Experimental Study On Admixture Of Precast Concrete Early Strength Without Steam Curing

With the rapid development of China’s modernization,precast concrete has become one of the most important development directions of concrete and cement products industry.However,due to the early strength of precast concrete is generally not high,resulting in low turnover rate of mold,greatly affecting the production efficiency.As a commonly used technology to improve the early strength of steam curing,there are many problems,such as harmful gas emissions,crack formation and strength loss.Therefore,the research on the early strength of precast concrete without steam curing can avoid the problems caused by steam curing,improve the production efficiency and save the cost,which is of great significance to the development of housing industrialization.Polycarboxylate superplasticizer have high water reducing rate,increase the strength of growth rate and other advantages;early strength agent can accelerate the speed of setting and hardening of concrete,and the price is low,especially in winter by adding early strength agent method to improve the early strength of concrete.The objective of this paper is mainly through the study of early strength admixture of polycarboxylate superplasticizer and early strength agent of the combination of the two,the optimal mix ratio,to meet the C40 precast concrete in various curing temperature curing and early strength to meet the engineering requirements of the stripping strength.The conclusions are as follows:the acid ether,sodium methylacrylsulfonate substitution rate,synthesis catalyst and oxidant and reductant dosage respectively,the single variable experiments,variation of fluidity and compressive strength with various factors are found out,and through analysis,respectively,to determine the best value of four important factors,on the basis of on the synthesis of PC-ZQ type early strength admixture.From the three aspects of the adaptability of cement,the fluidity of cement mortar and the compressive strength of cement mortar,the PC-ZQ water reducing agent is compared with the standard water reducing agent and the early strength water reducing agent.Through five groups of early strength agent dosage experiment,found the concrete fluidity and compressive strength respectively with sodium thiosulfate,calcium formate,triethanolamine,changes of sodium nitrite and sodium sulfate content of selected three kinds of early strength agent was better,the best ratio was determined through orthogonal test by composite early strength agent,and find out the relationship between various factors.Based on the experiment,the optimum mix proportion of C40 precast concrete in different seasons was discussed,and two kinds of composite additives,ZQ-C and ZQ-D in winter,were developed,respectively,for Yu Chunqiu.In order to save the cost and adjust the proportion of mineral admixtures,the basic law of the variation of the slump and compressive strength with the mineral admixture ratio was found.Under the curing temperature of summer,it can meet the requirement of early strength without adding early strength agent,only relying on PC-ZQ early strength polycarboxylate superplasticizer.Finally,through the test,the optimum mix proportion of the early strength concrete can be achieved in the different seasons.