THE FLEXURAL TOUGHNESS AND DUCTILITY OF PORTLAND CEMENT-BASED BINDERS REINFORCED WITH WOLLASTONITE MICRO-FIBERS

An analysis of the flexural toughness and ductility of Portland cement-based binders reinforced with natural wollastonite micro-fibres is reported. The flexural toughness was calculated as the sum of finite area increments under the entire load-deflection curve and the ductility was determined from the deflection in the post-peak region. Load-deflection curves were created with numerical data obtained in flexural tests employing the computer controlled MT'S system. Five series of specimens were investigated. A series of specimens made with cement and blended with different amounts of silica fume served as reference systems. The other four series of specimens contained seven different concentrations of wollastonite micro-fibres, each series having a different amount of silica fume. Results showed that the flexural toughness of the cement-silica fume system decreased non-linearly as the amount of silica fume in the mixture increased. The flexural toughness of the cement-wollastonite composite system and the cement-silica fume-wollastonite composite system was observed to increase almost linearly as the concentration of the wollastonite micro-fibres in the composite matrices increased. The increase of the flexural toughness with increasing concentration of wollastonite micro-fibres in the composite mixtures was influenced by the amount of silica fume. The ductility of the composite matrices increased nonlinearly with increase in concentration of wollastonite micro-fibres in the composite mixtures. The amount of silica fume in the composite matrix had no significant role in modification of ductility in the composite system. Differences in observed properties are discussed.