关键词: 混凝土;冻融循环;核磁共振;孔隙分布;动弹模量

Abstract: In order to study the effect of pore distribution on the frost resistance of recycled concrete under freeze-thaw cycles,three sets of concrete were selected, and the replacement rate of recycled aggregate was 0%, 50% and 100% respectively.The decomposition and change of the internal pore structure during the freezing and thawing process of concrete were monitored by nuclear magnetic resonance (NMR)technique.The results show that the freeze-thawing performance of ordinary concrete and 50%substitution rate is similar to the ordinary concrete in freeze-thaw cycle test,and the pore expansion is not obvious,and the pore expansion of fully replaced recycled concrete is significant,and the frost resistance of concrete is obviously reduced.The change of pore distribution and the change rate of pore volume in the concrete can reflect the frost resistance of concrete,which can be used as one of the important indexes to judge the frost resistance of concrete.

Key words: concrete;freeze-thaw cycle;nuclear magnetic resonance;pore distribution;relative dynamic modulus of elasticity