Jonathan Ginzburg

Raquel Fernández

David Schlangen

Self-addressed questions in disfluencies

The paper considers self-addressed queries -queries speakers address to themselves in the aftermath of a filled pause. We study their distribution in the BNC and show that such queries show signs of sensitivity to the syntactic/semantic type of the sub-utterance they follow. We offer a formal model that explains the coherence of such queries.

Introduction

How to characterize the context associated with hesitations? For production, [START_REF] Clark | Using uh and um in spontaneous speech[END_REF] claimed that fillers like 'uh' and 'um' should be treated as words with different distributions ('uh' more for short pauses,' um' for long pauses) and with discourse functions intended by the speaker. ( [START_REF] Horne | Attitude reports in spontaneous dialogue: Uncertainty, politeness and filled pauses[END_REF] proposes a related account for Swedish glottalized filled pauses. Clark and Fox-Tree's hypothesis has more recently been strongly disputed for distributional differences [START_REF] O'connell | Uh and Um Revisited: Are They Interjections for Signaling Delay?[END_REF] as well as with respect to speakers' intentions [START_REF] Corley | Hesitation disfluencies in spontaneous speech: The meaning of 'um[END_REF].

In this paper we consider a phenomenon that occurs in the aftermath of a filled pause, namely self-addressed queries, exemplified in ((1)):

(1) a.

Carol The question we investigate is whether such queries are essentially reflexive or show signs of sensitivity to the (the syntactic/semantic type of) the sub-utterance they follow. Section 2 describes a corpus study we ran on the BNC to investigate this issue. The study demonstrates clearly a strong effect, with distinct distributions clustering around a small number of triggering contexts. After brief discussion of the results in section 3, section 4 provides a formal model in which we analyze the coherence of such moves, as part of an account of what we call forwards-looking disfluences -disfluencies where the moment of interruption is followed by a completion of the utterance which is delayed by a filled or unfilled pause (hesitation) or a repetition of a previously uttered part of the utterance (repetitions).

Conclusions and further work are provided in section 5.

Corpus study

We ran a corpus study on the BNC, using the search engine SCoRE ( [START_REF] Purver | Score: A tool for searching the bnc[END_REF]) to search for all self-addressed queries. We searched using the pattern 'noun preceding 'er' or 'erm' preceding a wh word, adjacent to a verb.'.

Discussion

Table 1 indicates that self-addressed queries occur in a highly restricted set of contexts, above all where an NP is anticipated and after 'the'. Moreover, the distribution of such queries across these contexts varies manifestly: the anticipated NP contexts involve predominantly a search for a name or for how the person/thing is called with some 'who'-questions as well, whereas the post 'the' contexts only allow 'what' questions, predominantly of the form 'what does X call Y'; anticipated location NP contexts predominantly involve 'where' questions.

The final two classes identified are somewhat smaller, so generalizations there are less robust -nonetheless, the anticipated predicative phrase and post 'say' context involve seem to involve quite distinct distributions from the other classes mentioned above.

Forward Looking Dysflencies in a dialogue model 4.1. Dialogue GameBoards

We start by providing background on the dialogue framework we use here, namely KoS (see e.g. [START_REF] Ginzburg | Computational models of dialogue[END_REF][START_REF] Ginzburg | The Interactive Stance: Meaning for Conversation[END_REF]). On the approach developed in KoS, there is actually no single context -instead of a single context, analysis is formulated at a level of information states, one per conversational participant. The dialogue gameboard represents information that arises from publicized interactions. Its structure is given in (3) -the spkr,addr fields allow one to track turn ownership, Facts represents conversationally shared assumptions, Pending and Moves represent respectively moves that are in the process of/have been grounded, QUD tracks the questions currently under discussion, though not simply questions qua semantic objects, but pairs of entities which we call InfoStrucs: a question and an antecedent sub-utterance. 1 This latter entity provides a partial specification of the focal (sub)utterance, and hence it is dubbed the focus establishing constituent (FEC) (cf. parallel element in higher order unification-based approaches to ellipsis resolution e.g. [START_REF] Gardent | Computing parallelism in discourse[END_REF].) 2

(3) DGBType= def

The basic units of change are mappings between dialogue gameboards that specify how one gameboard configuration can be modified into another on the basis of dialogue moves. We call a mapping between DGB types a conversational rule.

The types specifying its domain and its range we dub, respectively, the preconditions and the effects, both of which are supertypes of DGBType.

Examples of such rules, needed to analyze querying and assertion interaction are given in (4). Rule (4-a) says that given a question q and ASK(A,B,q) being the LatestMove, one can update QUD with q as QUD-maximal. QSPEC is what characterizes the contextual background of reactive queries and assertions. (4-b) says that if q is QUD-maximal, then subsequent to this either conversational participant may make a move constrained to be q-specific (i.e. either About or Influencing q). 3 (4) a. ________________ 1 Extensive motivation for this can be found in [START_REF] Fernández | Non-sentential utterances in dialogue: Classification, resolution and use[END_REF][START_REF] Ginzburg | The Interactive Stance: Meaning for Conversation[END_REF], based primarily on semantic and syntactic paralleism in non-sentential utterances such as short answers, sluicing, and various other fragments. 2 Thus, the FEC in the QUD associated with a wh-query will be the wh-phrase utterance, the FEC in the QUD emerging from a quantificational utterance will be the QNP utterance, whereas the FEC in a QUD accommodated in a clarification context will be the sub-utterance under clarification. 3 We notate the underspecification of the turn holder as 'TurnUnderspec', an abbreviation for the following specification which gets unified together with the rest of the rule:

(4) b.

Forwards-looking disfluencies and selfaddressed queries

Our starting point is the account developed within the KoS framework for Clarification Requests (see e.g. [START_REF] Purver | Clarie: Handling clarification requests in a dialogue system[END_REF][START_REF] Ginzburg | Situation semantics: from indexicality to metacommunicative interaction[END_REF]): in the aftermath of an utterance u a variety of questions concerning u and definable from u and its grammatical type become available to the addressee of the utterance. These questions regulate the subject matter and ellipsis potential of CRs concerning u and generally have a short lifespan in context. We argue that disfluencies can and should be subsumed within a similar account, a point that goes back to [START_REF] Schegloff | The preference for self-correction in the organization of repair in conversation[END_REF]: in both cases (i) material is presented publicly, (ii) a problem with some of the material is detected and signalled (= there is a 'moment of interruption'); (iii) the problem is addressed and repaired leaving (iv) the incriminated material with a special status, but within the discourse context. Concretely for disfluencies -as the utterance unfolds incrementally questions can be pushed on to QUD about what has happened so far, as with Backwards Looking Disfluencies (BLDs) (e.g. what did the speaker mean with subutterance u1?) or what is still to come, as with Forwards Looking Disfluencies (FLDs) (e.g. what word does the speaker mean to utter after sub-utterance u2?).

We specify FLDs with the update rule in (5) -given a context where the LatestMove is a forward looking editing phrase by A, the next speaker -underspecified between the current one and the addressee -may address the issue of what A intended to say next by providing a co-propositional utterance: 4,5 (5) ________________ 4 This rule is inspired in part by Purver's rule for fillers, (91), p. 92, ( [START_REF] Purver | The theory and use of clarification in dialogue[END_REF]). Given that our rule leaves the turn ownership unspecified we unify FLDs with fillers. CoPropositionality for two questions means that, modulo their domain, the questions involve similar answers. For instance 'Whether Bo left', 'Who left', and 'Which student left' (assuming Bo is a student) are all co-propositional. In the current context co-propositionality amounts to: either a CR which differs from MaxQud at most in terms of its domain, or a correctiona proposition that instantiates MaxQud. Rule (5) differs from its BLD analogue, in two ways. First, in that the preconditions involves the LatestMove having as its content what we describe as an FLDEdit move, which we elucidate somewhat shortly. Words like 'uh', 'thee' will be assumed to have such a force, hence the utterance of such a word is a prerequisite for an FLD. A second difference concerns parallelism: for BLDs it is intuitive that parallelism exists between reparandum and alteration (with certain caveats), given that one is replacing one sub-utterance with another that is essentially of the same type. However, for FLDs there is no such intuition-what is taking place is a search for the word after the reparandum, which has no reason to be parallel to the reparandum. Hence in our rule [START_REF] Fernández | Non-sentential utterances in dialogue: Classification, resolution and use[END_REF], the FEC is specified as the empty set. To make this explicit, we assume that 'uh' could be analyzed by means of the lexical entry in ( 6): [START_REF] Gardent | Computing parallelism in discourse[END_REF] We demonstrate how to analyze ( 7): [START_REF] Ginzburg | Situation semantics: from indexicality to metacommunicative interaction[END_REF] A: Show flights arriving in uh Boston. [START_REF] Shriberg | Preliminaries to a theory of speech disfluencies[END_REF] After A utters u0= 'in', she interjects 'uh', thereby expressing FLDEdit(A,B,'in'). This triggers the Forward Looking Utterance rule with MaxQud.q = λx MeanNextUtt(A,'in',x). 'Boston' can then be interpreted as answering this question, with resolution based on the rule used to interpret (elliptical) short answers. Similar analyses can be provided for [START_REF] Ginzburg | The Interactive Stance: Meaning for Conversation[END_REF]. Here instead of 'uh' we have lengthened versions of 'the' and 'a' respectively, which express FLDEdit moves: (8) a.

And also the-the dog was old.

[2] b.

A vertical line to a-to a black disk [START_REF] Levelt | Monitoring and self-repair in speech[END_REF] Let us return to consider what the predicate 'FLDEdit' amounts to from a semantic point of view. Intuitively, (9) should be understood as 'A wants to say something to B after u0, but is having difficulty (so this will take a bit of time)': Moving on finally to (dysfluent) self addressed queries of the kind described in section 2, on our account such queries are licensed because these questions are co-propositional with the issue 'what did A mean to say after u0'.

Self addressed queries also highlight another feature of KoS's dialogue semantics: the fact that a speaker can straightforwardly answer their own question, indeed in these cases the speaker is the "addressee" of the query. Such cases get handled easily in KoS because turn taking is abstracted away from querying: the conversational rule QSpec, introduced earlier as (4-b), allows either conversationalist to take the turn given the QUD-maximality of q. This contrasts with a view of querying derived from Speech Act Theory (e.g. [START_REF] Searle | Speech Acts[END_REF]) still widely as-sumed (see e.g. [START_REF] Asher | Logics of Conversation[END_REF]), where there is very tight link to intentional categories of 2-person dialogue ('. . . Speaker wants Hearer to provide an answer . . . Speaker does not know the answer . . . ').

Conclusions

In this paper we offer the first detailed corpus study of selfaddressed queries that occur in the aftermath of filled pauses.

We show that such queries show marked signs of sensitivity to the (the syntactic/semantic type of) the sub-utterance u0 they follow. We then offer a formal model from which the possibility for such queries follows directly. An obvious next step is to study differences between the distribution we found in the BNC and that occurring in other languages, as surface syntax in particular of NPs seems to be a significant factor, as does predicational structure.

P

5

 5

( 9 )

 9 FLDEdit(A,B,u0) This means we could unpack (9) in a number of ways, most obviously by making explicit the utterance-to-be-produced u1, representing this roughly as in (10): (10) ∃u1[After(u1,u0) ∧ Want(A,Utter(A,B,u1))]

Table 1 :

 1 Distribution

	This yielded 692

Table 2 :

 2 Distribution

	of Self addressed questions in
	pre NP context
	what's his/her name?	19
	what do they/you call him/her/it?	13
	who was it/the woman?	3
	what's the other one?	3
	what did you/I say?	2
	what did it mention?	2
	Total

Table 3 :

 3 Distribution of Self addressed questions in post

	Det context
	what do/did they/you call it/that/them?	14
	what's it called?	2
	what is it?	3
	what am I looking for?	1
	Total	20

Table 4 :

 4 Distribution of Self addressed questions in post Loc Prep context

	where is it?	3
	where do they call that?	2
	what's the name of the street/address?	2
	what do they call X?	2
	where do we go?	1
	where did it say now?	1
	what is it?	1
	Total	12

Table 5 :

 5 Distribution

of Self addressed questions in postcopular context. what is she/it? 3 what's the word I want? 1 what do you call it? 1 Total 5

Table 6 :

 6

Distribution of Self addressed questions in post 'say' context what did X say? 3 where did I get the number? 1 Total 4

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		D D i i S S S S 2 2 0 0 1 1 3 3
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Proceedings of Disfluency in Spontaneous Speech, DiSS 2013

Acknowledgements

This work has been partially funded by the Labex EFL (ANR/CGI).


Hocine Siad
email: hcine_siad@yahoo.fr

Mohamed Lachemi

Siham Kamali Bernard

Mustafa Sahmaran

Anwar Hossain

Assessment of the Long-term Performance of SCC Incorporating Different Mineral Admixtures in a Magnesium Sulphate Environment

Keywords: Self-consolidating concrete, mineral admixture, natural pozzolan, fly ash, limestone filler, magnesium sulphate attack

The effects of mineral admixture type on the behaviour of self-consolidating concrete (SCC) in magnesium sulphate environments were investigated over the course of four years of exposure. Three mineral admixtures (limestone filler, fly ash and natural pozzolan) representing a wide range of compositions were used in the study. Twelve formulations covering three strength classes (30, 50 and 70 MPa) and four concrete mixtures were studied.

Mass loss with physical deterioration, and dimensional and compressive strength changes due to magnesium sulphate attack were determined through microstructural analysis. The sulphate profiles of sulphur, magnesium, silicon, calcium and aluminium elements were also quantified through analyses of the samples. A complementary analysis by phase assemblages was performed on the degraded layers of concrete specimens. These test results indicate that the mineral admixture type greatly affects the durability performance of SCC under magnesium sulphate exposure. Among the tested mineral admixtures, natural pozzolan showed better long-term durability performance in the magnesium sulphate environment. The interaction between vibrated concrete and SCC is related to the nature of the mineral admixtures.

Introduction

Self-consolidating concrete (SCC) is characterized by its ability to compact itself by means of its own weight, with little or no vibration and without segregation or bleeding. It fills all recesses, reinforcement spaces and voids, even in highly reinforced concrete members.

Recently, this type of concrete has gained wide use in many countries. Because of the advantages it offers, SCC is increasingly being used in civil engineering structures such as substructures, infrastructure and industrial floors that are regularly subjected to aggressive environmental conditions. External sulphates are highly soluble salts that are considered to be one of the major problems affecting concrete structures. The results of sulphate attack are generally related to the volume change, cracking and hence the deterioration of concrete. Magnesium sulphate (MgSO 4 ) is responsible for the fastest, most severe attacks on concrete [START_REF] Yildirim | Effects of sodium chloride and magnesium sulfate concentration on the durability of cement mortar with and without fly ash[END_REF]. According to Golop and Taylor [START_REF] Golop | Microstructural and microanalytical studies of sulfate attack, III. Sulfate resisting Portland cement: reaction with sodium and magnesium sulphate solutions[END_REF], magnesium sulphate is more severe than sodium sulphate. Their spectrum media is wide, and they usually originate from underground water, soil, seawater or industrial wastewater. The magnesium sulphate reacts with double action, with the ions SO [START_REF] Bonen | Magnesium sulfate attack on Portland cement paste -II. Chemical and mineralogical analyses[END_REF] 2-reacting with the aluminate (or portlandite) to form gypsum and ettringite. The ions Mg 2+ may react with OH -to form brucite [Mg(OH) 2 ] or cause a partial replacement of calcium by magnesium in calcium Silicate Hydrate (C-S-H). The Magnesium Silicate Hydrate (M-S-H), thus formed, has no binder properties and the hydrated paste becomes soft and incoherent [START_REF] Bonen | Magnesium sulfate attack on Portland cement paste -I. microstructural analysis[END_REF][START_REF] Bonen | Magnesium sulfate attack on Portland cement paste -II. Chemical and mineralogical analyses[END_REF].

Deterioration due to magnesium sulphate is a well-known occurrence in ordinary concrete, and there have been numerous studies conducted into its effects [START_REF] Sumer | Compressive strength and sulfate resistance properties of concretes containing Class F and Class C fly ashes[END_REF][START_REF] Shannag | Sulfate resistance of high-performance concrete[END_REF][START_REF] Jaturapitakkul | Evaluation of the sulfate resistance of concrete containing palm oil fuel ash[END_REF][START_REF] Siddique | Properties of concrete made with volcanic ash[END_REF][START_REF] Sharif | Performance of Pozzolanic Concrete Using Different Mineral Admixtures[END_REF]. However, the composition of SCC is quite different than that of ordinary concrete. The mixture design of SCC usually incorporates an efficient high-range water-reducing admixture, possibly a viscosity-modifying admixture, controlled coarse aggregate volume fraction and a large amount of mineral admixture. The influence of the nature and volume of mineral admixture content in SCC appears to be fundamental to understanding the behavior of the material in a magnesium sulphate environment. However, there is very little information in the literature on the behavior of SCC under MgSO 4 attack. Uysal and Sumer presented an experimental study on the influence of replacement of Portland cement with fly ash (FA), granulated blast furnace slag (GGBS), limestone powder (LP), basalt powder (BP) and marble powder (MP) on the magnesium sulphate attack durability of high-strength SCC [START_REF] Uysal | Performance of self-consolidating concrete containing different mineral admixtures[END_REF]. The rate of attack was evaluated by visual examination and the reduction in compressive strength of samples immersed for 400 days in 10% magnesium sulphate solution. According to the results of this study, incorporation of FA, GGBS, LP, BP and MP substantially improved the resistance of SCCs against MgSO 4 attack. In a recent publication, Hassan et al. studied the assessment of magnesium sulphate attack on SCC containing FA, rice husk ash (RHA), and GGBS, with cement replacement levels of 5 to 15% [START_REF] Hassan | Effect of Magnesium Sulphate on Self-Consolidating Concrete Containing Supplementary Cementitious Materials[END_REF]. Specimens were immersed in 5% MgSO 4 solution after seven days of curing. Compressive strength, length change, and mass loss were investigated over 118 days. Results of this study showed that adding FA, RHA, and GGBS to SCC improves its resistance to magnesium sulphate attack. These studies reveal the need for further comprehensive studies on the assessment of SCC incorporating high volumes of mineral admixtures under magnesium sulphate attack, especially for a long-term exposure period.

This paper presents a detailed mechanical, physical and microstructural study into the effects of strength class and nature of mineral admixture on the behavior of SCC in a magnesium sulphate environment. Twelve concrete mixtures with three strength classes were produced for the study. Three typical mineral admixtures (i.e., fly ash, natural pozzolan and limestone filler) were used in the production of the SCC mixtures, representing a wide range of chemical compositions. Ordinary concrete mixtures (OC) with similar strength grades were also produced for comparison purposes. The degree of magnesium sulphate attack was evaluated by visual inspection and by assessing mass change, dimensional variation and compressive strength change of concrete specimens immersed in the reference medium (fresh water) and in 5% magnesium sulphate solution for 1440 days (4 years). Microstructural changes within the different layers of degraded samples were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. Sulphate profiles were performed with backscattered electron imaging from the surface towards the core of the concrete samples, avoiding aggregates. The mechanisms of damage were studied using a microanalysis graphical treatment of the infected and uninfected zones [START_REF] Scrivener | Backscattered electron imaging of cementitious microstructures: understanding and quantification[END_REF].

Experimental program

Materials

Portland cement CEM I-52.5, complying with European Standards EN 197-01 [START_REF]European standards EN 197-1. Cement. Composition, specifications and conformity criteria for common[END_REF] (similar to ASTM C150 Type I cement [START_REF]Standard specification for Portland cement[END_REF]), was used as part of the cementitious materials in the production of SCC. Siliceous round sand with a maximum grain size of 4 mm and crushed silico-calcareous rocks with 12.5 mm maximum size were used as fine and coarse aggregates.

The specific gravity and water absorption properties of round sand and crushed rocks were 2.6% and 1.2%, and 2.66 and 0.5%, respectively. Three types of mineral admixtures were used in the SCC mixtures: a limestone filler characterized by its high degree of fineness, a natural pozzolan from a volcanic deposit site, and a silico-aluminate Class-F fly ash. The superplasticizer (SP) used was an acrylic copolymer with a density of 1.06 and chloride ion content of ≤0.1%. Table 1 describes the various physical and chemical characteristics of Portland cement and the mineral admixtures used in this study.

Mixture proportions

Four concrete recipes [ordinary concrete (OC), SCC with limestone filler (SCCLF), SCC with natural pozzolan (SCCPZ) and SCC with fly ash (SCCFA)] (12 concrete mixtures in total)

were prepared, covering three strength classes (30 MPa, 50 MPa, and >70 MPa). All of the various data related to the materials were taken into account for determining the SCC mix design using Bétonlab-Pro software [START_REF] Sedran | BetonlabPro 2, ComputerAided MixDesign Software[END_REF]. Bétonlab-Pro combines several behavioural models calibrated from a wide range of concrete types, with the granular structure described by the compressible stacking model.

A fixed amount of binder (cement + mineral admixtures) equal to 520 kg/m 3 was selected. In each strength class, the concretes were formulated from the same components, with the same granular skeleton and constant water to binder (W/B) ratio. A comparison was then carried out using the same mechanical strength. The amount of superplasticizer was selected to obtain a slump flow as close to 670 ± 20 mm as possible for all SCC mixtures. In order to get the same strength classes as the SCC, the OC formulation was realised using the Dreux-Gorisse method [START_REF] Dreux | Nouveau guide du béton[END_REF]. Table 2 gives the mixture proportions of the concretes investigated. As seen in the table, the mixtures are labeled based on their ingredients; for example, mixture SCC70LF had a compressive strength class of 70 MPa and contained limestone filler.

Specimen preparation and testing

Compressive strength and mass changes before and after immersion in the magnesium sulphate solution were monitored on 10×10×10 cm concrete cube specimens. Prismatic specimens with 7×7×28 cm dimensions were prepared to determine expansion amount after immersion. All specimens were demoulded after 24 hours and cured in a controlled chamber at 20 °C and 95% relative humidity.

Slump-flow, L-box, V-funnel and air content tests were conducted in the fresh state to determine the properties of SCC in accordance with the tests recommended by the AFGC [START_REF]Interim recommendations for use of selfconsolidating concrete[END_REF]. In the hardened state, after 28 days of curing, the initial mass, compressive strength and length of the specimens were determined before immersion in the sulphate solution. Two mediums were used for immersion: a fresh water tank (reference medium) and a water tank containing 5% magnesium sulphate solution. The temperature of the solution was maintained at 22±2 °C. The testing procedure was conducted according to the ASTM C1012-04 [START_REF]Standard test method for length change of hydraulic-cement mortars exposed to a sulfate solution[END_REF] and the method outlined by Mehta [START_REF] Mehta | Evaluation of sulfate resisting cements by a new test method[END_REF]. The pH of the sulphate solution was maintained within a range of 6.0-8.0 by adding a suitable amount of sulphuric acid solution (0.1 N H 2 SO 4 ). In addition, the aggressive solutions were totally renewed every eight weeks.

Samples were immersed for four years in the magnesium sulphate and fresh water solutions.

To evaluate the effect of the various mineral admixtures on the durability of SCC exposed to magnesium sulphate solution, visual (photos), mechanical (compressive strength), physical (change of mass and length), and mineralogical (XRD) investigations were performed.

Chemical and microstructural studies were also carried out using SEM coupled to EDS and microanalyses of polished surfaces.

Experimental results

Concrete properties in fresh state and compressive strength before immersion

Table 3 presents the workability and basic mechanical properties of twelve SCC mixtures.

The results of the SCC mixtures listed in Table 3 can be interpreted according to the limits of the standard for SCC tests recommended by the AFGC [START_REF]Interim recommendations for use of selfconsolidating concrete[END_REF]. The SCC mixtures had good filling ability with a slump-flow equal to 670±20 mm and V-funnel flow times between 5.8 and 7 seconds. All SCC mixtures showed acceptable passing ability based on L-box and fillbox results, which ranged between 0.80 and 0.90 and 79% and 96.2%, respectively.

When seven-day compressive strength test results were compared, a significant difference between SCCLF and other concretes was observed. The improved strength of SCCLF at an early age can be attributed to the formation of calcium carboaluminates hydrate, which led to a decrease in the total porosity and accelerated the hydration rate of the cement paste [START_REF] Bonavetti | Studies on the carboaluminate formation in limestone filler-blended cements[END_REF].

From the 28-day test results, the compressive strength values were closer to the targeted strength classes (30, 50 and 70 MPa), a result that confirms the reliability of the method used on the design of the different mixtures.

Magnesium sulphate attack

Change of mass

Mass change results for specimens immersed in 5% magnesium sulphate solutions are shown in Figure 1. As seen in Figure 1, there is a positive trend in the mass change for all the concrete mixtures of 70 MPa class. The mass gain can be attributed to water filling cracks, and to the mass of water used to precipitate the hydrated phase as ettringite [START_REF] Khelifa | Consequences mecaniques de l'attaque sulfatique externe sur les betons autoplaçants[END_REF].

For the 50 and 30 MPa classes (with the exception of OC50 and OC30), a mass loss for SCC with different mineral admixtures was observed after four years of tests. When comparing SCCs of the same strength class at up to 720 days of immersion, unlike SCCPZ and SCCFA, the SCCLF mixtures did not show mass loss. At four years of immersion, the SCCLF presented the largest mass loss, especially in the 30 MPa classes, with a difference of around 12% compared to SCC30PZ and SCC30FA. The mass loss difference between SCCPZ and SCCFA was small (<1%) for both 50 and 30 MPa strength classes.

The ordinary concrete results showed better physical resistance against magnesium sulphate attack compared with SCC formulations with different mineral admixtures. During all the immersion times, no mass loss occurred for ordinary concrete formulations.

A visual inspection was carried out after four years of immersion in 5% MgSO 4 solution (Figures 234) to determine the state of the different samples. Obvious signs of degradation were observed in all specimens, with extensive spalling and cracking on surfaces. The most significant signs of degradation were observed in the SCC specimens, particularly those in 50 and 30 MPa strength classes. The degree of deterioration in SCC30LF appeared to be highest, with greater physical expansion, a significant amount of spalling and cracking at corners and edges, and a remarkable loss of shape. Severe exterior damage was recorded in both SCC30FA and SCC30PZ. These concretes more or less kept their form, however their dimensions decreased considerably, with clearly deteriorated layers in exposed surfaces. For example, SCC30FA lost 4-6 mm on all sides and SCC30PZ lost 2-4 mm. Ordinary concrete samples underwent minimal change, mainly on the sides and the external surfaces.

Dimensional variation

The length change of the samples immersed in magnesium sulphate solution is shown in value of water-binder ratio and the cement content in the concretes of this class. Indeed, according to Maltais [START_REF] Maltais | Predicting the durability of Portland cement systems in aggressive environments -laboratory validation[END_REF], a reduction of w/c contributes to decrease the transport properties of the material and therefore limit the extent of degradation. Neville [START_REF] Neville | The confused world of sulfate attack on concrete[END_REF] added that, in high performance concrete there is limited pore space to accommodate the products of reactions with sulfate, namely, magnesium silicate hydrate and gypsum partly responsible on the expansion.

As can be seen from Figure 6, the expansion was registered starting from 560, 880 and 1320 days for OC50, SCC50LF and SCC50FA, respectively. At four years, expansion values of 1600 µm/m, 5085 µm/m, and 28 µm/m were measured respectively for OC50, for SCC50LF and for SCC50FA. The expansion of OC50 was registered early than SCC50LF, however after four yours of immersion, the SCC50LF showed three times higher expansion than OC50. The same result was recorded for the 30 MPa strength class concretes.

From the results of Figure 7, we can observe the continuous increase of expansion, especially for OC30 and SCC30LF with 2100 µm/m and 7870 µm/m, respectively. The expansion was recorded starting from 520 days for OC30 and from 630 days for SCC30LF. The expansion of SCC30PZ and SCC30FA was measured starting between 1250 and 1290 days of immersion, with resulting values of 143 µm/m and 123 µm/m, respectively. These observations emphasize that when SCC is exposed to magnesium sulphate attack, mixtures with limestone filler showed earlier and higher expansion than those containing natural pozzolan or fly ash.

The expansion values of SCCPZ and SCCFA mixtures were negligible compared with those of the SCCLF mixtures.

By comparison between SCC and OC mixtures, the SCC prepared with natural pozzolan or fly ash consistently presented lower expansion than the OC. After four years of immersion, SCC incorporating limestone filler showed higher expansion. It is interesting to note that the expansion of OC mixtures occurred earlier than it did in SCCLF. However, after the four-year period, OC expansion was lower.

Change of compressive strength

The compressive strength change illustrated by the results of the control medium (fresh water) If we consider that the reference corresponds to the initial values before immersion, it is clear that for 70 MPa (Figure 8) and 50MPa classes (Figure 9), slight reductions in compressive strength values occurred after 1440 days (-4.4 MPa for SCC70LF, -6.1 MPa for OC50, -8.9

MPa for SCC50LF, -5.3 MPa for SCC50PZ and -5.2 MPa for SCC50FA). For the 30 MPa class, the loss of strength was recorded starting at 90 days of immersion for OC30 (-20.7 MPa after 1440 days) and SCC30LF (complete deterioration at 1440 days). Late age strength loss was observed after 1440 days for SCC30PZ (-20.9 MPa) and SCC30FA (-21.5 MPa). In general, SCCPZ and SCCFA showed late loss of compressive strength compared with SCCLF or OC in the same compressive strength class. At four years of immersion, they showed almost the same values as OC. The SCCLF mixtures showed higher loss in compressive strength than the other concretes.

Microstructural observations

Specimens of the 30 MPa concrete classes were examined by XRD after four years of immersion in magnesium sulphate solution. Measurements were performed starting at the surface layer (0 cm) and moving towards the interior (0.8-1.0, 1.8-2.0, 2.-3.0 cm). Figure 11 presents the XRD spectra at different layers for each type of concrete. Patterns were obtained using an X-ray diffractometer with Cu Kα radiation and 2θ scanning, ranging between 5° and 80° of 2θ.

The superposition of the spectra of different layers confirmed the presence of strong intensity peaks for gypsum formation at around 11.7 and 29.15° 2θ for all concrete mixtures. Relatively strong peaks of ettringite were also detected on the surface layer of all concretes exposed to magnesium sulphate attack, especially at around 33.4 and 43.8° 2θ. In spite of the similarities between thaumasite and ettringite at around 9.1 and 16° 2θ, the XRD patterns confirmed the presence of thaumasite in the surface layer of OC30 and SCC30LF. Based on the peaks observed at 19.3 and 23.35° 2θ, the thaumasite peaks were very intense in SCC30LF compared with OC30 samples. It should be noted that the thaumasite was detected in the concrete specimens exposed to magnesium sulphate attack in a temperature maintained at 22±2 °C. Previous studies have also reported the formation of small quantities of thaumasite (in pastes and mortars), even at room temperature [START_REF] Lee | Effect of limestone filler on the deterioration of mortars and pastes exposed to sulfate solutions at ambient temperature[END_REF][START_REF] Skaropoulou | Use of mineral admixtures to improve the resistance of limestone cement concrete against thaumasite form of sulfate attack[END_REF]. Contrary to the OC30 and SCC30LF results, no trace of thaumasite was observed in SCC30PZ and SCC30FA. In comparing the data of each layer, the absence or negligible level of gypsum is notable in the 0.8 cm layer in all concrete mixtures. Ettringite was present in the other layers (0.8-1.0 cm, 0.8-2.0 cm, 0.8-3.0 cm) up to the core of specimens, but with fewer peaks, especially in SCC30PZ. The XRD results showed the presence of portlandite at around 18.1 and 34.1° 2θ, from 1.8 cm depth for OC30, from 0.8 cm depth for SCC30LF and from the 1.8-2 cm layer for SCC30PZ and SCC30FA. The portlandite was weak due to the significant consumption of calcium hydroxide in the magnesium sulphate reaction for OC and SCC30LF, and both pozzolanic and sulphate reaction in SCC30PZ and SCC30FA. There was no detectable trace of portlandite in the surface of all concrete samples, which indicates total leaching at this phase.

A small amount of brucite [Mg(OH 2 )] at around 37.95° 2θ was evident in the surface layers of OC and SCC30LF. The peak due to brucite was always very weak in the surface layer of SCC30PZ and SCC30FA. The very low solubility of brucite favours the consumption of calcium hydroxide [START_REF] Skaropoulou | Use of mineral admixtures to improve the resistance of limestone cement concrete against thaumasite form of sulfate attack[END_REF], which is related to the XRD peaks of portlandite.

SEM-EDS analyses were conducted to qualitatively investigate the hydrate phases formed by sulphate attack. Figure 12 shows SEM micrographs of examined samples after four years of immersion in a 5% magnesium sulphate solution. The micrographs (Figure 12 a-f) are taken from areas close to the surface layers of the samples. SEM observations of different degraded areas confirmed the presence of significant amounts of ettringite (Figure 12a and12c) and gypsum (Figure 12b), as also noticed in XRD results.

EDS analysis of Figure 12d (OC30 sample) indicated that the crystals consisted mainly of Ca, S, Si and C. Although there was a small amount of Al in the spectra, the product appeared to be thaumasite, because Al is replaced by Si in the thaumasite crystal structure [START_REF] Tosun | Effects of limestone replacement ratio on the sulfate resistance of Portland limestone cement mortars exposed to extraordinary high sulfate concentrations[END_REF]. The presence of thaumasite in the surface layer of OC30 appeared in the areas with a large amount of ettringite. This observation is an agreement with the results of KÖhler et al. [START_REF] Köhler | Effect of ettringite on thaumasite formation[END_REF], who reported that the presence of thaumasite is often preceded by the formation of ettringite, which considerably controls the rate of thaumasite formation. Figure 12e, which shows the SEM-EDS of SCC30LF, confirms the presence of the double layer consisting of brucite and gypsum. The presence of M-C-S-H (or Mg rich C-S-H) due to the magnesium sulphate attack was noticed through the EDS analysis of SCC30FA (Figure 12f). The M-C-S-H product was not detected by XRD because of its poor crystallinity.

Penetration depth of degradation

Sulphate profiles were performed from the surface to the core of each concrete sample, avoiding aggregates. Figure 13 presents the sulphate profile of the samples after four years of immersion in 5% MgSO 4 . The variations of sulphur, magnesium, silicon, calcium and aluminium are presented to help understand the role of different mineral admixtures in the mechanism of degradation of OC and SCC mixtures. The results show that for OC30, the profile of Mg presents a maximum density at a very small surface region, presented at the approximate depth of 0.2 mm of brucite. The passage from the brucite to the gypsum was detected due to a maximum amount of sulphur of about 14% and a depth of 18 mm. The gypsum amount decreased with depth, with a decrease in the peak of sulphur associated with increased calcium content and uniform concentration of silicon. The aluminium showed irregular concentration with a different maximum peak of ettringite, especially during the first 13 mm. An increase in silicon was noted at around 14 mm, and a similar concentration was maintained at 18 mm throughout the sample. The stabilisation in silicon concentration after increase, which is associated with the maximum amount of calcium at 18 mm depth, shows the presence of great amount of C-S-H, indicating the beginning of the safe area.

For SCC30LF, the presence of brucite in a slight exterior layer was indicated by a maximum peak of magnesium and a lower concentration of sulphur, silicon, and calcium. After reaching a depth of 0.2 mm, the Mg contents dropped to the minimum throughout the rest of the specimen. The high levels of sulphur (about 10%) revealed the presence of the surface double layer, followed by gypsum at a depth of 9 mm. The decrease in sulphur by depth was associated with a decrease in calcium, and a stable amount of silicon indicated decreased gypsum concentration. Ettringite was revealed throughout the specimen by a maximum concentration of aluminium, especially at a 14 mm depth. The zone unaffected by the external solution was noticed from a 9 mm depth, and was characterised by the maximum amount of silicon and calcium.

Like the OC30 and SCC30LF specimens, SCC30PZ showed a maximum peak of magnesium in the surface layer, indicating brucite at a depth of 0.4 mm. However, other peaks of magnesium were detected across the specimen, a result that corresponds to brucite being dispersed throughout the concrete. The sulphur patterns displayed a maximum concentration of about 4% and a depth of around 7.5 mm, which indicated the presence of gypsum. With the exception of the low concentration of silicon in the first 2 mm, the decrease in the sulphur patterns was accompanied by fluctuating peaks of silicon and calcium, with a small increase at 7 mm. This explains the presence of an infected layer, as indicated by decalcification of the C-S-H, as well as the presence of gypsum. A maximum concentration of aluminium was noted at around 2 mm, accompanied by changes in sulphur and calcium, indicating the presence of a small amount of ettringite next to the gypsum.

The sulphate profile of SCC30FA was also started at the brucite cover, and was characterised by a maximum peak of magnesium. The significant breadth of the magnesium peak at a 2 mm depth was associated with a low concentration of calcite and aluminium. However, the sulphur initially presented a low value (at 0.4 mm depth), followed by a maximum peak through the rest of the 2 mm depth, as shown in the case of magnesium. The silicon also showed a low concentration in the exterior surface, increasing after 1 mm depth, with maximum peak at around 2 mm. These changes indicated the major deterioration area with an evident brucite cover (around 0.4 mm) followed by an M-S-H layer interblended by gypsumettringite. The relatively high concentration of sulphur decreased with depth, stabilizing at a low value after about 7 mm into the specimen. This decrease was associated with a stable concentration of silicon. The line profile for Ca fluctuated but increased at a low rate toward the interior of the bar. Calcium increased at a low rate toward the 7 mm depth, indicating that the zone was affected by decalcification of the C-S-H.

A complementary analysis of the microstructure was performed on the degraded layers (0-7 mm zone for SCC30PZ and SCC30FA, 0-18 mm zone for OC30 and 0-9 mm for SCC30LF).

Figure 15 presents the changes in the phase assemblage across the samples of the element ratios S/Ca as a function of Al/Ca. The plots of S/Ca vs. Al/Ca (Figure 14) suggest that the S/Ca and Al/Ca ratios of 1 and 0, respectively, correspond to gypsum. The ettringite phase has S/Ca = 0.5 and Al/Ca = 0.33, monosulphoaluminate has S/Ca = 0.25 and Al/Ca = 0.5.

The microanalyses of the degraded layers of concrete samples confirmed the results of the sulphate profile. Figure 14 shows the presence of an important amount of the C-S-H phase partly intermixed with ettringite in SCC30LF and OC30. The C-S-H phase was rarely seen in the degraded zones of SCC30PZ and SCC30FA. A small concentration of ettringite was noted in SCC30PZ, but no trace of this element was found in the phase assemblage of SCC30FA.

Gypsum was identified in OC30 and seemed to appear in smaller amounts in the SCC30LF mixture. Contrary to the sulphate profile results, the SCC30PZ and SCC30FA analyses showed an absence of gypsum in the degraded layer. Portlandite was detectable in the SCC30LF concrete, but not in OC30, SCC30PZ and SCC30FA; these results were in agreement with those of the XRD analysis. Higher amounts of monosulphoaluminate were detected in SCC30PZ and SCC30FA, which is partly attributable to the high percentage of alumina in the chemical composition of natural pozzolan and fly ash. It can also be attributed to the fact that the monosulphoaluminate in these two concrete specimens had not yet transformed into ettringite. According to Schmidt [START_REF] Schmidt | Sulfate Attack and the Role of Internal Carbonate on the Formation of Thaumasite[END_REF], ettringite is formed by a reaction between sulphate ions and aluminates (sulphoaluminate or carboaluminate). When the reserve in aluminate is exhausted, ettringite crystallization stops and sulphate ions react with calcium ions to form gypsum.

Summary and discussion

A comparison of the results of different compressive strength classes showed increased mass loss, expansion and compressive strength loss from the higher to the lower strength classes.

The lower compressive strength concretes (30 MPa) showed weaker performance against magnesium sulphate attack. Indeed, according to Siad et al. [START_REF] Siad | Characterization of the degradation of self-consolidating concretes in sodium sulfate environment: Influence of different mineral admixtures[END_REF] and Guillon et al. [START_REF] Guillon | Characterization of the mechanical damage of a chemically degraded cement paste[END_REF], the volume and connectivity of the porous network decrease when the water/binder ratio decreases, therefore making the penetration of aggressive agents more difficult.

The difference between the results obtained for SCC and OC relates to the time of exposure and the nature of the mineral admixture. During more than three years of immersion, the OC mixtures showed greater expansion and compressive strength loss. The early compressive strength loss in OC mixtures is correlated with the major diffusion of sulphur through the concrete, leading to a maximum amount of gypsum manifested by early expansion. The lower physical damage of OC specimens after four years of immersion may be related to the gradual expansion, with a gradual reduction in the cohesiveness of the hydrated cement paste. This conclusion is supported by the presence of significant amounts of C-S-H, even in the infected exterior layer showed beyond the brucite film.

The positive behaviour of SCC mixtures in the early state of immersion can be attributed to the denser matrix of these concretes compared with OC. The large amounts of natural pozzolan, fly ash and limestone filler in SCC paste promoted a denser microstructure, which contributed to decreased diffusion of aggressive ions like magnesium sulphate ions [START_REF] Siad | Influence du type d'addition minérale sur le comportement physicomécanique et sur la durabilité des bétons autoplaçants[END_REF].

Indeed, according to Bonen and Cohen [START_REF] Bonen | Magnesium sulfate attack on Portland cement paste -I. microstructural analysis[END_REF][START_REF] Bonen | Magnesium sulfate attack on Portland cement paste -II. Chemical and mineralogical analyses[END_REF], magnesium sulphate attack has a progressive diffusion process in Portland cement paste involving several stages including the conversion of portlandite to brucite and gypsum, the conversion of C 3 A, hydrated calcium aluminate, and monosulphate to secondary ettringite, and the decalcification of C-S-H to form M-S-H.

By comparing concretes of the same strength class, the results showed that the SCCLF experienced greater mass loss, visual damage, expansion and compressive strength loss.

SCCPZ and SCCFA results showed lower (or absent) expansion, accompanied by significant mass loss, physical damage and compressive strength loss. The low resistance of SCCLF formulations against MgSO 4 attack is consistent with the results of Seung et al. [START_REF] Tae | Effect of limestone filler on the deterioration of mortars and pastes exposed to sulfate solutions at ambient temperature[END_REF] and Tosun et al. [START_REF] Tosun | Effects of limestone replacement ratio on the sulfate resistance of Portland limestone cement mortars exposed to extraordinary high sulfate concentrations[END_REF], who observed that high limestone replacement rates negatively affect the sulphate resistance of cement mortars. It is important to note the evolution of results by time;

the lower performances of SCCLF were recorded extremely late. A good correlation between expansion results, mass loss, physical damage and compressive strength loss was clear in the case of SCCLF. According to Liu et al. [START_REF] Liu | Effect of Limestone Powder and Fly Ash on Magnesium Sulfate Resistance of Mortar[END_REF], the expansion of mortar destroys the microstructure and causes a progressive loss of strength and mass. The most probable cause of the large expansion in SCCLF mixtures was the presence of gypsum and especially thaumasite after long-term exposure to MgSO 4 . In spite of the presence of thaumasite in the OC mixtures, XRD analysis showed very intense thaumasite peaks in SCC30LF. Also, the carbonate sources and the calcite available in the case of SCCLF suggested a higher thaumasite component. Schmidt [START_REF] Schmidt | Sulfate Attack and the Role of Internal Carbonate on the Formation of Thaumasite[END_REF] reported that the amount of thaumasite formed during sulphate interaction significantly influences the damage of the concrete structure, and concluded that small amounts of thaumasite observed in pores or cracks have no significant impact on strength loss.

In case of SCCFA and SCCPZ, the microstructure study indicated that the brucite layer in SCCPZ and SCCFA was two times thicker than in the SCCLF and OC specimens. Brucite formation on the specimen faces and the denser microstructure promoted by the pozzolanic reaction protected the samples from penetration of magnesium sulphate ions [START_REF] Biricik | Resistance to magnesium sulfate and sodium sulfate attack of mortars containing wheat straw ash[END_REF], slowing the damage process of natural pozzolan and fly ash SCC mixtures. After long-term immersion, the mass loss of the SCCPZ and SCCFA mixtures was correlated with physical damage and compressive strength loss. However, it was observed that the lower values of expansion did not correlate with the important physical damage. Moreover, the microstructure study of SCCFA and SCCPZ showed the presence of areas affected by the decalcification of C-S-H just under the brucite layer, especially in the interfacial transition zone around the aggregate.

This suggests that, after a long period of time, the magnesium solution penetrated through the damaged interfacial transition zone (ITZ) in the external layer causes the decrease in dimensions by surface loss. This conclusion is also supported by the deterioration method of SCCPZ and SCCFA samples viewed by visual inspection and SEM profile images. Visual damage showed starting at the exterior and progressing into the disintegration of aggregate and leaching of the paste. The SEM profile images showed several lines of rich magnesium along the exterior damaged layer. This conclusion is consistent with the results of Kunther et al. [START_REF] Kunther | Deterioration of mortar bars immersed in magnesium containing sulfate solutions[END_REF], who worked on a comparison between CEMI and CEMIIII/B cement mortar bars immersed in magnesium sulphate solution. They found that for CEMI III binder, surface erosion of mortar specimens is the dominant deterioration mechanism.

In the microstructure study, the presence of a large amount of monosulphoaluminate corresponded to the absence of portlandite, the low concentration of ettringite, and the rare C-S-H phase in the infected layers of SCCPZ and SCCFA. According to Schmidt [START_REF] Schmidt | Sulfate Attack and the Role of Internal Carbonate on the Formation of Thaumasite[END_REF] the participation of portlandite is the one possible cause of ettringite formation from monosulphate during sulphate attack. Hossain and Lachemi [START_REF] Hossain | Performance of volcanic ash and pumice based blended cement concrete in mixed sulfate environment[END_REF] added that the consumption of Ca(OH) 2 by the pozzolanic reaction causes Mg 2+ actions to react directly with the C-S-H 20 gel, converting it to M-S-H. This is also in agreement with the presence of M-S-H directly under the brucite layer in the sulphate profile of SCCPZ and SCCFA samples.

Conclusions

This paper aims to contribute to a better understanding of the effects of the nature of mineral admixtures on the behaviour of SCC mixtures in magnesium sulphate environments for an immersion period of four years by evaluating mechanical, physical, chemical, mineralogical and microstructural deterioration of concrete samples. Three strength classes (30 MPa,50 MPa and 70 MPa) and three mineral admixtures (limestone filler, fly ash and natural pozzolan) were studied. The following conclusions were drawn from the study:

1. Physical damage, expansion and compressive strength loss due to Mg 2 SO 4 attack, increased from the higher to the lower strength classes of concretes. SCC mixtures containing limestone filler presented the highest physical deterioration, especially in the 30 MPa class, with 18% mass loss. The 30 MPa classes of SCC with natural pozzolan and fly ash also showed remarkable deteriorated surfaces, with mass loss ranged between 4 and 5%. No mass loss was recorded for the ordinary concrete mixtures.

2. After four years of exposure to magnesium sulphate solution, the SCC with limestone presented a very advanced expansion, especially for concretes in the 30 MPa strength class, with values (7870 µm/m) too higher than in the OC mixtures (2100 µm/m).

Minor expansion was recorded for all SCCs containing fly ash or natural pozzolan with 143 µm/m and 123 µm/m, respectively.

3. All concrete formulations showed a decrease in compressive strength, especially for 30 MPa strength classes with loss of 20.7 MPa for OC30, 20.9 MPa for SCC30PZ and 21.5 MPa for SCC30FA. The greatest loss was observed in the SCCLF formulations, with complete deterioration of SCC30LF.

4. A good correlation between mass loss, physical damage, expansion, and compressive strength loss results were found in the case of SCCLF. Expansion of SCCLF due to the presence of gypsum and thaumasite after long-term exposure to MgSO 4 was the most probable cause of the sample weakness. For SCCPZ and SCCFA mixtures, the mass loss was linked to the physical damage and compressive strength loss; however, the results of expansion with lower values did not correlate with the important physical damage. Severe exterior deterioration of SCCPZ and SCCFA was observed due to surface erosion.

5. Microstructure analysis using SEM-EDS and XRD showed significant changes in the degraded zone. Formation of gypsum and ettringite was found in different amounts in all concrete mixtures. The formation of thaumasite was detectable in OC and occurred in higher amounts in SCCLF mixtures. Higher C-S-H decalcification occurred in SCCPZ and even more so in SCCFA.

6. The results of the sulphate profile, which used SEM-EDS to determine variations of sulphur, magnesium, silicon, calcium and aluminium in concrete samples, were consistent with those of the XRD analysis. After four years of immersion in 5% MgSO 4 solution, the expansion of OC mixtures depended on the amount of gypsum and ettringite, the degradation of SCCLF was related to the amount of thaumasite, and the deterioration of SCC containing natural pozzolan or fly ash was based on the amount of C-S-H replaced by M-S-H in advanced stages of immersion.

Figures 5 - 7 .

 57 Figures5-7. The reference corresponds to the initial length just before immersion. Because

(

  C) and the magnesium sulphate (Mg) solution is shown in Figures 8-10. The four years compressive strength of SCC30LF was not measured because of the severe deterioration of samples in 5% MgSO 4 .As shown in Figures8-10, compressive strength development was clearly influenced by the magnesium sulphate solution. There was a continuous increase in the compressive strength of specimens stored in fresh water versus a large decrease recorded for those stored in magnesium solution. This decrease was more marked for the 30 MPa strength class, especially between 360 and 1440 days of immersion.