The potential of cement stabilized shale quarry dust for possible use as road foundation material

Abstract

This research investigated the potential of cement stabilized shale quarry dust for possible use as road foundation material. From the results, the shale consists mainly of SiO 2 (27.7–60.1%), Al 2 O 3 (7.30–17.9%), CaO (3.91–32.3%) and LOI (4.93–18.8%). The shale quarry dust (SQD) in its natural state had an average liquid limit (LL) as 38%, plasticity index (PI) as 24% and fines fraction as 14%, which is regarded as poor material according to American Society for Testing and Materials recommendation. The plasticity, compaction, California bearing ratio (CBR) and unconfined compressive strength (UCS) of the SQD were evaluated in its natural state and when mixed with varying percentages of cement. When stabilized with 3% cement, the strength parameters such as CBR and UCS showed improvement by about 20 and 25%, respectively, while the swellability indicators; plasticity and shrinkage limit reduced by about 56.2 and 46.6%, respectively, suggesting substantial improvement in the volume stability, strength and stress–strain properties and continued strength gain with time of the cement treated materials. The presence of the carbonate minerals contributed to the improved strength of the SQD for a given cement type and dosage. The beneficial changes in geotechnical properties of SQD when treated with 6% Portland cement, indicate that treated shale material satisfy most Nigerian specifications for highway fill and embankment, base and sub-base material. Their use, in heavy traffic highway, however, may be handled with caution as the continued high LL may likely imply some swelling on moisture influx.