Title:
Factors Affecting Bond Between New and Old Concrete
Author(s):
J. S. Wall and N. G. Shrive
Publication:
Materials Journal
Volume:
85
Issue:
2
Appears on pages(s):
117-125
Keywords:
bond (concrete to concrete); bonding; cement pastes; curing; polyvinyl acetate; shear tests; strength; tests; thickness; Materials Research
DOI:
10.14359/2329
Date:
3/1/1988
Abstract:
When new concrete is placed next to old concrete, attempts are usually made to bond the two concretes together: often a cement paste or mortar "joint" is used, as in masonry. The service stress states in bonds can vary tremendously so no single test method can replicate all these states. A method of test for bond should reflect a typical inservice stress state yet also be sensitive to variation in the strength of the bond. Four tests were evaluated, and a slant shear test was found to be the most appropriate. The effects of various parameters were evaluated theoretically with the finite element method and/or experimentally. A bond material with a modulus of elasticity similar to the adjacent concrete was found to be desirable, as was consistency in the bond material properties. Thick bond layers were found to reduce bond strength considerably and copolymer polyvinylacetate was found to be a poor bonding agent over a wide range of curing conditions and mortar mix designs.