Analysis of the static and dynamic elastic moduli of a one-coat rendering mortar with laboratory and in situ samples

Although the compressive strength is the most commonly used property to characterize mortars, it has limited representativeness in real-world applications. The deformation properties of mortars, specifically the elastic modulus, are responsible for masonry behavior. However, there is currently no standard method for determining the elastic modulus of mortars and no consensus on the best approach. Therefore, the aim of this paper is to obtain both static and dynamic moduli of a one-coat rendering mortar following the standards for calculating them on concrete specimens and verify their validity. The static modulus was determined under compression by adapting the standard for concrete specimens (EN-1352) to mortars using two gauges, and under the flexural tensile test following the standard EN-1015-11. The dynamic modulus was calculated by measuring the fundamental resonant frequencies of longitudinal and transverse vibration modes, adapting the American standard for concrete (ASTM C215) for mortar. The tests were performed on both standardized and non-standardized prismatic specimens, as well as in situ samples at various ages. The results indicated that dynamic modulus obtained from the longitudinal vibration mode was higher than that from the transverse mode, but differences were smaller using a uniaxial accelerometer than with a triaxial accelerometer. The dynamic modulus exhibited a slightly higher value and lower dispersion than the static modulus. Both moduli decreased with time and were easily correlated through linear regressions. Additionally, both moduli were correlated with flexural and compressive strength values. In situ samples had lower elastic moduli, but the compaction procedure in real works differs from laboratory tests. In summary, it was demonstrated that the procedures for calculating dynamic and static elastic moduli in concrete can be applied to mortar samples, and their effectiveness was confirmed.