In this study, mechanical properties of a polymer cementitious matrix (PCM) on fly ash, shrinkage reducing agent, and EVA polymer were evaluated and its optimum mixing level was determined to strengthen structures damaged by natural disasters. A total of 19 PCM mixtures were divided into the series I and II to evaluate the effects of fly ash, shrinkage reducing agent, and the amount of EVA polymer, respectively. Results showed that the PCM containing fly ash and shrinkage reducing agent together satisfied the required flow, setting time, compressive strength, and dry shrinkage. However, the bonding strength of 1.0 MPa did not satisfy the requirement. The bonding strength was thus improved by increasing the amount of EVA polymer in series II by 2-8%, resulting in 0.81-1.65 MPa. Therefore, it is found that a mix of 10% of fly ash, 1% of shrinkage reducing agent, and 4% of EVA polymer was determined as the optimum mixing level of the PCM.