Due to urbanization, it is near impossible to construct civil infrastructures without encountering soil materials with poor geotechnical response. In soil re-engineering, the trending practise is the use of supplementary cementitious material with the aim of reducing carbon footprint and construction cost. This has necessitated the usability of integrating the blends of palm oil fuel residue (POFR) and calcium carbide residue (CCR) in the amelioration protocols of two soil materials. The amelioration protocols were implemented by inclusion of 0, 2, 4, 6, 8 and 10 % dosages of POFR and 0, 2, 4, 6, and 8 % dosages of CCR by requisite weight of soil materials. The experimental works were carried out in three phases, namely: material characterisation, mechanical performance and microstructural testing. Judging from the index performance, BCS and RLS are clayey materials having a plasticity index of 28.70 and 18.97 % respectively. With regard to the mechanical performance (compaction, California bearing ratio and durability), the inclusion of the blends of POFR-CCR into the soils (BCS and RLS) activated a positive response and was later validated via means of microstructural tests. This research has shown the potential of blended waste residues in soil re-engineering studies. The study was vividly achieved through qualitative approaches, namely: scanning electron microscopy and Fourier transform infrared.