Hognon Sogbossi

Jérôme Verdier

Stéphane Multon

Impact of reinforcement-concrete interfaces and cracking on gas transfer in concrete

Keywords: Reinforced concrete, durability, transfer, gas permeability, crack

The durability of reinforced concrete structures is largely impacted by their transfer properties, which can be evaluated through, for example, permeability measurement. Usually, concrete permeability is studied on plain specimens and the effect of the presence of steel bars on permeability in reinforced concrete has been little studied in the literature. The steel-concrete interface presents a larger porosity than plain concrete, which can be the cause of preferential percolation paths for fluids. Such percolation paths could create a lower resistance to fluid transfer and modify transfer kinetics. For reinforced and prestressed structures with large reinforcement contents, such as found in nuclear power plants, the impact of the reinforcement on gas transfer should be identified to obtain a better assessment of the flow within the structure. The aim of this experimental study is to characterize the effect of the presence of reinforcement on such flows by measuring leakage rates, permeability, and time to reach the steady state. Measurements were performed with a Cembureau constant head permeameter on cylindrical concrete specimens with or without steel bars. Since gas transfer into concrete depends on the rate of saturation of the material, the specimens were tested at different degrees of saturation: 0%, 6%, 30%, 60%, 80%, 90% and 100%. The analysis quantifies the impact of the defects created by the steel bar for each state. The results show that material composed of concrete and reinforcement can be divided into two distinct permeability zones: the plain concrete and the steel-concrete interface with or without cracking.

These two zones can be associated in series and/or in parallel according to the configuration. The consequences on permeability measurement in reinforced structures are discussed.

Introduction

The penetration of aggressive agents, water, chloride and other ionic species into concrete is responsible for most of its deterioration [START_REF] Vu | Contribution à l'étude de la corrosion par carbonatation du béton armé: Approche expérimentale et probabiliste[END_REF]- [START_REF] Basheer | Assessment of the durability of concrete from its permeation properties: a review[END_REF]. The viability of many structures depends on their concrete transport properties [START_REF] Ollivier | Propriétés physiques du béton et de ses constituants[END_REF]- [START_REF] Care | Determination of relevant parameters influencing gas permeability of mortars[END_REF]. The permeability of a reinforced concrete and the extent to which it permits diffusion are considered as major indicators of its durability [START_REF] Basheer | Assessment of the durability of concrete from its permeation properties: a review[END_REF], [START_REF] Abbas | Gas permeability of concrete in relation to its degree of saturation[END_REF], [START_REF] Hilsdorf | Performance Criteria for Concrete Durability[END_REF]. Fluid transport in a porous material is possible because of the presence of paths of connected porosity. In concrete, the pathways are mainly: the capillary pores of the cement paste [START_REF] Hilsdorf | Performance Criteria for Concrete Durability[END_REF]- [START_REF] Powers | Structure and Physical Properties of Hardened Portland Cement Paste[END_REF]; the interfacial transition zone between cement paste and aggregate [START_REF] Schutter | Report 38: Durability of Self-Compacting Concrete -State-of-the-Art Report of[END_REF], [START_REF] Maso | Interfacial Transition Zone in Concrete[END_REF]- [START_REF] Scrivener | The interfacial transition zone (ITZ) between cement paste and aggregate in concrete[END_REF]; and micro cracks in aggregates and cement matrix [START_REF] Schutter | Report 38: Durability of Self-Compacting Concrete -State-of-the-Art Report of[END_REF], [START_REF] Ismail | Etude des transferts et de leurs interactions avec la cicatrisation dans les fissures pour prolonger la durée de service des infrastructures (ponts, centrales nucléaires)[END_REF]. Most of the research on the subject has dealt with plain concrete and mortar without reinforcement, so the effect of the presence of steel bars on the permeability of reinforced concrete has been little studied. Reinforcements lead to obtain smaller cracks opening for concrete under mechanical loading and thus to decrease permeability in damaged concrete [START_REF] Desmettre | Contribution à l'étude de la perméabilité du béton armé sous sollicitations statiques et cycliques[END_REF]- [START_REF] Rizkalla | Air leakage characteristics in reinforced concrete[END_REF]. This impact of reinforcement has to be taken into account for leakage prediction in real structures [START_REF] Riva | Prediction of air and steam leak rate through cracked reinforced concrete panels[END_REF]. The inclusion of fibres decreases permeability properties in concrete with [START_REF] Hubert | Influence of fiber content and reinforcement ratio on the water permeability of reinforced concrete[END_REF], [START_REF] Rapoport | Permeability of Cracked Steel Fiber-Reinforced Concrete[END_REF] or without [START_REF] Singh | Permeability of Steel Fibre Reinforced Concrete Influence of Fibre Parameters[END_REF] cracks due to mechanical loading. Previous experimental works analysed the mechanical role of reinforcement on the permeability of loaded concrete. In this case, several mechanisms impact concrete permeability: the modification of porosity due to mechanical loading, the cracks occurrence and the impact of the steel-concrete interface. Small stresses lead to compaction and thus to the decrease of permeability [START_REF] Choinska | Effects and interactions of temperature and stress-level related damage on permeability of concrete[END_REF] and permeability increases when cracks connectivity occurs [START_REF] Choinska | Effects and interactions of temperature and stress-level related damage on permeability of concrete[END_REF], [START_REF] Picandet | Effect of axial compressive damage on gas permeability of ordinary and high-performance concrete[END_REF]. In reinforced concrete samples, steels densify the cracking and reduce the crack width due to loading. Reinforcement leads to a reduction of the flow through cracks and thus of the permeability.

However, reinforcement bars are also responsible for concrete cracking due to restrained shrinkage, even without external loading. The induced cracks and also the voids at the interface with the concrete [START_REF] Soylev | Quality of steel-concrete interface and corrosion of reinforcing steel[END_REF]- [START_REF] Mohammed | Chloride-Induced Corrosion of Steel Bars in Concrete with Presence of Gap at Steel-Concrete Interface[END_REF] disturb the transfers in concrete, particularly close to the skin, where transfer has a preponderant effect on durability. For reinforced concrete submitted to loading, the different mechanisms acting on permeability are concomitant. To obtain precise modelling, it is necessary to distinguish the part of each mechanism: the impacts of the mechanical loading, of the induced cracks and of the steel-concrete interface. As a consequence, transfers in plain and reinforced specimens without mechanical loading have to be analysed to assess the capacity of steel-concrete interfaces to provide gas transfer paths.

If the steel-concrete interfaces are actually preferential paths of transfer and become accessible to fluids from the surface through cracking, the reinforcement cover would become unable to assume its protective role against aggression and so the steel bars could be directly exposed. The degradation kinetics of reinforced concrete becomes greatly accelerated if other phenomena do not occur (healing, precipitation). Similarly, as these steel-concrete interfaces act on the kinetics of the fluid flow, they can change the time necessary to reach the steady state of flow due to their low resistance to transfer [START_REF] Verdier | Contribution à la caractérisation de l'évolution du taux de fuite des enceintes de confinement du parc nucléaire[END_REF], according to the design of the reinforcement in the structure. In heavily reinforced structures, the steel-concrete interfaces are numerous, have considerable area and are highly connected. Therefore, they form significant pathways for transfers, which should be considered when predicting the durability, and particularly the air tightness of such structures. This study analyses the contribution of steel-concrete interfaces to gas transfer within reinforced concrete.

The degree of saturation of concrete on site is usually very high close to water supply and in locations submitted to rainfall and is usually over 80% at 50 mm depth [START_REF] Stark | The moisture condition of field concrete exhibiting alkali-silica reactivity[END_REF], which prevents most of the transfer in plain concrete. However, the Kelvin Laplace equation indicates that cracks with an opening greater than one micrometre are drained even at high relative humidity (99.99%). So, in the presence of skin cracking, the steel-concrete interface can easily be drained even if the saturation level of the rest of the concrete is high. Since the permeability of concrete is affected by its water saturation [START_REF] Abbas | Gas permeability of concrete in relation to its degree of saturation[END_REF], [START_REF] -A. Kameche | La perméabilité relative comme indicateur de durabilité: Influence de l'état hydrique du béton et de la taille des éprouvettes[END_REF]- [START_REF] Monlouis-Bonnaire | Prediction of the relative permeability to gas flow of cement-based materials[END_REF], it is important to perform this study on material at different states of water saturation.

Objectives

The objective of this paper is to analyse the impact of the steel-concrete interfaces on reinforced concrete permeability, by inducing pathways for gas transport into concrete. They can change the transfer kinetics and the time to reach steady state during a measurement of gas leak rate and can thus constitute weak zones regarding the air tightness of reinforced concrete structures. Three specific points are particularly highlighted:

-Impact of the steel-concrete interface on permeability, -Impact of the steel-concrete interface on flow kinetics, -Impact of induced cracking close to the steel-concrete interface on permeability.

The first two points will lead us to identify the different zones of permeability in reinforced concrete, including the steel-concrete interface and induced cracking. The third point concerns an analysis of the impact of the crack opening on the transfer. To obtain a more relevant identification and characterization of the variation of permeability with the length of the steel-concrete interfaces in site conditions, all three studies were performed for various states of saturation.

Theoretical background

Permeability is defined as the ability of a material to allow fluids to pass through it under a pressure gradient. This property governs the flow rate of a fluid through a porous medium. The coefficient of permeability 𝑘 𝑎 is defined by Darcy's law.

For the sake of simplicity, the "coefficient of permeability" is referred to simply as "permeability" in this article unless otherwise noted. The gas permeability of a porous solid is calculated using the Hagen-Poiseuille relationship for laminar flow of a compressible fluid through a porous medium with small capillaries under steady-state conditions. The relationship solved for the apparent permeability 𝑘 𝑎 can be written as in Eq. 1 [START_REF] Kollek | The determination of the permeability of concrete to oxygen by the Cembureau method-a recommendation[END_REF].

𝑘 𝑎 = 2 𝜇 𝐿 𝑄 𝑂 𝑆 𝑃 𝑂 𝑃 𝐼 2 -𝑃 𝑂 2 (Eq. 1)
where 𝑄 𝑂 is the volume flow rate of the fluid (m 3 /s), S is the cross-sectional area of the specimen (m 2 ), L is the thickness of the specimen in the direction of flow (m), μ is the dynamic viscosity of the fluid at the test temperature (Pa.s), PI is the absolute inlet pressure (Pa), and PO is the outlet pressure (the pressure at which the volume flow rate is determined, assumed in this test to be equal to atmospheric pressure -N m -2 ).

For dried air at a temperature of 20°C, the dynamic viscosity μ may be taken as 1.83e -5 Pa.s.

Materials and methodology

Experimental setup

The permeability of porous materials can be evaluated through a gas flow measurement using a permeameter with constant head (the difference in pressure is fixed during the measurement) or variable head. In this study, a constant head permeameter was used. The apparatus is known as a Cembureau permeameter. The permeating medium was dried air. Fig. 1 gives an overview of the apparatus. The main elements are: an air supply cylinder fitted with a pressure reducing valve, a precision pressure regulator, a pressure gauge, the permeability cell, a flow meter and a computer to record the air flow.

In order to reach a precision of 1% in the determination of permeability, Kollek's specifications [START_REF] Kollek | The determination of the permeability of concrete to oxygen by the Cembureau method-a recommendation[END_REF] were followed: the inlet pressure, PI, to the cell was controlled over a range of absolute pressure from 2 to 5 bars (2 x 10 5 to 5x10 5 N.m -2 ) by the pressure regulator and the set pressure level was maintained within 1% of the selected pressure during the whole time of air flow measurement. The graduations on the pressure gauge were 5 x 10 -2 bars (5 x 10 3 N.m -2 ). The permeability cells were to the flow range: the first one for flows lying between 0 and 10 cm 3 /min and the second one for flow between 10 and 100 cm 3 /min. After initiating the percolation of dried air through the specimen at a given applied pressure, sufficient time was allowed for steady state flow to become established.

The steady state condition was verified with the curves of air flow versus time. In this study, the time to reach steady state (TRSS) was short due to the transfer thickness (50 mm) [START_REF] Verdier | Modelling of a gas flow measurement: Application to nuclear containment vessels[END_REF]. The measurement allowed the TRSS to be compared among test configurations (comparison of the impact of steel bar length in concrete on TRSS) by direct comparison of the downstream flow. After having measured the flow in the steady state, the permeability ka was calculated from the Hagen-Poiseuille equation for laminar flow of a compressible fluid through a porous body under steady state conditions (Eq. 1).

Experimental program

Different configurations can be used to measure the air flow through reinforced concrete specimens.

The transfer into the accessible pores and/or into cracks of the material can be analysed with the specimen configuration illustrated in Fig. 2. In this arrangement, the concrete around the reinforcement and/or the crack openings directly governs the measured air flow and the contribution of the steel-concrete interface to the outlet flow, QO, cannot be isolated. The lengths of the reinforced bars in the samples were chosen in accordance to the concrete aggregate size (16 mm). The impact of reinforcement on permeability was studied for different degrees of saturation: 0%, 6%, 30%, 60%, 80%, 90% and 100%. The degree of saturation is indicated at the beginning of the specimen reference when necessary (Fig. 4).

Samples

To limit causes of scatter, all the samples were extracted from four cylindrical specimens with a diameter, ∅, of 150 mm and height, h, of 200 mm: one specimen for the three plain samples (SrP/1, SrP/2, SrP/3) and three specimens for the reinforced concrete samples (SrR2/i, SrR3/i, SrR5/i) as shown in Fig. 5. All measurements were performed on three (3) samples of each type. Concrete mix is given in Table 1. Siliceous limestone aggregates were used. Silica contents of aggregates were about 80 and 5% for the sand and the gravels, respectively. Specimens (ϕ=150 mm, h= 200 mm) were cast in plastic moulds. Twenty-four hours after casting, they were removed from their moulds and cured in lime water at a temperature of 20 ± 2 °C for at least 60 days. This long time (60 days) in water was required to obtain a stabilized material regarding cement hydration [START_REF] Waller | Relations entre composition des betons, exothermie en cours de prise et resistance en compression[END_REF].

Lime water allows an increase of the pH and a limitation of carbonation and calcium leaching [START_REF] Makhloufi | The strength of limestone mortars with quaternary binders: Leaching effect by demineralized water[END_REF], [START_REF] Ramezanianpour | Practical evaluation of relationship between concrete resistivity, water penetration, rapid chloride penetration and compressive strength[END_REF]. After curing, the samples (ϕ=150 mm, h=50 mm) were sawn from the original specimens and the first 25 mm of both sides were removed to avoid skin effects (Fig. 5). The samples were then The preconditioning of the samples is described in Table 2. The specimens of concrete were dried at four temperatures to reach the different degrees of saturation (Sr). They were first dried in an oven at 40°C to achieve Sr equal to 80%, then at 50°C to reach Sr of 60%, then at 60°C to reach 30%, and again at 60°C to achieve the smallest saturation for this temperature (considered to have been obtained when constant mass was reached, with a mass loss lower than 0.05% in 24 hours).

These three temperatures were used to decrease the risk of inducing thermal cracking associated with drying at 105°C. If 105°C is considered as the reference temperature at which the degree of saturation is assumed to reach zero, the specimen "dried" at 60°C actually contained an amount of water corresponding an Sr of 6%. The saturation degree of 6% was studied to obtain the permeability at the lowest saturation degree and to minimize the impact of thermal damage. Finally, to achieve a fully dry state, samples were dried in an oven at 105°C until constant mass was reached (less than 0.1% change in mass in 24 hours). At each drying state, the samples were wrapped in aluminium foil and put into the oven to allow the moisture to spread evenly in the material. The duration of homogenization was at least equal to the drying time and the temperature was the same as during drying. The permeability test was performed after each drying stage. This preconditioning to ensure an identical material before and after drying was inspired by the literature [START_REF] Carcassès | An optimised preconditioning procedure for gas permeability measurement[END_REF], [START_REF] Antón | An improved procedure for obtaining and maintaining well characterized partial water saturation states on concrete samples to be used for mass transport tests[END_REF], [START_REF] Rilem Tc 116-Pcd | Permeability of concrete as a criterion of its durability, final report[END_REF]. For saturation at 90% and 100%, no oven drying was required. For the degree of saturation of 100%, permeability tests were performed directly at the end of the curing period in lime water. For 90%, samples were simply left in the test room at 20°C for 20 hours. The specimens were weighed before and after the permeability measurements. No variations were noted. Global degree of saturation was constant during the permeability measurement.

Concrete properties

Tables 2 presents the porosity of samples according to the configuration. The porosity accessible to water of each type of specimen and the apparent density of plain concrete are noted with the standard deviation. This porosity was determined according to the AFPC-AFREM method [START_REF] Ollivier | Durabilité des bétons, méthodes recommandées pour la mesure des grandeurs associées à la durabilité compte rendu des journées techniques AFPC-AFREM[END_REF] on the complete sample including the steel bar.

The steel bars used were ribbed bars 14 mm in diameter. The ribbing of the steel surface was expected to increase adherence and reduce the voids along the steel-concrete interface. As shown in Table 2, the porosity was rather high and of the same order of magnitude for all the specimens. The presence of different volumes of steel within the samples could have changed the porosity. As steel bars are non-porous, with a good quality steel-concrete interface, the transition from P to R2 and R5 could have led to a decrease of porosity. Conversely, a poor quality steelconcrete interface could have led to increases in porosity between P and R5. In this study, no significant differences were observed and no conclusions can be drawn with respect to the interface quality.

Results

Reproducibility of the curves of air flow

The steel-concrete interfaces and cracking resulting from restrained shrinkage around the reinforcement can be the origin of heterogeneities in reinforced concrete, which lead to differences in TRSS, so it was important to verify the reproducibility of flow measurements in the presence of reinforcement. For this purpose, each test was performed three times on one sample of each of the four configurations under study (Fig. 4). The results presented here were obtained on the samples in the driest state: 0P1, 0R2/2, 0R3/2 and 0R5/3. The samples were taken at random. Two reproducibility tests were performed: one related to measurements, starting from the same face, and one related to the impact of the choice of measurement face. The presence or absence of the steel bar on the face exposed to inlet pressure could have an impact on the measurement. The curves of air flow versus time Q(t) are shown in Fig. 6.

P1 R2/2A R2/2B R3/3A R3/3B R5/3A R5/3B
In all cases, the standard deviation for three measurements on the same sample was very low (less than 1% -Table 4) and the measurement was reproducible with the presence of steel bars. The volume flow rate and flow kinetics were the same whatever the face exposed to the inlet absolute pressure (Fig. 6), even for asymmetrically reinforced samples (cases of R2 and R3 in which the steel does not cross the sample completely). In the rest of the paper, no distinction will be made between the faces subjected to the inlet pressure. The results presented here for one sample of each type are representative of all the samples, even those made of reinforced concrete. Differences in amplitude could be obtained among samples in the same configuration due to the heterogeneity created at the interface by the reinforcement. It is important to note that all the curves of air flow obtained on the reinforced samples can be divided into two parts (Fig. 6):

-an initial abrupt increase in flow. This jump is greater when the length of steel in the sample is greater (R5 and R3),

-followed by the usual kinetics of fluid flow through plain concrete.

The plain samples showed no abrupt increase at the beginning but only the usual kinetics, as expected.

The initial flow jump was due to the steel-concrete interface, which represented a defect regarding the transfer of gas into reinforced concrete (discussion in section 5.3). It is important to mention that this jump is not the same as the flow peak presented by Verdier and al. [START_REF] Verdier | Modelling of a gas flow measurement: Application to nuclear containment vessels[END_REF], which corresponds to a measurement artefact due to the initiation of the inlet pressure and can be explained by the evacuation of an outlet overpressure when inlet pressure is applied. To eliminate this parasite, the pressure was always evacuated at the beginning of measurement by opening the valves at the outlet of the permeability cell. Based on Verdier and al.'s work [START_REF] Verdier | Modelling of a gas flow measurement: Application to nuclear containment vessels[END_REF] and on the measurements performed in the present work, fifteen seconds after application of the inlet pressure was enough to evacuate this overpressure. The initial time (zero date) of the air flow measurement was taken from the moment when this overpressure was evacuated.

The experimental results presented in Fig. 6 are in contrast with the measurements of porosity, which did not show any significant differences (Table 3). The difference was due to a preferential pathway of gas transport into reinforced samples that was not sufficiently significant to show an impact on porosity but was revealed by flow measurements. This shows the good sensitivity of such measurements for detecting small defects that can impact the concrete durability without significant consequences on other properties. The highest permeability of the reinforced specimens (Fig. 7) could be explained by the highest pore connectivity with the creation of preferential paths of gas transfer into the concrete near the reinforcement or the steel-concrete interface. In the case of R5, the path could be totally constituted by the steel-concrete interface, which opened out. In the case of R2 and R3, the presence of the steel bar could be the cause of cracking induced by drying in the concrete part under the steel bars. Such cracks were connected to the steel-concrete interface and could form a path between the two faces of the sample. The consequence was an increase in the air flow. The aggregate size had probably an impact on the connectivity of the pore network under the steel bars. Permeability measurement on samples with concrete thickness larger than 30 mm under the steel bar could exhibit a decrease of the initial flow jump.

Impact of steel-concrete interface on permeability

The permeability of samples was calculated from the flow rates in the steady state (Eq. 1). Fig. 7 shows the evolution of apparent and relative permeability as a function of saturation. The inlet pressure was 2 bars. The results presented were similar at all test pressures (2, 3 and 4 bars).

As usual, the relative permeability was obtained from the ratio of the permeability at a given state of saturation and the permeability at saturation state Sr = 6%: ka,rel = ka,Sr/ka,Sr = 6%. The state Sr = 0% (drying of the material at 105°C) was not kept as the reference in order to limit the impact of Whatever the state of saturation, the permeability of plain concrete samples P was always the lowest (Fig. 7). The presence of reinforcement led to significantly increase the permeability of samples.

The permeability of reinforced samples R5 (reinforcement crossing the sample) were the highest, while the values of permeability obtained for R2 and R3 (steel not completely crossing the sample)

were intermediate. The zones with high permeability (preferential paths of gas transfer into the concrete near the reinforcement or steel-concrete interfaces) were more noticeable at high saturation. The presence of water in pores makes difficult the transfer of air in concrete. Air flow decreases with the increase of concrete saturation [START_REF] Abbas | Gas permeability of concrete in relation to its degree of saturation[END_REF], [START_REF] Monlouis-Bonnaire | Prediction of the relative permeability to gas flow of cement-based materials[END_REF], [START_REF] Kameche | Assessment of liquid water and gas permeabilities of partially saturated ordinary concrete[END_REF], [START_REF] Villain | Mesure de la perméabilité aux gaz en fonction du taux de saturation des bétons[END_REF]. This phenomenon depends on the geometry of the percolation path. Path with an opening greater than one micrometre can be drained even at high relative humidity (99.99%). Thus, path formed by steel-concrete interface can be drained more easily than usual concrete porosity. For Sr lying between 60% and 80%, all three reference samples P were impermeable to air (low or zero permeability as obtained by many researchers [START_REF] Abbas | Gas permeability of concrete in relation to its degree of saturation[END_REF], [START_REF] Monlouis-Bonnaire | Prediction of the relative permeability to gas flow of cement-based materials[END_REF], [START_REF] Kameche | Assessment of liquid water and gas permeabilities of partially saturated ordinary concrete[END_REF]) while all reinforced samples (R2, R3 and R5) were permeable (Fig. 7-b).

This means that the pathway formed by the interface and the cracks was larger and more connected than the usual concrete pores. Consequently, they were desaturated even with the drying at 40°C, while the rest of concrete was still in a high saturation state that did not allow gas transfer. At high levels of saturation, such pathways had a greater impact on the gas transfer into the material.

Concerning the impact of the reinforcement, it is important to note the high standard deviation that can be seen in the case of the reinforced samples completely crossed by steel bars while plain concrete samples show little scatter (Fig. 7-a). This highlights the impact of the defect on flow paths.

These large standard deviations of the permeability of reinforced samples can be explained by the heterogeneous nature of the steel-concrete interface [START_REF] Makhloufi | The strength of limestone mortars with quaternary binders: Leaching effect by demineralized water[END_REF], which can vary greatly from one sample to another according to casting (vibration), drying, and difference in verticality of the steels in the concrete during casting.

In summary, the analysis of the results presented in Fig. 7 leads us to break the downstream air flow (from which the apparent permeability is calculated) down into two distinct contributions: one zone of high permeability due to the "defect" caused by the presence of the steel/concrete interface and induced cracking, and one zone of plain concrete. In all cases, the defect is located in the vicinity of the steel. The impact is characterized by an initial jump in the measured air flow and leads to an increase of the permeability of reinforced samples.

Impact of steel-concrete interface on air flow and on flow kinetics

Air flow, Time to Reach Steady State (TRSS) and different permeability zones

The analysis of the kinetics of air flow is necessary to identify and quantify the impact of the presence of reinforcement on gas transfer. Fig. 8 shows the flow kinetics according to the degree of saturation Sr = 80%, 60%, 30% and 6% for one sample of each type (SrP1, SrR2/2, SrR3/3 and SrR5/2). The absolute pressure of the test was 2 bars. At Sr = 80%, no flow was measured through the reference samples, as illustrated by 80P1 in Fig. 8, while flows appeared through all the reinforced samples for this same saturation degree. For reinforced samples, the flow was almost immediate and constant. The flow rates observed through reinforced samples were due to highpermeability zones since plain concrete is not permeable at this saturation degree (Sr = 80%). This zone is called a "defect" in the following.

It is very interesting to observe that the flow through reinforced samples reached steady state almost instantaneously after application of the inlet pressure: the TRSS was less than 1 minute. This short time is representative of a medium with very low resistance to the flow (for example, concrete with serious damage, because the defects oppose little resistance to transfer). The poor adhesion between the concrete and the steel bar, and cracks in the concrete near the steel bar led to very low resistance to gas transfer and a flow rate proportional to the defect. If the adhesion was perfect, flow rates of all reinforced concrete would be zero. The presence of this defect can also be expected to modify the concrete transfer properties around the reinforcement during drying. The concrete located in the vicinity of the defect is preferentially drained by its connection to the defect.

At Sr = 60%, very low air flow was measured in the reference samples (Fig. 8). The flow was smaller than any of the flows through reinforced samples. Initial abrupt increases in the flow were observed for all the reinforced samples (R2, R3 and R5). The jumps were observed 15 seconds after the start of measurement while the flow through the plain concrete was zero. Unlike the previous state (Sr = 80%), the steady state took longer to become established in reinforced samples at Sr = 60%. The times to reach steady state of reinforced samples increased from 1 minute to 40 minutes when Sr changed from 80% to 60%. At Sr = 80%, the TRSS was very small because it was due to transfer in the defect only (which is very fast) since transfer in concrete was still zero. But at Sr = 60%, the TRSS was relatively long for the plain sample (more than 40 min), because the connectivity of the concrete percolating network was reduced by the presence of water and its tortuosity was increased.

Local pressure variations can be more difficult to clear out and impact TRSS. In reinforced samples, the contribution of the concrete could be measured after the initial jump [START_REF] Schutter | Report 38: Durability of Self-Compacting Concrete -State-of-the-Art Report of[END_REF] and the TRSS increased due to the slow transfer in concrete as in the plain sample. Nevertheless, it was still the defect that mainly controlled the gas transfer into the material at Sr = 60%. At Sr = 30% and 6%, the pores of the concrete were almost free of water, the air molecules thus encountered less resistance to their movement in the concrete pores and the TRSS decreased compared to the state Sr = 60% . However, although the TRSS of the reinforced samples for Sr lower than 30% were lower than the TRSS for Sr = 60%, they remained higher than the TRSS for Sr > 80%. In this case, water was not the only factor responsible for the resistance to flow in pores; pore tortuosity and connectivity also had a greater impact.

The variation of the air flow rate with the saturation degree for the reference sample P (in blue) was as usual for such measurements [START_REF] Verdier | Modelling of a gas flow measurement: Application to nuclear containment vessels[END_REF]. For reinforced samples, the concrete contribution was apparent after the first jump. Concerning the first jump, the longer the interface was (from R2 to R5), the greater was the jump. This was verified for all degrees of saturation, thus confirming the importance of the steel/concrete interface for air flow in reinforced concrete. Permeability tests performed on concrete thicknesses less than twice the maximum size of the aggregate could be impacted by the contribution of the interfacial transition zone (ITZaggregates-mortar interfaces) to transfer. The 20 or 30 mm of concrete under the reinforcement (R2 and R3 samples) did not create the same resistance to transfer as in the case of plain samples; it participated in the flow associated with the defect. The residual thickness of concrete under the reinforcement did not provide a representative volume in terms of permeability measurement. The consequence could be a preferential path linking steel/concrete interfaces and interfacial transition zones of aggregate in the concrete under the reinforcement, which would amplify the impact of the defect. However, this thickness was of the same order as that of the concrete cover in many real structures.

Concrete contribution to air flow kinetics

To analyse the contribution of concrete to the air flow through reinforced samples, the air flow corresponding to the contribution of the interface and cracks (referenced Q1) was subtracted from the curve. In order to determine the flow Q1, the plain concrete curves were first subtracted from the reinforced concrete curves. As shown in Fig. 9, the result of the subtraction, Q1, was quite constant after 30 seconds of measurement. Constant flows Q1 were subtracted from the curves of reinforced samples for the samples at saturation degrees lying between 0 and 30% (Fig. 10). For the high saturation degrees (60% and 80%), the contribution of the plain concrete was low or negligible and the representation was not useful.

Fig. 10: Correction of curves for all samples for Sr = 0%, 6% and 30%

After the subtraction of the initial jump, all the air flows had the same kinetics (Fig. 10). The corrected curves are representative of the contribution of the sound concrete to transfer whatever the depth of reinforcement. This confirms that the beginning of the curve of air flow Q(t) is highly representative of the defect due to the interface and induced cracks. The slight differences observed in flow kinetics after subtraction (Fig. 10) may be due to the heterogeneity of the samples, which can be high since cracks are involved in air flow through reinforced samples. In presence of reinforcement, two mechanisms act on transfer in concrete: the air flow in the interface and induced cracks, and the usual air flow in sound concrete. The transfer in the plain concrete does not appear to be greatly affected. Modelling has to consider the two phenomena in order to be representative of concrete in real structures.

Discussion

The different permeability zones in reinforced concrete are schematized in Fig. 11. In the case of R5, the interface crosses the whole sample and links the two sample faces. It can provide a transfer pathway according to the nature of the steel/concrete interface (Fig. 11-a). For R2 and R3, the interface does not link the two faces directly (Fig. 11-b) but the previous analysis has pointed out that it can also lead to a preferential pathway between the two faces since abrupt increases in air flow were observed in all reinforced R2 and R3 samples (Fig. 8). The variation of the effect of reinforcement according to the degree of saturation can be quantified in terms of permeability (Fig. 7), in terms of relative air flows compared to the total flow QO (Fig. 12) or in terms of equivalent crack opening (Fig. 14). The definition of the relative air flows in Fig.

12 is:

-Q1/QO, ratio between the flow due to the presence of the interface and the total air flow into the sample, -Q2/QO, ratio between the flow through the concrete and the total air flow into the sample (Fig. 12).

Fig. 12:

Relative air flows in reinforced samples according to saturation degree

In terms of relative permeability, the impact of reinforcement was the greatest for degrees of saturation lying between 60 and 80% (Fig. 7-b). The comparison of the flows Q1 and Q2 confirms this result (Fig. 12): the contribution of the defect to transfer is all the more important when the saturation level is high.

These observations can be analysed in three points:

-For saturated samples (Sr equal to 100%), the whole concrete porosity and steel-concrete interfaces are filled by water and samples are totally impermeable to gas, -At high degrees of saturation (Sr equal to 60% and 80% in the experiments), the permeability of plain concrete is still zero (Fig. 7), which is not the case for reinforced samples. This means that steel-concrete adherence is not perfect and impacts gas transfer because of its direct connection with the surface in the case of R5. In the case of the samples R2 and R3, it indicates that there is not only the pathway created by steel-concrete interfaces but also a continuity of the defect in the concrete below the steel (Fig. 11-b), which can be induced by the presence of cracks and by pathways through interfacial transition zones of aggregates. In high states of saturation, the steel-concrete interfaces and induced cracks are thus the main transfer vector in reinforced samples (Fig. 12). This result has an implication for the durability of structures:

the concrete in situ is generally subjected to high levels of water saturation [START_REF] Laurencet | Fissuration, étanchéité et durabilité des structures en beton armé[END_REF], and the percentage of transfer through concrete skin by cracks could be particularly high compared to transfer through concrete (Fig. 12). It could be the main mechanism to be considered for transfer through the concrete skins of structures. -At low degrees of saturation, the pores of the concrete surrounding the reinforcement are gradually emptied of water, which increases the contribution of concrete to the air flow (Fig. 12). Moreover, the impact of concrete shrinkage on transfer is amplified. The shrinkage induced by drying is restrained by the rigid inclusion of the steel bar in the reinforced samples, where it leads to tensile stresses in the concrete and to cracks. Consequently the pores can be connected to the cracks and to the steel-concrete interface, the consequence being an increase in gas transfer. These cracks were already present in reinforced samples for saturation degrees between 60% and 80%. At low saturation degrees, shrinkage strains are greater and the induced cracks grow, thus possibly increasing the contribution of the defect to the air flow.

However, the relative contribution of a defect decreases with decreasing degree of saturation (Fig. 12): for a low saturation state, the proportion of transfer in the concrete increases faster than the contribution of the defect, except for a saturation degree equal to 0, for which the contribution of the defect increases suddenly, probably because the high drying temperature (105°C) between 6 and 0% leads to associated damage.

These phenomena contributed to the greater relative permeability of reinforced samples (Fig. 7).

In order to complete this analysis, samples were observed with a video microscope (Keyence VH-5911, maximum magnification x 175). Fig. 13 shows a microscopic view of the steel-concrete interface of the sample R5/1 (magnifications x 25 for Fig. 13-a and x 175 for b). As could be expected, the geometry of the interface was very complex. The microscopic observation indicated the presence of some irregular voids in the contact between concrete and steel. The voids did not cross the sample but were localized (Fig. 13-b) as already observed by Mohammed and al. [START_REF] Mohammed | Marine Durability of 15-Year Old Concrete Specimens Made with Ordinary Portland, Slag,and Fly Ash Cements[END_REF]. With the precision of the apparatus used here, no detachment appeared anywhere around the reinforcement (Fig. 13-a). However, detachments with openings smaller than 10 μm may exist.

They would not be observable with this video microscope. The specimens would have to be sawn for more precise apparatus to be used. This was not done since it could lead to the interface being modified.

To quantify the opening necessary to obtain the measured permeability, equivalent crack openings were calculated from flows. For this purpose, the defect caused by the interface and the induced cracking was modelled as a single perfect crack with an equivalent crack opening, w, completely surrounding the steel bar. This opening was determined from the air flow Q1, which characterizes the impact of the defect on the permeability. Different works propose a determination of the crack opening 𝑤 from air flow [START_REF] Greiner | Air leakage characteristics in cracked concrete[END_REF], [START_REF] Rizkalla | Air leakage characteristics in reinforced concrete[END_REF], [START_REF] Suzuki | Leakage of gas through concrete cracks[END_REF]. The equation below ( 2) is drawn from Mivelaz's work [START_REF] Mivelaz | Etanchéité des structures en béton arme. Fuites au travers d'un élément fissuré[END_REF]:

𝑤 3 = 24 𝜇 𝐿 𝑅 𝑇𝑄 1 𝜉 (𝑃 𝐼 2 -𝑃 𝑂 2 ) (Eq. 2)
where μ is the dynamic viscosity of the fluid at the test temperature (Pa.s), PI the inlet pressure (absolute) (Pa), PO the outlet pressure -assumed to be equal to the atmospheric pressure (Pa) in this test, R the gas constant (J/kg/K), T the temperature (K) and ξ a flow coefficient that essentially characterizes the network tortuosity.

During the test, the evolution of the flow is characteristic of the presence of different defects. To quantify the impact of these defects on permeability, the tortuosity, the connectivity, the constrictivity of the pore network, and the interactions between cracks and concrete porosity should be taken into account. The importance of each parameter for permeability depends on the geometry of the actual percolation path which is difficult to characterize. However, the measured flow highlights the range of the impact and allows a simplified evaluation. This calculation assumes constant thickness for the defect. In order to quantify the approximation of this approach, the calculation is performed for two extreme values of the flow coefficient ξ. Thus, the impact of the geometry of the percolation path on permeability is evaluated.

This approach was chosen because it took only a few parameters (𝑤 and 𝜉) into account in comparison with others. According to Ripphaussen [START_REF] Ripphausen | Untersuchungen zur Wasserdurchlässigkeit und Sanierung von Stahlbetonbauteilen mit Trennrissen[END_REF], cited by Mivelaz [START_REF] Mivelaz | Etanchéité des structures en béton arme. Fuites au travers d'un élément fissuré[END_REF], the flow coefficient, ξ, is defined as the ratio of flow through cracks with an opening of w and the theoretical flow through two smooth parallel planes having the same opening, 𝑤 . ξ is then less than 1 and takes the roughness and the tortuosity of the transfer path into account. The equivalent crack of width w is assumed to be all around the reinforcement over the entire sample thickness. Its length is equal to the thickness of the samples (L). The flow coefficient, ξ, is assumed to be constant while, in reality, the crack network is modified by drying and the coefficient could increase for the lowest saturation degree.

The calculated opening is approximate and does not represent reality but it enables the impact of the opening due to steel-concrete interfaces on the concrete permeability to be analysed and compared. The defect openings thus calculated are presented in Fig. 14 for a relative inlet pressure of 1 bar and for two extreme assumptions of flow coefficient, ξ:

-A flow coefficient, ξ, of 1, which represents direct transfer [START_REF] Mivelaz | Etanchéité des structures en béton arme. Fuites au travers d'un élément fissuré[END_REF],

-A flow coefficient, ξ, of 0.08, which represents usual transfer in a diffusive cracking pattern in concrete [START_REF] Mivelaz | Etanchéité des structures en béton arme. Fuites au travers d'un élément fissuré[END_REF], [START_REF] Buss | Proof of Leakage Rate of a Concrete Reactor Building[END_REF].

The mean values and standard deviations presented in Fig. 14 were obtained from the values for all samples tested (except SrR2/3 as explained above). Between 0 and 80% of saturation, two slopes can be distinguished in the variation of the defect opening 𝑤:

-A fairly constant evolution between Sr = 80% and 6%

-A marked change of gradient for the last drying between Sr = 6% and 0%.

This change for the lowest saturation degree could be due to notable damage occurring in the concrete during the drying at 105 °C. The increase of the calculated opening w presented in Fig. 14 globally quantifies the increase of transfer properties of the defect with drying. In reality, it may be partially due to the increase of the opening but it is probably also due to the movement of water out of the cracks and to the increase in crack connectivity, all of which all make transfer easier in the samples.

All the calculated values of opening 𝑤 are close and lie below 7 µm whatever the assumptions on the flow coefficient, ξ (Fig. 14). Unlike the localized voids observed under the microscope (Fig. 13), which did not cross the samples, the calculated detachments had to cross the samples to obtain the flows measured during permeability tests. No measurement was performed between 100% and 80% with the same preconditioning of samples. As defects with openings greater than 1 µm are drained at very high relative humidity (up to 99%, Kelvin Laplace equation), the air transfer in interfaces (and in cracks) could be expected to be between 80% and 99% for such openings. In reality, it depends on the morphology of the pathways. If there are only pathways with large openings (greater than 1 µm), a sample should be permeable even at very high degrees of saturation (higher than 95%) but, if the defect is composed of several pathways with smaller openings (less than 1 µm), it can become airtight for lower degrees of saturation. Consequently, to complete the evaluation of the pathways in the different samples, another degree of saturation was studied. For this purpose, samples were initially saturated with water under vacuum and then stored in an air-controlled test room (RH of 60% and temperature of 20°C) for only one day. The objective of this additional preconditioning was to drain only the defects, such as the steel/concrete interface, but to keep the percolating network of the concrete full of water. In these conditions, the concrete sample was still wet even if its surface was slightly dry. The global saturation rate of these samples is about 90% after this preconditioning. The permeability test was then performed and showed that:

-the air flow through plain samples was still zero, -the air flows through reinforced samples R2 and R3 were zero, and the equivalent opening 𝑤 was thus zero for this saturation degree (Fig. 14),

-the air flow through reinforced concrete R5 was not zero and the equivalent crack opening calculated was equal to the opening obtained for 80% (Fig. 14).

Results on R2 and R3 indicate that the defects that crossed the samples at 80% no longer formed a pathway for air flow at larger saturation degrees: the concrete below the steel bar (thickness: 20 mm for R3 and 30 mm for R2) was not permeable to gas at 90% saturation and so resisted gas transfer into the material. Results on R5 show that, apart from localized voids, there was actually a connected interface between the steel bar and the concrete, which crossed the entire thickness of the samples.

Its equivalent opening was effectively smaller than 5 µm and could not be seen in the microscopic analysis (Fig. 13).

The impact of reinforcement bars on permeability studied in this work should be dependent on numerous parameters (concrete composition, steel bars diameter, confinement pressure…).

Concerning concrete composition, aggregate size and composition should impact the effect as it modifies the ITZ porosity [START_REF] Elsharief | Influence of aggregate size , water cement ratio and age on the microstructure of the interfacial transition zone[END_REF]- [START_REF] Makani | Time-dependent behaviour of high performance concrete: influence of coarse aggregate characteristics[END_REF]. Decreasing the aggregate size could lead to increase the tortuosity in the percolation paths due to ITZ and thus to decrease the connection between the external environment and steel bars. The impact of steel bars on permeability could be lower for concrete with smaller aggregate. The impact of steel bar diameters would be dependent on steel / concrete ratio. For a same volume of concrete, the volume of voids at the interface should be lower for bars with smaller diameter. It should lead to smaller modification of permeability. At the opposite, for a same steel / concrete ratio, using smaller bars would lead to increase the number of bars. Each bar should create percolation paths. It should lead to increase the global permeability.

Future works should quantify precisely this effect. The confinement pressure applied to the specimen can also modify the results. In this program, six pressures lying between 3 and 9 bars were used for R5 sample (reinforcement crossing the sample) at the lowest saturation degree. As expected, no modification of the permeability was noted for plain samples. Such confinement pressures are too low to imply the reduction of the porosity. For reinforced samples, a decrease of the flow were observed for increasing pressure as the pressure leads to the closure of the interface (decrease of 6% of the permeability for pressure increasing from 3 to 9 bars). In case of damaged concrete, the application of confining pressure can decrease the opening of the existing cracks but the relative displacements of cracks lips prevent total reclosure. Decrease of flow can be expected as long as the confinement pressure does not lead to supplementary cracking.

The results presented in this paper cannot be directly extended to water permeability. Indeed, movements of water in such interfaces would lead to the combination with numerous chemical mechanisms: additional hydration of cement, precipitation of new phases, and steel corrosion according to water composition and pressure [START_REF] Ranaivomanana | Prediction of relative permeabilities and water vapor diffusion reduction factor for cement-based materials[END_REF]. The objective of the study was to decrease such risk of interaction and future works should analyse the impact of combination between potential cicatrisation in case of water transfer.

The high flow rate observed through the defects and the increase in permeability with reinforcement emphasized the great connectivity of the pores and steel/concrete interfaces in the reinforced samples. In literature, Singh and Singhal showed the decrease of permeability with the inclusion of steel fibres in concrete for unloaded concrete [START_REF] Singh | Permeability of Steel Fibre Reinforced Concrete Influence of Fibre Parameters[END_REF]. For fibres reinforced concrete, the percolation path induced by the steel fibres is discontinuous and the cracks which could be induced by restrained shrinkage would be smaller than in plain concrete. Such small cracks would have little impact on permeability [START_REF] Hubert | Influence of fiber content and reinforcement ratio on the water permeability of reinforced concrete[END_REF], [START_REF] Rapoport | Permeability of Cracked Steel Fiber-Reinforced Concrete[END_REF]. At the opposite, the presence of usual steel reinforcement in concrete induces continuous and larger percolations paths. Such continuous paths can largely impact permeability as shown in the present study. In conclusion, small continuous defects in concrete, such as steel/concrete interfaces and small concrete skin cracks can lead to permeability twice that expected for the plain samples usually used for permeability measurements. This illustrates and quantifies the risk associated with the use of measurements on plain concrete to evaluate and predict the transfer behaviour of real structures. Modelling based on permeability obtained on plain samples should take the impact of cracks and interfaces into account to obtain more relevant calculations, particularly close to the concrete skin. The experimental programme presented in this paper can thus be used to evaluate the scatter on concrete permeability due to the presence of reinforcement.

Summary

Permeability characterizes the ability of materials to resist the penetration of aggressive agents. It is an important indicator of durability for structures in reinforced concrete. The presence of reinforcement affects the concrete cover and the permeability. The present study contributes the following results:

(a) The presence of steel bars embedded in concrete, in parallel with the flow associated with the inlet pressure, leads to an increase of the permeability of the composite material due to the steelconcrete interface (particularly porous) and to cracking induced by restrained shrinkage (which can be connected with the steel-concrete interface). In these interfaces and induced cracks, the transfer is accelerated, (b) Steel-concrete interfaces modify the gas flow kinetics in reinforced concrete. For reinforced samples, tests showed that two transfer mechanisms existed: a sudden jump reflecting the effect of the steel-concrete interface and a more progressive transfer, characteristic of the permeability in concrete, (c) At high degrees of saturation (above 60% moisture saturation), the concrete-steel interface is the main gas transfer vector in reinforced concrete; it is desaturated and connected to the surface while the concrete remains impermeable to gas. It is important to model permeability in structures subjected to a variety of environmental conditions.

(d) By representing the defect as a crack, the equivalent opening can be calculated from the air flow.

The evolution of the damage of the steel-concrete interface with drying is reflected by an increase in the opening of the equivalent crack. Even small defects (equivalent opening of some micrometres) are sufficient to obtain permeability twice that measured on plain concrete. This should be taken into account in calculations used for prediction.

Finally, the present study opens up perspectives for the characterization and quantification of the geometry of the steel-concrete interface according to the type of reinforcement. For this, it will be necessary to continue the experimental programme on different types of steels and different thicknesses of samples. These studies would contribute to better predictions of the durability of reinforced concrete structures.

Fig. 1 :

 1 Fig. 1: Experimental apparatus

Fig. 2 :

 2 Fig. 2: Reinforced concrete for QO measurement: case n°1

Fig. 3

 3 Fig. 3 Reinforced concrete for Qo measurement in this study: case n°2

Fig. 4 :

 4 Fig. 4: Types and codes of specimens

Fig. 5 : 4 . 4 .

 544 Fig. 5: Description of the samples SrP/i, SrR2/i, SrR3/I and SrR5/i

-

  Sr is the degree of saturation; i identifies the specimen: i =1; 2; 3.

Fig. 1 :

 1 Fig. 1: Types and codes of specimens

Fig. 6 :Table 4 .

 64 Fig.6: Air flow Q(t)two faces (A and B), tested at the saturation degree equal to 0% for the absolute pressure PI equal to 2 bars (the curves corresponding to R2/2A and R2/2B coincide; the differences were lower than 0.3% of the scale)

Fig. 7 :

 7 Fig. 7 : Apparent permeability (a) and relative permeability kSr/kSr = 6 % (b) for PI = 2 bars

Fig. 8 :

 8 Fig. 8: Air flow kinetics and Time to Reach the Steady State at Sr = 80%, 60%, 30% and 6%

Fig. 9 :

 9 Air flow Q(t)calculation of Q1 (Sr = 0%)

Fig. 11 :

 11 Fig. 11: Permeability zones in R5 (a) and permeability zones in R2 and R3 (b)

Fig. 13 :

 13 Fig. 13: Detachment of the reinforcement from the concrete at steel-concrete interface

Fig. 14 :

 14 Fig. 14: Defect opening, w, for two assumptions of flow coefficient, ξ, equal to 1 (a) and 0.08 (b)

Table 1 .

 1 Concrete mix for 1 m3

	Constituents	[kg]
	Sand 0/4 rec GSM LGP1	830
	Gravel 4/11 R GSM LGP1	445
	Gravel 8/16 R BALLOY	550
	Cement CEM I 52.5 NCE CP2 NF	320
	Plasticizer SIKAPLAST TECHNO 80	2.4
	Water	213

Table 2 .

 2 Preconditioning description

	Sr (%)	Temperature (°C)	Drying time (day)	Cumulative mass loss (%)
	90.	20.	0.8	0.8
	80.	40.	1.	1.6
	60.	50.	1.	3.1
	30.	60.	5.	5.9
	6.	60.	22.	7.8
	0.	105.	2.	8.2

Table 3 .

 3 Concrete properties

	Porosity P [%]	18.8 ± 0.1
	Porosity R2 [%]	19.3 ± 0.3
	Porosity R3 [%]	19.4 ± 0.2
	Porosity R5 [%]	18.8 ± 0.2
	Apparent volumetric mass, P [kg/m 3 ]	2107.3 ± 3.8

stephane.multon@insa-toulouse.fr

Acknowledgment

The authors acknowledge the financial support provided by the project "Non-destructive evaluation of containment of nuclear power plants" (ENDE) financed by the Programme Investissement d'Avenir (PIA -Centre National de la Recherche Scientifique, délégation Provence et Corse, France). The opinions presented in this paper reflect only those of the authors and do not necessarily represent the opinions of the funding agencies.


Grading

Once the visits for the 2012-2013 evaluation campaign had been completed, the chairpersons of the expert committees, who met per disciplinary group, proceeded to attribute a score to the research units in their group (and, when necessary, for these units' in-house teams). This score (A+, A, B, C) concerned each of the six criteria defined by the AERES. NN (not-scored) attached to a criteria indicate that this one was not applicable to the particular case of this research unit or this team. Criterion 1 -C1 : Scientific outputs and quality ; Criterion 2 -C2 : Academic reputation and appeal ; Criterion 3 -C3 : Interactions with the social, economic and cultural environment ; Criterion 4 -C4 : Organisation and life of the institution (or of the team) ; Criterion 5 -C5 : Involvement in training through research ; Criterion 6 -C6 : Strategy and five-year plan.

With respect to this score, the research unit concerned by this report (and, when necessary, its in-house teams) received the following grades:  Grading table of the unit: LABORATOIRE D'ETUDE DU RAYONNEMENT ET DE LA MATIERE EN ASTROPHYSIQUE C1 C2 C3 C4 C5 C6

The LERMA2 project results from the merging of two laboratories, LERMA and LPMAA.

LERMA is one of the laboratories of the Observatoire de Paris; it is located on 5 sites: mostly at the Paris site of the Observatoire de Paris and at the ENS (Paris), but also at the Meudon site of the Observatoire de Paris, at Cergy-Pontoise and at Ivry/Jussieu (Université Pierre et Marie Curie).

LPMAA is a laboratory located in Jussieu, under the supervision of CNRS and UPMC.

In this report, the past activities of both laboratories will be analyzed separately, and the analysis of the LERMA2 project will be detailed in section 2. Moreover, as the individual teams do not have an independent policy, most of the comments concerning e.g. the interactions with the socio-economic environment, internal organisation, training, will be discussed in the general laboratory section except where otherwise needed. 2  Assessment of the unit

Management team

Strengths and opportunities

Scientific excellence and interdisciplinarity are two clear very strong points of LERMA2. This is favoured by the scientific environment of the laboratory in the Paris area, where interactions with other astrophysics and physics laboratories are relatively easy, and contacts with excellent students simple. This could have been better acknowledged in the SWOT analysis. The conjunction of top-level scientists engaged in top priorities of astronomy and the availability of new world class facilities (e.g. Herschel, Planck, Alma, and NOEMA) accounts for the past successes of the laboratory and prepares well for a bright future.

The committee also believes that the merging of LPMAA and LERMA has been well prepared and gives excellent opportunities to the future laboratory to develop strongly visible activities at the interface between molecular physics, astrophysics and atmospheric sciences.

The committee is happy to see that many recommendations from the previous LERMA visiting committee (four year ago) have been implemented. In particular the organisation in poles is seen by the committee as a very efficient move.

Weaknesses and threats

The complexity of the laboratory, with 5 sites, located on the premises of two universities, one « grand établissement » and one « école normale supérieure » makes the management of the laboratory difficult and the coordination of the policies of those 4 institutions plus CNRS an issue. Clearly, this does not impact the scientific production of the laboratory, and decreasing significantly the number of sites does not seem possible on the short/medium term.

LERMA2 also covers a large number of themes, ranging from cosmology to the Earth atmosphere. While there is a clear link between these themes which are connected in part by observation techniques, setting long term priorities in coordination with all institutions involved in LERMA2 and having a stronger focus on these, would be needed.

The visiting committee noted that the project does not develop a long term strategy, but is essentially based on the continuation of existing activities. This is neither unusual nor unexpected in domains for which programming is not central (as e.g. in instrumentation). The committee believes that NOEMA could be an example of such potential developments which could involve several poles. NOEMA is indeed mentioned in the project, but could have been given more emphasis. In a context where top-level senior scientists will leave, this will be of particular importance, as new opportunities might appear for their replacement. The recruitment plan, in particular for the research staff, has suffered from the absence of priorities, and, as it is now, is unrealistic.

Recommendations

-

Do not increase the complexity of the laboratory;

-Set long term priorities (see above). The opportunity offered by the possibility of a senior appointment at ENS must be carefully studied;

-Site communication still requires efforts. The organisation of internal meeting days every year must be a priority, even in financially difficult times. In the same vein, more meetings involving several sites should be organized, and an efficient video-conference system would be most helpful in this context. Videotransmission of seminars is an option which could also be considered;

-Give the students an opportunity to visit all sites;

-The management is encouraged to develop the scientific life in the poles which are relatively broad in terms of thematic range and are scattered over sites which can be distant;

-

The role of various bodies (laboratory council, executive committee, site directors …) should be clarified and understood by everybody. The visiting committee was for example unsure that the site directors should be allowed to take strategic decisions;

-

In each site, try to find office space for staff from another site;

-

The availability of office space has become critical and should be addressed by hosting institutions in a coherent way.  3  Detailed assessments of the existing LERMA

Assessment of scientific quality and outputs

The scientific production of LERMA is outstanding, with more than 150 refereed publications per year on average, or approximately one publication per year per permanent researcher having a LERMA member as first author. This is significantly above the French average in astronomy. The number of citations per paper is also high, ranging from 15 (papers published in 2011) to 20 (papers published in 2007). As a comparison, the average number of citations of papers published in Astronomy and Astrophysics in 2011 is slightly less than 9.

The scientific output of LERMA is also large in domains such as instrumentation, with for example the delivery of two SIS mixers of Herschel HIFI band 1, which was done during the period 2003-2007, but obviously contributed to the scientific success of Herschel during the present period. The production of databases (e.g. GALMER, VO databases) which are widely used by researchers from other institutions all over the world is another example of such a production extending beyond the usual acceptation of scientific production.

Assessment of the unit's academic reputation and appeal

Many scientists from LERMA have a well-established international reputation and visibility. The number of citations per paper is of course a measure of this recognition. The fact that LERMA hosts 2 ERC grants (one advanced grant and one starting grant), plus the number of projects funded by ANR (11 over the 2007-2011 period, and participations in several LABEX), or by other funding sources, as well as the fact that half of these (including one LABEX) are under the leadership of LERMA, the participation of LERMA members in international committees or academies (e.g. the French Academy of Sciences or the Royal Astronomical Society) demonstrate very clearly the recognition at the national and international level of the excellence of a significant number of the LERMA staff. As a consequence, the laboratory is able to attract well-known scientists as short term visitors, and the number of applications to post-doctoral positions opened in LERMA is also very large, up to more than 100 in one case. Very clearly, there are a few top world class scientists in the laboratory, and at the same time, the average visibility of the other researchers is high.

As a consequence, the laboratory is quite well-funded by external contracts, and is wealthy. The uneven distribution of post-docs between the different teams does not seem to create internal tensions.

Assessment of the unit's interaction with the social, economic and cultural environment LERMA is one of the very few laboratories in Astronomy in which a spin-up company (Estellus) has been created, providing services in atmospheric and environmental sciences. Tight connections also exist between the R&D/instrumentation group and industrial partners, and the number of applications outside the academic field of technologies developed in LERMA is potentially large. The staffing of the team involved in the THz developments is limited however, as compared to what exists in other laboratories with activities in this domain, and is unlikely to increase by a large factor. The visiting committee therefore recommends setting priorities and organizing the technical developments in such a way that the top priorities are above the critical mass.

Outreach is well-organized at the laboratory level, and is a strong point. LERMA is for example coordinating the European project EU-HOUMW which consists in developing and operating small radio-telescopes, one of them being located in the Paris observatory, conceived for education, and has been involved, at high levels, in other projects. It is worth noting that some of the top LERMA scientists play a very active role in this domain. The visiting committee has been impressed by the activities in this domain, and congratulates the direction and the whole staff of LERMA for their efforts.

In this context, the web pages of the laboratory are very disappointing and do not reflect the current activities in the laboratory and not even its actual structure. Given the complexity of the laboratory and the need to have efficient internal communication channels, the LERMA management should urgently change this situation. The committee was informed that this was indeed one of the short term actions foreseen, and the merging with LPMAA could be a good opportunity to install a new website.

Assessment of the unit's organisation and life

The visiting committee noted and appreciated that recommendations from the previous visiting committee had been taken into account and implemented, resulting in a very positive evolution. Some progress is still desirable though.

The committee noted that the staff has, with very few individual exceptions, very little concerns. The laboratory is viewed as wealthy, and the workload on both the administrative and technical staff seems to be acceptable, indicating no major staffing problem.

The "Conseil de laboratoire" does not play its role, as its involvement in the definition of e.g. scientific priorities, long term strategy, etc. is relatively small. It is kept informed by the management, but is neither active nor proactive. The current council members and the general laboratory staff do not seem to consider this as a problem, which could also be a concern. A likely explanation for this would be that the management decisions are generally accepted by the staff, and perhaps also that LERMA staff is focused on scientific productivity. In any case, a clarification of the role of the "Conseil de laboratoire" should be made and accepted by everybody. The management practice should then be in agreement with existing texts. The merging with LPMAA, where the practice is quite different, makes this clarification even more important.

Assessment of the unit's involvement in training through research

LERMA is traditionally heavily involved in training by research at doctoral level. One LERMA membre (P. Encrenaz) was the directore of the doctoral school Astronomie et Astrophysique d'Ile de France (ED 127) for many years. And during the reporting period, two LERMA members have been acting as members of the boards of the doctoral scools ED 389 (La Physique de la Particule à la Matière Condensée) and 417 (École Doctorale Sciences et Ingénierie). 60% of the PhD students were enrolled in École Doctorale ED 127, Astronomie et Astrophysique d'Ile de France, while the other 40% belonged to one of 8 different ED's, namely: ED 129, 389 or 417 (to which LERMA is officially affiliated), ED 107 or ED 381 (alternative doctoral schools in physics at ENS and UPMC), and, for a very small number of theses in cosupervision with external institutions, ED 52, 227, or 422 (respectively with ENS Lyon, Museum National d'Histoire Naturelle, and Orsay University).

The involvement of LERMA in training activities is quite good. The committee had a positive appreciation of the fact that a fraction of the teaching was made in « classes préparatoires ». A solution should be found for finding shared office space on university premises for all teaching staff.

The number of PhD students is still relatively low (23 on 30/6/2012); at the time of the previous visiting committee, there were 22 PhD students, and it was recommended to increase this number. Efforts should be made to attract students from engineering schools in the instrumentation team, at a time when these schools start considering that a PhD can be a valuable addition to their diploma.

The visiting committee also supports the director's efforts to have more people having their HDR.

Assessment of the five-year plan and strategy

See section 2 "assessment of the unit" above.

 Detailed assessments of the existing LPMAA Assessment of scientific quality and outputs

LPMAA is an excellent fundamental research laboratory in molecular physics and fundamental/applied spectroscopy with applications to atmospheric physics, astrophysics and environment research.

LPMAA is led by dynamic and young scientists. The number of publications is high, with an average of 21 publications in refereed journals per year, among which 9 having a first author from LPMAA. Given the fact that all but one of the present LPMAA staff have heavy teaching duties and that the laboratory had to move during the reference period, this is an achievement. The committee noted, however, that this high number of publications is unevenly distributed.

The strength of this laboratory is its scientific excellence, with applications ranging from space to our atmosphere, its ability to produce reference data and to undertake the technological developments needed for its research.

Assessment of the unit's academic reputation and appeal

The LPMAA scientists benefit from a high visibility at the national and international levels. This can be measured by, for example, the number of ANR projects (3, among which 2 have a PI from LPMAA), contracts from other sources, including the Canadian Space Agency, the fact that the director of LPMAA is the coordinator of the FP7 project VAMDC or the fact that members of LPMAA are members of various scientific committees.

Another indication of the visibility of the laboratory is the co-supervision of a thesis between the Netherland and LPMAA on desorption processes induced on cold ices by UV photons.

Assessment of the unit's interaction with the social, economic and cultural environment

There is nothing above what is expected from a laboratory of this size and type to note in this domain.

Assessment of the unit's organisation and life

The laboratory being small, the decision process involves the General Assembly (meetings every two months) where budgets, recruitments, scientific priorities, and political orientations are discussed. The internal communication is handled through the General Assembly, coffee breaks and internal meetings.

LPMAA is a small group, well organized, where decisions are obviously taken in a consensual way. It was for example quite clear, from the discussions the committee had with the staff and management, that the merging with LERMA has been well prepared by thorough discussions covering all possible issues, and involving everybody. The committee noted that although the move back to Jussieu had a significant impact on the laboratory activity, this was organized in such a way as to minimize it, with a collective approach of the various problems.

Assessment of the unit's involvement in training through research

LPMAA is affiliated to ED 389 (La Physique de la Particule à la Matière Condensée).

All permanent research staff but one having teaching duties, it is no surprise that the involvement of the laboratory in teaching is strong. The number of PhDs supervised, in view of the low number of HDR, is fair. The committee was impressed by the number of trainees at the Licence and Master levels.

Assessment of the five-year plan and strategy

See section 2 "assessment of the unit" above.

 Team-by-team analysis

The laboratory has chosen to label its teams "poles". In the following, the word "pole" is in general used to refer to a specific team, e.g. "Pole 1", whereas "team" is ised in a more generic sense.

Team 1 :

Galaxies and Cosmology

Name of team leader: Qualified research supervisors (with an HDR) or similar positions 6 5,5

 Detailed assessments

Strengths and opportunities

This Pole covers many aspects of modern extragalactic and cosmological research, including the primordial universe, the Cosmic Microwave Background anisotropies, the epoch of reionization, high redshift galaxies, clusters of galaxies and the dynamics of local galaxies. The major highlights comprise the achievements obtained with the Planck ESA satellite for cosmology (other LERMA researchers in Pole 2 exploit the data for galactic science), accurate simulations of the 21cm HI line in absorption and emission during the epoch of reionization with consequences on the design of SKA, the first detection of molecular CO gas in cooling flows in the centre of galaxy clusters as well as the importance of the AGN feedback to trigger the flows, and the study of streams of stars as observed with Megacam on the CFHT, degrees away from the Andromeda Galaxy, to the nature of the dark matter (cosmology within the local universe).

Pole 1 thus has a multi-focused approach in extragalactic studies, using in a coherent way theory, simulations, observations and instrumentation to tackle a clear-cut problem. The 2010 ERC in Pole 1 with about 10 post-doctoral fellows shows its attractiveness and international standing, as well as the participation in 6 ANRs. Heavy numerical studies (using National GENCI facilities, and PSL and ERC Momentum mesocenters) are among the core of Pole 1 activities.

Involvements in "Hands-on Universe" and AMA09 (World Year of Astronomy) are among the activities which demonstrate the role of Pole 1 in outreach activities.

The project of pole 1 is basically to continue the gold mining in the Herschel and Planck datasets, the numerical simulations, and observations with world-class telescopes (ALMA, IRAM, ESO, CFHT), especially in the (sub)millimetre domain, and on the longer term in the centimetre domain with SKA.

Weaknesses and threats

Pole 1 has a world-class reputation and scientific production which should be continued as far as it is possible. In this context, it is important to envision the evolution of the group after the end of the present ERC, and on the longer term when senior researchers may have retired. The scientific questions approached by the group are diverse, from cosmology to CO in nearby galaxies. This is a priori good but it might also be dangerous if individuals independently develop their own research separately from the rest of the pole members.

Recommendations

A reflection to reinforce and better prioritize projects and define the group core activities is important to ease the mid-to long-term evolution of the pole. Also since the group is mostly working on the ISM in galaxies, it could be interesting to develop more direct collaborations with activities in Pole 2. Teaching is important (with about 500 hours TD per year) in the group, but training through research could be improved with 1 or 2 more PhD students. It is for instance seen as a pity that the ERC does not employ any PhD student to fully benefit from the exciting, present-day scientific activity of the group with as many as 10 post-docs.

Strengths and opportunities

This Pole is central to the LERMA activity, since it is concerned with scales intermediate between those of Poles 1 and 3. It is also arguably the pole that combines the widest range of techniques, from multiwavelength observations and laboratory experiments at one extreme, to theory and numerical simulation at the other. Not only are the talented individuals involved in this node delivering research that is of the very highest quality and profound international impact, they are also very adept at exploiting the advantages to be gained by combining their different approaches in imaginative ways. Central to the activity are detailed magneto-hydrodynamic simulations, coupled with sophisticated thermal, chemical and radiative schemes, which are shedding new light on the dynamics of the interstellar medium, the collapse of prestellar cores, the formation and evolution of circumstellar discs, the physics of protostellar jets and outflows, and the transport processes operating in stars. A major highlight is the work on turbulent dissipation in molecular clouds, which has established the different mechanisms at work, and -by modeling the detailed space and time-dependent chemistry -determined the observational signatures of this critical process, and explained the formation of CH+, HCO+, CO and rotationally excited H2. A second highlight involves controlled plasma experiments being performed in the laboratory, that are analogues of the mechanisms presumed to operate in interstellar and circumstellar space and serve not only to give crucial insights into, for example, protostellar jets and shocks, but also to provide checks on the fidelity of the magneto-hydrodynamic code. Other highlights include the observation of mid-infrared coreshine and the implications for the size distribution of dust grains; and the modeling of isotopic fractionation and ortho-para ratios, and their use as chemical clocks to constrain the ages of prestellar cores.

The addition of a small team working on the ISM coming from LUTH, another laboratory of Paris Observatory, will help strenghtening Pole 2, and will favour LERMA2 participation in the development of the theoretical virtual observatory.

Weaknesses and threats

Our only significant concern with this Pole is that two senior members have recently left (for jobs that afford them better pay and working conditions, and more time for research); a third senior and highly active member of the team has recently retired, and whilst we are confident that the contributions of these individuals to the research of LERMA2 will continue in the short term, it is essential that coherent plans for their replacement in the medium term be carefully formulated and vigorously implemented. There are some very bright young scientists in the group, but, without new appointments -including at least one senior to provide vision, guidance, and leadership -the momentum of the group is unlikely to be maintained. This would be a great loss, both to French astronomy, and to the wider international astronomy community.

Recommendations

The proposed future program aims to continue exploring many of these successful areas. However with the demise of Planck and Herschel, the Pole needs to be careful to develop strategies to replace the important role these instruments have played within the science of the pole.

Team 3 :

Molecules Name of team leader: Mr Jean-Hugues Fillion Workforce The research activity of pole 3 is dedicated to molecular physics applied to astrophysics and Earth atmosphere. This activity is strongly interdisciplinary, connecting physics and chemistry, astrophysics and even technological development. The pole gathers theoreticians and relies upon innovative experimentation, sophisticated molecular physics calculations and high-resolution spectroscopy studies to understand the fundamental mole-cular processes occurring in various space environments both in the gas phase and on grains.

Significant successes have been achieved in LERMA over the last five years. These include: 1) ultra-high precision HD lines measured at extreme UV wavelengths, providing a database for comparison with high-redshift quasar spectra in order to probe possible proton-electron mass ratio variations on a cosmological time scale; 2) accurate collisional rate coefficients computed for the rotational excitation of SO2 by o/p-H2 giving new absorption and maser line profiles that will be useful to trace physical conditions of the ISM; 3) successful experimental synthesis of H2, H2O, CO2 and NH2OH on cold dust grains analogs; 4) sticking measurements of H2, D2 on amorphous water ice and silicates, revealing important Isotopic effects. The number of publications for this pole is large despite heavy teaching duties that most members of the pole face all over the year.

Activities at LPMAA include ultra-high resolution and precision spectroscopy for spectral parameter determination of molecules for climate researches, isotopic ratio measurement in atmospheric CO2, running the Qualair FTS ground based station, experimental studies on the nuclear spin relaxation in small hydrogenated molecules induced by interaction with solids, experimental studies on the photon induced processes on cold ices, collisional rate coefficient calculations, maintenance of a database of atomic and molecular collisional rates (BASECOL) and finally creation, organization, coordination and scientific contribution to building the Virtual Atomic and Molecular Data Center VAMDC (EU funded project).

The strength of the pole relies upon the combination of its expertise on both theoretical and experimental molecular physics which can address new issues raised by observations, and its inclusion in an astrophysics laboratory where results can be assessed through astrophysical modeling. Its deep involvement in teaching at both the undergraduate and graduate level helps in maintaining tight contacts with students and in sustaining a steady flow in Master 2 or PhD training.

The geographical dispersion of the pole (theoreticians are located in Meudon while most experimentalists are in Cergy-Pontoise, and the LPMAA team is located in Paris) has not prevented the construction of a strong thematic coherence, which could falter with time if members of the pole have no common space where they could meet regularly; this shared place could be in Paris, which would also reinforce exchanges with astrophysicists of pole 2. The committee also noted the need to reinforce the surface reactivity group in Cergy-Pontoise by recruiting on a permanent position an engineer for managing the experimental platform.

One should finally note the deep involvement in training through research at the undergraduate (L) and Master (M) levels as well as PhD thesis supervisions (during the last 5 years, 8 theses have been defended and 4 are in progress). One can list the management of a Master 2 at the University of Cergy-Pontoise, the management of a « Classes préparatoires aux Grandes Ecoles», management duties in two "Ecoles Doctorales", editorial activities and a participation to the creation and the use of a web site for e-learning in astrophysics.

Strengths and opportunities

The merging of LPMAA and pole 3 of LERMA will bring together leading research groups in quantum physics/chemistry, low temperature physics, chemical physics as well as surface science researchers. This will strengthen the research activities of both parts with new synergies already emerging also with other poles of LERMA. The effort made by the theoreticians to enlarge their activities toward the modeling of reactive processes on surfaces is noted and strongly encouraged.

Weaknesses and threats

The committee has some concerns about the future of the atmospheric activities which are rather isolated in the pole.

Recommendations

CNRS and UPMC should decide on whether they want atmospheric activities to continue, and if the answer is positive, keep the team above the critical mass; the development of collaborations with the atmospheric component of Pole 4 or with other laboratories in the Paris area are possible options. The team working on Earth and planet remote sensing is strongly involved in European programs devoted to the observation and modeling of Earth atmosphere in the microwave spectral range. The strength of the team is mostly related to the analysis of ice clouds, for which remarkable scientific strides have been made. The second strong topic studied by the team is the study of Earth surface parameters, like wetland extend, soil moisture, etc. This domain is also very active, with good achievements and participation to several international projects. The team is also working on planetary observation, by contributing to programs like Cassini and Rosetta.

The software instrumental activity deals with processing and storing astrophysical data supplied either by instruments or by numerical simulations. The team is contributing to the creation of new international standards and to the establishment and diffusion of databases.

The committee has noted the excellent scientific production of the THz and remote sensing teams. The links between the 3 teams of the pole can certainly be tightened. The THz team is facing both the departure of two of its major members, namely P.Encrenaz and G.Beaudin, as well as uncertainties in the programming of space projects which, with the notable exception of SWI on JUICE, are not yet decided. On the other hand, the superb performance of the produced devices may find numerous applications in non-astrophysical domains, like security, sensing for the industry, etc. Such devices may also be used for Earth observation from satellites, without needing large additional developments. Whether this is the role of LERMA2 is an open question, and transferring part of this activity to more applied laboratories could be considered. If this activity were to remain as a foremost one in the laboratory, the team should be reinforced in order to remain competitive with existing teams in other laboratories.

Strengths and opportunities

The committee has noted the excellent scientific production of the THz and remote sensing teams.

Weaknesses and threats

The links between the 3 teams of the pole can certainly be tightened.

Recommendations

If this activity were to remain as a foremost one in the laboratory, the team should be reinforced in order to remain competitive with existing teams in other laboratories. Qualified research supervisors (with an HDR) or similar positions 0,5 0,5

 Detailed assessments This is not a scientific team, but it is organized as a separate "pole" in LERMA, and needs therefore to be assessed as such.

The creation of a specific pole gathering the administrative and technical staff is seen by the committee as a positive move. This has happened in many other laboratories, and has been quite beneficial in these. An additional advantage in the case of LERMA2 is that it will promote discussions between technical staff working in different poles and sites. It has created some concerns among the staff, which is not a surprise, as this also happened in all places where this organization has been put in place. However, the committee has not seen any strong opposition from the staff. The committee therefore encourages the LERMA2 management to develop discussions and meetings with the staff, and agrees with the gradual approach adopted by the management.

The committee had little to say on the organization of the so-called « services d'observation » which are defined and assessed at the national level by CNRS/INSU. It encourages however the LERMA2 management to evaluate the workforces involved in each activity, their visibility and scientific impact, and eventually set priorities. This is apparently the management's approach, and most of the elements needed to have this evaluation made are already available.

Specific points to be mentioned:

There has been no specific problem, and the visit went quite smoothly. The committee regrets however that there has not been enough time devoted to questions and discussion during the formal presentations, as most speakers considered that their presentation should last longer than the time slot allocated (including questions).

Moreover, the LERMA written document was made available late and could have been more synthetic (and checked for misprints and missing words). A significant fraction of the section in the LPMAA document describing the organization of the laboratory was written in French.

These minor problems had no significant impact on the committee work. The committee found that the visits to various sites (including the video presentation of Cergy) were well-organized and prepared, and were very instructive.

  -GILBERT, Université Paris-Sud (representing CoNRS) Ms Marie-Renée DE BACKER, Université de Reims (representing CNU) Scientific delegate representing the AERES: Mr Michel BLANC Representative(s) of the unit's supervising institutions and bodies: Mr Claude CATALA, Observatoire de Paris Mr Paul INDELICATO, Université Pierre et Marie Curie Mr Werner KRAUTH, ENS/département de Physique Mr Olivier La MARLE, CNES Mr Yves LAZLO, ENS Mr Denis MOURARD, CNRS/INSU Mr Reynald PAIN, Université Pierre et Marie Curie Mr Guy PERRIN, Observatoire de Paris Mr Jean-Pierre REYES, CNRS/DR2 Ms Pascale ROUBIN, CNRS/INP Mr Stéphane SERFATY, UCP Mr Gilles TRAIMOND, CNRS/DR5 1  Introduction History and geographical location of the unit

  Postdoctoral students having spent at least 12 months in the unit 2Number of Research Supervisor Qualifications (HDR) taken 1Qualified research supervisors (with an HDR) or similar positions 15 Detailed assessments

  Postdoctoral students having spent at least 12 months in the unit 0Number of Research Supervisor Qualifications (HDR) taken 1Qualified research supervisors (with an HDR) or similar positions 4,5 Detailed assessmentsPole 4 of LERMA is dedicated to researches in instrumentation, including both hardware and software activities, and in Earth and planet remote sensing. The pole is organized along 3 teams working, respectively on -THz components and instrumentation, -Earth and planet remote sensing, and -software. Because of its technological objectives, Pole 4 incorporates a technical staff more numerous than the other three.The THz instrumentation group has produced significant achievements during the 2007-2012 period, based on a unique expertise and know-how in high-frequency devices and systems for radio-astronomy. The group has supplied several programs like HIFI on Herschel with state-of-the-art components, for example SIS mixers (the components were delivered prior to 2007 and went through tests in 2007). The group is involved in several new projects, like CIDRE, JUICE and ISMAR. With the technical help of LPN in Marcoussis, the group is now producing mixers and sources, based on SIS, Schottky diodes and HEB, which are among the best in the world. The recently achieved 4-microW power for an electronic source (developped in collaboration with JPL) operating at 2.5 THz and at room temperature is really impressive.

  Postdoctoral students having spent at least 12 months in the unit 0Number of Research Supervisor Qualifications (HDR) taken 0

  de M. Blanc, Délégué AERES et de J.-M. Hameury, Président du comité 9h40 25 mn Bilan du LERMA (M. Pérault directeur LERMA) 10h05 10 mn Bilan du LPMAA (M.-L. Dubernet directrice LPMAA) 10h15 20 mn Projet LERMA² (M. Pérault directeur LERMA) 10h35 25 mn Discussion générale sur les Bilans et le des représentants des sections avec les personnels en marge de la visite

7

  Statistics by field: ST on 10/06

Unit workforce Number as at 30/06/2012 1 Number as at 01/01/2014 2

  LERMA (present). Director: Mr M. PÉRAULT; deputy director: Mr L. PAGANI; technical director: Mr J.M. KRIEG LPMAA (present). Director: Ms M-L. DUBERNET; technical director: Mr P. JESECK. Project LERMA2. Director: Mr M. PÉRAULT; deputy directors: Ms M. GÉRIN, Ms C. BOURSIER, Mr F; DULIEU; technical director: Mr J-M. KRIEG.

	AERES nomenclature
	ST3 Earth and universe sciences
	Unit workforce:
				2014-2018
				Number of project producers 3
	N1: Permanent professors and similar positions	LERMA : 23 LPMAA : 10	30	28
	N2: Permanent researchers from Institutions and similar positions	LERMA : 17 (16,8)	18 (17,8)	18
		LPMAA : 1
	N3: Other permanent staff (without research duties)	LERMA : 32 (31,2)	35 (33,8)	9
		LPMAA : 9
	N4: Other professors (Emeritus Professor, on-contract Professor, etc.)	LERMA : 13 LPMAA : 1	12	8
	N5: Other researchers from Institutions (Emeritus Research Director, Postdoctoral students, visitors, etc.)	LERMA : 9 LPMAA : 0	5	9
	N6: Other contractual staff (without research duties)	LERMA : 4 LPMAA : 3	3	0
	TOTAL N1 to N6	LERMA : 98 (97)

LPMAA : 24 Unit workforce Number as at 30/06/2012 Number as at 01/01/2014

	Doctoral students	LERMA : 23 LPMAA : 5
	Theses defended	LERMA : 30 LPMAA : 5
	Postdoctoral students having spent at least 12 months in the unit*	LERMA : 6 LPMAA : 0
	Number of Research Supervisor Qualifications (HDR) taken	LERMA : 3 LPMAA : 3
	Qualified research supervisors (with an HDR) or similar positions	LERMA : 33 LPMAA : 6

  Mrs Françoise COMBES

	Workforce
	Team workforce	Number as at 30/06/2012	Number as at 01/01/2014	2014-2018 Number of project
					producers
	N1: Permanent professors and similar positions	4,5	4,5		4,5
	N2: Permanent EPST or EPIC researchers and similar positions	3	2,5		2,5
	N3: Other permanent staff (without research duties)	0	0		0
	N4: Other professors (PREM, ECC, etc.)	4,5	6		6
	N5: Other EPST or EPIC researchers (DREM, Postdoctoral students, visitors, etc.)	4	1		1
	N6: Other contractual staff (without research duties)	1	1		0
	TOTAL N1 to N6	17	15		14
	Team workforce	Number as at 30/06/2012	Number as at 01/01/2014
	Doctoral students	3
	Theses defended	7,5
	Postdoctoral students having spent at least 12 months in the unit	4
	Number of Research Supervisor Qualifications (HDR) taken	1

(100,6)

Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, LERMA2, OP, ENS, UPMC, UCP; Mr Michel PERAULT

 Supervising bodies' general comments

Conduct or programme of visit:

The visit began by a series of presentations of both laboratories and of the thematic poles, during midafternoon of the first day. This was followed by visits on the various sites attended by subgroups of the committee split in two parts. The afternoon of the second day was devoted to the formal meetings with staff categories and representatives of the overseeing institutions. The internal discussions of the committee took place during the evenings of the first and second days (about one hour each), and during the morning of the last day (8:30 -12:30). Preliminary conclusions were then given to the laboratory staff by the visiting committee chair.

The detailed program of the visit is given below.