MICROSTRUCTURE OF THE INTERFACIAL ZONE BETWEEN LIGHTWEIGHT AGGREGATE AND CEMENT PASTE

Over recent years much attention has been given to the influence of the interfacial zone between aggregate and cement paste on the various properties of concrete. Most of the research work on this area has been carried out using normal weight aggregate. In the present paper experimental work on the interfacial zone between different types of lightweight aggregates and cement paste is presented. For high strength lightweight aggregate with a dense outer layer the nature of the interfacial zone between aggregate and cement paste is similar to that for normal weight aggregate. For lightweight aggregate with a weaker and more porous outer layer and for aggregate without any outer layer, the interfacial zone is more dense and homogeneous. Also for such aggregates the bond appears to be better due to an improved mechanical interlocking between the aggregate and the cement paste. The nature of the interfacial zone appears to depend on the microstructural characteristics of the aggregate. © 1990.