关键词: 再生混凝土;替代率;力学性能;低场核磁共振技术;孔结构;

Abstract: In order to study the influence of coarse aggregate replacement ratio(0,30%,50%,70%,100%)and curing age(3d, 7d, 14d, 28d)on the performance development of recycled concrete, the uniaxial compressive strength and splitting tensile strength tests of recycled concrete with different coarse aggregate replacement ratio were carried out, and the evolution of internal pore structure of recycled concrete under different conditions was analyzed by Low Field-Nuclear Magnetic Resonance(LF-NMR)technology.The results showed that the mechanical properties of recycled concrete were optimal when the substitution ratio was 30%.When the replacement ratio exceeded 50%,the mechanical properties of recycled concrete began to decrease significantly.The distributions of transverse relaxation time T2(obtained by nuclear magnetic resonance)of recycled concrete with different coarse aggregate replacement ratios were generally the same, showing an obvious three-peak distribution.The peak area gradually decreased with the increasing of curing age, and the peak point of the first peak had a tendency to shift to the left.Compared with the replacement ratio, the effect of curing age on the transverse relaxation time T2 distribution was more significant.Finally, a strength prediction model of recycled concrete based on the nuclear magnetic resonance porosity and different substitution ratios was established, it was found that the model prediction results had a good correlation with the test results.

Key words: recycled concrete; replacement ratio; mechanical property; LF-NMR; pore structure;