Environmental sustainability of geopolymer composites
Abdulkareem, Mariam (2021-12-03)
Väitöskirja
03.12.2021
Lappeenranta-Lahti University of Technology LUT
Acta Universitatis Lappeenrantaensis
School of Energy Systems
School of Energy Systems, Ympäristötekniikka
Kaikki oikeudet pidätetään.
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-335-739-6
https://urn.fi/URN:ISBN:978-952-335-739-6
Tiivistelmä
Portland cement (PC) production is resource-intensive and contributes 4–8% of global CO2 emissions. The quest for reduced CO2 emissions from PC production has led to the development of geopolymer binders. Geopolymers are produced from aluminosilicate precursors such as coal fly ash and granulated blast furnace slag and are developed from the polycondensation of polymeric aluminosilicates and alkali-silicates, yielding threedimensional polymeric frameworks. This study was conducted to determine the environmental sustainability of geopolymers with respect to PC and PC concrete.
The primary aim of this dissertation is to compare the environmental performance of geopolymer materials to conventional materials and to support decision-making in the development of environmentally sustainable construction materials. To this end, the objectives of this dissertation are as follows: (1) to identify the most important factors contributing to the environmental impact of geopolymers that could be considered in future development, by quantifying the environmental performance of different geopolymer binders and composite mix designs in comparison to PC and PC concrete; (2) to quantify the potential to improve the environmental performance of geopolymers by utilising chemically modified waste-derived alkali-silicates instead of conventional sodium silicate, and (3) to quantify and compare the environmental performance of a product (low-height noise barrier) made from either PC concrete or geopolymer, identify hotspots, and evaluate the impact of product system changes on the performance.
The aim and objectives of this dissertation were met using the life cycle assessment (LCA) methodology which addresses the environmental performance and potential environmental impacts throughout a product’s life cycle. Four LCA studies were conducted in this regard. The LCA studies were progressive, with results from the first two LCA studies providing the basis for the last two LCA studies.
The results obtained from the first two LCA studies reveal that alkali activator (sodium silicate) is the major contributor to the environmental performance of geopolymer mix designs. The best mix design from these analyses has 4% sodium silicate and 50% reduced global warming potential (GWP) when compared to PC concrete, and 61% reduced GWP when compared to steel fibre reinforced PC concrete. Based on the above results, the third LCA study was carried out by substituting chemically modified glass waste and rice husk ash derived alkali-silicate, respectively, with conventional sodium silicate powder and sodium silicate solution which led to 72% and 90% GWP reduction.
These results supported decision-making and guided the development of geopolymer composite mix designs in a project involving LUT university and partners. The environmental performance of these locally developed geopolymer composite mix designs shows the possibility of developing a geopolymer composite from 83% weight- % of industrial waste and by-products and 0.3% weight-% of alkali activator with a 73% GWP reduction when compared to conventional concrete.
This dissertation shows the differences in the environmental performance of geopolymers with different precursors, alkali activators, and system boundaries (cradle-to-gate and cradle-to-grave) and provides insight into how the environmental performance of geopolymers is influenced by these factors. It also enables a better understanding of the development of geopolymer composites as sustainable construction materials and facilitates environmentally sustainable decision-making in this area of study. This supports the often-emphasised view that geopolymer binders can be considered a lowcarbon substitute for PC.
The primary aim of this dissertation is to compare the environmental performance of geopolymer materials to conventional materials and to support decision-making in the development of environmentally sustainable construction materials. To this end, the objectives of this dissertation are as follows: (1) to identify the most important factors contributing to the environmental impact of geopolymers that could be considered in future development, by quantifying the environmental performance of different geopolymer binders and composite mix designs in comparison to PC and PC concrete; (2) to quantify the potential to improve the environmental performance of geopolymers by utilising chemically modified waste-derived alkali-silicates instead of conventional sodium silicate, and (3) to quantify and compare the environmental performance of a product (low-height noise barrier) made from either PC concrete or geopolymer, identify hotspots, and evaluate the impact of product system changes on the performance.
The aim and objectives of this dissertation were met using the life cycle assessment (LCA) methodology which addresses the environmental performance and potential environmental impacts throughout a product’s life cycle. Four LCA studies were conducted in this regard. The LCA studies were progressive, with results from the first two LCA studies providing the basis for the last two LCA studies.
The results obtained from the first two LCA studies reveal that alkali activator (sodium silicate) is the major contributor to the environmental performance of geopolymer mix designs. The best mix design from these analyses has 4% sodium silicate and 50% reduced global warming potential (GWP) when compared to PC concrete, and 61% reduced GWP when compared to steel fibre reinforced PC concrete. Based on the above results, the third LCA study was carried out by substituting chemically modified glass waste and rice husk ash derived alkali-silicate, respectively, with conventional sodium silicate powder and sodium silicate solution which led to 72% and 90% GWP reduction.
These results supported decision-making and guided the development of geopolymer composite mix designs in a project involving LUT university and partners. The environmental performance of these locally developed geopolymer composite mix designs shows the possibility of developing a geopolymer composite from 83% weight- % of industrial waste and by-products and 0.3% weight-% of alkali activator with a 73% GWP reduction when compared to conventional concrete.
This dissertation shows the differences in the environmental performance of geopolymers with different precursors, alkali activators, and system boundaries (cradle-to-gate and cradle-to-grave) and provides insight into how the environmental performance of geopolymers is influenced by these factors. It also enables a better understanding of the development of geopolymer composites as sustainable construction materials and facilitates environmentally sustainable decision-making in this area of study. This supports the often-emphasised view that geopolymer binders can be considered a lowcarbon substitute for PC.
Kokoelmat
- Väitöskirjat [1099]