In this study, it is investigated effect of construction waste to some engineering properties of a high plasticity clay. For this reason, some chemical properties of the soil sample and construction waste are determined. The consistency limits and standard compaction tests are carried out on the clayey samples in weight with the ratios 2%, 5%, 10%, 15%, 20%, 25%, 30% and 35% of the construction waste passing from the sieve of No 40. The constant-volume swelling and unconfined compression tests are also conducted on both pure clay and the mixtures in weight with the ratios 5%, 10% 20% and 30% of the construction waste compacting at the optimum water content and maximum dry density. From the results of test, it is found that the construction waste can be effectively used at a ratio of 10%-20% for both decreasing the swelling potential of clay and increasing the unconfined compression strength of that.