Effect of some admixtures on the setting time and strength evolution of cement pastes at early ages

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1 Aville online t Construction nd Building Mterils 22 (8) Construction nd Building MATERIALS Effect of some dmixtures on the setting time nd strength evolution of cement pstes t erly ges S. Aggoun, *, M. Cheikh-Zououi, N. Chikh, R. Duvl Lortory of Mechnics nd Mterils of Civil Engineering, University of Cergy-Pontoise, 5, Mil Gy-Lussc, Neuville sur Oise, 9531 Cergy Pontoise Cedex, Frnce Lortory of Mteril nd Durility of Constructions, University of Constntine, Constntine 25, Algeri Received 6 August 4; received in revised form 19 April 6; ccepted 25 My 6 Aville online 9 Novemer 6 Astrct The purpose of this work is to investigte the effect of using some dmixtures such s clcium nitrte, triethnolmine nd triisopropnolmine, on the setting nd hrdening process of cement pstes t C temperture. Tests were performed on specimens from vrious mixes considering two types of cements. The results otined indicte tht the clcium nitrte used lone cts s setting ccelertor nd hs reltively little eneficil effect on the long term development of mechnicl resistnces. Regrdless of the cement type used, oth lknolmines used lone performed well s hrdening ccelertor t ll ges. The comined dditions produced t very erly ge significnt nd promising results with respect to oth setting nd hrdening ccelertion, nd to continuous compressive strength increse with time. Ó 6 Pulished y Elsevier Ltd. Keywords: Hrdening ccelertor; Setting ccelertor; Erly ge; Cement pste; Compressive strength; Setting time; Temperture 1. Introduction The present economic constrints require ccelertion in the speed of work in the construction industry. The need for concrete with sufficient strength t very erly ge is in mny situtions very importnt. Such concrete is otined through the use of some dmixtures such s wter-reducing superplsticiser, set ccelertors nd hrdening ccelertors. Stndrds out dmixtures for concrete nd mortr differentite etween set nd hrdening ccelertors nmely; Set ccelertor is defined s n dmixture tht decreses the initil setting for the trnsition of the mix from the plstic to the rigid stte. * Corresponding uthor. Tel.: ; fx: E-mil ddress: slim.ggoun@iupc.u-cergy.fr (S. Aggoun). Hrdening ccelertor is defined s n dmixture tht increses the rte of development of erly strength in the concrete with or without ffecting the setting time. Vrious dmixtures hve een used to get concrete with sufficient strength t very erly ge, the clcium chloride hs een in the pst the most widely used set ccelertor in this field. However, the presence of chloride cuses serious prolems regrding corrosion of reinforcing rs emedded in concrete memers. This hs renewed interest to develop numer of chloride-free dmixtures. Dodson [1] presented review of non-chloride, non-corrosive set ccelerting slts. His investigtion strted in 1962, it ws found tht the clcium formte, C(CHO 2 ) 2, cn e used s set ccelertor [2]. The second slt to fulfill requirements ws clcium nitrte, C(NO 3 ) 2, which ws ptented in 1969 [3]. After n intensive reserch, it ws estlished tht the clcium nitrte ws lso very effective corrosion inhiitor for metl imedded in concrete /$ - see front mtter Ó 6 Pulished y Elsevier Ltd. doi:1.116/j.conuildmt

2 S. Aggoun et l. / Construction nd Building Mterils 22 (8) The effect of clcium nitrte dditions on the setting chrcteristics of cements nd the steel corrosion hs een studied y Justnes [4 6]. It ws initilly ssumed tht the ccelerting effect ws dependent on the luminte content of the cement. This ssumption ws not verified for cements t low temperture (5 C). The results otined showed tht clcium nitrte does function s set ccelertor for cement etween 7 C nd C, ut the set ccelerting efficiency of clcium nitrte depended very much on the cement type used. It ws lso found tht the set ccelerting efficiency of clcium nitrte seems to increse with incresing elite content in cement or other cement chrcteristic promoting elite formtion in the clinker process. Triethnolmine (TEA), low tertiry lknolmines, is used s grinding id in cement mnufcture nd s constituent in certin dmixture formultions in concrete prctice. Depending on the cement type nd ddition rte, TEA cn produce either set ccelertion or retrdtion. An ddition rte of.2% to the type I Portlnd cement, TEA cts s set ccelertor, t.25% s mild set retrder nd t.5% severe retrder nd t 1% very strong ccelertor [7,8]. The effect on the strength development in cement pstes is lso dependent on the dded mount of TEA [9,1]. The ddition of smll mounts of higher tertiry lknolmines such s triisopropnolmine (TIPA) resulted in interesting increses in the strength of cement pstes t different ges [11,12]. A recent study crried out on the strength enhncing mechnism of triisopropnolmine presented compressive strength dt for 1 Portlnd cements tested s cement pste fter 28 dys of hydrtion [13]. The verge strength improvement with ppm TIPA dded to the mix wter ws 1%. The purpose of the present study is to find comintions of clcium nitrte with other compounds so s to fulfill the criteri for oth setting nd hrdening ccelertor. In this respect, the choice of lknolmines presenting developed sptil moleculr structure like TEA nd TIPA seems to e pproprite to verify previously indicted criteri. 2. Experimentl study The physicl properties nd the chemicl nlyses of the two cements (C1 nd C2) used in this investigtion re shown in Tle 1. Both cements present similr specific surfce nd triclcium silicte (C 3 S) content ut their triclcium luminte (C 3 A) content re different, with C2 cement contining lower mount in C 3 A. Ech of the cement type used is mnufctured y seprte cement plnt situted in est Algeri. The generl formul of the clcium nitrte used in the present study is: X Æ NH 4 NO 3 Y Æ C(NO 3 ) 2 Z Æ H 2 O. The coefficients X, Y nd Z vlues re respectively X =.92, Y =.5 nd Z =.826, which correspond to 19.% C 2+, 1.57% NH þ 4, 64.68% NO 3 nd 14.1% H 2 O. The chemicl formule of the triethnolmine nd the triisopropnolmine dded ws respectively N(CH 2 CH 2 OH) 3 nd (CH 2 CH 2 CH 2 OH) 3 [C 9 H 21 O 3 N]. The ltter dditions were Tle 1 Physicl properties nd chemicl nlyses of the cements Chemicl composition Cement 1 (C1) (%) Cement 2 (C2) (%) CO SiO Al 2 O Fe 2 O l5.37 SO MgO K 2 O N 2 O.26.8 Minerlogicl composition C 3 S C 2 S C 3 A C 4 AF Physicl properties Ignition Loss, % Bline surfce, m 2 /kg Addition used for C1 cement: either 18% of pozzoln or 1 12% of limestone. used for the purpose of providing the hrdening criteri to the lend dmixture. The w/c rtio for the vrious mixes investigted is.3. The chrcteristics of theses mixes re shown in Tle 2. The setting test on the cement pstes ws performed using Vict pprtus nd following EN196 3 procedure. The hrdening criteri were determined through simple compressive strength tests on cuic specimen mm 3. These ltter were cst in metllic moulds nd kept for 24 h t ± 1 C nd t 55 ± 5% RH. They were then demoulded nd conserved in wter t C until required for testing. Using hydrulic testing mchine, compressive strength tests were crried out ccording to the code NF Ech compressive strength vlue represents the verge of the results from 3 specimens tested. The study of the hydrtion process nd the recording of temperture evolution during cement setting nd initil hrdening were performed trough clorimetric tests in complince with stndrd NF P These tests hve een crried out t C temperture for period of 4 dys. Tle 2 Mixes investigted Cement type Mixes designtion % Nitrte % TEA % TIPA C1 M1... M M M M M C2 M... M M M M M

3 18 S. Aggoun et l. / Construction nd Building Mterils 22 (8) Results nd discussions 3.1. Setting Times nd Compressive Strength Tests were crried out on specimen t the ge of 1, 3, 7 nd 28 dys. The vrious results otined regrding setting times nd compressive strength re given in Tle 3 nd Figs. 1 nd 2. Both C1 nd C2 cements present higher diclcium silicte content ut different compring content in luminte nd luminte ferrite Effect of clcium nitrte (M11, M21) In regrds to C1 cement, with norml triclcium silicte content (8.33%), the clcium nitrte ffected significntly the evolution in the erly ge compressive strengths, they incresed y lmost 5% t 1 nd 3 dys compred to control mix vlues. The improvements noticed on the setting times were very smll. Considering C2 cement, which hs low triclcium silicte content (2.82%), the otined results show tht clcium nitrte cts s good setting Tle 3 Experimentl setting times nd compressive strengths results Mixes investigted Setting times (±1 min) Compressive strength (MP) Initil Finl 1 dy 3 dys 7 dys 28 dys M1 (control) M11 (Nitrte) M12 (TEA) M13 (TIPA) M14 (Nitrte + TEA) M15 (Nitrte + TIPA) M (control) M21 (Nitrte) M22 (TEA) M23 (TIPA) M24 (Nitrte + TEA) M25 (Nitrte + TIPA) Compressive Strength (MP) Compressive Strength (MP) M1 (Control) M11 (Nitrte) M12 (TEA) M13 (TIPA) M14 (Nitrte+TEA) M15 (Nitrte+TIPA) 1 dy 3 dys 7 dys 28 dys M (Control) M21 (Nitrte) M22 (TEA) M23 (TIPA) M24 (Nitrte+TEA) M25 (Nitrte+TIPA) 1 dy 3 dys 7 dys 28 dys Fig. 2. () Compressive strength for C1 mixes. () Compressive strength for C2 mixes. ccelertor. Compred with control mix initil nd finl setting times, the presence of clcium nitrte reduces them y %. However, s the erly ge compressive strength ws not improved, clcium nitrte cn not e clssified s hrdening ccelertor though it improved the 28 dys strength y %. Time (min) M1 (Control) M11 (Nitrte) M12 (TEA) M13 (TIPA) M14 (Nitrte+TEA) M15 (Nitrte+TIPA) Time (min) M (Control) M21 (Nitrte) M22 (TEA) M23 (TIPA) M24 (Nitrte+TEA) M25 (Nitrte+TIPA) 5 5 Initil Finl Initil Finl Fig. 1. () Setting times for C1 mixes. () Setting times for C2 mixes.

4 S. Aggoun et l. / Construction nd Building Mterils 22 (8) Thus the efficiency of the clcium nitrte s set ccelertor seems to e dependent on the cement chemicl composition, confirming therey the results otined y Justnes [5] Effect of triethnolmine (M12, M22) The ddition of.5% TEA with C1 cement produced little effect on M12 mix setting times. The increse ws significnt on its erly ge compressive strength, 5% t 1 nd 3 dys, ut resonle in the long term, out % t 28 dys. Regrding C2 cement, this ddition rte reduced the M22 finl setting time to 75% control mix vlue. It lso improved significntly the compressive strength t 1 nd 3 dys y out 5%, ut modertely t 7 nd 28 dys y 15 %. These results clerly show tht the triethnolmine performed well s hrdening ccelertor regrdless of the cement type used Effect of triisopropnolmine (M13, M23) The initil nd finl setting times were hrdly ffected y the use of.5% TIPA with C1 cement. However, it produced mjor improvement on the compressive strength of M13 mix t ll ges. Compred to control mix M1, the increse in strength ws out % t 1 dy, 9% t 3 dys, 11% t 7 dys nd % t 28 dys. In the cse of C2 cement rich in C 4 AF, the use of the sme mount of TIPA reduced the finl setting time y out 4%. It lso improved considerly the compressive strength t ll ges of M23 mix, out 185% t 1 nd 3 dys, 13% t 7 dys nd % t 28 dys. Regrdless of the cement type used, the performnce of triisopropnolmine s hrdening ccelertor is greter thn tht of triethnolmine Effect of clcium nitrte comined with triethnolmine (M14, M24) The use of clcium nitrte in comintion with TEA resulted in their joining effects. The initil nd finl setting times were reduced respectively to 55% nd 65% for C1 cement nd to 7% nd % for C2 cement of their respective control mix vlues. The mechnicl resistnces were lso enhnced y 4% for M14 mix nd 3% for M24 mix t erly ge, nd t successive ges y respectively 5 3% for M14 mix nd 4 5% for M24 mix. Thus clcium nitrte comined to triethnolmine leds t the erly ges to some interesting results in terms of ccelerting oth setting nd hrdening Effect of clcium nitrte comined with triisopropnolmine (M15, M25) The joining effects were lso illustrted with the use of clcium nitrte in comintion with triisopropnolmine. The initil nd finl setting times compred with control mix vlues were reduced respectively y 45% for C1 cement nd y 35% nd 45% for C2 cement. Regrding M15 mix, the compressive strength increse for short nd long term ges ws respectively more thn 9% nd 45%. Such increse ws further improved with M25 mix s it recorded more thn 15% nd 11% respectively for short nd long term ges. Thus etter dmixture rectivity took plce with C2 cement which contins high luminte ferrite content. The process of ccelerting oth setting nd hrdening t erly ges ws further explicit with the use clcium nitrte comined to triisopropnolmine Hydrtion temperture evolution The het relesed y the cement during its hydrtion is trnslted into n importnt temperture increse from which the het quntity developed cn e evluted. The rte of hydrtion seems to depend on the permeility nd cohesion of the C S H gel cotings round the cement grins such tht its modifiction to more open flocculted structure fcilittes diffusion nd ccelertes hydrtion [14]. Clorimetric tests hve een relised for some mixes elorted with C2 cement only. The results my e presented grphiclly in terms of rte of het evolution versus time [7], or mximum rte of het evolution versus reciprocl to pek height [14] or temperture evolution versus time [11]. This ltter presenttion is dopted in the present work. The generl profile of ll the curves displyed in Fig. 3 ws similr ut with different rtes, in consistence with Temperture ( C) 1 4 M M24 M21 M Time (hours) Temperture ( C) 1 4 M M24 M21 M Time (hours) Fig. 3. () Temperture evolution with time ( h). () Temperture evolution with time ( 24 h).

5 11 S. Aggoun et l. / Construction nd Building Mterils 22 (8) the times results shown in Tle 3. The first hydrtion pek, indicting initil hydrtion rections, ppered quickly (etween 3 min) for M21, M22 nd M24 mixes nd ws quite difficult to locte precisely. The min pek, corresponding to the mximum temperture, indicted the principl rections tking plce during the hrdening phse. With respect to control curve, M21 temperture slope hs undergone n increse during the strting process indicting therey the presence of set ting ccelertor. The use of TEA lone, M22 curve, delyed during the first hours the hydrtion rection. The highest temperture recorded y M22 mix illustrted clerly the potentility of hrdening ccelertor. The comintion of clcium nitrte with TEA, M24 curve, performed etter s the temperture slope incresed during the initil setting ( 5 h) nd higher temperture vlue ws chieved compred to control curve, which mens n extr hrdening effect. Hence, M24 mix included oth spects of setting nd hrdening ccelertor. Referring to Fig. 3(), it my e interesting to exmine the joining effects through the vrition of M24 curve. Within the first hours, clcium nitrte cted s setting ccelertor y incresing the hydrtion rte, then follows second phse where TEA slowed the hydrtion rte mking M24 curve elow control curve. After 16 h from the strting process, the hydrtion rection ws rectivted with higher degree in the long term. Thus it my e inferred tht clcium nitrte cted initilly s setting ccelertor then triethnolmine took over y ccelerting minly the hrdening phse. According to Grtner [12], the triethnolmine seems to e mostly sored y cement prior to the development of ctlytic mechnism which fcilittes the trnsport of ferric ions through the queous phse in the form of ferric lknolmine complexes. 4. Conclusions Tests hve een crried out on cement pstes specimens to investigte the effect of using some dmixtures such s clcium nitrte, triethnolmine nd triisopropnolmine, on the setting time nd compressive strength evolution. In view of the dmixture rtes dded, the min results show tht: The clcium nitrte cted minly s setting ccelertor with efficiency depending on the cement chemicl composition. In the long term, the effect on the strength increse ws insufficient for it to e considered s hrdening ccelertor. Regrdless of the cement type used, oth triethnolmine nd triisopropnolmine performed well s hrdening ccelertor t ll ges. The comintion of clcium nitrte with either triethnolmine or triisopropnolmine resulted in their joining effects with time, trnslted y reduction in the initil nd finl setting times nd strength enhncement t ll ges of the cement pstes, prticulrly t erly ges. Used with equl dosge, triisopropnolmine is fr more efficient in terms of strength increse thn triethnolmine. References [1] Dodson VH. Concrete dmixture. New York: VN Reinhold; 199. [2] Dodson VH, Frks E, Rosenerg AM. US Ptent No. 3,21,7, Octoer 5, [3] Angtdt RL, Hurley FR. US Ptent No. 3,427,175, Ferury 11, [4] Justnes H. Report STF F9313. SINTEF Structures nd Concrete. Norwy: Trondheim; [5] Justnes H, Nygurd EC. The influence of technicl clcium nitrte dditions on the chloride inding cpcity of cement nd the rte of chloride induced corrosion of steel emedded in mortrs. In: Swmy RN, editor. Proceedings of interntionl conference on corrosion nd corrosion protection of steel in concrete. UK: Sheffield; p [6] Justnes H, Nygurd EC. Technicl clcium nitrte s set ccelertor for cement t low tempertures. Cement Concr Res 1995;25(8): [7] Rmchndrn VS. Action of triethnolmine on the hydrtion chrcteristic of triclcium silicte. J Appl Chem Biotechnol 1972;22: [8] Rixon R, Milvgnm N. Chemicl dmixtures for concrete. London: E nd FN Spon; [9] Heren Z, Ölmez H. The influence of ethnolmines on the hydrtion nd mechnicl properties of Portlnd cement. Cement Concr Res 1996;26(5):71 5. [1] Aid I, Mohmmed Ao-El-Enein SA. Rheologicl properties of cement pstes dmixed with some lknolmines. Cement Concr Res 3;33:9 13. [11] Justnes H. Accelertor lends for Portlnd cement. In: Second interntionl symposium on cement nd concrete technology in the s. Turkey: Istnul,. p [12] Grtner E, Myers D. Influence of tertiry lknolmines on Portlnd cement hydrtion. J Am Cerm Soc 1993;76(6): [13] Snderg PJ, Doncster F. On the mechnism of strength enhncement of cement pste nd mortr with triisopropnolmine. Cement Concr Res 4;34: [14] Wilding CR, Wlter A, Doule DD. A clssifiction of inorgnic nd orgnic dmixtures y conduction clorimetry. Cement Concr Res 1984;14(2):