B. Sena da Fonseca

Influence of GFRP Confinement of Reinforced Concrete Columns on the Corrosion of Reinforcing Steel in a Salt Water Environment

AbstractThis paper concentrates on the changes on the corrosion rate of the steel bars of RC columns due to their wrapping with glass fiber–reinforced polymers (GFRPs). RC cylindrical laboratorial specimens, both unwrapped and wrapped with GFRP, were immersed in a sodium chloride solution for 20 months. The changes on concrete resistivity and the corrosion process were followed by open potential measurements and electrochemical impedance. It was possible to quantify the influence of the GFRP jackets in the solution uptake and on the corrosion of the steel reinforcement. The results showed a delay on the diffusion of the solution into concrete due to the presence of the GFRP, which allowed that the bars remained in a passive state for longer immersion periods. The GFRP barrier lowered the rate of uptake of the solution and the chloride ion penetration. However, the GFRP jacket may have the properties as a physical barrier reduced due to imperfect application. The incomplete concrete saturation makes oxygen...

TEOS-based consolidants for carbonate stones: the role of N1-(3-trimethoxysilylpropyl)diethylenetriamine

For several years functional organosilanes containing NH groups have been tested to improve the performance of TEOS-based consolidants for carbonate stones, however different efficacies are being reported and the role of side-effects in sol–gel routes is still unclear. The present study aims at improving the efficacy of a formulation for carbonate stone consolidation by adding N1-(3-trimethoxysilylpropyl)diethylenetriamine (SiDETA) to previously developed TEOS-based consolidants. While xerogels derived from reference sols were transparent, dense, and with smooth morphology, SiDETA-modified xerogels were translucent, coarser and composed of interconnected nanosized particles. It was concluded that SiDETA changed the mechanism of silica network formation by modifying the sols pH, acting as a nucleation center, and by ionic interactions. Despite the changes in the silica network structure, SiDETA incorporation showed to cause additional strength increments on the treated stone.