Open AccessEffect of curing temperature and particle size distribution on unconfined compressive strength of raw and treated fly ash-lime modified phosphogypsum waste
Author(s) -
Tebogo Mashifana,
Felix Okonta,
Freeman Ntuli
Publication year - 2019
Publication title -
iop conference series. materials science and engineering
Language(s) - English
Resource type - Journals
eISSN - 1757-899X
pISSN - 1757-8981
DOI - 10.1088/1757-899x/652/1/012044
Subject(s) - phosphogypsum , compressive strength , fly ash , lime , raw material , curing (chemistry) , phosphoric acid , materials science , waste management , cement , environmental science , environmental pollution , pulp and paper industry , composite material , metallurgy , chemistry , engineering , environmental protection , organic chemistry
The Voluminous quantity of phosphogypsum waste is generated by phosphoric acid manufacturing industry and end up being landfilled, resulting into environmental pollution. This study was done to determine applications for raw and treated waste phosphogypsum in building and construction, to determine the best conditions to produce the final product. Two readily available wastes namely phosphogypsum and fly ash were used and blended with hydrated lime. Best strengths was obtained from a mixture of phosphogypsum-lime-fly ash specimens were at elevated temperatures. The strengths obtained at the temperature of 80°C were above the 3.5 MPa permissible strength for building masonry with unconfined compressive strength up to 4.8 MPa. At lower temperature of 40°C the optimum strength obtained was at the minimal phosphogypsum content of 30%. The optimum strength was achieved at the PG content of 50% for raw PG and 60% for treated phosphogypsum. The strengths obtained for the treated phosphogypsum were lower than the minimum permissible load bearing strength due to the non-uniform particles distribution and the presence of impurities and forces of adhesion between citric acid and phosphogypsum. Increasing the curing temperature also reduced the radionuclides initially present in the raw PG without any prior treatment.