## 4 Conclusions  
This study has investigated the use of binary and ternary blended calcined clay and silica fume as alternative binder, and their effect on hydration, reactivity and the mechanical and durability properties of cementitious mortar. Overall, the experimental findings showed that the co-addition of calcined clay and silica fume can improve the fresh and hardened properties of mortar by harnessing the individual characteristics of the pozzolans involved. The following conclusions have been drawn from analysis of the results:  
1. After 28 days of hydration, XRD analysis revealed substantially smaller peaks in the blended cement pastes. This is attributed to the reaction between the calcined clay/silica fume and portlandite to generate additional cementitious products like calcium silicate hydrates, evidenced by the improvement of strength in the ternary mixtures, especially at later ages. 2. The portlandite consumption test showed a significant depletion of Ca(OH)\({}_{2}\) in the blended cement mixes compared to the control paste. Pastes containing a ternary blend of calcined clay and silica fume showed a relatively higher degree of pozzolanic reactivity, resulting in lower levels of portlandite after 91 days of hydration. Between the two pozzolans, silica fume-rich pastes were found to contain less portlandite content at the end of the curing period. This was confirmed by the Frattini test results. 3. Generally, all blended cement samples exhibited lower porosity and permeability compared to the control. Porosity in silica fume-rich samples was found to be inversely proportional to the degree of porosity and permeability. The higher the silica fume content, the lower the sorptivity coefficient. Even though all samples suffered a reduction in strength as a result of the freeze-thaw cycles, the blended cement samples, irrespective of pozzolan content and dosages, demonstrated a better resistance compared to the control mix. Among the blended cements, the paste prepared with 30% silica fume offered the greatest resistance to freeze and thaw. 4. Drying shrinkage was found to be less severe in the control mortar than the blended cement mixes. Different blended cement mixes impacted drying shrinkage differently. Drying shrinkage in the blended cement mixes containing silica fume was more pronounced than the ones without. A higher level of sulphate resistance was achieved in the calcined clay-silica fume composite cements than the control. Compared to the blended cement specimens, the control suffered the most weight (13.3%) and strength (10%) losses. An increase in silica fume content in the mix resulted in a corresponding decrease in weight and compressive strength. 5. Compressive strength of all the blended cement mortar mixes trailed behind the control mortar at 3 and 7 days. SF-rich ternary blended mixes were observed to outperform the CC-rich mixes at early ages. However, at 91 days, compressive strength significantly improved, outperforming the reference cement mortar. The findings of this research are expected to contribute to the development and utilisation of alternative binders for infrastructure, especially in areas where conventions SCM's are scarce. The mix designs tested and presented in this research offer a wide range of options for construction applications depending on the intended purpose. Further studies into the long-term durability of these ternary mixes are recommended. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Sample** & **Mass Loss, \%** & **Strength Loss, \%** \\ \hline Control & 13.5 & 10 \\
30 CC & 7.0 & 4.2 \\
20 CC10 SF & 5.2 & 3.2 \\
15 CC15 SF & 6.2 & 3.5 \\
10 CC20 SF & 4.2 & 2.1 \\
30 SF & 4.6 & 2.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Changes in mass and compressive strength. Author Contributions: Writing--original draft, K.B. ; Supervision, M.K. All authors have read and agreed to the published version of the manuscript. This research received no external funding, and The APC was funded by MDPI open access publishing in Basel/Switzerland.