## 5 Conclusions  
The replacement of PC with CWP in concrete has been established to significantly alter the fresh, mechanical, and durability properties of the concrete. However, the potential of CWP concrete has yet to be fully realised due to certain limitations and knowledge gaps. The key conclusions and recommendations are summarised as follows:  
1. CWP enhances compressive strength, reduces water absorption, improves chemical resistance, and provides better thermal insulation at optimal replacement levels(typically 10-20%). A 10% substitution rate is effective for higher-strength concrete (40 MPa), while up to 20% is suitable for lower-strength concrete (<30 MPa).
2. The pozzolanic activity of CWP may contribute to a denser concrete matrix, refining its microstructure and enhancing its long-term durability.
3. Replacing cement with ceramic waste powder (CWP) up to 30% generally leads to a 15-30% reduction in concrete slump. However, this reduction can be mitigated by using finer CWP particles (\(\leq\)35 \(\upmu\)m) or incorporating superplasticisers. Some studies have also highlighted the effectiveness of bio-based additives, like Bacillus megaterium, in improving workability.
4. Replacing 5-10% of PC with CWP typically increases the compressive strength by 5-15%, particularly in concrete with a strength class of 40 MPa and below. However, increasing the replacement level to 20% often results in a strength reduction of 10-20%. The use of nanoCWP or CWP particles finer than 35 \(\upmu\)m can further enhance the strength by an additional 3-6%. Although the general trend is consistent, some discrepancies exist across studies, likely due to differences in CWP characteristics, mix proportions, and testing methodologies.
5. Contradictory findings on the optimal percentage replacement, pozzolanic reactivity, and later-age strength highlight the need for a deeper investigation.
6. Differences in the effects of CWP, such as its pozzolanic reactivity and contribution to durability, may be influenced by the particle size, chemical composition, and ceramic source of CWP.
7. Further studies on the use of CWP in concrete should focus on the following aspects: 1. Conducting long-term durability tests on CWP concrete in aggressive environments, including exposure to chloride. Chloride conductivity tests on CWP concrete would be helpful. 2. Investigating the pozzolanic reactivity of CWP at different replacement levels to determine its optimum percentage for balancing strength and durability. 3. Assessing the impact of CWP particle size, source variability, and its optimum particle size distribution on concrete performance. 4. Exploring the replacement of SCMs (e.g., fly ash, GGBS, silica fume, and nanomaterials) with CWP to compare the pozzolanic behaviours of CWP with those of other pozzolanic materials. 5. Further testing should be conducted on high-strength concrete (above 40 MPa), as the existing literature predominantly focuses on concrete with strength classes of 40 MPa or lower.  
Conceptualization, P.O.A., J.O.I. and A.J.B.; methodology, P.O.A.; software, P.O.A.; validation, J.O.I. and A.J.B.; formal analysis, P.O.A.; investigation, P.O.A.; resources, J.O.I. and A.J.B.; data curation, P.O.A.; writing--original draft preparation, P.O.A.; writing--review and editing, J.O.I. and A.J.B.; visualization, A.J.B.; supervision, J.O.I. and A.J.B.; project administration, J.O.I. and A.J.B.; funding acquisition, J.O.I. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Durban University of Technology South Africa Research Scholarship and Future Professor program [GOOT-0258 GT019]. And The APC was funded by the Future Professor programme [GOOT-0288 GT019].  
Not applicable.  
No new data were created or analysed in this study. Data sharing is not applicable to this article.