Abstract

Abstract

Abstract

The application of organic coatings is one of the most effective and economic methods to protect concrete structures from deterioration. However, organic coatings are prone to degradation under aggressive environmental actions, so the protective function may loss. While ultraviolet (UV) aging is often blamed for the degradation of organic coatings, water may play a more important role on the interfacial adhesion between the coatings and the substrate. To uncover the effect of water on the degradation performance of coating-substrate system, mortar samples coated with water-borne epoxy resin (WER) were exposed to three assigned environments, i.e., UV radiation, UV/water immersion, and UV/dry-wet cycle, up to 60 days. The surface appearance, chemical structure, wettability, and surface micro-morphology of the aged WER coatings were characterized via image process analysis, attenuated total reflectance flourier transform infrared spectroscopy (ATR–FTIR), static water contact angle, and scanning electronic microscopy (SEM). Results show that the UV/water immersion resulted in severest blistering on the WER-mortar interface, while the UV/wet-dry cycle caused the formation of micro-pinholes on the WER surface. In contrast, the UV radiation did not induce such severe aging. The data implied that water can accelerate the aging of WER-mortar system.

Abstract

Abstract

The diffusion or permeability of ions or gases through the cement matrix is key in the degradation of reinforced concrete for marine applications. The delay in ion diffusion has been an important approach to extend the life of this type of materials. In this work it is detailed how reduce degradation of cement mortar using nanotechnology. The addition of nanoparticles to the cement paste has important implications for the hydration and microstructure, reducing porosity and improving mechanical properties. In this study, different nanoparticles have been used to reduce the porosity of mortars evaluating this improvement by means of electrical resistivity measurements. It is perfectly established the porosity reduction with the increasing of electrical resistivity. Reduction of porosity minimises the intake of aggressive agents into the mortar in a meaningful way, retarding the corrosion of metal reinforcement. Nanoparticles addition (<10%) within cement mortar have allowed to increase the electrical resistivity in up to 112% regarding to control sample, without modifying of mechanical properties.       

Abstract

In this study, the impact of the thaumasite sulfate attack (TSA) on cement mortar was investigated by comparing it to the ettringite sulfate attack (ESA). Mortar specimens with three binders, corresponding to the blank, ESA, and TSA, were exposed to sulfate solution. The evolutions of thaumasite and ettringite formation, pore structure, and gas permeability on the mortar specimens were characterized through XRD, 1H NMR, and CemBureau device. The experimental results show that: (1) both ettringite and thaumasite were formed in TSA; (2) ESA reduces the capillary pore space, whereas TSA decreases both the capillary pore and interlayer pores; and (3) ESA decreases the gas permeability while TSA significantly increases it.