In this study, a clay with low plasticity is mixed with 12 different proportions of fly ash and slag. The fly ash and slag contents range from 0 to 20 percent and 0 to 10 percent, respectively, on the dry weight basis. Laboratory investigations include compaction, unconfined compression, triaxial consolidated undrained, and one dimensional consolidation tests. Adding fly ash and slag to the clay results in a decrease of maximum dry density and an increase of optimum water content of that clay obtained in a standard Proctor compaction test. Results also show that when only this low calcium oxide content (7.5%) fly ash is added to the clay, there is only very little improvement on the strength. The strength gain in the mixtures is primarily due to the effect of the high calcium oxide content (39.3%) slag. The coefficients of permeability for all the mixtures are of the same order of magnitude, which is 10 (super -7) cm/sec. Results from the consolidation tests indicate that additives have about the same compressibility effects on the clay. The compressive indices and swell indices of clay-additive mixtures are about 18% to 36% and 40% to 60% respectively, of the clay. For the covering abstract see IRRD 863991.