摘要
为实现污染土和稻壳灰资源化利用,解决水泥固化材料高排放问题,采用稻壳灰-水泥为固化剂对重金属镉污染土进行固化处理。开展不同养护龄期、固化剂类型及镉含量下固化镉污染土无侧限抗压强度、毒性浸出、X射线衍射及扫描电镜试验,通过分析抗压强度、浸出质量浓度、破坏形态、微观形貌及矿物组成等宏微观特性,揭示稻壳灰-水泥固化镉污染土微观作用机制。结果表明:稻壳灰可以加速水泥水化过程,提高固化土无侧限抗压强度,低水泥掺量时加入5%~10%稻壳灰改善效果较优;固化土强度随镉含量增加而先升后降,存在临界值100~400 mg/kg;稻壳灰掺入后,土体脆性破坏特征减弱,镉污染下土体裂纹较多且破坏面不规则;固化土浸出质量浓度随龄期增加而降低,在镉含量为100 mg/kg时满足标准限值,稻壳灰部分替代水泥后浸出质量浓度相差不大;稻壳灰-水泥主要以水化硅铝酸钙聚合物凝胶(C-A-S-H)和钙矾石(AFt)共同支撑土体孔隙,不断团聚、胶结形成空间网状结构,形成骨架结构并吸附镉离子。
In order to realize resource utilization of contaminated soil and rice husk ash,and solve the problem of high emission of cement-solidified materials,the rice husk ash(RHA)-cement is used as the solidified agent to treat heavy metal cadmium(Cd)-contaminated soil.The unconfined compressive strength(UCS),toxicity leaching,XRD and SEM tests are carried out on the solidified Cd-contaminated soil with different curing ages,curing agent types and Cd contents.The UCS,leaching concentration,failure modes,micro-morphology and mineral composition are used to analyze the macro-micro characteristics.The micro-mechanism of the RHA-cement solidified Cd-contaminated soil is revealed.The results demonstrate that the RHA can accelerate the hydration process of cement and improve the UCS of solidified soil,while adding 5%~10%RHA at low cement content has better effect.The strength of solidified soil increases first and then decreases with the increase of Cd content,and there is a critical value of 100~400 mg/kg.When the RHA is added into the soil,the brittle failure characteristics of the soil are weakened.The soil cracks and irregular failure surfaces increase under Cd pollution.The leaching concentration of solidified soil decreases with the increase of age,and reaches the standard limit when the Cd content is 100 mg/kg.The leaching concentration of solidified soil after partial replacement by the RHA cement is similar.The RHA-cement mainly uses hydration calcium aluminosilicate polymer gel(C-A-S-H)and ettringite(AFt)to support soil pores,and continuously agglomerates and cements to form a spatial network structure,and finally to form the skeleton structure and to adsorb Cd2+.
作者
李丽华
岳雨薇
肖衡林
李文涛
韩琦培
曹毓
LI Lihua;YUE Yuwei;XIAO Henglin;LI Wentao;HAN Qipei;CAO Yu(School of Civil Engineering,Architecture and Environment,Hubei University of Technology,Hubei Ecological Road Research and Engineering Center,Wuhan 430068,China)
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2023年第2期252-261,共10页
Chinese Journal of Geotechnical Engineering
基金
武汉市应用基础前沿专项项目(2020020601012278)
国家自然科学基金项目(52278347)
湖北省重点研发项目(2022BCA059)
湖北工业大学杰出人才基金项目(XJ2021000501)。
关键词
稻壳灰
固化/稳定化
镉污染土
抗压强度
浸出质量浓度
微观机制
rice husk ash
solidification/stabilization
cadmium-contaminated soil
compressive strength
leaching concentration
microscopic mechanism