Research On Properties Of Protective Materials Of Maincable Strand And Bearing Of Suspention Structure

The main cable and bearing are important structures to make the suspension bridge work, and the protective effect is the major factor to guarantee the service life of suspension bridges. In this paper, with the aid of total reflection infared scaning(ATR-FTIR), electrochemical impedance spectroscopy test(EIS) and any other research methods, we tested the protective coating of the main cable strands and protective materials of the bearing under the environment of natural exposure aging and ultraviolet artificial accelerated aging, comparatively studied the protective effect of zinc coating, epoxy coating, high density polyethylene(HDPE) coating and polyurea coating on the main cable strand, and mechanical properties of natural rubber, neoprene, high damping rubber and spray polyurea as the bridge bearing. Through the study we have got the following conclusions:1.The visual testing result of main cable strand under wetting-redrying and media immersion environment showed that, zinc coating and epoxy coating which cause corrosion at the end of the steel strand after 10 d exposed to air have poor corrosion resistance, and EIS testing result showed that coatings were about to enter the later corrosion; the steel strand wrapped in HDPE coating and polyurea coating has not changed much after 150d’s trial, and EIS testing result showed that coatings still had large resistance and good protective properties.2.The result of bearing protective materials corrosive medium showed that, after immersion in 5wt%H2SO4, the change rate of neoprene in tensile strength, breaking elongation, tearing strength and hardness(Shore A) were all higher than natural rubber, high damping rubber and polyurea, the decline rate were all greater than 30%, the mechanical properties of other three materials were relatively stable which change rate at 20%, the change rate of tensile strength of high damping rubber was +3.90%, the breaking elongation of polyurea was-8.8% which had the smallest change rate, the tearing strength of natural rubber rose by 11.35%, the change rate of hardness of these three materials were all within 10%; after immersion in 5wt%NaOH, the change rate of neoprene in tensile strength, breaking elongation, tearing strength and hardness(Shore A) were all higher than natural rubber, high damping rubber and polyurea, the decline rate were all greater than 30%, the mechanical properties of other three materials were relatively stable; after immersion in seawater, in addition to the decline rate nearly by 30% of neoprene, the mechanical properties of these four materials were all relatively stable; the infrared spectroscopy result showed that internal structure of all materials almost unchanged, just suffered different degrees of change on the surface of materials,which illustrated the stability of materials.3. The result of bearing protective materials after 300d’s aging resistance testing(natural environment and ultraviolet artificial accelerated environment) showed that, in natural environment, neoprene had greatest change rate of tensile strength, breaking elongation and hardness(Shore A) which were-22.98%,-45.49% and-19.75% respectively, polyurea had the most stable change rate of tensile strength, breaking elongation and hardness(Shore A) which were+0.49%、-12.70% and 0.00% respectively; in ultraviolet artificial accelerated environment, neoprene had greatest change rate of tensile strength, breaking elongation and hardness(Shore A) which were-30.40%,-53.63% and-19.75% respectively, polyurea had the most stable change rate of tensile strength, breaking elongation and hardness(Shore A) which were +4.58%、-9.44% and 0.00% respectively; the infrared spectroscopy result showed that internal structure of all materials almost unchanged, just suffered different degrees of change on the surface of materials,which illustrated the stability of materials.4. The result of bearing protective materials after 60 freez-thaw cycle testing showed that, the change rate of tensile strength of natural rubber, neoprene, high damping rubber and polyurea was respectly +2.34%, +9.63%, +13.01% and-22.31%, the change rate of breaking elongation was respectly-9.10%,-13.61%, +0.12% and-10.03%, the change rate of hardness(Shore A) was respectly 0.00%, +6.35%,-30.00% and +6.75%; the infrared spectroscopy result showed that internal structure of all materials almost unchanged, just suffered different degrees of change on the surface of materials,which illustrated the stability of materials.The experimental study shows that: As the protective materials of main cable strand, the protective properties of polyurea coating is better than that of zinc coating and epoxy coating, and as good as HDPE coating. As the protective materials of suspension bridge bearing, the polyurea has quiet a anti-corrosion performance of these three rubbers above, and has a better aging resistance performance than any other materials.Consequently, the experimental research provides application foundation for polyurea applied to protect main cable strand and bearing of suspension bridges as a new protective material.