recycling of construction and demolition gypsum wastes as stabilizer of soft clay soil and effects of drying-rewetting frequency on the treated soil stability

the continuous growth in civilization and population have led to upsurge in generation of construction and demolition (c d) wastes. a considerable part of c d wastes is gypsum wastes that together with its derivatives are classified as a group of binding agents in soil stabilization and immobilization and upgrading soil durability. in this study, the possibility of using gypseous wastes as a binding agent was investigated. moreover, soil stabilized with recycled gypsum was tested under different dry-wet cycles as well as multiple dry-rewetting to assess the stability of improved soil. different amounts of gaseous waste (0, 5, 10, and 20%) and 5% cement and 5% lime were added to clay soil at various curing conditions (0, 7, 14, and 21 days). then, durability of samples was tested by wetting/drying cycles (0, 1, 2, and 3 cycles). soil characteristics including compaction, unconfined compression strength, atterberg limits and soil durability were assessed for all samples. results demonstrated significant increase of the unconfined compressive strength in clay by addition of gypsum waste, cement, and lime. however, we detected a significant reduction in the unconfined compressive strength of the samples in the third cycle of wetting-drying test.