Mix Proportion Design And Performance Study Of Concrete In Bridge Of Long Yan Railway

The Long Yan Railway is located in Yantai City.Because of the large fluctuations in the quality of local raw materials,there are certain difficulties in the concrete construction of prefabrication T-girder engineering.To this end,the mix proportion were designed and the performance were studied for the girder body concrete,the girder deck protection concrete and the anchor hole filling concrete.The micro-structure of the bridge body concrete with different fly ash content was studied by SEM test technique.Combined with the problems that may occur in the actual construction of prefabricated T-girders,the causes of girder concrete quality defects were analyzed.The conclusions are outlined as follows:?1?For the girder body concrete,appropriate fly ash content should be selected and the mud content of the coarse aggregate should be controlled below 1.3%to meet the performance requirements during the preparation.One-time one-factor method is used and by calculations and tests,the best mix proportion of bridge body concrete is that W/B is 0.30,sand percentage is 39%,fly ash content is 16%,water dosage is 145kg·m^-3,and water reducer dosage is 1.1%.All performance indexes of concrete meet the design index requirements and its economy is reasonable.The SEM observation of the girder body concrete with age of 28 days showed that different fly ash content have effects on the compactness,holes,and micro cracks of the concrete.When the fly ash content is 16%,the micro-structure of the concrete is optimal.?2?For the girder deck protection concrete,appropriate fly ash content and polypropylene fiber content should be selected to meet the the splitting tensile strength requirement during the preparation.One-time one-factor method is used and by calculations and tests,the best mix proportion of bridge deck protection concrete is that W/B is 0.33,sand percentage is 48%,fly ash content is 30%,water dosage is 148kg·m^-3,water reducer dosage is 1.2%,and polypropylene fiber content is 1.8 kg·m^-3.All performance indexes of concrete meet the design index requirements and its economy is reasonable.?3?For the anchor hole filling concrete,appropriate expansion agent content should be selected to meet the limiting expansion rate requirement during the preparation.One-time one-factor method is used and by calculations and tests,the best mix proportion of anchor hole filling concrete is that W/B is 0.30,sand percentage is 41%,fly ash content is 10%,water dosage is 140 kg·m^-3,water reducer dosage is 1.0%,expansion agent content is 10%of the total amount of cementing material.All performance indexes of concrete meet the design index requirements and its economy is reasonable.?4?Due to the fluctuation of the quality of the the girder body concrete,when the problem of bleeding occurs,the dosage of water reducer can be adjusted from 1.1%to1.0%and the sand rate can be adjusted from 39%to 40%.When the problem of pockmarking of the girder due to the excessive viscosity of the concrete,the dosage of water reducer can be adjusted from 1.1%to 1.2%and the sand rate can be adjusted from 39%to 38%,thereby improving the cohesion of the concrete.For the girder deck protection concrete,the dosage of water reducer which changes from 1.2%to1.25%can solve the slump loss problem caused by the construction time is too long,and can prevent the concrete surface crack generation.