Hardening mechanism and pore size analysis of new magnetic epoxy cement grout
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摘要: 常规砂浆无法满足反倾斜裂隙和缺陷的工程填充要求，在注浆压力驱使下会引入大量气泡，浆液密实度得不到保障。针对此，研发了一种新型磁性环氧树脂水泥(MEC)浆液，可实现反重力式注浆锚固、导向式流动、增大浆体密实度、浆液黏度实时调控。采用SEM、XRD、N2吸附测试方法，对MEC浆液在不同磁场作用下的微观形貌、水化产物和孔径进行了分析。结果表明：MEC浆液主要分为环氧树脂固化、水泥水化两个硬化过程。固化产物对水化产物进行包裹，与钙矾石(Ettringite，AFt)和Ca(OH)2中的Ca2+发生离子作用，形成络合物包裹磁粉，对浆液中存在的微小孔隙进行填充；磁场强度由400 GS增大到6000 GS时，孔隙面积减小率达77.6%，孔隙数量减小率达76.8%。N2吸附试验表明：附加磁场会降低介孔和大孔的数量，显著减小比表面积，磁性浆液符合H4型滞回线，主要表现为墨水瓶孔；基于磁偶极子理论，数值模拟了磁颗粒受力，分析结果表明在磁场强度为2000~6000 GS可高效减小孔隙面积。
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关键词:
- 磁性环氧树脂水泥(MEC)浆液 /
- 微观结构 /
- XRD衍射分析 /
- 氮气吸附法 /
- 孔径分布
Abstract: Conventional mortar can not meet the engineering filling requirements of anti-inclined fractures and defects, and a large number of bubbles will be introduced under the pressure of grouting, and the density of slurry can not be guaranteed. In view of this, a new magnetic epoxy cement (MEC) slurry was developed, which can realize anti-gravity grouting anchoring, guided flow, increase of slurry density and real-time control of slurry viscosity. The SEM,XRD and N2 adsorption tests were used to analyze the microstructure, hydration products and pore size of MEC slurry under different magnetic fields. The results show that the MEC slurry can be divided into the following two hardening processes: Epoxy curing and cement hydration. The solidified product encapsulate the hydration product and ionize with Ca2+ in ettringite (AFt) and Ca(OH)2 to form a complex to fill the tiny pores in the slurry. When the magnetic field intensity increases from 400 GS to 6000 GS, the pore area and pore number decrease rate reach 77.6% and 76.8% respectively. The test of N2 adsorption shows that the number of mesopores and macropores and the specific surface area decrease significantly with the addition of magnetic field. The magnetic grout is in line with H4 hysteresis loop and mainly represents as ink bottle pores. Based on magnetic dipole theory, the force of magnetic particles is simulated numerically. The analysis results show that the pore area can be effectively reduced when the magnetic field intensity is from 2000 GS to 6000 GS. -
图 3 水泥砂浆与MEC水化产物对比
AFt—Ettringite; C-S-H—Calcium silicate hydrates
Figure 3. Hydration products comparison between cement mortar and MEC
图 4 不同环氧掺量的MEC浆液7天的XRD图谱
C3S—Tricalcium silicate; C2S—Dicalcium silicate
Figure 4. XRD patterns of MEC slurry with different epoxy contents at 7 d
图 5 不同龄期普通水泥浆液和MEC浆液XRD图谱
Figure 5. XRD patterns of ordinary cement grout and MEC slurry at different ages
图 7 不同磁力下MEC锚固段孔径分析
Figure 7. Analysis of aperture of anchor section of MEC under different magnetic forces
图 8 MEC锚固体内外圈层截面分区示意图
L1—Thickness of external circle; L2—Thickness of internal circle
Figure 8. Schematic diagram of section partition of inner and outer layers of MEC anchorage
图 9 MEC锚固体孔隙分布与孔隙数量分布直方图
Figure 9. Histogram of pore distribution and pore number distribution of MEC anchorage
图 10 MEC锚固体图像分区与孔径统计
D—Thickness
Figure 10. Image partition and aperture statistics of MEC anchorage
图 13 水泥浆液和MEC的N2吸附-脱附等温线
H—Magnetic field intensity; V—Adsorption volume
Figure 13. N2 adsorption-desorption isotherms of cement grout and MEC
图 16 水泥浆液和MEC微分孔径分布曲线
Figure 16. Differential aperture distribution curves of cement grout and MEC
图 17 MEC中磁颗粒的磁偶极子磁矩分布图
i, j—Magnetic particle
Figure 17. Distribution diagram of magnetic dipoles of magnetic particles in MEC
图 18 MEC中磁颗粒受力及孔隙率与磁场强度关系
Figure 18. Relationship between magnetic particle force and porosity and magnetic field intensity in MEC
表 1 磁性环氧树脂水泥(MEC)浆液配合比
Table 1. Design of magnetic epoxy cement (MEC) slurry
g Materials Cement Absolute water consumption Water-borne epoxy resin Curing agent Magnetic powder content Disperser Cement grout 400 160 0 0 0 0.0 MEC 400 110 100 85 100 1.5 
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表 2 MEC锚固体内外圈层孔隙统计
Table 2. Porosity statistics in the inner and outer circles of MEC anchorage
Layered
categoryTotal pore number Macrovoid (0.18-0.4 mm) Fine pore (Pore diameter d＜0.1 mm) Area/mm2 Number Area/mm2 Number External circle 218 0.326 6 0.4180 165 Internal circle 92 0.061 2 0.1918 65
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表 3 水泥浆液和MEC的孔结构参数
Table 3. Hole structure parameters of cement grout and MEC
Sample Specific surface area/(m2·g−1) Adsorption constant cBET Total volume/(m3(STP)·g−1) Cement grout 25.734 47.021 5.9124 MEC (H=0 GS) 8.205 95.022 1.8853 MEC (H=6000 GS) 6.368 34.645 1.4632 Note: STP—Standard temperature and pressure.
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