Fly ash: Usually decreases water demand

Fly ash usually decreases water demand. Most of the other pozzolans increase the water demand. Pozzolans reduce bleeding because of fineness; reduce the maximum rise in temperature when used in large amounts (more than 15% by mass of cementitious material) because of the slower rate of chemical reactions; which reduce the rise in temperature. Introduction This TechNote discusses the implications of limits on the proportions of fly ash in project specifications. This TechNote addresses only fly ash that meets current, applicable specifications such as ASTM C618. Prescriptive specifications for concrete construction projects often include a clause that limits the proportion of supple-mentary cementitious materials (SCMs) (Obla and Lobo 2015). For example, the clause incorporated in Section 033000 pertaining to cast-in-place ... In this article named “ Production of Fly Ash “, the process of fly ash production will be discussed briefly. Fly ash is a by-product of burning coal in an electrical generating station. The following figure shows a typical layout of a coal-burning generating station. Notes/Preview Preview Description Fly ash is used in concrete and other portland cement-based systems primarily because of its pozzolanic and cementitious properties. These properties contribute to strength gain and are known to improve the performance of fresh and hardened concrete, mortar, and grout. The use of fly ash typically results in more economical concrete construction. This report gives an overview of the origin and properties of fly ash , its effect on the properties of hydraulic ...