Compressive strength, dynamic, and static modulus of cement-lime laying mortars obtained from samples of various geometries

Abstract

Correlations between compressive strength and modulus of elasticity resulted from cement-based materials of different geometries can help researchers to compare experimental data of studies that applied procedures described by different characterization standards. Due to the absence of systematic studies about the correlation between compressive strength, dynamic, and static modulus of cement-lime masonry mortars, this experimental program was carried out to determine empirical relationships between these mechanical properties, based on tests of 108 samples of shapes and sizes used in quality control of structural masonry: (4 × 4 × 16) cm prisms, 10 cm cubes, (5 × 10) cm cylinders, and (10 × 20) cm cylinders. Different cement-lime masonry mortar compositions with 28-days compressive strength between 3 and 21 MPa were evaluated. The 45 new empirical models developed in this work define the relationships between mechanical properties resulted from the various sample types. Comparisons with correlations reported in previous literature for different mortars types were also made. The compressive strength of cement-lime masonry mortars is directly related to the mutual influence of restraining effects of loading platens and the volume of the mortar specimen, since larger size specimens were more likely to contain portions with lower strength. Size and shape of samples significantly affected the dynamic modulus of cement-lime masonry mortars. Differently from concrete, the minimum wave path length of 10 cm was not enough to disregard size and shape effects on the ultrasonic pulse velocity measured in mortars. Static modulus results of small and large cylinders were different due to the higher concentration of cement paste close to the lateral surface of the reduced specimens. The results provided important information for characterization and technological control of cement-lime masonry mortars.