机制砂掺量对自密实轻骨料混凝土碳化性能的影响机理

为探究机制砂掺量对自密实轻骨料混凝土碳化性能的影响及其变化规律，采用固定砂石体积法和改进的全计算法配制了5组机制砂掺量(0、30%、60%、80%、100%)的自密实轻骨料混凝土，并与2组机制砂掺量(0、100%)的自密实混凝土对比，测试了各龄期下混凝土的碳化深度，并通过扫描电子显微镜(scanning electron microscope, SEM)对比研究了自密实轻骨料混凝土和机制砂自密实轻骨料混凝土碳化前后的微观结构。结果表明：随着龄期的增长，混凝土碳化深度不断增加，但碳化速率前期较大，后期较小；机制砂的掺入能够细化孔结构，提高硬化浆体和骨料过渡界面区的密实度，轻骨料特有的内养护机制能够改善骨料水泥石过渡区界面结构，均可提高混凝土的碳化性能。最后，得到了关于机制砂掺量的自密实轻骨料混凝土碳化深度预测模型，可为机制砂自密实轻骨料混凝土耐久性预测提供参考。

Study on the Influence Mechanism of the Content of Manufactured Sand on the Carbonation Performance of Self Compacting Lightweight Aggregate Concrete

In order to explore the influence of the amount of manufactured sand on the carbonation performance of self-compacting lightweight aggregate concrete and its variation law, five groups of self-compacting lightweight aggregate concrete with the amount of manufactured sand (0%, 30%, 60%, 80%, 100%) were prepared by using the fixed sand volume method and the improved full calculation method. Compared with two groups of self compacting concrete with the amount of manufactured sand (0%, 100%), the carbonation depth of concrete at each age was tested, The microstructure of self-compacting lightweight aggregate concrete and manufactured sand self-compacting lightweight aggregate concrete before and after carbonization was studied by SEM. The results show that the carbonation depth of concrete increases with the increase of age, but the carbonation rate is larger in the early stage and smaller in the later stage; The addition of manufactured sand can refine the pore structure and improve the compactness of the transition interface between hardened slurry and aggregate. The unique internal curing mechanism of lightweight aggregate can improve the interface structure of aggregate cement stone transition area and improve the carbonation performance of concrete. Finally, the prediction model of self-compacting lightweight aggregate concrete carbonation depth about the content of manufactured sand is obtained, which can provide a reference for the durability prediction of manufactured sand self-compacting lightweight aggregate concrete.