Interfacial interaction of aggregate-cement paste in concrete

Abstract

The chemical and physical interactions in the interfacial transition zone (ITZ) between three different types of coarse aggregates (limestone, granite and basalt) and cement paste were investigated. The results show that all the aggregates are chemically active. Signifi cant amounts of Ca 2+ , K + , and Na + are absorbed by all the aggregates from the cement solution, granite and basalt also absorb signifi cant amounts of OH -and release signifi cant amounts of Si 4+ into cement solution. The XRD, EDXA and pore structure results of the ITZ also show that more clinkers participate in the cement hydration in the ITZ of granite and basalt, and more hydrates are generated, hence resulting in a denser ITZ structure with a lower content of macropores. Although the limestone has the least activity, the connection between it and cement paste is tight, due to its rough surface and higher water absorption. Whereas the granite with smooth surface and lower water absorption has a loose connection with cement paste, many pores and cracks are visible, which is very detrimental to the concrete durability.

The Influence of Heat and Mechanical Treatment of Concrete Rubble on the Properties of Recycled Aggregate Concrete

“…The microstructure of the paste around the granite is denser than around the gravel, small pores and defects are visible and many groups of hydrates are closely bonded with each other. It is therefore difficult to identify the paste and the aggregate [30]. The physical interaction between the aggregate and the cement slurry depends mainly on the roughness of the surface and the absorbability of the aggregate.…”