Flexural strength and physical properties of fiber reinforced nano metakaolin cementitious surface compound

• The effect of nano metakaolin on properties of fiber reinforced cement has been investigated.
• Nano metakaolin increases flexural strength of fiber reinforced cement by 67%.
• Nano metakaolin reduces the capillary water absorption of fiber reinforced cement.
• Nano metakaolin improves the microstructure of fiber reinforced cement.

This study aimed at investigating the role of nano metakaolin (NMK) for enhancing the flexural strength and reducing the capillary water absorption of fiber-reinforced cementitious composites (FRCCs) for building surface plastering. Short natural fibers were added to white Portland cement (WPC) by different amounts of 0.5%, 1%, 1.5%, 2%, 2.5% and 3% by weight of cement. All samples were cured in water. It was found that as the amount of fiber increases the flexural strength increases up to about 2% by 82%, then after, a decrease in flexural strength was observed. The capillary water absorption increases with increasing fiber percent. In order to develop fiber reinforced nano-cementitious composite, different percentages of NMK ranging from 2% to 14% were used with the replacement of cement keeping constant fiber content of 2%. The phase composition and microstructure of the formed hydrates were studied using thermogravimetric analysis (TGA), X-ray diffraction (XRD) & scanning electron microscope (SEM). Additional increase in the flexural strength by about 67% was achieved at 10% NMK content. The capillary water absorption generally decreases with increasing replacements of cement by NMK. A decrease of about 50% was observed at 10% NMK.