Leaching resistance of hazardous waste cement solidification after accelerated carbonation

Abstract

When cement-based materials are carbonated, some of their physicochemical properties are changed, which includes reductions of porosity by 20% and pH from 12-13 to 8-9. These changes can enhance the retention ability of cementitious solids containing hazard waste. This research studied the effect of carbonation on the leaching resistance of hazardous waste cement solidification. The finite element software COMSOL Multiphysics was used to simulate the process of accelerated carbonation and the effect of carbonation on leaching. Laboratory tests were conducted to validate the numerical models. Parametric studies from the numerical simulations revealed that carbonation could significantly improve leaching retention capabilities of cementitious solids containing hazardous wastes.

How carbonation curing influences ca leaching of Portland cement paste: Mechanism and mathematical modeling

“…Once the concentration of Ca in solution was stabilized, powder samples would be collected and X-Ray Fluorescence analysis (XRF) was conducted to determine this equilibrium concentration of Ca in solid phase using an x-ray fluorescence analyzer (AXIOS, PW4400). To determine the influence of carbonation curing and ca leaching on the microstructure and solubility of C-S-H, 29 Si Nuclear Magnetic Resonance (NMR) was also performed using a NMR spectrometer (BRUKER, DMX 500). To reduce the interference of Fe 2 O 3 in Portland cement, 29 Si NMR spectra were collected at 60 MHz and a spinning rate of 4 kHz.…”

“…To determine the influence of carbonation curing and ca leaching on the microstructure and solubility of C-S-H, 29 Si Nuclear Magnetic Resonance (NMR) was also performed using a NMR spectrometer (BRUKER, DMX 500). To reduce the interference of Fe 2 O 3 in Portland cement, 29 Si NMR spectra were collected at 60 MHz and a spinning rate of 4 kHz. 34 Samples were collected for 800 scans and each scan consisted of a single pulse with a width of 4.7 μs followed by a delay of 10s.…”

“…Ca carbonate (CaCO 3 ) generated during the carbonation process could refine the pore structure and leads to a nucleation effect, which accelerates the subsequent hydration. Previous investigations have shown that carbonation of mature concrete could improve the leaching resistance by reducing the porosity and permeability . However, there are significant differences between the passive carbonation of mature concrete and the carbonation curing of early age concrete in terms of reactants and products.…”

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

“…As shown in Figure 1, the depth of carbonation L was measured at four different locations along four edges, and the average value was used to determine the extent of carbonation according to GB/T 50082-2009 [36]:…”

The effect of random porosity field on supercritical carbonation of cement-based materials

“…In the recent years, however, the researchers in this area have paid more attention on studying the beneficial aspects of material carbonation, due to the rapid development of the accelerated and supercritical carbonation techniques. These researches include modification of composition and microstructure of cement based materials using carbonation [7][8][9] , use of CO 2 curing to improve material properties [10,11] , CO 2 capture and storage [12] and carbonation of hazardous water materials [13] . Clearly, further research on the carbonation process of cement and concrete is required in order to maximize the benefits and reduce the negative effects caused by carbonation.…”