Study On The Influence Of Composition Of Binding Material And Temperature And Humidity On The Performance Of Shrinkage Compensated Concrete

This paper relies on the construction project of “Jingtai-Zhongchuan highway airport connection line corrugated steel web steel box composite beam bridge”.Based on the compensation shrinkage mechanism,this paper focuses on the analysis of the influence of the composition of cementitious materials,water temperature and water supply on the strength and limiting expansion rate of Shrinkage-compensated concrete.The hardened paste of cementitious material is taken as the research object.Meanwhile,the hydration process,hydration products and micro-morphology of hardened paste cured at different temperatures and humidities were studied by means of SEM and XRD.The main conclusions of this paper are as follows:(1)Using response surface design(Box-Behnken design),regression analysis and significance test,the mathematical model of interaction between three influencing factors and three response values was established.The proportion of shrinkage-compensating concrete which meets the requirements of engineering strength and deformation can be obtained through the regression model.In addition,expansion agent is not the only factor that determines the limit of expansion rate,and it can be controlled by adjusting the composition of cementitious materials.(2)The development trend and final size between the compressive strength and limited expansion rate of Shrinkage-compensated concrete under different water temperature conditions are significantly different.High temperature water curing can promote the hydration of cementitious materials,and make the early strength and limited expansion rate close to or reach the maximum.However,due to the different sensitivity of calcium oxide expansive agents and cement to temperature changes,the development of strength and expansion is not matched.(3)External water supply is the key to the expansion efficiency of calcium oxide expansive agent in shrinkage compensating concrete with low water-binder ratio.Expansive agent and cement will promote each other in the early hydration stage when the water is sufficient.However,if the water supply is insufficient,the hydration relationship between the two is mutually inhibited.In addition,water shortage will also intensify the competition between expansive agent and cement for water,but expansive agent will take precedence over cement for water,and ultimately the ideal expansion can also be produced.(4)As for shrinkage-compensating concrete with calcium oxide expansive agent,the propotion shall be adjusted according to the different application fields and parts in the project to prepare the concrete that meets the strength requirements and has little difference in deformation.This would realize the coordinated development ofstrength and expension.