Recycling CMP sludge as a resource in concrete

Sludge, a byproduct of chemical mechanical polishing (CMP) used in integrated-circuit (IC) industries, is composed of hazardous materials such as nano-particles of SiO2, Al2O3, CaF2, and unknown organics. These nano-particles are potentially dangerous if released into the environment. Preliminary studies are carried out on sludge-blended cement concrete (SBCC) formed into specimens of cylindrical concrete with 10 cm diameter and 20 cm height. They are with 10 wt.% cement replaced by CMP sludge powder. Three water/cementitious (W/C) ratios were selected to mold the specimens for setting time, XRD analysis, TCLP analysis and compressive strength and stress–strain tests, respectively. TCLP test results revealed that the concentrations of leached heavy metals were substantially below the regulatory thresholds. The strengths of the SBCC specimens were comparable to those of the ordinary Portland cement concrete (OPCC) specimens with 3-day curing and about 22–38% much higher than those of OPCC cylindrical concrete specimens at 7–91 days of age. These results demonstrate the feasibility of recycling CMP sludge into construction materials, a positive step for sustainable development.

► Sludge of the chemical mechanical polishing is recycled as the concrete compound.
► Sludge-blended cement concrete (SBCC) is stronger than ordinary concrete in compression.
► SBCC is comparable with ordinary concrete in engineering behaviors.