## 4 Conclusions  
The production of heating devices generates solid wastes that are harmful to the environment but can be managed. This paper presents research into the possibility of using waste enamels for the production of cement composites. According to the experimental results and results of testing the pozzolanic activity of waste vitreous enamels, as well as their influence on the properties of cement paste, mortar and concrete, several major conclusions are drawn as follows:  
1. Used waste enamels possess pozzolanic activity and belong to class 15 (WEP), that is 5 (WETM) of pozzolanic materials. Additionally, both waste enamels meet the criteria for the activity index according to EN 450-1, which refers to their possible use as a type II admixture for the production of concrete in accordance with EN 206. Waste enamels WEP and WETM in terms of water requirement, initial setting time and soundness meet the criteria prescribed by the Standard.
2. Examinations of the physical and mechanical properties of mortars with waste enamels have shown that these materials can be used as a replacement for cement in the production of mortar, where is recommended a maximum cement replacement in the amount of 30% for WEP, and 20% for WETM. These replacements of cement with waste enamels in mortar do not significantly affect its physical and mechanical characteristics in comparison with the characteristics of the reference mortar prepared with 100% cement.
3. The use of waste enamels in concrete, as a partial replacement of cement, contributes to a slight decrease in physical and mechanical properties, while on the other hand, it does not compromise the durability of the concrete. Test results indicate that the replacement of cement with WEP up to 30%, or WETM up to 20% does not significantly affect the quality of concrete compared to the quality of the reference concrete prepared with 100% cement.
4. Bearing in mind that vitreous waste enamels can be used for the production of cement composites, the problem of their disposal is solved, which is a great contribution to preserving a healthy environment.
5. Further research should be focused on studying the behavior of reinforcement in concrete produced with the addition of waste enamels, as well as the possibility of the production of concrete paving flags and blocks.  
In general, by finding a useful value for vitreous enamel waste materials and their application, the process will be improved and contribute to cleaner production, as the most suitable for industrial application.  
[PERSON] conceived and designed the experiments, wrote the paper, and contributed to all experiments and the analysis of the obtained results. [PERSON] and [PERSON] contributed to the conceptualization and analysis of all the obtained results [PERSON] performed physical-mechanical measurements and contributed to analyzing the results. [PERSON]-[PERSON] contributed to FESEM experiments. [PERSON] participated in leaching test measurements and analysis of the obtained results. [PERSON] contributed in the work with XRPD measurements. Supervision [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.