Experimental Study On Modification Of Recycled Aggregate And Concrete Properties With Construction Waste

At present,the rapid development of the construction industry has brought about some negative problems while promoting economic development.On the one hand,the development of raw materials used in new construction comes from natural minerals,which consumes a lot and causes serious threats to the sustainable development of the ecological environment;on the other hand,the demolition of old buildings will generate huge construction waste.The improper disposal of construction waste will not only pollute the environment,but also contradict the circular economy.Recycling the concrete of construction waste can effectively alleviate the above-mentioned resource,ecological and environmental crisis,and it is the best way to solve the above problems.Based on the review of the status quo of construction waste resource utilization at home and abroad,this paper determines the research plan for the reinforcement modification test of construction waste aggregate concrete.The experiment mainly studied the material properties,modification strengthening,mechanical properties and durability of construction waste coarse aggregate and fine aggregate,and obtained the following conclusions:(1)Construction waste aggregate has the characteristics of low density,high water absorption,high water content,high mud content and low crushing index.(2)The properties of various materials of Modified aggregate(immersed in 5% water glass solution for 1h,immersed in 10% PVA solution for 24 h,immersed in 8% silane solution for 24 h,immersed in 5% water glass solution for 1h+ immersed in 10% PVA solution for 24 h,immersed in 5% water glass solution for 1h+ immersed in 8% silane solution for 24h)were improved.Among them,water absorption rate and crushing index were the best to improve the properties,and the improvement effect of fine aggregate of construction waste was better than the coarse aggregate of construction waste.The best performance improvement effect of the five schemes is water glass-silane composite modification(the apparent density of coarse and fine aggregates can be respectively increased by 1.4% and 4.5,the bulk density can be respectively increased by 6.1% and 5%,respectively,the water absorption rate can be respectively reduced by 47.3% and 64%,respectively,the water content can be respectively reduced by 40% and 35.3%,the crushing index can be respectively decreased by 24.6% and 37.3% respectively),followed by water glass modification,silane modification,water glass-PVA composite modification and PVA modification.(3)The experimental results of concrete mechanical properties show that the recycled concrete of aggregate of construction waste has the characteristics of low compressive strength,low splitting tensile strength and low flexural strength.The mechanical properties of concrete made by construction waste aggregates treated with five modified schemes have been significantly improved.The ratio of splitting tensile strength to compressive strength and the ratio of flexural strength to compressive strength of the recycled concrete of each group are relatively large.The best improvement in mechanical properties is water glass-silane composite modification(the compressive strength can be increased by 19%,the splitting tensile strength can be increased by 14%,and the flexural strength can be increased by 9%),followed by water glass modification,silane modification,water glass-PVA composite modification,and PVA modification.(4)The durability test of concrete shows that the anti-freezing performance of recycled concrete of aggregate of construction waste is relatively good and the impermeability is better,which can basically meet the anti-leakage requirements of engineering.The durability properties of concrete made by construction waste aggregates treated with five modified schemes have been significantly improved.The best improvement in durability is water glass-silane composite modification,followed by water glass modification,silane modification,water glass-PVA composite modification,and PVA modification.