It is known that the vast majority of buildings in Turkey are made out of reinforced concrete (RC). The 1999 Kocaeli and Duzce, the 2010 Elazig, and the 2011 Van earthquakes that occurred in Turkey revealed that the most significant factor in causing damage to buildings, or their collapse, was the use of low quality concretes, i.e., concretes with low strength values, in their construction. This reveals that the load bearing members of these structures should be reinforced against the effects of possible earthquakes. The aim of the present study is to investigate the effect of carbon fiber reinforced polymer (CFRP) usage on the behavior of beams made out of low strength concrete. Within the scope of the study, the results of the experimental and numerical analysis for 14 RC beams, to which CFRP plates were applied on their lower surface, as well as for two reference beams, were presented for the case of collapsing. From the start of the test to the end, load, deflection and deformation data obtained from the beams were collected and then, by the identification of the collapsing mechanism as well as the load-deflection relation, the behavior of the beams was discussed in detail. In the numerical study, moment capacities were obtained for CFRP applied beams with different concrete strength values by using the material properties of the specimens examined in the mechanical test. The results of the numerical analysis were compared with those of the experimental tests, which were found to be consistent with each other.