The effect of polypropylene fibers was investigated by compression and bending tests, identification of the resulting phases by X-ray XRD diffraction pattern test and phase morphology by field microscope FE-SEM, investigation of thermal behavior and types of bonds formed by DTA-TG thermal test and FTIR was performed. The results showed that the strength increases with the increase in the storage time of the samples from 7 to 28 days. The addition of polypropylene fibers has increased the compressive strength compared to the sample without fibers. By adding 3% of 4 and 8 mm fibers, the compressive strength of 28 days increases by 46%. The XRD results showed that quartz and pyrophyllite minerals are the main remaining phases of these structures after the geopolymerization process in all samples. The FTIR results showed that in the geopolymeric samples, the CM-1 peak at 1030/63 has shifted to higher frequencies, i.e. 1528/171-1422/97 cm, which indicates the progress of the geopolymerization process. SEM images showed that the extrusion mechanism is more dominant than other mechanisms. The results show that samples containing 3% by volume of fibers have the highest compressive and bending strength and can be considered as optimal values.