Performance characteristics of lightweight aggregate concrete containing natural pozzolan

Pozzolans are materials of natural or artificial origin that are not cementitious by themselves, but form a hydraulic cement when mixed with lime hydrate due to their aluminosiliceous composition. The reaction of pozzolan with lime already existing in cement or liberated during the hydration process modifies some properties of the cements and the resulting concrete.This research studies the potential of using pozzolan from natural source in Algeria as pozzolanic material. This pozzolan is rarely used in concrete due to the absence of a thorough study of its properties. In order to gain more knowledge on the efficiency of pozzolan concrete, six concrete mixtures: one specimen with Portland cement (control) and five mixtures with 10%, 20%, 30%, 40%, and 50% of replacement of cement by pozzolan were tested. Crushed pozzolan was used as lightweight aggregate (LWA) and natural sand was used in all mixes to produce a lightweight aggregate concrete (LWAC).Fresh concrete mixtures were tested for workability and density. While for the hardened concrete specimens, compressive strength, splitting tensile strength, and flexural strength were determined after 3, 7, 28, 90 and 365 days. A total cementitious materials content of 400 kg/m3 was maintained invariant in all the concrete mixtures. The concrete mixtures were designed for a constant workability expressed with a measured slump of 5±1 cm.The results of this study suggest that the use of pozzolan at 20% of the weight of cement produces the highest strength increase of the mixtures that were tested.