Effect of high tensile strength polypropylene chopped fiber reinforcements on the mechanical properties of sodium based geopolymer composites

The geopolymer matrix is ideal for incorporating a variety of reinforcements for structural applications. In the case of this experiment, the reinforcements are high tensile strength polypropylene (PP) chopped fibers of lengths of 0.5″, 1″, and 2″. The fibers were added in increments of 0.92, 1.01, 1.32, and 2.48 weight percents. These samples were then tested in a three point bending apparatus at a loading rate of 176 Newtons per minute. The maximum stress for each sample was then compared to that of the pure, nonreinforced, sodium geopolymer matrix. The samples prepared using the 0.5″ fibers achieved average maximum stresses of 9.9±0.5, 9.0±1.3, 9.9±3.0, and 15.1±1.5 MPa, respectively for increasing weight percent of fibers. Samples prepared using the 1″ fibers had average maximum stresses of 9.6±3.8, 10.5±1.6, 12.4±1.34, and 14.4±1.0 MPa with respect to increasing fiber contents. The samples prepared with the 2″ fibers had average maximum stresses of 9.0±0.9, 11.2±1.4, 13.5±1.7, and 18.3±0.8 MPa with respective increasing fiber composition. This data was compared to the average maximum stress achieved by the pure sodium geopolymer (NaGP) of 1.8±0.5 MPa. From this data Weibull statistics were calculated to determine the mechanical reliability of the material. According to the Weibull statistics for each fiber length used, the 0.92, 1.01, and 2.48 weight percent samples produced the most reliable data, where the 1.32 weight percent samples produced data that was reasonably reliable, while the pure geopolymer samples did not produce reliable data.