Microscopic Study on Hardening Process and Structural Defect at the Boundary between Cement Paste and Aggregate

Abstract

During the hardening process of concrete, many structural defects are produced at the boundary between cement paste and aggregate. It is considered that both the seepage water around the aggregate and the sedimentative phenomenon of aggregate influence remarkably the formation of defects. The present observations using a scanning electron microscope show that the defective boundary consists of many fragile calcium hydroxide crystals.