Long term effects of lead contaminated water on the strength and microstructure of concrete

The discharge of lead-contaminated effluents from industrial activities such as smelting, refining, and petrochemical operations poses a critical environmental challenge by polluting surface and groundwater resources. Among mitigation strategies, the use of cement-based materials for the stabilization and solidification (S/S) of lead contaminants offers a promising approach, integrating environmental management with construction applications. This study systematically investigates the long-term effects of lead-contaminated mixing water on the mechanical performance, durability, and pollutant immobilization capacity of concrete, with particular focus on microstructural evolution. A total of 210 concrete specimens were prepared using mixing water containing lead concentrations of 0, 0.001, 0.002, 0.005, 0.01, 0.02, and 0.05 M. Compressive strength tests were conducted at curing ages ranging from 3 to 730 days, and pollutant retention was assessed using the toxicity characteristic leaching procedure. Microstructural analyses through X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy revealed that lead contamination disrupted cement hydration by forming Pb(OH)₂ and Pb-C-S-H phases, which inhibited the nucleation and growth of primary hydration products, notably calcium silicate hydrate (C-S-H) and portlandite (CH). At 0.05 M lead concentration, a compressive strength reduction of 61% was recorded after 365 days, with further deterioration to 14 MPa after 730 days. Despite the mechanical degradation, the stabilization process significantly reduced lead leaching, maintaining compliance with environmental standards for non-structural applications. These findings highlight the feasibility of employing lead-contaminated water in controlled construction uses, while emphasizing the critical need to account for long-term mechanical performance reductions when designing S/S-based waste management solutions.