Abstract
This study focuses on characterisation of side streams including biomass fly ash, biomass bottom ash, coal fly ash, green liquor dregs, limestone mine tailings, and electric arc furnace steel slag from different industrial locations in Finland. It was found that the fly ash samples contained the highest Al2O3 and SiO2 concentrations, a large number of spherical particles of small sizes and high specific surface areas. Fly ashes and steel slag were observed to contain higher amounts of amorphous phases compared to the other side streams. The high loss on ignition value of the coal fly ash and green liquor dregs was found to exceed the limitations for their application in geopolymer composites. Despite their relatively high concentrations in ashes and steel slag, the leaching tests have shown that no hazardous metal leached out from the streams. Finally, test specimens of geopolymer composites (GP2) were prepared by the application of biomass fly ash, bottom ash, and limestone mine tailings without any pre-treatment process, in addition to the ordinary Portland cement-(R) and metakaolin-based geopolymer composites (GP1). The measured compressive (14.1 MPa) and flexural strength (3.5 MPa) of GP2 suggest that it could be used in concrete kerbs and paving flags. The data has also shown that over 500% of the compressive strength was developed between 7 and 28 days in GP2, whereas in the case of reference concrete (R) and the metakaolin-based geopolymer composite (GP1) it was developed in the first 7 days.
Highlights
According to the 2030 climate and energy framework adopted by the European Council in October 2014, the target for 2030 is to reduce the GHG emissions by 40%, to increase the share of renewable energy to at least 32%, and to improve the energy efficiency to 32.5% [1]
As part of the attempts to address issues related to waste management and greenhouse gas emissions in the construction industry, numerous studies have been conducted that consider the use of geopolymer composites as an alternative to ordinary Portland cement (OPC) [3,4,5]
This paper focuses on characterisation of several important industrial side streams, namely, biomass fly ash, coal fly ash, biomass bottom ash, green liquor dregs, limestone mine tailings and electric arc furnace
Summary
According to the 2030 climate and energy framework adopted by the European Council in October 2014, the target for 2030 is to reduce the GHG (greenhouse gas) emissions by 40% (from 1990 levels), to increase the share of renewable energy to at least 32%, and to improve the energy efficiency to 32.5% [1]. Continuous efforts are required; for instance, the cement industry, on a global scale, is responsible for 8% of world’s CO2 emissions despite improvements in terms of energy efficiency [2]. As part of the attempts to address issues related to waste management and greenhouse gas emissions in the construction industry, numerous studies have been conducted that consider the use of geopolymer composites as an alternative to ordinary Portland cement (OPC) [3,4,5]. Geopolymer composites are inorganic materials that have been produced by polymerisation of materials with high aluminosilicate contents. The polymerisation is a result of the fast chemical reaction of silica and aluminosilicate under strong alkaline conditions with, e.g., NaOH, Ca(OH), Na2O, LiOH, and Na2SiO3 [6]. Different polymeric chains may be generated, such as poly(sialate)(-Si-O-Al-O-)n, poly(sialate-siloxo) (-Si-O-Al-O-Si-O-)n, poly(sialate-disiloxo)(-Si-O-Al-O-Si-O-Si-O-)n, and poly(sialate-multisiloxo), depending on the reaction conditions [7]
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