Designing and Characterizing the LEED Concrete for Drilled Shaft Applications

Abstract

In order to meet Leadership in Energy and Environmental Design (LEED) guidelines, research is underway to produce concrete (LEED concrete) with alternative binders. LEED concepts provide for environmentally sustainable construction. Since its inception in 1998, LEED has grown to encompass projects in 50 US States and over 30 other countries. In this study, a LEED concrete mix with 70% Class C fly ash as replacement for cement, with appropriate chemical admixture was designed and tested. The behavior of LEED concrete mixture was compared to a conventional Portland cement control mix. The LEED concrete mixture reached similar to higher strength as Portland cement concrete with time due to the pozzolanic properties of Class C fly ash. Internal curing temperature of the LEED concrete mixture was reduced with the addition of fly ash and the setting time of the LEED concrete mixture was increased, which is generally achived by using a retarder in the conventional concrete mix. In addition, volume changes due to shrinkage, and the water absorptions by the LEED concrete mixture were lower than the conventional Portland cement concrete mixture at all ages, indicating that durability of the LEED concrete mixture was comparable or even better than the conventional Portland cement concrete mixture. By using appropriate chemical admixture, highly workable LEED concrete mixture with up to 200 mm (8 in) slump was developed for drilled shaft and/or other pile foundation applications.