###### Abstract  
In this study, we compare the behavior of confined compression-tested concrete test pieces and short concrete beams subjected to three-point flexural strength testing when they are reinforced with high-modulus, high-strength carbon fibers reinforced polymers (CFRP). The fabrics used have roughly the same mechanical capacity but very different rigidities. As such, the results make it possible to obtain the influence of the rigidity of the CFRP on the structural behavior of the elements tested. The results obtained show that the type of fabric used does not cause significant differences in the values of tension of rupture and the form of rupture of the test pieces subjected to compression and flexural strength testing, which suggests that the variable which determines the mechanical response of the elements which have been reinforced and subjected to these kinds of demands is the mechanical capacity of the reinforcement, not its rigidity. concrete; reinforcements; CFRP; Young's modulus Article  
Influence of the Modulus of Elasticity of CFRPs on the Compressive Behavior of Confined Compressive Behavior of Conf  
properties. Specifically, the application of temperature increases during the final heat treatment--graphitization--produces significant increases in the material's modulus of elasticity whilst slightly reducing its tensile strength [8; 9; 10]. As such, it is possible to find high-strength (HR) carbon fibers on the market which have longitudinal modulus of elasticity values of 215-235 GPa and breaking strains of 3500-4800 MPa, as well as high-modulus-of-elasticity (HM) fibers which have longitudinal modulus of elasticity values of 350-500 GPa and breaking strains of 2500-3100 MPa [11]. The reinforcement of concrete beams using FRP is an established technique both in terms of practical implementations and at a research level. The increase in flexural strength was assessed, obtaining results of as much as 160%, when the FRP was attached to the exterior of the area under tensile stress of these beams [12; 13; 14]. Excellent results were also obtained when the beams underwent shear [15; 16; 17; 18; 19; 20] and pure torsional reinforcement [21]. The experiments carried out have served to develop a significant body of rules and regulations [22; 23; 24; 25; 26]. Another relatively unknown aspect is the behavior of this type of reinforcement in short beams; it is not possible to apply the general theory of beams to their analysis since all regions of the beam are in areas of discontinuity, in which it is not possible to assume that planar sections remain planar after deformation (D regions). This type of region can be examined using a hypothetical truss with articulated joints composed of struts and tensioners connected to the nodes [27; 28]. There are various procedures for increasing the strength of reinforced concrete pillars. Using jacketing, generally made of steel or concrete, the strong section is increased and, consequently, so is the load capacity [29; 30; 31; 32]. The confinement of the concrete results in increased mechanical capacity and ductility of the existing concrete. The confinement of concrete can be achieved in various ways. The incorporation of external metallic tubes and filling the existing space between the pillar and the tube with high-modulus-of-elasticity concretes has been used for decades, and the technique continues to generate researchers' interest up to the present day [33; 34; 35; 36]. The initial applications of the FRP-confinement technique in reinforced concrete (RC) columns took place in Japan in the 1980s [37; 38]. However, the use of FRPs in Japan suddenly increased in 1995 following the earthquake in Hyogoken Nanbu [39]. Despite being a more recent technique, there are plenty of practical applications and laboratory projects which make it possible to endorse the suitability of the procedure.