Name: CATARINA VIEIRA BOTELHO
Publication date: 30/09/2025
Examining board:
Name |
Role |
|---|---|
| CARLA THEREZINHA DALVI BORJAILLE ALLEDI | Examinador Externo |
| GUILHERME BRAVO DE OLIVEIRA ALMEIDA | Examinador Externo |
| PATRICIO JOSE MOREIRA PIRES | Presidente |
| RONALDO PILAR | Coorientador |
Summary: This dissertation evaluates the technical feasibility of using ferronickel slag (FeNi) as a stabilizing agent and gradation corrector in two soils: a sandy soil (SL) and a silty fine soil (SR), with the aim of application in pavement layers. Mixtures with 30% and 60% FeNi, with and without 3% cement (CPIII and CFN50), were studied. The experimental program encompassed physical characterization (particle size distribution, specific gravity, organic matter content, Atterberg limits), chemical characterization (pH and cation exchange capacity), mineralogical characterization (XRF and XRD), and mechanical testing (compaction, California Bearing Ratio and swelling, as well as resilient modulus), with curing periods of 7 and 63 days. Results showed that FeNi is distinctly granular and of high density, shifting the mixtures towards a framework-controlled behavior and reducing plasticity, especially at 60% replacement. The SUCS, AASHTO and MCT classifications confirmed the trend toward more sandy materials. In compaction, the maximum dry unit weight increased, while the optimum moisture content decreased or remained stable with FeNi incorporation. The CBR increased significantly in SL mixtures with 3% cement, qualifying them as base course material, whereas pure SL and SL with FeNi but without cement met the requirements for subbase. In SR, relevant improvements occurred with FeNi, with or without 3% cement, placing the mixtures in the subbase category. Swelling remained very low in FeNi mixtures, complying with DNIT specifications. The resilient modulus increased with confining stress; in SR, the gain was governed by FeNi while cement had a secondary role, whereas in SL, cement was decisive and FeNi additionally contributed to the granular response. According to DNIT specifications, only SR+60%FeNi, with or without 3% cement, simultaneously met all requirements for subbase; considering only CBR and swelling, several SL formulations satisfied the base course criteria. It is concluded that FeNi is technically feasible as a component for base and subbase layers, with best performance at 60% content and in combination with low cement dosages, contributing to the valorization of by-products and to circular economy practices in pavement engineering.
Keywords: Ferronickel Slag; Soil Stabilization; Pavements; Resilient Modulus.
