B Lothenbach

B Pacewska

B. Trybalska

E Garcia

E. Żugaj

HFW Taylor

M Bouasker

P Lura

R Talero

V Antonovich

VL Bonavetti

W Kurdowski

W Nocuń-Wczelik

W. Nocuń-Wczelik

Crossref

Application of calorimetry as a main tool in evaluationof the effect of carbonate additives on cement hydrationW. Nocun´-Wczelik • B. Trybalska • E. _ZugajReceived: 19 October 2012 / Accepted: 16 January 2013 / Published online: 12 February 2013 The Author(s) 2013. This article is published with open access at Springerlink.comAbstract Calorimetry was applied to follow the hydra-tion in the Portland cement–dolomite–limestone mixtures.In the experiments the limestone additive of various fine-ness (standard component of various common cements), aswell as the dolomite additive (not a standard component)were used. The rate of hydration versus time for commoncements reflects the proper setting and early hardeningduring the first days after mixing with water (two or threepeaks and the induction period between them). The aim ofmeasurements presented in this work was to show thecourse of heat evolution curve and the heat evolved values,equivalent to the acceleration/retardation of hydration, incase of the pastes produced from Portland cement and thecarbonate additives mixed in variable proportions, as wellas to verify the results by other methods. The rate of heatevolution accompanying cement paste hydration, total heatevolved, conductivity of hydrating suspension and rheo-logical (flow) properties versus time are modified by thefine grained carbonate additives. This is due to the hypo-thetical nucleating effect of limestone and dolomite.Keywords Cement  Limestone  Dolomite Heat of hydration  Rheology  Chemical shrinkageIntroductionThe kinetics and mechanism of hydration in variouscementitious systems can be investigated by calorimetry[1–4]. The heat evolution curve (dQ/dt = f(t)) reflects thefluctuations of the overall rate of reactions occurring in thehydrating system and accompanying cement setting andhardening. The heat evolution profile consists generally ofthe two peaks with the induction period between them andthis can be observed only in case of binding materials inwhich the hydration reactions, structure formation and,finally, proper setting and strength development takesplace. The heat evolved versus time plot corresponds to thegrowth of hydration products.The production of Portland cement containing lime-stone, interground or blended with clinker, has increased inthe past decades due to technical, economical and envi-ronmental reasons [5–7]. The technical reasons mean thesatisfactory physical and mechanical properties of hydratedcement paste; the economic and environmental reasonsinclude energy saving during the decreased clinker pro-duction and consequently the reduction of environmentalpollution by carbon dioxide.The idea of using dolomite as a component of cement isnot quite new. Some reports appeared in early 80-ties inGermany [8, 9]. However, this material has not been takeninto account in the European standardization process, whenthe Portland limestone cement was implemented. Theoret-ically, in highly alkaline environment of cement paste theso-called dedolomitization process can occur, leading to theformation of brucite with no binding properties and possiblerisk of damage due to expansion. There are the other phe-nomena discussed as the alkali carbonate reaction in thepaste (dolomite) aggregate interface is concerned [10, 11].In some countries the limestone deposits do not complywith the quality requirements given in the EN 197-1 standard(min. 75 % CaCO3) because they contain inclusions ofdolomite and their more economical disposal is required.Only a few reports dealing with dolomite usage as cementW. Nocun´-Wczelik (&)  B. Trybalska  E. _ZugajFaculty of Material Science and Ceramics, University of Scienceand Technology AGH, Al. Mickiewicza 30,30-059 Krako´w, Polande-mail: wiesia@agh.edu.pl123J Therm Anal Calorim (2013) 113:351–356DOI 10.1007/s10973-013-2994-6constituent have appeared and according to all authorsdolomite can be implemented as cement component; quiterecently in Germany there was a research project [8, 9].The usage of dolomite/dolomitized limestone is expec-ted to increase in the nearest future in terms of the growthof supplementary cementing materials ratio in cements,forced by reduction of carbon dioxide emission. The pos-sible application of dolomitized limestone as a componentof mixtures for geotechnical application should be con-sidered. This problem can be related generally to the ideaof sustainable development.This study focused on the kinetics of early hydration inthe Portland cement–dolomite–limestone mixtures. Thefollowing techniques, providing the continuous monitoringof hydration process were used: calorimetric measure-ments, electric conductivity measurements in the hydratingsuspensions, shrinkage and rheological characteristics ofhydrating cement pastes.ExperimentalMaterialsThe commercially produced standard Portland cements CEMI 42,5R was used (Blaine specific surface 3,550 cm2 g-1).The chemical composition of cement is given in Table 1. Thefollowing carbonate additives were used:Fine limestone powder; CaCO3—min. 99.0 % (Blainespecific surface 14,500 cm2 g-1).Coarse limestone powder; CaCO3—min. 98.5 % (Blainespecific surface 1,500 cm2 g-1).Dolomite; CaCO3MgCO3—min. 98.0 % (Blaine spe-cific surface 4,600 cm2 g-1).The grain size distribution of particular carbonate reagentsis plotted in Fig. 1.The mixtures of cement with limestone of differentfineness and the mixtures of cement with dolomite weresubsequently produced.As one can see the grain size distribution curves of basiccement and dolomite run close to each other (Fig. 1).MethodsThe rate of heat evolution was followed by means of dif-ferential microcalorimeter on the pastes at water to cementratio 0.5. The measurements of conductivity were carriedout on the continuously stirred water–cement suspensionsat w/c = 10, with help of equipment with sensor andmeasuring device. The measurements were carried out attemperature 20 C in glove box using calibrated Hg elec-trode. The rheological parameters of hydrating suspensionswere determined from the flow curves taken with a rota-tional viscometer. Some selected samples were subjected tothe evaluation of the so-called chemical shrinkage, usingbasic laboratory equipment (glass vials and pipettes) andprocedure similar to that given in the ASTM Standard C1608-07 [12, 13]. Some samples were observed under SEMwith EDS microanalyzer, to characterize the microstructure.Results and discussionThe heat evolution curves are shown in Figs. 2, 3, 4.In Table 2 some parameters relating to the heat evolutioncurves characteristics are listed. The changes of conduc-tivity versus time for cement–water suspensions withadmixtures are plotted in Fig. 5; the results of chemicalshrinkage in Fig. 6 and the flow curves in Fig. 7, respec-tively. The example microstructures of fractured 7-dayhydrated samples are presented in Fig. 8.From the data presented above one can see that theadditives do not reduce markedly the rate of heat evolutionor the total heat evolution as it would result from theirpercentage in the hydrated mixtures. Added as 5 % bymass of mixed binder they play a role of active cementreplacement and this refers both to the fine, coarse lime-stone and dolomite powder. Obviously, the effect of theTable 1 Chemical composition of cementComponents SiO2 Al2O3 Fe2O3 CaO MgO SO3 Na2O K2O Cl- LoiPercentage 20.2 5.7 3.2 64.5 1.6 2.1 0.18 1.11 0.013 1.4024681012140.1 1 10 100 1000Grain diameter/µmContent/% CEMI 42,5RDolomite Fine limestoneCoarse limestone Fig. 1 Grain size distribution of cement and particular carbonatereagents352 W. Nocun´-Wczelik et al.123finest limestone powder is more clearly pronounced, in theform of separate, third peak attributed to the calcium alu-minate intensive hydration (possible formation of calciumcarboaluminate) [14–16]. However, the total heat evolvedvalues do not decline much from those for the other series;dolomite gives similar course of heat evolution as coarseaggregate. The differences do not exceed generally the 5 %of total values.The conductivity curves reflecting the concentration ofions in the liquid phase are obtained at higher w/c (becauseof instrumental reasons) to show a competition betweendissolution and precipitation from the liquid phase under01230 5 10 15 20 25 30 35 40Time/hHeat liberation/10 Jg–1 h–1CEM I 42,5R5 % C fine10 % C fine25 % C fine30 % C fineFig. 2 Heat evolution of cement with fine limestone powder additive01230 5 10 15 20 25 30 35 40Time/hHeat liberation/10 Jg–1 h–1CEM I 42,5R5 % Ccoarse10 % Ccoarse25 % Ccoarse30 % CcoarseFig. 3 Heat evolution of cement with coarse limestone powderadditive01230 5 10 15 20 25 30 35 40Time/hHeat liberation/Jg–1 h–1 CEM I 42,5R5 % Dol10 % Dol25 % Dol30 % DolFig. 4 Heat evolution of cement with dolomite additive05101520250 200 400 600 800 1000 1200 1400 1600Time/minConduct./mS cm–1CEM ICEM + 30 % C fineCEM I + 30 % C coarseCEM I + 30 % DolomiteFig. 5 Conductivity of cement suspensions produced from CEM I42,5R with additives (Cfine fine limestone powder, Ccoarse coarselimestone powder) (w/c = 10)Table 2 Heat evolved on hydrationSamples Heat evolvedvalue, kJ g after41 h/for1 g mixed sampleHeat evolved value,kJ kg after 41 h/for1 g cement insampleQ/Qcem.CEM I 264 264 1005 % Cfine 274 288 10910 % Cfine 258 287 10925 % Cfine 230 307 11630 % Cfine 221 316 1205 % Ccoarse 261 275 10410 % Ccoarse 253 281 10625 % Ccoarse 220 293 11130 % Ccoarse 198 283 1075 % Cdolomite 273 287 10910 % Cdolomite 232 258 9825 % Cdolomite 208 277 10530 % Cdolomite 195 279 107Cfine fine limestone powder, Ccoarse coarse limestone powder00,010,020,030,040,050,060 20 40 60 80Time/hShrinkage/ml g–1  cem.CEM ICEM I + 20 % DolomiteCEM I + 20 % C coarseCEM I + 20 % C fineFig. 6 Chemical shrinkage of pastes produced from CEM I 42,5Rwith additives (Cfine fine limestone powder, Ccoarse coarse lime-stone powder) (w/c = 0.4)Application of calorimetry as a main tool 353123the influence of different factors. The results of conduc-tometric measurements in the suspension with water tosolid ratio 10 should be compared to the typical curve forneat cement—after rapid growth soon after mixing withwater the conductivity/concentration increases slowly tosome maximum (corresponding to supersaturation) andthen diminishes because of the precipitation of hydrationproducts. The results for dolomite and limestone during thefirst minutes are quite similar; however, presumably theprecipitation of early product in the diluted suspension withdolomite occurs better. This would prove the effect ofdolomite grains surface as effective nucleating site. Theplots for the suspensions with additives show that theconductivity/concentration of ions decreases at early ageand subsequently increases slowly to the maximum as well.One could speculate that the deposits of hydration productsform on the surface of filling agent grains and lower theconcentration; therefore, the maxima of conductivity/con-centration in the suspensions with 30 % dolomite andcoarse limestone are more or less delayed, while in the finelimestone powder mixture with cement the maximumeffect is observed at the same time as in cement suspension.040801201602000 50 100 150 200 250Dr/s–1Tr/PaCEM I CEM I + 5 % DolomiteCEM I + 20 % DolomiteFig. 7 Flow curves of cement pastes produced from CEM I 42,5Rwith dolomiteTable 3 Rheological parameters of hydrating cement–dolomite pastesSamples w/c g/Pa s Sy/Pa Smax/PaCEM I 42,5R 0.4 5.4 11.8 16.1CEM I ? 5 % CaMg[CO3]2 0.4 13.4 42.7 68.9CEM I ? 20 % CaMg[CO3]2 0.4 16.5 45.1 71.5g viscosity, Sy yield stress, Tmax rigidity of thixotropic structureO KaC Ka SiKaCaKbCaKaCaKa0.90cb1.80 2.70 3.60 4.500.90 1.80 2.70 3.60 4.50o KaSiKaC KaAlKaMgKaK KaCaKbK KbaFig. 8 SEM. Microstructureof cement–dolomite paste atw/c = 0.5. Seven-day hydration(a) with EDS plots. See theportlandite crystal (1, b) andspherical aggregate of thinC–S–H plates with Mg andAl (2, c)354 W. Nocun´-Wczelik et al.123At early age, up to 20 h, a significant increase of chemicalshrinkage is observed (Fig. 6). The shrinkage is the highestin the case of paste with 30 % fine limestone powder; itmeans that the process is accelerated. The shrinkage changesfor the other samples occur at first identically as for thereference; the similar rate of water consumption is thusproved. The breakdown of shrinkage curves after the initialgrowth can be attributed to the increasing role of diffusionmechanism in the hydration process. Since the results ofchemical shrinkage measurements reflect the formation ofproducts rich in water and the formation of specific, more orless open pore structure it seems that in this case these factorsgive the similar results for 20 % coarse limestone anddolomite, as well as for cement paste produced at w/c—0.4but the water consumption is the highest in the case of finelimestone fraction (in this case the possible formation ofcarboaluminate occurs).One can notice (Fig. 7; Table 3) that the pastes pro-duced from cement with dolomite filler show the modifi-cation of rheological properties and consequently the flowcurves; this should be related to the action of additive.A significant increase of the yield stress and plastic vis-cosity, as a result of introducing the carbonate filler isclearly visible. The broader and broader hysteresis loopproves the strong thixotropy of suspension with dolomite.It means that in the presence of this additive, presumablytogether with some early hydration products, the strongstructure of fluid is produced. This maybe due to the roughsurface of filler grains. The thixotropic structure charac-terized by the so-called rigidity parameter (Tmax) is thenstrengthen too.As one could observe under the scanning electronmicroscope the surface of carbonate small grains wascovered with C–S–H formed as a dominating hydrationproduct; this was proved by the presence of Mg peak onEDS plot (see Fig. 8—the depth of surface penetration byelectron beam is ca. 3 lm).Conclusions• The rate of heat evolution accompanying cement pastehydration, total heat evolved, conductivity of hydratingsuspension and rheological (flow) properties versustime are modified by carbonate additives. This is due tothe nucleating and structural effect of limestone ordolomite filler.• The very fine carbonate additive (limestone powder ofBlaine specific surface 14,500 cm2 g-1), acting asprecursor of hydration products (nucleating agents) atearly age, contributes much to the formation of hydratedproduct—the rapid consumption of water (chemicalshrinkage measurements) and an additional peak on thecalorimetric curve seem to prove the formation ofcalcium aluminate hydrate phase.• The changes of chemical shrinkage in case of cement–coarse limestone or cement–dolomite pastes at earlyage are generally similar to those for the referencecement paste as it is proved by the chemical shrinkagemeasurements and reflect the supplementary characterof this additive.• The usage of dolomite (dolomitic limestone) as Port-land cement clinker replacement should be consideredin terms of the potential consolidation properties.• The densification of cement–dolomite suspension, foundduring the rheological examinations, seems to point outthe usage of dolomite enriched cement material in somegeotechnical applications.Acknowledgements Financial support from the Polish Ministry ofScience and Higher Education (tutorial activity of the University ofScience and Technology, Faculty of Material Science and Ceramics;Grant No: 11.11.160.938) is acknowledged.Open Access This article is distributed under the terms of theCreative Commons Attribution License which permits any use, dis-tribution, and reproduction in any medium, provided the originalauthor(s) and the source are credited.References1. 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Application of calorimetry as a main tool in evaluation of the effect of carbonate additives on cement hydration

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Application of calorimetry as a main tool in evaluation of the effect of carbonate additives on cement hydration

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