Evaluation of Concrete Bridge Mix Design for Control of Cracking

This project examines a series of differing concrete mix designs in order to begin the process of selecting an optimum design for VTrans bare concrete bridge/ bridge deck projects. The desire is to lower the amount of cracking that is present on the bridge decks. This could be possible by using shrinkage control agents and/or by reducing the amount of cementious material, which would result in a reduction of needed mix water, based on the current water/cementious ratios. Laboratory testing of this type is needed in order to provide a basis for support for using shrinkage reducing admixtures and/or adjusting current mix designs. Mixes will fall within three groups. The first group will be the control group, consisting of batches of normal high performance concrete (HPC), classes A and B. The second group will make use of two different methods of shrinkage control within the control mixes, a shrinkage reducing admixture and a shrinkage compensating cementitious admixture. The third group will make use of an optimized gradation of aggregate and other various alterations. Since January 2009, seven of the nine original mix design test batches have been produced, along with some additional test batches for greater comparison in the study. Associated shrinkage, compression strength, and modulus of rupture testing are progressing.