Microstructure and performance of new interface of recycled concrete with different cementitious material systems
Using analysis methods of microhardness tester and scanning electron microscope,the effect of three cementitious materials(ordinary Portland cement,high belite sulfoaluminate cement and alkali-activated slag)on the microstructure and performance of new in terface(new aggregate interface and new mortar interface)of recycled concrete is studied.The results show that the microhardness of new mor-tar interface is higher than that of new aggregate interface for C30 and C40 ordinary Portland cement recycled concrete,and the width of ITZ has little difference.The microhardness of new mortar interface of high belite sulfoaluminate cement recycled concrete(C30,C40,C50)strength grades is all higher than that of new aggregate interface.The microhardness of new aggregate interface of alkali-activated slag recycled concrete is higher than that of paste.Alkali-activated slag recycled concrete for the same strength grade,the microhardness of new aggregate interface is higher than that of new mortar interface,and the width of new aggregate interface obviously decrease compared with that of new mortar interface.Considering the microhardness and width of the ITZ,the performance of the new aggregate interface of three cementitious materials recycled concrete for the same strength grade is as follows,alkali-activated slag＞ordinary Portland ce-ment＞high belite sulfoaluminate cement,and the new mortar interface is consistent with the new aggregate interface.
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