ABSTRACT

This chapter discusses the use of acceptance test results from testing laboratories as a means to quantify the variability, identify its main causes, and reduce it.

The annual NRMCA Industry Data Survey results indicated that between 2006 and 2010 a ready mixed concrete plant in the United States produced an annual average of 50,000 yd3 (38,000 m3) of concrete. Assuming that, on average half of that concrete is supplied to projects that include job-site acceptance testing at a frequency of one in every 150 yd3 (115 m3; minimum requirement per ASTM C94), it can be calculated that a concrete plant would receive about 14 project data sets/ month. The test data are likely to be from different mixtures and/ or projects. These data typically include slump, air content, temperature, density, and compressive strength at two ages (typically, one cylinder at 7 days, and two cylinders at 28 days). The density test results are useful for quality assurance and have been required in ASTM C94 and more recently incorporated in ACI 301-10.