Abstract:
Concrete is composed essentially of cement, aggregates and water. In some cases an admixture is added, generally for the purpose of entraining air, but occasionally for special reasons such as modifying setting time or reducing water content. Lightweight aggregates are available and in use in other parts of the world in the construction industry. These are either processed in a rotary kiln / Sintering grate or natural materials
such as pumice and scoria. The study indicates that considerable knowledge has been accumulated on industrial processed lightweight aggregates for use in concrete, but more study needs to be done to determine the effects of other locally available and
natural lightweight aggregates like crushed limestone on physical and mechanical properties of concrete. This was done by partial replacement of the granitic aggregates with crushed Limestone as coarse aggregates. The replacement proportions were varied from 0%, 25%, 50%, 75%, and 100% by weight of natural aggregates. Tests results of this work are of importance in assessing the mechanical properties determined through tensile splitting tests, flexural tests and compressive tests at 3, 7, 14 and 28 days. Crushed limestone (Coral stone) and sand locally available in Mombasa and in specific river sand from Malindi, Limestone Aggregates from Coast Calcium Ltd in Kwale and the Natural Coarse aggregates from Kokotoni where used in this research. This may lead to better and more economical Light weight aggregate for manufacture of masonry units and concrete.
