## 4 Concluding Remarks  
This study explored the possibility of using SS as a single precursor in AAM. The effect of the variation of the activation parameters, namely, the Na\({}_{2}\)O concentration and silica modulus, on the fresh and hardened properties of BOF slag-based AAM was evaluated through a series of experiments. The focus was given to the structural and microstructural behavior of the AAM pastes. The main conclusions were as follows:  
* The BOF slag studied presented low pozzolanic behavior, low heat generation and may be considered a low-reactivity material. Nevertheless, the alkali activation process and hardening of pastes were confirmed in all studied cases. * Crystalline phases of the BOF slag dissolved under the alkaline environment to produce hydrates in all studied formulations, as presented by the TGA and XRD results. * The high initial heat release measured from the formulations with a high concentration of Na\({}_{2}\)O and a high silica modulus may have contributed to the rapid setting, thus compromising the casting process of those formulations. Figure 16: SEM image of 2.22M-4% (magnification of 2000\(\times\)) with elemental mapping and EDX spectra of the scanning points: (**A**) RO phase (embedded in BOF particle), (**B**) steel particle, (**C**) calcium silicate (unreacted BOF slag particle) and (**D**) C-S-H (reaction product). * All formulations presented the same behavior in terms of hydrate formation over the curing time. The TGA results showed the amount of hydrates by quantifying the mass loss, but no correlation with compressive strength development was determined. Other external factors are related to compressive strength, such as workability, molding process, water content and internal porosity. * A low silica modulus combined with a low Na\({}_{2}\)O concentration led to the identification of residual Ca(OH)\({}_{2}\) in the TGA and XRD results. This strongly suggested that the alkali reaction was weaker, and thus, less reaction products were formed, which jeopardized the strength development. * A high silica modulus combined with a high Na\({}_{2}\)O concentration increased the alkalinity in the solution, thus increasing the intensity and speed of the heat release. Moreover, the excess of silicate and OH\({}^{-}\) limited the diffusion of ions, and thus, the reaction of Ca\({}^{2+}\) with Si\({}^{4+}\). As a result, the casting process and the strength development were compromised. * Finally, better strength performance was achieved when an optimized combination of activator sources was considered. In this study, a low Na\({}_{2}\)O concentration (4%) with an intermediary silica modulus (1.50-2.22) presented the best mechanical results (compressive strength up to 20 MPa), a good amount of reaction products formed (C-S-H/C-A-S-H gel and CaCO\({}_{3}\)), and a low initial and cumulative amount of heat released. Although the compressive strength was lower than for the conventional ones, it is essential to highlight that BOF slag is an important industry waste that presents economic and environmental benefits and can be used in future engineering projects. Conceptualization, V.A.N. and P.H.R.B. ; data curation, V.A.N. ; methodology, V.A.N., P.H.R.B. and C.T. ; validation, V.A.N. and P.H.R.B. ; formal analysis, P.H.R.B. ; investigation, V.A.N. and P.S. ; resources, P.H.R.B. and A.C.S.B. ; writing--original draft preparation, V.A.N. ; writing--review and editing, V.A.N., P.H.R.B., C.T., A.C.S.B. and P.S. ; visualization, V.A.N. ; supervision, P.H.R.B. and C.T. ; project administration, V.A.N. ; funding acquisition, V.A.N. and P.H.R.B. All authors have read and agreed to the published version of the manuscript. This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior--Brasil (CAPES)--finance code 001, grant PPM-00709-18 (FAPEMIG) and grant 316882/2021-6 (CNPq). Not applicable.