纳米SiO<sub>2</sub>改性滨海水泥土的短龄期力学性能与微观机制

王伟; 刘静静; 李娜; 马露

doi:10.13801/j.cnki.fhclxb.20210702.001

纳米SiO₂改性滨海水泥土的短龄期力学性能与微观机制

doi: 10.13801/j.cnki.fhclxb.20210702.001

王伟^{1, 2,},
刘静静^{1, 2,},
李娜^{1, 2,},
马露^3, ,

1.
绍兴文理学院　土木工程学院，绍兴 312000
2.
浙江省岩石力学与地质灾害重点实验室，绍兴 312000
3.
河海大学　岩土工程研究所，南京 210009

基金项目: 国家自然科学基金(41772311)

详细信息

通讯作者:
马露，博士研究生，讲师，研究方向为软土地基处理　E-mail：mal@ahstu.edu.cn

中图分类号: TU43；TB383.1
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- 被引次数: 0
出版历程
- 收稿日期: 2021-04-19
- 修回日期: 2021-06-11
- 录用日期: 2021-06-24
- 网络出版日期: 2021-07-02
- 刊出日期: 2022-04-01

Mechanical properties and micro mechanism of nano-SiO₂ modified coastal cement soil at short age

WANG Wei^{1, 2
,},
LIU Jingjing^{1, 2
,},
LI Na^{1, 2
,},
MA Lu^{3
, ,}

1.
School of Civil Engineering, Shaoxing University, Shaoxing 312000, China
2.
Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province, Shaoxing 312000, China
3.
Geotechnical Engineering Research Institute, Hohai University, Nanjing 210009, China

摘要

摘要: 为了研究纳米SiO₂对滨海水泥土短龄期的力学改性效果，开展了纳米SiO₂掺量(与水泥质量比)分别为0%、1.5%、3.0%、4.5%和6.0%的水泥土无侧限抗压试验、劈裂抗拉试验、pH试验、SEM试验。力学试验表明，纳米SiO₂能够提高水泥土的无侧限抗压强度、劈裂抗拉强度和弹性模量，但加剧了水泥土的脆性；纳米SiO₂改性水泥土的抗压强度大约为抗拉强度的10倍；pH测试表明，纳米SiO₂能够改善水泥土的碱性环境。SEM微观测试发现，水泥土颗粒形态、孔隙特征变化规律与强度发展规律关系紧密，随着纳米SiO₂掺量的增加，土颗粒形态分布由松散变为聚集，并伴随孔隙的减少。综上发现，纳米SiO₂掺量为4.5%时，强度改善效果最佳，微观孔隙最少，4.5%为最优掺量。最后，建立了纳米SiO₂改性水泥土力学强度与微观孔隙率之间的二次多项式模型。
- 水泥土 /
- 纳米SiO₂ /
- 力学特性 /
- 微观结构 /
- 二次函数模型
Abstract: In order to study the mechanical modification effect of nano-SiO₂ on coastal cement soil at short age, unconfined compression test, splitting tensile test, pH test and SEM test of cement soil with nano-SiO₂ content (mass ratio to cement) of 0%, 1.5%, 3.0%, 4.5% and 6.0% were carried out. Mechanical tests show that nano-SiO₂ can improve the unconfined compressive strength, splitting tensile strength and elastic modulus of cement soil, but aggravate its brittleness; the compressive strength of nano-SiO₂ modified soil is about 10 times of its tensile strength. The pH test shows that nano-SiO₂ can improve the alkaline environment of cement soil. SEM micro test shows that the change law of cement soil particle morphology and pore characteristics is closely related to the strength development law. With the increase of nano-SiO₂ content, the distribution of soil particle morphology changes from loose to aggregate, and the pores decrease. In conclusion, when the nano-SiO₂ content is 4.5%, the strength improvement effect is the best, the micro pores are the least, and 4.5% is the best content. Finally, the quadratic polynomial model between mechanical strength and micro porosity of nano-SiO₂ modified cement soil is established.
- cement soil /
- nano-SiO₂ /
- mechanical properties /
- microstructure /
- quadratic function model

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图 1 滨海软土的SEM图像 (a) 和EDX图谱 (b)

Figure 1. SEM image (a) and EDX spectrum (b) of coastal soft soil

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图 2 M32.5硅酸盐水泥SEM图像 (a) 和EDX图谱 (b)

Figure 2. SEM image (a) and EDX spectrum (b) of M32.5 silicate cement

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图 3 纳米SiO₂的SEM图像 (a) 和EDX图谱 (b)

Figure 3. SEM image (a) and EDX spectrum (b) of nano-SiO₂

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图 4 无侧限抗压试验获得的不同纳米SiO₂掺量水泥土抗压强度应力-应变曲线

Figure 4. Stress-strain curves of compressive strength of cement soils with different nano-SiO₂ contents obtained from unconfined compression test

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图 5 无侧限抗压试验获得的不同纳米SiO₂掺量水泥土抗压强度与残余强度变化

Figure 5. Variation of compressive strength and residual strength of cement soils with different nano-SiO₂ contents obtained from unconfined compression test

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图 6 不同纳米SiO₂掺量水泥土无侧限抗压试验试样破坏图

Figure 6. Failure diagrams of unconfined compression test samples of cement soils with different nano-SiO₂ contents

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图 7 不同纳米SiO₂掺量水泥土弹性模量变化

Figure 7. Variation of elastic modulus of cement soil with different nano-SiO₂ contents

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图 8 劈裂试验获得的不同纳米SiO₂掺量水泥土抗拉强度曲线

Figure 8. Tensile strength curves of cement soils with different nano-SiO₂ contents obtained from splitting test

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图 9 无侧限试验与pH试验获得的不同纳米SiO₂掺量水泥土无侧限抗压强度与pH关系

Figure 9. Relationship between unconfined compressive strength and pH of cement soils with different nano-SiO₂ contents obtained from unconfined test and pH test

S—Soil

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图 10 2 000放大倍数下nano-SiO₂/CS试样SEM图像

Figure 10. SEM images of nano-SiO₂/CS at 2 000 magnification

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图 11 取自图10a₁、b₂、c₃、d₄点的nano-SiO₂/CS 5000放大倍数下SEM图像

Figure 11. SEM images of a₁，b₂，c₃ and d₄ at 5000 magnification from Figure 10

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图 12 不同倍数下纳米SiO₂/CS孔隙率灰白二值图

Figure 12. Gray binary diagrams of nano-SiO₂/CS porosity at different times

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图 13 不同放大倍数下纳米SiO₂/CS孔隙率变化

Figure 13. Porosity variation of nano-SiO₂/CS at different magnifications

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图 14 无侧限抗压试验获得的不同纳米SiO₂掺量水泥土抗压强度与孔隙率的拟合曲线

Figure 14. Curve of unconfined compressive strength and porosity of cement soils with different nano-SiO₂ contents obtained by unconfined compression test

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表 1 滨海软土的物理性质指标

Table 1. Physical property index of coastal soft soil

Density/(g·cm⁻³)	Pore ratio	Water content/%	Liquid limit/%	Plastic limit/%	Liquidity index	Plastic index
1.65	1.64	30.0	46.2	26.4	0.18	19.8

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表 2 M32.5硅酸盐水泥基本物理性能指标

Table 2. Basic physical properties of M32.5 silicate cement

Fineness/%	Initial setting time/min	Final setting time/min	Ignition loss/%	Compressive strength/MPa		Flexural strength/MPa
Fineness/%	Initial setting time/min	Final setting time/min	Ignition loss/%	3 days	28 days	3 days	28 days
3.4	210	295	1.4	26.9	48.1	4.9	9.0

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表 3 纳米SiO₂基本物理性能指标

Table 3. Basic physical properties of nano-SiO₂

Color	Average particle size/nm	Bulk density/(g·L⁻¹)	Specific surface area /(m²·g⁻¹)	pH	Water content/%	Burn/%	SiO₂/%
White	20	50	25-200	3.7-4.7	≤1.5	≤1.0	≥99.8

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表 4 不同纳米SiO₂掺量水泥土试样成分组成和测试龄期

Table 4. Composition and testing age of cement soil (CS) samples with different nano-SiO₂ contents

Sample code	Water content/%	Cement content/%	Nano-SiO₂ content/%	Curing time/days
0%nano-SiO₂/CS	30	7	0	7
1.5%nano-SiO₂/CS	30	7	1.5	7
3.0%nano-SiO₂/CS	30	7	3.0	7
4.5%nano-SiO₂/CS	30	7	4.5	7
6.0%nano-SiO₂/CS	30	7	6.0	7
Notes: Water content—Mass ratio to mixture; Cement content—Mass ratio to soil; Nano-SiO₂ content—Mass ratio to cement.

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表 5 不同纳米SiO₂掺量水泥土的抗压强度平均值与变异系数C_V

Table 5. Average values and coefficients of variation C_V of compressive strength of cement soils with different nano-SiO₂ content

Sample code	Average compressive strength/kPa	C_V
0%nano-SiO₂/CS	1021	0.04
1.5%nano-SiO₂/CS	1149	0.02
3.0%nano-SiO₂/CS	1307	0.03
4.5%nano-SiO₂/CS	1683	0.03
6.0%nano-SiO₂/CS	1524	0.03

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表 6 不同放大倍数下纳米SiO₂/CS孔隙率n与强度的关系

Table 6. Relationship between porosity n and strength of nano-SiO₂/CS at different magnifications

Sample code	Compressive strength/kPa	Tensile strength/kPa	Porosity n/%
Sample code	Compressive strength/kPa	Tensile strength/kPa	×500	×2 000	×5000
0%nano-SiO₂/CS	1 021	110	9.7	10.8	7.2
1.5%nano-SiO₂/CS	1 149	121	8.4	8.4	5.3
3.0%nano-SiO₂/CS	1 307	133	6.2	6.4	4.5
4.5%nano-SiO₂/CS	1 683	167	4.6	5.6	3.8
6.0%nano-SiO₂/CS	1 524	155	5.6	5.8	4.3

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