Prepackaged concrete repair materials come with data sheets listing the material's performance in a variety of lab tests, which presumably attest to the material's quality. But which of these properties are truly important to the material's performance in the field? And what values are acceptable?

These are the questions researchers attempted to answer during a 5-year lab and field testing program performed by Structural Preservation Systems Inc. and sponsored by the U.S. Army Engineer Waterways Experiment Station. The main goal of the program was to determine the material properties that influence cracking, the most common cause of premature deterioration in concrete repairs. The researchers tested 12 materials—11 commercial prepackaged repair mortars and concretes and a standard 4000-psi concrete mix. All of the repair materials were hydraulic-cement-based and six were also polymer-modified.