Optimization of magnesium oxychloride cement formation using experimental design methodology

Transcription

1 114 Journal of the Tunisian Cheical Society, 016, 18, Optiization of agnesiu oxychloride ceent foration using experiental design ethodology Aal Brichni a,b, Hali Hai a, Salia Aggoun c, Adel Mnif a a) Useful Material valorization laboratory, National Center for Research in Materials Sciences, Technopole Borj Cedria, BP73, 807 Solian-Tunisia; b) Université de Tunis El Manar, Faculté des Sciences de Tunis, 09, Tunis, Tunisie. c) University of Cergy-Pontoise (LMGC), 5 Mail Gay-Lussac, Neuville Sur Oise, Cergy-Pontoise Cedex, France; (Received : 17 February 016, accepted: April 016) Abstract: In this work, the experiental design ethodology is applied to optiize the condition of foration of Magnesiu chloride ceent. A four factors factorial design to odel and to optiize the operating paraeters that govern the foration was used. The studied factors were ass ratio of MgCl.6H O/MgO, ixing tie and stirring speed. Considered responses are copressive strength and setting tie. The optiu operating conditions were quite efficient to have a good copressive strength and suitable setting tie. The phases copositions of agnesiu oxychloride ceent were evaluated by X-ray diffraction, the orphological properties were exained by SEM and their theral behaviour was analyzed by DTA/TGA. The presence of phase 5 confirs the good copressive strength of agnesiu oxychloride ceent. Keywords: Magnesiu oxychloride ceent, Experiental design ethodology, Optiization. INTRODUCTION Magnesiu chloride ceent (MOC) has superiors properties as copared to ordinary Portland ceent such as high copressive strength [1], good resistance to abrasion, rapid hardening rate, good cohesiveness, high fire resistance [] and it can be use with all kinds of aggregates [3]. The ain used applications are architectural such as construction of industrial floors, construction of theral and acoustical insulating panels [4] and other prefabricated building boards [5]. The basic cheical reaction syste of MOC syste is MgO MgCl H O [6-7]. The ain bonding phases found in hardened MOC are 5Mg(OH).MgCl.8H O (phase5) and 3Mg(OH).MgCl.8H O (phase 3) which are obtained by the following cheical reactions[7]: 5MgO + MgCl + 13 H O = 5Mg (OH). MgCl + 8 H O (1) 3MgO + MgCl + 11 H O = 3Mg (OH). MgCl + 8 H O () They are the only stable phases in the syste MgO-MgCl -H O. Due to the presence of excess water a parallel or copetitive reaction, corresponding to the agnesiu oxide hydration can take place: MgO+ H O = Mg(OH) (3) The presence of Mg(OH) indicates the low quality of the agnesiu oxychloride ceent. Furtherore, the widespread use of agnesiu oxychloride ceent has been liited because of loss of strength on prolonged excessive exposure to water [8]. Much research has long been processed to iprove the water-resistance of agnesiu oxychloride based on his ability to the binding of various organic and inorganic aggregates such as high active SiO [9-10], active aluinates [1] sulfates and phosphoric acid or phosphate [1]. In this work, the influence of three factors (ass ratio of MgCl /MgO, ixing tie and * Corresponding author, e-ail address : aal.brichni@gail.co, halihai015@gail.co, salia.aggoun@u-cergy.fr, nifinrst@gail.co

2 Aal Brichni and al., Journal Tun. Che. Soc., 016, 18, Table I: Cheical copositions of the used raw aterials MgO Coponent MgO ClO SO 4 CaO Mass fraction (%) Heavy etal (as Pb) Fe O 3 CuO Coponent MgCl.6H O SO 4 As O 3 CaCl Fe O 3 K O NaCl MgCl.6H O Mass fraction (%) stirring speed) on copressive strength and setting tie of MOC was carried out. The application of the experiental design ethodology was used in order to axiize synthesis yield by searching for the optiu experiental conditions in a less nuber of experients. MATERIAL AND EXPERIMENTAL PROCEDURE 1. Materials The raw aterials used in the study were agnesiu oxide and agnesiu chloride hexahydrate. The agnesiu oxide was produced by HIMEDIA (Laboratories in India) and agnesiu chloride hexahydrate was produced by Scharlab in Spain. The cheical copositions of the raw aterials are listed in table I.. Preparation of agnesiu chloride solution: Saturated Magnesiu chloride solution was prepared by dissolving the agnesiu chloride hexahydrate into distilled water before ixing with agnesiu oxide powder to produce MOC ceent paste. The ass concentration of the solution is 17 g for 100 g of water. 3. Preparation of speciens Magnesiu oxide powder was ixed with agnesiu chloride solution echanically using a ixer (Heidolph RZR) to for hoogenous MOC pastes. The weight of MgO is fixed and the weight of MgCl.6H O has been varied. Mixtures were cast in cylindrical olds (6 in diaeter, 50 high) and stored for 4 h, then unolded and air-cured for 8 days. 4. Measureents The XRD analyzed was carried out on the powdered saple using X-Ray powder diffractoeter (XRD PHILIPS) with Cu K radiation (λ K=1.54Å). Differential therogras were obtained using the Netzsch 449 STA F1 Jupiter theral analys syste. The rate of heating was 15 C / in. The icrostructure of the saples was exained using scanning electron icroscope Carl ZEIIS LEICA S430i odel. Measureent of theral conductivity was perfored in dry state using Phototheral Deflection Technique. Setting tie was deterined by using Vicat Apparatus. Porosity accessible to water of MOC is deterined according to EN nor. The easureent of porosity in the water under a vacuu of 0.1 bar, quantify the volue of open pores (accessible to water) using the following protocol: Ceent saples are placed in sealed desiccators and kept under Vacuu of 0.1 bar for 1 h. Previously degassed water is introduced progressively in desiccators to fill all the pores of saples, without introducing air bubbles. Once the saples are saturated, they kept iersed in water for 4 hours, and finally we i deterined hydrostatic ass and saturated dry surface ass ss. The porosity is calculated by the following equation (4): dry i With: : saturated dry surface ass of saple dry : ass of saple before saturation i : ass of saple easured in water

3 116 Aal Brichni and al., Journal Tun. Che. Soc., 016, 18, Table II: Experiental factors and levels investigated Levels Mass ratio of MgCl /MgO Speed tie (rp) Mixing tie (in) RESULTS AND DISCUSSION 1. Studied factors and experiental doains According to the preparation of MOC, 3 quantitative factors are chosen: ass ratio of MgCl /MgO, stirring speed and ixing tie. The corresponding variables and their levels (set according to the data of preliinary experients and the equipent abilities) are given in Table II. The two experiental responses tracked were copressive strength (Y 1 ) and the setting tie (Y ). We should ention that we fixed H O\MgO ass ratio for each level. To test the direct influence of the three studied factors as well as their possible interaction effects on the easured experiental responses, we have realized a two-level coplete factorial design 3 which is expected to provide excellent inforation concerning not only the ain effects but also the double interaction effects. The experiental design and the easured responses are suarized in Table IV. Coparing MOC and Portland ceent (setting tie between h and 3h), it is found that MOC has a faster setting. It also has better echanical strength. For a very short setting tie (6 in), MOC have a high strength (75.48 MPa): in this case the ceent is recoended for applications that require fast setting (decoration use, restoration of onuents, daaged arble...). For a longer setting tie (64 in), also it has a good echanical strength (46.59 MPa): in this case the ceent is recoended for applications which require a longer setting tie (floor covering...). Considering that the interaction effects between three or ore factors are negligible, the factor effect estiation is coputed [13] according to [14]: N Y j j bi N (5) Where b i is the effect estiation of the factor i, Y j is the response j and N is the nuber of experiences. The pooled variance estiation used to deterine the significant factors is coputed as n isi i S a n (6) Where S a is the pooled experiental variance, S i is the experiental variance estiation i, ν i is the degree of freedo i and n= i is the degree of freedo of the pooled experiental variance.. Identification of the influential factors Based on check student for an error risk α=5%, it was found that t tabulated = Table V suarizes the factors effects estiation for the two responses: copressive strength (Y 1 ) and setting tie (Y ). Table III: The ass ratio of H O\MgO Levels H O\MgO

4 Aal Brichni and al., Journal Tun. Che. Soc., 016, 18, Table IV: Factorial atrix 3. No. Exp. Mass ratio of MgCl /MgO Mixing tie (in) Stirring speed (rp) Copressive strength (MPa) Setting tie (in) Table V: Factors signification for the two responses Y 1 and Y Coefficient Y 1 Y Value SD t.exp P Value SD t.exp P b b b b b b b b

5 118 Aal Brichni and al., Journal Tun. Che. Soc., 016, 18, ean square and and.333 as estiation of experiental variance. Thus, the values of the ratio between the lack of fit ean square and the estiation of experiental variance and for the responses Y 1 and Y are inferior to F 0. 4 F 0. tabled, and 3,, respectively. Consequently, it is possible to confir the validity of the two elaborated odels. In addition, the ratios between the regression ean square and the residual ean square for the three responses Y 1 and Y (4.638 and ) are superior to the F 0. 4 F tabled, and 5, respectively. Thus, the significant variables, applied to elaborate the three odels, have a large significance on their responses. Figure 1: Calculated versus experiental values graph (a) for copressive strength (b) for setting tie. The two odels are represented by the equations given below: Copressive strength: Y cal 1 = X X X 1 X X 1 X X 3 (7) Setting tie: Y cal = X X -5.65X X 1 X X 1 X X 3 (8) 5. Optiization For selecting the optial conditions we try to ake a coproise between the two responses to have a good copressive strength and a suitable setting tie. By erely regarding values and signs of these significant effects, we conclude that axiization of the two responses is reached for experience nuber 6 (copressive strength = MPa and setting tie = 41 in): Mass ratio of MgCl.6H O/MgO (X 1 ):. Mixing tie (X ) : 5 in Stirring speed (X 3 ) : 115 rp The phase diagra of the ternary MOC syste (MgO-MgCl -H O) [5] at abient teperature is 3. Analysis of Residue Figure 1 reveals the distribution of the calculated versus experiental values for the two responses (Y 1 and Y ). The points are alost randoly distributed about the line representing exact agreeent, providing good agreeents between experiental values and those calculated using the odel. 4. Analysis of Variance Table VI suarizes the variance analysis of the chosen responses Y 1 and Y. The ain results for Y 1 and Y are, respectively, and 1.539, as lack of fit Figure : Phase diagra of the ternary MOC syste

6 Aal Brichni and al., Journal Tun. Che. Soc., 016, 18, Table VI: Analysis of variance. Source of variation SS DF MS Ratio P Copressive strength Regression Residual Lack of fit Pure error 36, Total Setting tie Regression Residual Lack of fit Pure error Total illustrated in Figure with the coposition point of the optiu which is located near to the phase 5 responsible for the good copressive strength of the ceent. 5. Characterization Figure 3 shows the XRD pattern of MOC with optial condition. It can be found that phase 5 is present. This phase is the ajor product responsible for hardening and the strength of MOC. We easured porosity accessible to water, we founded that the total porosity of MOC is 4% which is in a good accordance with other results in literature [15]. The theral conductivity of ceent is 0.8 w/ K. The orphology of MOC is shown in Figure 4. We can see a rough surface with a dense network of needle-like crystals of 500 n which has a high strength (Phase 5). Theral analysis of MOC is shown in Figure 5. Six endotheric events appear on the DTA curves of MOC during heating. Theral decoposition requires a dehydration stage of crystalline phase 5 Mg(OH) MgCl.8H O at 179 C to obtain an anhydrous aterials. The other deflections in this curve at 358 C, 414 C, 484 C and 711 C present the decoposition stage Figure3: XRD patterns of MOC Figure 4: SEM analysis of MOC

7 10 Aal Brichni and al., Journal Tun. Che. Soc., 016, 18, Figure 5: TG and DTA curves of MOC of 5 Mg(OH) MgCl and the loss of MgCl. The last deflection at 1100 C represents the decoposition to obtain the final solid product MgO. CONCLUSION The foration of MOC was carried out in this study using experiental design. The results showed that there is an agreeent between the experiental values and those calculated fro the odel developed which confirs its validity. The optial conditions are MgCl.6H O/MgO (X 1 ):., Mixing tie (X ): 5 in and Stirring speed (X 3 ): 115 rp. The responses are: copressive strength = MPa and setting tie = 41 in. The interpretation of results found by DRX, IR, SEM and TG-DTA confirs the presence of phase 5 which is responsible for the good copressive strength of agnesiu oxychloride ceent. ACKNOWLEDGEMENTS: This work was supported by a grant fro Ministry of Higher Scientific Research of Tunisia. The authors would like to thank the technical tea of the National Research Centre of Materials Sciences in Borj Cedria Technological Park and of LMGC in University of Cergy-Pontoise. REFERENCES [1] G. Li, Y. Yu, J. Li, Cons and Buil. Mat, 008,, [] JF. Montle, KG. Mayhan, J Fire Flaability/Fire Retard. Che, 1974, 1, [3] R. Siddique, TR. Naik, Waste Manage, 004, 4, [4] H. Yu, Magnesiu Oxychloride Ceent and its Application, 1st ed., China Building Materials Industry Press, Beijing, [5] L, Zongjini, CK, Chau, Ce. Concr. Res, 007, 37, [6] D.H. Deng, C.M. Zhang, Ce. Concr. Res, 1999, 9, [7] Y. Li, H.F. Yu, J.M. Dong, J. Wen, Y.S, J. Chin. Cera. Soc. 013, 41, [8] J. J, Beaudoin, V.S, Raachandran, Ce. Concr. Res 1975, 5, [9] C.Y. Wu, H.F. Zhang, H.F. Yu, Adv. Ce. Res. 013,5, [10] K. Xu, Y. Guo, Q. Sun, S. Dong, Z. Li, 01, 3, [11] D.H. Deng, C.M. Zhang, Ce. Concr. Res. 1996, 6, [1] Y. Li, H. Yu, L. Zheng, J. Wen, C. Wu, Y. Tan, Constr. Build. Mater. 013, 38, 17. [13] D.Mathieu, R.Phan Tan Luu, Nerod-W Software. Aix-Marseille III University. France, [14] Goupy J, Modélisation par les plans d expériences, Techniques de l ingénieur. Traité Mesures et Contrôle pp1 3, 000. [15] S. Zhao, J. Fan, W.Sun, Constr. Build. Mater, 014, 50,