再生细骨料及其混凝土的微观结构特征

Micro-structure Characteristics of Recycled Fine Aggregate and Its Concrete

采用扫描电镜、能谱分析、X射线衍射、显微硬度和氮吸附等微观测试方法研究了再生细骨料及其混凝土的微观结构特征。研究结果表明:再生细骨料是一种组成复杂的、具有一定水化活性的和高渗透性的人造骨料,其主要矿物相为SiO2、CaCO3以及少量的C2S。再生细骨料混凝土内部水泥石孔隙较多,结构密实性较差,同时其与再生细骨料间存在较为明显的界面过渡区,该界面过渡区宽度较大,且界面过渡区两侧的骨料和水泥石的显微硬度均较低。再生细骨料的多孔结构,以及再生细骨料混凝土内部水泥石和界面过渡区微观结构缺陷是导致其大孔增多的主要原因,大孔的增多会对混凝土抗渗性产生不利影响。

The characteristics of recycled fine aggregate（RFA） and its concrete（RFAC） were analyzed by SEM,EDXA,XRD,Micro-harness and nitrogen absorption.The results show that RFA is an artificial aggregate with complex compositions,certain hydration activity and high permeability.The mineral compositions of RFA include SiO2,CaCO3 and a small quantity of C2S,which has a certain hydration activity and can form hydration productions.The compaction rate of cement paste in RFAC is low because of pores in it.There is obvious interfacial transition zone（ITZ） between RFAC and cement paste,and its width is bigger than that in ordinary concrete.In addition,the values of micro-hardness of the interfacial transition zone on both sides of RFA and cement paste are lower.The porous structure of the recycled fine aggregates and defects of ITZ are main reasons for big pores in RFAC,which has bad effect on impermeability of RFAC.