Advances in alternative cementitious binders

Alkali-activated materials

The development of new, sustainable, low-CO2 construction materials is essential if the global construction industry is to reduce the environmental footprint of its activities, which is incurred particularly through the production of Portland cement. One type of non-Portland cement that is attracting particular attention is based on alkali-aluminosilicate chemistry, including the class of binders that have become known as geopolymers. These materials offer technical properties comparable to those of Portland cement, but with a much lower CO2 footprint and with the potential for performance advantages over traditional cements in certain niche applications. This review discusses the synthesis of alkali-activated binders from blast furnace slag, calcined clay (metakaolin), and fly ash, including analysis of the chemical reaction mechanisms and binder phase assemblages that control the early-age and hardened properties of these materials, in particular initial setting and long-term durability. Perspectives fo...

Geopolymers and Related Alkali-Activated Materials

Alkali-activated fly ash/slag cements: Strength behaviour and hydration products

Sodium silicate-based, alkali-activated slag mortars: Part I. Strength, hydration and microstructure

This paper summarizes the advantageous and disadvantageous properties of alkali-activated slag cement and concrete by reviewing previously published work in English, Russian and Chinese. Practical problems and theoretical questions are discussed. Topics for future work in this field are suggested. The practical problems mentioned are quick setting, the possibility of alkali—aggregate reaction, and the occurrence of efflorescence, shrinkage, microcracks and strength variation. The theoretical questions discussed concerning alkaline activation include the roles of the alkaline anion and cation, the nature of the hydration products, microstructural development and the setting and hardening mechanisms.

Xin-Cheng Pu

Papers

Alkali-activated slag cement and concrete: a review of properties and problems