Kiefer Creek Overpass, St. Louis, MO

For this project, both concrete maturity testing and cylinders were used. In one section of the bridge deck, the data from the Con-Cure system showed that the temperature of that area was virtually flat, indicating very little strength gain while other areas showed normal strength gain. While the Con-Cure system could not tell the contractor WHAT was wrong, it was obvious something was not right with the pour.

Further investigation revealed that one truck driver had added 2.5 gallons of retarder instead of superplasticizer. The bridge deck remained plastic for 6 days where the retarder was placed. Since no cylinders were taken from the problem truck, reliance on cylinders alone would have been erroneous and potentially dangerous if the forms had been stripped.