Study On The Mechanical Properties Of Steam Curing Concrete Under The Condition Of Film Mulching

Steam curing has many advantages,such as improve the early strength of concrete and accelerate the turnover rate of the mold.It is the common used way for making concrete prefabricated components.Film mulch steam curing is covers a layer of film on the surface of concrete prefabricated components and keeps constant temperature steam in the membrane which is an easy way in the steam curing method.In this paper,we select the C30 concrete for the study which is often used in prefabricated components.In this experiment we use film mulch steam curing,considering the ratio of water to cement,water reducing agent and mineral admixture,the concrete specimens are tested under different ages.the main research contents and conclusions are as follows:(1)Consider the local aggregate parameters,use volume method design the steam curing concrete mix proportion based on Bowromi formula.Use mapping method get the mixing ratio of steam curing concrete was obtained.Combine the electron microscopy test observe the hydration product of concrete,analysis the compressive strength and splitting tensile strength of Stripping strength at the age of 3d,7d,28 d.The results show that: Be based on the compressive strength at 28 d age,the water cement ratio is 0.51,the concrete strength requirement can be satisfied and the low water binder ratio can promote the growth of compressive strength and splitting tensile strength of autoclaved concrete,and accelerate the hydration reaction of concrete 7d~28d.(2)Add polycarboxylate superplasticizer with cement quality of 0.2%,0.4%,0.6%,0.8%,and 0.2%,0.5%,0.8%,1.1% FDN water reducing agents.Make concrete block.Analysis the variation law of compressive strength and splitting tensile strength,the results show that: The optimum dosage of polycarboxylate superplasticizer is 0.4%,and the optimum dosage of FDN is 1.1%,Compared with FDN water reducing agent,the change of the amount of polycarboxylate superplasticizer has great influence on the strength of concrete.When the amount of polycarboxylate superplasticizer is more than 0.4%,the mechanical properties of concrete decrease obviously.(3)Single-doping fly ash,slag powder,silica fume instead of different proportions of cement and at the replacement rate of 20% under the condition of fly ash-slag powder and fly ash and silica fume,make concrete block,combine the state of hydration products in concrete was observed by SEM,analysis the variation law of compressive strength and splitting tensile strength of different age blocks,the result shows that:Fly ash can reduce the mechanical properties of concrete,slag powder replacement rate was 20% when the mechanical properties of concrete,silica fume replacement ratio is 8% when the mechanical properties of concrete are the highest;fly ash and slag powder ratio of 1:1 was the highest strength,fly ash and silica fume ratio of 6: 6 strength is the highest.(4)Base on non statistical methods,analysis the strength of concrete under film mulch steam curing satisfied the design strength consider the cost,the optimum dosage of mineral admixture was analyzed under the condition of single admixture and compound addition.The results show that the economic efficiency of concrete is the best when the replacement rate of single slag powder is 40%.under the replacement of 20%,the ratio of fly ash and slag is 4:1,the economic efficiency of concrete is the best.