Abstract
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.
Highlights
Every year, ten billion tons of concrete are produced in the world [1]
In byproduct-based concrete, cement and/or natural aggregates are replaced with byproducts from other industries, such as fly ash (FA), coal bottom ash (CBA), granulated blast furnace slag (GBFS), quarry dust powder (QDP), and copper slag (CS), in addition to others [2,5]
The first is the reduction in sand and water production, while the second is an increase in the transport load due to the transportation of CBA from the coal-fired power plant to the local concrete batching plant and gravel production
Summary
Ten billion tons of concrete are produced in the world [1]. Conventional concrete production consumes high amounts of cement and aggregates and causes severe environmental damage due to the high greenhouse gas emissions and natural resource depletion [2]. In byproduct-based concrete, cement and/or natural aggregates are replaced with byproducts from other industries, such as fly ash (FA), coal bottom ash (CBA), granulated blast furnace slag (GBFS), quarry dust powder (QDP), and copper slag (CS), in addition to others [2,5]. This problem is faced in Israel due to (i) the prevalence of concrete as a main building material under the current socioeconomic state [6], and (ii) the presence of polluting industries, such as coal-fueled electricity production [7]. The Israeli electric company uses two major sources of fuel, i.e., coal (50%–57%) and natural gas (40%–45%) [7], and coal combustion produces 85%–90% FA and
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