## 1 Introduction  
The stress-strain parameters in concrete allow us to determine both the modulus of elasticity and the compressive strength. The modulus of elasticity test is generally carried out through the American Society for Testing and Materials (ASTM C469) and in Colombia from the Colombian technical standard (NTC 4205); the compression resistance evaluation is carried out by the ASTM C49 and NTC 673 standards, respectively. The modulus of elasticity \(\mathrm{E_{c}}\) of concrete, together with compressive strength, are the most commonly used concrete properties for the design of buildings and civil structures. Over time, it was decided to express stress-strain parameters as a function of these two elements. The ability to withstand loads is made possible by the concrete resistance \(f_{c}\), and the compatibility of displacements and deformations is achieved by incorporating the \(\mathrm{E_{c}}\) modulus, which is responsible for rigidity. On both parameters, there are a large number of variables that significantly affect their values, and they are both related to the concrete components and extended to the testing mechanisms. Some of them have a greater or lesser influence on the compressive stress, other factors have considerable experimental development, some have only been explained by numerical analysis, and finally, some have not yet been addressed by scientific literature. The modulus of elasticity \(\mathrm{E_{c}}\) and the compressive strength \(f_{c}\), are influenced by coarse aggregate, mortar paste, the interfacial transition zone (ITZ), and test parameters [1; 2]. It is logical to expect that since the coarse aggregate represents, on average, up to 50% of the volume of the concrete, it has an important influence on the mechanical and elastic characteristics of the concrete [3]. The modulus of elasticity of concrete is strongly influenced by the modulus of elasticity of the coarse aggregate [4; 5; 6; 7; 8]. However, the maximum size of the aggregate has a much more marked degree of affection in both parameters [9; 10; 11; 12; 13; 14]. The effects of the test parameters can be summarized in the influence of the geometry of the specimen that is primarily tested on the compression stress [15; 16; 17; 18]. The affection of the types of ends used for the test, both in the modulus of elasticity and in compression stress, can have a small to appreciable connotation [19; 20], effects that can also be noted differently with the types of mechanisms with which they are applied to perform the test [18; 21; 22]. All these documented affectations are addressed and valued when formulating the computational model as variables that depend on the material and the test method to which the complications of the model are added, which, in this case, is developed in the Abaqus software of finite elements. However, there are characteristics required in the formulation of the model for its operation that have an inference on the level of accuracy of the results. Complex models are expected to require a more precise definition of the mesh size and element geometry, which, in turn, is reflected in the computational cost [23] of the model used. The search for an optimal solution that concerns the size of the mesh has been required in several investigations of the use of concrete in current engineering [24; 25]. However, it is possible that the optimal value sought is not available, due to the restriction in the computational economy [26], and in that sense, it is not possible, for reasons of computational costs, to achieve a mesh level in which the error obtained can be considered irrelevant. However, it is possible to establish a relationship between the different results and their minimum mesh size [27]. Different mesh sizes have been used in finite element modeling for concrete slabs subjected to impact, explosion, and fire [28; 29], as well as in the analysis of solid and hollow columns under the effects of eccentric loads and compression [30].