Impact resistance, being the ability of a material to resist impact loads without undergoing plastic deforming or failing is one of the fundamental characteristics of concrete. However, failures of bridges, tunnels and dams are increasing now-a-days. Their failures are directly connected to impact loads; violent wind loads in bridges, seismic loads on tunnels and turbulent wave surges in dams. This project attempts to improve impact resistance/strength of concrete by replacing fine aggregate with a suitable replacement material. Cockle seashell species was found to be ideal as it had high calcium content while being relatively stronger than other seashells. Of the different methods tried to grind the Cockle shells into fine aggregate sizes, it was found that machine mill grinding was most efficient. Blended cement with 27% fly-ash was used, to avoid excessive heat of hydration during curing. Four different replacement percentages (by volume) were evaluated; 4%, 8%, 12% and 16%. Numerous specimens were cast and a variety of destructive and Non-Destructive Tests (NDT) were performed. NDTs namely, rebound hammer test and ultrasonic pulse velocity test were conducted on slab specimens that were subjected to mild impact loading. Relatively higher magnitude impact loads were used for destructive weight drop impact testing. The mix with 4% fine aggregate replacement showed increased compressive, tensile and flexural strengths when compared to specimens of the other mixes as well as the control mix. The 4% fine aggregate replaced mix also displayed significantly higher impact resistance during the weight drop test. Furthermore, it maintained greater surface hardness and lesser density of internal cracks during non-destructive testing.