Concrete is a construction material made from cement, water, and aggregates (sand and gravel) that hardens into a durable, stone-like substance. It is one of the most widely used building materials in the world, employed for foundations, roads, sidewalks, bridges, buildings, and infrastructure. Concrete's advantages include strength, durability, fire resistance, and moldability into various shapes. Municipal infrastructure relies heavily on concrete for water and sewer pipes, culverts, retaining walls, and public buildings. Concrete production (particularly cement manufacturing) is a significant source of carbon dioxide emissions, prompting research into lower-carbon concrete alternatives. Concrete maintenance includes sealing, crack repair, and eventual replacement.