Deviating conversion factors between compressive strength values obtained with cylinders or cubes were introduced for lightweight concretes (LC) and normal weight concrete (NC) in Model Code 90 [1] and adopted in the following generations of European concrete standards, although the need for verification was expressed in [2]. No publication was found which addressed the topic since and confirmed or rejected this change. Additionally, no information is available in standards regarding the conversion of LC strength results obtained with different specimen sizes or how to account for the impact of alternative curing regimes. These effects were investigated for a series of nine LC covering the strength range from 15 to 70 MPa and one NC. It turned out that experimentally obtained conversion factors between LC cylinders and cubes (1.17 to 1.26) correlate rather with the factor given for NC (1.23) in Model Code 90 [1], EN 1992 [3] and EN 206 [4] than with the one for LC (1.10). Thus the conversion factor for LC in these standards may result in an overestimation of the achieved strength class, if cubes are tested only as it is common in e.g. The Netherlands [5], Austria [6], Belgium [7], Germany [8] and U.K. [9]. The conversion factors used to account for the impact of the curing condition and those used to convert strength results between different cubes sizes turned out to be the same for LC as for NC as well. It looks very much as if there is no need for deviating conversion factors for LC at all.    «

Deviating conversion factors between compressive strength values obtained with cylinders or cubes were introduced for lightweight concretes (LC) and normal weight concrete (NC) in Model Code 90 [1] and adopted in the following generations of European concrete standards, although the need for verification was expressed in [2]. No publication was found which addressed the topic since and confirmed or rejected this change. Additionally, no information is available in standards regarding the convers...    »