## 4 Conclusions  
The aim of this research was to fine-tune three mortars that have been already studied and contained wastes in their formulation, replacing cement or sand. The first one contained forest biomass ashes (replacing cement at 15% by volume), the second one contained powder of sanitary ware waste (replacing sand at 20% by volume) and the third mortar contained sanitary ware waste fine aggregates (replacing sand at 100%). The modified mortars improved some properties of the render mortars, when compared with a reference mortar, but they worsened others. In order to improve these modified mortars, the wastes were combined two-by-two and then the three of them were combined.  
Several tests were performed in order to evaluate the fresh-state, water and mechanical behaviour of the mortars in order to evaluate their technical performance. The main conclusions obtained from this research were:  
* The incorporation of some wastes in rendering mortars is viable and is a solution to reduce landfilling;
* The industrial wastes studied in this research (FBA, SWP and SWF) can reduce the amount of natural resources extracted used in mortars (as sand and cement), replacing them and producing technically viable mortars;
* It is possible to achieve mortars simultaneously with 83% of wastes and better technical performance than a conventional mortar;
* It is possible to combine wastes and take advantage of the best features of each one, maximising their advantages and minimising their limitations;
* The mortars that presented better technical performance were SWP+FBA and SWF+SWP+FBA, with respectively 19% and 83% of recycled volume;
* The SWP+FBA and SWF+SWP+FBA mortars presented better fresh-state behaviour, better water behaviour, characterized by lower water absorption, and higher mechanical strengths than the ones presented by the REF mortar.  
This research contributed to the scientific knowledge on rendering mortars and the incorporation of wastes in hydraulic materials. The incorporation of the wastes in mortars reduces the environmental impacts, not only of the new materials, but also the ones that the wastes would be responsible for if they were sent to landfill, and simultaneously improves the technical performance of the mortars.  
Figure 4: Compressive strength test results.  
**Author Contributions:** [PERSON] performed the experiments in the laboratories of Building Coatings and Thermal Insulation Unit, of Portuguese National Laboratory for Civil Engineering: [PERSON] and [PERSON] analysed the fresh, water and mechanical tests and discussed the obtained results; [PERSON] and [PERSON] were responsible for the supervision of the research. Writing--original draft preparation was performed by [PERSON] and writing--review and editing by [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by Portuguese Foundation for Science and Technology (PD/BD/113639/2015).  
**Acknowledgments:** The authors would like to acknowledge the REuSE project from National Laboratory for Civil Engineering of Portugal (LNEC) and the research unit CERIS from Instituto Superior Tecnico (IST).  
**Conflicts of Interest:** The authors declare no conflict of interest.