建築工学技術

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A Comparative Study of Concrete Strength Using Metamorphic, Igneous, and Sedimentary Rocks (Crushed Gneiss, Crushed Basalt, Alluvial Sand) as Fine Aggregate

Mambou Ngueyep Luc Leroy, Tchapga Gniamsi Guy Molay, Ndop Joseph, Fofe Meli Colince and Ndjaka Jean-Marie Bienvenu

A comparative study of the technical and economic performances of hydraulic concretes based on three sands with different geological nature has been investigated in this work. Sand from crushed basalt (SB), sand from crushed gneiss (SG) and sand from the river Sanaga were used for the formulation of these concretes. The formulation of these concretes was carried out according to the method of ‘Dreux-Gorisse’. The results of the analysis show that concrete made from crushed basalt (CSB) has very good mechanical strengths (34 MPa at 28 days) followed by concrete made with alluvial sand (CSS), (24 MPa at 28 days) and finally concrete made from crushed gneiss(CSG), (22 MPa at 28 days). This is due to the fact that basalt is a compact rock, hard, tough and also consists of hard minerals such as olivine, plagioclase, clinopyroxene. Nevertheless concretes made with these sands are less malleable and have blemishes after stripping due to the angularity and very sharp edges of grains of sand. Fresh concrete (CSS) prepared with river sand is more malleable than the CSB concrete and CSG concrete. Besides the technical aspect, due to the cost of transport and the scarcity of river sand, concretes made with alluvial sand is more costly (49.893 FCFA/m3 of concrete) compared to concretes made with crushed gneiss and basalt costing 47.053 FCFA and 46.854 FCFA/m3 , respectively. In view of these results, it is therefore possible to replace river sand with quarry sands in the production of concrete and then reduce the environmental problems generated by the overconsumption of alluvial sand.