Long term durability of PVA reinforcing fibres in a cement matrix

The long term durability of PVA (polyvinyl alcohol) fibres used as reinforcement in cement-based products has been assessed after exposure of the products to natural weathering and an accelerated ageing process. The PVA fibres were extracted, then characterised by X-ray diffraction techniques. The mechanical properties of the extracted fibres were compared with the mechanical properties of the composite. In general an increase in composite strength and stiffness was evident; this may in part be associated with carbonation of the matrix and increase in the PVA fibre-matrix interfacial bond.

X-ray diffraction studies on the extracted PVA fibres indicated in some cases a loss of crystalline order with age (natural weathering) related to a disordering of the hydrogen-bonded sheets. The possible changes are minor and have no influence on the tensile properties of the PVA fibres or the ageing properties of the composites.

It is suggested that PVA fibres which participate in the reinforcement of the cement matrix are durable over a period of at least 7 years, and there is every reason to believe that these fibres will continue to be durable for extended periods.