ABSTRACT
Abstract The paper presents results on the effects of time-dependent changes in the ITZ on mechanical properties of concrete. Concretes were prepared with OPC at two w/c ratios (0,43 and 0,61). Two different crushed aggregates were used, derived from andesite and dolomite rock, comprising coarse and fine fractions. The compressive strength and elastic modulus of the concretes were measured up to 90 days after casting. At the various ages of testing, samples were cut from companion specimens, and subjected to a preparation regime before being examined under a SEM for ITZ properties of porosity, percentage anhydrous material, and quantity of CH. The results, although only preliminary, suggest that time-dependent changes in stiffness of concretes made with different aggregates may be explained in terms of development of the characteristic properties of the ITZ. Keywords: Interfacial transition zone, aggregates, stiffness, microstructure.
