| Portland cement is the most widely used basic material in the construction industry.As a product with high energy consumption and high carbon emissions,its large use has also brought serious environmental problems to social development.Therefore,it is an urgent problem for the construction industry to seek a green and environmental protection material to replace Portland cement to reduce environmental pollution.Alkali activated cementitious materials are mainly a new type of energy-saving and environmental protection materials which are made of slag,metakaolin,fly ash and steel slag.Under the basic activator,the chemical bond recombination is realized by polymerization.Compared with cement,alkali activated cementitious materials have excellent properties such as low carbon emission,turning waste into treasure,rapid setting,early strength and corrosion resistance.However,alkali activated cementitious materials also have some problems,such as large drying shrinkage,poor slurry setting time and fluidity,poor resistance to plastic deformation and many shrinkage cracks,which limit their application.Therefore,the strength and shrinkage properties of slag steel slag composite cementitious materials were studied by adding different volume of basalt fiber and PVA fiber with slag and steel slag as raw materials.The conclusions are as follows:(1)Through the orthogonal experiment design,the range analysis of 3d,7d and 28d compressive strength and flexural strength of composite cementitious material was carried out,and the optimum mix proportion was determined.When the alkali activator modulus was 1.20,the water binder ratio was 0.50,the concentration of alkali activator was 0.22,and the binder sand ratio was 0.60,the slag steel slag based composite cementitious materials had better mechanical properties.(2)The flexural strength of the composite cementitious material first decreased and then increased with the increase of steel slag content,but it was smaller than that of the control group as a whole;with the increase of PVA fiber and basalt fiber content,the flexural strength of the composite cementitious material first increased and then decreased.When the PVA fiber and basalt fiber content were 0.3%and 0.2%respectively,the flexural strength was the largest.The compressive strength decreased and then increased with the increase of steel slag content,and increases first and then decreased with the increase of PVA fiber and basalt fiber content.(3)The elastic modulus of composite cementitious material first decreased and then increased with the increase of steel slag content.When the steel slag content was 30%,the elastic modulus of composite cementitious material was the minimum.The elastic modulus of composite cementitious material was the same with the content of PVA fiber and basalt fiber,which first increased and then decreased.And the elastic modulus of composite cementitious material was the maximum when the content was 0.3%.The effect of basalt fiber reinforced composite cementitious material was better than PVA fiber.(4)The drying shrinkage rate of composite cementitious materials first increased and then decreased with the increase of steel slag content.The early shrinkage rate increased rapidly,and then decreased and tended to be stable after 14d.The effect of two kinds of fibers on the drying shrinkage rate was similar to this.In addition,the drying shrinkage of composite cementitious materials was closely related to the drying water loss.When the water loss was more,the drying shrinkage was also larger.With the increase of steel slag,the autogenous shrinkage first decreased and then increases.When the steel slag content was 20%,the autogenous shrinkage was the smallest.With the increase of basalt fiber content,the autogenous shrinkage first increased and then decreased.With the increase of PVA fiber content,the autogenous shrinkage first decreased and then increased.When the steel slag content was 0.3%,the 56 d autogenous shrinkage was the smallest. |
PDF Full Text Request