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STUDY ON ROAD PERFORMANCE AND FREEZE-THAW RESISTANCE OF ALKALI ACTIVATED MATERIAL STABILIZED LOW-LIQUID-LIMIT SILTY CLAY
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摘要: 以伊犁地区S315线蜂场至尼勒克段低液限粉黏土为研究对象，以碱激发材料为固化剂，对粉质黏土和其固化土开展了路用性能指标试验与冻融循环试验，并利用电镜扫描试验(SEM)与X射线衍射试验(XRD)研究了固化土的微观特征，探讨了碱激发材料对粉质黏土路用性能指标与抗冻融特性的影响。试验结果表明，固化土的无侧限抗压强度与抗剪强度随碱激发材料掺量和养护龄期的增加而增大；固化土的CBR值与回弹模量随碱激发材料掺量的增加而显著增大，固化土路用性能指标满足规范要求。低液限粉黏土对冻融敏感，其冻胀、融沉率的大小与降温速率、含水率有关，相同温差下温度梯度越小土体受冻融影响越明显，相同温度梯度下含水率越高土体受冻融影响越明显。不同碱激发材料掺量下的固化土在补水条件下冻胀率均小于1%，不发生冻胀。微观特征分析结果表明，碱激发材料的主要水化产物是C(-A)-S-H凝胶，其生成量随龄期增加，其填充和胶结作用使土体形成致密的微观结构，从而提高土体的强度，同时增强其抗冻融稳定性。Abstract: The current study investigates the use of Alkali-Activated Material (AAM) to stabilize a silty clay with low liquid limit, collected from a construction site between Fengchang to Ni Leke section of line S315 in Yili Area. The experimental program includes road performance index tests and freeze-thaw cycling tests. They are performed on the silty clay and the stabilized soil to study the effect of AAM on the road performance index and freeze-thaw resistance. Micro characterization using scanning electron microscope(SEM) and X-Ray diffraction(XRD) is also carried out to study the underlying stabilizing mechanisms. The results show that the unconfined compressive strength and shear strength of solidified soil increase with the content of AAM and the curing age. The CBR value and resilient modulus of solidified soil increase with the content of AAM. The road performance indices of AAM stabilized soils satisfy the regulation requirements. The frozen heave and thawed settlement rates of silty clay are related to temperature gradient and water content. At the same temperature dropping range, the freeze-thaw effect is more evident on the silty clay at smaller temperature gradient. At the same temperature gradient, the freeze-thaw effect is more evident at higher water content. The frost heave rate of silty clay treated with different content of AAM under water supply condition is less than 1%, showing no frozen heave tendency. The results of micro characterization show that the C(-A)-S-H gel is the major cementing agents formed after AAM stabilization and its content increases with curing age. This cementing agent fills the pores between the soil particles and cements the soil particles together leading to a dense micro structure, which increases the strength and freeze-thaw resistance of stabilized soil.
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图 2 碱激发材料固化土与粉黏土击实曲线
Figure 2. Compaction curves of alkali-activated material treated soils(3%, 5% and 8%) and silty clay
图 3 固化土的CBR值与碱激发材料掺量的关系
Figure 3. Relationship between CBR value of solidified soil and content of alkali activated material
图 4 固化土的回弹模量与碱激发材料掺量的关系
Figure 4. Relationship between resilient modulus of solidified soil and content of alkali activated material
图 5 固化土的抗剪强度指标与碱激发材料掺量的关系
Figure 5. Relationship between shear strength index of solidified soil and content of alkali activated material
图 6 固化土的无侧限抗压强随着掺入比与养护龄期的变化
Figure 6. The variation of unconfined compressive strength of solidified soil with the mixing ratio and curing age
图 7 不同降温速率下粉黏土冻胀率随含水率的变化
Figure 7. Variation of frozen heave rate of silty clay with water content under different freezing rates
图 8 粉黏土的融沉率随含水率的变化
Figure 8. Variation of thawing settlement of silty clay with water content
图 9 冻融循环下粉黏土的冻胀、融沉特性
a. 粉黏土的冻胀和融沉量随冻融循环次数的变化; b. 粉黏土的冻胀和融沉率随冻融循环次数的变化
Figure 9. Freeze-thaw characteristics of silty clay
图 10 固化土的冻胀、融沉量随冻融循环次数的变化
a. 无补水; b有补水
Figure 10. Variation of frozen heave and thaw settlement of solidified soils
图 11 固化土冻胀、融沉率随冻融循环次数的变化
a. 无补水; b. 有补水
Figure 11. Changes of frozen heave and thawing settlement rate of solidified soil with freeze-thaw cycles
图 12 固化土与纯碱激发材料的XRD谱图
a. 不同掺量的固化土; b. 不同龄期的纯碱激发材料
Figure 12. XRD spectra of solidified soil and alkali activated materials
图 13 粉黏土与固化土SEM照片
a. 粉黏土; b. 掺量3%的固化土; c. 掺量5%的固化土; d. 掺量8%的固化土
Figure 13. SEM images of silty clay and solidified soil
图 14 素土与养护龄期为28d的固化土的表观孔隙率对比
Figure 14. Comparison of apparent porosity between silty clay and solidified soil with curing age of 28 days
表 1 粉黏土的基本物理指标
Table 1. Basic physical indexes of silty clay
最大干密度ρd /g·cm-3 最优含水率ω /% ωL/% ωP/% IP/% 1.91 11.20 32.7 21.5 11.2 
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表 2 原料化学成分
Table 2. Chemical composition of raw materials
化学组分 SiO2/% Fe2O3/% Al2O3/% CaO/% MgO/% K2O/% SO3/% Na2O/% 烧失量/% 粉煤灰 52.34 9.62 24.48 5.0 1.91 2.27 0.46 0.78 3.14 钢渣 31.20 35.40 9.00 8.4 2.40 2.30 3.10 2.74 5.46 水泥 19.40 3.32 6.84 60.6 2.68 0.95 5.26 0.20 0.75
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表 3 路用性能试验方案
Table 3. Road performance test plan
试验项目 掺入比/% 养护龄期/d 承载比 0，3，5，8 7 回弹模量 0，3，5，8 7 无侧限抗压强度 0，3，5，8 7，28 直剪 0，3，5，8 7
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表 4 冻胀融沉试验方案
Table 4. Plan for evaluating frost heaving and thawing settlement
试验项目 掺入比/% 温度梯度/℃·h-1 初始含水率/% 冻胀 0 -6，-4，-2 20，24，28 融沉 0 -2 20，24，28 冻融循环 0，3，5，8 -2 最佳含水率(补水)
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表 5 微观特征分析试验方案
Table 5. Test plan for micro characterization
试验项目 研究对象 养护龄期/d XRD 碱激发材料，固化土 7，28 SEM 粉黏土，固化土 28
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表 6 素土与碱激发材料固化土液、塑限
Table 6. Liquid and plastic limits of untreated soil and alkali-activated material treated soils(3%, 5% and 8%)
碱激发材料掺量/% ωL/% ωP/% IP/% 0(素土) 32.7 21.5 11.7 3 33.1 23.0 10.1 5 35.9 25.4 10.5 8 36.3 26.2 10.1
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