Reducing the Specimen Size of the AASHTO T 97 Concrete Flexural Strength Test for Safety and Ease of Handling

This study examined the feasibility of using smaller-size concrete beam specimens to conduct flexural strength tests of concrete with a simple beam with third-point loading according to the AASHTO T 97 procedure. Twenty-two mixtures containing four coarse aggregates (limestone, diabase, gravel, and granite) with maximum size varying from .75 to 1.5 in. were prepared. A total of 132 specimens measuring 4 x 4 x 14 in. and 132 standard-size specimens (6 x 6 x 21 in.) were tested. The 4- X 4-in. specimens yielded higher flexural strengths, as expected from the literature review. Analysis of the flexural strength test data revealed a very good correlation (R-2 = .93) between the smaller- and standard-size beams. An equation is proposed to convert the flexural strength of the smaller-size specimen to the flexural strength of the standard-size specimen.