利用油基岩屑制备水泥路面基层的力学性能及重金属浸出特性研究
Mechanical properties and heavy metal leaching characteristics of cement pavement base prepared from oil-based drilling cuttings
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摘要: 利用油基岩屑制备11种不同配合比的水泥路面基层试件,通过无侧限抗压试验、劈裂抗拉试验以及抗压回弹试验,探寻符合相关力学性能要求且岩屑掺加量最大的试件,随即对其开展浸出试验以研究重金属浸出规律,并通过浸出动力学模型拟合重金属长期浸出量。结果表明:(1)随着油基岩屑掺加量的提升,水泥路面基层试件的无侧限抗压强度、劈裂抗拉强度以及抗压回弹模量同时呈现下降趋势。当岩屑掺加量为12.0%时,试件相关力学指标满足要求,此时岩屑掺加量达到最大;(2)Ba、Mn、Pb、Zn为油基岩屑中的特征污染物。Ba、Mn、Pb的累积浸出量变化趋势较为一致,在64天时基本达到浸出平衡;而Zn的累积浸出量在第64天时仍持续增长。四种重金属在全浸出阶段的浸出行为都受到扩散控制影响;(3)Ba和Pb的浸出规律符合Elovich方程,而二阶动力学方程更适用于描述试件中Mn的浸出特性。浸出动力学模型拟合结果显示,长期使用利用油基岩屑制备的水泥路面基层,应更加关注Mn的浸出风险。Abstract: 11 kinds of cement pavement base specimens with different mixing ratios of oil-based drill cuttings (OBDC) were prepared, and unconfined compression strength, splitting tensile strength, and compressive modulus of resilience of the specimens were detected, in order to determine the specimen with the largest mixing ratio of OBDC and could meet the relevant mechanical properties. After that, the leaching test was carried out to study the leaching behavior of heavy metals, and different leaching models were used to predict the long-term cumulative leaching amount. The results reveal that: (1) unconfined compressive strength, splitting tensile strength and compressive modulus of resilience of the cement pavement base specimens decrease with the increment of OBDC content, with the mixing ratio of OBDC reaches to 12.0%, the relevant mechanical properties of the specimen could meet the requirements and, in this case, 12.0% of OBDC is the maximum mixing ratio. (2) Ba, Mn, Pb, and Zn are the characteristic heavy metal pollutants in OBDC. The cumulative leaching amount of Ba, Mn, and Pb reached to leaching equilibrium at 64 days, whereas the cumulative leaching of Zn continued to increase. Overall, the leaching behavior of these four heavy metals was affected by diffusion control. (3) Elovich equation could better describe the leaching behavior of Ba and Pb, while the second-order kinetic equation is more suitable to describe the leaching characteristics of Mn. The prediction of long-term heavy metal cumulative leaching amount indicated that more attention should be paid to Mn based on the leaching risk, when OBDC was used in preparing cement pavement base.
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