Preparation Of Low-clinker Cement With Steel Slag And Application In Concrete

With the continuous development of China’s infrastructure,the consumption of cement as one of the indispensable raw materials is increasing rapidly,the pollution problem brought by cement production to the environment,it is becoming more and more serious,long-term development will seriously pollute our living environment,therefore from the origin of cement,break the traditional pattern of cement production,optimization of concrete components,the steel slag powder as raw material instead of clinker cement,cement clinker production is solved in the process of cement clinker calcined brings huge harm to the environment,al eviates the pollution of land and water resources caused by the accumulation of steel slag solid waste.In this paper,the hydration mechanism of steel slag cementit system was studied by grinding and activation of steel slag powder.The steel slag powder was used in the preparation of Low-clinker cement,and the Low-clinker cement with Steel slag with42.5 strength grade was prepared and applied to concrete.The details are as follows:（1）With the increase of grinding time,the specific surface area of steel slag powder increases gradually.Through the strength test and particle size analysis of cement mortar,the optimal grinding time of steel slag powder is determined to be 75min initial grinding and10min regrinding（2）One component activator was selected to activate the steel slag powder,five kinds of activator were selected for orthogonal experiment to activate the steel slag powder,the activator of steel slag powder was prepared,including 0.5%Na₂SO₄,0.7%Ca SO₄,0.2%Ca（OH）₂,0.25%Na Al O₂ and 0.03%TEA.（3）The peak values of hydration heat temperature curve and hydration heat release rate curve of steel slag powder gelatinization system after excitation were higher than that of steel slag powder before excitation,but lower than that of cement,and the wear amount of cement mortar decreased by 4.4%compared with cement group.After excitation by SEM analysis shows that steel slag powder in the 3 d hydration products C-S-H gel from the mesh to shape of clusters,the generated AFt crystal more bulky,the decrease in the number of Ca（OH）2 crystals,28 d hydration products in tabular form C-A–H crystal,AFt crystal quantity increased,volume change,gel ing system internal more dense,beneficial to the improvement of the strength.（4）Gypsum,kuangfen,three kinds of mineral admixture of fly ash and steel slag powder mixed is advantageous to the compressive strength of steel slag powder gel system,to improve the steel slag powder of mineral powder and steel slag powder mixed gel system optimal intensity,through the orthogonal experiment was 42.5 grade Low-clinker cement with Steel slag,mixture ratio of clinker:SAC:gypsum:steel slag powder,mineral powder=31:3:31:31,various performance all conform to the requirements of the specification;XRD and SEM were used to analyze the hydration products of Low-clinker cement at various stages.The hydration products of Low-clinker cement were AFt crystal,C-S-H gel and C-A-H crystal.With the increase of hydration phase,globular and netted C-S-H gels are transformed into clusters,and hexagonal crystal oid C-A-H crystal are formed,while AFt crystals increase in number and cover on the matrix,forming A compact structure.When it is applied to concrete,it is found that clinker cement concrete has a higher initial slump than Mengxi P·O42.5 cement coagulation,better wrapping performance to stones and better wear resistance.