# Clinker-Free Cement: A New Reality
## 3 Results and Discussions  
### Raw Materials Results  
According to Table 4, the primary chemical components of GBFS are SiO\({}_{2}\), CaO, Al\({}_{2}\)O\({}_{3}\), and MgO, which make up more than 90% of the composition. BOF slag, on the other hand, has high levels of CaO and ferric phases, as well as high quaternary basicity indices--IB4 (NBR 16697) [19], and ternary--IB3 (EN 15743) [20]. These high basicity levels of BOF slag help in the chemical activation of GBFS and the formation of hydration products. Gypsum waste's chemical composition consists mainly of CaO and SO\({}_{3}\), which means that its purity is greater than 95%, stoichiometrically calculated.  
The mineralogical gypsum waste composition indicates that it is a byproduct of the hydration process of anhydrous or hemihydrate phases, consisting mainly of gypsum. Additionally, the cement grinding did not result in the removal of water.  
BOF slag is composed of crystalline materials such as belite (Ca\({}_{2}\)SiO\({}_{4}\)-C\({}_{2}\)S) and brown-millerite (Ca\({}_{4}\)Al\({}_{2}\)Fe\({}_{2}\)O\({}_{10}\)--C\({}_{4}\)AF). It also has a high amount of the wustite phase (FeO) which is typical of BOF slag. These mineral phases can significantly affect the reactivity of the reaction environment, especially when it comes to its hydraulic behavior and the formation of hydrates resulting from the hydration of BOF slag phases. Additionally, BOF slag also functions as an alkaline activator due to the presence of phases such as lime and portlandite.  
On the other hand, due to the granulation process of blast furnace slag, the material is mostly amorphous, meaning that it lacks a definite shape and is not crystalline in nature. According to the Rietveld method, the material has a vitreous degree of 99%, indicating that it is predominantly glassy. Hence, it was not possible to identify significant crystalline peaks in the material.  
The degree of vitrification of the slag, based on the counting technique using transmitted light optical microscopy, corroborates the XRD results since blast furnace slag presented a predominantly vitreous crystallinity degree, greater than 98%. The BOF slag presented a predominantly crystalline structure attributed to its chemical composition, which had a high content of alkaline oxides, and the function of its slow cooling after leaving the converter.  
In terms of reactivity, GBFS displayed better mechanical behavior than BOF slag for both normal and accelerated curing conditions. However, despite having inferior  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
\begin{tabular}{c} **Chemical** \\ **Constituent** \\ \end{tabular} & **BOF** & **GBFS** & **GW** & **Mineralogical Phases** & **BOF** & **GBFS** & **GW** & **BOF** & **GBFS** \\ \hline LOI \({}^{\text{A}}\) & 0.44 & 0.38 & - & Belite—\(\text{\text  
performance, the mortar composed of BOF slag exhibited hydraulic activity, mainly due to the presence of C\({}_{4}\)AF and C\({}_{2}\)S phases [21].  
The utilization of an accelerated method reduced the difference in mechanical resistance between the slags, which led to a faster hydration process. However, although the accelerated curing conditions favored the reactivity of BOF slag, the stability of its crystalline atomic structure plays a crucial role in its reactivity. In the context of cement hydration, the dissolution and crystallization reactions will be slower for this material.