Banca de DEFESA: NILSON SANTANA DE AMORIM JÚNIOR

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : NILSON SANTANA DE AMORIM JÚNIOR
DATE: 24/05/2024
TIME: 14:00
LOCAL: on-line /DCTM
TITLE:

Development of controlled release microparticles for realkalinization of carbonated mortars and concretes

KEY WORDS:

Microparticles, Microspheres, Durability, Carbonation, Controlled realkalization; Chloride diffusion

PAGES: 172
BIG AREA: Engenharias
AREA: Engenharia Civil
SUMMARY:

The corrosion of steel in reinforced concrete structures is one of the main contemporary socio-economic problems, leading to early deterioration of structures and significant economic losses. The corrosive process is triggered by the presence of aggressive agents that form electrochemical batteries. These damaging agents include chlorine ions and carbon dioxide (CO2). With regard to CO2, it reacts with cement hydration products in a process known as carbonation, resulting in the formation of calcium carbonate and a consequent decrease in pH, destabilizing the passivating film of the reinforcement and leaving it susceptible to corrosion. With this in mind, this study aims to develop microparticles that dissolve (on demand) and release an agent that regulates the pH of the matrix, providing a barrier to CO2 and/or a lifeline for reinforced concrete structures. The microparticles were produced using the biopolymers maltodextrin and chitosan as the matrix material, as well as calcium, sodium and aluminum hydroxides as re-alkalizing agents. After the production of the microspheres in a spray dryer, they were characterized to check their realkalization potential and integrity according to the pH variation of the medium. In addition, in order to verify the effect of the polymeric particles on the cement matrix, physical/mechanical tests, calorimetry, setting time and X-ray diffraction were carried out on pastes and mortars containing maltodextrin and chitosan microspheres. Finally, based on the results obtained in these tests, concretes with the incorporation of microspheres were molded and evaluated in terms of chloride and CO2 diffusion. The results indicate alkalization capacity and integrity for the maltodextrin microspheres. The chitosan microspheres required chemical modification to achieve the same capacity, showing satisfactory results for re-alkalinization in carbonated mortars with a low water/cement ratio. Although the maltodextrin microspheres interfered negatively with hydration and durability in relation to chloride attack, there was a gain in service life when considering the carbonate depth.

COMMITTEE MEMBERS:
Presidente - 1779028 - DANIEL VERAS RIBEIRO
Interno - 2137887 - CLEBER MARCOS RIBEIRO DIAS
Externa ao Programa - ***.706.834-** - JANIA BETANIA ALVES DA SILVA - UFRB
Externo à Instituição - FERNANDO DO COUTO ROSA ALMEIDA - UFMG
Externo à Instituição - DENILSON DE JESUS ASSIS - UNIFACS
Externa à Instituição - EDNA POSSAN