STABILITY OF PORTLAND CEMENT-BASED BINDERS REINFORCED WITH NATURAL WOLLASTONITE MICRO-FIBERS

The stability of Portland cement-based binders reinforced with natural wollastonite micro-fibres was investigated for hydration periods up to one year. The wollastonite microfibres imbedded in the hydrated cement paste were examined employing a scanning electron microscopy technique. Composite specimens were also periodically evaluated by flexural strength testing and microstructural characterization including mercury intrusion porosimetry, helium gas pycnometry, and isopropyl alcohol saturation measurement. The amount of Ca(OH)2 in the hydrated matrices was also determined by differential scanning calorimetry. Wollastonite micro-fibres imbedded in hydrated cement-silica fume matrices remained stable after prolonged hydration and exhibited no surface or bulk deterioration. The flexural strength and overall pore structure of the Portland cement-based binders reinforced with wollastonite micro-fibres also remained essentially unchanged and unaffected. Flexural toughness and the post peak deflection, however, were observed to decrease with hydration time . The amount of Ca(OH)2 in the hydrated matrices decreased slightly at advanced hydration times. The observed behaviour is discussed.