engleski

Kinetics of cement hydration of type CEM I 42.5R without and with replacement addition of fly ash

Fly ash is a waste material formed by combustion in coal fired thermal power plants. It is usually used as a replacement material for cement in the cement industry, in this way is solved the environmental problem of waste disposal, reduced the CO2 emissions from cement production, protected the natural resources and reduced the production cost of cement. In this paper is presented the influence of the addition of fly ash (from the thermal power plant Plomin2, HEP) as replacement material on the kinetics in the early phase of cement hydration (type CEM I 42.5R). Hydration was carried out in isothermal conditions (20 ± 0.01 °C) up to 48 hours in cement paste with and without an addition of fly ash in the amount of 5 and 15 wt.%. Cement pastes were prepared with weight ratio of w/s=0.5 (water/solid (solid = cement + fly ash)). Hydration in the cement paste was followed by using differential microcalorimety (DMC). The results obtained after the implementation of kinetic analysis indicate that the addition of fly ash in Portland cement CEM I 42.5R acts as an accelerator of cement hydration at an early stage of cement hydration. It extends the duration of the process of nucleation and growth (NG) that determines the overall rate of cement hydration, but also shortens the duration of the process of interaction on boundary phase (I) which in turn increases the hydration degree of cement. Increasing the degree of cement hydration is not only a result of rapid hydration, but it could be confirmed the influence of fly ash on the hydration process in which fly ash acts as nucleation place, which is the physical role of the substitute supplement.

fly ash; cement; portlandite; hydration; kinetics; TG/DTG

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