University of Utah
Admixtures; Bridge decks; Cracking; Mix design; Shrinkage; Specifications
Concrete mixtures designed or constructed incorrectly as bridge decks can lead to shrinkage cracking. There have been lots of cracking found on bridge decks in Utah. The new shrinkage cracking apparatus built at Utah Department of Transportation (UDOT) can be used to verify in advance if the mixture design can lead to a potential shrinkage cracking problem. The Phase I of this project resulted in building the apparatus to test restrained shrinkage of mixture designs. A Phase II is needed now to understand how specific mixture changes can affect restrained shrinkage crack potential. The objectives are to determine mixture proportions and admixture effects on the age of cracking based on the UDOT modified restrained ring shrinkage test. This will be done by: (1) If needed, the test apparatus from Phase I may be further refined or modified (such as applying humidity controls); (2) Recreate and test restrained shrinkage of bridge deck mix designs identified from Phase I; and (3) Test changes to mixture proportions (potentially including adding water in the field) and different material effects (potentially including lightweight aggregates, or dosage of water-reducers) on restrained shrinkage. The expected results will be: (1) Determine if any existing approved Utah bridge deck mixtures can cause restrained shrinkage issues; and (2) Determine if changes to mixtures can cause shrinkage issues.