Mortar and concrete made with Portland cement have been popular construction materials for housing and infrastructure for over 170 years. At first glance their longevity and popularity seems obvious. These materials consist of inexpensive powders that are mixed with water, fillers, and aggregates to form a fluid mass that can be easily shaped and molded and, thereafter, hardens spontaneously under normal environmental conditions. However, cement, mortar, and concrete have some well-known disadvantages such as delayed hardening, low tensile strength, large drying shrinkage and low chemical resistance. To reduce these disadvantages, a full industry has blossomed around mortar and concrete additives.
Common additives for mortar and concrete consist of chemicals, minerals (fly ash, slag, etc.), and particulates (principally organic fiber). Chemical additives will be the primary focus of this article. They consist of organic and inorganic materials that are added in very small amounts to the mortar or concrete mixture before or during mixing with water.