Study On Early Age Mechanical Properties Of Waste Fiber Recycled Concrete

Concrete is indispensable in modern civil engineering.At the same time,due to its waste of natural resources and serious damage to the environment,the research of recycled aggregate concrete had attracted enough attention.In addition,human activities produced a large number of non-degradable waste fibers,its impact on environment cannot be ignored.Therefore,through study the influence of different replacement rates of recycled aggregates(RAs)and volume contents of waste fibers on the basic mechanical properties in early age and tensile creep of waste fiber recycled concrete(WFRC),to further research and application of WFRC.Main achievements are as follows:1.Through the test of RAs,the characteristics of high porosity and water absorption of recycled coarse aggregate were determined.At the same time,RAs brought defects to concrete material.2.Through the compressive strength test of the early age standard specimens of WFRC,to investigate the influence of recycled aggregates and waste fibers on compressive strength in early age.The results showed that RAs and waste fibers increased the strength of concrete at early age,but reduced concrete strength in day 28.The reason was that RAs boosted concrete early strength,but its original defects decreased the compressive strength;waste fibers had dual effects of crack resistance and looseness,and the result of double effects were to increase the early strength of the WFRC,and slightly reduced the compressive strength in day 28.3.Through tensile creep tests of WFRC,the influence of different replacement rates of RAs and volume contents of recycled fibers on the development of tensile creep were studied.Found out that whether RAs or waste fibers were single or mixed,RAs increased the creep of WFRC,and the increasing extent became larger with specimens further loaded;Waste fibers inhibited the development of tensile creep of WFRC.The effect became more obvious when loading time became longer.4.Compared the test data of axial tensile creep tests of WFRC with the current creep prediction models,found that the commonly used creep prediction model cannot predict the tensile creep of WFRC,but the modified ?Stargaard model can better predict the differentcontents of RAs and waste fibers,thus a prediction model of tensile creep for WFRC was established.