Study on physical and chemical properties of renewable brick power and hydration kinetics of cement paste

In response to national strategies such as green, low-carbon, and environmental protection, and to alleviate the problems of large construction waste stockpiles and low recycling rate, renewable brick power with different particle sizes was prepared by physical grinding method. On the basis of studying the basic characteristics of particle size on the particle characteristics, surface binding energy, and activity of RBP, the influence of particle size on the hydration characteristics of recycled brick powder-cement cementitious material system was clarified. Finally, the hydration kinetic parameters of RBP -cementitious material system were obtained by Krstulovic-Dabic model, and the hydration process of recycled brick powder-cementitious material system was quantitatively described. The results show that with the decrease of particle size, the content of fine particles of RBP increases, the angularity of particles decreases, the degree of lattice distortion of silicon-aluminum minerals increases, the surface binding energy decreases, and the hydration activity increases. The incorporation of recycled brick powder reduces the hydration heat release rate, cumulative heat release and hydration degree of the slurry, and delays the time of the exothermic peak. In the early stage of hydration, the RBP mainly plays the role of physical filling and crystal nucleus. At 25℃, the hydration process of RBP -cement cementitious material is divided into three stages : crystal nucleation and crystal growth (NG) → phase boundary reaction (I) → diffusion (D). With the decrease of the particle size of the RBP, the hydration rate of the slurry is accelerated, the hydration heat is increased, the hydration degree is improved, and the hydration microstructure is more uniform. The research results can lay a theoretical foundation for the production of RBP and its efficient and high-value application in cement-based materials.