聚丙烯酸钠改性钙基膨润土工程特性及微观结构研究

陈宏信; 牛松荧; 冯世进; 薛钦培; 李正霏; 石福江

doi:10.11779/CJGE20240103

聚丙烯酸钠改性钙基膨润土工程特性及微观结构研究 English Version

陈宏信^{1, 2,},
牛松荧¹,
冯世进^{1, 3, ,},
薛钦培¹,
李正霏¹,
石福江¹

1.
同济大学地下建筑与工程系, 上海 200092
2.
同济大学岩土及地下工程教育部重点实验室, 上海 200092
3.
土木工程防灾减灾全国重点实验室, 上海 200092

基金项目:

国家重点研发计划项目 2023YFC3707904

国家自然科学基金项目 42077250

国家自然科学基金项目 42277148

详细信息

作者简介:
陈宏信(1987—)，男，博士，教授，主要从事环境岩土方面的教学和研究工作。E-mail: chenhongxin@tongji.edu.cn

通讯作者:
冯世进, Email：fsjgly@tongji.edu.cn

中图分类号: TU411
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出版历程
- 收稿日期: 2024-01-31
- 网络出版日期: 2024-06-18
- 刊出日期: 2025-03-31

Engineering properties and microstructure of sodium polyacrylate-modified calcium bentonite

1.
Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
2.
Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Shanghai 200092, China
3.
State Key Laboratory of Disaster Reduction in Civil Engineering, Shanghai 200092, China

摘要

摘要: 中国钙基膨润土（CaB）资源丰富，近年来作为竖向隔离墙膨润土泥浆的替代材料备受关注。然而，由于天然钙基膨润土膨胀能力与化学相容性较差，对其工程特性的改进成为关键问题。为此，研究以聚丙烯酸钠（PAAS）为改性剂对钙基膨润土进行改良，确定了制浆—干燥—研磨法制备聚丙烯酸钠改性钙基膨润土（PAAS―CaB）的最佳制备条件。系统测试了改性膨润土的工程特性及微观结构，结果表明，改性剂掺量为8%时，PAAS―CaB膨胀指数可达34.0 mL/（2g），聚丙烯酸钠改性显著提高了钙基膨润土的吸水膨胀性能及化学相容性，为降低了膨润土泥饼的渗透系数。随PAAS掺量的增加，泥浆马氏黏度增大，滤失量和pH值减小，泥浆密度则主要由膨润土掺量控制。与未改性的CaB相比，PAAS―CaB在微观上表现出整体性更好的片层结构、更小的蒙脱石晶层间距。聚丙烯酸钠主要通过桥联包覆作用与接枝共聚合作用改善钙基膨润土性能。研究为优化PAAS―CaB制备工艺提供了可靠依据，为CaB的工程应用提供了可行的技术路径。
- 隔离墙 /
- 钙基膨润土 /
- 聚丙烯酸钠 /
- 工程特性 /
- 微观结构
Abstract: The abundant calcium-based bentonite (CaB) resources in China have gained attention as potential alternatives for preparing slurry when constructing cut-off walls. However, the limited swelling capacity and chemical compatibility of natural CaB pose critical challenges to enhancing its engineering properties. In this study, sodium polyacrylate (PAAS) is employed as a modifier to ameliorate CaB, and the optimal preparation conditions for sodium polyacrylate-modified calcium-based bentonite (PAAS―CaB) are determined through the processes of slaking, drying and grinding. The systematic tests on the engineering properties and microstructure of the modified bentonite were conducted. The results reveal that at a modifier content of 8%, the swelling index of PAAS―CaB reaches 34.0 mL/2g. The sodium polyacrylate modification significantly enhances the water absorption and swelling performance of CaB, along with improving its chemical compatibility, resulting in reduced permeability coefficient of the bentonite cake. With the increasing PAAS content, the Marsh viscosity of slurry increases, while the filtration loss and pH value decrease. The slurry density is primarily controlled by the bentonite content. Compared to the unmodified CaB, PAAS―CaB exhibits a superior overall lamellar structure at a microscopic scale, characterized by a smaller interlayer distance of montmorillonite crystalline layers. The sodium polyacrylate primarily modifies the calcium-based bentonite through bridging encapsulation and graft copolymerization. This study establishes a reliable foundation for optimizing the preparation process of PAAS―CaB and presents a feasible technical pathway for the engineering application of the calcium-based bentonite.
- cut-off wall /
- calcium-based bentonite /
- sodium polyacrylate /
- engineering property /
- microstructure

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图 1 固液比与膨胀指数关系

Figure 1. Relationship between solid liquid ratio and SI

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图 2 反应时间与膨胀指数关系

Figure 2. Relationship between reaction time and SI

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图 3 反应温度与膨胀指数关系

Figure 3. Relationship between reaction temperature and SI

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图 4 膨润土掺量与马氏黏度的关系

Figure 4. Relationship between bentonite content and marsh viscosity

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图 5 膨润土掺量与滤失量的关系

Figure 5. Relationship between bentonite content and filtration loss

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图 6 膨润土掺量与泥浆密度的关系

Figure 6. Relationship between bentonite content and slurry density

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图 7 膨润土掺量与泥浆pH值的关系

Figure 7. Relationship between bentonite content and slurry pH

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图 8 各掺量PAAS―CaB的扫描电镜

Figure 8. SEM images of (a) CaB, (b) PAAS―CaB with modifier content of 2%, (c) PAAS―CaB with modifier content of 4%, (d) PAAS―CaB with modifier content of 8%

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图 9 天然CaB及各掺量PAAS―CaB的XRD衍射图谱

Figure 9. XRD spectra of CaB and PAAS―CaB with modifier contents of 2%~8%

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表 1 膨润土的基本性质指标

Table 1 Properties of bentonites used in this study

性质指标	测试方法	CaB	NaB
相对质量密度	ASTM D854	2.34	2.75
液限/%	GB/T 50123	114.3	186.2
塑限/%	GB/T 50123	29.1	52.8
膨胀指数/ (mL·(2g)^-1)	ASTM D5890	9.0	23.5
pH	ASTM D4972	8.7	9.3
黏土分类	ASTM D2487	CH	CH

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表 2 PAAS―CaB最佳制备条件试验设计

Table 2 Test design for identifying optimal reaction conditions for PAAS―CaB preparation

改性样品	反应条件	第一阶段	第二阶段	第三阶段
2%PAAS―CaB	固液比S︰L	1︰8，1︰9，1︰10，1︰11，1︰12，1︰13	—	—
	反应时间t/min	90	30，60，90，120	—
	反应温度T/℃	50	50	20，35，50，65，80
4%PAAS―CaB	固液比S︰L	1︰11，1︰12，1︰13，1︰14，1︰15，1︰16	—	—
	反应时间t/min	90	30, 60, 90, 120	—
	反应温度T/℃	50	50	20，35，50，65，80
8%PAAS―CaB	固液比S︰L	1︰14，1︰15，1︰16，1︰17，1︰18，1︰19	—	—
	反应时间t/min	90	30，60，90，120	—
	反应温度T/℃	50	50	20，35，50，65，80

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表 3 NaB、CaB和2%~8%PASS―CaB的理化性质

Table 3 Physical and chemical properties of NaB, CaB and PAAS―CaB with modifier contents of 2%~8%

膨润土	膨胀指数SI/ (mL·(2g)^-1)		泥饼渗透系数k/(10^-10 m·s^-1)		化学相容性 ${k_\text{c}}/{k_\text{w}}$	液限 ${w_\text{L}}$ /%	塑限 ${w_\text{p}}$ /%
膨润土	DIW	CaCl₂	DIW	CaCl₂	化学相容性 ${k_\text{c}}/{k_\text{w}}$	液限 ${w_\text{L}}$ /%	塑限 ${w_\text{p}}$ /%
NaB	23.5	13.0	0.34	1.07	3.15	186.2	52.8
CaB	9.0	7.0	1.03	7.55	7.33	114.3	29.1
2%PAAS―CaB	17.0	11.0	0.43	3.43	7.98	143.7	35.6
4%PAAS―CaB	25.0	12.5	0.30	0.51	1.71	188.0	54.7
8%PAAS―CaB	34.0	16.3	0.11	0.13	1.15	221.5	68.5

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表 4 FTIR各吸收峰位置及化学键振动模式

Table 4 Chemical bond vibration patterns and FTIR peaks

振动模式	吸收峰位置/cm^-1
振动模式	CaB	2% PAAS― CaB	4% PAAS― CaB	8% PAAS― CaB
结晶水―OH伸缩振动	3621.6	3618.8	3620.0	3621.1
自由水―OH伸缩振动	3431.0	3446.6	3447.2	3447.4
―CH3不对称振动	—	—	2949.7	2949.7
自由水―OH弯曲振动	1636.5	1636.2	1635.7	1636.1
羧酸根(COO―)振动，C―H不对称伸缩振动	—	—	—	1569.8
羧酸根(COO―)振动，C=O对称伸缩振动	—	—	1419.3	1416.3
Si―O―Si反对称伸缩振动	1031.1	1032.0	1032.7	1032.2
Si―O―Si对称伸缩振动	796.1	795.8	795.9	795.7
Si―O―Al弯曲振动	519.0	519.2	519.1	518.9
Si―O―Si对称弯曲振动	465.3	466.8	466.9	466.7

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