INFLUENCE OF CEMENT BLEND AND AGGREGATE TYPE AN STRESS-STRAIN BEHAVIOR AND ELASTIC-MODULUS OF CONCRETE

Paper presents an experimental investigation in which four aggregate t ypes-granite, dolomite, andesite, and quartzite - were used in concret es made with four cement types-ordinary portland cement (OPC) and blen ds of OPC with silica fume, slag, and fly ash. The influence of these mix variables on short-term stress-strain behavior and concrete elasti c modulus E was assessed. The results showed clearly that E was marked ly dependent on aggregate and cement type, and that age played an impo rtant role. Andesite and dolomite yielded considerably stiffer concret es than granite or quarizite. Silica fume produced concretes of simila r or slightly greater stiffness than OPC, but slag and fly ash reduced stiffness, particularly at early ages, on an equal strength or water- cement ratio (w/c) basis. The most plausible mechanism to explain the results would be that silica fume densified the interfacial zone betwe en paste and aggregate, while slag and fly ash do not have the same ab ility in this regard. A practical design approach for engineers to est imate concrete E for the various combinations of materials is also giv en.