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Research on Corrosion Effect of Sulfate Ions on Concrete Under wetting-drying cycle

Journal of Ocean University of China 2022年第1期21卷 124-130页

作者： WANG Xiuhai TIAN Zhuangcai ZHANG Yanan SU Xiuting LIU Hongjun LIU Tao College of Environmental Science and Engineering Ocean University of ChinaQingdao 266100China Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116China

Saline soil is widely distributed in the marine sediments along the coast of the world and the arid-semi-arid areas of the Middle East and Iraq,and calcium sulfate erosion has become one of the important factors affecting the durability of concrete in this *** order to clarify the mechanism of sulfate ion damage to concrete,this paper mainly takes saline soil with high sulfate content in coastal area as well as arid-semi-arid area as the research object,and uses indoor geotechnical test,field test and numerical simulation to study the influence of different dry-wet cycle times on the unconfined compressive strength of concrete test blocks,and puts forward the relationship between the erosion arrival depth and time of sulfate ion in concrete,so as to predict the long-term erosion depth by using the erosion depth of sulfate ion in concrete in short *** results show that the shorter the erosion time when the erosion reaches a certain depth,and the larger the erosion reaches when the erosion time is the same,the faster the erosion reaches the depth with the increase of erosion *** with rectangular section concrete,circular section concrete penetrates *** results of this study can provide a reference for the durability design of concrete in saline soil sites containing sulfate.

关键词： wetting-drying cycle sulfate ion concrete corrosion

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Development and application of an instrument for simulating wetting-drying cycles of expansive soils under loads

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Journal of Mountain Science 2018年第11期15卷 2552-2560页

作者： DONG Jun-gui LV Hai-bo WU Wei School of Civil Engineering and Transportation South China University of Technology Guangzhou 510641 China College of Civil Engineering and Architecture Guilin University of Technology Guilin 541004 China

Alternating rainfall and evaporation in nature severely impact the shear strength of expansive soils. This study presents an instrument for simulating the effect of wetting–drying cycles on the strength of expansive soils under different loads, and its testing error is verified. With this instrument,direct shear tests were performed on samples experiencing 0-6 cycles under vertical loads of 0 kPa,5 kPa, 15 kPa, and 30 k Pa. The results found that this instrument provides a new method for evaluating the effects of wetting–drying cycles on soils, and this method represents actual engineering conditions more accurately than do preexisting methods. It accurately controls the water content within 1% while simulating the specified loads at different soil *** is significantly affected by wetting–drying cycles, while the friction angle is not as sensitive to these cycles. Decrease in shear strength can be attributed to the fissures in soils caused by wetting–drying cycles. The existence of vertical loads effectively restricts shrinkage fissuring and cohesion attenuation, consequently inhibiting the attenuation of shear strength.

关键词： Expansive soils wetting-drying cycle Instrument Load Shear strength

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Accelerating Effect of wetting-drying cycles on Steel Bar Corrosion in Concrete

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Journal of China University of Mining and Technology 2005年第3期15卷 197-202页

作者： LI Guo YUAN Ying-shu LI Fu-min School of Architecture and Civil Engineering China University of Mining and Technology Xuzhou Jiangsu 221008 China

Raining and sun-shining processes in natural climate were simulated by water spraying and infrared lightshining alternately as wetting-drying cycles in accelerated durability test. The accelerating effects of the wet-ting-drying cycles and the variation of corrosion current density and corrosion potential of steel bar in concrete undersuch conditions were studied. The result shows that the main reason leading to accelerating corrosion of steel bar inconcrete is the wetting-drying cycles, which can cause the increase of corrosion potential difference between the an-ode and cathode of steel bar corrosion cell and the decrease of concrete resistance. Corrosion rate of the steel bar inconcrete under four typical conditions, including wetting-drying cycle, long time submerging in water, long time ex-posure to indoor and outdoor environment were measured and compared. The test results indicate that the corrosionrates under the four typical conditions are in the order of spraying and infrared light shining cycles, outdoor environ-ment, indoor environment, and submerging in water, respectively.

关键词： wetting-drying cycle concrete steel bar corrosion rate

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Effect of cyclic wetting-drying on tensile mechanical behavior and microstructure of clay-bearing sandstone

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International Journal of Coal Science & Technology 2021年第5期8卷 956-968页

作者： Pingye Guo Juan Gu Yi Su Jiong Wang Zhanwen Ding State Key Laboratory for Geo-Mechanics and Deep Underground Engineering Beijing 100083China School of Mechanics Architecture and Civil EngineeringChina University of Mining and TechnologyBeijing 100083China Tang Steel International Engineering Technology Corp Tangshan 063000China China Henan Geological and Mineral Resources Construction Engineering(Group)Co. LtdZhengzhou 450007China

The understanding of the weakening mechanism of tensile strength of rock subjected to cyclic wetting-drying is critical for rock *** strength tests were conducted on a total of 35 sandstone specimens with different wetting-drying *** crack propagation process and acoustic emission characteristics of the tested samples were obtained through a high-speed camera and acoustic emission *** results indicate that the tensile strength is observably reduced after cyclic wetting-drying,and the extent of the reduction is not only related to the number of wettingdrying cycle,but also closely related to the clay mineral content of the *** addition,as the cycles of wetting-drying increase,the effect of each single cycle on tensile strength get reduced until it becomes ***,the crack initiation and penetration time is prolonged as the number of wetting-drying cycle increases,which indicates that cyclic wetting-drying weakens the rock stiffness and enhances the ductility of ***,the acoustic emission characteristics of the tested samples further confirmed the ductile behaviour of the sandstone samples with increasing wetting-drying ***,through the analysis of the microstructure and mineral composition of the samples with different wetting-drying cycles,it is concluded that the main weakening mechanisms of sandstones containing clay minerals are frictional reduction,chemical and corrosive deterioration.

关键词： Sandstone wetting-drying cycle Tensile strength Weakening mechanism Failure characteristics

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Change in Grain-Size Composition of Lignite under Cyclic Freezing-Thawing and wetting-drying

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Natural Resources 2024年第1期15卷 17-27页

作者： Natalia S. Batugina Vladislav I. Fedorov Chersky Institute of Mining of the North Siberian Branch Russian Academy of Sciences Yakutsk Russia

The paper presents the change in grain-size composition of lignite under cyclic freezing-thawing (FTC) and wetting-drying (WDC). The article shows that in the spring and autumn periods the lignites can be subjected to repeated freezing-thawing and wetting-drying, which determines the possibility of changing their grain-size composition and structure. Experimental studies in laboratory conditions on the influence of cyclic freezing-thawing (FTC) and wetting-drying (WDC) on the quality indicators of lignites have been carried out, their granulometric (fractional) composition has been studied. Freezing-thawing cycle conditions are as follows (FTC): minimum exposure temperature: -20°C;maximum: +5°C;relative humidity: 30%;number of processing cycles: 3. wetting-drying cycles are as follows (WDC): drying temperatures are +20, +40, +60, +80°C, drying time 90 minutes, the coals are further subjected to rain (soaking) for a period of water saturation to humidity of 30% - 40% and dry again. The number of wetting-drying cycles is 3 times. The tests have revealed the destructive effects of FTC and WDC on the samples of lower metamorphic grade coal, and the cycles of wet-dry lead to the much higher yield of fine sizes (-6+0;-13+0 mm) than the cycles of freeze-thaw. Furthermore, it is found that the increase in the yield of fines depends on the heating temperature: coal disintegration proceeds more intensively at a higher temperature of drying.

关键词： Lignite Freezing-Thawing cycle wetting-drying cycle Grain Size Composition Dust Coal Storage Loss Quality

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Desiccation cracking remediation through enzyme induced calcite precipitation in fine-grained soils under wetting drying cycles

Biogeotechnics

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Biogeotechnics 2023年第4期1卷 13-27页

作者： Kaniz Roksana Shaini Aluthgun Hewage Melissa Montalbo Lomboy Chaosheng Tang Wei Xue Cheng Zhu Department of Civil and Environmental Engineering Rowan UniversityGlassboroNJ 08028USA Experiential Engineering Education(ExEEd) Rowan UniversityGlassboroNJ 08028USA School of Earth Sciences and Engineering Nanjing UniversityNanjing 210046China Department of Mechanical Engineering Rowan UniversityGlassboroNJ 08028USA

The effects of desiccation cracking in clay soils on geotechnical constructions are *** study investigates the viability of utilizing Enzyme-induced calcite precipitation(EICP),a bio inspired approach,as a potential solution for addressing desiccation cracking in fine-grain *** the EICP technique,crude soybean extract is employed for the purpose of urea *** fluid samples,including a control sample,a cementation solution containing 1 M urea,0.675 M CaCl_(2),and 4 g/L milk,along with various concentrations of enzyme solutions(3-80 g/L),were tested for the *** evaluate the surface cracking patterns,the method involved constant monitoring and photo recording using a high-resolution camera aided by image processing *** results showed that fine-grain soils improved from increased calcite precipitation and decreased desiccation cracking intensity when the EICP method was *** and enzyme solution with low concentrations(3 g/L and 10 g/L)had similar effects on crack remediation,suggesting a modest *** contrast to the sample treated with water,the crack network remained unaltered in this ***3 precipitation within the void area kept the crack network in place even as the void thickness decreased at increasing enzyme concentrations(30 g/L,50 g/L,and 80 g/L).wetting and drying cycles were found to decrease the crack ratio,crack width,and crack length in the EICP-treated sample,particularly under higher concentrations of urease *** enzyme concentrations of 3 g/L and 10 g/L have minimal impact on crack remediation but effectively inhibit new crack ***,higher enzyme concentrations result in calcium carbonate precipitates,forming a soil crust and increasing surface *** study aims to enhance understanding of the EICP methodology and to provide novel perspectives on potential uses for soil enhancement.

关键词： Desiccation crack wetting-drying cycle Bio cementation Plant-based EICP

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