Study On Mechanical Properties Of Cement-desulfurization Gypsum-fly Ash Composite Cementitious Material

Solid waste desulfurization gypsum and fly ash two industry is widely used in practical engineering.For the use of desulfurization gypsum are mainly in the production of building gypsum material.Fly ash is mainly used in our country are also building materials products.However,cement,desulfurization gypsum and fly ash three composite made of composite cementitious material in this study is not thorough and comprehensive.Based on the composite cementitious material,it has the characteristics of light weight hardening and fast speed.And the latter because of the composite material has certain water resistance and high strength characteristics.n this paper,the fluidity,water resistance,unconfined compressive strength and accelerated carbonation experiment of composite cementitious materials.And strength characteristics and durability of composite cementitious materials was studied in this paper.And microcosmic experiment.This paper mainly discussed the following contents:(1)Analysis of the gypsum and fly ash to replace a large number of cement,reduce the effect of cement content on the fluidity of cementitious materials.The experimental results show that: The cement is gypsum and fly ash instead of increasing liquidity when the composite cementitious materials become worse;(2)Summary of the three proportion is not the same,the water resistance experimental of composite cementitious materials.The experimental results show that:When the cement accounted for 70%,accounting for 15% of the desulfurization gypsum and fly ash accounted for 15%,the coefficient of softness of the material reached the maximum of 0.81.When the cement content is reduced,the coefficient of softness of the material is proportional to the cement content.(3)Analysis of different ratio,composite cementitious material of unconfined compressive strength characteristics.Thus analyze the effect of different ages on the strength of composite cementitious material.The experimental results show that: With the increase of curing age,the strength of growth is increasing,the content of cement decreases,and the strength of integral compressive strength decreases.The strength of fast test block with high desulfurization gypsum content is fast at the later stage of curing.(4)To investigate the carbonation time is not the same,the strength characteristics of development trend of carbonization and carbonation resistance of composite cementitious materials after.The experimental results show that:When the cement ratio is greater than 50%,with the increase of accelerated carbonization time,the increase rate of compressive strength is the fastest at 3~7 days of carbonization time.Cement content for the compressive strength of 90% specimens after 14 days of accelerated carbonation reached 80 MPa,while the normal curing strength of the specimen is about65 MPa.But when the cement content is 50%,the strength of the 3 days before carbonization is greater than that of the normal curing test,but the later strength decreases.(5)Through microscopic experiment,XRD test and SEM test of the carbonized samples.Analysis of composite cementitious material internal microstructure change after carbonation.To explain the macroscopic properties from the microscopic angle change.