Study on the hardening mechanism of cement asphalt binder

The hydration and hardening mechanism of cement asphalt binder (CAB) was studied. The early hydration process, hydration products and paste microstructure of CAB made by Portland cement and anionic asphalt emulsion were investigated by calorimetry, X-ray diffraction, and environmental scanning electron microscopy. The early hydration process of CAB can be characterized as 5 stages similar to those of Portland cement. There is no chemical reaction detected between cement and asphalt, hence no new hydration products other than those of Portland cement are produced. The hardening of CAB begins with the hydration of cement. When the hydration of cement comes into the acceleration period and its exothermic rate comes to the maximum, the coalescence of asphalt particles in asphalt emulsion is triggered. In the hardened system of CAB, it was found that the hydration products of cement form the skeleton and are covered by the continuous asphalt film. They formed an interpenetrating network system. The emulsifiers in the asphalt emulsion may retard the hydration process of cement.