Banca de QUALIFICAÇÃO: NATHALIA SOUZA TEIXEIRA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : NATHALIA SOUZA TEIXEIRA
DATE: 23/03/2026
TIME: 14:00
LOCAL: Videoconferência Google Meet
TITLE:

Synthesis and Characterization of Geopolymers from Natural Materials and Industrial Waste for Supplementary Cementitious Materials

KEY WORDS:

Geopolymers; Cements; Strength; Waste; (CO2); Covering kaolin; Perlite; Homogeneity.

PAGES: 100
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Cerâmicos
SUMMARY:

The growth in the production of cementitious materials in the construction industry has significantly contributed to the increase in carbon dioxide (CO₂) emissions into the atmosphere. Among these materials, Portland cement stands out, as its production process involves high temperatures and high energy consumption. In this context, geopolymers emerge as a promising alternative to conventional cementitious materials due to the reduction of CO₂ emissions during their production. In addition, they exhibit relevant properties such as high compressive strength, thermal insulation, and the possibility of being synthesized using natural materials or residues rich in aluminosilicates. In this work, geopolymers were synthesized from different residues and natural materials, such as overburden kaolin, white kaolin, yellow kaolin, kaolin residue, Brazilian metakaolin, glass powder, coal fly ash, expanded perlite, diatomite, and aluminum silicate, aiming at their application in cementitious materials. The materials were characterized using different techniques in order to determine their structural, textural, and morphological properties. X-ray diffraction (XRD) allowed the identification of crystalline phases in some samples and confirmed that the geopolymers Geo.Res.Cau, Geo.3, Geo.4, Geo.Cober.3, and Geo.Perlite presented amorphization in the network. From the FTIR spectra, the presence of Si–O–Si bonds and hydroxyl groups (O–H) was confirmed, and it was observed that some materials showed low formation of sodium carbonate (Na₂CO₃), associated with efflorescence, particularly in Geo.Res.Cau and Geo.Perlite. Scanning electron microscopy (SEM) micrographs allowed the visualization of the amorphous nature of the geopolymers, especially for Geo.Res.Cau, Geo.3, Geo.4, Geo.Cober.3, and Geo.Perlite. The specific surface area determined by the BET method showed that Geo.3, Geo.4, Geo.Res.Cau, and Geo.Cober.3 presented lower surface area, indicating that the precursor residue contributed to lower porosity and consequently higher density. Furthermore, transmission electron microscopy (TEM) analysis allowed the investigation of the internal structure of some samples, confirming the presence of amorphization and porosity in the geopolymers. From the NMR results, the aluminum coordination in the network was determined through spectral deconvolution, identifying tetrahedral and octahedral linkages. For the geopolymers Geo.4, Geo.Res.Cau, and Geo.Perlite, a predominance of tetrahedral linkages was observed, indicating better network homogenization. Thus, the calculations were performed to quantify the relative proportion of the different structural environments of aluminum, highlighting tetrahedral coordination and a higher degree of polymerization in the structure for Geo.4, Geo.Res.Cau, and Geo.Perlite. Therefore, the geopolymers most suitable for application as supplementary cementitious materials were Geo.4, Geo.Perlite, and Geo.Res.Cau, demonstrating greater network homogenization, absence of secondary phases, and promising performance due to the amorphous nature and reactivity of their precursor materials, making them suitable for use in high-performance cementitious materials in the construction industry.

COMMITTEE MEMBERS:
Externo à Instituição - ANA PAULA DE CARVALHO TEIXEIRA - UFMG
Presidente - 349770 - DULCE MARIA DE ARAUJO MELO
Interno - 1350249 - RUBENS MARIBONDO DO NASCIMENTO
Interna - 1308577 - SIBELE BERENICE CASTELLA PERGHER