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 CO 2 emission is important because CO 2 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.

Characteristics for Improvement of Compressive Strength of Geopolymers Made of Mixed Binders

“…The compressive strengths of geopolymers q u is generally considered as a function of w (= weight ratio of activator to binder) and η (= weight ratio of NaOH to Sodium silicate). In this research, according to Koumoto [1], the w opt , which is the optimum value of w yielding the ultimate compressive strength q umax , becomes a constant value of w = 0.4. Geopolymer samples were made for variable η value with a value of w = 0.4.…”

“…More than 60 million ton of industrial by-products such as fly ash, steel slags and garbage melting furnace slags are generated every year in Japan [1]. Geopolymers are composite hard materials made by mixing binders, such as fly ash and slags, and activators, such as NaOH and sodium silicate [2].…”

“…Koumoto [1] has found the ground blast furnace slag to be the binder that yielded the highest *Address correspondence to this author at the Prof. Emeritus of Saga University, Saga, Japan; Tel/Fax: 0952-30-5868; E-mail: koumotot@gmail.com compressive strength geopolymer among various kind of binders such as fly ash, ground stainless steelmaking slag, and garbage melting furnace slags.…”

“…Note: Reihoku and Karaita= Fly ash; Koro= ground blast furnace slag; Stainless= ground stainless steel-making slag; Kazusa= ground garbage melting furnace slag. *: data from Koumoto[1].…”

Environmentally Friendly Geopolymer Building Material: Production, Determination of Physical-Mechanical-Radiation Absorption Properties and Mathematical Model Approach

“…The interest towards the improvement of novel technologies for the production of higher potential geopolymer-based products has gradually increased (Koumoto 2019;Djobo et al 2017). Geopolymeric materials are alluring since they can help to attain outstanding mechanical properties and durability (Kurtoğlu et al 2018;Huseien et al 2017).…”