Seawater Influence On The Strength Of Cement Treated Fly Ash

In recent urban developing, many constructions are need to carry out on the soft soils.Such as Qingdao Jiaozhou Bay dispersing lots of wet fly ash filled and marine clay soils with higher water content, lager void ratio and lower bearing capacity which is low. However, cement mixing method is a new way for soft soil stabilization which has been widely used in seaside cities.The method which utilites cement to mix with in-situ soft clay soils, form a certain strength integrity and water stability soil-cement matrix through soil-cement reaction. Cement mixing method involves deep mixing method and powder-jetting mixing method. The study stabilizes the soft soil foundation with powder-jetting method. However, surrounding seawater can corrode the soil-cement matrix which will limit the application of engineering practice.The experiment is studying the seawater influence on the strength of cement treated fly ash. First, soaking dry fly ash in seawater under saturation condition for 180 days to simulate wet fly ash, then stabilizes it with Portland slag cement and ordinary Portland cement separately, and dry fly ash as a comparison. Four cement content 8%,12%,16%,20%, and immerging the soil-cement samples under seawater until designed curing time, and test the unconfined compressive strength and analyze corresponding mechanism through SEM. The experiment concludes that seawater environment has negative effects on the strength of soil-cement matrix and slag cement can against seawater erosion. The strength of soil-cement matrix prepared with dry fly ash are higher than wet fly ash. The lower pozzolanic activity of wet fly ash leads to lower soil-cement matrix strength and anti-erosion. Whatever conditions, the stress-strain curves of soil-cement matrix show the same way as curing time growth,and the water content has various degrees reduction, and more cement content more water content reduction.