Surface modification of miscanthus fiber with hydrophobic silica aerogel for high performance bio-lightweight concrete

Bio-fiber reinforced cementitious material is now attracted widespread attention thanks to its low carbon footprint and its advantages in energy conservation in buildings. However, the main concerns of using large volume of bio-fibers in concrete is its high water absorption and the leaching of organic matter that is incompatible with cement. This study investigates a surface modification method of a bio-fiber (miscanthus) by using hydrophobic silica aerogel and further evaluates its mechanical and insulating performance in lightweight concrete and increase its compatibility with cement. X-ray diffraction, thermal gravimetry and calorimeter test were carried out to investigate the effect of hydrophobic miscanthus fibers on the microstructure of cement matrix. The results show silica aerogel modified miscanthus fiber enhances both the compressive and flexural strength, meanwhile significantly improving the insulating performance of concrete. The use of superhydrophobic aerogel particles reduces the sugar leached from miscanthus and the hydration heat peak is only slightly delayed with the incorporation of aerogel coated miscanthus fibers. The results of this study shed light on surface modifications of bio-fibers for applications in high performance construction materials.