The Experimental Study On The Mechanical Properties And Frost Resistance Of Recycled Aggregate Concrete

As the modernization process of human beings develops, great huge quantity of concrete is consumed worldwide. So the impacts of wastes from building demolition on the environment become an urgent problem to be solved. A possible method to overcome this issue may be using Recycled Aggregate Concrete (RAC). As the durability is an important aspect that influence the life cycle of constructions, the durability properties of RAC was put out.The aim of this project is to research the frost resistance of RAC and identify the mechanical properties of RAC under freeze-thaw environment. This paper firstly produced two different original concrete: air-entrained concrete and non-entrained concrete . After 28 days of conservation the compressive strength was identified and found out that after air-entrained the strength was significantly reduced. The original concrete was crushed by jaw crusher, two coarse aggregate were achieved after sift out: the air-entrained aggregate(ARG), the non-entrained aggregate(NRG). Produced RAC with such coarse aggregate. The law of aggregate, air content, aggregate processing method on the strength was achieved by analyzing the compressive strength. 100 freeze-thaw cycles test was carried through on the prism specimens by means of standard quick freezing and thawing method. Meanwhile, the ratio of weight loss and the dynamic modulus of elasticity behave regular changes were measured, cubic polynomial expressions were used to fit the relationship between the relative dynamic modulus of elasticity and the freeze-thaw cycles n.In this paper, the rigid unit was appended on the normal compression testing machine to get the stress-strain curve of all the prism specimens and the entire stress-strain curves were obtained. Based on the experimental results, the changing law of the peak stress, peak strain, elastic modulus, transverse deformation were gained. Such factors: the aggregate type, times of freeze-thaw cycles, aggregate processing method that may influence the changing law were analyzed. Established the equations that fit the relationship between freeze-thaw parametersΔP_n and the mechanical parametersαa,αd. It's convenient to be used in engineering applications.In addition, scanning electron microscopy test, microanalysis test were done to observe the microstructure of RAC. The interfacial transition zone of various specimens was observed and analyzed in detail, analysis of microstructure's influence on the freeze-thaw resistance was made out and then found out the key factors that affect these properties. So as to provide some references to improve the engineering properties of RAC in the future. 7 groups of shrinkage test was done in this paper. Such factors as aggregate, aggregate processing methods that may influence the shrinkage were analyzed.