Reuse of light-emitting diode manufacturing process sludge in cement concrete

The purpose of this study is to investigate the use of the sludge that is a by-product of the light-emitting diode (LED) manufacturing process to partially replace cement in cement concrete. Two water-to-cementitious-material ratios, w/c = 0.5 and 0.7, are used. LED sludge powder replaced 5, 10 and 20 wt% of the cement in sludge-blended cement concrete (SBCC) specimens. These molded cylindrical specimens, 10 cm in diameter and 20 cm in height (10 cm 013, x 20-cm H), are subjected to compressive strength test and other mechanical properties tests. The properties of the LED sludge samples are determined using scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM/EDS) and X-ray diffraction (XRD). The experimental tests reveal that the compressive strengths of SBCC specimens are comparable to those of ordinary Portland cement concrete (OPCC) specimens at all curing ages and that the other mechanical properties are also similar. These findings indicate that LED sludge can be converted into a useful resource, thereby avoiding the problems associated with its disposal and improving its environmental sustainability.