冻融循环下再生混凝土孔隙分布变化及其对抗冻性能的影响

为研究冻融循环下再生混凝土孔隙分布变化对抗冻性能的影响,选取再生骨料取代率为0%、50%、100%的三组混凝土进行冻融循环试验,基于核磁共振(NMR)技术,监测混凝土冻融破坏过程中内部孔隙结构的分布和变化情况.结果表明:冻融循环试验中,普通混凝土和50%取代率的再生混凝土抗冻性能相近,孔隙扩展不明显,而全取代再生混凝土内部孔隙扩展情况显著,混凝土抗冻性能明显降低;核磁共振测得的混凝土内部孔隙分布变化和孔隙体积变化率参数,能够很好的反映混凝土的抗冻性能,可以作为评判混凝土结构抗冻性的重要指标之一.

Effect of Pore Distribution of Recycled Concrete on Frost Resistance under Freeze-thaw Cycling

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.