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

Abstract

Calorimetry was applied to follow the hydration in the Portland cement-dolomite-limestone mixtures.In the experiments the limestone additive of various fineness (standard component of various common cements), as well as the dolomite additive (not a standard component) were used. The rate of hydration versus time for common cements reflects the proper setting and early hardening during the first days after mixing with water (two or three peaks and the induction period between them). The aim of measurements presented in this work was to show the course of heat evolution curve and the heat evolved values, equivalent to the acceleration/retardation of hydration, in case of the pastes produced from Portland cement and the carbonate additives mixed in variable proportions, as well as to verify the results by other methods. The rate of heat evolution accompanying cement paste hydration, total heat evolved, conductivity of hydrating suspension and rheological (flow) properties versus time are modified by the fine grained carbonate additives. This is due to the hypothetical nucleating effect of limestone and dolomite.

Heat of hydration of low-clinker cements

“…Addition of fly ash more distinctly retards the acceleratory period of cement hydration than slag, this tendency is especially clear for the high substitution rate of fly ashes. This retarding effect of the mineral additions on the cement hydration has been already reported [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35].…”

“…For composite binders containing fly ash, the hydration heat evolution has been studied, inter alia, by Nocuń-Wczelik [25][26][27], Pacewska et al [28][29][30], Giergiczny [31,32], Han et al [22], Kumar et al [33], Narmluk et al [34] and Mounanga et al [35]. Similarly, as for slag cements, the tests showed that the evolved heat decreases with increasing amount of fly ash addition.…”

“…Narmluk et al [34] found that fly ash retards the early hydration of cement but accelerates the hydration of cement in the later period at 20 and 35°C, but at 50°C and 50 % dosage of fly ash retards the hydration of cement at later age as well. Nevertheless, it is highlighted that the influence of fly ash addition on the hydration process can be different and it is dependent on the mineral composition and fineness of fly ash [25][26][27][28][29][30][31][32][33][34][35]. The kinetics and mechanism of hydration in different cementitious systems with fly ash has been also discussed in [25].…”

Influence of selected activating methods on hydration processes of mixtures containing high and very high amount of fly ash

“…These methods are frequently used in case of studies of hydration processes of cement in the presence of different additives (e.g. [37][38][39][40][41][42]). They are also useful in case of investigations of hydration/activation processes of high and very high volume fly ash mixtures.…”

The Effect of Dolomite Additive on Cement Hydration

“…The studies of hydration process in the mixtures of cement with limestone powder, dolomite powder and limestone -dolomite additive were reported by Nocuń-Wczelik et al [6]. In the pastes hydrating with fine grained dolomite powder the crystallization of products is accelerated and as a consequence the strength development is improved.…”