The concrete is the second largest consumed material by human after the water. Cement is the main ingradient in concrete. In the most general sense of the word, cement is a substance which sets and hardens independently, and can bind other materials together. The production of one tonne of OPC consumes about 1.5 tonnes of raw material due to this the cement raw materials are exhausting as quickly as possible. It causes increasing scarity of natural materials and causes environmental problem by

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... mission of co2 and other gases. By replacing pozolanic materials like flyash, silica fume and phosphogypsum etc with cement in concrete it is used as economical, reduces environmental pollution and scarity of cement making raw materials. Phosphogypsum is a by-product in the wet process for manufacture of phosphoric acid (ammonium phosphate fertilizer) by the action of sulphuric acid on the rock phosphate. And Fly ash is a by-product of the combustion of pulverized coal, usually from coal-fired power plants. The disposal of phosphogypsum and fly ash are serious environmental problems. This problem along with rapid depletion of cement making materials, environmental pollution associated with the manufacture of cement and its increased cost can be solved to some extent by replacing certain quantity Phosphogypsum generation in the Country is about 11 million tonnes per annum. The RTPP located at muddanur in Kadapa district produces about one million tons of fly ash every year. The main aim of this study is to investigate the influence of phosphogypsum (PG), fly ash (FA) on mechanical properties and durability properties of concrete. The use of partial replacement of opc by wastes favoured concrete production due to their advantages in improving some of the properties of concrete. The experiment consists of testing partially replaced cement with phosphogypsum in fly ash concrete, Using 0%, 4%, 8% and 10% replacement of cement with phosphogypsum and maintaining fly ash at constant 25% all the mixtures were prepared. Based on the experimental investigation conducted and the subsequent analysis of test plain concrete (PC) is more than 30%. The percentage increase in split tensile strength at 8% phosphogypsum content, when compared with conventional concrete is around 60%. Maximum strength and lowest water penetration of fly ash concrete are achieved at 8% replacement of opc with phosphogypsum.