Precast Concrete Roof Failure

CTLGroup was retained by attorneys representing a precast concrete supplier to investigate the failure of precast prestressed concrete hollow core slabs. These slabs comprised the structural roof system for a water filtration plant in the Northeast U.S., and was showing signs of premature failure at an age of approximately 10 years. The slabs exhibited signs of heaving at their ends and concrete blowouts at the center of their span, resulting in loss of prestress force. Opposing experts concluded this distress was a resulted from chemical attack known as Delayed Ettringite Formation (DEF), and recommended roof replacement. CTLGroup engineers and scientists performed visual inspections and documented failed slabs, collected samples for testing, and performed extensive laboratory work to assess the observed distress.

CTLGroup's laboratory testing included petrographic examination of concrete cores, chemical analysis, sulfur analysis, and differential thermal analysis. Thermal modeling was performed to evaluate whether the known temperature criteria for Delayed Ettringite Formation (DEF) was satisfied.

Based on field observations and test results, CTLGroup concluded that premature failure of the slabs was caused primarily by freeze thaw deterioration, not DEF, and wholesale replacement of the roof was not necessary. CTLGroup also concluded that standard industry practice did not include considerations to guard against DEF, as it was a relatively unknown failure mechanism at the time of construction.

CTLGroup provided deposition testimony on behalf our client, and the matter was settled prior to trial.