Effect of Heat‐Treatment on the Constitution and Mechanical Properties of Some Hydrated Aluminous Cements

The compound compositions of four aluminous cements were determined on anhydrous as well as hydrated specimens which had been heat‐treated at temperatures between room temperature and 1400° C. Phases were identified by X‐ray diffraction and differential thermal analysis. Specimens were also tested for transverse strength, dynamic modulus of elasticity, and thermal length change. A study of the dehydration characteristics of CaO ‐ Al 2 O 8 ‐ 10H 2 O 3 3CaO.Al 2 O 3 . 6H 2 O, and Al 2 O 3 . 3H 2 O was included. The data indicated that CaO. Al 2 O 3 10H 2 O was the primary crystalline hydrate formed in the cements at room temperature. At 50° C., 3 CaO Al 2 O 3 ‐6H 2 O and Al 2 O 3 . 3H 2 O were formed as by‐products of the dehydration of CaO.Al 2 O 3 .10H 2 O. When heated alone in an open system, CaO.Al 2 O 3 .10H 2 O did not convert to 3CaO. Al 2 O 3 . 6H 2 O and A1 2 O 3 . 3H 2 O. A correlation between the mechanical properties and compound compositions was noted.