An experimental study was carried out to evaluate the Effects of using sea sand partially replacement as fine aggregate of concrete on mechanical properties has been presented in this paper. The sand is partially replaced with sea sand with the dosage of 20 % ,30 % and 40% of river sand. The sea sand used was untreated which enhanced the mechanical properties of concrete compare to ordinary concrete. The workability was maintained with addition of superplasticizer, the water cement ratio adopted was 0.48 for all mix of concrete. Based on the results the compressive strength, split tensile strength, flexural strength, ultra pulse velocity and rebound hammer test were performed and results were obtained optimum at 30 % dosage of Sea sand as 9.94 %, 22.66%, 21.34%, 11.81%, and 12.81% respectively.