Study On Permeability Resistance Of C50 Marine Concrete In Main Tower Of Zhoudai Cross-sea Cable-stayed Bridge

In this paper,the impervious performance of C50 Marine concrete used in the main bridge tower is studied by investigating the design requirements,service environment and raw materials of zhoudai sea-crossing cable-stayed bridge.Firstly,the optimal design of the concrete mix ratio of the main tower C50 of zhoudai sea-crossing cable-stayed bridge was carried out.The influence of water-binder ratio,sand ratio,fly ash content and ore content on its impermeability and its variation law were analyzed by orthogonal test method.Secondly,the control variable method was used to design the mix ratio of C50Marine concrete in the main tower,and the low-grade limestone powder and fly ash were mixed in different proportions to study the influence of the composite effect of the two on the impermeability of C50 Marine concrete in the main tower.The internal microstructure of C50 Marine concrete in the main tower was studied by SEM test.The following main conclusions are drawn:?1?Water-binder ratio is the main factor affecting the impermeability of C50 Marine concrete in the main tower.In this paper,the influence of water-binder ratio on the impermeability of C50 Marine concrete is studied by orthogonal contrast ratio test.It is found that with the increase of water-binder ratio,the concrete electric flux value and the28-day chloride diffusion coefficient gradually increase,and the impermeability becomes worse.Therefore,reducing the water-binder ratio can significantly improve the impermeability of C50 Marine concrete.?2?The content of fly ash and ore powder is a secondary factor affecting the impermeability of C50 Marine concrete in the main tower.The results of electric flux test and RCM test show that when the content of fly ash is 30%,the impermeability of C50Marine concrete in the main tower is the best.When the content of ore powder is 20%,the impermeability of C50 Marine concrete is the best.?3?The sand rate has little influence on the impermeability of C50 Marine concrete in the main tower.The results of the indoor impermeability test show that with the increase of the sand rate,the concrete electric flux value and the 28-day chloride diffusion coefficient change little.By contrast,when the sand rate is 41%,the impermeability of C50 Marine concrete in the main tower is the best.?4?Using the method of range is analyzed,the result of the orthogonal experiment to meet pillar C50 Marine engineering design strength grade of concrete and permeability performance requirements under the premise of economic benefit analysis,the main pillar recommend to choose mix:A₂B₂C₂D₂?water/cement ratio,sand ratio 0.32 42%,30%,the dosage of fly ash and mineral powder content 20%?,and a reasonable project cost.?5?When the low-grade limestone powder is substituted with fly ash by 15%of the total mass of cementing material,the chloride ion migration coefficient and electric flux value of C50 Marine concrete are the lowest.Combined with its working performance and mechanical properties,the optimal dosage of low-grade limestone powder is 10%of the total mass of cementitious material,and the ratio of the two is 1:2.