•Use of polymer resin minimized with addition of fillers and fibers to the matrix.•Varied the micro filler contents like Fly ash (FA) and Quartz powder (QP).•Varied the macro-filler contents like Poly-Methyl-Metha-Acrylate (PMMA), Sand.•Varied the fiber contents like Glass fiber (GF) and Steel fiber (SF).•Developed of composites with a high compressive strengths ranging from 80 to 107 MPa.•Nondestructive studies were done by UPV and dynamic Moduli.•Durability was determined water absorption and exposure to alkaline environment. The use of polymer composites in highly aggressive environments has compelled the research focused towards enhancing the performance characteristics through matrix modifications, by incorporating suitable fillers and fibers. Suitable matrix modification of the composite has resulted in the development of high strength and durable material, which can be used in coastal and marine structures. In addition to this, they can be used in sewage systems prone to alkali attack. The present study is focused to investigate the effects of varying the filler and fiber contents in fly ash based polymer composites. The study was carried out to minimize the utilization of polymer resin with an improvement in the mechanical and durability characteristics of the final composite. The effect of varying the micro-filler contents like Fly ash (FA) and Quartz powder (QP) (0–20%), macro-filler contents like Poly-Methyl-Metha-Acrylate (PMMA) (0–40%), Sand (40–80%) and fiber contents like Glass fiber (GF) and Steel fiber (SF) (0–2%) on the performance of polymer composite has been presented through the results of laboratory investigation of parameters like compressive strength, tensile strength, ultrasonic pulse velocities (UPV) and dynamic Moduli. The durability characteristics were determined through water absorption studies and exposure to aggressive alkaline environment. The suitable matrix modification has yielded in development of composites with a high compressive strengths ranging from 80 to 107 MPa and tensile strengths ranging from 14 to 20 MPa with enhanced durability characteristics.