| The promotion and application of crumb rubber concrete(CRC)can effectively reduce the number of waste tires,which not only protects the ecological environment,but also complies with the call for "Energy Conservation and Pollution Emissions Reduction" and the sustainable development strategy of our country.However,CRC has the disadvantage of low strength.The strength of CRC can be improved by mixing steel fibers and nano-silica to optimize its physical and mechanical properties.In order to further expand the use of CRC in the field of civil engineering,this thesis carried out experimental research on the basic mechanical properties of steel fiber nano-silica modified crumb rubber concrete(SFNS-CRC)and the bond performance of deformed steel bar with it,and focused on steel fiber volume fraction,nano-silica content,anchorage length,steel bar diameter and protective layer thickness on its bond performance with deformed steel bar.The main contents are as follows:(1)Through the actual measurement of the compressive strength,splitting tensile strength of 72 cubic specimens and the axial compressive strength of 36 prism specimens,the effect of the change of the amount of two modified materials on the failure morphology,compressive strength,split tensile strength and axial compressive strength of CRC specimens of two different strength grades(C35 and C45)was studied.Consequently,the calculation formulas for compressive strength,split tensile strength and axial compressive strength were fitted by considering the influence of steel fiber volume fraction and nano-silica content.(2)Through operating the pull-out test of 80 central bonding specimens and comparing with the unmodified crumb rubber concrete bonding specimens,the influence of the quantity of two modified materials on the bonding specimens failure pattern,initial bond strength,ultimate bond strength and bond-slip curve of two different strength grades of CRC(C35 and C45)was analyzed.And the influence of the thickness of protective layer,the diameter of the steel bar and the anchorage length on the bond performance of SFNS-CRC bonding specimens with the strength grade of C35 was also studied emphatically.Moreover,the strengthening mechanism of nano-silica and steel fiber was investigated.A formula for calculating ultimate bond strength was established that comprehensively considered the influence of steel fiber volume fraction,nano-silica content,anchorage length,diameter of steel bar and thickness of protective layer.(3)The effect of anchorage length and protective layer thickness on the distribution curve of bond stress was discussed through the local bond slip test of 20 steel bars slotted and pasted strain gauges.Based on the theory of thick wall cylinder of elastic mechanics,the theoretical calculation formula of bond strength was established.A bond-slip constitutive relationship model considering the influence of steel fiber volume fractio n and nano-silica content was proposed. |
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