Desenvolvimento de micropartículas de liberação controlada para a realcalinização de argamassas e concretos sujeitos à ação do Co2

Abstract

The corrosion of steel in reinforced concrete structures is a significant contemporary socio-economic problem. It leads to the early deterioration of structures and significant economic losses. CO2 is one of the most aggressive agents that cause corrosion. It reacts with cement hydration products in a process known as carbonation, resulting in a decrease in pH and leaving the reinforcement susceptible to corrosion. This study developed microparticles (microspheres) that dissolve on demand and release an agent that regulates the pH of the matrix, providing a barrier to CO2 and/or a gain in service life for reinforced concrete structures. The microparticles were produced using biopolymers maltodextrin and chitosan as the matrix material, along with calcium, sodium, and aluminum hydroxides as re-alkalizing agents. Following the production of the microspheres in a spray dryer, they were characterized to assess their alkalinization potential and integrity, with the pH variation of the medium serving as the criterion for evaluation. Furthermore, in order to ascertain the impact of the microspheres on the cement matrix, a series of physical and mechanical tests, thermogravimetric analysis, calorimetry, setting time assessments, and phase formation investigations (X-ray diffraction) were conducted on pastes and mortars incorporating maltodextrin and chitosan microspheres. Ultimately, the findings from these assessments were utilized to fabricate concrete incorporating microspheres, which was then evaluated for chloride and CO₂ diffusion. The results demonstrate the capacity for realkalinization and the structural integrity of the maltodextrin microspheres. The chitosan microspheres underwent chemical modification to achieve the same capacity, demonstrating favorable outcomes for realkalization in carbonated mortars with a low water/cement ratio. The concretes containing maltodextrin microspheres produced with calcium and aluminum hydroxides demonstrated enhanced alkalinization capacity, reducing CO₂ Kacel by 99%. Additionally, they exhibited superior outcomes in terms of corrosion potential and electrical resistivity, with only constraints associated with delayed hydration reactions. Consequently, microspheres can be regarded as a viable corrosion inhibitor.