Abstract
A million tons of Phosphogypsum (PG) is stacked in the environment every year and is progressively considered an asset. South African construction industry is expanding as a result of infrastructural developments in the country, the reuse of PG in this industry is considered for recycling and reducing the stacks in landfills. Phosphogypsum is known for its limited ability to use in cement industry due to its phosphorus and radionuclides impurities. This study was conducted to reduce these impurities and investigate the probability of PG application in building and construction. Leaching of PG with citric acid was conducted whereby a relative proportion of P2O5 and radionuclides was reduced in the material, constituents which contributes to strengths reduction. Optimum moisture Contents and maximum dry densities were determined for various PG content mix designs in which Lime and Fly Ash were added to stabilise PG material. The composites were compacted at various moisture contents and cured at low and elevated temperatures of at 40 °C and 80 °C for 4 days. The results obtained shows that for unconfined compressive strengths; the composites produced from PG, and cured at high temperature qualified for the use in construction industry.
Highlights
Environmental problems do take a lead in the reported crisis and threatens the existence of humanity in the near future
The main targeted impurity was phosphorus and purification was successfully achieved as the relative proportion of P2O5 decreased by an enormous 34.7%
The relative proportion of F and total radionuclides were decreased, indicating that these components had a significant reaction with Citric acid concentration reducing the impurities and rendering PG more environmentally friendly by reducing the level of radioactive particles
Summary
Environmental problems do take a lead in the reported crisis and threatens the existence of humanity in the near future. Sustainable products and processes is a major problem in the developing country like South Africa. Engineers have to find new ways to recycle and re-use all the alleviating percentage of accumulated by-products. South Africa has limited resources and this makes it a necessity for the adoption of a number of policies, such as pollution prevention, and recycling of waste material for better use. South Africa has a highly developed domestic and export oriented phosphate industry, with the largest igneous phosphates deposits located in Phalaborwa in the northern province of the country [1]. Residual deposits of Phosphogypsum are readily available in large quantities in South Africa and currently are landfilled or pumped into the sea [2]. Waste Phosphogypsum is produced as a by-product during the treatment of phosphate concentrates with sulphuric acid to produce phosphoric acid according to the following simplified chemical reaction [3]
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