Assessing the Efficiency of Chemical and Mineral Admixtures in Early Cement Hydration

About influence of some superplasticizers on hydration and the structure of hardened cement paste

“…According to [15][16][17], three main periods of cement hydration -induction, accelerated and delayed -are distinguished on thermokinetic dependence. In our opinion, the following three sections are of primary interest in the integral curve of heat of hydration of the PC in the early period of hydration: 1 -due to the heat of wetting and hydration of alkalis, free lime, partial hydration of C3A and the formation of primary ettringite; 2 -the so-called induction period, during which the hydration heat is practically not fixed; 3 -period of intense hydration heat (accelerated) due to hydration of the basic clinker minerals.…”

“…According to the data of [15], hydration heat in the initial period with hydration of C3S is 2.3 to 4.9 kJ/kg, depending on the dispersity of the binder, and the duration of this stage is from 20 to 38 minutes. In our studies (Table 5), the values for PC without SP, respectively Q1 from 2.15 to 6.6 kJ/kg, and the duration of the first period from 5 to 50 minutes.…”

“…classify the SP on the influence on the setting time (SP with a retarding influence or not). According to [15], the duration of the induction period during hydration of C3S is from 1.1 to 4 hours, depending on the dispersity. In our studies, the duration of the induction period for PC without SP was 1.8 to 3.1 hours (Table 6).…”

“…According to [15], the duration of the third period of hydration because of C3S hydration is 6.3 to 14.2 hours, depending on the size of cement particles, and the rate of hydration heat at this stage is from 8.2 to 19.8 kJ/kg · h. The total hydration heat at this stage is 44.8 to 90.9 kJ/kg. According to our data, the rate of hydration in the third period for PC without SP was from 2 to 25 kJ/kg · h, and the total hydration heat in the third period was from 26 to 94 kJ/kg (Table 7).…”

Optimization of selection process of constituent materials for high performance concrete and mortars

“…In this connection, important aspect of simultaneous application of different admixtures in cement-based systems is their compatibility with each other and with cement. Testing thermokinetic parameters of cement hydration is an effective method for estimation of compatibility [8]. These parameters allow prediction a series of properties for cement and concrete [9].…”