Study on aggregate strengthening performance and principle of recycled concrete based on macro and micro tests

Abstract

Recycled concrete aggregates have a large number of voids, micro-cracks and interface transition areas, resulting in low apparent density and high water absorption and crushing values. If the recycled concrete aggregate is directly applied to the semi-rigid base, it will easily cause a series of problems such as cracks in the semi-rigid base and insufficient bearing capacity during service. In view of this, different concentrations of water glass, nano-SiO2 and infiltration crystalline materials were used to soak the regenerated aggregates, and the macro-strengthening effect was evaluated using the apparent density, water absorption rate and crushing value of the regenerated aggregates after chemical strengthening. The strengthening effect of the microstructure of the recycled aggregate is evaluated by SEM, EDS and pore size analysis test. The experimental results show that the water absorption and crushing value of the modified recycled aggregate soaked with three kinds of strengthening agents are significantly decreased in macro aspect. The micro cracks and interface transition zone of recycled aggregate are repaired, and the total pore diameter and maximum pore diameter are reduced. Compared with the strengthening effect of three kinds of chemical agents on recycled concrete aggregate, it is found that nano-SiO2 has a significant effect on macro index and microstructure of recycled aggregate.