Performance Criteria for Ready Mixed Concrete: Where Are We Today? (Part 1)-Prescription to Performance (PDF)

Prescription to Performance (PDF)

Pdf Summary

The Minnesota Department of Transportation (MnDOT) transitioned from prescription-based to performance-based specifications for high-performance concrete (HPC) in bridge decks to address widespread cracking issues observed in bridge decks across the United States. Initiated in 2004, MnDOT began collecting construction data for bridge deck pours and collaborating closely with the Ready-Mix industry to develop a specification for HPC.<br /><br />In 2006, MnDOT started working on a high-performance concrete bridge deck specification and specified its first HPC bridge deck in 2009. The goal was to achieve a durable and crack-free configuration, leading to the construction of their first 100% crack-free bridge deck in 2010. Despite continued observations of some cracking influenced significantly by the design of bridges, the performance of bridge decks has improved over time with the application of evolving concrete mixtures and specifications.<br /><br />MnDOT’s efforts included reducing cement content, working with well-graded aggregates, and optimizing water/cement ratios. Specifications evolved with contractor input, ensuring practicality and workability. By 2013, key specifications included a maximum of 40% supplementary cementitious materials by weight and a water/cement ratio ranging from 0.40 to 0.45, among other detailed parameters to tackle cracking and enhance durability.<br /><br />Moving forward, innovations such as Internal Cure Mix Designs and the addition of concrete fibers have been adopted. These approaches include ensuring no fly ash but allowing up to 35% slag, using lightweight sand, and incorporating lightweight aggregates to optimize the internal curing of concrete decks. This consistent evolution of concrete formulations and practices is central to enhancing the performance and longevity of Minnesota’s bridge infrastructure.

Keywords

MnDOT

high-performance concrete

bridge decks

performance-based specifications

crack-free

cementitious materials

internal curing

concrete fibers

Ready-Mix industry

infrastructure longevity