Title:
Interface Shear Strength of Concrete at Early Ages
Author(s):
Dong-Uk Choi, David W. Fowler, and James O. Jirsa
Publication:
Structural Journal
Volume:
96
Issue:
3
Appears on pages(s):
343-347
Keywords:
bonded overlay; curing; shear strength
DOI:
10.14359/667
Date:
5/1/1999
Abstract:
The development of interface shear strength at early ages following placement of new concrete overlaying existing concrete was studied experimentally. Thirty-two pushoff tests were conducted to determine interface strength. Test variables were age of overlay and overlay curing method. Special powder-driven shear connectors were used across the interface in most specimens to provide some reinforcement between old and new concrete layers. Tests were performed when the age of the overlays was between 12 hr and 35 days. Test results showed that the interface shear strength was 1370 kPa or higher 24 hr after casting, and strength improved rapidly during the first 3 days. The interface strength was influenced significantly by the overlay curing method. Test results suggested that good curing of the overlays at early ages, especially during the first 3 days when the interface strength is increasing rapidly, resulted in higher interface shear strengths.