Title: Concrete Q & A: Fresh Frozen Concrete

Author(s): Bruce A. Suprenant

Publication: Concrete International

Volume: 30

Issue: 9

Appears on pages(s): 75-76

Keywords:

DOI:

Date: 9/1/2008

Abstract:
During cold weather placement of a foundation, fresh concrete came into contact with a top mat of No. 5 and No. 9 (No. 16 and No. 29) reinforcing bars. During the placement, the ambient air temperature was 22 °F (–6 °C), the concrete temperature was 66 °F (19 °C), and the reinforcing steel temperature was 25 °F (–4 °C). Concrete that remained hung up on the top mat, as shown in the photo, became frozen before the placement was completed. The concrete contractor doesn’t believe the concrete remained frozen after the placement was completed and the concrete had been thoroughly vibrated. The contractor states that they followed the recommendations in ACI 306R for cold weather protection and met the requirements in ACI 306.1. They therefore believe that the concrete was frozen only temporarily and will not cause any problems. The engineer is concerned, however, that the frozen concrete may have affected the bond of the top reinforcing. How do we determine if the bond of the concrete to the reinforcing steel was affected?