Question: Are there any simple guidelines for use when we get low-strength test results? The low tests seem to make owners especially nervous, and we'd like to have an authoritative document that lays out a course of action following the report of a low test.

Answer: You need a copy of "In-Place Concrete Strength Evaluation-A Recommended Practice," published by the National Ready Mixed Concrete Association. First produced in 1970, it was revised in 1979 and again in 1999. The booklet covers three aspects of the low-test problem:

  • What degree of apparent strength deficiency justifies further investigation?
  • When is an investigation required and how should it be performed?
  • How should results of the investigation be translated into action with respect to the structure and to the allocation of costs?

The booklet costs $6 for NRMCA members, $14 for nonmembers. To order a copy, call NRMCA at 301-587-1400 and ask for publication No. 133-99.