Production of High Compressive Strength Geopolymers Considering Fly Ash or Slag Chemical Composition

Abstract

More than 60 billion kg (60 million t) of industrial by-products such as fly ash, garbage melting furnace slag, and steel slag are generated every year in Japan. Almost all of them seem to have been effectively used in mixtures with cement according to their chemical and mechanical characteristics in the field of civil work. Fly ash and slags can be used to create geopolymers in a process that emits less carbon dioxide than does the cement-making process. This reduction in CO2 emission is important because CO2 is one of the substances known to contribute to global warming. In the future, further uses of these fly ash and slags must be explored. The chemical mechanism for hardening composite materials by mixing aluminosilicate binders such as fly ash and slags with alkaline activators such as liquid NaOH and sodium silicate is known as a geopolymeric reaction, and the hardened composite material is called geopolymer. Geopolymers are produced by mixing two components of solid binders, such as fly ash, slags, and so on, with liquid activators such as NaOH, KOH, sodium silicate, and so on. Geopolymers have recently been developed to be used as a replacement for portland cement concrete. Research has been done to improve the compressive strength characteristics of both geopolymers and the combination of soft soil and fly ash–based geopolymer. The development of high compressive strength geopolymer using fly ash and slags will strongly contribute to the fields of construction, geotechnical engineering, and architecture. This paper describes the method for production and strength diagnosis of geopolymers considering the chemical composition of fly ash or slags.