Concrete and asphalt are strong, durable building materials comprised of binders and aggregates, such as rock, sand, or gravel. Concrete and asphalt are initially mixed in a pliable, semi-viscous state prior to application. After setting, they harden into a durable solid state, making them ideal for new construction, such as sidewalks, driveways, and roads, or in maintenance and repair applications such as patching and tuckpointing. Concrete is a mixture of Portland cement and aggregate that hardens into a strong and durable building material commonly used to set posts and pour foundations. Mortar is used to build and repair brick or block walls or to fill gaps and cracks in concrete and masonry walls. It has lower strength, retains more water, and has a higher air content than concrete.