## 4 Conclusions  
The results of the tests mentioned in the methodology lead to a series of partial conclusions that converge in the verification of the final hypothesis. The final hypothesis of this research is the study of the viability of biomass bottom ashes as filler in bituminous mixtures of discontinuous grading and bitumen emulsion. Therefore, we proceed to define the partial conclusions:  
* The chemical composition of biomass bottom ash reflects that it is a mainly inorganic material, with a low percentage of organic matter. The main chemical elements are potassium, calcium, silicon, sulfur, chlorine, magnesium, and phosphorus, these elements being usual in other types of biomass ashes.
* The main chemical compounds of biomass bottom ash are silicates, potassium carbonate, sylvite, and arcanite. These compounds are responsible for the cementitious properties discussed by different authors.
* The biomass bottom ash leachate test showed a low concentration in the leachate of heavy metals, as well as carbon and sulfur. Consequently, their use in bituminous mixtures is acceptable without producing environmental pollution problems, especially when the ashes are coating by bitumen.
* The grading of the biomass bottom ash after treatment is suitable for use as a filler in bituminous mixtures.
* The particle density and bulk density in kerosene of the biomass bottom ashes are acceptable according to the standards, highlighting the higher specific surface area of the ashes reflected in the bulk density and scanning electron microscope test. In addition, the ashes do not show plasticity.
* The bituminous mixtures conformed with biomass bottom ash filler obtain similar physical properties, void content, to mixtures conformed with limestone filler and ophite filler.
* The mixtures conformed with biomass bottom ash have a lower particle loss due to the existence of a quality mastic that coats the aggregates and holds them together under tensile loads.
* The Marshall test showed that bituminous mixes with biomass bottom ash have higher strength and, consequently, better plastic deformation behavior, even with a higher percentage of bitumen, than mixes with ophite filler and limestone filler.  
Based on the partial conclusions, it can be stated that biomass bottom ash has acceptable chemical and physical characteristics for use as a filler in bituminous mixtures. In addition, its use as a filler in discontinuous grading bituminous mixtures with bitumen emulsion develops a quality mastic capable of providing better tensile strength, better behavior to plastic deformations, higher bitumen absorption, and physical properties similar to traditional mixtures. At the same time, it should be noted that the use of a waste product that is currently unused for the conforming of bituminous mixtures avoids the deposition of this by-product in landfills, avoids the extraction of new raw materials, and creates sustainable materials for construction.  
Conceptualization, F.A.C.-I., F.J.I.-G., J.M.T.-S., and J.S.-M.; methodology, F.A.C.-I., F.J.I.-G., J.M.T.-S., and [PERSON]-M.; software, J.M.T.-S. and [PERSON]-M.; validation, F.A.C.-I. and F.J.I.-G.; formal analysis, F.A.C.-I. and F.J.I.-G.; investigation, J.M.T.-S. and J.S.-M.; resources, F.A.C.-I.; data curation, F.J.I.-G.; writing--original draft preparation, J.S.-M.; writing--review and editing, J.M.T.-S.; visualization, J.M.T.-S.; supervision, F.A.C.-I.; project administration, J.S.-M.; funding acquisition, F.A.C.-I. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Data Availability StatementData are contained within the article.  
The technical and human support provided by CICT of Universidad de Jaen (UJA, MINECO, Junta de Andalucia, FEDER) is gratefully acknowledged.  
The authors declare no conflict of interest.