Architecture：Non-Portland Rapid Setting Cements.pdfVIP

403 10 Non-Portland Rapid Setting Cements 1.0 INTRODUCTION Cements other than portland cement, either alone or in combination with portland cement, are often more suitable for specific applications. Requirements of construction or environmental conditions can place con- straints on conventional practice. Rapid setting, high early strength, and durability specifications often dictate the choice of an alternate cement system. The application of thermal analysis to selected rapid setting cements is presented in this chapter. These include the following systems: calcium aluminate cements (high alumina cement, Jet Set or regulated-set cement) and related pure mineral systems; magnesium oxychloride and oxysulfate cement; and magnesia-phosphate cements, precursors to the formation of hydroxyapatite. Cement systems containing supplementary materials and other additions are discussed in Ch. 8 of this book. 403 404 Chapter 10 - Non-Portland Rapid Setting Cements 2.0 CALCIUM ALUMINATE CEMENTS 2.1 Basic Reactions Calcium aluminate cements (CAC) have a wide range of alumina content (38 to 90%). The chemistry and principle cement-water reactions for high alumina cement—a widely used non-portland cement—are de- scribed in detail in Ch. 9. The primary binding phase is calcium monoaluminate (CaAl2O4 or CA). Refractory cements contain higher alumina contents (70 to 90%). In CAC, the CA reacts with water to form a series of calcium aluminate hydrates. These include CAH , C AH , C AH , and AH (an 10 2 8 3 6 3 amorphous phase). The metastable hydrates, CAH and C AH , convert to 10