Abstract:
Cement industry has been participated in the waste management by using different kinds of industrial wastes
as alternative fuel or raw materials in manufacturing process. In this work, cadmium was introduced into the raw
material with the variation of initial concentrations of CdO ranging from 0.1-2.0% by weight. The clinker
characteristics were analyzed by X-ray diffraction(XRD) and scanning electron microscope(SEM) with energy
dispersive X-ray spectrometer(EDS). Results showed that cadmium inhibited the formation of C3S and C2S
which are the major phases of clinker. The new compounds of cadmium as CdSO3 and CdAl2O4 were identified
in the composition of clinker. It was found that cadmium affected on the clinker properties by decreasing
the compressive strengths and retarding the setting time. In the study of cadmium leaching behavior, using
Toxicity Characteristic Leaching Procedure Test(US.EPA), cement mortars doped with cadmium up to 2.0% by
weight was not classified as hazardous waste, as the concentration of cadmium leached from the mortar was 0.07 mg/L
which is lower than the regulated value(1 mg/L). However, with Waste Extraction Test following were
Thailand regulation, mortars with concentration of cadmium equal or higher than 0.1% by weight were
classified as hazardous waste, as the concentration of cadmium leached from mortar was higher than 1.0 mg/L
which is the regulated value.