Study On Recycled Aggregates Concrete Modified Experiment

With the improvement of urbanization level, further accelerate the speed of urban construction, the average life expectancy of building less than 30 years in our country, which makes the production of large Numbers of construction waste, construction waste has three to forty percent of the total waste. As one of the construction waste, waste concrete, simple landfill treatment, not only occupy the limited land resources, but also spend a certain number of resources. Secondary utilization of the waste concrete, domestic and foreign scholars have studied for many years, and have achieved some results. Recycled aggregate is made of waste concrete crushing and come, a lot of use of waste concrete is a necessary choice to protect the environment and sustainable development,Also contributing to the ecological environment and promoting the harmonious development of man and nature, has a profound social significance and superior economic value.Based on the analysis of recycled aggregate concrete research present situation, on the basis of summarizing the predecessors’ research results, selection of laboratory waste made of recycled aggregate concrete was treated, according to some natural defects of recycled aggregates, put forward by adding polypropylene fiber and silica fume, using their special effect, to make mechanical properties and durability of the recycled aggregate concrete. By orthogonal test and carbonation resistance, freezing-thawing resisting performance, resisting impact, abrasion test, research of polypropylene fiber and silica fume, the mechanical properties of the recycled aggregate concrete, carbonation resistance and freeze resistance performance and effect of resisting impact, abrasion and discuss the influence mechanism, the results as follows:(1) Through the orthogonal experiment optimization and comprehensive analysis, it is concluded that the optimal mixture ratio of recycled aggregate concrete A2B3C3D2E2, water-cement ratio 0.43,20% dosage of fly ash,60% recycled aggregate, silicon ash content is 4%, polypropylene fiber content is 0.9 kg/m3.(2) Through 28 d physical mechanics performance test results show that by adding polypropylene fiber and silica fume, the optimization of basic close to the benchmark set pressure strength, lower than the baseline group only 0.6%,10.8% higher than the recycled aggregate concrete, the strength and meet the design requirements.(3)All performance than ordinary concrete carbonation resistance of recycled aggregate concrete is poorer, polypropylene fiber on the carbonation resistance of concrete. Added fly ash and silica fume optimization group Y carbonation resistance of recycled aggregates with fully improved.(4) The frost resistance of concrete test showed that the curing conditions, four groups of concrete frost resistance size order for J> Y> W>Z. Y antifreeze performance very close to the J group, and is much higher than Z group (group full of recycled coarse aggregate).60% recycled aggregate, silica fume, double mixing polypropylene fibers can obviously improve the recycled aggregate concrete of antifreeze performance.(5) The impact abrasion resistance of concrete test showed that the standard curing condition, four groups of anti-abrasion strength of the specimens in order of size is in turn:J (reference group), Y (preferred), W (no fiber group), Z (full set of recycled aggregates). Y group (optimization) rushed grinding strength than J group decreased by 10.5%. the wear rate W group was down more than J 15.4%, Z group than J wear rate decreased by 30.3%, W group than Y wear rate decreased by 5.6%.