Mortar Admixture is a powdered material that can be used to make mortar, a paste made of sand and water that can be used to build brick or stone walls. Mortar can be made from a variety of materials, but the mortar admixture helps reduce the need for costly, hard-to-find materials. Mortar Admixture is primarily used for mortar mixing, but it can also be used to fill in holes in brick or stone walls or to shore up weak areas.