活化牡蛎壳固化余泥渣土及其机理分析

为实现牡蛎壳和余泥渣土两种固废资源的利用,提出了预处理的牡蛎壳经磷酸或磷酸氢二铵(DAP)活化后固化土体,制得牡蛎壳固化土。试验测定了不同配比的牡蛎壳固化土的力学性能,研究牡蛎壳固化土的边坡抗冲刷性能,并使用扫描电镜和X射线衍射仪观察固化土的微观结构,分析其固化机理。结果表明,掺磷酸、DAP能提高牡蛎壳固化土的抗压强度,其中掺加DAP的效果更好。材料最佳配比(质量分数)为:73.6%土,18.4%牡蛎壳(粒径≤1 mm),8%DAP。其烘干抗压强度达到2.14 MPa,是牡蛎壳稳定余泥渣土抗压强度的2.43 倍,软化系数达到0.5,改变了原土遇水崩解的特性。在室内边坡冲刷试验中,掺DAP牡蛎壳固化土与素土相比,有效降低了坡面冲刷的产沙量。微观结构分析表明,磷酸、DAP分别与牡蛎壳作用生成磷酸钙晶体、羟基磷灰石,两者都能胶结土粒,从而固化土体。

Activated Oyster Shell for Solidification of Residual Soil and Its Mechanism Analysis

In order to realize the utilization of the two solid waste resources of oyster shell and residual soil, it was proposed that the pretreated oyster shell was activated by phosphoric acid or diammonium hydrogen phosphate (DAP) to obtain the oyster shell solidified soil. The mechanical properties of oyster shell solidified soil with different ratios were measured and the scouring resistance of slope was studied. The scanning electron microscope and X-ray diffraction were used to observe the microstructure of solidified soil and analyze its solidification mechanism. The results show that the addition of phosphoric acid or DAP improves the compressive strength of oyster shell solidified soil, and the effect of adding DAP is better. The best ratio (mass fraction) of materials is: 73.6% soil, 18.4% oyster shell (particle size ≤1 mm), 8% DAP. Under the optimum ratio condition, the drying compressive strength reaches 2.14 MPa, which is 2.43 times of the compressive strength of oyster shell stabilized residual soil, and the softening coefficient reaches 0.5, which changes the disintegration characteristics of the original soil when exposes to water.In indoor slope scour test, the oyster shell solidified soil mixed with DAP effectively reduces the amount of sand produced by the erosion of slope compared with the plain soil. Microstructure analysis shows that phosphoric acid or DAP interacts with oyster shell to form calcium phosphate crystals and hydroxyapatite. The new products can cement soil particles and solidify the soil.