ANALYSIS ON ITZ STRUCTURE OF SELF-COMPACTING CONCRETE

Interface transition zone between aggregate and cement paste (ITZ) is regarded as the main weak points in concrete. Density of ITZ structure of self-compacting concrete (SCC) is incredulous for satisfying the need of high mechanical properties and long term service life when fresh concrete is cast without vibration. In this investigation, SCCs with nature medium size sand and mixed sand which composed of superfine sand and manufactured sand were prepared according to the same mix proportion. One conventionally vibrated concrete (CVC) with natural medium size sand was made for comparison. Microhardness of ITZ structure of the SCCs and CVC was tested. ITZ structure of the SCCs were analyzed by means of SEM and metallographic test. The results show that good compact structures were acquired in both SCCs and CVC. The SCC prepared with mixed sand has a thicker and more porous ITZ than SCC with nature sand.