Concrete and Cement

Mariano Velez

Abstract Inorganic concretes are reviewed, emphasizing two major areas: construc­tion concretes and high temperature (refractory) concretes. Although such materials are intended for completely different applications and markets, they have in common that they are made from inorganic ceramic oxides and both materials are used for structural purposes. Current applications and research topics representing new chal­lenges are summarized.

1 Introduction

Concrete usually indicates a construction material made from Portland cement, aggregates (for instance, gravel and sand), water, and additives to improve mixing or specific properties of the final material. Refractory concretes (monolithic refractories) refer to high-temperature materials for the manufacture of shaped refractories. Most concrete refractories are based on calcium aluminates, although some applications require the use of other high-temperature ceramic materials, such as magnesium oxide. The distinguishable feature of these concretes is that the method of preparation does not involve forming or firing at the manufacturing plant as in the fabrication of refractory bricks. This compilation includes only concretes for construction and refractory applications.

Cement is a binder that sets and hardens by itself or binds other materials together. The most widely known application of cements is in construction; a second one is the area of “bone cements.” Cements used in construction are characterized as hydraulic or nonhydraulic and mostly for the production of mortars and concrete. Hydraulic cements set and harden after combining with water. Most construction cements are hydraulic and based on Portland cement, which consists of calcium silicates (at least 2/3 by weight). Nonhydraulic cements include the use of nonhy­draulic materials such as lime and gypsum plasters. Bone cements and bone cement composites refer to compounds that have a polymer matrix with a dis­persed phase of particles. For instance, polymethylmethacrylate (PMMA) is reinforced with barium sulphate crystals (for radio-opacity) or with hydroxyapatite

J. F. Shackelford and R. H. Doremus (eds.), Ceramic and Glass Materials: 135

Structure, Properties and Processing.

© Springer 2008

to form a bioactive cement. These composites are currently used in orthopaedics for bone trauma repair.