چكيده به لاتين
In the past decade, Boron nitide nanosheets (BNNSs) has attracted the interests of researchers as supplementary materials in construction industry due to their extraordinary mechanical properties, large surface area and strong interaction with the host matrix. However, the role of BNNS in cementitious alkaline environment due to its poor stability and lack of uniform dispersion needs further investigation. Therefore, this study investigates the effect of influential factors such as ultrasonication energy, the presence of cations, alkalinity and surfactants on BNNS dispersion in the cementitious alkaline environment. For this purpose, UV-vis test, atomic force microscope, scanning electron microscope, transmission electron microscope, dynamic light scattering, zeta potential measurement, mini-slump test, helium porosity test, compressive and flexural strengths were performed on the control samples and BNNS containing samples. The results show that the ultrasonication energy equal to 165000 J/mg within the aqueous solution with a concentration of 0.024 mg / ml guarantees the best level of BNNS dispersion. Moreover, Ca2+ is the most detrimental cation among other ones (Na+ and K+) in the case of BNNS agglomeration in the cementitious alkaline environment. Furthermore, although, in the solutions with alkalinity of 7.5 to 12.2, the dispersion of BNNS is stable, at high alkali media with PH value equal to 13.1, BNNS dispersion undergoes reduction. Among examined surfactants, gum arabic, polycarboxylate ether based superplasticizer and naphthalene based superplasticizer showed highest ability to stabilize the dispersion of BNNS in the cementitious alkaline environment, respectively, while sodium dodecyl sulfate had poor ability to maintain BNNS dispersion. Finally, by optimizing the above-mentioned parameters and adding only 0.01 wt% of BNNSs, the compressive and flexural strengths of cement paste increased by 14.59% and 7.83%, respectively.
