DISCENTE: MADSON LUCAS DE SOUZA
DATA: 29/11/2024
HORA: 10:30
LOCAL: meet.google.com/yfd-zvss-oxj
TÍTULO:
RHEOLOGICAL, MICROSTRUCTURAL, MECHANICAL AND DURABILITY PROPERTIES OF BSSF SLAG ALKALI-ACTIVATED BINDERS AND CONCRETES FOR INTERLOCKING BLOCKS PRODUCTION
RESUMO:
The civil construction and infrastructure sectors significantly contribute to global environmental impacts. A major contributor to this impact is from the use of Portland cement. In this context, alkali-activated binders (AABs) have emerged as promising sustainable alternatives to Portland cement binders. These materials are synthesized through the alkaline activation of aluminosilicate sources (precursors), usually industry wastes, in combination with a concentrated alkaline solution (activators). While fly ash, blast furnace slag, and metakaolin are well-studied precursors, steel slag remains underexplored. Particularly, Baosteel's Slag Short Flow slag (BSSF), generated through advanced cooling processes of Basic Oxyne Furnace (BOF) slag, shows a potential use as a precursor in AABs and as an aggregate in concretes due to its chemical composition and availability. The general objective of this research is to investigate the impact of incorporating steel industry coproducts, specifically BSSF, as precursors on the rheological, mechanical, microstructural and durability behavior of alkali-activated materials applied to paving. For that, a comprehensive experimental framework was developed, encompassing precursor characterization, formulation optimization, and material performance evaluation and was divided in four phases. The first phase involved analyzing various industry coproducts to identify their suitability as AABs precursors. Characterization techniques such as XRF, XRD, and laser granulometry were employed. Based on these analyses, BSSF and fly ash (FA) were selected as the most promising precursors for further investigation. The second phase focused on optimizing AAB formulations (FA and BSSF-based) by varying key parameters such as alkali content (N/B), silica modulus (S/N), precursor ratios, and curing conditions. Compressive strength tests and analysis of efflorescence formation were conducted. It was observed that increasing the BSSF content generally led to a reduction in compressive strength, except for AABs containing 75% BSSF, which demonstrated optimal performance. Notably, efflorescence was found to have no impact on compressive strength. The third phase involved a fundamental analysis of the impact of replacing FA with BSSF on the rheology, structural build-up, and microstructure of AABs. Rheological tests, including mini slump, flow sweep, small amplitude oscillatory shear (SAOS), and setting time measurements, were conducted followed by microstructural analyses by techniques such as XRF, XRD, FTIR, TGA, SEM, and N2 sorption. The results indicated that increasing BSSF content improved workability, reduced viscosity, and accelerated hardening due to the higher calcium content. SAOS tests revealed faster gel formation and enhanced stiffness in BSSF-rich AABs. Additionally, microstructural analyses highlighted significant changes in the composition and structure of the AABs as BSSF content increased, which was associated with the formation of C-A-S-H and C-S-H gels. In the fourth phase, the use of BSSF as an aggregate in AACs was explored. Rheometry and slump tests were performed alongside with compressive strength, modulus of elasticity (using different methods), absorption, chloride migration and electrical resistivity. For comparison, these tests were also performed on Portland cement concretes. The study concluded with the validation of AAC formulations through the production and testing of interlocking blocks, according to NBR 9781 (2013). These blocks underwent visual inspection, compressive strength, and absorption tests, confirming their suitability for practical applications. All concretes exhibited self-compacting behavior, with AACs showing higher viscosity and greater mixing energy requirements. The incorporation of BSSF aggregates enhanced the compressive strength and modulus of elasticity. All AACs met the specifications for interlocking blocks.
MEMBROS DA BANCA:
Orientador - 3058783 - LUCAS FEITOSA DE ALBUQUERQUE LIMA BABADOPULOS
Examinador Interno - 3060676 - HELOINA NOGUEIRA DA COSTA
Examinador Externo ao Programa - JUCELINE BATISTA DOS SANTOS BASTOS - IFCE
Examinador Externo à Instituição - ANTONIN FABBRI - ENTPE
