Study on the Hydration Kinetics of Free CaO in High Calcium Fly Ash

CHEN Rong; CHEN Zhi-yuan

doi:10.3969/j.issn.1007-9629.2000.02.011

Abstract：In this paper, the hydration kinetic process of free CaO in system containing high calciumfly ash-H20 has been studied under different temperatures. The degree of hydration reaction at time twas determined by means of the volume expansion value L of hardened Portland cement-high calciumfly ash pastes. In the present experimental research it was found that the hydration is first-order reaction whose rate is directly proportional to the degree of reaction. For the hydration reaction the plot ofln L against t is a straight line and the intercept gives initial volume expansion L0 at t = 0 while therate constant k can be calculated from the slope. It was also found that the rate constant k increaseswith the increase of the temperature and the quantitative relationship between them followed Arrhenius' law and the plot of ln k against T-1 is linear for the reaction. Both frequency factor A and activation energy E a, which are known as Arrhenius parameters, were calculated. The experiment resultsalso show that the hydration reaction rate of free CaO increases while the volume expansion decreasesin the pastes through grinding high calcium fly ash. Some admixtures have influence on the kinetic parameters of the reaction.