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Zhiming Ma,Fangzhi Zhu,Tiejun Zhao 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.2
Surface waterproofing treatment with silane coupling agent is developed to prepare surface modification concrete, in recent years, which possesses an excellent permeability resistance. Freeze-thaw damage inevitable exists in concrete exposed to the cold environment, therefor this paper intensively investigates the effects of surface modification of silane coupling agent on the properties of concrete with freeze-thaw damage. Freeze-thaw cycles, capillary absorption, chloride penetration and carbonization tests were carried out, respectively. The results demonstrate that the surface waterproofing treatment is appropriate for the durability repairing of concrete with freeze-thaw damage, and the penetration depth of silane coupling agent in concrete increases linearly with the rise of freeze-thaw damage. The water and chloride permeability both increase with the increased freeze-thaw cycles for various concrete; however, the surface modification concrete has a better permeability resistance than ordinary concrete with the same freeze-thaw damage. In particular, the permeability resistance increases with the increases of applied amount of silane coupling agent, and there exists a good correlation between the permeability behavior and induced freeze-thaw damage for various concrete. Abrasion significantly decrease the permeability resistance of surface modification concrete, which should be considered carefully in the durability repairing.
Li Gao,Mei-Ling Zhuang,Fangzhi Zhu,Chuanzhi Sun,Jun Yang 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.5
The temperature stress in mass concrete structure is relatively high during construction, which usually leads to temperature cracks. To solve this problem, concrete blocks are usually placed by setting wide slots. Connecting the truncated steel bars at the position of the wide slots by welding or extruding sleeves has many disadvantages. To solve the problem of temperature-induced stress loss, a new type of slightly curved arc HRB400 (SCAHRB400) steel bars was proposed without cutting off the steel bars in this article. Tensile tests and numerical simulations were performed for five types of SCAHRB400 steel bars considering geometric and material nonlinearity. Based on the test results and numerical simulation results, the equivalent stress–strain relationships of SCAHRB400 steel bars were established, and the emergence of the plastic zone of SCAHRB400 steel bars in the tensile process were observed, the tensile properties of SCAHRB400 steel bars were analyzed and discussed. The test results indicate that SCAHRB400 steel bars are prone to local yielding near the crown of large arches and at the connection of horizontal and arc sections. The numerical simulation equivalent stress–strain curves have good regularity. The equivalent stress–strain curves of slightly curved arc HRB400 and HRB335 steel bars have the similar changing law. When the stress is small, the tensile stiffness and compressive axial stiffness of slightly curved arc HRB400 and HRB335 steel bars are similar; when the stress is large, the axial stiffness of SCAHRB400 steel bars is greater than that of slight curved arc HRB335 steel bars. Through test and numerical simulation studies, the theoretical basis can be established for the engineering application of new slightly curved arc steel bars in mass concrete.