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| 1 | Deterioration Mechanism of Sulfate Attack on Concrete under Freeze-thaw Cycles显示文摘The experiments of concrete attacked by sulfate solution under freeze-thaw cycles were investigated. The sulfate solution includes two types of 5% Na 2 SO 4 and 5% MgSO 4. Through the experiment, microstructural analyses such as SEM, XRD and TGA measurements were performed on the selected samples after freeze-thaw cycles. The corrosion products of the concrete were distinguished and quantitatively compared by the thermal analysis. Besides, the damage mechanism considering the dynamic modulus of elastically of concrete under the coupling effect was also investigated. The experimental results show that, under the action of freeze-thaw cycles and sulfate attack, the main attack products in concrete are ettringite and gypsum. The corrosion products exposed to MgSO 4 solution are more than those to Na 2 SO 4 solution. Furthermore, the content of gypsum in concrete is less than that of ettringite in test, and some of gypsum can be observed only after a certain corrosion extent. It is also shown that MgSO 4 solution has a promoting effect to the damage of concrete under freeze-thaw cycles. Whereas for Na 2 SO 4 solution, the damage of concrete has restrained before 300 freeze-thaw cycles, but the sulfate attack accelerates the deterioration process in its further test period. | NIU Ditao JIANG Lei FEI Qiannan | 2013 | Journal of Wuhan University of Technology(Materials Science)2013，28，6： | 7 |
| 2 | Damage Evolution of Concrete under the Actions of Stray Current and Sulphate显示文摘Based on the mechanism of stray current generation in underground structures,the concrete durability test device for stray current and sulphate in typical soil environment was designed to study the damage of concrete under the action of stray current and sulphate.The deterioration law of concrete under the action of stray current and sulphate was studied by microscopic techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD).The microstructure of corroded concrete was observed to determine the phase composition of erosion products.The damage performances such as quality,strength,and dynamic elastic mode of corroded concrete were performed.The experimental results show that,under the action of stray current,the products of sulfate-eroded concrete are mainly gypsum,ettringite,and thaumasite;the stray current accelerates the hydration process of cement and the erosion of concrete by sulfate;when the concrete pores are filled with the erosion product,there is an increase of approximately 10% in the concrete compressive strength and dynamic elastic modulus;and the concrete compressive strength is more sensitive to the stray current electrification period than the current intensity. | 张路 文波 NIU Ditao JI Zhiyuan | 2021 | Journal of Wuhan University of Technology(Materials Science)2021，36，4： | 4 |
| 3 | Experimental test of corrosion- induced concrete cover cracking pattern 显示文摘 | Niu Ditao Hua Song | 2012 | Advanced Materials Research2012，，： | 1 |
| 4 | Study of the performance of steel fiber reinforced concrete to water and saltfreezing condition显示文摘 | Ditao Niu Lei Jiang Min Bai Yuanyao Miao | 2013 | Materials and Design2013，44，： | 1 |
| 5 | Stress-strain model of PVC-CFRP confined concrete column subjected to axial compression 显示文摘 | Yu Feng Niu Ditao | 2010 | International Journal of Physical Sciences2010，5，15： | 1 |
| 6 | Stress-strain model of PVC-FRP confined con- crete column 显示文摘 | Feng Yu Ditao Niu | 2010 | International Journal of physical science2010，5，15： | 1 |
| 7 | Research on the Variation of pH Value of the Ordinary Concrete and FlyAsh Concrete in the Carbonation Process显示文摘 | Guangzheng Qi Ditao Niu | | 0，，： | 1 |
| 8 | Stress-strain model of PVC-FRP confined concrete column 显示文摘 | Yu Feng Niu Ditao | 2010 | International Journal of Physical science2010，5，15： | 1 |
| 9 | Stress-strain model of PVC-CFRP confined concrete column显示文摘 | Yu Feng Niu Ditao | 2010 | International Journal of the Physical Science2010，15，5： | 1 |
| 10 | Stress-strain model of PVC-FRP confined con-crete coluran显示文摘 | Feng Yu Ditao Niu | 2010 | International Journal of Physical Science2010，5，15： | 1 |
| 11 | Influence of freeze-thaw damage gradient on stress-strain relationship of stressed concrete显示文摘Freeze-thaw damage gradients lead to non-uniform degradation of concrete mechanical properties at different depths.A study was conducted on the stress-strain relationship of stressed concrete with focus on the freeze-thaw damage gradient.The effects of relative freeze-thaw depths,number of freeze-thaw cycles(FTCs)and stress ratios on the stress-strain curves of concrete were analyzed.The test results demonstrated that freeze-thaw damage was more severe in the surface layers of concrete than in the deeper layers.The relative peak stress and strain of concrete degraded bilinearly with increasing depth.The stress-strain relationship of stressed concrete under FTC was established,and it was found to agree with the experimental results. | Xiguang LIU Yongjie LEI Yihao SUN Jiali ZHOU Ditao NIU | 2023 | Frontiers of Structural and Civil Engineering2023，17，9： | 0 |
| 12 | Effects of Mineral Admixtures on Chloride Diffusion in Environment-Friendly Coral Aggregate Concrete显示文摘Coral materials can replace concrete aggregates and achieve material self sufficiency for reducing the construction costs of island projects.This paper studies the effects of different mineral admixtures on the properties of coral aggregate concrete(CAC).The chloride concentration of CAC after different erosion times is measured using the potentiometric method,and the porosity of the CAC is ca lculated using thermogravimetric and drying methods.The chloride concentration of the CAC presents a two-phases dis tribution.The peak chloride concentration fol-lowed a power function,increasing with the erosion time.The chloride diffusion coefficient of CAC is 7.9%-37.5%larger than that of ordinary aggregate concrete,and the addition of 15% fly ash and 5%silica fume can significantly reduce the chloride diffusion coefficient,with a maximum reduction of 45.0%.The porosity obtained via the thermogravimetric and drying methods is well correlated.The porosity has a strong negative correlation with the compressive strength and a strong positive correlation with the chloride diffusion coefficient. | Daguan Huang Ditao Niu Li Su Hao Zheng Qiang Fu Yunhe Liu | 2022 | Journal of Renewable Materials2022，10，12： | 0 |
| 13 | Hydration Characteristics and Microstructure of Alkali-Activated Slag Concrete: A Review显示文摘Alkali-activated slag concrete (AASC) is a new green building material. The amount of CO_(2) produced by AASC is 1/5th of that produced by ordinary Portland cement concrete (OPCC). In addition, AASC promotes the reuse of slag and other wastes and saves resources. Furthermore, the scope of use of slag has been expanded. The progress of the research on the hydration characteristics, microstructure, interfacial transition zone, and pore structure of AASC based on the relevant literatures was analyzed and summarized in this study. The influences of the slag composition, the type and dosage of the alkali activator, and the curing conditions on the hydration characteristics and the microstructure of the AASC were discussed. Relatively few research results on the microstructure of AASC are available, and the relevant conclusions are not completely consistent. Moreover, there are many constraints on the development of AASC (e.g., complex composition of raw materials of slag, large shrinkage deformation, and low fluidity). Therefore, further research is required. | Qiang Fu Mengxin Bu Zhaorui Zhang Wenrui Xu Qiang Yuan Ditao Niu | 2023 | Engineering2023，，1： | 0 |
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