Experimental Study On Work Performance And Flexural Toughness Of Steel-polypropylene Hybrid Fiber Lightweight Aggregate Concrete

Using ceramsite instead of ordinary coarse aggregate in preparation of lightweight aggregate concrete of the ordinary concrete,compared to ordinary concrete,it is not only light with high strength,and the performance of insulation,sound insulation,and seismic are good.In addition,it is an eco-friendly building material.However,because of brittle and low strength defects,the lightweight aggregate concrete is not conducive to the promotion and application.In this paper,based on the improvement of the brittleness of lightweight aggregate concrete,steel fiber and polypropylene fiber were chosen to mixed into the test combined with the research achievements of steel fiber and polypropylene fiber lightweight aggregate concrete to study the effects of steel-polypropylene hybrid fibers on the performance and flexural toughness of lightweight aggregate concrete when the steel fiber shape is corrugated and end hook shape,steel fiber volume rate is 0.5%to 1.5%,polypropylene fiber aspect ratio is 167,281 and 396,polypropylene fiber content is 0.6 to1.2kg/m³.The main contents and conclusions are as follows:（1）In order to analyze the influence of various factors on the working performance（slump）of lightweight aggregate concrete,orthogonal test was used.Through the analysis of the range and the variance analysis,the conclusion was drawn that for the slump of mixed fiber lightweight aggregate concrete,the effect of each factor from is strong to weak as follow:steel fiber’s volume rate→steel fiber’s shape→polypropylene fiber’s contents→steel fiber and polypropylene fiber’s interaction→polypropylene fiber’s aspect ratio.The incorporation of steel fibers and polypropylene fibers reduces the slump of lightweight aggregate concrete.（2）In order to study the Cubic Compressive Strength Test,18 groups of（each group of three test pieces）steel-polypropylene fiber lightweight aggregate concrete test block and a group（each group of three test pieces）is not mixed with fiber lightweight aggregate concrete test block（blank control group）were designed by the method of orthogonal test.Through the range analysis and variance analysis,the results show that the factors influencing the compressive strength of the mixed fiber lightweight aggregate concrete cubes are from strong to weak:steel fiber’s shape→steel fiber’s volume fraction→polypropylene fiber’s content→steel fiber and polypropylene fiber’s interaction→polypropylene fiber’s aspect ratio.The effect of steel fiber on the compressive strength of lightweight aggregate concrete is highly significant,and the corrugated steel fiber has better effect.（3）Orthogonal test was used to design 18 groups（3 of each group）of steel-polypropylene fiber lightweight aggregate concrete specimen and 1 group（3 of each group）without fiber-doped lightweight aggregate concrete specimen（blank control group）.The bending-toughness tests were carried out on each set of test pieces according to the recommended three-point loading method in the Fiber Reinforced Concrete Test Method Standard（CECS 13:2009）.The load-deflection curves were plotted to obtain the initial crack strength,flexural toughness index and the flexural toughness ratio of the lightweight aggregate concrete was discussed.The optimum fiber dosage was obtained:volume fraction of 1.5%of the end of the hook-shaped steel fiber and the aspect ratio of 281,the volume of 1.2kg/m³ of polypropylene fiber mixed.