Size effect in concrete beams

This paper will report on an experimental investigation into the size effect in the strength of hardened cement paste (nominal compressive strength 40 MPa) and high strength concrete (nominal compressive strength 110 MPa) as measured in three point bending. The aim of the investigation is to judge the range of applicability of the various size effect formulae available in the literature. With this aim in mind, the failure loads have been analysed according to the size effect formulae of Bazant and of Karihaloo for the notched beams and according to those of Bazant and of Carpinteri for the unnotched beams. The results of this analysis will be presented. Improvements to Karihaloo’s size effect formula will also be proposed.