New Pull-Off Method Aids in Concrete Repair
One of the central problems in dealing with concrete is making repairs that will not fail prematurely. This failure is often due to the repair material being applied to a damaged or improperly prepared substrate or because there is inadequate bond strength between the repair material and the substrate. In order to make concrete repair more reliable, ASTM Committee C09 on Concrete and Concrete Aggregates has created the newly approved ASTM standard, C 1583, Test Method for Tensile Strength of Concrete Surfaces and the Bond Strength or Tensile Strength of Concrete Repair and Overlay Materials by Direct Tension (Pull-Off Method).
There was a strong need within the concrete industry, especially those involved in concrete repair, for a test method to evaluate the condition of a concrete surface before repair and to evaluate the bond of repair materials to existing concretes, says Committee C09 chairman Nicholas Carino, a research structural engineer working in the Building and Fire Research Laboratory at the National Institute of Standards and Technology in Gaithersburg, Md.
The test method, which is under the jurisdiction of ASTM Subcommittee C09.25 on Organic Materials for Bonding, chaired by David Elmendorf, can be used in both field and laboratory situations to determine any of the following:
The near-surface tensile strength of the substrate as an indicator of the adequacy of surface preparation before applying repair or overlay material;
The bond strength of a repair or an overlay material to the substrate;
The tensile strength of a repair or overlay material after the material has been applied to a surface; and
The adhesive strength of bonding agents.
Carino says that this test method will prove useful to manufacturers of repair materials during product development, as well as to specifying agencies to evaluate alternative materials for repairs.
For further technical information, contact Nicholas Carino, NIST, Gaithersburg, Md. (phone: 301/975-6063) or David Elmendorf, Sika Corp., Lindhurst, N.J. (phone: 201/933-8800). C09 meets June 13-16 during the June Committee Week in Kansas City, Mo. For membership or meeting details, contact Jim Olshefsky, ASTM International (phone: 610/832-9714). //
Copyright 2004, ASTM International