Research On Physical And Mechanical Properties Of Recycled Concrete Affected By Water Absorption Of Recycled Aggregate

According to the demands of sustainable development of construction field, recycled concrete, as a renewable energy, can solve resource and environmental development issues. Recycled aggregate is formed by mixing a certain percentage of waste concrete blocks that is crushed, cleaning and grading. Water absorption of aggregate is the biggest difference between natural aggregate and recycled aggregate. Therefore, this article focuses on the physical and mechanical properties of recycled concrete affected by the water absorption of recycled aggregate.First, paper studies the physical and mechanical properties of recycled concrete affected by the replacement ratio of recycled aggregate in the same water-cement. With the increase of recycled aggregate replacement rate, the results show that the flow of recycled concrete reduced, the adhesive and water retention increased, and the strength had an upward trend.Secondly, paper studies the effect of recycled aggregates on mechanical properties of recycled concrete with different strength grade. With the premise of the same water-cement ratio, test results show that recycled aggregate has an effect on mechanical properties of recycled concrete with different strength grade. The strength of C60 recycled concrete was lower than the corresponding ordinary concrete; The strength of C20 and C40 recycled concrete was higher than the corresponding ordinary concrete. Test results also show that crushing value of recycled aggregate is a major factor to determine the mechanical properties of high-strength recycled concrete. Water absorption of recycled aggregate is a major factor to determine the mechanical properties of medium-strength and low-strength recycled concrete.Finally, paper studies the physical & mechanical properties and the microstructure of recycled concrete composed of different water absorption recycled aggregates. The results show that, with the premise of the same water-cement ratio, the strength of recycled concrete is higher than ordinary concrete, and the strength of recycled concrete with high water absorption recycled aggregates is higher than that with low water absorption recycled aggregates. The results also show that the hardness of recycled aggregate-cement interfacial transition zone is higher than natural aggregate-cement interfacial transition zone, and the hardness of recycled aggregate-cement interfacial transition zone with high water absorption recycled aggregates is higher than that with low water absorption recycled aggregates. The paper considers that there are many pores in the recycled aggregate-cement interfacial transition zone. When a part of the mixing water is adsorbed to the pore, the water-cement ratio of the recycled aggregate-cement interfacial transition zone decreases, and therefore the interface can be strengthened.As to the results, the paper puts forward a conception of "water absorption of recycled aggregate is the core factor to determine the physical and mechanical properties of recycled concrete". That can provide an important reference for forming technical specifications of recycled concrete application.