This paper presents an experimental study to evaluate effect of TiO2 on self-cleaning
performance of mortars exposed to controlled UV irradiation for up to 1500 hrs. Portland cement mortars and mortars with 50% slag as cement replacement were included, and w/cm of the mortars was 0.5. In addition, effect of TiO2 on rate of cement hydration, workability, and strength development of mortars were evaluated as well.
Results indicated that the rate of cement hydration was increased with the increase in TiO2 dosage from 1 to 6 % by mass of cementitious materials in both pastes with or without slag. Workability of the fresh mortars was not affected significantly by 1% TiO2. However, the workability was decreased with further increase in TiO2 dosage. Compressive strength of the mortars at 28 days was decreased with the increased in TiO2 dosage up to 6%. The decrease was more pronounced for the Portland cement mortars than the mortars with slag. At 91 days, the compressive strength of the Portland cement mortars with TiO2 was only slightly lower than that without, and there was no significant difference for the slag mortars with or without TiO2. Mortars with 1% TiO2 showed good self-cleaning performance and faster rates of colour recovery of the contaminated specimens to their original colour of uncontaminated conditions.
With a further increase in TiO2 dosage to 2%, the rate of colour recovery was further increased. However, the percentage of improvement was less significant compared with 1% TiO2. There was no obvious improvement in self-cleaning when the dosage of TiO2 is further increased beyond 2%. Self-cleaning efficiency of the mortars tended to decrease with increasing irradiation time. Further study is need for long-term performance and performance in tropical environment.