Experimental Study On The Influence Of Modified Construction Waste Aggregate On Concrete Properties

When the recycled aggregate is crushed by the crusher,the aggregate is damaged,causing fine cracks in the aggregate itself,which reduces the performance of the recycled aggregate,and also causes the recycled concrete prepared with the recycled aggregate to be unsatisfactory.Actual engineering needs.In this paper,chemical solution is used to soak and modify the recycled coarse aggregate of construction waste to improve the performance of the recycled coarse aggregate,so that the modified recycled concrete can be more widely used.However,because of the wide range of recycled aggregate sources,the performance is different,and the strength of fully recycled aggregate concrete is low.Therefore,on the basis of chemical modification,the problems of uneven aggregate quality and low strength of fully recycled concrete are solved by changing the replacement rate of recycled aggregate.Finally,by examining the performance of different types of concrete,the substitution rate range and chemical modification schemes that make the performance of recycled concrete more stable are explored.The analysis of the test results reached the following conclusions:(1)Soak treatment of construction waste coarse aggregate through three chemical modification schemes: water glass modification,PVA modification,and water glass-PVA composite modification.It is found that the performance of the modified aggregate has been greatly improved.Among them,the water absorption and crushing value indexes have the most significant improvement effects,which are48.8% and 24.3% lower than the unmodified recycled coarse aggregates,respectively.However,the improvement of apparent density and bulk density is less,and the improvement effect is not too obvious.(2)In terms of mechanical properties,the replacement rate of recycled aggregates has a negative correlation with concrete properties.The optimal substitution rate ranges from 0% to 50%.Within this range,the performance of recycled concrete decreases slowly with the increase of the replacement rate of recycled coarse aggregate,and the performance of recycled concrete is relatively stable.When the substitution rate is 30%,the concrete performance is relatively stableand the strength is high at this time,which can basically meet the needs in actual engineering,and the utilization rate of recycled construction waste aggregate is also considerable.The three chemical modification schemes have greatly improved the mechanical properties of concrete.From good to bad,they are water glass-PVA composite modification,water glass modification and PVA modification.(3)In terms of durability,the frost resistance of recycled concrete is poor.Even by changing the substitution rate and modifying the aggregate with a chemical solution,there is a large gap compared with natural concrete.However,the impermeability of recycled concrete is better,and the impervious grade of the recycled concrete after modification can reach the highest P10.