Bricks have been essential to architecture since antiquity, with clay bricks being the predominant material utilized. The conventional clay brick manufacturing technique, although robust and readily available, has several environmental and resource-related issues. These problems have encouraged a gradual transition to alternate materials. The novelty of the research lies in assessing the balance between reduced cement content and enhanced durability by leveraging fly ash’s pozzolanic characteristics. Notably, the cement content was systematically reduced from 300 kg/m3 in FAB1 to 260 kg/m3 in FAB4 to investigate the trade-offs between strength and sustainability. FAB4, with the most fly ash concentration, attained superior outcomes, including the highest compressive strength (10.2 MPa), lowest water absorption (9%), and greatest densities (1890 kg/m3 wet and 1778 kg/m3 dry). Conversely, FAB1, characterized by the lowest fly ash and greatest cement content, had the least resistance to acid attack and compressive strength (6.9 MPa in HCl, 5.4 MPa in sulfuric acid), attributable to elevated free lime levels that react with acids to produce soluble salts, hence exacerbating deterioration. Intermediate mixes (FAB2 and FAB3) exhibited reasonable performance, with FAB3 marginally surpassing FAB2 owing to superior optimization of fly ash and cement, leading to a denser matrix and equilibrated hydration products. The influence of cement reduction is likely masked by the dominant effect of increasing fly ash content, indicating a need for isolated optimization of cement dosage.