## 1 Introduction  
Every year, 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]. This problem is further exacerbated in areas where natural resources such as sand are becoming scarce, for example, in Singapore [3] and India [4]. Therefore, to reduce the environmental damage caused by concrete production, a worldwide switch from conventional concrete to \"byproduct-based\" concrete should be made. Typically, 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 also 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 10%-15% CBA [8]. Recently, [PERSON] et al. [9] conducted a study to partially replace sand with QDP and FA in the concrete produced in Israel (18 wt.% of the sand was replaced with FA, and 18 and 9 wt.% of the sand was replaced with FA and ODP, respectively). The authors reported improvements in the mechanical and chemical properties of the concrete, and in the leaching of contaminants [9]. However, the total life-cycle influence, from production to the end-of-life, of partial and/or full replacements of sand with byproducts is unknown. Life-cycle assessment (LCA) is an appropriate approach to elucidate the trade-offs of such replacements [10]. According to [11], in LCA studies, a functional unit (FU), to which all inputs and outputs of the raw materials, their embodied energies, and emissions, should be traced, must be shared by all the compared alternatives. The compared concrete alternatives (conventional and byproduct-based) should be comparable, at least in terms of their (i) fresh properties (such as the consistency), (ii) hardened properties (such as the compressive strength), and (iii) durability (such as the penetration of water). To achieve this, two different concrete mixture design methods, i.e., (i) a mixture with a fixed slump range or (ii) a mixture with a fixed water/cement (W/C) ratio, have been used in previous LCA studies [12; 13; 14]. [PERSON] et al. [12] used a fixed slump range of 185-205 mm in byproduct-based concretes that were designed using foundry sand or steel slag to partially replace the sand and FA as a mineral admixture, and they attempted to achieve comparable compressive strengths and water penetration. However, the range of the 28-day compressive strength was 30.1-45.3 MPa and the water penetration depth was 16-34 mm. Despite this relatively wide strength range, the FU was the production of 1 m\({}^{3}\) of concrete without normalization to the 28-day compressive strength. It should be noted that [PERSON] et al. [12] also conducted consequential LCA modeling for the byproducts, which allowed the prevention of byproduct disposal in landfill to be considered as a benefit of the byproduct-based concretes. As a result, the global warming potential (GWP), acidification potential, eutrophication potential, and photochemical ozone creation potential were lower for the byproduct-based concretes than those of conventional concrete [12]. [PERSON] et al. [13] compared CS-based (100 vol.% of sand was replaced with CS) and conventional concretes for fixed W/C of 0.37, 0.47, and 0.57, and followed the absolute volume method when replacing sand with CS. This is because their method restricted the addition of any surplus water that can increase the W/C ratio and, in turn, reduce the strength of the concrete.