Checklist for Making More Climate-Friendly Concrete
• Adjust specifications to avoid requiring concrete strength more quickly than it is actually needed. A 56-day strength should be adequate for most jobs, and allows more time for pozzolanic reactions to take effect. Making this change should allow for a reduction in the amount of cement used, with or without the addition of a mineral admixture. • Test the strength and performance of any nonconventional mix. • Mixes with Class F fly ash or ground granulated blast furnace slag are especially appropriate for applications where sulfate attack and/or alkali-silica reactions are possible. • Class F fly ash is an excellent material for high-mass applications, in which internal heat gain can be a serious problem. • Class C fly ash can potentially be used with little, if any, Portland cement. • As rice hull ash becomes commercially available, it may prove an excellent substitute for more expensive, harder to handle silica fume. Rice hull ash may also make the use of air-entraining admixtures unnecessary.
