轻骨料混凝土抗碳化性能及微结构分析

Carbonation Resistance Performance and Microstructure Analysis of Lightweight Aggregate Concrete

为了探究轻骨料混凝土抗碳化性能及微结构,采用绝对体积法配制全轻骨料混凝土(ALWAC)和次轻骨料混凝土(SLWAC),并与普通混凝土(NC)比对,测试混凝土在各龄期下的碳化深度,通过MIP压汞测试对比研究NC和ALWAC碳化前后微细观孔结构变化。结果表明:轻骨料混凝土特有的内养护效果,轻骨料周围水泥石日趋密实,因而ALWAC和SLWAC较NC抗碳化性能优,且随碳化时间增长碳化速率显著降低;微结构分析表明经历28 d快速碳化试验后,NC和ALWAC孔隙率分别由14.36%、30.33%下降至13.53%、28.70%,定量说明了碳元素入侵造成大量孔隙被填充细化,与水泥水化产物反应生成CaCO_(3),孔径减小,密实度增加。最后给出了基于陶粒掺量的轻骨料混凝土碳化深度预测模型。研究成果可为轻骨料混凝土耐久性预测提供参考。

All-light Weight Aggregate Concrete(ALWAC)and Sub-light Weight Aggregate Concrete(SLWAC)were prepared by absolute volume method,and were compared with Normal Concrete(NC)in terms of carbonation depth at different ages.The microstructure changes of NC and ALWAC before and after carbonation were compared by Mercury Intrusion Porosimetry(MIP).The results showed that ALWAC and SLWAC had better carbonation resistance than NC because of special internal curing effect of lightweight aggregate which led to more compact cement stone surrounding the ceramsite.The carbonation rate of ALWAC and SLAWAC also decreased apparently with the increasing of carbonation age.Microstructural analysis showed that after 28 days of accelerated carbonation experiment,the porosity of NC and ALWAC declined from 14.36%and 30.33%to 13.53%and 28.70%,respectively.The result quantitative explained the reduction of pore diameter and the augment of compactness by the intrusion of carbon which filled and refined a large number of pores and reacted with cement hydration products to generate CaCO_(3).In addition,a model predicting the carbonation depth of lightweight aggregate concrete in consideration of ceramsite content was given.