The research work examined the modification of expansive soils with bagasse fibre to improve its engineering properties for road pavement structures. Preliminary investigations classified the clay soils as A – 7 – 6 on the AASHTO Classification System and soils are dark grey at all conditions and percentage (%) passing BS sieves #200 are 73.85%, 67.38%, 6.35%, 82.35%, and 71.55%. Comparative results confirmed a decrease in plastic index properties of clay soils. Compaction test results showed a decreased in MDD values while OMC recorded increased values due to bagasse fibre inclusion. Results obtained showed an increase in UCS with an increase in fibre percentages to soil corresponding ratio. Relative results showed an increased in CBR values with an increase in bagasse fibre percentages to a peak ratio of 0.75% to soil ratio. The entire results showed the potential of using costaceae lacerus bagasse fibre (CLBF) as admixtures in the treatment of clay soils. The swelling potential of treated soil decreased with the inclusion of bagasse fibre up to 0.75%.