Experimental Study On Fracture And Durability Of Recycled High Performance Concrete

Recycled concrete is a new concrete that using recycled aggregate which comes from the waste concrete of old building after crushing, washing, screening and mixing with a certain proportion of mutual cooperation as a part or all of aggregate replacing natural aggregate. Because of much rejected cement mortar and other impurities in recycled aggregate, nowadays recycled concrete whose intensity is low, volume stability is poorer and durability is not high. As the further development of concrete, recycled high performance concrete is coming out. On the one hand, it's reasonable to use recycled concrete. On the other hand, it adds super plasticizer and mineral admixtures, so the strength and durability of RHPC is improved greatly. The situation that it closed with our country's environment protection, ecological protection policies and sustainable development strategy conforms to the trend of the future, and also an important direction of concrete.In this paper, the author researches the fracture performance and durability of RHPC by compressive strength of concrete, chloride ions diffusion coefficient fast detection of RCM test and three-point bending test which can measure the fracture energy of concrete, also together with optimization and fractal theory. The test results as follows : (1) with the replacement of recycled aggregate increasing, the compressive strength and anti-chloride ion erosion ability on RHPC is reducing gradually , but the reducing amplitude are both not very big, the reason is that the bibulous rate and hydraulic are a little big from recycled concrete, reduced its mechanics and durability performance; (2) to optimize aggregate replacement, the best aggregate substation is only a theoretical data, in practical engineering it can calculate the similar best aggregate substation from the method which is provided by this paper; (3) the quantitative relationship between compressive strength and fracture energy are not determined, it's relevant with the quality of recycled aggregate and mineral admixture preliminary forecast, and waiting for the future studies; (4) the bigger fractal dimension of fractures on RHPC is, the smaller compressive strength of concrete is , it also can calculate the compressive strength by formula like y=-2560.762x+2692.364.At last, the author reviews all the conclusions from experiment and theoretical derivation nearly half a year. The problems which require to be solved in future on microscopic analysis of interface transition layers and carbonation influences their resistance about the ability of chloride eroding are discussed. And then how to lightweight and fracture studies were prospected. It is said that RHPC must be a new area after nature recycled concrete is mature, and will have a broad outlook.