Microstructure and mechanical performance of bamboo fiber reinforced mill-scale—Fly-ash based geopolymer mortars

Natural fiber reinforcement in cementitious matrices is being explored to provide an environment-friendly solution for lowering the overall carbon footprint of construction materials while giving the matrix much-needed tensile strength. Short bamboo fibers extracted from Bambusa blumeana or Kawayan tinik using 5% sodium hydroxide solution and treated with 10% aluminum sulfate solution are used to reinforce zero-cement geopolymer mortars. Bamboo fibers with varying lengths of 10 mm, 20 mm, and 30 mm are mixed with mill-scale – fly ash-based geopolymer in varying 0%, 0.5%, 1%, 1.5%, and 2% fiber loading per weight of specimen sample. Compressive strength and split tensile strength tests are administered to small cylinder samples, 50 mm in diameter by 100 mm in height, in accordance with ASTM C780. An optimum fiber length of 20 mm and fiber loading of 1.4% by weight is determined using Response Surface Methodology (RSM). The addition of bamboo fibers increased the unconfined compressive strength up to 292.41% compared to specimens without bamboo fibers. The split tensile strength also improved by up to a 355.82% increase compared to control samples. The corresponding high-strength and low-strength samples are also subjected to Fourier-transform Infrared Spectroscopy – Attenuated Total Reflectance (FTIR-ATR) to investigate and compare the stretching of bands between the raw materials and tested specimens. Scanning Electron Microscopy – Energy Dispersive X-Ray analysis (SEM-EDX) is used to show microscopic images and the elements present in the selected samples. The implications of the results on the material development of bamboo fiber-reinforced geopolymer mortar for construction are discussed.