This document discusses different types of admixtures used in concrete. It outlines four main categories of admixtures: air-entraining agents, plasticizers, mineral admixtures, and specialty admixtures. Air-entraining agents create tiny air bubbles in concrete to increase workability and freeze-thaw resistance. Plasticizers enhance workability and strength and include lignosulfonates, hydroxycarboxylic acids, and polymers. Mineral admixtures like fly ash and slag cement improve concrete properties when reacted with calcium hydroxide. Specialty admixtures provide various benefits such as waterproofing, corrosion inhibition, and pumping aid.