Zhou Jiguo, Wang Guihua, Liu Peng, Guo Xuefeng, Xu Jun
College of Civil Engineering, Baicheng Normal University, Baicheng 137099, China.
College of Civil Engineering and Architecture, Jiangsu University of Science and Technology, Zhenjiang 212003, China.
Materials (Basel). 2022 Jun 21;15(13):4380. doi: 10.3390/ma15134380.
To determine how the performance of concrete changes after initial load damage and salt freezing, concrete samples were first subjected to loading and unloading, and were then put into salt solutions to carry out rapid freeze-thaw cycle (FTC) experiments. Salt solutions were created based on the saline soil of western Jilin, China, for use in salt freeze-thaw testing. This determined the change law of the compressive strength and the dynamic elastic modulus (DEM). Additionally, low-field nuclear magnetic resonance technology and a scanning electron microscope were applied to investigate the pore characteristics and microstructure of concrete samples after FTCs. This study found that when the concrete specimens were subjected to an initial load of 0.3 under 50 FTCs, the loss in the compressive strength increased by 24% when the concrete was subjected to freeze-thaw cycles in freshwater and increased by 24% when concrete was subjected to freeze-thaw cycles in a 6.8% composite salt solution compared with the specimens without the initial load. When the concrete was subjected to FTCs in a 6.8% composite salt solution 50 times, the loss in the compressive strength increased by 110% for concrete without an initial load and increased by 109% when the concrete was subjected to an initial load of 0.3 compared with the specimens under FTCs in freshwater. The persistent effect of the FTCs also aggravated chloride ion erosion in the concrete, which gradually reduced the concrete's permeability resistance. Internal pores in the concrete, especially the proportion of above-medium-sized pores, gradually increased along with the increase in the number of FTCs. There is a good linear correlation between the change rule of compressive mechanical properties and the change rules of mass, DEM, and pore characteristics inside the concrete under rapid FTCs in different salt solutions.
为了确定混凝土在初始加载损伤和盐冻后性能如何变化，首先对混凝土试件进行加载和卸载，然后将其放入盐溶液中进行快速冻融循环（FTC）试验。基于中国吉林西部的盐渍土配制盐溶液，用于盐冻融试验。由此确定了抗压强度和动态弹性模量（DEM）的变化规律。此外，应用低场核磁共振技术和扫描电子显微镜研究了FTC试验后混凝土试件的孔隙特征和微观结构。研究发现，当混凝土试件在50次FTC试验下承受0.3的初始荷载时，与未承受初始荷载的试件相比，在淡水中进行冻融循环时，抗压强度损失增加了24%，在6.8%的复合盐溶液中进行冻融循环时，抗压强度损失增加了24%。当混凝土在6.8%的复合盐溶液中进行50次FTC试验时，与在淡水中进行FTC试验的试件相比，未承受初始荷载的混凝土抗压强度损失增加了110%，承受0.3初始荷载的混凝土抗压强度损失增加了109%。FTC试验的持续影响还加剧了混凝土中氯离子的侵蚀，逐渐降低了混凝土的抗渗性。混凝土内部孔隙，特别是中等以上尺寸孔隙的比例，随着FTC次数的增加而逐渐增大。在不同盐溶液快速FTC试验下，混凝土抗压力学性能的变化规律与质量、DEM和内部孔隙特征的变化规律之间存在良好的线性相关性。
