Effect Of High Volume Slag Powder On The Properties Of Cement Cementitious Material

The use of slag powder in cement and concrete engineering,has significantly improved the mechanical properties and working properties of the cementitious materials.As an industrial waste,the recycling of slag not only meets the requirements of sustainable development,but reduces the use of cement which has high energy consumption and high pollution.Because of the potential activity of the slag powder,simply mixing with cement is difficult to have a good performance.Especially when the content of slag powder is high,its early mechanical properties are difficult to meet the standard.Nowadays,how to replace cement with large amount of slag powder in industrial production,with a better early mechanical properties and durability,has become the focus of people's attention.In this paper,the influence of large amount of slag powder on the mechanical and physical properties of P.O 42.5 Portland cement was studied.According to the results of the mortar strength,70% of the amount of slag powder was selected,and several activators were chosen to stimulate the early strength of composite cementitious material.The results show that with the increase of the slag powder content,the early strength of the composite cementitious material decrease gradually,and the strength of 28 d increase first and then decrease.The addition of Na2CO3 makes the cementitious material condense faster and have a higher early strength,but the subsequent strength growth becomes slow.The addition of Na2SO4 has a better comprehensive improvement of the mechanical properties of the cementitious material.The strength of the cementitious material at different ages have reached the standard of P.O 42.5 Portland cement,with the addition of Na2SO4 and Ca(OH)2.According to the results of mortar strength test,several representative groups were selected to analyze the microscopic properties,including XRD and SEM analysis.The results show that the content of Ca(OH)2 in the cementitious material is greatly reduced by the incorporation of the slag powder,and the addition of Na2SO4 make the structure of cementitious material well-distributed and more compact,which is effectively stimulated the potential activity of slag powder.