The Development And Freeze Thaw Durability Of High Fly Ash Content Concrete PDF Download

The objective of this research was to develop a freeze-thaw cycling test procedure and to investigate how the volume, moisture content, resilient modulus (Mr), and unconfined compressive strength (qu) of geomaterials, including soils and recycled materials, stabilized with fly ash change after freeze-thaw cycling. Three different types of materials (fine-grained and coarse-grained soils and recycled pavement materials) and five different fly ashes were used at different percentages (10, 12, 14, and 20 % by dry weight). Both one-dimensional and three-dimensional freezing of the specimens were considered. Freezing in three-dimensional was faster in terms of completing the freeze-thaw cycling and provided very similar results to the ones prepared in one-dimensional. Thus, three-dimensional freezing was adopted in this study without access to water (i.e., closed system). The results of this study indicated that the volume of all soil-fly ash mixtures tended to increase after freeze-thaw cycling; however, the volume change was not significant. Resilient modulus tests were conducted on all unstabilized materials, as well as on their mixtures with fly ash, while qu tests were conducted only on fine-grained soil and their fly ash mixtures. The Mr of all mixtures with one exception decreased by an average of 28.5 % when specimens were subjected to freeze-thaw cycling. The drop in the Mr of the specimens leveled off after 5 freeze-thaw cycles. A general trend of higher Mr of materials stabilized with fly ash (from 3 to 168 %), even after freeze-thaw cycles compared to unstabilized material was observed. In general, a reduction in unconfined compressive strength (qu) after freeze-thaw cycles up to 70 % was obtained. However, results showed that qu of stabilized soils that were subjected to freeze-thaw cycles were still higher (from 6 to 157 %) than the qu of unstabilized soils.