Use of slag (GBFS) generated in charcoal blast furnace as raw material in alkali-activated cement
- PDF / 2,250,783 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 78 Downloads / 203 Views
Use of slag (GBFS) generated in charcoal blast furnace as raw material in alkali‑activated cement E. A. Langaro1 · M. Costa de Moraes2 · I. S. Buth2 · C. Angulski da Luz2 · J. I. Pereira Filho2 · A. Matoski1 Received: 26 July 2019 / Accepted: 24 March 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Alkali-activated cements are low-environmental-impact binders and can be obtained from the alkaline activation of wastes such as slags and fly ashes, and solutions of hydroxides and silicates. In this study, two types of slag, A and B, generated in charcoal and coke blast furnaces, respectively, were activated with NaOH in contents of 4, 5 and 6% to obtain alkali-activated slag (AAS). Samples were submitted to calorimetry and compressive strength tests, and investigative microstructure analysis. The results showed that cement obtained with slag A (AAS_A) presented a much superior performance than AAS_B, which was related to the higher degree of hydration, higher formation of amorphous CSH with a higher incorporation of aluminum ions (C–(A)S–H). For AAS_B, the activator content was not able to improve the compressive strength. Calorimetry measurements showed a small interaction between slag B and the activator. The results contribute to the appreciation of slags generated in charcoal blast furnaces, which may become raw material for low-environmental-impact cements, in this case, AAS. Keywords Alkali-activated slag · Granulated blast-furnace slag · Microstructure · Calcium silicate hydrate (C–S–H)
Introduction The concrete industry contributes around 7% to total global CO2 emissions and approximately 90% of this embodied energy and associated carbon is due to the commonly used Portland cement binder [1]. Relative to other building materials, concrete has a low embodied energy and carbon footprint. However, due to the enormous quantity of concrete used each year, the resulting total embodied energy and carbon footprint is quite large. Alkali-activated cements can only be synthesized from waste without the need for the calcination process. Alkaliactivated cements are usually obtained from slag, fly ash or metakaolin, which are activated by solutions of sodium hydroxide (NaOH), potassium hydroxide (KOH) and silicates. Raw materials rich in SiO2 and Al2O3 form an * C. Angulski da Luz [email protected] 1
Departamento de Engenharia Civil, Universidade Tecnológica Federal do Paraná, Campus Curitiba, Curitiba, PR, Brazil
Departamento de Engenharia Civil, Universidade Tecnológica Federal do Paraná, Campus Pato Branco, Pato Branco, PR 85501970, Brazil
2
amorphous aluminosilicate material as a hydrated compound, while those rich in CaO produce calcium silicate hydrate (C–S–H) [2–5]. In the alkali-activated slag (AAS) obtained from the granulated blast-furnace slag (GBFS), the main hydration product is C–S–H, or C–A–S–H, due to the incorporation of Al2O3 in its structure [6–8]. Hydrotalcite, merwinite, stratlingite and calcium monosulfoaluminate hydrate may also be present as minority phases [9–15]. One o
Data Loading...
