The experimental results of composite geo-material indicated that the stress-strain relationship and the unconfined compressive strength are strongly influenced by mixing conditions such as air-foam content and bottom ash content. Maximum compressive strength of CGM increased with an increase in cement content, but decreased with an increase in air-foam content. Most of the failure types of specimens were general shear failure. Bulging failure, however, was shown in the specimen with high air-foam content. It was observed that the compressive strength as well as the stiffness of composite geo-material increased by adding bottom ash due to angular shape of bottom ash and the pozzolanic reaction in the mixture. The 28-day strength of composite geo-material was 1.5∼2.3 times higher than the 7-day strength. The moist unit weight strongly depended on air-foam content as well as bottom ash content added to the composite geo-material. In composite geo-material, secant modulus (E 50) also increased as its compressive strength increased due to the inclusion of bottom ash. Secant moduli of CGM were in the range of 185 to 480 times the value of unconfined compressive strength. The stiffness of CGM was greater than that of unreinforced lightweight soil due to the reinforcing effect of bottom ash.