THE EFFECT OF WOLLASTONITE MICRO-FIBER ASPECT RATIO ON REINFORCEMENT OF PORTLAND CEMENT-BASED BINDERS

Reinforcement of Portland cement-based binders with natural wollastonite microfibres has been further investigated with emphasis on the effect of fibre geometry on property modification. Wollastonite micro-fibres were separated into five different size groups before addition to cement and cement-silica fume matrices. The aspect ratio (length/width) of the wollastonite micro-fibres was determined by scanning electron microscopy technique. Systematic experimentation including flexural tests, mercury intrusion porosimetry, helium gas pycnometry, and isopropyl alcohol saturation measurement showed that, at constant micro-fibre content, the flexural strength and total porosity of the composites remained essentially unchanged and independent of the aspect ratio of the wollastonite micro-fibres. However, the volume of coarse Pores, the Pore size distribution, the flexural toughness and overall ductility characteristics hydrated cement and cement-silica fume matrices were observed to change systematically as the aspect ratio of wollastonite micro-fibres was increased. A discussion of the differences in the observed properties is presented.