Designing construction and building material containing recyclable resources have become a potential demand for sustainable development. The main objective of the research is to create fly ash cement paste (FCP), which incorporated various proportions of fly ash (FA) to replace Portland cement (PC) for ecological purposes. In this research, the dry density, compressive strength, water absorption, drying shrinkage, and chloride ion penetration (CIP) examinations were performed on mix designs assembled from various FA fractions (0, 20, 40, 60, and 80%) as a partial substitution of PC. Based on the laboratory findings, incorporating 20% FA in FCP formulations can achieve comparable bearing capacity at all cured ages as a reference mix. Among all FCP mixtures, specimens containing 20% FA exhibited the greatest compressive strength value of 70.92 MPa at 120 days, while the 80% FA samples exhibited the weakest load-carrying capacity of 39.28 MPa. The finding was consistent with the test results of the dry density and water absorption experiments since the optimized engineering characteristics may be attained by keeping the FA consumption below 20%. In addition, the ion charging conveyed across the FCP mixture can be mitigated by utilizing an adequate FA concentration (20%), contributing to an equivalent in resistivity compared to the reference mixture. The analysis findings also demonstrated a strong correlation between water absorption and CIP levels because a lower porosity value can lead to a denser framework and restrict chloride ions from migrating via the specimen. Besides, replacing the PC with high-volume FA was beneficial in reducing the drying shrinkage of the FCP. Overall, optimizing the FA content in FCP below 20% promotes ecological growth objectives while maintaining acceptable performance, highlighting the positive impact of proper FA utilization in achieving a balance between ecological considerations and desired engineering properties.