Banca de DEFESA: YURI SOTERO BOMFIM FRAGA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : YURI SOTERO BOMFIM FRAGA
DATE: 02/08/2023
TIME: 09:00
LOCAL: PECC
TITLE:

EFFECT OF FUNCTIONALIZATION OF NANOSILICA WITH DIFFERENT DEGREES OF DENSIFICATION OF SHRINKAGE REDUCING ADDITIVE IN CEMENTITIOUS COMPOSITIES

KEY WORDS:

Portland Cement; Functionalization; Colloidal Nanosilica; Autogenous Shrinkage

PAGES: 164
BIG AREA: Engenharias
AREA: Engenharia Civil
SUBÁREA: Construção Civil
SPECIALTY: Materiais e Componentes de Construção
SUMMARY:

The nanosilica (NS) provides changes in the microstructure of cementitious composites such as densification of the cementitious matrix that result in increased of mechanical strength and durability of these composites. Despite this improvement, the NS contributes to potentiate undesirable effects in cementitious composites, such as autogenous shrinkage. Thus, this research project aims to verify the effect of NS functionalization with different mass ratios of shrinkage reducing additive (SRA) in Portland cement pastes. Four functionalized nanosilicas were produced, one with amine groups (NSFA) and three with different mass ratios of ARR/NSFA (5%, 10% and 15%), called NSFArr. These samples were characterized using dynamic light scattering (DLS), Zeta potential, thermogravimetric analysis (TGA), infrared spectroscopy (FTIR) and nuclear magnetic resonance (²⁹SiNMR). The properties of six different pastes and microconcretes were investigated, one being produced only with Portland cement CP V-ARI and five replacing 1% of Portland cement by NS or the functionalized nanosilicas. Time zero, autogenous shrinkage, heat of hydration, compressive strength at 2, 7 and 28 days of hydration, amount of CH and C-S-H through X-ray diffraction (XRD), TGA and FTIR, as well as the porosity at 28 days of hydration through the mercury intrusion porosimetry test (PIM) were analyzed. It was possible to observe changes in the hydration kinetics with a delay in the induction period of the pastes with NSFArr compared to the other pastes, which did not influence the mechanical performance at the initial ages. In addition, NSFArr mitigated the autogenous shrinkage, increased the pozzolanic reaction and promoted an increase in mechanical strength between 7 and 28 days. It was possible to conclude that the functionalization method used was efficient to promote the coupling of the SRA functional groups on the surface of the nanoparticles and that the mass ratio of 10% was the one that presented the most promising results for use in cementitious composites.

COMMITTEE MEMBERS:
Presidente - 1734221 - JOAO HENRIQUE DA SILVA REGO
Interna - 1573495 - VALDIRENE MARIA SILVA CAPUZZO
Externo à Instituição - MOISÉS FRÍAS ROJAS - IETcc
Externa à Instituição - BERENICE MARTINS TORALLES - UEL