Waterglass impregnation of municipal solid waste incineration bottom ash applied as sand replacement in mortars

Incineration has been recognized as one of the most applied strategies for the processing of the municipal solid waste (MSW). The primary output from the incineration of the MSW is Bottom Ash (BA), whose particles are highly porous and contaminated with heavy metals, chlorides, and sulphates, limiting its application in concrete. For improving the applicability as aggregates, many porous materials are impregnated with a pozzolanic solution, easing their use as building materials. However, this treatment has never been applied to by-products like BA, and therefore the influence of a coating on the leaching behaviour of the by-products has never been investigated. This study analyses the effect of an impregnation treatment based on different sodium silicate amounts on BA particles between 1 and 2 mm. The application of the coating lowers the pore volume of BA by 2.5 times, allowing a sand replacement up to 100% and improving the rheological behaviour of mortars till 38%, compared to uncoated samples. Replacing 50 vol.% of coated BA achieves 22% higher flexural and comparable compressive strength than the uncoated BA samples, thanks to the reduction of the Ca/Si ratio in the reaction products. Finally, in the presence of the coating, the leaching of the following contaminants Cl, Ba, Cu, Zn is reduced by 88, 98, 94 and 97%, respectively, compared to the uncoated BA application. Therefore, the impregnation treatment not only favours the application of higher amounts of BA, but it also improves the final performances of the product both mechanically and environmentally.

Internal evaluation of impregnation treatment of waterlogged wood; relation between concentration of internal materials and relaxation time using magnetic resonance imaging

The purpose of this study is to clarify the degree of impregnation resulting from treatment of internal waterlogged wood samples using MRI. On a 1.5T MR scanner, T₁ and T₂ measurements were performed using inversion recovery and spin-echo sequences, respectively. The samples were cut waterlogged pieces of wood treated with various impregnation techniques which were divided into different concentrations of trehalose (C₁₂H₂₂O₁₁) and polyethylene glycol (PEG; HO-(C₂H₄O)_n-H) solutions. Then these samples underwent impregnation treatment every two weeks. From the results, we found that the slope of the T₁-concentration curve using linear fitting showed the value of the internal area for PEG to be higher than the external area; internal, -2.73ms/wt% (R²=0.880); external, -1.50ms/wt% (R²=0.887). Furthermore, the slope of the T₁-concentration curve using linear fitting showed the values for trehalose to have almost no difference when comparing the internal and the external areas; internal, -2.79ms/wt% (R²=0.759); external, -3.02ms/wt% (R²=0.795). However, the slope of the T₂-concentration curve using linear fitting for PEG showed that there was only a slight change between the internal and the external areas; internal, 0.26ms/wt% (R²=0.642); external, 0.18ms/wt% (R²=0.920). The slope of the T₂-concentration curve did not show a change in linear relationship between the internal and the external areas; internal, 0.06ms/wt% (R²=0.175); external, -0.14ms/wt% (R²=0.043). In conclusion, using visualization of relaxation time T₁, it is possible to obtain more detail information noninvasively concerning the state of impregnation treatment of internal waterlogged wood.