Study On Phosphate Tailings Applied To Building Materials

The rapid economic development has led to the excessive consumption of resources and increasingly serious environmental problems. The exploitation of mineral resources is very obvious. Low utilization of mineral resources in China has resulted in serious waste of resources. Tailings emissions are growing at an alarming rate every year. Because of piling directly in the tailings pond it takes up a lot of land resources, and the annual maintenance cost is very high. So recycling tailings and secondary use of tailings is extremely important significance.In this paper, we have studied the phosphate tailings which are discharged by Yunnan Phosphate Cooperation. The main phases of phosphate tailings contain apatite, quartz and dolomite by X-ray diffraction analysis. With combining other local raw materials we have explored the three ways of comprehensive utilization of phosphate tailings. They are phosphate tailings as inert filler for preparing construction materials, studying on calcining and grading phosphate tailings and calcining phosphate tailings used in preparing steam-cured brick. We have made systematic experiments and analyzes with the above three methods and get the following conclusions.We have successfully prepared steam-cured brick, foam concrete and lightweight wall plate with phosphate tailings which act as inert filler. By studying various technological parameters and molding we have obtained the best ratio of raw materials. With the aid of XRD and SEM, we have studied the reaction process and mechanism.Through calcining, milling and sieving phosphate tailings we achieve the phosphorus enrichment. After900℃calcining,40min ball-milling and sieving phosphate tailings the percentage content of apatite increased to60.6%in the material below200mesh. The percentage of phosphorus pentoxide content increased to25.61%. Compared the percentage content of raw mine apatite increased by20%, the percentage of phosphorus pentoxide is increased by8%. And that the finer the phosphate tailings particle is, the more the content of apatite in phosphate tailings is, wherein the greater the percentage of phosphorus element.We have studied the process parameters in preparing steam-cured brick which the calcined phosphate tailings act as cementitious material, and have tested and analysised the physical properties of the prepared steam-cured brick. With the aid of XRD and SEM, we have studied the reaction process and mechanism. Come to the optimum ratio: cement-sand ratio is3:7, water-cement ratio is0.45, and the molar ratio of CaO/SiO2is from1.27to2.06. The molding pressure is20MPa. This formulation does not mixed with cement, compressive strength of steam-cured brick can reach50MPa.