Basing half-cell potential method estimating steel corrosion rate in concrete was studied in this paper. The exponential relationship between the corrosion current and the corrosion potential was regressed by the data collected from the linear polarization method experiment. Potential collected by the half-cell potential method and linear polarization resistance method in the experiment were close, it is reasonable to using regression equation. Regression equation was applied to analysis steel corrosion rate in a concrete structure column.
Many studies have focused on the flexural behavior of conventional reinforced concrete (RC) beams strengthened with fiber reinforced polymer (FRP) bonded on the bottom surface; however, rare attempt is made to strengthen RC beams with FRP bonded on the side surface, furthermore, as for the comparative study of the both is even more scarce.Based on the existing bending experimental data of RC beams externally strengthened with FRP, the flexural capacity calculation formula of normal section of RC beams strengthened with FRP bonded on the side or bottom surface was deduced in the paper. In addition, a comparative analysis on the strengthening effect between bottom bonded FRP and side bonded FRP was made. The results indicated that the ultimate load-carrying capacity of the former was slightly lower than the later.
The compressive strengths of the concrete cubes added fly ash were increased 53.2%, the density was almost unchanged, but the water absorption was decreased 30%. The concrete permeability coefficient and chloride diffusion coefficient added fly ash were lower than the common concrete at all ages. The concrete specimens corrosion potential added fly ash were higher than-300mV, while common concrete almost were lower than-500mV. Corrosion probability was small and there was no crack and corrosion pot on the surface of the specimens until 82 times cycles in wet-dry chlorides solution. Fly ash in concrete has obvious act for improving concrete behavior in protecting the embedded steel in corrosion.
Based on the fatigue test for flexural performance of five reinforced concrete beams, the variation characteristics of the crack development, concrete strain, steel strain, fiber strain with the cycle number of the fatigue load were analyzed, and the effect of hybrid fiber sheets and basalt fiber reinforced polymer(BFRP)sheets on flexural fatigue performance of the strengthened beam was studied. The results show that the accumulated damage of RC beams strengthened with hybrid fiber sheets was slowed down significantly, the anti-crack property was much improved, and the fatigue life was greatly prolonged. Compared with the ordinary RC beam and the RC beam strengthened with double BFRP sheets, the fatigue life of RC beams strengthened with hybrid CFRP/BFRP(C/BFRP) sheets and hybrid CFRP/GFRP(C/GFRP) sheets was increased by 291.26%, 298.63% and 10.73%, 13.53%.
The influences which were caused by difference of produced methods and original concrete on the performance of recycled aggregate have been studied in this paper. Moderate reprocessing of recycled aggregate can effectively improve the performance. Higher strength matrix concrete, better the performance of recycled aggregate, and the recycled concrete strength will be higher also. Original concrete has little effect on the performance of recycled aggregate.
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