Characteristic of Fresh and Harden Properties of Polyvinyl Alcohol Fibre Reinforced Alkali Activated Composite

Fibre can enhance the mechanical properties of cement-based composites, but fibre also degrades their workability. However, the quantitative effects of fiber content and length-diameter ratio on alkali-activated materials are still unclear. Various aspect ratio, volume fraction of polyvinyl alcohol fibre (PVAF), and various water-binder ratio were employed to prepare a total of 26 groups of fibre reinforced alkali-activated composite (FRAAC). The influence of PVAF fibre factor (product of fiber volume fraction and length-diameter ratio) on flowability, compactness, strength, and crack fractal dimension of FRAAC was researched. The influence of water-binder ratio on the plastic viscosity of FRAAC was more significant than that on the yield stress. When fibre factor was lower than critical value of 150, the influence of fibres could be overlooked. The reason was that the space between fibres was distant, so the flowability of FRAAC was not impacted by PVAF. At this time, fibres were challenging to restrict the cracks in matrix and increase their mechanical properties. When fibre factor was higher than critical value 150 and lower than density packing value 450, the flexural strength, compressive strength and crack fractal dimension of FRAAC were considerably enhanced, and the FRAAC could still flow easily under dead weight. When fibre factor were above 450, noteworthy fibre balling considerably decreased the flowability, leading to poor solidity and reduced compressive strength. Hence, the ideal content of PVAF in alkali activated composite is between 150/(l/d) and 450/(l/d).