"石膏胶凝材料" can be translated as "gypsum binding material" or "gypsum cementitious material".
"Gypsum" refers to the mineral or the hydrated calcium sulfate that is the main component of such materials.
"Binding material" or "cementitious material" describes the property of these substances to bind other materials together, forming a solid mass when mixed with water and allowed to harden.
Both translations are commonly used in the field of materials science and engineering.