RELATIONSHIP BETWEEN MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF THE PASTE-AGGREGATE INTERFACE

An experimental study of the the interfacial zone between aggregate an d cement paste was undertaken. The study adapted a newly developed pus hout method. A closed-loop controlled setup was used to measure force and slip-displacement continuously during loading. The experimental da ta were analyzed by using a recently proposed theoretical model. It wa s observed that the method provides a useful way of characterizing the interfacial properties of the transition zone, including the stiffnes s, strength, friction, and fracture energy of the interface. The trans ition zone was further investigated by using backscattered electron im aging and energy, dispersive analysis of x-rays (EDAX) to characterize the microstructure of the interface. The relationship between mechani cal properties and microstructure of the interfacial zone was studied. Various factors such as type of aggregate, treatment of aggregate sur face, mixing process, and incorporation of silica fume were investigat ed. It was found that the microstructure of the interfacial zone can b e significantly improved by aggregate pretreatment and mixing methods, and thus the mechanical interfacial properties can be enhanced.