The doctoral thesis submitted by Ing. Lukáš Matějka addresses a highly relevant and scientifically significant topic concerning the influence of zinc compounds on the hydration of Portland cement and the possibility of mitigating these adverse effects through the use of hydration accelerators. The subject is closely connected with current trends in the cement industry, particularly the increasing use of alternative fuels and secondary raw materials, which contribute to elevated concentrations of trace elements in cement raw materials and binders. The topic is also important in the field of hazardous waste immobilisation using cementitious materials. 
The dissertation summarizes the results of long-term research conducted within a grant-funded project focused on suppressing the negative effects of zinc contamination in Portland cement. During his doctoral studies, the candidate actively participated in the design of experiments, preparation of samples, execution of measurements, evaluation of results, and their interpretation. He gradually acquired extensive expertise in a broad range of experimental techniques commonly used in the study of cement hydration, including isothermal and isoperibolic calorimetry, thermal analysis, and X-ray diffraction. 
The thesis is logically structured and well organized. The literature review provides a comprehensive overview of the current state of knowledge regarding Portland cement hydration, the effects of zinc on hydration processes, and the application of various hydration accelerators. This section is followed by the presentation and discussion of the candidate's original research results, which are based on published scientific papers.
Among the most important achievements of the dissertation are:
•    a systematic clarification of the differences between the effects of soluble zinc compounds and zinc oxide on the hydration of Portland cement,
•    demonstration of the synergistic effect of zinc and ground granulated blast-furnace slag leading to significant prolongation of setting time,
•    clarification of the role of ettringite formation in mitigating the negative effects of zinc on cement hydration,
•    experimental verification of the effectiveness of several groups of hydration accelerators,
•    demonstration of the unsuitability of alkaline thiocyanates for ZnO-contaminated cement systems,
•    evaluation of the performance of both commercial and pure nitrate-based accelerators,
•    identification of formate salts, particularly calcium formate, as highly effective accelerators capable of substantially reducing the setting time of ZnO-containing Portland cement while maintaining or even improving the mechanical properties of the hardened material. 
The results presented in the thesis are not only scientifically valuable but also possess considerable practical potential for application in the cement industry. They contribute to a better understanding of the mechanisms responsible for zinc-induced retardation of cement hydration and provide practical recommendations for the design of cementitious systems containing elevated levels of heavy metals.
The quality of the candidate's work is further demonstrated by his publication record. He is a co-author of several scientific papers published in international journals indexed in the Web of Science and Scopus databases, and he is the first author of a number of these publications. He has also presented the results of his research at national and international scientific conferences.   
Throughout his doctoral studies, Ing. Lukáš Matějka demonstrated the ability to conduct independent scientific research, critically evaluate experimental results, and communicate scientific findings effectively. He actively participated in research projects and made a significant contribution to the research activities of the department. I particularly appreciate his systematic approach, diligence, attention to detail in experimental work, and ability to solve complex research problems.
From both scientific and formal perspectives, the dissertation fulfils the requirements expected of a doctoral thesis. It presents original scientific findings and clearly demonstrates the candidate's ability to independently conduct advanced research and solve demanding scientific problems.

Conclusion
I state that Ing. Lukáš Matějka has successfully fulfilled the objectives of his doctoral studies as well as the goals defined in the dissertation thesis. I therefore recommend the dissertation for defence and, upon its successful defence, I recommend that Ing. Lukáš Matějka be awarded the academic degree of Doctor of Philosophy (Ph.D.).