This document summarizes research on using foundry sand as a partial replacement for natural sand in concrete. It reviews 14 research papers that studied the effects on properties of fresh and hardened concrete like strength, durability and workability. Most studies found that replacing up to 20-30% of natural sand with foundry sand resulted in higher compressive and tensile strengths compared to normal concrete, while workability decreased as replacement increased due to fine particles in foundry sand. Water absorption generally increased with higher replacement. However, all studies concluded that concrete with foundry sand partial replacement can be suitable for structural or nonstructural uses. Further research is needed to study concrete with 100% replacement.