Study On Composition,Structure And Properties Of Cement And And Concrete With Steel-making Slag Powder Mineral Additive

Mineral additives have become one of most important compositions in the modern cement and concrete with development and progress of concrete technology, so exploitation of new high efficiency mineral additives has an important branch in the study of cement and concrete in order to meet development and requirement of modern concrete. As a new mineral additive of cement and concrete, ground steel-making slag powder has quite high activity and its activity is obvious higher first grade fly ash and close to blast furnace slag. Furthermore, its distribution is very wide and quantity is quit plenty in our country. Therefore, it has quite high value of application and study.In this paper based on the study of composition structure and properties of steel-making powder, relationship and laws between composition, structure and properties of cement and concrete with steel-making powder are revealed by testing composition and microstructure of hydration products, physical properties, workability and comprehensive durability of cement and concrete with steel-making slag powder. It provide theory reference and technology support for application and spread of steel-making slag powder mineral additive.Composition and structure feature of steel-making slag powder are investigated systematically and relationship between composition and cementitious property of steel-making slag is discussed. Results show that basic parameter can determinate content of C3S in steel-making slag powder; however, it can not determine cementitious property of steel-making slag. Cementitous property of steel-making slag powder is determined by mineral composition calculated from chemical composition and treating process, which means intrinsic cementitous property of steel-making slag is determined by total content of active mineral composition, C2S, C3S, C4AF and C3A, and content of Ca(OH)2 marking loss of active mineral.Activity factor is presented for evaluating cementirous property of mineral additives by certain derivation and numerical analysis. Calculated results of activity factor show that activity of Soudu steel-making slag powder is highest, activity ofWuhan steel-making slag powder is higher and activity of Shanghai steel-making slag powder is lowest because of its treating process. Generally speaking activity of steel-making slag is higher than first grade fly ash.Influence of special surface and particle morphology of steel-making slag powder on cementitous property is studied by experiment. Results show that cementitous property of steel-making slag powder increase with increase of its special surface, but increase of cementitous property is not obvious when its special surface is beyond 500 m2/kg. Therefore it is reasonable that special surface of steel-making slag powder is controlled in the rang between 450-500m2/kg. Furthermore, when special surface of different steel-making slag powders are close, steel-making slag powder, which surface is attached lot of fine particle powder or which degree of roundness is high, has higher cementitous property.Effect of MgO, f-CaO, FeO, RO phase and metal Fe in steel-making slag powder on soundness of cement is investigated by boiling test, steam test and autoclave test. Results show that MgO, FeO, RO phase in steel-making slag do not cause soundness problem of cement. Generally speaking, f-CaO and metal Fe are main factors which cause soundness problem of steel-making slag powder, so their content must be limited strictly restricted. Content of f-CaO must be limited fewer than 3% and content of metal Fe must limited fewer than 2%.Composition feature of hydration products of cementitous materials with steel-making slag powder is studied by XRD and DTA-TG and influence of mineral additives on hydration rate also investigated by chemical bond water of ultimate hydration products. Results show that C2S, C3S and Ca(OH)2 in hydration sample with steel-making slag powder are more than those in hydration sample with fly ash or blast furnace slag. Sequence of capacity bonding water...