Production Process Of Steel Slag Powder And Its Application In Cement Concrete

Steel slag is a byproduct of steel smelting in steelworks,which is about 12%～15%of the steel output.In recent years,with the rapid development of China’s steel industry,the production of steel slag has been increasing by years.The comprehensive utilization rate of steel slag is about 40%.The main mineral compositions of steel slag are the overburned tricalcium silicate,dicalcium silicate,olivine,rhodonite and so on,which are mainly used as road materials,backfill materials,building materials products,ground cement mixture and concrete admixture,etc.Due to the limitation of technical equipment,the low activity and high cost of steel slag restrict the popularization of steel slag powder.In recent years,China vigorously advocates the concept of "clean production",supports the technical transformation projects on the comprehensive utilization of metallurgical slag resources,and implements preferential policies for the emerging industries and products formed by the comprehensive utilization of metallurgical slag.Domestic steel enterprises have made great achievements in the treatment and utilization of metallurgical slag.Many enterprises have transformed from the simple way of recovering to the deep processing with high added value.In order to speed up the comprehensive utilization of steel slag,the research and development project of steel slag powder is put forward in this research,which is of great significance to realize the high value utilization of steel slag.Steel slag powder,as a high active admixture of cement and concrete,is used in the manufacture of cement and concrete to realize the effective utilization of steel slag waste.Aiming at the ultimate realization of the efficient utilization of steel slag as the supplementary cementing material in the construction materials industry,the grinding characteristics of hot disintegration steel slag,morphology and powder characteristics of steel slag powder and properties of steel slag mortar are studied in this paper.The tests of steel slag concrete coordination optimization and the full performance verification of steel slag concrete are carried out as well.The results are as follows:(1)In order to maximize the utilization of steel slag with the premise of no obvious impact on the strength of concrete,the content of steel slag powder in the admixture should be controlled at 20%.When the boiling expansion values meet the requirements that standard is at least not higher than 5 mm,the boiling stability is qualified.(2)The Blaine specific surface area of steel slag powder has a primary exponential decay relationship with grinding time,and the grinding balance fineness is 715 m2 kg1.Compared with the ordinary steel slag,the fine-grained steel slag treated by the technology of hot disintegration has the advantages of low iron content,good grindability,low grinding energy consumption and large output.The cumulative distribution of the granularity of various hot pressed steel slag powder milled at different grinding time is consistent with the typical distribution of RRB.(3)The research on the particle morphology of the steel slag powder shows that with the increase of the granularity of the hot disintegration steel slag,the statistical average value of the ratio of the length to the diameter increases obviously on the whole,and the sphericity of the particles becomes worse.With the increase of specific surface area,steel slag powder presents the same law of change with the bigger rest angle of steel slag powder and the decrease of the natural packing density and compression density.The result of the shearing test shows that the steel slag powder belongs to the Coulomb powder with relatively low cohesion.The larger internal friction angle of hot disintegration steel slag powder indicates that it has greater cohesiveness.(4)After 80 minutes of grinding,the activity index of the steel slag powder can meet the requirements of the first-grade powder.The compactness,freeze-thaw resistance and wear resistance of the composite cementitious materials mixed with steel slag powder are all significantly improved.When 25%cement is replaced by equivalent steel slag powder,the rate of water absorption,the loss of freeze-thaw cycle compressive strength and wear of test are reduced by 3 6%,76%and 67%,respectively,which is conducive to the preparation of high-strength,high-density and wear-resistant materials.(5)According to the test results of concrete preparation,the mix proportion is that steel slag powder replaces 20%of S95 mineral powder,steel slag sand replaces 40%of medium sand and steel slag stone replaces 20%of crushed stone.The mechanical properties of steel slag concrete are better than that of reference concrete or similar with it;the impact and wear resistance of steel slag concrete is better than that of ordinary concrete,with the improvement of 4.5%.The durability of steel slag concrete is basically similar to that of the reference concrete,the frost resistance is slightly poor,and the impermeability is worse than that of the reference concrete,but the impermeability grade is greater than P10.With the development of curing age,the durability of steel slag concrete will be improved.