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With a view to implement sustainability concepts (namely, use of locally available materials and industrial by-products) in the concrete construction industry, the possibility of use of crushed stone fine aggregate as replacement to river sand is explored in this paper. Towards this, tests have been carried out on concrete cubes and concrete cylinders. The effect of variation in percentage replacement of river sand with crushed stone fine aggregate on the mechanical properties is studied. In order to popularize the locally available material for the construction of shear critical concrete structures (viz. flat slabs, foundation of heavy structures), the Mode -II fracture behavior of the considered concrete is studied using DCN (Double Central Notched) specimens with different notch to depth, (a/w), ratios of 0.3, 0.4, 0.5 and 0.6. For each (a/w) ratio five different percentage replacements (viz. 0, 25, 50, 75 and 100%) are considered. The study indicates that both cube compressive strength and split tensile strength increases with the increase in percentage replacement up to 50% and then gradually decreases. A similar observation was made with respect to the Mode -II fracture energy also. It is noted that the strengths of concrete even with 100% replacement are higher than the concrete with 0% replacement suggesting that the locally available crushed stone fine aggregate can be considered as an alternative to the river sand. Keywords: cushed stone fine aggregate, DCN (Double Central Notched) specimen, notch to depth ratio, Mode -II fracture energy

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At present all the constructions are executed with conventional granite aggregate concrete. If the granite aggregate is reduced by replacing it partially and fully by Metakaolin pellets as aggregate, the behavior and strength properties are interesting to be investigated. In this study an attempt has been made to use the Metakaolin as the basic ingredient in preparation of artificial pelletized metakaol in aggregate using lime and cement as binders. In the present experimentation, addition of Metakaolin pellets replacing the conventional granite aggregate in percentages of 0, 25, 50, 75 and 100% by volume of concrete and also adding the crimped steel fibre in percentages of 0.50, 1.00, 1.50 and 2.00% by weight. The properties such as compressive strength, split tensile strength, modulus of elasticity and flexural strength are studied by casting and testing around 240 samples consisting of 60 numbers of plain cube specimens of size 150x150x150 mm, 120 numbers of cylinders of size 150mm diameter and 300mm height and 60 numbers of plain beams of size 500x100x100 mm for testing after 28 days of curing.

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