Study On The Mechanical And Durability Of Concrete With High Active Mineral Admixture

With the rapid development of society,the construction of infrastructure is also accelerating,resulting in the increasing demand for cement,but the environmental problems brought by the development are becoming increasingly serious.In order to reduce the amount of cement and protect the environment,metakaolin,ultra-fine fly ash and silica fume three high active mineral admixtures are replaced by cement,compared with the traditional mineral admixtures fly ash and mineral Slag and high active mineral admixtures(metakaolin,silica fume,ultra-fine fly ash)can make concrete have better mechanical properties and better durability,and can be widely used in marine engineering,northwest saline soil area and tunnel engineering.Therefore,through orthogonal test and parallel group test,this paper explores the replacement of cement by high active mineral admixtures alone or by two or three In addition,the durability of concrete with high active mineral admixtures under different curing ages was studied by rapid carbonation test and dry wet cycle test.(1)The orthogonal test shows that the mixing ratio of ternary high active mineral admixture concrete is A3B1C2.If only the splitting tensile strength of concrete is considered,the optimum mixing ratio of high active mineral admixture concrete is A2B1C3.When the curing age of concrete is less than 28 days,metakaolin is the most important factor affecting the compressive strength of concrete.When the curing age of concrete exceeds 28 days,silica fume is the main factor influencing the compressive strength.For splitting tensile strength,metakaolin is the main influencing factor.(2)When the curing age is more than 28 days,the mechanical properties and carbonation resistance of the concrete are higher than that of the concrete with high active mineral admixtures.If the concrete has certain carbonation resistance,it needs to be cured for at least 7 days.When the curing age is less than 7 days,metakaolin and silica fume will increase the carbonation depth of concrete,while ultra-fine fly ash will reduce the carbonation depth of concrete.(3)The addition of metakaolin can greatly improve the resistance of concrete to sodium sulfate solution,but it will significantly weaken the corrosion resistance of concrete to magnesium sulfate solution;the addition of ultra-fine fly ash can improve the resistance to sodium sulfate corrosion and magnesium sulfate corrosion of concrete;the double addition of metakaolin and ultra-fine fly ash has the best resistance to sodium sulfate corrosion Through XRD,SEM,FTIR red spectrum analysis,the main reason for the different damage degree of the two solutions to concrete is the different corrosion products of the two solutions.(4)All kinds of corrosive ions promote and hinder the corrosion of concrete with high active mineral admixtures.Through the comparison of macro and micro morphology of ternary high active mineral admixture concrete in various solutions,it can be seen that single chloride ion has no corrosive effect on concrete,only magnesium ion has a relatively small corrosion effect on concrete,Magnesium ion can promote the destruction of sulfate ion on concrete,while chloride ion can hinder the corrosion of sulfate ion and inhibit the production of ettringite.In practical engineering,special attention should be paid to the areas where magnesium ions and sulfate ions occur simultaneously.Figs:63 tables:26 refs:62...