# Development of Passive Fire Protection Mortars
## 4 Conclusions  
The objective of this work was to develop gypsum or cement-based mortars for passive fire protection and to evaluate the influence of aggregate size and the addition of silica micro- and nanoparticles on its thermal performance. The thermal performance of these mortars in short steel columns under a compression service load and subjected to high temperatures was assessed. The following conclusions can be drawn:  
* The furnace, the dimensions of the specimens, and the test procedure adopted in the tests at high temperatures allowed an adequate thermal exposure of the specimens. It allowed the evaluation of the thermal performance of the various mortars tested. * Some mortars developed in the laboratory (DCM, DGMP, and DGMV) have better thermal performance when compared with the best commercial solution tested (CM). Furthermore, in this set of mortars without nano- and microparticles of silica, the mortars with vermiculite in their constitution were those with the best thermal performance. * Most mortars with raw material milled through the Los Angeles method had better thermal performance than mortars developed with raw material processed through the Industrial Mill method. However, if nano- and microparticles of silica are added in their composition, the mortars developed with raw material obtained through the Industrial Mill method may have a slightly superior thermal performance. * The addition of nano- and microparticles of silica improves the insulating capacity of the mortars. * Overall, the results demonstrate that the reduction in grain size of the raw materials used (perlite and vermiculite) did not benefit the thermal performance of the tested compositions. * Regarding the cracking of the mortars, it was concluded that perlite (DGMP) contributes to its low value. It was also concluded that, in general terms, the addition of NS and MS tends to increase the cracking degree of the developed compositions. * The compositions that use gypsum as a binder (DGMP and DGMV) had the best thermal insulation capacity. Under the tested conditions, it was found that 10 mm of mortar coating was sufficient to form an efficient thermal barrier, reducing the ISSP temperature by approximately 70% of the temperature recorded inside the oven (900 \({}^{\circ}\)C). * The thermal protection level of columns with the mortar developed in the laboratory with the best overall thermal performance (DGMP with nano- and microparticles of silica) was 19% more efficient than the commercial solution and increases by 5.9 times the fire resistance of an unprotected short steel column. These results demonstrated the actual impact that the application of such mortars can have as passive fire protection of steels structures. Bearing in mind the experimental findings obtained in this research study, further experimental tests on short steel columns with the developed mortars and new ones by using different additives as well as with different loading conditions will be carried out in the near future. Conceptualization, H.C. and A.S. ([PERSON]); methodology, H.C.; software, A.S. ([PERSON]); validation, L.L., L.D. and A.S. ([PERSON]); formal analysis, H.C.; investigation, H.C.; resources, A.S. ([PERSON]); data curation, A.S. ([PERSON]); writing--original draft preparation, H.C.; writing--review and editing, L.L. ; visualization, H.C.; supervision, H.C.; project administration, A.S. ([PERSON]); funding acquisition, A.S. ([PERSON]). All authors have read and agreed to the published version of the manuscript. This research was funded by the Portuguese Foundation for Science and Technology (FCT), grant number PTDC/ECI-EGC/31850/2017. Not applicable.