再生砖粉掺量对水泥水化特性及力学性能的影响

The Effect of Recycled Brick Powder Content on Cement Hydration Characteristics and Mechanical Properties of Cement Mortar

摘要:

再生砖粉具有作为辅助性胶凝材料的潜力，但会导致水泥砂浆的力学性能显著降低，再生砖粉高效利用的关键在于其水化过程的调控。研究了不同掺量下再生砖粉-硅酸盐水泥浆体在25和60 ℃下的水化动力学特性，阐明了再生砖粉掺量对再生砖粉-硅酸盐水泥砂浆的力学性能和微结构的影响，揭示了再生砖粉-硅酸盐水泥的早期水化机理。结果表明：当水化温度为25 ℃时，再生砖粉-硅酸盐水泥的水化放热速率和水化放热量均随再生砖粉掺量增加而线性减小，60 ℃时降幅减小；25 ℃时再生砖粉-硅酸盐水泥的水化过程为成核结晶生长→相界面反应→扩散过程控制（NG→I→D），随着再生砖粉掺量增加，NG阶段与I阶段反应速率减小，D阶段反应速率增大，发生水化阶段转变的时间前移；60 ℃环境下水化加速，相界面反应速率提高，水化过程主要为NG→D；再生砖粉会导致浆体的孔隙率提高，有害孔数量增多，进而显著降低了砂浆强度，随再生砖粉掺量提高，砂浆强度降低幅度增大，而砂浆力学性能的降低幅度会随水化龄期增长而减小。

Abstract:

Recycled brick powder （RBP） has the potential to be used as an auxiliary cementitious material， but it will lead to a significant reduction in the mechanical properties of cement mortar. The key to the efficient utilization of RBP is the regulation of its hydration process. In this paper， the hydration kinetics of RBP-Portland cement paste at 25 ℃ and 60 ℃ was studied. The effect of RBP content on the mechanical properties and microstructure of RBP-Portland cement mortar was clarified. The early hydration mechanism of RBP-Portland cement was revealed. The results show that when the hydration temperature is 25 ℃， the hydration heat release rate and hydration heat release of RBP-Portland cement decreases linearly with the increase of RBP content， and the decreases at 60 ℃. At 25 ℃， the hydration of RBP-Portland cement is controlled by nucleation and crystal growth， phase interface reaction and diffusion process （NG →I→D）. With the increase of RBP content， the reaction rate of NG stage and I stage decreases， and the reaction rate of D stage increases. At 60 ℃， the hydration is accelerated， the phase interface reaction rate is increased， and the hydration process is controlled by NG→D. The RBP will lead to the increase of the porosity of the paste and the increase of the number of harmful pores， which will significantly reduce the strength of the mortar. With the increase of the content of RBP， the decrease of mortar strength increases， and the decrease of mortar mechanical properties decreases with the increase of hydration age.