Modeling the substitution of natural materials with industrial byproducts in green roofs using life cycle assessments

2019

Sustainability

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The results of life-cycle assessments (LCAs) of concrete are highly dependent on the concrete design method. In this study, LCAs were conducted to evaluate the environmental impacts of the replacement of sand with furnace bottom-ash (FBA) in concrete. In the FBA-based concretes, sand was replaced with FBA at proportions of 0, 30, 50, 70, and 100 wt%. Two design methods were studied: (i) concrete with fixed slump ranges of 0-10 mm (CON-fix-SLUMP-0-10) and 30-60 mm (CON-fix-SLUMP-30-60); and (ii) concrete with fixed water/cement (W/C) ratios of 0.45 (CON-fix-W/C-0.45) and 0.55 (CON-fix-W/C-0.55). The ReCiPe2016 midpoint and single-score (six methodological options) methods were used to compare the environmental damage caused by the FBA-based concretes. A two-stage nested (hierarchical) analysis of variance (ANOVA) was used to simultaneously evaluate the results of six ReCiPe2016 methodologies. The ReCiPe2016 results indicate that replacing sand with FBA decreased the environmental impact of the concretes with fixed slump ranges and increased the environmental impact of the concretes with fixed W/C ratios. Therefore, using FBA as a partial sand replacement in concrete production is of debatable utility, as its impact highly depends on the concrete design method used.Sustainability 2019, 11, 4083 2 of 20 several industrial byproducts, such as FA, FBA, copper slag (CS), and quarry dust powder (QDP) [7][8][9]. Chowdhury et al. [7] studied the full replacement of sand with FA and FBA in road construction, and reported mixed results: climate change (e.g., CO 2 emissions) and environmental acidification were found to be lower for the byproducts, whereas the formation of particulate matter was found to be lower for the sand. Kua [8] performed a life-cycle assessment (LCA) of high-performance concrete in which sand had been partially (10 vol%) replaced with CS, and reported an increased climate change impact (e.g., increased CO 2 emissions) compared to that of conventional concrete. Lim et al. [9] studied the replacement of a high percentage of sand with QDP in lightweight foamed concrete, and reported a decrease in CO 2 emissions of up to 10%. This highlights that the effect of the partial or full substitution of sand in the production of concrete is not fully understood and requires additional research.Among all the possible industrial byproducts, the conversion of waste from coal-fired electricity production into an environmentally friendly byproduct for the production of concrete is a pressing issue for environmentally sustainable development in many countries [2]. For example, Zhang and Poon [10] considered the use of FBA, a waste byproduct from coal-fired electricity production, as an alternative to natural fine aggregates in byproduct-based concrete production to improve the concrete's environmental impact.The problem of producing concrete with a low environmental impact is also important for Israel. Concrete is a major building material in Israel [11], and furthermore, according to the Israel Electric Corporation Lt...

Section: Discussionmentioning

confidence: 99%

“…The single-score method was used to evaluate the following six methodological options: I/A, H/A, E/A, I/I, H/H, and E/E. A two-stage nested (hierarchical) analysis of variance (ANOVA) was used to simultaneously evaluate the results of the six ReCiPe2016 methodological options [28].…”

Section: The Recipe2016 Life-cycle Impact Assessment (Lcia) Methodsmentioning

confidence: 99%

The Effect of Different Concrete Designs on the Life-Cycle Assessment of the Environmental Impacts of Concretes Containing Furnace Bottom-Ash Instead of Sand

2019

Sustainability

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“…However, Huijbregts et al [26] stated that "the time horizon for the third scenario [E] was not always infinite, as not all the environmental models provided sufficient information to model steady-state conditions." These three scenario analyses (perspectives), I, H, and E, can be presented through the ReCiPe2016 midpoint and single-score methods [27]. In addition, the ReCiPe2016 single-score method includes two types of weighting procedures: Average and particular weighting sets.…”

Section: Recipe2016: a Life-cycle Impact Assessment (Lcia) Methodsmentioning

confidence: 99%

“…Six methodological options of the ReCiPe2016 single score method in combination with a two-stage nested (hierarchical) analysis of variance (ANOVA). The two-stage nested ANOVA was used to simultaneously evaluate the results of the six ReCiPe2016 single score methodological options [27].…”

mentioning

confidence: 99%

Life-Cycle Assessment of the Substitution of Sand with Coal Bottom Ash in Concrete: Two Concrete Design Methods

2019

Applied Sciences

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Life-cycle assessments (LCAs) were conducted to evaluate the replacement of sand with coal bottom ash (CBA) in concrete. CBA is a byproduct of coal-fueled electricity production. Sand was replaced with CBA at proportions of 0, 25, 50, 75, and 100 wt.%, and the resultant concretes were denoted as CBA0, CBA25, CBA50, CBA75, and CBA100, respectively. Two concrete mixture design methods (that resulted in different component qualities of concrete mixtures) were used: (i) Mixture with a fixed slump (MIX-fixed-SLUMP) and (ii) mixture with a fixed water/cement ratio (MIX-fixed-W/C). The ReCiPe2016 midpoint and single score (six methodological options) methods were followed to compare the environmental damage caused by the CBA-based concretes. The ReCiPe2016 results showed that replacing sand with CBA was environmentally (i) beneficial with the MIX-fixed-SLUMP design and (ii) harmful with the MIX-fixed-W/C design. Therefore, using CBA as a partial sand replacement in concrete production is a controversial issue as it highly depends on the concrete mixture design method.

“…The small contribution of sand to the total environmental evaluation of concrete makes this issue very sensitive to different factors related to concrete design. For example, Pushkar [8] studied the influence of the concrete design method (i.e., the fixed slump or fixed water/cement (W/C) ratio methods) on the LCAs of byproduct-based concretes in which sand had been substituted with BA in the amounts of 0, 30, 50, 70, and 100 wt % and reported a decreased environmental impact of the concretes with fixed slump ranges and an increased environmental impact of the concretes with fixed W/C ratios.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Additional Byproducts on the Environmental Impact of the Production Stage of Concretes Containing Bottom Ash Instead of Sand

2019

Sustainability

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This study aims to assess whether using byproducts as additional binders can reduce the environmental damage of concretes that already contain bottom ash instead of sand. In particular, two concretes in which sand had been replaced by coal bottom ash at varying percentages (from 0 to 100 wt %) were evaluated in which (i) silica fume was an additional binder, and (ii) silica fume and blast furnace slag were additional binders. Consequential life cycle assessment was applied to environmentally evaluate the effect from the production stage of these byproducts. We used the ReCiPe2016 midpoint hierarchist and single-score (six methodologies) methods. A two-stage nested mixed analysis of variance was used to simultaneously evaluate the results of six ReCiPe2016 methodologies. The ReCiPe2016 midpoint hierarchist results indicate that using additional binders in both bottom ash-based concretes decreases global warming potential, terrestrial ecotoxicity, water consumption, and especially, fossil resource scarcity environmental impacts. The bottom ash-based concrete with silica fume and blast furnace slag as additional binders shows more environmental benefits than the bottom ash-based concrete with only silica fume. The ReCiPe2016 single-score method results indicate that the bottom ash-based alternatives with 40–100 wt % (with silica fume as an additional binder) and 75–100 wt % (with silica fume and blast furnace slag as additional binders) of sand replacement seem to cause the least environmental damage.