Use of cement-chelated, solidified, municipal solid waste incinerator (MSWI) fly ash for pavement material: mechanical and environmental evaluations

Abstract

As a by-product from the incineration of municipal solid waste (MSW), fly ash usually contains mobile heavy metals that may engender severe pollution when reused. In this study, fly ash was solidified with cement and a chelating agent to immobilize these polluting elements. The possibility of using the solidified fly ash for pavement materials was also assessed through mechanical and environmental perspectives. According to the results, the strength of solidified fly ash was found proportional to both the cement/fly ash ratio and curing time. This indicated that the increase of fly ash loading reduced the concentration of products from cement hydration, and thus destroyed the structure of the products of hydration. With the increase of freeze–thaw cycles, the compressive strength of cement-stabilized fly ash decreased between days 7 and 14, and then increased between days 14 and 28. Subsequently, the finite element analysis showed that placing the solidified fly ash layer as a pavement material between an unbound base course and subgrade was beneficial to prolong fatigue life and reduce rutting distress of asphalt pavements. Finally, leachability of metals from the mixtures was tested, which showed that leaching concentration decreased as the cement/ash ratio, curing time, and chelating agent content increased.

Strength and Deformation Properties of Fiber and Cement Reinforced Heavy Metal-Contaminated Synthetic Soils

“…Heavy metals in soil are highly toxic, persistent, and nonbiodegradable, which will impair the natural ecosystem services and eventually damage human health via the food chain [6][7][8][9][10]. Furthermore, heavy metals have adverse effects on the mechanical properties of soils, which results in unfavorable conditions for the redevelopment of contaminated sites [11]. Solidification/ stabilization (S/S) is an effective and economical method to heavy metal-contaminated soil treatment and has attracted increasing attention in the past decades [12,13].…”

“…S/ S technology according to different disposal locations can be divided into in situ and ex situ. Ordinary Portland cement, as a common binder utilized in S/S remediation, encapsulates heavy metal ions in a monolithic solid of high structural integrity to reduce further mobility of heavy metal ions [11,12]. Du et al evaluated the environmental characteristics of cement-solidified heavy metal-contaminated soil by using the finite element model.…”

Shear Behaviors of the Intersurface between Rice Straw Rope and Dredger Fill Silt: Experimental and Mechanism Studies

“…Table 3. ere is a certain interfacial cohesion at the interface of rice straw rope and dredger fill silt [36][37][38][39][40]. With the increase of immersion time, the interfacial cohesion decreases after 20 days' immersion and then increases, while the interfacial friction angle increases first and then decreases.…”

Evaluation of Carbonation Effects on Cement-Solidified Contaminated Soil Used in Road Subgrade

“…In China, according to Zhang et al, the concentration of Cu(II) in Guangdong was founded as high as 4800 mg/kg [9]. Heavy metals are not only hazardous to the environment and public health but also lead to the degradation of mechanical properties of soils [10,11]. Bochenek and Kurdowski found that the effect of solidification/stabilization of the waste is strongly related to the concentration of Pb(II) and Zn(II) [12].…”

“…is method not only enhances the strength of soil effectively but also reduces the leaching of heavy metals [11]. Numerous researchers have studied S/S process to immobilize heavy metal by means of various S/S agents such as cement, quicklime, hydrated lime, fly ash, and cement kiln dust [17,18].…”