## 3 Results and Discussion  
Figure 15 shows an example of the shape of the samples after pressing, labelling and curing at RWTH. The height of each manufactured sample varied with the different recipes and the different MPs of the press. The height showed values between 24 and 52 mm, depending on the filling factor of the mould. Cold compression strength (CCS) tests were carried out using an INSTRON multifunctional breaking strength testing machine with a 500 kN load cell. Samples were placed in between the load cell (upper position) and the moving bar (lower position). The moving bar subsequently was driven up just before the sample touched the load cell. Thus, the testing procedure started by basically following ISO BS 4700:2015 with a moving speed of the lower bar of 15 mm/min. The test was aborted manually at the point when (1) max. resistance was reached and (2) visual disintegration of the sample itself noticeably started. Figure 16 shows an MA604 sample after the CCS testing procedure placed in between the load cell and reversed moving bar. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline
**RECIPE** & **PP** & **GS** & **OCF** & **CCD** & **CARBON** & **FIBRES** & **STARCH 2301 DD** & **STARCH 6501 XC** & **WATER** \\ \hline MA604C & SC & 46.4 & 34.1 & - & 10.3 & - & - & 9.2 & - \\ MA604B & SC & 46.0 & 33.8 & - & 10.2 & 0.9 & - & 9.2 & - \\ MA604B & BC & 46.0 & 33.8 & - & 10.2 & 0.9 & - & 9.2 & - \\ CC03 & SC & - & 34.4 & 34.1 & 14.9 & - & 9.7 & & 7.0 \\ CC02A & BC & - & 36.2 & 35.9 & 15.6 & 0.9 & & 4.0 & 7.4 \\ UO & - & 43.1 & 33.8 & - & 10.2 & 1.9 & - & 11.0 & - \\ \hline \end{tabular}  
* PP: press parameter; GS: grinding sludge; OCF: oxy-cutting fines; CCD: combustion chamber dust.  
\end{table} 
Table 12: Recipes of the agglomerates produced and tested at RWTH and UOulu (composition in wt%). Figure 15: Exemplary MA604B agglomerates manufactured with a 10 N/mm\({}^{2}\) manufacturing pressure (MP). Results of the compression strength dependent on different MPs and recipes are given in Table 13 and illustrated by the following diagrams. For every MP and recipe, the average of four CCS tested briquettes is reported. Results of the CCS test of the briquettes based on grinding sludge and oxy-cutting fines (MA604 series) are shown in Figure 17. The figure depicts the dependency of compression strength on MP, the parameter \"clearance\" between upper stamp and mould as well as the compression strength dependency on the use of fibres as reinforcement in the mixture. For the MA604B recipes, it can be derived that the increasing MP leads to a higher compression strength. For MA604B SC, the increase in compression strength (10 vs 40 N/mm\({}^{2}\)) was in the range of about 60%, and for MA604B BC, the increase was in the range of about 15%. However, it seems that there exists a threshold for the MP, at least for MA604B BC, at approximately 30 N/mm\({}^{2}\), where an increase in MP does not lead to a higher compression strength. Based on the results of MA604B SC versus BC, it seems that the clearance between the mould and the stamp only has an influence on the compression strength for lower manufacturing pressures, while the resulting compression strength for a higher MP seems to be independent of the clearance. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**RECIPE** & **PP** & \multicolumn{4}{c}{**MANUFACTURING PRESSURE (N/mm\({}^{2}\))**} \\ \cline{3-6}  & & **10** & **20** & **30** & **40** \\ \hline MA604C & SC & 73.9 & 80.2 & 84.5 & 83.2 \\ MA604B & SC & 53.6 & & & 84.4 \\ MA604B & BC & 42.8 & 38.5 & 40.0 & 34.4 \\ CC03 & SC & 18.6 & 21.6 & 23.8 & 22.8 \\ CC02A & BC & 46.4 & 49.1 & 52.3 & 51.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Cold compression strength (average of four tests) of the agglomerates produced and tested at RWTH. Figure 16: MA604 after the cold compression strength (CCS) testing procedure. What can clearly be stated from the results obtained is that the use of fibres in the recipe increased the compression strength by approx. 70%-100% depending on the MP.