Microstructure and durability properties of cement mortars containing nano-TiO2 and rice husk ash

• Cement mortar is produced with incorporation of nano-TiO2 and rice husk ash.
• Improvement in durability of mortar is showed by addition of NT and RHA.
• More packed pore structure is observed by addition of nanoparticles.
• The permeability is reduced with an increase in the contents of RHA and NT.
• Synergic influence of nanoparticles is illustrated by XRD results.

In the present study, Compressive strength, water absorption, electrical resistivity, Rapid Chloride Permeability Test (RCPT) and Ultrasonic Pulse Velocity (UPV) tests of the hardened composites incorporating two supplementary cementitious materials: agricultural waste ash namely as rice husk ash (RHA) and nano-TiO2 (NT) in cement mortars were investigated. The interfacial transition zone (ITZ) and the microstructure were studied by using Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) analysis, respectively. Compressive strength results showed a substantial improvement in samples containing NT and also a slight increase in mortar performance was observed by using up to 10 wt% of RHA as a replacement of cement. However, binary mixtures displayed the best results for strength development and durability. It is also seen that a combination of 15% RHA and 5% NT in mortar led to a positive contribution to durability properties. XRD analysis showed that intensity of Alite and Belite phases decreased and new peak of portlandite achieved with the addition of NT. The SEM micrographs illustrated the widespread distribution of mortars containing NT with packed pore structures which resulted in promoting of strength and durability of specimens. Consequently, the combined mixture of RHA and NT has led to the enhancement of strength and durability properties of mortars. In general, it seems that 15% RHA and 5% NT can be considered as a suitable replacement regarding to the economic efficiency and hardened properties.