Evaluation of CDOT Specifications for Class H and HT Crack Resistant Concrete

摘要

This study examined the performance of concrete mixtures designed to increase cracking resistance for Colorado bridge decks. The current CDOT Class H and HT concrete mixtures and nine other mixtures were investigated to aid in the development of a more crack resistant concrete specification. A total of eleven concrete mixtures were designed, batched, and tested for their fresh and hardened concrete performance. Specifically, the designs differed by type of cement, w/cm, cement content, supplementary cementitious materials (SCMs), use of chemical admixtures, and aggregate type. Compressive strength, permeability, freeze-thaw resistance, and restrained shrinkage cracking were evaluated and documented in this report. Lower w/cm resulted in high early compressive strengths and rates of strength and strain development. Increasing the w/cm to 0.44 and Class F fly ash replacement levels up to 30% was beneficial in controlling strength gain. A low cement content mixture with increased w/cm and fly ash replacement proved to be beneficial. When SCMs were not utilized, a low cement content of 6.0 bags was beneficial. When SCMs were used, increased cement content helped to maintain the same properties. Type G, coarse-ground cement was beneficial to strain and strength at the higher w/cm of 0.42 and low cementitious materials content. At a lower w/cm of 0.38, the mixture behaved similarly to the control mixture fabricated using Type II cement, developing strain and strength at an average rate.