Mass Concrete Drilled Shafts: Specification Landscape and Recommended Revisions-Video

Video Transcription

Video Summary

The presentation examines how mass-concrete requirements should apply to large-diameter drilled shafts, combining research and practical experience. As shafts grow larger, heat buildup may cause delayed ettringite formation (DEF), which can lead to cracking, while temperature differences may also cause thermal cracks. The speaker argues that drilled shafts should not be exempt from mass-concrete provisions, but that current rules often copy above-ground requirements inappropriately.<br /><br />Recommendations include allowing peak temperatures up to 185°F when sufficient supplementary cementitious materials are used, rather than enforcing the common 160°F limit. For most buried shafts, temperature-differential limits are unnecessary because resulting cracks are generally minor and not visually exposed; exceptions may apply in aggressive ground conditions. Monitoring should continue only until the temperature peak is confirmed, typically for 24 hours afterward. Specifications should also clearly define the consequences of exceeding limits and assign responsibility fairly. The speaker emphasizes that thoughtful thermal-control planning can reduce the risk of exceedances.

Keywords

mass concrete

drilled shafts

thermal cracking

delayed ettringite formation

temperature limits