Experiences with the use of alkali free accelerators in Asia

Abstract

Alkali Free Accelerators (AFA) were developed for the sprayed concrete market in Europe during the early nineties and have gained a reputation as the product of choice for high performance durable sprayed concrete for use as rock support and permanent sprayed lining. This paper examines the development of sprayed concrete from the early use of the dry process with caustic, aluminate based liquids and powders in the eighties, to today's state of the art application using the wet process, AFA, admixtures, fibres and high output robotic application. In certain Asian countries, there is still a tendency toward the continued use of caustic aluminate accelerators. However, during the last 5 years, the use of AFA has become more prevalent, especially in the mature markets of Asia. In recognition of this trend in Asia for continued technology transfer toward AFA, a performance comparison is presented between caustic based liquid accelerators and AFA liquid accelerators with reference to actual civil and mining projects featuring case studies from around the Asian region. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.