## 1 Introduction  
In 2016, the total weight of wastes generated by the EU-28 amounted to 2538 million tonnes [1]. Construction and demolition waste represented 36% of the total wastes generated [1] and was still the most pollutant sector. It was also responsible for producing materials that have great impacts on the environment, such as cement. According to the European Cement Association, one tonne of CEM II produced releases 738 kg of CO\({}_{2}\) into the atmosphere [2]. According to the European Commission [3], the long-term goal of Europe is to become a recycling society, avoiding waste production and using wastes (the ones that are unavoidable) as raw materials whenever possible, thus minimizing the extraction of additional natural resources. In order to achieve the aims proposed, Directive 2008/98/CE of the EU set up a minimum rate of reuse, recycling or other material recovery [4], 70% (by weight) for construction and demolition waste. The encapsulation of wastes in hydraulic materials, such as cement-based mortars, is a possible solution for the wastes' management [5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21]. The incorporation of wastes, replacing the original constituents of the mortars (natural aggregate or cement), can improve some characteristics of the mortars, and consequently improve their technical performance. The authors of this research, as well as others [6; 14; 15; 16; 17; 18; 19; 20; 22; 23; 24; 25; 26], have been studying the incorporation of wastes in cement-based mortars, namely render mortars and found that the incorporation of wastes is responsible for modifying some properties of the mortars, improving some properties and compromising others. In three previous researches [5; 6; 14] from the authors of this research, the incorporation of three wastes in rendering mortars was analysed: forest biomass ashes, sanitary ware waste powder and sanitary ware waste fine aggregates. The main advantages and limitations of each waste are summed up next. The incorporation of forest biomass bottom ashes (FBA) in mortars significantly improves the environmental benefits of the mortars [27], since it reduces the volume of cement content. The encapsulation of biomass ashes in cement-based mortars also reduces the environmental impacts of landfill, since the cement matrix is responsible for a reduction of release of elements such as arsenic (As), chromium (Cr) and molybdenum (Mo), when compared with the release of pure biomass ashes [28]. In a previous research, it was found that the replacement of CEM II/B-L 32.5 N at 15% (by volume) with forest biomass bottom ashes resulted in mortars with lower CO\({}_{2}\) emissions, by about 13%, when compared with a reference mortar [27]. Technically, it was found that the replacement of cement with FBA produced weaker and slightly more water-absorbent mortars, but also more deformable and ductile [14], which are considered advantages in rendering mortars. A decrease of mechanical strength was also found by other researchers [29; 30]. In another research [6], it was found by the authors that the incorporation of sanitary ware powder (SWP) waste in rendering mortars resulted in stronger and less permeable mortars, which agrees with the findings of other researchers [31]. The mortars presented high flexural and compressive strengths [6; 31]. The increments of strength at 28 days were 250% and 227%, respectively, for flexural and compressive strength [6], relative to the reference (REF) mortar. The water permeability (by capillarity) was reduced in the first minutes by 30%, relative to the EF [6]. However, the incorporation of this type of waste (as powder) was noticed to be detrimental to the mortars' deformability, which led to higher susceptibility to micro-cracking [6]. This was responsible for a reduction of strength over time. At 90 days, the flexural strength was reduced by about 48% and the compressive strength by about 36% [6].