Semester of Graduation
Master of Science in Engineering Science (MSES)
The mechanical and physical properties of novel metakaolin (MK) based Engineered Geopolymer Composites (EGCs) consisting of locally available river sand (RS) or manufactured microsilica sand (MS) reinforced with polyvinyl alcohol (PVA) fiber were studied. Plain geopolymer (GP) binder, GP mortars, and fiber-reinforced composites were also studied. Aspects of the material composition that were investigated in this study include binder composition, aggregate type, and PVA fiber content. Per the compressive strength results, GP mortars presented greater compressive strength than GP binder where the GP mortars manufactured with lower water to solids ratio exhibited greater compressive strengths. Furthermore, the incorporation of PVA fiber produced an important increment in compressive strength. Moreover, an enhancement in compressive strength of the composite was seen with an increase in fiber content. Additionally, MS tended to produce composites with higher strength compared to those using RS. All the composites evaluated in this study exceeded the compressive strength of regular concrete (i.e., 30 MPa) while exhibiting low densities (i.e., 1.80-1.94 g/cm3). Moreover, K321 GP-MS-1.6%PVA EGC presented the highest compressive strength of 57.5 MPa, thus classifying it as high strength concrete per ACI Committee 363. Furthermore, per uniaxial tensile test, tensile pseudo strain-hardening (PSH) behavior was observed for the MK-based GP composites manufactured where MS produced higher tensile strength and strain capacity compared to RS. However, due to the lack of proper fiber dispersion (i.e., fiber clumping), robust PSH behavior was not achieved. According to Scanning Electron Microscopy (SEM), several unreacted metakaolin particles were encountered indicating incomplete geopolymerization in both GP binders evaluated in this study. Additionally, there was good agreement between the intended chemical composition of the manufactured GP binders and the actual chemical composition found in the specimens examined via energy dispersive X-ray spectroscopy (EDS) in the geopolymer gel.
Abufarsakh, Ruwa, "Effect of Fine Aggregate and PVA Fiber Content on the Properties of Metakaolin-Based Engineered Geopolymer Composites" (2022). LSU Master's Theses. 5661.