CHARACTERISATION OF RAW AND TREATED DE-OILED BLEACHING EARTH FOR SUPPLEMENTARY CEMENTITIOUS MATERIAL

Abstract

This study assessed the potential of raw and treated De-Oiled Bleaching Earth (DOBE) as a supplementary cementitious material (SCM) by analysing its characteristics. DOBE, originating from Spent Bleaching Earth (SBE), is a waste of the palm oil refining industry, often discarded in landfills, hence presenting environmental hazards. Study on DOBE for its potential as an SCM is still limited, particularly on how its characterisation impacts its reactivity, which in this study was evaluated through the Strength Activity Index (SAI) test. Apart from examining its general properties, raw and treated DOBE were also analysed using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and laser diffraction. The treatment at 700°C for one hour improved its pozzolanic reactivity by raising its amorphous silica content from 56.7% to 64.7% and removing residual oil and volatile contaminants. The Strength Activity Index (SAI) tests indicated that the treated DOBE achieved 98% (20.71 MPa) of the control mix strength at 7 days and 107% (29.05 MPa) at 28 days, exceeding that of ordinary Portland cement (OPC). The findings validate that treated DOBE complies with ASTM C618 criteria for Class N pozzolans, establishing it as a suitable SCM. Nevertheless, issues such as loss on ignition, moisture content, and oil content must be resolved to enhance its performance. This study emphasises DOBE's capacity to improve cement sustainability by reducing its dependency on cement and mitigating environmental concerns. Future studies need to include the assessment on its durability, shrinkage, and ideal replacement ratios in concrete mixes.