Title: Strength Compliance Evaluation with More than Three Core Specimens

Author(s): F. Michael Bartlett and John S. Lawler

Publication: Concrete International

Volume: 33

Issue: 12

Appears on pages(s): 46-49

Keywords: concrete, testing, acceptance, sample size, probability

DOI:

Date: 12/1/2011

Abstract:
The current procedure in ACI 318-08 for determining strength compliance of in-place concrete with low standard cylinder strength test results involves obtaining and testing three core specimens and accepting concrete if the average core strength equals or exceeds 0.85fc′ and if no single core strength is less than 0.75fc′. This article addresses acceptance criteria for samples comprising more than three core tests. It provides two approaches for determining suitable equivalent minimum-strength and two example calculations.