Freeze-Thaw Resistance of Red Mud-Based Stabilized Crushed Stone
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摘要:
为实现赤泥基胶凝材料在道路工程中的安全应用,研究赤泥基稳定碎石基层在冻融循环作用下力学性能与质量的变化规律,并采用工业CT扫描、SEM-EDS等方式探究冻融温度与次数对力学性能和质量损失的作用机制. 研究表明:20~−20 ℃、28 d条件下胶凝材料5%掺量最大质量损失率为1.85%;5%和6%赤泥基胶凝材料掺量下稳定碎石质量损失率变化幅度高于掺量7%和8%掺量下的变化幅度,且随着冻融循环次数的增加,质量损失率不断增加;通过工业CT与SEM-EDS微观分析,随着冻融循环次数增加,稳定碎石孔隙率增大,养生28 d、6%掺量稳定碎石经历20次冻融循环后,孔隙率增长1.53%,内部裂缝损伤增多并不断积累,呈现由少变多、由窄变宽的变化规律;研究结果对交通工程绿色建设和赤泥大宗量利用具有积极推动作用.
Abstract:In order to achieve the safe application of red mud-based cementitious materials in road engineering, the mechanical properties and quality of red mud-based stabilized crushed stone base under freeze-thaw cycles were studied. The influence of freeze-thaw cycle temperature and number on mechanical properties and quality loss was explored by industrial CT scanning and SEM-EDS. Research has shown that when the temperature ranges from 20 ℃ to −20 ℃ for 28 days, the maximum quality loss rate of the cementitious material with a 5% dosage is 1.85%. The change in quality loss rate of stabilized crushed stone with 5% and 6% red mud-based cementitious materials is higher than that with 7% and 8% red mud-based cementitious materials. In addition, with the increase in freeze-thaw cycles, the quality loss rate continues to increase. Through industrial CT and SEM-EDS microscopic analysis, as the number of freeze-thaw cycles increases, the porosity of stabilized crushed stone increases. After the stabilized crushed stone undergoes 28 days of curing and 20 freeze-thaw cycles with a 6% dosage, the porosity increases by 1.53%, and internal crack damage increases and accumulates continuously, showing a changing pattern from less to more and from narrow to wide. The research results have a positive role in promoting the green construction of transportation engineering and the large-scale application of red mud.
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表 1 原料化学组成
Table 1. Chemical composition of raw materials
% 类型 Fe2O3 Al2O3 SiO2 TiO2 Na2O CaO SO3 ZrO2 P2O5 MgO Cr2O3 MnO K2O 赤泥 53.63 19.48 8.30 7.26 4.86 4.65 0.42 0.42 0.24 0.23 0.19 0.11 0.08 矿粉 2.36 16.71 25.51 0.99 0.50 45.09 1.25 0.11 0.04 5.67 0.46 1.04 表 2 赤泥基胶凝材料主要技术指标
Table 2. Technical specifications of red mud-based cementitious materials
试验项目 标准稠度用水量/% 凝结时间/min 28 d抗折强度/MPa 28 d抗压强度/MPa 检测结果 27.36 初凝226,终凝366 9.64 24.50 表 3 碎石骨料物理性质
Table 3. Physical properties of crushed stone aggregate
试验项目 压碎值/% 针片状含量/% 小于0.075 mm颗粒含量/% 表观相对密度 毛体积相对密度 吸水率/% 碎石A 5.8 0.1 2.738 2.714 0.33 碎石B 21.8 7.7 0.8 2.721 2.700 0.4 碎石C 9.9 0.6 2.712 2.693 0.62 石粉 14.9 2.703 表 4 骨料各筛孔通过百分率
Table 4. Percentage of passing each sieve opening of aggregate
% 类别 粒径/mm 31.50 26.50 19.00 9.50 4.75 2.36 0.60 0.08 碎石A 100.0 87.4 3.4 0.1 0.1 0.1 0.1 0.1 碎石B 100.0 100.0 84.0 7.1 0.8 0.8 0.8 0.8 碎石C 100.0 100.0 100.0 98.9 15.6 1.2 0.6 0.6 石粉 100.0 100.0 100.0 100.0 98.8 72.2 34.6 14.9 表 5 最大干密度、最佳含水率和7 d无侧限抗压强度
Table 5. Maximum dry density, optimal water content, and 7 d unconfined compressive strength
级配名称 最佳含水率/% 最大干密度/
(g•cm−3)7 d无侧限抗压强度/MPa 合成级配1 4.4 2.316 5.32 合成级配2 4.8 2.400 6.19 合成级配3 4.6 2.356 6.09 合成级配4 4.8 2.373 5.76 表 6 不同冻融循环条件下的元素及含量比例
Table 6. Element content and content ratio under different freeze-thaw cycle conditions
% 冻融条 件 点位 Ca Si Na Al Ca/Al Ca/Si Si/Al Na/Si Na/Al 20~−20 ℃,冻融5次 1 27.21 2.22 0.8 1.21 22.5 12.26 1.83 0.36 0.66 2 42.91 1.96 0.4 1.21 35.5 21.89 1.62 0.2 0.33 3 40.69 0.87 0.18 0.43 94.6 46.77 2.02 0.21 0.42 4 37.48 2.77 0.67 1.66 22.6 13.53 1.67 0.24 0.40 5 45.95 0.90 0.23 0.31 148 51.06 2.90 0.26 0.74 20~−20 ℃,冻融20次 1 18.47 9.48 2.63 4.45 4.15 1.94 2.13 0.28 0.59 2 27.72 12.31 1.03 10.33 2.68 2.25 1.19 0.08 0.10 3 10.47 9.25 4.48 10.29 1.02 1.13 0.90 0.48 0.44 4 24.12 12.97 1.01 9.77 2.47 1.86 1.33 0.08 0.10 5 41.97 17.74 0.2 0.84 50.00 2.36 21.1 0.01 0.24 40~−20 ℃,冻融5次 1 14.33 14.95 0.86 7.23 1.98 0.95 2.07 0.06 0.12 2 22.49 5.78 2.3 4.03 5.58 3.89 1.43 0.40 0.57 3 23.61 4.56 1.45 2.32 10.2 5.17 1.97 0.32 0.63 4 25.08 5.44 1.45 2.62 9.57 4.61 2.08 0.27 0.55 5 15.65 12.69 3.66 7.86 1.99 1.23 1.61 0.29 0.47 40~−20 ℃,冻融20次 1 0.19 2.40 2.20 0.65 0.29 0.08 3.69 0.92 3.38 2 0.10 1.95 1.34 0.42 0.24 0.05 4.64 0.69 3.19 3 0.37 7.32 2.28 4.11 0.09 0.05 1.78 0.31 0.55 4 0.21 8.73 5.68 0.34 0.62 0.02 25.70 0.65 16.7 5 0.59 4.80 2.27 0.84 0.70 0.12 5.71 0.47 2.70 -
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