en گروه سرامیک Ceramic Materials and Engineering Research Paper Research Paper <div style="text-align: justify;"><span style="font-size:11pt"><span style="line-height:200%"><span style="unicode-bidi:embed"><span calibri="" style="font-family:"><span new="" roman="" style="font-family:" times="">This study evaluates the mechanical performance of a metakaolin-based geopolymer matrix reinforced with quartz particles and polypropylene fibers, in comparison with a Portland cement-based matrix. Compressive strength, shrinkage, and flexural strength tests reveal that incorporating 20 wt% quartz particles significantly improves the mechanical properties of both matrices. The combined use of quartz particles and fibers contributes to shrinkage crack control and dimensional stability through synergistic effects involving particle&ndash;matrix interactions, fiber&ndash;matrix bonding, fiber surface characteristics, and toughening mechanisms. In the geopolymer matrix, the reinforcement effect of quartz particles is more pronounced due to the formation of a strong and chemically active interfacial bond. Compared with Portland cement composites, quartz particles increase the flexural and compressive strengths of geopolymer composites by approximately 2.5 and 1.3 times, respectively. The addition of 0.5 wt% polypropylene fibers slightly reduces strength but enhances energy absorption and alters the failure mode from brittle to more ductile. Overall, the results highlight the role of fibers in suppressing or arresting brittle fracture in cementitious and geopolymeric composites.</span></span></span></span></span></div> Geopolymer,Quartz sand,Portland cement,Polypropylene fiber 123 136 http://ijmse.iust.ac.ir/browse.php?a_code=A-10-1056-4&slc_lang=en&sid=1 Ardalan Aalipour ehsan.1376.a@gmail.com 1800319475328460022057 1800319475328460022057 No Department of Materials Engineering, SR.C., Islamic Azad University, Tehran, Iran Azam Moosavi az_moosavi@yahoo.com 1800319475328460022058 1800319475328460022058 Yes Department of Materials Engineering, SR.C., Islamic Azad University, Tehran, Iran