Sustainable alkaline cements with different Ca contents for stabilisation of copper mine tailings Elmira Khaksar Najafi, Tiago Miranda, Cise Unluer, Shahram Pourakbar, Hamid Reza Manaviparast, Pedro Tavares, Nuno Cristelo Journal of Cleaner Production, 2026 The sustainable management of mine tailings is a growing challenge for the mining sector, with substantial environmental risks and long-term storage costs. This study explores the valorisation of copper mine tailings through the production of alkali-activated mortars (AAMs) using low-calcium fly ash and high-calcium blast furnace slag as precursors. A five-level Central Composite Design within the Response Surface Methodology framework was applied to optimise three key mix parameters: precursor/solid ratio, activator/precursor ratio, and sodium silicate/hydroxide ratio. Uniaxial compressive strength testing was supported by microstructural analyses (Scanning Electron Microscopy, Energy-Dispersive Spectroscopy, X-Ray Diffraction, Fourier Transform Infrared Spectroscopy) to correlate strength with gel composition and morphology. Optimal slag-based mixes achieved compressive strengths up to 15 MPa, driven by C-(A)-S-H and N-(C)-A-S-H gel formation, whereas ash-based systems reached 12 MPa, with performance strongly dependent on silicate/hydroxide ratio and N-A-S-H gel development. Response Surface modelling accurately predicted compressive strenght (R 2 > 0.87) and identified precursor chemistry as a key determinant of activator efficiency. These results demonstrate the feasibility of designing high-performance, tailings-based AAM, while reducing reliance on Portland cement, contributing to circular economy goals through CO 2 emission reduction and industrial waste reuse. A screening LCA indicates 0.24–0.37 kg CO 2 e kg −1 of paste for optimised mixes, 56–71 % lower than an OPC benchmark under declared assumptions. The work is framed as a screening-level optimisation and comparison (FA vs BFS) with explicit model limits and microstructural corroboration. The findings provide a robust optimisation approach for tailoring sustainable binder systems to diverse tailings chemistries. • Alkali-activated binders stabilise copper tailings using FA and BFS. • Precursor fraction and activator chemistry control early-age strength. • Inline figures and model diagnostics (incl. parity plots) improve clarity. • XRD, FTIR and SEM-EDS evidence support gel formation mechanisms. • Ambient validation, durability and leaching tests defined as next steps.
Construction and characterization of a structural unit for modular artificial reefs Fábio Cruz, Isabel B. Valente, Tiago Miranda, Eduardo B. Pereira Structures, 2025 In recent years, the development of artificial reefs has gained significant importance, driven by the need to preserve marine ecosystems and promote the sustainability of human activities. These structures increasingly incorporate complex geometries to enhance their functionality and ecological integration, requiring advanced modelling approaches, more flexible and innovative construction methods. Given the need to address this increasing complexity, this study focuses on the construction and experimental characterization of a modular artificial reef unit using two alternative structural systems: reinforced concrete (RC) and engineered cementitious composite (ECC). The module development involved the use of 3D-printed moulds to optimize fabrication and reduce costs. Full-scale structural tests, including bending tests, were conducted to evaluate stiffness, strength, ductility, and failure modes of the modules. The results indicate that the RC unit exhibited superior structural performance, with higher load capacity, greater deformation, and higher initial stiffness compared to the ECC unit. The failure modes differed between the systems, with the RC unit failing due to cracking of the central bulb and failure of the reinforcement lashing, while the ECC unit failed due to separation of one of the loaded limbs. This study also highlights the feasibility of 3D printing for cost-effective and sustainable mould production.
Agricultural Waste: The Picture of European Union Countries Margarida Soares, Z. Genisheva, Tiago Miranda, Eduardo Pereira, C. Vilarinho, Joana Carvalho Journal of Sustainability Research, 2025 In today’s global landscape, a key challenge is balancing rapid population growth with sustainable agro-waste management. As demand for food and agricultural products rises, so does the volume of waste across the supply chain. It is vital to understand how demographic expansion affects waste generation, quantify this waste, and identify its geographic distribution within the European Union (EU). This study provides a statistical analysis of waste from agriculture, forestry, and fishing in the EU and assesses agricultural land use linked to crop production. By mapping this data across member states, it establishes a foundation for future research on the links between agricultural activity, land use, and waste. This will inform strategies for waste prevention, recovery, and valorization at both national and European levels. The study’s relevance lies in its ability to guide policymakers, researchers, and industry. Identifying countries with the highest waste output enables targeted interventions to foster circular
Engineering-Driven Approach for the Structural Design of Geometrically Complex Modular Artificial Reefs Fábio Cruz, Isabel B. Valente, Dmytro Maslov, Tiago Miranda, Eduardo B. Pereira Applied Sciences Switzerland, 2025 Over the years, artificial reefs with diverse forms and functions have become increasingly important in maritime engineering and ecosystem restoration plans, with socio-economic and ecological impacts on marine ecosystems. However, due to the increasing complexity of designs and durability requirements, the current structural design approaches lack adequate documentation and standardization. This work addresses this challenge by detailing an engineering-driven approach for the structural design of artificial reef structures made of reinforced concrete or composite steel and concrete. This study establishes the premises for the structural design, followed by the quantification of actions based on standards and recommendations for marine structures. Hydrodynamic and numerical models were utilized to assess the effects of these actions on the structure. A cross-section organic design was then implemented, followed by a parametric study exploring various structural and material combinations for optimization. This study validates the developed design methodology combining hydrodynamic actions and strength analysis for complex modular artificial reef structures of 3 to 15 m size, specifically tailored for open waters. The results confirm the applicability and reliability of the developed design methodology, demonstrating its potential for guiding future numerical and experimental studies on modular artificial reef structures in open waters.
Development of Half-Sandwich Panels with Alkali-Activated Ceramic and Slag Wastes: Mechanical and Thermal Characterization Norma Gaibor, Dinis Leitão, Ana Briga-Sá, Tiago Miranda, Nuno Cristelo, Eduardo N. B. Pereira, Vítor M. C. F. Cunha Buildings, 2025 This paper presents the development of two solutions for sandwich panels composed of a thin-layer alkali-activated composite (AAc) layer and a thicker insulation layer, formed by extruded polystyrene foam or expanded cork agglomerate (panels named APXPS or APICB, respectively). The AAc combined ceramic waste from clay bricks and roof tiles (75%) with ladle furnace slag (25%), activated with sodium silicate. The AAc layer was further reinforced with polyacrylonitrile (PAN) fibers (1% content). The mechanical behavior was assessed by measuring the uniaxial compressive strength of cubic AAc specimens, shear bond strength, pull-off strength between the AAc layer and the insulation material, and the flexural behavior of the sandwich panels. The thermal performance was characterized by heat flux, inner surface temperatures, the thermal transmission coefficient, thermal resistance, and thermal conductivity. Mechanical test results indicated clear differences between the two proposed solutions. Although APXPS panels exhibited higher tensile bond strength values, the APICB panels demonstrated superior interlayer bond performance. Similar findings were observed for the shear bond strength, where the irregular surface of the ICB positively influenced the adhesion to the AAc layer. In terms of flexural behavior, after the initial peak load, the APXPS exhibited a deflection-hardening response, achieving greater load-bearing capacity and energy absorption capacity compared to the APICB. Finally, thermal resistance values of 1.02 m2 °C/W and 1.14 m2 °C/W for APICB and APXPS were estimated, respectively, showing promising results in comparison to currently available building materials.
Development and characterization of structural connections for modular artificial reefs Fábio Cruz, Isabel B. Valente, Filipa Monteiro, Dmytro Maslov, Tiago Miranda, Eduardo B. Pereira Ocean Engineering, 2025 Artificial reefs and other marine structures are becoming relevant components of coastal engineering interventions and ecosystems restoration plans. Their construction and deployment, as well as durability, are challenging, and the available engineering solutions are limited and lack validation. Giving the need to address the increasing complexity of artificial reef designs and their durability requirements, this work focuses on the development and characterization of structural connections for modular artificial reef marine structures, with application to a case study. An extensive experimental program was conducted to assess their feasibility and performance, including the materials characterization and structural response. The materials and systems developed included hot-dip galvanized steel, engineered cementitious composites and knitted textiles in different layouts and combinations. The findings contribute to advancing the design of durable and efficient connections for modular artificial reef structures, as well as for other similar emerging structural applications of submerged ocean constructions. • Innovative connection systems for modular artificial reefs were developed and validated. • Materials included concrete, cementitious composites, steel, epoxy and knitted textile preforms. • Flexural tests showed ductile responses and high strengths for modular connections.
A Comprehensive Review on Clay Soil Stabilization Using Rice Husk Ash and Lime Sludge Hamid Reza Manaviparast, Nuno Cristelo, Eduardo Pereira, Tiago Miranda Applied Sciences Switzerland, 2025 Soil stabilization is vital in construction to enhance soil strength and durability. While conventional stabilizers like cement and lime improve soil properties, they contribute to significant carbon emissions. Given their widespread use, exploring eco-friendly alternatives is crucial. This review examines rice husk ash (RHA) and lime sludge (LS) as sustainable substitutes. Previous studies have evaluated their effectiveness in stabilizing clay soil, but a more application-focused approach, along with a detailed cost and sustainability evaluation, is needed. Standard Proctor compaction, California Bearing Ratio, and unconfined compression strength tests were analyzed from the existing literature to determine the optimal ratio of these additives for maximum soil strength. The results were compared to determine the most effective quantities of RHA and LS, either separately or combined, and inferences about their influences on clay soil attributes were drawn. Additionally, comprehensive life cycle assessment (LCA) and cost evaluation were reviewed. Finally, it was concluded that increasing the amounts of RHA and LS and combining them enhanced the strength of clay soil. Moreover, using RHA and LS for soil stabilization proved to be a cost-effective alternative to traditional methods, providing economic and environmental advantages.
A multidisciplinary engineering-based approach for tunnelling strengthening with a new fibre reinforced shotcrete technology Joaquim Barros, Hugo Costelha, David Bento, Nelson Brites, Rui Luís, Hugo Patrício, Vitor Cunha, Luís Bento, Tiago Miranda, Paulo Coelho, Miguel Azenha, Carlos Neves, Hamidreza Salehian, Gonçalo Moniz, Mojtaba Nematollahi, Abel Teixeira, Mahsa Taheri, Anton Mezhyrych, Emad Hosseinpour, Tales Correia, Hamid Kazemi, Omid Hassanshahi, Alireza Rashiddel, Briar Esmail Tunnelling and Underground Space Technology, 2024
AEROS: Oceanographic Hyperspectral Imaging and Argos-Tracking CubeSat Proceedings of the International Astronautical Congress Iac, 2022
Submarine Cables as Precursors of Persistent Systems for Large Scale Oceans Monitoring and Autonomous Underwater Vehicles Operation Marcos Tieppo, Eduardo Pereira, Laura Gonzalez Garcia, Margarida Rolim, Emanuel Castanho, Anibal Matos, Antonio Silva, Bruno Ferreira, Maria Pascoal, Eduardo Almeida, Filipe Costa, Fred Zabel, Joao Faria, Jose Azevedo, Jose Alves, Jose Moutinho, Luis Goncalves, Marcos Martins, Nuno Cruz, Nuno Abreu, Pedro Silva, Ruben Viegas, Sergio Jesus, Tania Chen, Tiago Miranda, Alan Papalia, Douglas Hart, John Leonard, Maha Haji, Olivier de Weck, Peter Godart, Pierre Lermusiaux Oceans Conference Record IEEE, 2022
Coastal Ocean Observing and Modeling Systems in Brazil: Initiatives and Future Perspectives Guilherme Franz, Carlos A. E. Garcia, Janini Pereira, Luiz Paulo de Freitas Assad, Marcelo Rollnic, Luis Hamilton P. Garbossa, Letícia Cotrim da Cunha, Carlos A. D. Lentini, Paulo Nobre, Alexander Turra, Janice R. Trotte-Duhá, Mauro Cirano, Segen F. Estefen, José Antonio M. Lima, Afonso M. Paiva, Mauricio A. Noernberg, Clemente A. S. Tanajura, José Luiz Moutinho, Francisco Campuzano, Ella S. Pereira, André Cunha Lima, Luís F. F. Mendonça, Helder Nocko, Leandro Machado, João B. R. Alvarenga, Renato P. Martins, Carina Stefoni Böck, Raquel Toste, Luiz Landau, Tiago Miranda, Francisco dos Santos, Júlio Pellegrini, Manuela Juliano, Ramiro Neves, Andrei Polejack Frontiers in Marine Science, 2021
Development of alkali activated ceramic residue and fly ash blends N. Gaibor, D. Leitão, T. Miranda, N. Cristelo Wastes Solutions Treatments and Opportunities III Selected Papers from the 5th International Conference Wastes Solutions Treatments and Opportunities 2019, 2020
Electrical resistivity of sustainable fiber reinforced concretes for smart marine structures IABSE Symposium Guimaraes 2019 Towards A Resilient Built Environment Risk and Asset Management Report, 2019
Rock quality designation 3D modelling using geostatistics: A tungsten Portuguese deposit case study 53rd U S Rock Mechanics Geomechanics Symposium, 2019
Comportamento ao fogo de blocos de terra comprimida Rehabend, 2018
Improvement of a clayey soil with alkaline activation of wastes Wastes Solutions Treatments and Opportunities II Selected Papers from the 4th Edition of the International Conference Wastes Solutions Treatments and Opportunities 2017, 2018
SQI - A quality assessment index for rock slopes Geotechnical Engineering for Infrastructure and Development Proceedings of the Xvi European Conference on Soil Mechanics and Geotechnical Engineering Ecsmge 2015, 2015
Application of Markov chains in the prediction of rock slopes degradation Geotechnical Engineering for Infrastructure and Development Proceedings of the Xvi European Conference on Soil Mechanics and Geotechnical Engineering Ecsmge 2015, 2015
Prediction of the mechanical compressive behavior of granite using intelligent tools Rock Engineering and Rock Mechanics Structures in and on Rock Masses, 2014
Vibration propagation in discrete element particle models of rock Rock Engineering and Rock Mechanics Structures in and on Rock Masses, 2014
Analysis of the performance of an evolutionary computation algorithm in the identification of geomechanical parameters in underground works Rock Engineering and Rock Mechanics Structures in and on Rock Masses, 2014
Prediction of hard rock TBM penetration rate based on data mining techniques 18th International Conference on Soil Mechanics and Geotechnical Engineering Challenges and Innovations in Geotechnics Icsmge 2013, 2013
Models for geomechanical characterization of the rock mass formations at DUSEL using data mining techniques 46th US Rock Mechanics Geomechanics Symposium 2012, 2012
Design of spread foundations on rock masses according to Eurocode 7 Harmonising Rock Engineering and the Environment Proceedings of the 12th ISRM International Congress on Rock Mechanics, 2012
Nondestructive evaluation of granite building stones and relation with key mechanical parameters Harmonising Rock Engineering and the Environment Proceedings of the 12th ISRM International Congress on Rock Mechanics, 2012
Relation between tensile and compressive engineering properties of granites Harmonising Rock Engineering and the Environment Proceedings of the 12th ISRM International Congress on Rock Mechanics, 2012
Prediction of rockburst based on an accident database Harmonising Rock Engineering and the Environment Proceedings of the 12th ISRM International Congress on Rock Mechanics, 2012
Development of models for geomechanical characterization using data mining techniques applied to a database gathered in underground structures 45th US Rock Mechanics Geomechanics Symposium, 2011
Nondestructive evaluation of granite building stones and relation with key mechanical parameters Harmonising Rock Engineering and the Environment, 2011
Design of spread foundations on rock masses according to Eurocode 7 Harmonising Rock Engineering and the Environment, 2011
Relation between tensile and compressive engineering properties of granites Harmonising Rock Engineering and the Environment, 2011
Prediction of rockburst based on an accident database Harmonising Rock Engineering and the Environment, 2011
Bayesian framework for the deformability modulus updating in an underground structure 42nd U S Rock Mechanics 2nd U S Canada Rock Mechanics Symposium, 2008
Numerical analysis of the Venda Nova II powerhouse complex Applications of Computational Mechanics in Geotechnical Engineering Proceedings of the 5th International Workshop on Applications of Computational Mechanics in Geotechnical Engineering, 2007
Inverse analysis on two geotechnical works: A tunnel and a cavern Applications of Computational Mechanics in Geotechnical Engineering Proceedings of the 5th International Workshop on Applications of Computational Mechanics in Geotechnical Engineering, 2007
