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8

Supplementary

Cementing Materials

and Other Additions

1.0 INTRODUCTION

Chemical admixtures such as accelerators, retarders, water reduc-
ers, and superplasticizers are generally water soluble and are added in small
amounts. They significantly affect the properties of concrete in the fresh
and hardened states through physico-chemical and surface interactions. In
contrast to chemical admixtures, materials such as fly ash, silica fume, blast
furnace slag, natural pozzolans, and others are added in substantial amounts
to concrete. Most of them react significantly with the components of the
cement paste yielding higher strengths and better durability characteristics.
They are used as cement replacement materials. Some of them also possess
self-cementitious properties. Utilization of these materials confers several
benefits such as energy savings, reduction of the heat of hydration,
conservation of resources, environmental protection, and improved dura-
bility to various types of chemical attack.
These materials are known by various names. The European
[1]
concrete standards refer to them as additions. The ASTM classifies
them as mineral admixtures. In the literature, they are also described as
[2]
supplementary cementing materials, cement replacement materials, or

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