Service Life Prediction Model for Wastewater Concrete Under Sulfate Dry-wet Cycle
To solve the durability problem of concrete in salty soil environment in the alpine region of Northwest China,the influence of different mixing plant wastewater on the durability of concrete against sulfate dry-wet cycle was investigated.To study the influence of different dosage of mixing plant wastewater on concrete resistance to sulfate under dry-wet cycle,the concrete mixing plant wastewater was mixed with C40 concrete by replacing potable water with 0%,25%,50%,75%,and 100%proportion of equal mass.The fly ash replaced cement with 20%proportion of equal mass.The specimens of 40 mm×40 mm×160 mm were tested by using 5%concentration of magnesium sulfate solution for full immersion dry-wet cycle test.The compressive strength,flexural strength,relative dynamic elastic modulus,mass and water absorption of concrete were tested.The relative dynamic elastic modulus was also used as the evaluation index,and the life prediction was carried out by using the gray prediction GM(1,1)model and damage quadratic decay model.The result indicates that with the increase of wastewater substitution rate,the concrete compressive strength loss firstly decreases and then increases.The rate of concrete mass loss under dry-wet cycle is C40-75,C40-100,C40-50,and C40-25 in descending order.The main oxides of mixing plant wastewater are similar to cement,and the microscopic morphology is mostly porous irregular particles,which can delay the deterioration rate of C40 concrete in sulfate dry-wet cycle.The degradation rate of C40 concrete in sulfate dry-wet cycle environment can slow down the deterioration rate of C40 concrete in cycle environment,so that the concrete improves the resistance to the invasion of SO42-,of which the concrete has the best resistance to SO42-erosion when the wastewater substitution rate is 50%.The GM(1,1)life prediction shows that the concrete has the longest durability life when the wastewater substitution rate is 50%.The durability life increases by 2.3 times.The concrete can resist 74 times sulfate dry-wet cycle.The decay model correlation coefficient R2 is greater than 0.94,which has high accuracy.
road engineeringservice life prediction modelgray prediction GM(1,1)wastewater concretedry-wet cyclesulfate
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