再生粗集料混凝土界面微观结构的发展规律

Development Law of Interfacial Microscopic Structure in Recycled Coarse Aggregate Concrete

关键词:  再生粗集料混凝土  界面微观结构  界面过渡区  抗压强度

Key words:  recycled coarse aggregate concrete  interfacial microscopic structure  interfacial transition zone(ITZ)  compressive strength

摘要:

分别制作相同配合比的再生粗集料混凝土和普通混凝土试件.在养护龄期为3，7，14，28d时，将再生粗集料混凝土试件切割，取样，然后对其内部不同界面微观结构进行扫描电镜观测；同时对再生粗集料混凝土和普通混凝土试件进行了抗压强度试验，观察了加载后再生粗集料混凝土试件内部裂纹的分布情况.结果表明：随着龄期的增长，再生粗集料混凝土各个界面过渡区都有不同程度的发展；天然粗集料新砂浆界面过渡区发展相对缓慢；再生粗集料中老砂浆新砂浆界面发展较快，老砂浆与新砂浆结合较好；再生粗集料中天然粗集料老砂浆界面为混凝土浇筑前已存在的界面，并且存在着一定数量的微裂缝.再生粗集料混凝土3d抗压强度略高于普通混凝土，7，14，28d抗压强度则与普通混凝土基本相当.荷载作用下，再生粗集料混凝土内部裂纹主要分布在天然粗集料新砂浆界面以及天然粗集料老砂浆界面处.

Abstract:

Recycled coarse aggregate concrete and ordinary concrete specimens were prepared with the same mix proportion. The recycled coarse aggregate concrete was sliced and samples were taken at the age of 3, 7, 14, 28d, and then their interfacial microscopic structures were observed by SEM. The compressive strength of recycled coarse aggregate concrete and ordinary concrete specimens were tested under axial loading. The distribution of internal cracks in recycled coarse aggregate concrete was also analyzed. It is concluded that with the age increasing, each interfacial transition zone(ITZ) in recycled coarse aggregate concrete has a certain degree of development. The development of ITZ between natural coarse aggregate and new mortar is relatively slow. The development of ITZ between old and new mortar in recycled coarse aggregate is the best. And the ITZ between natural coarse aggregate and old mortar in recycled coarse aggregate originally exists with some cracks. Compressive strength of recycled coarse aggregate concrete is slightly higher than that of ordinary concrete at the age of 3d, and equal at the age of 7, 14, 28d. The internal cracks in recycled coarse aggregate concrete are mainly distributed in the ITZ between natural coarse aggregate and new mortar and the ITZ between natural coarse aggregate and old mortar.