固化剂稳定磷石膏路基填料的工程特性研究

为提高磷石膏路基填料的强度和水稳定性，降低有害物质溶出，采用甲基硅酸钠、硅酸钠和乳化剂制备磷石膏固化剂（CA），并将质量比为0.5%、1.0%、1.5%和2.0%的CA加入到磷石膏中制备CA稳定磷石膏混合料（CASP），研究了CA掺量对CASP的力学性质（加州承载比CBR、回弹模量、无侧限抗压强度和剪切强度）、水稳定性（泡水软化系数和接触角）与有害物质溶出量的影响规律，并结合扫描电镜试验揭示了CASP的强度形成与水稳定性增强机理。结果表明：CA中的硅酸钠与磷石膏可生成硅酸钙凝胶与硫酸钠晶体，前者的胶凝作用和后者的填充作用提高了磷石膏的强度和密实度，CASP的CBR、回弹模量、无侧限抗压强度和剪切强度随着CA掺量的增加而大幅提升；由CA中的甲基硅酸钠所生成的聚硅氧烷憎水膜，改变了磷石膏颗粒表面的亲疏水性质，降低了磷石膏孔隙，改善了磷石膏的水稳定性，CASP的泡水软化系数随着CA掺量的增加而变大，掺2.0%CA的CASP与水分的接触角为91.4°；浸水11 d后掺1.0%CA的CASP可满足高速公路的路床填料CBR不小于8%和路基回弹模量不低于40 MPa的技术要求；通过硅酸钙凝胶的物理吸附和化学结合，以及憎水膜的填充固封，CA显著降低了磷石膏砷、铬、铅、氟离子和磷酸根的溶出量，掺0.5%CA的CASP浸出液中砷、铬和铅含量分别满足地下水Ⅰ级、Ⅱ级和Ⅳ级标准。

Research on Engineering Characteristics of Curing Agent Stabilized Phosphogypsum Roadbed Filler

In order to improve the strength and water stability of phosphogypsum subgrade filler and reduce the dissolution of hazardous substances. Phosphogypsum curing agent (CA) was prepared by using sodium methyl silicate, sodium silicate and emulsifier, and CA with mass ratios of 0.5%, 1.0%, 1.5% and 2.0% was added to phosphogypsum to prepare CA-stabilized phosphogypsum mixture (CASP). The effects of CA content on the mechanical properties (CBR, modulus of resilience, unconfined compressive strength and shear strength), water stability (softening coefficient and contact angle) and the amount of hazardous substances in the leaching solution of CASP were studied. The strength formation and water stability enhancement mechanism of CASP were revealed by scanning electron microscopy. Results show that sodium silicate and phosphogypsum in CA can generate calcium silicate gel and sodium sulfate crystal. The gelling effect of the former and the filling effect of the latter improve the strength and compactness of phosphogypsum, making CBR, resilient modulus, unconfined compressive strength and shear strength of CASP significantly increase with the increase of CA content; Polysiloxane hydrophobic film formed by sodium methyl silicate in CA changes the hydrophilic and hydrophobic properties of phosphogypsum particle surface, reduces the porosity of phosphogypsum and improves the water stability of phosphogypsum, so that the CASP's CBR and the water-weakening effect coefficient of resilient modulus increases with the increase of CA content, and the contact angle of CASP with 2.0% CA and moisture is 91.4°; CASP with 1.0% CA after soaking for 11 days can meet the technical requirements of highway roadbed filler CBR not less than 8% and subgrade resilient modulus not less than 40 MPa; Through the physical adsorption and chemical combination of calcium silicate gel, and the filling and sealing of hydrophobic membrane, CA significantly reduces the dissolution of arsenic, chromium, lead, fluoride and phosphate in phosphogypsum. The content of arsenic, chromium and lead in CASP leaching solution with 0.5% CA meet the grade Ⅰ, Ⅱ and Ⅳ groundwater standard, respectively.