MORTAR

in military science, short-range artillery piece with a short barrel and low muzzle velocity, firing an explosive projectile in a high-arched trajectory. Large types were used against fortifications and in siege operations from medieval times through World War I. Since 1915, small, portable models have become standard infantry weapons, especially for trench or mountain warfare. Medium mortars, with a calibre of 7090 mm (about 34 inches), a range up to 4,000 m (about 2.5 miles), and a bomb weight of up to 5 kg (11 pounds), are now favoured. in technology, material used in building construction to bond brick, stone, tile, or concrete blocks into a structure. Mortar consists of inert siliceous (sandy) material mixed with cement and water in such proportions that the resulting substance will be sufficiently plastic to enable ready application with the mason's trowel and to flow slightly but not collapse under the weight of the masonry units. Slaked lime is often added to promote smoothness, and sometimes colouring agents are also added. Cement is the most costly ingredient and is held to the minimum consistent with desired strength and watertightness. Mortar hardens into a stonelike mass and, properly applied, distributes the load of the structure uniformly over the bonding surfaces and provides a weathertight joint.