s part of the seismic upgrade of a 20-million-gallon drinking water reservoir, we are replacing all sealants in the floor and wall control joints. A typical sealant reservoir is 11_2 inches deep, 1_2 inch wide at the bottom, and 3_4 inch wide at the concrete surface. The tank has been drained, but the concrete is damp and can't be dried economically. What joint sealants can be used to replace the existing sealants?
The results of tests by the U.S. Bureau of Reclamation may help. Released in December 1993, Report No. R-93-18, "Elastomeric Canal Sealants: Application to Wet Concrete" describes the performance of 16 sealants applied in both damp and underwater conditions. Test specimens were prepared in accordance with ASTM C 719, "Standard Test Method for Adhesion and Cohesion of Elastomeric Joint Sealants Under Cyclic Movement (Hockman Cycle)." Twelve specimens were prepared for each sealant: four on dry concrete, four on damp concrete, and four on concrete placed underwater. After curing, half the sealant specimens were tested for ultimate tensile strength and elongation. The other half were tested for tensile modulus of elasticity at 25% and 50% elongation. These modulus specimens were then placed underwater to simulate service conditions and retested for tensile modulus every two to four weeks for 26 weeks. Twelve of the 16 sealants received high or moderate scores when applied to damp concrete. Four of the sealants received high or moderate scores when applied underwater. For copies of the test report, contact Jay Swihart at the Bureau of Reclamation (303-236-3730, ext. 436; fax: 303.236.4679); e-mail: jswihart@usbr.gov