Suggested Modifications to ASTM C31/C31M for Consolidation by Rodding

ASTM C31/C31M describes the procedure of making concrete specimens in the field. Its origin can be traced to 1920, proposing rodding or stroking each 100 mm thick layer 25 to 30 times. Concrete technology has evolved tremendously over the last century, but specimens are still prepared following this 100-year-old methodology. This paper investigates the density and compressive strength of concrete cylinders for different consolidation procedures. Mixture design variations include paste volume, water-cement ratio (w/c), aggregate grain size distribution, fly ash, and water-reducing agent. An increase in compressive strength of approximately 5 MPa can be obtained if 100 x 200 mm cylinders are rodded in four layers, 25 rods each, if the slump is not over 100 mm. For all other mixtures, the current rodding procedure of two layers, 25 rods each, is recommended. For mixtures with higher slump, two layers with less rodding per layer deliver similar strength values, but the variability is high.