|Contributions||Dikeou, J. T.|
|The Physical Object|
|Number of Pages||17|
Additional Physical Format: Online version: Dikeou, James T. Fly ash increases resistance of concrete to sulfate attack. Washington, D.C.: United States Department of . Fly Ash Increases Resistance to Sulphate Attack August 95 strong water reducer and aids in reducing water/ cementitious ratio. Lowering water/cementitious ratio significantly can lead to more sulphate resisting concrete. To ensure the most durable concrete possible, fly ash is an essential ingredient when the project will beFile Size: 20KB. Class F Fly Ash INCREASES RESISTANCE TO SULFATE ATTACK Sulfate Attack Is A Two-Phased Process Sulfates combine with calcium hydroxide generated during cement hydration to form calcium sulfate (gypsum). The volume of this gypsum is greater than the sum of its components causing internal pressure and expansion, which fractures the Size: KB. the resistance of sulfate attack, and the sulfate resistance is increased with the increase of amount of fly ash. The reason may be connected with the pozzonlanic reaction of fly ash.
Figure Summary of sulfate expansion of concrete containing 45 percent fly ash. Effect of Fly Ash Content. Concrete contain 35 and 45 per cent fly ash, by volume, was cast to investigate of the fly ash content on the sulfate resistance of concrete. Liu et al. [8, 9] demonstrated that fly ash could increase the deterioration of concrete partially immersed in sulfate solution, and indicated that chemical sulfate attack rather than sulfate salt. This partial replacement of portland cement with apozzolan such as low calcium fly ash, ground granulated blast furnace slag, or silica fumeequally reduce the potential for sulfate attack. These pozzolans consume the calcium inthe pore water, reduce the total mass of . The consequences of sulfate attack include not only disruptive expansion and cracking, but also loss of strength of concrete due to the loss of cohesion in the hydrated cement paste and of adhesion between it and the aggregate particles. Sulfates combines with the C-S-H, or concrete paste, and begins destroying the paste that holds the concrete.
the fly ash will be in terms of reducing the heat of hydration (Thomas ), controlling expansion due to alkali-silica reaction (Shehata ), and providing resistance to sulfate attack (Shashiprakash ). These issues are addressed in sections Effect of Fly Ash on . Fly ash increases the cementitious compounds, minimizes water demand, and reduces bleed channels – all of which increase concrete density. These factors yield concrete of low permeability with low internal voids. Durability is increased with regard to freeze-thaw damage and disintegration from attack by acids, salts or sulfates. Technical Bulletin 6File Size: KB. The partial replacement of cement by fly ash is recognised as effective in giving increased resistance to attack by sulphate in groundwater and soils. BRE Digest allows fly ash/cement for almost all groundwater and soil conditions for which sulphate-resisting cement is allowed, and draft ENV X also allows fly ash/cement within defined Cited by: Fly ash also improves the resistance of concrete to Na 2 SO 4 attack. This effect is not simply the consequence of dilution of PC, since replacement with sand increases expansion. Unlike PC, whose sulfate resistance is relatively insensitive to the duration of curing, the effectiveness of fly ash is highly dependent on curing time, with longer curing periods yielding higher resistance. ,