Preparation And Performance Of Foam Concrete With Phosphogypsum

Phosphogypsum(PG) is a waste of phosphoric acid manufacturing by dehydrating process, which is a fine powder with high calcium sulphate content.In China, the amount of phosphogypsum has exceeded 250 million tons with more than 70 million tons of growth rates each year. The unscientific discharge of phosphogypsum not only leads to serious environmental contamination, but also occupies considerable land resource. Hence, it starves for large-scale and low-cost processing technology. Now there are many ways of high value-added utilization,but only used in building materials can achieve the goal of consuming great quantities of PG. “The 12 th five-year plan for building materials” in China makes clear that government encourages the development of the use of industrial waste to produce lightweight construction materials. Foam concrete, a kind of building insulation materials with energy-saving production and less raw materials consumption, can get more favourable. In this work, original PG was used as raw material for manufacture of foam concrete. The large-scale low-cost processing technology of PG to the production of energy-saving wall materials is of great significance.In this work, the matrix of PG- cement- slag and PG- cement- fly ash foamed concrete was studied. A series of technological parameters were investigated and then the relative performances of the product were tested. At the same time, what the role of PG play, and the water resistance, shrinkage,carbonation and heat conduction performance are aslo studied.Results show that, 1. There is a continuous increase in the compressive strength values with PG content increases from 0% to 12%. Later, it is almost in a line down. Most of the PG in the mix are as filler, and there is a small amount of sulfate in the PG also played a role in stimulating calcium silicon materials and generating ettringite to enhance compressive strength. 2. Quick lime yields harmful acidic impurities like soluble phosphorus in phosphogypsum shifting to insoluble salts, which can make the PG specimens coagulating and curing normally. It also stimulates the activity of slag, and at the same time strengthens the hydration reaction of the mix. Accelerated effect of the sulphoaluminate cement is apparent, and the optimum content is 2%, that can make the stable timeof foam consistent with the thickening rate of the slurry. 3.The most excellent content of PG was 45% to 55%, cement to slag ratio was 1, quick lime 4%,sulphoaluminate cement 2%. In the case of mixed without water reducing admixture, the W/S(water to solid ratio) from 0.4 to 0.5 is excellent. 4. Through the orthogonal experiment, the primary and secondary order of influencing factors for PG- cement- fly ash matrix is water to solid ratio, Ca O, PG, cement to fly ash,SAC. 5. Carbonation resistance of PG-cement-slag system is better than PG-cement-fly ash system. Compact system performance of carbonation resistance is better than that of light system. The influence factors of PG foam concrete carbonation resistance are mainly:(1) Aluminum content.(2) Porosity. 6.The thermal conductivity of different density grade met the requirement of a Chinese standard. The lower bulk density(or the larger the water to solid ratio),which leads to the higher porosity, the lower the inflation rate.