Microstructure of lime pastes with the addition of vegetable oils

Vegetable oils can be used as water- repellent additives for mortars and coatings for improving their durability when applied in the protection of structures exposed to severe weathering conditions involving water ingress. Previous studies have shown that, besides imparting water -repellence, vegetable oils can significantly affect the microstructure of the lime paste. The influence of the addition of different amounts (0.5 and 1.5 wt%) of linseed, stand, and rapeseed oil on the microstructure of lime pastes has been investigated with thermogravimetry, Fourier transform infrared spectroscopy, X -ray powder diffraction, and scanning electron microscopy, up to 18 0 days of age. The wettability of the pastes was analysed by measuring the contact angle of water drops on the pastes’ surface. The overall results indicate that linseed and rapeseed oil are more reactive with lime than stand oil, thus , affecting the microstructure of the paste more significantly. The lower reactivity of stand oil is assigned to the considerably lower amount of carbon -carbon double bonds as compared with the other oils. A higher amount of stand oil may be required to achieve water -repellence in the lime paste.