Development of Self-Consolidating Concrete for Prestressed Bridge Beams

摘要

Sixteen self-consolidating concrete (SCC) mixtures were developed for use in precast, prestressed bridge beams in Texas. The mixtures featured two different sets of aggregates-namely with river gravel or crushed limestone coarse aggregate-and varied in sand-aggregate ratio, paste volume, and paste composition. The 16-hour compressive strengths (release strengths) ranged from 4,500 to 10,500 psi (30 to 70 MPa) depending on the mixture proportions and curing temperature history. The 28-day compressive strengths ranged from 11,000 to nearly 15,000 psi (75 to 100 MPa). The SCC mixtures were developed to achieve the necessary release strengths while balancing the requirements for adequate workability and durability. This paper discusses the need for higher paste volumes and sand-aggregate ratios to achieve SCC workability requirements and the implications for hardened properties. Semi-adiabatic and isothermal calorimetry measurements performed on concrete and paste specimens, respectively, and compressive strength measurements indicated that although the SCC mixtures exhibited slightly delayed setting times in some cases, they generated heat at a faster rate, generated more total heat, and developed higher 28-day strength for a given release strength. Compared to conventional mixtures with the same release strength, the SCC mixtures exhibited unchanged or slightly reduced shrinkage except when one specific admixture was used.