Mechanical properties of high-ductility cementitious composites with methyl silicone oil

Methyl silicone oil is used to precondition silica sand for the preparation of high-ductility cementitious composites. Its effect on their mechanical properties is investigated. Results indicate that the presence of methyl silicone oil significantly enhances the ductility (tensile strain capacity) of high-ductility cementitious composites while undermining their compressive and flexural strengths. The strain hardening behaviour, which is indicated by the slope of the linearised tensile stress–strain curve following the first cracking point, was found to be a maximum at 2% methyl silicone oil followed by a gradual decrease at a higher methyl silicone oil content. This behaviour can be explained by the interaction mechanism of methyl silicone oil on the matrix and fibre–matrix interface. Methyl silicone oil is found to improve the fibre distribution as a result of the oil presence on the fibre surface. Microscopic observation reveals that the fibre–matrix interface becomes porous through the presence of thin rod-like hydration products. This reduces the fibre bonding to the matrix that facilitates pullout but increases the post-pullout friction, which is beneficial in ductility improvement.