Isothermal and solution calorimetry to assess the effect of superplasticizers and mineral admixtures on cement hydration |
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Authors: | P Siler J Kratky N De Belie |
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Institution: | (1) Centrum for Materials Research, Faculty of Chemistry, Brno University of Technology, Project ERDF CZ.1.05/2.1.00/01.0012, Purkyňova 118, 621 00 Brno, Czech Republic;(2) Magnel Laboratory for Concrete Research, Department of Structural Engineering, Ghent University, Technologiepark Zwijnaarde 904, 9052 Ghent, Belgium |
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Abstract: | The heat of hydration evolution of eight paste mixtures of various water to binder ratio and containing various pozzolanic
(silica fume, fly ash) and latent hydraulic (granulated blast furnace slag) admixtures have been studied by means of isothermal
calorimetry during the first 7 days of the hydration process and by means of solution calorimetry for up to 120 days. The
results of early heat of hydration values obtained by both methods are comparable in case of the samples without mineral admixtures;
the values obtained for samples containing fly ash and granulated blast furnace slag differ though. The results from isothermal
calorimetry show an acceleration of the hydration process by the presence of the fine particles of silica fume and retarding
action of other mineral admixtures and superplasticizer. The influence of the presence of mineral admixtures on higher heat
development (expressed as joules per gram of cement in mixture) becomes apparent after 20 h in case of fly ash without superplasticizer
and after 48 h for sample containing fly ash and superplasticizer. In case of samples containing slag and superplasticizer
the delay observed was 40 h. The results obtained by solution calorimetry provide a good complement to the ones of isothermal
calorimetry, as the solution calorimetry enables to study the contribution of the mineral admixtures to the hydration heat
development at later ages of the hydration process, which is otherwise hard to obtain by different methods. |
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