Title:
Factors Influencing Fracture Behavior of Old-New Concrete Bonds
Author(s):
Elmar K. Tschegg, Michael Ingruber, Cord Henrik Surberg, and Fritz Munger
Publication:
Materials Journal
Volume:
97
Issue:
4
Appears on pages(s):
447-453
Keywords:
anchor; bond; fracture; surface texture
DOI:
10.14359/7409
Date:
7/1/2000
Abstract:
The fracture properties of anchor-reinforced construction material composites (bonds) are determined by the uniaxial wedge splitting test using a simple material testing device. Such fracture tests on old-new concrete bonds with differently treated old concrete surfaces with and without anchor reinforcement have shown that the crack initiation properties are mainly influenced by the workmanship and quality of the interface between the old and new concrete. For this reason, only 50% of the resistance to crack propagation can be obtained for the interface by conventional treatments of the old concrete surface relative to the new or old concrete. By optimizing the surface roughness of old concrete surfaces, which must be matched to the aggregate size used in the old and new concrete, mechanical and fracture mechanical properties can be achieved that are comparable to those of the old or new concrete themselves. When anchors are used as reinforcements, they act as effective crack stoppers. Also, anchors reduced the width of edge cracks if the quality of the old-new concrete bond is appropriate, that is, has sufficient strength. Measures and strategies can be derived from the fracture mechanical behavior of old-new concrete bonds. They lead to an optimization and development of the quality of such old-new concrete bonds, as well as its anchor reinforcement.