Experimental Research On The Influence Of High Temperature On The Performance Of Concrete With Solid Waste Aggregate

With the development of urbanization,the demand for natural sand and stone for concrete has gradually increased.The comprehensive utilization of solid waste as a resource can not only solve the problems of land occupation and environmental pollution caused by long-term stacking of solid waste,but also alleviate the shortage of natural aggregates and realize the green and sustainable development of the construction industry.In this paper,the basic properties,microscopic composition and thermal stability of solid waste aggregates were analyzed from the macroscopic and microscopic perspectives.The effect of solid waste aggregate replacement rate(10%,25%,50%,100%)on the mechanical properties of concrete at room temperature was explored.The effect of high temperature on the performance of solid waste aggregate concrete was studied through the after high temperature(200℃,400℃,600℃,800℃)mechanical properties,durability and thermal expansion performance of solid waste aggregate concrete.The main contents and results were as followed:The solid waste coarse and fine aggregates were prepared through technological such as crushing,screening and washing.The basic properties of different solid waste aggregates were studied by compare with natural aggregate.The chemical composition,mineral composition,microstructure and thermal stability of different solid waste aggregates were explored through microscopic and thermal analysis methods.The results shown that the particle gradation,apparent density and crushing index of solid waste aggregate met the quality requirements of sand and gravel used in the preparation of concrete.Siliceous and aluminum elements were richly contained in aggregate.The main minerals included calcite,quartz,feldspar and kaolinite,and the microstructure presented lamellar bedding characteristics.Obvious endothermic peaks of were shown at high temperatures and were accompanied by weight loss.The cubic compressive strength,splitting tensile strength,axial compressive strength and elastic modulus of concrete with different substitution rates were determined through the mechanical performance test at room temperature.The results shown that within the 50% replacement range,the cubic compressive strength and axial compressive strength of solid waste aggregate concrete met the quality requirements of concrete,even higher than that of ordinary concrete.The splitting tensile strength was lower than that of ordinary concrete,but the elastic modulus of solid waste fine aggregate concrete was improved.The compressive strength,splitting tensile strength and elastic modulus of the concrete replaced by 50% of the solid waste coarse and fine aggregates were determined through the mechanical performance test after high temperature.The results shown that the strength and elastic modulus of concrete gradually decreased with increasing temperature.The strength and elastic modulus of concrete was reduced due to the defects of solid waste coarse aggregates.But that was promoted due to the rough surface and irregular particle morphology of solid waste fine aggregates.The thermal expansion deformation of the concrete replaced by 50% of the solid waste coarse and fine aggregates was determined during the heating and constant temperature stages through the high temperature expansion deformation test.The PCY high temperature dilatometer was used.The results shown that the thermal expansion deformation of concrete with coal gangue aggregate and ceramic tile aggregate was lower than that of ordinary concrete at the end of heating.The difference in thermal expansion deformation of different aggregate concretes gradually increased with the heating time.At the end of the constant temperature,the thermal strain and thermal expansion coefficient of the concrete were significantly greater than before the constant temperature.The water absorption,freeze-thaw resistance and carbonization resistance of the concrete replaced by 50% of the solid waste coarse and fine aggregates were studied through the durability test after high temperature.The results shown that when the temperature was 200℃ and 400℃,the water absorption rate of solid waste aggregate concrete was greater than that of ordinary concrete.The compressive strength of solid waste aggregate concrete was significantly reduced after high temperature and freezethaw.The compressive strength of concrete with granite aggregate and ceramic tile aggregate was better under the same conditions.The carbonation depth of solid waste coarse aggregate concrete was greater than that of ordinary concrete.The better carbonation resistance was represented for solid waste fine aggregate concrete.There are 114 figures,38 tables and 134 references in this dissertation.