Architecture：Introduction to Non-Portland Cement Binders and Concrete.pdfVIP

355 9 Introduction to Non-Portland Cement Binders and Concrete 1.0 INTRODUCTION Portland cement-based concretes are the most widely used in the construction industry. Non-portland cement-based systems, particularly those that have fast hardening and strength development characteristics, are well suited for special applications, many of these related to the repair of concrete structures. The performance of many non-portland cement-based repair mate- rials is dependent on the chemistry and physics of the system, the properties of the existing concrete, and the environment. Thermal analysis techniques are increasingly being used to investigate the physico-chemical behavior of non-portland cement binders exposed to aggressive environments. This chapter provides a description of the hydration and engineering behavior of special cements including: magnesium oxychloride and oxysulfate cement; calcium aluminate cement; portland-calcium aluminate blended cement; phosphate cement; regulated set cement; and gypsum. 355 356 Chapter 9 - Non-Portland Cement Binders and Concrete 2.0 MAGNESIUM OXYCHLORIDE CEMENT 2.1 Description The first oxychloride cement was reported by Sorel.[1] Magnesium oxychloride cement (MOC), referred to as Sorel cement can be formed by mixing fine particles of calcined magnesite with magnesium chloride solution (specific gravity 1.18– 1.20). Many of its properties are superior to those of portland cement. Most are dependent on the chemical composition and the reactivity of calcined magnesite with magnesium chloride solu- tion.[2] For example, coarse-grained magnesite compressed of grains coated with iron minerals results in reduced strength compared to magnesite consisting of primarily microcrystalline material.