Alkali-activated fly ash/slag cements: Strength behaviour and hydration products
TL;DR: The activation of fly ash/slag pastes with NaOH solutions has been studied in this paper, where the authors established the equations of the models describing the mechanical behaviour of these pastes as a function of the factors and levels considered.
About: This article is published in Cement and Concrete Research.The article was published on 2000-10-01. It has received 745 citations till now. The article focuses on the topics: Fly ash & Calcium silicate.
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TL;DR: In this paper, the authors present the work carried out on the chemical reaction, the source materials, and the factor affecting geopolymerization, and demonstrate that certain mix compositions and reaction conditions such as Al2O3/SiO2, alkali concentration, curing temperature with curing time, water/solid ratio and pH significantly influences the formation and properties of a geopolymers.
Abstract: Geopolymerization is a developing field of research for utilizing solid waste and by-products. It provides a mature and cost-effective solution to many problems where hazardous residue has to be treated and stored under critical environmental conditions. Geopolymer involves the silicates and aluminates of by-products to undergo process of geopolymerization. It is environmentally friendly and need moderate energy to produce. This review presents the work carried out on the chemical reaction, the source materials, and the factor affecting geopolymerization. Literature demonstrates that certain mix compositions and reaction conditions such as Al2O3/SiO2, alkali concentration, curing temperature with curing time, water/solid ratio and pH significantly influences the formation and properties of a geopolymer. It is utilized to manufacture precast structures and non-structural elements, concrete pavements, concrete products and immobilization of toxic metal bearing waste that are resistant to heat and aggressive environment. Geopolymers gain 70% of the final strength in first 3–4 h of curing.
1,078 citations
TL;DR: In this paper, the synthesis of alkali-activated binders from blast furnace slag, calcined clay (metakaolin), and fly ash is discussed, including analysis of the chemical reaction mechanisms and binder phase assemblages that control the early-age and hardened properties of these materials.
Abstract: 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...
862 citations
TL;DR: In this paper, a fly ash-based geopolymer concrete for curing in ambient condition can be proportioned for desirable workability, setting time, and compressive strength using ground granulated blast-furnace slag (GGBFS) as a small part of the binder.
855 citations
TL;DR: Alkali-activated binders have emerged as an alternative to OPC binders, which seems to have superior durability and environmental impact as mentioned in this paper, and the proper terminology to designate these new binders will be discussed.
800 citations
TL;DR: In this paper, ground fly ash (GFA), with a median particle size of 10.5μm, was used as source material for making geopolymers cured at room temperature, and compressive strength tests and microstructure observations using SEM, EDX, XRD and FTIR were performed.
755 citations
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TL;DR: In this paper, the mechanism of activation of fly ash with highly alkaline solutions is described, and the product of the reaction is an amorphous aluminosilicate gel having a structure similar to that of zeolitic precursors.
1,779 citations
TL;DR: Alkali-activated cements as discussed by the authors are those with compositions falling in the Me2O-MeO-me2O3-SiO2-H2O system, and their history of development and present status are reviewed.
549 citations
TL;DR: In this paper, the joint influence of a series of factors (specific surface of slag, curing temperature, activator concentration, and the nature of the alkaline activator) on the development of mechanical strengths in alkaline-activated slag cement mortars was investigated.
520 citations
TL;DR: In this paper, the authors summarized the advantageous and disadvantageous properties of alkali-activated slag cement and concrete by reviewing previously published work in English, Russian and Chinese, and discussed practical problems and theoretical questions concerning alkaline activation.
Abstract: 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.
395 citations
TL;DR: In this paper, the authors examined the early hydration of alkali-slag cements activated by different sodium compounds, such as NaOH, NaCO3, Na2SiO3 and NaF, at 25 and 50 °C.
330 citations