The dissertation investigates the effect of aluminosilicate pozzolanic additives (metakaolin waste formed by producing expanded glass granules and a catalyst used in catalytic cracking in an oil plant) on the hydration, structure, and physical-mechanical properties of a lightweight cement composite with expanded glass granules. For additional modification of the structure of such a composite, a polyvinyl alcohol fibre additive was used. The developed composite is intended to be plastered onto the surfaces of industrial energy equipment, replacing asbestos plasters. The dissertation consists of an introduction, three chapters, general conclusions, lists of literature, and the author’s publications on the subject of the dissertation, a summary in English, and appendices. The introductory chapter discusses the research problem, and the relevance of the work, describes the research object, formulates the purpose and tasks of the work, describes the research methodology, the scientific novelty of the work, the practical significance of the work results, and defended statements. At the end of the introduction, the author’s publications and conference presentations on the subject of the dissertation are presented, as well as the dissertation’s structure. The first chapter discusses the hydration characteristics of Portland cement paste with various active additives (chemical, mineral, reinforcing) and their effect on the properties of cement stone, mortar, and concrete. The analysis focuses on the characteristics of light aggregates (including expanded glass granules) and the properties and areas of use of composites made on their basis. At the end of the chapter, conclusions are formulated, and the tasks of the dissertation are clarified. The second chapter describes the materials used in the work and their properties, the composition of lightweight cement composites, and the methodology of sample preparation. Applied research methods are presented, which were chosen to find out the influence of pozzolanic additives on the physical and mechanical properties of the cement composite. The third section presents the research results on the effect of pozzolanic additives (catalyst waste, metakaolin waste, and its mixture) on the hydration of Portland cement and the structure and physical-mechanical characteristics of the composite with expanded-glass granules and their evaluation. It also examines and presents the research results regarding the effect of polyvinyl alcohol fibre on the structure and properties of the composite with mixed pozzolanic additive and expanded-glass granules. The dissertation material was published in two scientific articles, and the research results were presented at four scientific conferences in Lithuania and abroad.