Experimental and numerical evaluation of mortar specimens shape and size influence in compression tests

Abstract

The axial compressive strength of cementitious compounds is an important parameter for classification, quality assessment and material design. The values obtained in tests are influenced due intrinsic properties of the compounds and external factors such specimen size and shape. The present work aims to evaluate experimentally and numerically using finite element method, the specimen shape and dimension influence over results of the mortar axial compressive strength test. The specimen geometry aspects are cubic, 4x4x4cm, column with height/thickness ratio equals two prismatic, 4x4x8cm, beam with height/thickness ratio equals one prismatic also with dimensions 4x4x8cm however tested with horizontal 8cm dimension and 5cm diameter cylindrical with 5cm and 10cm of height. Specimen material are strong and weak mortar. We tested five specimen of every mortar strength one for each geometry therefore ten specimen total at 28 days of age. The cylindrical specimen resulted in lower mechanical strength among all geometry. Between cylindrical ones the results exibited equivalent strength however, among prismatic and cubic ones the strength results diverged. Ones with height/thickness ratio equals one, i.e., cubic and beam, resulted in higher strength then one with height/thickness ratio equals two, named column. Numerical simulations verify these results indicating equally height/thickness ratio equals one geometry with higher strength. This could be happening because in height/thickness ratio equals one geometry the maximum principal stress values (tractions) are lower.