## 3 Results and Discussion
### Suppressing CO\({}_{2}\) Emissions by Use of Slag in Cement Manufacturing  
International policy frameworks developed by the Paris Agreement Sustainable Development Goals (SDG) calls for immediate actions to be taken to suppress CO\({}_{2}\) emissions. According to the World cement Association, cement producers have developed plans to contribute towards this direction, by outlining pathways for low-carbon cement production. Despite the profound benefits that cement offers in shaping our modern built environment, it is undoubtedly a massive source of carbon dioxide to the atmosphere. According to estimates from the International Energy Agency, it accounts for about 7 percent of all global carbon emissions, meaning that it is the second-largest single industrial emitter, second only to the iron and steel industry. Further to this, it is expected that cement production will vastly increase by within the next 20 years due to the increasing demand in cement from developing countries. Thus, solutions must be implemented to reduce CO\({}_{2}\) emissions because this it may likely put the Paris Agreement's global climate targets in jeopardy (e.g., [41; 42]). The production of Portland cement leaves a notable carbon footprint due to the use of fossil fuels to create the necessary intense heating but more important, from the chemical decomposition of limestone that releases large amounts of CO\({}_{2}\) as a byproduct. Proposed solutions include the use of alternative fuels, the implementation of innovative carbon capture technologies, as well as the use of recycled byproducts from other industries, such as slag, fly ash and clay material.  
Scientists and cement industries are combining forces and are expected to succeed in gradually reducing CO\({}_{2}\) emissions, although there are still many barriers to be dealt with [43]. Blast furnace  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Slag** & **Expansion (mm)** \\ \hline – & 0.0 \\ –* & 0.0 \\
3-1a & 0.5 \\
3-2a & 1.3 \\
4-2a & 2.0 \\
5a & 0.6 \\
3-1b & 1.6 \\
3-2b & 1.0 \\
4-1b & 2.0 \\
4-2b & 1.5 \\ \hline \hline \end{tabular}
\end{table}
Table 12: Expansion of manufactured SCs (40% slag).  
slag production can partially replace clinker in cement by even up to 50% or directly in to be used in concrete. Moving one step forward, the results of the present research demonstrate that the allowable main cement constituents list of the current cement norm [17] could potentially be expanded to include other kind of slags beyond the blast furnace slags. The testing principles applied in this study demonstrate that the selection criteria should not rule out slags just based on the chemical analysis and amorphous slag content as currently in place for the GGBFS, but consider whether the properties of the corresponding obtained cements meet the required technical specifications for their application. Increasing the potential volume of slag cement would result in significant environmental and economic benefits, since its production requires less than a fifth of the energy compared to the production of Portland cement and releases less than a fifteenth of the carbon dioxide emissions. Additional sustainable benefits are that manufacture of slag cement does not require the quarrying of virgin limestone materials, but also the fact that the slag is considered as a key link to achieve a sustainable circular economy, to move our society from a linear economic system by using slag as an eco-friendly byproduct.