| The strengthening methods using fiber reinforced polymer(FRP)and wire-mesh reinforced mortar(WRM)are now popular in the field of structural strengthening and rehabilitation.At present,epoxy resin is often used as adhesive agent in FRP strengthening.However,this organic matrix is lack of high temperature resistance.Also,the cement used in WRM strengthening is a major source of greenhouse effect.Based on the disadvantages of above two strengthening methods,the materials used in strengthening are changed to improve strengthening effects,so two new methods called carbon fiber reinforced geopolymer(CFRG)strengthening and wire-mesh reinforced geopolymer mortar(WRGM)strengthening are presented.The feasibility of using CFRG and WRGM to strengthen concrete columns and the study on the durability of geopolymer mortar are carried out.The detailed contents of this paper are as follows:1.Axial compression tests were conducted on 20 CFRG strengthened cylinders at room temperature and after high temperatures.Test results show that:(1)The ultimate load increase of CFRG strengthened cylinders with one,two and three layers of fiber sheets than unstrengthened cylinders at room temperature is 16.5%,41.8%and 72.4%respectively,and the increase in ultimate deformation is 153.3%,212.4%and 336.7%respectively.It can be seen that the CFRG strengthened system exhibits good restraint to the cylinder.(2)CFRG strengthened cylinders exhibit good high temperature resistance.With the temperature increases from 100 ? to 300 ?,the ultimate load of strengthened cylinders gradually decreases,and the maximum decrease is 16.8%.(3)The failure mode of CFRG strengthened cylinders with one,two and three layers of fiber sheets at room temperature are all slip failure at the overlap position of fiber sheets.After high temperatures,the failure mode of CFRG strengthened cylinders changes from slip failure to rupture of carbon fiber sheets at 300 ?.Based on the calculation formula for ultimate load of CFRG strengthened cylinder at room temperature,along with the experimental data after high temperatures,the formula for ultimate load of CFRG strengthened cylinder after high temperatures is presented.The calculated values agree well with experimental results.2.The flexural,compressive and tensile strength tests of geopolymer mortar prepared by 8 different formulas at room temperature were carried out,and the preferred formula of geopolymer mortar was obtained.The flexural,compressive and tensile strength of geopolymer mortar prepared by the preferred formula were compared with those of commercial geopolymer mortar.Then,axial compression tests of wire-mesh reinforced geopolymer mortar(WRGM)strengthened cylinder at room temperature and after high temperatures were carried out.Test results show that:(1)When binder-aggregate ratio,water-binder ratio and polypropylene fiber content of GM are 1.5,0.34,and 1.5 kg/m3 respectively,the flexural,compressive and tensile strength of GM at 3 d and at room temperature are 8.5Mpa,50.5MPa and 3.95MPa respectively.No obvious reduction of strength occurs below 300?.(2)The strengthening effect of WRGM confined cylinders at room temperature and after 100? is slightly higher than that of WRPM,the strengthening effect of WRGM is comparative to that of WRPM after 300 and 500?,and the strengthening effect of WRGM is higher than that of WRPM after 700?.Based on the calculation formula for ultimate load of WRGM confined cylinders at room temperature,along with the experimental data after high temperatures,the formula for ultimate load of WRGM confined cylinders after high temperatures is presented.The calculated values agree well with experimental results.3.Experimental study on the chemical corrosion resistance property of geopolymer mortar to sulfuric acid and sodium chloride was carried out.Test result show that:(1)The mechanical properties of geopolymer mortar in sodium chloride solution and sulfuric acid solution are basically the same with those of geopolymer mortar in tap water.Compared with GM specimens in air,the strength ofGM specimens in sodium chloride solution and sulfuric acid solution decreases,and the maximum decreases are 15.5%,13.7%and 10.9%respectively.(2)The exterior of geopolymer mortar is almost unchanged,and the mass of geopolymer mortar in sodium chloride solution and sulfuric acid solution changes a little.(3)For geopolymer mortar specimens in sulfuric acid solution,the strength and mass loss rate of GM are not less than those of cement-based composites such as Portland cement concrete and slag Portland cement concrete. |
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