Experimental Study On Mechanical Properties And Durability Of Steel Polypropylene Hybrid Fiber Reinforced Lightweight Aggregate Concrete

Lightweight aggregate concrete is replaced by lightweight aggregate that is artificially made or naturally formed instead of coarse aggregate in ordinary concrete.Lightweight aggregate concrete has the characteristics of light weight and high strength.Under the same volume,lightweight aggregate concrete is about 20% to 30% lighter than ordinary concrete,and the impermeability and corrosion resistance of light aggregate concrete of the same grade are better than those of ordinary concrete.However,the low strength and brittleness of lightweight aggregate concrete limit its development.With the aim of improving the brittleness of lightweight aggregate concrete,the test of mixing steel fiber and polypropylene fiber is carried out on the basis of the previous research results of steel fiber and polypropylene fiber lightweight aggregate concrete.Two factors influencing the volume ratios of steel fiber and polypropylene fiber were selected in the test.The test was made of polypropylene fiber with 0.05%,0.10%,0.15% volume ratio,the volume ratio of steel fiber with 1%,1.5%,2%,and the mix of polypropylene fiber and steel fiber into the lightweight aggregate concrete matrix.The mechanical properties and durability performance of steel-polypropylene hybrid fiber lightweight aggregateconcretewere studied.The maincontents areas follows:(1)Cube compressive strength test.A total of 16 groups of specimens were designed.Through the analysis of the test data,the optimal fiber volume ratios for the single-blended steel fiber group,polypropylene fiber group,and hybrid fiber group were obtained,and the fiber reinforcement coefficient and fiber hybrid coefficient were introduced.The positive and negative hybrid effects of the hybrid fiber group were analyzed.Finally,the linear regression analysis was carried out by using SPSS software,and the relationship between compressive strength and hybrid fiber reinforced lightweightaggregateconcrete was obtained.(2)Splitting tensile strength test.A total of 16 groups of specimens were designed.Through the analysis of the test data,the optimal fiber volume ratios for the single-blended steel fiber group,polypropylene fiber group,and hybrid fiber group were obtained,and the fiber reinforcement coefficient and fiber hybrid coefficient were introduced.The positive and negative hybrid effects of the hybrid fiber group were analyzed.Finally,the linear regression analysis was carried out by using SPSS software,and the relationship between splitting tensile strength and hybrid fiber reinforced lightweightaggregateconcrete was obtained.(3)Durability test.It includes water infiltration resistance,resistance to 50 freeze-thaw cycles,resistance to sulfate corrosion test.Through the analysis of the test data,the optimal fiber volume ratios of single-doped steel fiber group,polypropylene fiber group and hybrid fiber group in each test were obtained.Based on the relationship between the impermeability and resistance to 50 freeze-thaw cycles and resistance to sulfate corrosion,linear functional relationships between the impermeability of the hybrid fiber lightweight aggregate concrete and the resistance to the 50 freeze-thaw cycles and the resistanceto sulfate corrosion wereobtained.(4)Based on the relationship between the impermeability and durability of concrete,the "impermeability" rating was established to evaluate the "steel-polypropylene hybrid fiber lightweight aggregate concrete durability evaluation system." Through the linear fitting of the data of water penetration resistance test with the latter two data respectively---the anti-50 freeze-thaw cycles and the anti-sulfate corrosion resistance data,the correlation function of steel polypropylene hybrid fiber lightweight aggregate concrete is established to evaluate its durability on the basis of its impermeability.