Study On Impact Resistance Of Plastic-steel Fiber Reinforced Recycled Aggregate Concrete

The waste concrete is used for the preparation of recycled aggregate concrete（RAC）after crushing,cleaning,screening and other procedures,which can achieve environmental and economic benefits.However,compared with natural aggregates,recycled aggregates have problems such as high water absorption,large crushing indicators,and many original cracks,so that the strength of RAC will be reduced to varying degrees.However,compared with natural aggregates,recycled aggregates have problems such as high water absorption,large crushing indicators,and many original cracks,so that the strength of RAC will be reduced to varying degrees.With the deepening of research on RAC,it is found that adding a certain amount of fiber to RAC can increase its tensile strength,flexural strength,inhibit creep,etc.,and significantly improve the ductility and toughness of concrete.However,most scholars at home and abroad focus their research on high elastic modulus fibers such as steel fiber,carbon fiber or basalt fiber.With the advancement of the industrial level,some synthetic fibers,such as high-performance polypropylene fibers（also known as plastic steel fibers）,have gradually attracted attention due to their high cost performance and excellent acid and alkali resistance.There are few studies on adding plastic steel fiber into reinforced RAC to prepare plastic steel fiber reinforced RAC,especially the impact resistance is rarely reported.To this end,this article uses a combination of experimental research and theoretical research to study the following aspects of plastic steel fiber reinforced RAC:（1）According to"Standard for Test Methods of Mechanical Properties of Ordinary Concrete"and"Standard for Test Methods of Fiber Concrete",19 groups of fiber concrete specimens were tested for basic mechanical properties.4 fiber content and 3 aggregate replacement rates are considered,and compared with steel fiber.The results show that:unlike steel fiber reinforced RAC,with the increase of fiber content,the cubic compressive strength of plastic steel fiber reinforced RAC has no obvious change,but the elastic modulus decreases slightly;The splitting tensile strength of the plastic steel fiber reinforced RAC is gradually improved,and the bending toughness is significantly improved,and both are significantly better than the corrugated steel fiber in this paper;In addition,it was found that,except for the bending toughness,the other mechanical properties all weakened with the increase in the replacement rate of recycled aggregate.（2）According to the drop-weight impact test method proposed by the ACI544 committee,the drop-weight impact test was carried out using a drop-weight impact test machine designed and improved by our own research group.And after the test,the fiber crack resistance performance was simply evaluated.The test factors mainly consider the replacement rate of recycled aggregates and fiber volume content.Comparing with steel fiber reinforced RAC,it is found that with the increase of fiber content,the initial crack resistance of plastic steel fiber reinforced RAC is not improved significantly,and it is significantly weaker than steel fiber;The plastic-steel fiber reinforced RAC is better than steel fiber reinforced RAC in terms of final crack（destructive）impact resistance and final crack resistance,as the fiber content increases.（3）The log-normal distribution and the two-parameter Weibull distribution are used to perform fitting analysis and failure probability prediction on the impact test results of fiber RAC specimens using mathematical statistical functions.The results show that the impact test results of both plastic steel fiber reinforced RAC and steel fiber reinforced RAC obey the log-normal distribution and the two-parameter Weibull distribution.And the P-ln N₂-V_frelationship curve can be used to predict the impact life under different failure probabilities.