The utilization of concrete has been increasing day by day due to rapid industrialization, urbanization and infrastructural developments all over the world. A huge quantity of natural coarse aggregate, natural river sand and also cement is needed in order to fulfill the increasing demand. This is causing a rapid depletion of the natural resources, be it rocks for coarse aggregate or the natural river sand and need to be conserved urgently. It is also found that during the production of cement,

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... n equal amount of carbon dioxide is also produced and to overcome the ill effects caused on the environment, attempts have been made to replace the natural resources by some other materials such as recycled aggregates and ROBO sand and cement by some other binding material like bentonite. This work reports the results of an experimental study on the mechanical properties of concrete produced with recycled coarse aggregate (100%), ROBO sand (100%) and partial replacement of cement with Bentonite (0%, 5%, 10%, 15%, 20%, 25% and 30% replacement). The compressive strength, split tensile strength and flexural strength of this concrete was tested by casting cubes of size 150 X 150 mm, cylinders of diameter 150 mm and length 300 mm and beams of length 500 mm and cross sectional dimensions 100 X 100 mm size respectively and testing was done at 7 and 28 days. The fresh and harden concrete properties were analysed after 28 days of curing and found that at 20% replacement of OPC with bentonite along with super plasticizer was optimum and gave compressive strength of 44.0 N/mm2 which is an increase of about 17.5%.Similarly the split tensile strength is found to12% more than at 0% bentonite.. The workability was a problem initially but was able to achieve after addition of super plasticizer.