Mechanics and durability of concrete reinforced with flax fibres or recycled baler twine

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An estimated 0.6 million tonnes of flax straw and 2000 tonnes of polypropylene baler twine are discarded in Saskatchewan every year. Previous research has demonstrated that fibres derived from these waste materials can be used to effectively reinforce concrete in some applications. However, the properties of the waste fibre-reinforced concretes must be more fully characterized, and their long-term durability must be better understood before they can be recommended for widespread use.    Short fibres of steel, plastics, or glass are commonly added to concrete to reduce the formation of cracks just after the concrete has been placed and to increase the amount of energy required to fracture the concrete (a property known as "toughness"). These properties are important for the durability of concrete pavements, bridge decks, airport runways, and parking garage floors. While flax fibres have been shown to be effective at reducing crack formation in concrete, they do not increase the toughness significantly and they have also been found to degrade over time when embedded in concrete. The proposed research will seek to better understand how severely flax fibres degrade and identify treatments that may be applied to the fibres to improve both the durability of the fibres and their ability to increase the toughness of concrete.    New chopped polypropylene baler twine has been shown to significantly increase the toughness of concrete. The proposed research will investigate the performance of recycled baler twine.  Experiments will also be conducted to measure the ability of different types of recycled baler twine to reduce cracking in concrete.    The proposed research program has the potential for identifying new markets for what are now waste materials and providing low-cost alternative fibres for use in the concrete industry.  It is expected that the research will lead to the development of fibre-reinforced concrete made using flax fibres or baler twine which possess properties that are sufficient to justify their use in certain engineering applications.