Effects of sample dimensions in compressive strength tests of masonry wall products

Introduction. State standards for testing ceramic masonry wall materials of plastic molding establish grinding as the main method of smoothening supporting (loaded) surfaces. Therefore, studies were conducted on the effect of sample dimensions on the compressive strength of tested masonry products. The effect of a scale factor on the measured strength of brick and stone has so far been only partially reflected in the standard for test methods (GOST 8462 “Wall materials. Methods for determining compressive and bending strength”). According to both Russian and foreign specialists, shape factors values, provided in EN 772-1 European standard “Methods of test for masonry units. Part 1. Determination of compressive strength” need to be adjusted as they do not take into account the void ratio of masonry products and the sample material type.

Aim. To assess the effects, caused by the geometric dimensions of masonry product samples, as well as the void ratio and other characteristics, on compressive strength according to the results of laboratory tests. Materials and methods. As a result of conducted control tests of ceramic and silicate single and thickened bricks with a void ratio of up to 27 %, measured values of product compression strength were compared to determine the value of transition coefficients.

Results. The performed studies confirmed the shape coefficients, adopted in EN 772-1, to require an adjustment. Based on the results of studies, conducted in Russia and abroad, conclusions and recommendations were made to take into account the dimensions of tested samples during strength tests.

Conclusion. Performed studies and analysis of experimental results have demonstrated that in order to increase the accuracy of determining the strength of test samples, taking into account their shape and void ratio, it is necessary to have several tables with shape factors. Currently, until reliable data about the void ratio effect of the masonry material on test results are obtained, it is advisable to take into account only the height of the sample (“longitudinal bending”).

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