Physical, mechanical properties and microstructure of concretes made with natural and crushed aggregates: Application in building construction

This paper discusses an experimental work on concrete made from river and crushed sands such as quartzite, granite, gneiss, marble, dolomite, basalt and limestone with an emphasis on physical, mechanical, and microstructural properties of fresh and hardened concrete. This paper is completed by the formulation of three types of concrete with a constant w/c ratio of 0.54: A concrete with 100% gneiss aggregates (CSGG), a mixed concrete composed of river sand and gneiss aggregates (CSGS) and a concrete with 100% basalt aggregates. All the physical and mechanical properties of concretes are depicted at room temperature in this paper used water/cement ratio (w/c) in the range of 0.22 to 0.66. The crushed aggregate is replaced by the river aggregate in concrete. In addition, for the best mechanical properties of concrete, with w/c ratio in the range of 0.36 to 0.45, it is suitable to use up to 65% of crushed sand as partial replacement of river sand. Good results of mechanical properties and handling are obtained in the range of w/c between 0.25 and 0.35 with superplasticizers. Indeed, the high percentages of fine particles in the sand reduce workability, increase w/c and reduce mechanical performance of concrete. Geological nature of rock and its mineral composition have a great influence on the properties of concrete. According to the shape and texture of aggregate, the use of angular form and rough surface lead to the best mechanical properties of concrete