Binders for Durable and Sustainable Concrete

Abstract

Modern hydraulic binders can be used effectively with Portland cement and supplementary cementitious materials to produce durable concrete. They also provide a means of recycling by-products from other industries and of decreasing the emission of greenhouse gases. The first binders were discovered in ancient times when it was observed that new pozzolans mixed with lime could harden under water; and in the middle of the nineteen century the first artificial hydraulic binder, Portland cement, was discovered. By modifying the four basic oxides in the limestone and clay mix used in the production of Portland cement it is possible to modify significantly the practical properties of the clinker, and consequently the performance of the fresh and hardened concrete in which it is used. Chemical admixtures can be used to disperse cement particles without the use of extra water, and so make concrete which is highly resistant to penetration by aggressive agents and of high durability and strength. Supplementary cementitious materials or fillers can be mixed with Portland cement to produce modern hydraulic binders and improve the ecological performance of concrete. The hydration process of a modern hydraulic binder is becoming quite complex because it involves the chemical reactivity of Portland cement clinker, of supplementary cementitious materials and of different types of admixtures. This has already resulted in great technological achievements such as high-performance concrete, self leveling concrete, confined concrete, high-performance roller compacted concrete, fiber reinforced concrete, and reactive powder concrete.