چكيده به لاتين
Many studies have been carried out on the effect of nanoclay on the cement composites. However, there are little researches in the halloysite nanotube effect as a subcategories of nanoclay on the properties of cement composites. The good mechanical properties of nano halloysite have made them useful as an additive to improve the mechanical properties of cement composites. Halloysite properties are nanotube structure, high length to diameter (L/D) ratio, high specific surface, large pore volume, low density in the surface, and pozzolanic properties. But one of the important issues in the discussion of the function of halloysite nanoclay is a dispersion or its uniform distribution in the cement environment. In the alkaline environment resulting from the cement hydration due to the presence of Van der Waals interactions between halloysite particles, the dispersion of these particles is not well done, and this may reduce the capacity of using these nanomaterials. Therefore, in this research, the behavior of halloysite nanotube in cement alkaline environment, the effect of existence free ions due to the cement hydration process and the effect of alkalinity of the environment on agglomeration of the halloysite nanotube, the performance of various surfactants in improving the dispersion of halloysite nanotube and the effect of halloysite on the alkalinity of the cement environment were investigated. The results show the inappropriate dispersion of halloysite in cement alkaline environment compared to deionized water, more effect of calcium ion due to bridging effect on agglomeration of halloysite nanotube, best halloysite dispersion in PH=11, polycarboxylate as the best surfactant in improving halloysite dispersion and decreasing alkalinity of cement environment it contains halloysite nanotubes. Also, in this study, the effect of halloysite nanoparticles was investigated on the performance of cement mortar and the evaluated workability, mechanical properties, and durability of samples containing 1 and 3% of halloysite nanotubes. The results of this study showed a 25% increase in compressive strength, an increase of 21% in flexural strength, 19% reduction of calcium hydroxide from the TGA test, increased by 28% electrical strength, a decrease of approximately 26% of the water absorption rate, a 15% reduction in water absorption, a decrease of 23% at a water desorption rate, 35% reduction in helium porosity, as well as reduced workability and increased hydration rate of the mortar containing 3% of halloysite nano tube was compared with control sample. These results indicate that the halloysite nanotubes it can be used as a suitable nanoparticle to improve the properties of concrete. The results of this research can be the application of nanoparticles in cementitious matrices provides the basis for the use of more efficient cement.
Keywords: halloysite nanotube, dispersion, cement mortar, mechanical properties, durability.
