Thermo-physical properties of nanostructured lightweight fiber reinforced cementitious composites

Cementitious materials are widely used for cladding of the building envelopes; however, they possess low thermal resistivity, low tensile strength and ductility which leading to cracking with time. It would be advantageous to improve thermal resistivity of lightweight cementitious materials whilst keeping their mechanical performance acceptable/reasonable. This study represents an extension to a work that has investigated the role of nano metakaolin (NMK) in enhancing the flexural strength of fiber reinforced cementitious composites (FRCC). An optimum composite of NMK - modified FRCC was determined. The aim of this study is to develop nanostructured lightweight fiber reinforced cementitious surface composites (NLWFRCC) with improved thermal properties and reasonable mechanical strength. For this purpose; white Portland cement (WPC) was partially replaced with different amounts of perlite ranging from 10% up to 70% by volume of cement then substituted by 10% nano metakaolin. Natural fibers were added by 2% by mass of binder. The bulk density, thermal conductivity, solar reflectivity, flexural strength, and capillary water absorption were determined in accordance to ASTM standards at 28 days of curing. The microstructure characteristics of the hardened NLWFRCC were investigated by scanning electron microscope (SEM). It was found that the density, thermal conductivity and flexural strength decrease with increasing replacements of cement by perlite, thermal conductivity at 70% perlite is 6.3 times less than the composite with no perlite (plain). Even at 70% Perlite; the developed NLWRFCC still retaining sufficient strength. Incorporating perlite into WPC, led to a significant enhancement in reflectivity especially in near infrared region; an increase of about 33% was obtained at 70% perlite.