Survey of Practice to Determine Strength of In Situ Concrete from Core Tests

Practitioners were invited to respond to a problem statement published in the November 2000 issue of the Journal of the Performance of Constructed Facilities asking for an estimate of the compressive strength of in situ concrete based on hypothetical results of compressive tests on ten cores. Responses were received from 23 persons. Several respondents provided more than one estimate. It was found that there were wide variations in practice for determination of compressive strength from cores. Estimates varied from $\mathrm{3,000}\text{to}\mathrm{5,000}\mathrm{psi}$ . The most frequent estimate was $\mathrm{4,000}\mathrm{psi}$ . The paper presents background information on code provisions relating to core testing, summarizes and discusses the responses, and offers observations based on the responses regarding investigations where compressive strength of concrete in an existing structure is determined from test of cores.