Effectiveness of treatment methods on polypropylene fibres incorporated in cement mortars

Fibre reinforcements are often used in cementitious materials to provide enhanced strength. However, the surface smoothness and inert chemical nature of polypropylene fibres result in an insufficient fibre–matrix bonding interface and hence lead to poor mechanical properties of these materials. Two distinct treatment methods, namely, porofication method and sulfuric acid–dichromate treatment method, are adopted to assess the effectiveness of these techniques on fibre–matrix interface properties. The paper begins with an investigation on the effectiveness of these methods on polypropylene fibres. The wetting characteristics of these fibres are determined using the water absorption test, contact angle measurements and scanning electron microscopy analysis. The study then focuses on the mechanical properties and durability of cement mortars incorporating treated polypropylene fibres. The void ratio, flexural and compressive strengths and split tensile strength are studied, and microstructural analyses are also carried out to support these measurements. The resistance to impact, freeze and thaw and carbonation of cement mortars incorporating treated polypropylene fibres is investigated. The treatment methods adopted in this study improve the interface between the hydrated cement product and fibres and also significantly enhance the mechanical properties and durability of these mortars incorporating polypropylene fibres.