Experimental Study On Mechanical Properties And Frost Resistance Of Polypropylene-Cellulose Fiber Lightweight Aggregate Concrete

With the gradual deepening of urbanization,concrete has become the most widely used building material by virtue of its excellent properties.The research on various aspects of concrete performance has also made more in-depth development.Pumice lightweight aggregate concrete has a wide range of application prospects due to its light weight,good thermal insulation,strong thermal insulation and good frost resistance.In Inner Mongolia,natural pumice is rich in resources.Pumice is used to replace the coarse aggregate of ordinary concrete to prepare lightweight aggregate concrete.The influence of polypropylene fiber and cellulose fiber hybrid on lightweight aggregate concrete is studied,and its macroscopic properties are discussed through indicators such as compressive strength,splitting tensile strength,relative dynamic elastic modulus,mass loss rate and so on.And through the use of scanning electron microscopy,mercury intrusion test to conduct in-depth research on its microscopic morphology,pore change rules and pore size distribution changes,the results show that:(1)With the increase of cellulose fiber content,the cubic compressive strength and splitting tensile strength both increased first and then decreased.The optimal dosage is 0.6kg/m~3 for polypropylene fiber and 0.9kg/m~3 for cellulose fiber.The optimal compressive strength of the cube is 38.76MPa,which increases by 11.1%.The optimal splitting tensile strength is 3.2MPa,increased by 77.8%.(2)The pumice lightweight aggregate concrete strength prediction model was established,and the other scholars and BP neural network prediction model,the test data results compared validation,validation results show that the prediction formula of high precision and less test data validation errors,the compressive strength of lightweight aggregate concrete for pumice reference for related research.(3)The addition of cellulose fiber improves the freezing resistance of lightweight aggregate concrete specimens,and the best freezing resistance is when the polypropylene fiber is 0.6kg/m~3 and cellulose fiber is 0.9kg/m~3.The addition of cellulose fiber can make the variation of pore structure characteristic parameters less than that of the reference group,and the pore size distribution is better than that of the reference group,and at the same time reduce the variation rate of concrete pore size.(4)The influence of pore characteristic parameters and pore size distribution on macroscopic test results was determined by grey entropy correlation degree.The most important factors affecting the compressive strength are the total pore area and the grey entropy correlation of pore size distribution<20nm,which are 0.99287 and 0.99356.The most important factors affecting the mass loss rate are the total pore volume and the grey entropy correlation of 50-200nm pore size distribution,which are 0.99403 and 0.9991.The largest factors of relative dynamic modulus are the total pore area and the grey entropy correlation degree of pore size distribution<20nm,which are 0.99903 and 0.99939.The GM(1,3)model is established for the compressive strength and relative dynamic modulus of concrete in freeze-thaw cycle according to the order of influence.