Abstract
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.
Highlights
In the concrete industry, a common worldwide approach to reducing pollution is the replacement of cement with byproducts from other industries, such as fly ash (FA), furnace coal bottom-ash (FBA), and ground granulated blast furnace slag (GGBS) [1,2]
The life-cycle assessments (LCAs) of five FBA-based concrete alternatives with 0, 30, 50, 70, and 100 wt% of sand replaced with FBA were evaluated
And 3, the impacts of global warming potential (GWP), terrestrial ecotoxicity, and water consumption were lower in the byproduct-based concretes (FBA50SL0-10, FBA70SL0-10, FBA100SL0-10, FBA50SL30-60, FBA70SL30-60, and FBA100SL30-60 ) compared with the conventional concretes (FBA0SL0-10 and FBA0SL30-60 ). These results indicate that when the sand in the concrete was sequentially replaced with FBA, the resulting decrease in the quantity of sand and water was greater than the increase in the traffic load due to the transportation of FBA from the coal-fired power plant to the local concrete batching plant and the increase in the quantity of coarse aggregates
Summary
A common worldwide approach to reducing pollution is the replacement of cement with byproducts from other industries, such as fly ash (FA), furnace coal bottom-ash (FBA), and ground granulated blast furnace slag (GGBS) [1,2]. Meng et al [4] studied the cost-effectiveness of ultra-high performance concretes (UHPC) with a high volume of cement replaced with Class C fly-ash (FAC), GGBS, and silica fume (SF), and with the complete replacement of quartz sand with conventional concrete sand. They reported that the cost of such mixtures was 4.1–4.5 $/m3 /MPa under standard concrete curing conditions. Saade et al [5] studied the environmental impacts of concretes with 66% of cement replaced with GBFS, and reported an approximate 40–70% decrease in the environmental impacts of the concrete, such as abiotic depletion, acidification, and eutrophication
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