Characerisation of natural pozzolan of "djoungo" (cameroon) as lightweight aggregate for ligtweight concrete

Abstract

Cameroon has an appreciable quantity of volcanic pozzolanic materials, but a very low proportion is used as cement additions. These materials are abundant but are rarely or very little used because of the lack or limited of studies to develop, promote and popularize its use naturally as an addition or as aggregates in the production lightweights aggregates concretes. The main objective of this study is to promote these sources of low environmental impact construction materials. Its aim is to characterize and value the natural pozzolan source "Djoungo" as lightweight aggregate for lightweight concrete. Analyses and tests conducted in this study were performed on aggregates produced from this resource. It's concern the chemical and mineralogical analysis, the production of aggregates (Crushing and Sieving), physical properties (appearance and shape, natural water content, porosity, density and water absorption) and mechanical (Compressive strength, tensile strength and elastic modulus) to optimize the mechanical properties and durability of lightweight aggregate concrete obtained from this resource. Chemical composition is according with ACI (American Concrete Institute) standard on natural pozzolans. Two categories of lightweight aggregates were obtained. Those derived by simply sieving have more than 82% of rolled particles and those obtained after crushing have more than 84% of flatter and elongate particles. The bulk density is ranging around 560-820 kg/m3 and specific density around 1,580-2,730 kg/m3. The water absorption after 48 hours is around 12 to 28% and depending of grading class.