Concrete is a mixture of Portland cement and aggregate that hardens into a strong and durable building material. It is used in a range of applications, from setting posts and pouring foundations, to erecting skyscrapers, highways, bridges, and dams. The cement binds the aggregate, and the aggregate provides structure and reinforcement to the concrete, which helps to prevent cracking. The ratio for dry concrete mix is typically 4 parts aggregate, 2 parts sand, and 1 part cement. Various types of concrete mix are available with different ratios for specific purposes, such as faster setting or higher strength. Concrete also continues to get stronger as it ages, making it a reliable building material for permanent installations.