Behavior of Various Concrete Mixes with Inclusion of Recycled Coarse Aggregates Based on Durability Point of View

Abstract

Cement concrete is the most extensively used construction material in the world with about six billion tons produced every year. It has emerged as the dominant construction material for the infrastructure needs of the 21st century. Aggregate is one of the main ingredients in producing concrete i.e. 75% of the concrete mass. The strength of the concrete produced is dependent on the properties of aggregates used, hence there is huge demand for this material. In order to reduce the use of natural aggregates from natural resources, the use of recycled aggregates in concretes is an interesting solution. It helps in reducing the cost of concrete manufacturing and also has numerous indirect benefits such as reduction in land-fill cost, energy saving, and protecting the environment from possible pollution effects. Durability and strength are two most important criteria for any concrete structures. One of the main causes of deterioration in concrete structures is its exposure to temperature variations mainly due to solar radiation and harmful chemicals that may be found in nature such as in industrial effluents. The most aggressive chemicals that affect the long term durability of concrete structures are the magnesium, sulphates and chlorides. These chemicals in presence of water increases the porosity of concrete and leads to loss of weight and strength. Hence this paper investigates the effect of thermal cycles and chemical attack on M20 & M25 grade cement concrete in partial replacement of natural aggregates with recycled aggregates with proportion of 10%, 20% and 30%. The effect of temperature variations were studied by analyzing loss in compressive strength after applying various thermal cycles on concrete cubes at 60o C and 90 o C. The chemical resistance of the concretes was studied through chemical attack by immersing concrete cubes in 5% MgSO4 , H2SO4 and HCl solution and loss in strength and weight were measured at 7, 28, 60 and 90 days. The result shows possible use of RCA as 20% for both M20 & M25 grade concrete, and resistance to thermal cycles and chemical attack shows reduction in strength and weight with time.