Polymer-based construction materials have gained global popularity in recent decades, finding widespread use in various applications like repair materials, pipes, roadway pavements, and bridge decks. As an environmentally conscious approach, concrete can contribute to CO2 emission mitigation by replacing or partially replacing the conventional cement binder with polymers. While existing studies have explored polymer concrete, there is limited information on the mechanical properties and application of polymer mortar. This study investigates the materials in the formulation of mortars utilising polyurethane resin as a substitute for cement and compositions used in polymer mortar mixtures, assessing their fresh properties and compressive strength. The impact of substituting fine aggregate with fly ash on fresh and mechanical properties and binder hardening characteristics is also examined, aligning with sustainable development principles in construction. Replacing components with more cost-effective alternatives is also explored to reduce material costs. The investigation delves into the use of fly ash waste from coal combustion in conjunction with PU resin, which is distinct from its common usage in Portland cement concrete. The fresh and mechanical properties were evaluated, including fresh density, consistency by flow table, working life, dry density and compressive strength. The study found that the innovative polymer mortar exhibits excellent mechanical properties, making it suitable for structural elements such as pipes, slabs, beams, columns, and walls. Additionally, using fly ash as a filler or partial substitute for sand contributes to sustainability by utilising industrial waste. The findings indicate that polyurethane resins can be a sustainable alternative to conventional cement, promoting eco-friendly construction practices.