Study On The Properties Of Self-compacting Sand Concrete For Underwater Cast-in-place Pile

The underwater cast-in-place pile is unable to vibrate when the concrete is poured in the mud wall,and the concrete is required to be formed by gravity flow after pouring,so self-compacting concrete becomes the best choice.Due to the non-renewable natural river sand resources,the river sand exploitation is restricted in some areas,and machine-made sand has become the main material for construction sand.In this study,combined with the requirements of underwater cast-in-place pile concrete and self-compacting concrete,machine-made sand is used to prepare machine-made sand self-compacting concrete for underwater cast-in-place pile,and the influence of mixing ratio and admixture factors on its performance is studied.1.It is found that the design parameters of mix ratio can be adjusted by clean slurry fluidity test and mortar test to improve the performance of self-compacting concrete of machine-made sand in underwater cast-in-place pile.The proportion of mineral admixture and the content of mechanized sand in self-compacting concrete of mechanized sand of underwater cast-in-place pile were adjusted by the fluidity test of cementified material and the volume ratio test of mortar sand.In the use of the net slurry and mortar test to get the better proportion of mixing material and machine-made sand content after the concrete test,by adjusting the coarse aggregate content and aggregate;Increase or decrease mechanized sand content;Adjust the water-binder ratio;The influence of various factors on the performance of self-compacting sand concrete of underwater cast-in-place pile was studied by changing the amount of additives.2.C30,for example,this study put forward the mechanism of underwater pile sand self-compacting concrete parameters optimal mixture ratio,and design a gelled material dosage of 461 kg/m3 of C30 underwater sand self-compacting concrete filling pile mechanism,the expansion degree of initial value reached more than 650 mm,and pass rate meets the demand of self-compacting concrete,reinforcement clearance strength reaches more than 42 MPa.Both workability and strength can meet the requirement of self-compacting concrete of C30 underwater cast-in-place pile.3.to polycarboxylic acid system water reducing mother solution,mother solution to protect slump(A,B)as the basis of compound adjustment of admixture water reducing component,slump protection component,air intake component and thickening component content.The concrete test results show that with the increase of the content of slump-preserving components,the dilatancy of the mixture increases and the loss of slump-dilatancy decreases.When the ratio of type A mother liquor to type B mother liquor is 1:1,the initial expansion of the mixture is the highest,and the loss of slump expansion in 3 hours is qualified.The optimal dosage of air entraining agent is 0.4kg/t by adding the air entraining agent in the way of elimination first and then entry.The study found that the addition of Z-2 thickener can effectively reduce the segregation rate of the mixture,but also reduce the fluidity of the mixture.The study confirmed that the addition of 2kg/t thickener can reduce the segregation rate of the mixture to less than15% while the mixture has sufficient fluidity.4.In order to reduce the dosage of cementing material and improve the economy,adjust the mixing ratio parameters,stone volume ratio Vg is adjusted to 0.34,sand volume ratio Φs is set to 0.44 in mortar,and the mixing ratio of cementing material is reduced from 461kg/m3 to 439kg/m3.Using special admixtures to adjust and optimize the concrete work performance,the test results show that when the admixtures increase to 1.2%,the concrete performance is the best.After calculation,the cost of concrete can be reduced by 1.8% after optimization,which can achieve the purpose of optimizing the mix ratio and reducing the cost.5.Electric flux test is used to detect the chloride ion penetration resistance of mechanized sand self-compacting concrete prepared by underwater cast-in-place pile.It is found that compared with ordinary concrete,mechanized sand self-compacting concrete of underwater cast-in-place pile has better chloride ion penetration resistance.