Effect and Mechanism of Coral Powder on the Rheological Properties of Cementitious Materials

Abstract

To study the effect and mechanism of micro coral powder on the flow behavior of fresh cement paste, the fluidity and rheological parameters of cement paste with fine coral powder of different dosages were investigated. The influence mechanism of coral powder on rheological properties was investigated by testing the water demand, the adsorption behavior and the zeta potential. Results show that with the increasing dosage of coral powder, the fluidity of the cement paste decreases and the torque of cement paste increases at the same rotation speed. The derived yield stress and plastic viscosity increase with the increasing dosage of coral powder. Because micro coral powder has higher volume and area than cement with the same mass, the water demand ratio of coral powder is very high, which is one of the reasons for the fluidity drop with the coral powder content. With the same dosage of polycarboxylate superplasticizer (PCE), the adsorption amount and the adsorption ratio of PCE by blended micro coral powder are much higher than that of cement particles. Therefore, compared to cement paste without PCE, the fluidity of cement paste with PCE decreased more significantly at the same coral powder content. In addition, competitive adsorption of Ca2+ between coral and cement particles reduces the positive charge density on the surface of cement particles, causing the decrease of the adsorption capacity of cement particles for PCE, thus affecting its rheological properties.