Effect and Mechanism Analysis of Engineered Geopolymer Composites with Hybrid Fibers: Fiber Dispersibility and Refined Mechanical Properties

In this paper, the fiber blending distribution test was designed to evaluate the workability of engineering geopolymer composites. The effect of polyvinyl alcohol, polyoxymethylene, and polypropylene fibers on the mechanical properties of engineering geopolymer composites was investigated using flexural and compressive tests. The mechanism of fiber influence on engineering geopolymer composites was investigated using x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and x-ray energy spectrometry. The test results showed that polyvinyl alcohol fibers could greatly reduce the workability of engineering geopolymer composites, while polyoxymethylene and polypropylene fibers had little effect on it. Polyvinyl alcohol fiber blended with polyoxymethylene or polypropylene fiber can effectively improve the 28-day compressive strength of engineering geopolymer composites. Polyvinyl alcohol fibers were easily chemically bonded with C─ (A)─ S─ H gels and interacted with geopolymer matrix mainly through chemical bonding and physical bonding. The chemical bonding of polyoxymethylene and polypropylene fibers to the geopolymer matrix was weak, mainly through physical bonding. Thus, the hybrid fiber of polyvinyl alcohol fiber and polyoxymethylene or polypropylene fiber can fully combine the respective advantages of fiber, making the workability and mechanical properties of engineering geopolymer composites more balanced.