Sustainability has become an important issue in the concrete industry in recent years. One way to make concrete more sustainable is through the replacement of portland cement clinker with alternative cementitious materials such as fly ash. While fly ash is a waste material obtained from coal combustion in power plants that is broadly used in concrete applications, this work investigates the use of higher volumes of fly ash with an emphasis on replacing a greater cement volume than what is typically done. This paper focuses on testing performed on mortar mixtures that would be consistent with the mortar portion of a concrete bridge deck mixture for many state departments of transportation. In this work a relatively large percentage of cement (40 % or 60 % by volume) is replaced with Class C fly ash. To overcome concerns associated with slow early-age strength development that are often expressed with the high volume fly ash mixtures, the water to binder ratio by mass has been reduced from the conventional value of 0.42 to 0.30. A series of tests were performed to determine the mechanical properties, volume change, and heat development. Prewetted lightweight aggregate is also evaluated as a method of internal curing (IC), thereby reducing shrinkage, increasing hydration, and improving durability. The high volume fly ash (HVFA) mortars with IC show additional benefits that should permit a broader use of HVFA mixtures.
Citation: Cement and Concrete Composites
Pub Type: Journals
Autogenous shrinkage, cracking, high volume fly ash, hydration, internal curing, restrained shrinkage.