Comparison of Selected Properties of Geopolymers and Cement Concretes with the Addition of Biomaterials Derived from the Fruit Processing Industry and Lake Restoration

The growing demand for CO2 emission reduction and efficient waste management has created a need for the development of sustainable construction materials. This study presents a comparative investigation of geopolymer and cement-based composites modified with bio-based additives originating from two abundant and underutilized waste streams: apple-processing waste and biomass collected during lake restoration activities. Geopolymer and cement composites containing 5 and 10 wt.% apple-processing waste or 5 and 10 vol.% lake fibers were prepared, and their compressive strength, flexural strength, density, and thermal conductivity were experimentally evaluated. The results revealed substantial differences between the investigated binder systems. Apple-processing waste significantly deteriorated the mechanical performance of both materials, particularly in cement-based composites, where disturbances in cement hydration and loss of structural integrity were observed. Although geopolymer composites also exhibited reduced compressive strength after the incorporation of apple residues, their structural cohesion was maintained. In contrast, biomass fibers obtained from lake restoration demonstrated considerably better compatibility with the geopolymer matrix, limiting compressive strength reductions to approximately 13–16% while contributing to improved crack resistance and post-failure integrity. The incorporation of bio-based additives reduced composite density and decreased thermal conductivity, resulting in enhanced thermal insulation performance. The lowest thermal conductivity was obtained for the geopolymer containing 10 wt.% wet apple waste, reaching 0.4216 W/(m·K), compared with 0.7067 W/(m·K) for the reference geopolymer. The findings indicate that lake-restoration biomass represents a promising reinforcement for geopolymer-based construction materials, whereas fruit-processing residues require further pretreatment before practical application. Overall, the study highlights the superior compatibility of geopolymers with organic waste streams and demonstrates their potential as sustainable, non-structural construction materials supporting circular economy strategies, waste valorization, and environmental remediation efforts.