Rheological behavior, mechanical properties, fire resistance, and gamma ray attenuation capability for eco-friendly cementitious mixes incorporating thermally treated lead sludge

Abstract

The main objective of this study is to develop eco-friendly innovative binding materials based on lead sludge (sludge generated during glass polishing) for various advanced applications. The challenge with using lead sludge (LS) in cementitious blends is the presence of a considerable quantity of organic matter, which has a detrimental impact on the workability and mechanical characteristics of such blends. As a result, this study focused on comparing the influence of untreated and thermally-treated LS (ULS and TLS, respectively) on rheological behavior, mechanical characteristics, fire resistance, and harmful gamma-radiation shielding for various cementitious mixes. When compared to ULS, the results demonstrate that TLS has a greater pozzalnicity (as evaluated by modified Chapelle and Abo-El-Enein et al. methods), a bigger particle size (as established by particle size distribution and SEM analysis), and no organic matter content (as determined by FTIR technique). TLS incorporation in cement composite enhanced rheological parameters (lowest yield stress and plastic viscosity values) through eliminating organic matter that may adsorb a large amount of water. The specimen containing up to 20 % TLS achieved significant compressive strength value because it improved by 45.3 % when compared to ULS. This may be attributed to improved workability followed by a decrease in the water/solid ratio (as determined by the water consistency test), decomposition of organic matter that impedes the hydration process, and high pozzolanicity, which resulted in the creation of additional hydration products as confirmed by TGA/DTG and SEM/EDX analyses, as well as pore structure redistribution from macro to meso-pores validated by textural characteristics study (N2 adsorption/desorption isotherm) and total porosity measurement. The composite containing 10 wt% TLS had the best fire-resistant behavior up to 900 °C; it has a compressive strength that is 15.8 and 57.1 wt% greater than OPC and a specimen containing 10 % ULS, respectively. Although TLS-containing composites displayed excellent mechanical characteristics, ULS-containing composites exhibited exceptional radiation shielding properties because the organic matter, when exposed to gamma-rays, may be transformed into a cross-linked structure that reduces radiation intensity. The immobilization test was developed to guarantee the safety of produced composites. It was discovered that both ULS and TLS specimens had a Pb-concentration in leachate solution that was lesser than the toxicity limit (5 ppm). The immobilization process in TLS-containing specimens is more effective than in ULS; rather than narrow pores identified in TLS-containing specimens, the PbO2 was transformed to stable Pb3SiO5, as shown by XRD.