| The research conducted in this paper aims to investigate the mechanism and properties of a low-pH magnesium phosphate cement(MPC) stabilized/solidified heavy metal contaminated soils under the acid rain environment with class42.5N portland cement(CEMI) for comparison, which were studied by laboratory tests combining theoretical analysis such as appearance observation, unconfined compressive test, chemical leaching test and microstructure observation.The main findings obtained from the tests are shown as follows:Based on comprehensive laboratory test, factors which controlling the erosion phenomenon in appearance,the strength behavior and the correlation of uniaxial strainstress of specimens under the acid rain environment are discussed,such as the initial pH value of acid rain, leaching time,the concentration of heavy metals and the type of binders.Furthermore; the engineering characteristics of the solidified heavy metal contaminated soils were investitated deeply by comparing two different leaching patterns between the long-term static circulation leaching and short-term semi-dynamic leaching.Through Batch leaching test, semi-dynamic leaching test and long-term static circulation leaching test simulates acid rain effect, the leaching characteristics of solidified zinc soil after erosion is investigaited by considering the influence of the initial pH value of acid rain, leaching time, the binder type and leaching pattern. The mechanism of Zinc ions releasing from specimens and the curing mechanism of Zinc ions are analyzed.The correlation between the concentration of Zinc and Leachate pH of Batch leaching test is discussed. The variety of effective diffusion coefficient calculated from the result of semi-dynamic leaching test is analyzed by considering different extraction frequency or leaching duration and the effect of initial pH value of leachant.Using electrical conductivity measuring to predict the leaching tendency of heavy metal ions in practice is discussed by studying the correlation of electrical conductivity and Zinc concentration in semi-dynamic leaching test and long-term static circulation leaching test.Then, the impact of leaching characteristics of Zinc ions is also studied by comparing different curing pattern for long-term static circulation leaching test.Transform of mineral phases and microstructure morphology of solidified heavy metal contaminated soils during erosion processes of acid rain were analyzed by X-ray diffraction(XRD) and scanning electron microscopy(SEM) techniques, respectively. The mechanism of stabilization and solidification of heavy metals and erosion mechanism of acid rain on solidified heavy metal contaminated soils are summarized by investigating the effect of initial pH of simulated acid rain, binder agent type, as well as the concentration of heavy metal ions on the mineral phase and microstructure of solidified soil. |
