Influence of the Use of Additives on the Properties of Compacted Gypseous Soils

In this paper, an experimental study is carried out on the effect of three different additives to gypseous soils in order to improve the compaction properties of the gypsum soil. the additives used in this study are recycled asphalt pavement passing from sieve no.4 (rp), recycled asphalt pavement passing from sieve 3/8 and remaining on sieve no.4 (rr) and rice husk ash (rha). the percentages of (rp) and (rr) are varied between (3-9)% by weight in the first and second series; whereas the percentage of rice husk ash was between (3-9)% by weight in the third series. in the fourth and fifth series, the percentage of (rha) was kept constant (6%) by weight, while the percentage of (rp) and (rr) varied from (3-9)% by weight. the results showed that the best improvement in compaction characteristics is achieved when the sample is tested by adding a mix of (rr) and (rha), the maximum dry density increases with the increase in the mixing content, while the opposite is true for the optimum water content.