# Physical-Mechanical Properties of Cupola Slag Cement Paste
## 2 Materials and Methods  
### Materials  
Cement  
In this work, two types of cement were used: CEM I-52.5 R and CEM III-32.5N-SR according to EN 197-1 [32]. The density and Blaine specific surface area were determined according to UNE 80103 [33] and EN 196-6 [34] respectively. In addition, the chemical composition of each cement was determined by means of an X-ray fluorescence test.  
Cupola Slag  
The chemical composition of the slag is essential to define its cementing properties. In addition, it was considered essential to check that this chemical composition was stable over time, so periodic tests were carried out for 13 months.  
Subsequently, in order to assess the use of slag as a replacement for OPC in the manufacture of mortar used in the internal lining of pipelines, it is necessary to ensure that it does not contain chemical compounds that could be harmful to health. To check this point, a leachate test was carried out in order to obtain the concentration of the chemical elements present in the slag. The analysis of the cupola slag leachate was carried out in accordance with EN 12457-4 [35].  
Once it was verified that the use of the cupola slag does not suppose any potential risk, cupola slag filler (CSF) was obtained from cupola slag aggregates (CSA). The process of obtaining CSF consists of 7 phases, and images of the complete reduction process can be seen in Figure 1.  
* Phase 1 (Figure 1a): CSA obtained from the pipe manufacturing process is available.
* Phase 2 (Figure 1b): The CSA is fed into a ball crusher with water for 8 h.
* Phase 3 (Figure 1c): After 8 h of wet crushing, the contents of the mill are poured into a large container.
* Phase 4 (Figure 1d): To facilitate drying, the material is transferred to smaller trays with a larger specific surface area.
* Stage 5 (Figure 1e): The trays are placed in an oven at 100 \({}^{\circ}\)C until the material is found to be free of moisture.
* Phase 6 (Figure 1f): Once the material is found to be completely dry, it is ready for use.
* Phase 7 (Figure 1g): Final appearance of the CSF.  
It was decided to crush 8 h after testing different times and obtaining the minimum time required to reduce the material size to filler. 2 h, 4 h, 6 h, and 8 h were tested and it was found that it is necessary 8 h, in an enamel mill with alumina balls, to obtain more than the 95%wt. of the material smaller than 75 \(\upmu\)m.  
The characterisation of CSF was divided into five phases; physical properties, setting time, vitrification, pozzolanicity test and ensuring sulphate resistance. The physical properties were obtained in the same way as for cement. To ensure that the actual pipe manufacturing process is not significantly modified, the setting times were compared using the procedure described in EN-196-3 [36]. Initially, three mixtures were used: the reference cement CEM III; a mixture of 80% CEM I and 20% CSF; and a mixture of 50% CEM I and 50% CSF. In a second phase, the mixture of 50% CEM I and 50% CSF was also used, but using an activator (1% sodium oxide in relation to the amount of CSF added). To analyse the degree of vitrification of the cupola slag, an X-ray diffractogram was performed. Once the presence of amorphous silica compounds was verified, a pozzolanicity test was performed according to EN-196-5 [37]. Finally, as the application requires resistance to sulphates, and the CEM III currently used to line pipes is sulphate resistant, it was necessary to check that the mixtures of CEM I with CSF are also sulphate resistant. For this purpose, the amount of C\({}_{3}\)A in the mixture was calculated to check that the mixture meets the sulphate resistance requirement of EN 197-1 [32]. For this purpose, the Bogue Formula (1), was used, which was applied to the CEM I clinker, as CSF does not provide C\({}_{3}\)A.  
\[\text{C}_{3}\text{A}=-1.6920\text{Fe}_{2}\text{O}_{3}+2.6504\text{Al}_{2}\text{O} _{3} \tag{1}\]