11 - Calcined clay as hydraulic binder substitution

Abstract

Concrete, being the dominant construction material, requires cement to bind the various mix constituents. Cement manufacture consists of quarrying, processing, and calcining at 1450°C, thereby high energy input and carbon dioxide emission. To reduce energy consumption, researchers and practitioners have been searching for alternatives to cement. Partial substitution of cement with pozzolanic materials or industrial products is a viable option. This chapter is concerned with the use of calcined clay in cementitious system. It covers the various clay-based materials that can be used for the production of calcined clay and the calcining temperature. This is followed by the fresh properties of cementitious systems containing calcined clay, including consistency, workability, and setting times. The mechanical and durability properties of concrete and mortar containing calcined clay and other additions (e.g. limestone) are covered. These include compressive, splitting and flexural strength, elastic and dynamic modulus, shrinkage, absorption, porosity, pore structure, permeability, chloride ingress, carbonation, sulfate resistance, abrasion and skid resistance, and fire resistance. The environmental and economic aspects, highlighting the benefits of using calcined clay as partial replacement of cement, are briefly stated. The conclusions and recommendations are the subjects of the last part of the chapter.