Study on the rheological properties of fresh cement asphalt paste

Abstract

The rheological properties of fresh cement asphalt paste (CA paste) were investigated, in which influencing factors such as type of asphalt emulsion, temperature, and time were discussed. CA pastes with two types of asphalt emulsions and varied asphalt contents were prepared at 0, 20 and 40 °C. The initial yield stress and its development over shelf time were tested to characterize the rheological properties of the pastes. The measurement of semi-adiabatic temperature development during hydration and optical microscopic observation were carried out to determine the hydration kinetics and microstructure evolution of the pastes. Results indicate that the initial flowability and flowability retention over shelf time of the pastes visibly improve because of the plasticizing effect of the asphalt emulsion and its retardation effect on cement hydration. The anionic asphalt emulsion is more effective than the cationic type because the former exhibits favorable adsorption onto the surface of cement grains. The temperature sensitivity of the rheological properties of the CA paste depends on the type and content of asphalt emulsion. The effects of time and temperature on rheological behavior were integrated into the effect of cement hydration degree. A generalized model linking yield stress and relative hydration degree α′ was established. Experimental results show that yield stress increases in a roughly linear fashion with 1/(1− α′) for all tested CA pastes.