| 偏高岭土协同石灰钝化红黏土水敏性的机制 |
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| 引用本文： | 谈云志,胡焱,曹玲,邓永锋,明华军,沈克军.偏高岭土协同石灰钝化红黏土水敏性的机制[J].岩土力学,2020,41(7):2207-2214. |
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| 作者姓名： | 谈云志 胡焱 曹玲 邓永锋 明华军 沈克军 |
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| 作者单位： | 1. 三峡大学 特殊土资源化利用宜昌市重点实验室，湖北 宜昌 443002；2. 东南大学 岩土工程研究所，江苏 南京 211189；
3. 宜昌鸿乾环保建材有限公司，湖北 宜昌 443100 |
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| 基金项目： | 国家自然科学基金（No. 51579137）；水电工程施工与管理湖北省重点实验室（三峡大学）开放基金（No. 2016KSD18）；湖北省优秀中青年科技创新团队计划项目（No. T201803）；三峡大学学位论文培优基金项目（No. 2019SSPY030）。 |
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| 摘 要： | 红黏土水敏性强，添加石灰等碱性材料处治后，能获得即刻的改良效果，但由于红黏土呈弱酸性，石灰改良后其长期性能会衰减。为提高石灰稳定红黏土（简称La+L）的长期性能，添加偏高岭土（4%）协同石灰（5%）稳定红黏土（简称La+L+MK），改善其水敏性和酸?碱互损作用。制备8种初始含水率的压实试样（初始孔隙比相同），养护到预定时间后开展无侧限抗压强度试验，同时，测定试样的钙离子浓度、电导率和pH值。结果表明：初始含水率为26%左右时，改良土的无侧限抗压强度最高，初始含水率偏高或偏低都不利于改良土的强度增长。究其原因，试样偏干时，缺少水分，石灰水化不充分，不能形成游离态钙离子，无法进行火山灰反应，颗粒之间无法形成胶结；试样偏湿时，火山灰反应形成的胶结强度不及过量水分引起的基质吸力丧失量。试样的钙离子浓度和电导率变化规律，证实了以上原因解释的猜想。当然，添加偏高岭土后，能够显著改善偏湿状态下的石灰土强度。即使浸水饱和后，相对石灰改良土，也能够保持较高的强度，充分证明偏高岭土能够有效降低石灰土水敏性，提高其耐久性。偏高岭土直接提供了大量硅、铝氧化物，且将土体pH值降到有利于硅、铝氧化物溶解的碱性范围，加速火山灰反应，缓减或抑制石灰?红黏土的互损作用。
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| 关 键 词： | 偏高岭土 石灰稳定红黏土 酸?碱互损作用 水敏性 钙离子浓度 |
| 收稿时间： | 2019-07-29 |
| 修稿时间： | 2019-12-30 |
Mechanism of metakaolin and lime modification of water sensitivity for
compacted laterite |
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| TAN Yun-zhi,HU Yan,CAO Ling,DENG Yong-feng,MING Hua-jun,SHEN Ke-jun.Mechanism of metakaolin and lime modification of water sensitivity for
compacted laterite[J].Rock and Soil Mechanics,2020,41(7):2207-2214. |
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| Authors: | TAN Yun-zhi HU Yan CAO Ling DENG Yong-feng MING Hua-jun SHEN Ke-jun |
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| Institution: | 1. Yichang Key Laboratory of the Resources Utilization for Problematic Soils, China Three Gorges University, Yichang, Hubei 443002, China;
2. Institute of Geotechnical Engineering, Southeast University, Nanjing, Jiangsu 211189, China;
3. Yichang Hongqian Environmental Building Material Co., Ltd., Yichang, Hubei 443100, China |
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| Abstract: | Laterite is very sensitive to water. This drawback can be substantially mitigated by adding alkaline materials like lime, but adding alkaline materials can impair the long-term performance of laterite due to the weak acidity of laterite. In this study, a certain amount of lime (5%) and metakaolin (4%) (La+L+MK) was added into the laterite to improve its water sensitivity and mitigate the deteriorative acid-base reaction. The mixtures with eight different initial water contents were compacted and cured at predetermined periods. After the curing, unconfined compressive strength (UCS), calcium ion concentration, electro conductibility and pH were tested. The results show that the UCS of the stabilized soil approached its peak at the water content of 26%, so it was not conducive to the strength development of the stabilized soil when the water content diverged from the optimal value. The reason is that when lime is not well hydrated due to lack of water, calcium ion cannot be released, thereby inhibiting the pozzolanic reaction. As a result, cementitious hydrates in the inter-aggregates of laterite cannot be generated. Also, the bonding strength increase due to the pozzolanic reaction is lower than the matrix suction loss caused by excessive moisture when the sample is too wet. The measurements of calcium ion concentration and electro conductivity confirmed the above conjectures. Our results clearly show that metakaolin combined with lime significantly improve the laterite strength at the wet state. Even after being saturated, the relative stability of the lime-stabilized soil can still be maintained with metakaolin additives, which indicates that metakaolin can effectively reduce the water sensitivity of lime soil and improve its durability. This phenomenon is due to the fact that metakaolin contains amorphous silicon and aluminum oxides and has edge-surface-contacted structures at the microscopic scale, thereby enabling it to significantly reduce the soil pH to the alkaline range that favors dissolution of silica and alumina oxides, thus accelerating the pozzolanic reaction and slowing down or inhibiting the deterioration reaction. |
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| Keywords: | metakaolin lime stabilized laterite deterioration interaction water sensitivity calcium ion concentration |
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