Assessment of the early-age compressive strength of concrete

This paper analyses the results of concrete compressive strength tests on cubic samples with different w/c ratios during the early stage of hardening (at 7, 14, and 28 days). Statistical and strength parameters were assessed and the quality of the concrete was estimated. The expected concrete grade, C25/30, was confirmed against the formulation provided by the prefabrication plant. Then, the amount of individual constituents was adjusted to obtain the target grade of concrete, i.e., C20/25. The concrete grade was estimated based on concrete strength parameters measured at three time points and compared with the expected 28-day strength values determined as per Eurocode 2 and with the concrete grade defined by these values. The paper also provides an overview of the most widely used methods of testing concrete compressive strength.