## 1 Introduction
GPC is also recognized as the earth friendly concrete (EFC) and can be produced by activating the source material rich in alumina and silica by alkaline activator solution (AAS) [13; 14; 15; 16]. The utilization of GPC causes reduction in energy consumption, CO\({}_{2}\) emissions, and overall budget due to the effective consumption of by-products/waste materials, thus making it an environment friendly material [7; 13; 17; 18]. However, these emissions vary for different location and mixes, and depend on several factors such as location, curing, transportation distance of source materials, andthe production of the activator solution. For the sake of comparison, the contribution to CO\({}_{2}\) emissions as a percentage of each of the ingredient/activity, from sourcing of raw materials to the curing of 1 m\({}^{3}\) of concrete, for GPC and OPC/conventional concrete is summarized in Figure 1[8]. This is one of the typical cases of CO\({}_{2}\) emissions for a specific mix design and location. The reported calculations were based on the activities associated with production of 1 m\({}^{3}\) of Grade 40 concrete (i.e., compressive strength of 40 MPa) which comprises locally available materials, manufacturing, and construction methods in the Melbourne Metropolitan area in Australia. The OPC is by far the most significant contributor to emissions, contributing 76.4% of CO\({}_{2}\) emissions in conventional concrete. On the other hand, the contribution of the geopolymer binder (fly ash + sodium silicate (SS) + sodium hydroxide (SH)) towards total emissions is 63% in the GPC. By weight comparison reveals 201 kg of CO\({}_{2}\) emissions from the geopolymer binder which is 25% less than the OPC binder (269 kg of CO\({}_{2}\) emissions) in the conventional concrete. The alkali activators required for the production of GPC expend significant energy. The total emissions for all the ingredients/activities from sourcing to curing of the OPC/conventional concrete and the GPC are estimated as 354 kg and 320 kg of CO\({}_{2}\) respectively [8]. A significant difference between emissions during the curing processes of both the concretes is due to the high temperature (40-80 \({}^{\circ}\)C) curing of the GPC for at least 6 h to achieve strength comparable to the OPC concrete. However, the CO\({}_{2}\) emissions during the curing operations can be reduced to less than 1 kg by promoting ambient curing conditions in the GPC construction. If ambient curing conditions are considered, then the total CO\({}_{2}\) emissions for the GPC construction would reduce to 281 kg, i.e., 21% less than the CO\({}_{2}\) emissions of the conventional concrete (for each cubic meter) for this specific case. It is reported that GPC can achieve better strength and durability properties than the OPC concrete if heat curing is performed at a temperature of 60-100 \({}^{\circ}\)C [19; 20]. [PERSON] and [PERSON] (2006) stated that the heat curing of GPC at elevated temperature results in higher compressive strength than the ambient curing [21]. The heat curing of GPC may practically be possible to manufacture precast concrete elements. However, such curing conditions may be challenging for in situ application of GPC. To make GPC application possible for in situ construction, material containing high calcium content like slag can be incorporated to increase reactivity of FA. By the addition of slag in FA based GPC, geopolymeric gel is produced along with the formation of calcium silicate hydrate (C-S-H). These hydrates help GPC to set at ambient temperature and improve its mechanical properties [22]. A number of studies have been carried out on GPC with FA and SG being the source materials [19; 20; 21; 22; 23]. [PERSON] et al. (2015) used silica fume in different dosages in combination with fly ash and metkaoain to improve the mechanical properties and concluded that the elevated temperature curing is the most suitable option to produce a stronger GPC [23]. [PERSON] et al.