Abstract

This paper presents a review on fly ash as prime materials used for geopolymer. Due to its advantages of abundant resources, less in cost, great workability and high physical properties, fly ash leads to achieving high mechanical properties. Fly ash is considered as one of the largest generated industrial solid wastes or so-called industrial by-products, around the world particularly in China, India, and USA. The characteristics of fly ash allow it to be a geotechnical material to produce geopolymer cement or concrete as an alternative of ordinary Portland cement. Many efforts are made in this direction to formulate a suitable mix design of fly ash-based geopolymer by focusing on fly ash as the main prime material. The physical properties, chemical compositions, and chemical activation of fly ash are analyzed and evaluated in this review paper. Reference has been made to different ASTM, ACI standards, and other researches work in geopolymer area.

Highlights

  • The production of ordinary Portland cement (OPC) contributes approximately 7% to the total of global greenhouse gas emissions; this is considered as a serious problem for the environment [1, 2]

  • Fly ash is classified as class F if the silica, alumina, and iron oxide content is at least 70% of the total mass and has a limited percentage of calcium oxide (CaO)

  • According to ASTM C188 [25], the specific gravity of fly ash (FA) particles can be determined by the same method that is used for hydraulic cement

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Summary

Introduction

The production of ordinary Portland cement (OPC) contributes approximately 7% to the total of global greenhouse gas emissions; this is considered as a serious problem for the environment [1, 2]. Geopolymer was firstly proposed by Davidovits [3] as an alternative binder to OPC. It is classified as class F fly ash, which will be detailed . FA with a high percentage of silica (SiO2) and alumina (Al2O3) (more than 80%). According to Davidovits [3], geopolymers are classified as binder materials, which could be formed by the activation of aluminosilicate with alkaline solutions. The term “geopolymer” was first introduced by Davidovits and well known as inorganic polymers or alkaline-activated binder material [4]. This review paper evaluates the significant characteristics of FA and its advantages as raw materials in geopolymer cement and concrete

Classification
Physical characteristics
Particle shape and form
Particle-specific gravity
Size and fineness of particle
Chemical and mineralogical composition of FA
Setting time
Physical treatment
Effect of FA on workability and water requirement
The impact of FA on durability of concrete exposed to elevated temperatures
FA requirements for geopolymer
Findings
Conclusion
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