Chloride retention mechanism of coral sand cement stones modified by graphene oxide
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摘要: 珊瑚砂地基远离大陆，在海洋环境下通过注浆或搅拌桩等工艺注入极少掺量氧化石墨烯（GO）的水泥浆液改善珊瑚砂地基，可以大幅提升珊瑚砂水泥结石体阻滞氯离子渗透性能。本文通过快速氯离子迁移试验（RCM方法）、扫描电镜（SEM）实验和Image-Pro Plus图像处理等，在对比分析河砂与珊瑚砂颗粒形态差异以及掺入GO前后微观结构变化规律的基础上，揭示了GO改性珊瑚砂水泥结石体阻滞氯离子渗透的作用机理。试验结果表明：颗粒棱角度高、形状不规则、多孔且含有内孔隙等原因是相同工艺条件下珊瑚砂水泥结石体阻滞氯离子渗透性远低于河砂水泥结石体的主要原因；当掺入质量分数0.02%的GO后，28 d和56 d的珊瑚砂水泥结石体阻滞氯离子渗透性能指标提升程度最高（39.43%与48.93%），并与相同工艺条件下无添加GO的普通河砂水泥结石体指标相近；珊瑚砂水泥结石体阻滞氯离子渗透性能提升程度与GO掺量有关，两者先呈正相关而后呈负相关，0.02%质量分数为本文最佳试验掺入量；调控水泥水化产物生成规整有序的水化晶体形状，改善界面过渡区的形貌，填充内部裂纹的空间，修复孔隙的形貌特征是掺入GO影响珊瑚砂水泥结石体抗氯离子渗透性的主要原因。Abstract: In the marine environment far away from the mainland, the coral sand foundation can be improved by injecting the cement grout with a very small amount of graphene oxide (GO) through grouting or mixing piles and other processes, which can greatly increase the stone body’s ability to block chloride ion penetration. Based on the comparative analysis of the difference in the particle morphology of river sand and coral sand and changes in hydration products and microstructure before and after GO incorporation, this study employed a rapid chloride ion migration test, scanning electron microscope experiment, and Image-Pro Plus image processing to reveal the mechanism of the modified coral sand cement stone body blocking permeation by chloride. The result reveals that high particle angles, irregular shapes, and porous and internal pores are the main reasons for the lower coral sand cement stone body than the river sand cement stone body in blocking chloride ion permeability under the same process conditions. After mixing 0.02% (mass fraction) GO, 28 d and 56 d coral sand cement stones have the highest degree of improvement in blocking chloride ion permeability (39.43% and 48.93%) and are similar to those of ordinary river sand cement stones without GO addition under the same process conditions. The coral sand cement stone body’s antichloride ion penetration performance improvement is related to the amount of GO. The two are first positively correlated and then negatively correlated. 0.02% is the best mix-up measure after the experiment in the assay. Regulating cement hydration products to form a regular and orderly hydrated crystal shape, improving the morphology of the interface transition zone, filling the space of internal cracks, and repairing the morphological characteristics of the pores are the main reasons that allow the incorporation of GO to affect the resistance of coral sand cement stones to chloride ion permeability.
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Key words:
- coral sand /
- stone body /
- graphene oxide /
- chloride ion penetration /
- microstructure /
- mechanism of retention
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图 1 试验用砂．（a）珊瑚砂宏观图；（b）河砂宏观图；（c）珊瑚砂微观图；（d）河砂微观图
Figure 1. Sand used in the test: (a) macroview of coral sand; (b) macroview of river sand; (c) microview of coral sand; (d) microview of river sand
图 3 GO的AFM图像．（a）GO的AFM形貌图像；（b）GO的三维形貌
Figure 3. AFM image of GO: (a) AFM topography image of GO; (b) three-dimensional topography of GO
图 5 氯离子迁移系数测定展示图．（a）氯离子迁移系数测定仪；（b）测定方法示意图
Figure 5. Display diagram of the determination of chloride ion mobility coefficient: (a) chloride ion mobility coefficient tester; (b) schematic diagram of the measurement method
图 6 不同GO掺量试块的氯离子迁移系数图
Figure 6. Chloride ion mobility coefficient of the specimen with different GO contents
图 7 不同GO掺量28 d试块的SEM图．（a）0% GO，1000×，河砂试块；（b）0.03% GO，1000×，河砂试块；（c）0% GO，1000×，珊瑚砂试块；（d）0.02% GO，1000×，珊瑚砂试块；（e）0% GO，5000×，珊瑚砂试块；（f）0.02% GO，5000×，珊瑚砂试块
Figure 7. SEM image of the 28 d coral sand specimen with different GO mass fractions: (a) 0% GO, 1000×, river sand cement stones; (b) 0.03% GO, 1000×, river sand cement stones; (c) 0% GO, 1000×, coral sand cement stones; (d) 0.02% GO, 1000×, coral sand cement stones; (e) 0% GO, 5000×, coral sand cement stones; (f) 0.02% GO, 5000×, coral sand cement stones
图 8 不同GO质量分数的珊瑚砂试块和河砂试块SEM图 （a）0% GO珊瑚砂试块；（b）0% GO河砂试块；（c）0.02% GO珊瑚砂试块；（d）0.03% GO河砂试块
Figure 8. SEM images of the coral sand specimen and river sand specimen with different GO mass fractions: (a) 0% GO coral sand specimen; (b) 0% GO river sand specimen; (c) 0.02% GO coral sand specimen; (d) 0.03% GO river sand specimen
图 9 不同GO质量分数的珊瑚砂试块和河砂试块SEM图．（a）0% GO珊瑚砂试块；（b）0% GO河砂试块；（c）0.02% GO珊瑚砂试块；（d）0.03% GO河砂试块
Figure 9. SEM images of the coral sand specimen and river sand specimen with different GO mass fractions: (a) 0% GO coral sand specimen; (b) 0% GO river sand specimen; (c) 0.02% GO coral sand specimen; (d) 0.03% GO river sand specimen
图 10 试块平均孔隙面积与迁移系数的双对数关系曲线
Figure 10. Logarithmic relationship between the average area of the pore of the test block and migration coefficient
表 1 水泥的物理及力学性能指标
Table 1. Physical and mechanical properties of cement
Setting times/min Stability flexural strengths/MPa Compressive strengths /
MPaInitial Final 3-day 28-day 3-day 28-day 180 240 6.6 8.9 32.7 56.8 
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表 2 28 d结石体内部平均孔隙直径
Table 2. Pore diameter of the 28 d stone body
Specimen Diameter of pore /μm Specimen Diameter of pore /μm CS+28+0 14.41 RS+28+0 11.87 CS+28+1 13.02 RS+28+1 10.65 CS+28+2 12.32 RS+28+2 10.22 CS+28+3 13.33 RS+28+3 9.67 CS+28+4 13.83 RS+28+4 11.75
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