Integral mixing using nano silicon for concrete waterproofing

Abstract

Permeation of water and other aggressive fluids in concrete can result in degradation and other aesthetic problems. Consequently, these affect the service life of concrete structures. A number of research studies were undertaken to extend the service life of concrete infrastructures using various waterproofing agents. To this effect, a great deal of repair and maintenance cost can be avoided. The aim of this study is to investigate and establish waterproofing performance of nano silicon-based mortar. In this regard, nano silicon was characterized using Field Emission Scanning Electron Microscope (FESEM), Energy Dispersion Spectroscopy (EDS), Fourier Transformed Infrared (FTIR), X-Ray Diffraction (XRD), surface zeta potential and Water Contact Angle Test (WCA). Response Surface Methodology (RSM) was employed to establish the optimum mix ratio. The relationship between the experimental factors and response was modelled and validity of the model was further evaluated to ensure accurate predictions. To establish precision of the mathematical model, an experiment was planned based on Central Composite Design (CCD). The model was investigated using Analysis of Variance (ANOVA). Optimum mix ratio, necessary to increase resistance to water absorption was established at nano silicon dosage of 6.6% by weight of cement and w/c of 0.42. Furthermore, an appropriate experimental control test steps for producing waterproof cement mortar was designed. In this regard, necessary test methods from established standards were adopted to constitute supporting structure of the approach. Besides, the results were validated using macro and microstructure tests and indicated that water resistance to capillary absorption of cement mortar increased to 62%. Likewise, water absorption by immersion increased by 37%. Furthermore, resistance to water vapor transmission rate increased to 52%. On the other hand, resistance to gas permeability increased to 31% as compared to reference specimen. Moreover, while the volume of water permeable voids for nano silicon-based mortar was 16.9%, the total porosity of the same specimen was 14%. Macrostructure test indicated a good quality mortar specimen recorded an Ultra Sonic Pulse Velocity (UPV) value of 3623 (m/s). In addition, FESEM and XRD indicated the formation of a crystalline hydrophobic thin film layer of nano silicon within the pore structure of the mortar specimen. In conclusion, the nano silicon-based mortar has been proven to have a good resistance to water permeation.