Study On Durability Of Recycled Concrete Under The Effect Of Sulfate Wet And Dry Cycle

In this paper,the performance characteristics and beneficial effects of recycled coarse aggregate,water binder ratio and mineral admixture were used to study the dry and wet cyclic erosion performance of recycled concrete,as an experimental factor,sulfate dry and wet cycle erosion of recycled concrete block under orthogonal design,single factor design is carried out by simulated sulfate dry and wet cycle erosion environment at the same time.The effects of various factors on the dry and wet cyclic erosion performance of recycled concrete were quantitatively analyzed with multiple evaluation indexes.Based on the multiple factors,a regression model was established under different indicators and explored the deterioration rule under the influence of various factors.Finally,considered the multiple factors and multiple indicators,the life prediction model was established to predict the initial life.The results showed that:(1)In the absence of erosion,the effects of various factors on each index were as follows: water to rubber ratio,replacement rate of recycled coarse aggregate,and content of admixture,the best combination was when the substitution rate of recycled coarse aggregate was 30%,the water binder ratio was 0.3,and the mineral content was 0%.The worst combination is when the substitution rate of recycled coarse aggregate was 70%,the water binder ratio was 0.5,and the mineral content was 40%.When the sulfate dry and wet cycle erosion was 60 and 120 times,the influence factors of various factors on each index were the ratio of water to glue,the amount of mineral admixture,the substitution rate of recycled coarse aggregate,when the substitution rate of recycled coarse aggregate was 30%,the ratio of water to binder was 0.3 and mineral content was 40%,it was the best combination.The worst combination was when the substitution rate of recycled coarse aggregate was 70%,the water binder ratio was 0.5,and the mineral content was 0%.(2)In the whole erosion process,the change of water-binder ratio has a highly significant effect on each index;when it is not eroded,the water-binder ratio is significantly greater than the significance of recycled coarse aggregate,and the recycled coarse aggregate is greater than that of the mixed admixture.When wet and dry cycle erosion was 60 times and 120 times,the water-binder ratio was more significant than that of the compounded admixture,and the admixture was larger than the recycled coarse aggregate.(3)The performance of each index decreased with the increase of the replacement rate of recycled coarse aggregate,and the performance of each index increased first and then decreased in two stages during the whole dry and wet cycle erosion process.(4)With the increase of water binder ratio,the performance of each index decreased rapidly,and the performance of each index increased first and then decreased in the two stage of drying and wetting cycle erosion process.(5)The recycled concrete mixed with mineral admixture has better corrosion resistance performance,and the performance of each index is reduced first,then increased,or first flattened and then increased.Finally,a three-phase mode is added.In the same amount,the mixed slag and powder are mixed.The anti-corrosion performance of coal ash is greater than the anti-corrosion performance of single admixed slag.The single admixed slag is larger than the anti-corrosion performance of single doped fly ash;within a certain amount of dosing,the performance of each indicator decreases with the increase of mineral admixtures in the early stage,and later Increases with mineral admixtures.(6)According to the law of material decay,based on the result of single factor test,the life prediction model of multi factor and multi index were considered.When recycled concrete was in the environment of sulphate erosion,it was preliminarily predicted that the life of the project is 117 years.