| In this paper,based on the Zhongshan West Ring Expressway project of Poly Changda Company,the influence factors of air content and concrete performance of C70 concrete of pre-tensioned I-beam are studied.This article first analyzes the cement,fly ash,mineral powder,fine aggregate,coarse aggregate,water reducing agent and other raw materials used in the C70 I-beam at the construction site;in order to analyze the influence of each component on the air content of C70 concrete In order to avoid the coupling effect of the constituent materials as much as possible,in the study,the pure slurry,mortar and concrete based on the production mix ratio of the pretensioned I-beam C70 concrete were used to carry out the experiments.Among them,the pure slurry test analyzes the influence of water-binder ratio,mineral admixtures and admixtures on air content;the mortar test analyzes the influence of fine aggregate on air content;the concrete test analyzes the influence of coarse aggregate on air content.Through Imagepro plus6.0 image analysis software,a set of numerical evaluation methods for the appearance quality of concrete was drawn up and used for the evaluation of the porosity of the I-beam C70 concrete on site.The influence of fumed silica powder and emulsion on the air content and performance of I-beam C70 concrete was studied.In terms of construction technology,the influence of mold release agent and mold material on the appearance of pores in the formed concrete was studied.Finally,the hydration exothermic behavior of C70 concrete cementitious material system mixed with air-entraining agent and fumed silica is studied.The results are as follows:(1)As the water-binder ratio increases,the air content of both the pure slurry and the mortar decreases;the fluidity of the slurry has a significant effect on the air content,and the water-to-binder ratio affects the fluidity of the slurry and then affects the air content.(2)The air content of mortar and concrete increases with the increase of the interface between the aggregate and the cementitious material.Compared with the influence of coarse aggregate,the influence of fine aggregate on the air content is more significant.The air content is much higher than that of pure slurry and concrete.(3)The increase of the air-entraining agent content will increase the air content,and as the air content increases,the compressive strength first increases and then decreases.When the air content exceeds 6%,the concrete strength decreases particularly significantly.This study The most reasonable concrete air content range of C70 concrete with middle-first-tensioned I-beam is about 3%,and the workability and strength of the concrete at this time can meet the needs of the project.When the water reducing agent is mixed with 0.04% air-entraining agent,the total hydration heat release rate of the pre-tensioned I-beam C70 concrete cementing material system is equivalent to the total hydration heat release when the air-entraining agent is not added.(4)The air content of both the pure slurry and concrete increases with the increase of the fumed silica powder or emulsion.The fumed silica affects the fluidity of the slurry and thus the air content.At the same time,it was found that within the range of the fumed silica content in this experiment,fumed silica powder and emulsion can improve the early compressive strength of pure slurry and concrete,and the powder effect is better.The total hydration heat of the pre-tensioned I-beam C70 concrete cementing material system with 0.26% fumed silica powder is higher than that without fumed silica.(5)Through the research on the release agent and mold material,it is found that when the water-based release agent is used and the mold is a plastic mold,the surface of the concrete is the smoothest and there are few pores. |
PDF Full Text Request