چكيده به لاتين
Halloysite nanotubes are mineral clays which have various industrial applications but in concrete industry haven’t been considered as much. Suitable mechanical properties of halloysite nanotubes have resulted in to be considered as a nanoscale additive in cementitious materials. Halloysite nanotubes have properties such as high length to diameter (L/D) ratio, high specific surface area, low density on the surface, rough surface, pozzolanic and hydrophobic properties. The notable problem in utilizing nano-halloysite particles is their uniform dispersion in the cementitious matrix. One of the methods to gain a suitable dispersion of the nanoparticles in the cementitious matrix is ultrasonic method, but the main challenge of this method is the selection of the optimum ultrasonication energy, which it should make the particles to be dispersed uniformly in the cementitious matrix and on the other hand don’t hurt the nano-scale particles. Due to the lack of researches in optimum ultrasonication energy field for dispersion of the halloysite nanotubes, the selection of the optimum ultrasonication energy is difficult. So, in the first part of this research the effect of the ultrasonication energy on the dispersion of the halloysite nanotubes in aqueous and cementitious medium was investigated. The results showed that the cement mortar with 2 percent of the weight halloysite nanotubes in 960 Joule/CHNT energy level has the best functionality in mechanical point of view, and this energy level was chosen as optimum ultrasonic energy level. And yet by using this optimum ultrasonic energy level, in the second part of this research workability and mechanical properties and durability of cement mortars containing 1, 2 and 3 weight percent of the cement halloysite nanotubes were evaluated. The results in this part showed a decrease in workability, 46 percent increase in compressive strength, 21 percent increase in flexural strength, 60 percent decrease in porosity, 51 percent increase in sulfate attack resistance after 15 weeks being immersed in 5% sodium sulfate solution, in samples containing 2 percent halloysite nanotubes. Due to excellent functionality on mechanical and durability compared to others, this 2 percent replacement of halloysite nanotubes in cement mortar was chosen as optimum percentage.
