Study on retarding feature and retardation mechanism of various retarding materials on gypsum as a construction material: A review

Extremely rapid setting time of building gypsum severely limits its further processing and application. Gypsum retardation is an indispensable technology that provides a long period of plasticity for gypsum construction. Developing highly efficient gypsum retarders is of great significance for improving gypsum retardation technology. Many progressive achievements in the development of gypsum retarders have been witnessed already over the past 30 years. Herein, various types of gypsum retarders are focused on and the recent research progress on this topic is reviewed in detail. Retarders used for gypsum are mainly divided into three categories: organic acids, alkaline phosphates and proteins, and each retarder is aimed to effectively respond to the purpose of gypsum retardation. Various types of retarders have varying degrees of effect on the setting time, mechanical strength, crystal morphology and other properties of gypsum, which are related to their unique retardation mechanism. Furthermore, the important challenge and issues for the future development of gypsum retarders are also discussed.