Surface properties of clay brick powder and its influence on hydration and strength development of cement paste. (20th September 2021) - Ouyang, Xiaowei
Highlights: The clay brick powder (CBP) has similar surface chemical properties as quartz. The effect of CBP on the early hydration of cement is due to its physical properties, rather than the chemical activities. The interface between CBP and hydrates is very weak. The main role of CBP playing in cement paste is the filler effect. Abstract: Replacing part of cement with recycled clay brick powder (CBP) can ease the environmental impact caused by construction waste disposal and cement production. This research studied the surface properties of CBP and its effect on the hydration and strength development of cement paste at the micro and sub-micro scales. Zeta potential measurement was applied to study the surface chemical properties of CBP. Based on it, the interactions between the main ions in the cement paste solution and the surface of CBP were discussed. Then the effect of CBP on the nucleation and growth of hydrates, and CBP/hydrates interfacial strength was investigated. The results show that CBP has similar surface properties as quartz powder (QP), even though the chemical compositions of them are different. Silicate is the main phase at the surface of CBP. The interactions of CBP's surface with Ca 2+ are due to an electrostatic force, which has an important effect on the nucleation and growth of hydrates (mainly C-S-H) on the surface of CBP, and the adhesion between CBP and the hydrates. The morphology of hydrates on the CBP particles is similar to that on the QP particles. It suggests that the effect of CBP particles on the early hydration of cement is mainly due to its physical properties, rather than the chemical activities. The interface between CBP and hydrates is very weak, and the chemical reaction of CBP in the cement paste is rarely presented. The main role of clay brick used in this study playing in cement paste is a filler, similar to quartz particles.