Optimization Of C50 Concrete Mix Ratio Based On Orthogonal Test

With the rapid development of China’s economic construction,the number of highway bridges has increased year by year,alleviating traffic pressure and providing convenience for transportation.Many regions in Northeast China and North China belong to typical severe cold areas,and the natural environment is extremely harsh,which puts forward higher requirements for highway bridges.The strength and durability of the pier concrete directly determine the safety and service life of the bridge.Under the action of external complex environment(deicing salt and freeze-thaw,etc.),the bridge pier will be eroded by chloride ions and freeze-thaw cycle,which will cause the concrete bridge pier to suffer different losses,which directly affects the safety and service life of the concrete bridge.It will threaten people’s lives and property safety.Therefore,based on the orthogonal test,the C50 concrete of bridge piers in the severe cold area was optimized.Its purpose is to improve the durability of the C50 concrete bridge pier,and is essential to reduce maintenance costs and extend the life of the bridge.For the C50 concrete of a bridge pier in a severe cold area,according to the actual requirements of the project,the compressive strength,anti-chlorine ion permeability,frost resistance and shrinkage performance of the bridge pier C50 concrete are used as the assessment indicators.Compound dosage of fly ash and mineral powder(composite ratio 1:1),silica fume dosage and gas content are taken as influencing factors,and four factors and four levels orthogonal test plan are formulated.According to the current common concrete mix design rules,determine the C50 concrete mix ratio.According to the current test method standards,the compressive strength,chloride ion migration coefficient,frost resistance and shrinkage performance of the bridge pier C50 concrete mix ratio under different levels of various factors were measured,and the test results were analyzed in extreme range.The influence of factors on the concrete assessment index is optimized through comprehensive analysis to select the mix ratio that satisfies each performance index.The results show:The water-binder ratio is the most significant factor that affects the 28d shrinkage of concrete,and ranks second in the ranking of the significant impact of 28d compressive strength of concrete,56d chloride ion migration coefficient,and concrete frost resistance.Control within 0.4;gas content is the most significant factor that affects the 28d compressive strength and frost resistance of concrete,and it ranks second in the ranking of the 28d shrinkage of the concrete,and the gas content of the concrete mixture can be selected from 3%and 5%;The compound dosage of fly ash and mineral powder is the most significant factor affecting the 56d chloride ion migration coefficient,and its dosage can be controlled within the range of 30%to 40%.Mix ratio(water-binder ratio is 0.34,fly ash and Mineral powder is 30%,gas content is 5%)and Mix ratio(water-binder ratio is 0.34,fly ash and Mineral powder is mixed 40%,silica fume content 2%,gas content 3%)can be used as the optimized concrete mix ratio.