Experimental Use of Fly Ash Concrete in Prefabricated Bridge-deck Slabs

About the report:

Hydraulic cement concretes with and without fly ash were investigated to assess the suitability of using fly ash in bridge-deck concrete. Eight prefabricated concrete slabs were prepared: four were control and the remaining contained fly ash. They were used for widening two bridge structures. Slump, air content, and unit weight were determined on the freshly mixed concrete; compressive strength, permeability, absorption, freezing and thawing durability, and the air void system were determined for the hardened concrete. Depth of cover over the reinforcing steel was measured. After three winters of exposure, slabs were surveyed visually for cracks, scaling, and spalls. Half-cell readings were taken, and chloride samples obtained and tested. Fly ash concretes required a larger amount of air-entraining admixture than the controls to achieve the required air content. Although the 28-day strength tests showed that three of the four fly ash concretes did not achieve the required strength of 4,000 psi, the strength of all concretes exceeded 4,800 psi at 6 months when moist cured. The field evaluation after 3 years of winter exposure indicates that all concretes with fly ash are performing satisfactorily.

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