Concrete and Circular Economy

Table of Contents

1. Eco-design and Eco-Construction

   1. Frontmatter

   2. Hygrothermal Properties of Compacted Bio-Based Blocks (CBB) Made from Alkali-Activated Binder and Flax Shives

      Laila Benbahloul, Jonathan Page, Chafika Djelal, Mohamed Waqif, Latifa Saâdi

      Abstract

      Bio-based materials are increasingly used in construction due to their excellent hygrothermal performance. They help manage energy consumption in buildings by contributing to thermal insulation, which reduces reliance on heating and cooling systems. This study aims to explore the potential of using an alkali-activated binder (AAB) to develop Compacted Bio-based Blocks (CBB) made from flax shives for thermal insulation in buildings. Four AABs were used, combining metakaolin (MK) and granulated blast furnace slag (GBFS) in different proportions (100% MK, 70% MK - 30% GBFS, 30% MK - 70% GBFS and 100% GBFS), and activated by a sodium silicate solution (SiO₂/Na₂O ratio of 1.5 and 35% by mass). These binders enabled the manufacture of two block types, L-BBC and M-BBC, with bulk densities of 360 kg/m³ and 500 kg/m³, respectively. The parameters evaluated included apparent bulk density, thermal conductivity, and moisture buffer value (MBV). The results show that the blocks manufactured have an apparent density of between 360 and 520 kg/m³, a thermal conductivity ranging from 0.11 to 0.13 W/(m.K), and a moisture regulation capacity (MBV) greater than 2 g/(m².%RH). The hygrothermal properties of the blocks are mainly influenced by the amount of flax shives in the mix. Increasing the Shives/AAB ratio leads to a rise in intergranular porosity, resulting in lower bulk density and thermal conductivity, and improved MBV values. Furthermore, the type of binder had minimal impact on the overall hygrothermal performance of the blocks. In conclusion, bio-based materials with alkali-activated binders exhibit promising hygrothermal properties, making them a viable solution for addressing the energy and environmental challenges in the construction industry.

   3. Reuse of Reservoir Sediments as Road Layer Material

      Sameh Anibi, Souhir Ellouze, Moncef Zairi

      Abstract

      Sedimentation in reservoirs causes environmental and economic issues. When dredging becomes necessary, reuse of the dredged sediments may reduce the high costs and environmental impacts associated with this process, reduce dependency on natural materials and support the concept of resources circular management.

      The main object of this research is to explore the possibility of using sediments from the Siliana dam reservoir, which has reached its half-life, in road construction. Samples taken from the sediments undergo geotechnical, and mechanical characterization. The sediments are classified considering their physical properties, including water content, grain size distribution, liquid and plastic limits, organic matter content, and methylene blue adsorption, as well as the standard Proctor compaction test and the California Bearing Ratio (CBR) test.

      The studied samples are mainly composed of fine sand, silt, and clay, with medium to high plasticity and low organic matter content. These sediments have geotechnical characteristics that make them unsuitable for direct use as embankments or as road foundation layers. Indeed, their high water content and low bearing capacity require improvements to meet road construction standards.

      The incorporation of different percentages of hydrated lime into the Siliana dam sediments suggests that an addition of 5% hydrated lime is sufficient to achieve the desired bearing capacity.

   4. Concrete Made from Vegetable Shells: Case of Palm Shell

      M. A. Serifou, A. Konin

      Abstract

      This study investigates the impact of the characteristic of palm shells on mechanical properties of biomass concrete. Seven types of concrete were made, six of those concretes are composed of substitutions with different proportions of palm nut shells and one formulated type served as a control concrete. The variation of mechanical properties of these concretes according to the curing time was studied. The research findings indicate that mechanical properties of the specimens increase with curing time. However, the substitution of palm nut shell in concrete leads to a decrease in the mechanical properties of concrete. these properties decrease with increasing substitution percentage. Furthermore, the splitting tensile strength measured at twenty-eight days is 2.05 MPa (control concrete) and drops to 1.08 MPa for 20% crushed shells then decreases to 0.44 MPa for 100% of whole shell. The flexural strength decreases with the increase in the proportion of shell. This study highlights the potential for integrating palm nut shells into concrete.

   5. Effects of lime and fibers on ECB properties

      Houcem Trabelsi, Souhir Elouze, Ines Garsellaoui, Stéphanie Bonnet

      Abstract

      Soil stabilization is essential in geotechnical engineering to improve the mechanical and durability properties of soils. This study investigates the combined effects of lime and natural fibers on soil stabilization, focusing on compressive strength and shrinkage behavior. Various lime contents (0%, 4%, 6%, and 8%) and fiber proportions (0%, 0.5%, and 1%) were used. Samples were molded into standardized cylindrical shapes and cured for 7 and 14 days under controlled conditions (22 °C, 70% relative humidity). Compressive strength tests followed the XP P 13-901 (2001) standard, while shrinkage behavior was analyzed through precise dimensional measurements. Results showed that while moderate lime content (6%) increased compressive strength due to pozzolanic reactions, excessive lime led to reduced strength. Fibers enhanced mechanical properties by acting as crack arrestors and reducing shrinkage. The study highlights the importance of optimizing lime-fiber ratios to achieve durable and stable soils.

   6. Characterization of Dam Sediments for Their Potential Use in Ceramic Production

      Assia Boukhili, Rakia Shabou, Ali Ellouze, Hassib Tounsi

      Abstract

      Sustainable dam sediment management is one area of the circular economy, which aims to optimize resources and reduce environmental impact through innovative eco-friendly solutions for environmental preservation and resource recovery. This study is a laboratory investigation of the Bir M’Cherga dam sediment (S) to determine its physical, geotechnical, environmental, structural, and thermal characteristics to investigate the possibility of reuse as a ceramic material. Geotechnical properties show that the sediment is a highly plastic clay composed of 6% clay, 50% silt, and 44% sand. Environmental characterization classifies the sediment into low organic matter, and the structural and physical characterizations revealed that (S) contains primarily calcite, quartz, kaolinite, and illite. X-Ray Fluorescence Spectrometry (XRF) revealed that the most abundant oxides are SiO₂, Al₂O₃, Fe₂O₃, and CaO, while SO₃, MgO, and alkali (K₂O, Na₂O) are only present in small quantities. Infrared spectroscopy (FTIR) results show relatively broad absorption bands localized around 3500 cm^-1, associated with phyllosilicates such as kaolinite and illite. Dilatometric analysis indicates a sintering start temperature of 1025°C. This characterization identifies the potential utilization of sediment in ceramic applications, including tiles and bricks, in accordance with circular economy principles.

   7. Exploratory Study of the Thermal and Mechanical Performances of an Agro-Concrete Using Reed as a Biosourced Aggregate

      Laura Prévitali, Thouraya Salem, Antonin Fabbri, Teddy Fen-Chong

      Abstract

      The carbon impact of construction materials, such as Portland cement, plays a major role in greenhouse gas emissions. Additionally, the growing demand for air conditioning, caused by rising temperatures due to climate change, intensifies these emissions. In this context, biosourced materials with low carbon binders can be a promising solution.

      This paper presents an exploratory study on the potential use of reed as a bio-based aggregate for the production of agro-concretes with good mechanical strength while keeping interesting thermal properties.

      In particular, encouraging results were observed regarding the thermal behavior, showing a conductivity of around 0.1 W/mK for a density of approximately 1000 kg/m3. However, a better understanding of the reaction processes between the reed and the concrete was found necessary to develop formulations that optimize also mechanical behavior. For that purpose, Vicat test was carried out using either pure water or reed leachate. Results underlined a slight delay in setting of the studied cement. These promising preliminary results pave the way for a more in-depth study, with the aim of optimizing the reed concrete mix design.

   8. Long-Term Durability of Treated Alfa Fibers Based-Cementitious Materials

      Soukaina Ajouguim, Jonathan Page, Chafika Djelal

      Abstract

      The incorporation of Alfa fibers into a cementitious matrix leads to an improvement in the mechanical properties of the composite, particularly its flexural strength. However, degradation of the Alfa fibers over time has been noted due to the high alkalinity of the cementitious environment. In our previous work, five treatments were selected: Chemical (alkaline and hydrothermal), biological (enzymatic), physical (ultrasonic), and mineral coating (sulfoaluminate cement). Although the most effective treatments were alkaline and hydrothermal, all the treatments provided fiber protection, improving the composite properties after 90 days. The aim of this study is to evaluate the performance and durability of mortars reinforced with treated Alfa fibers. Several tests were carried out to measure their behavior under environmental conditions. Mortars containing treated fibers showed that the mechanical performance of fiber-reinforced composites was maintained for up to 70 wetting/drying cycles. In conclusion, mortars with 1% vol. of Alfa fibers, 10 mm in length, treated with alkaline and hydrothermal methods, may be suitable for the development of materials for construction.

   9. Ballistic Impact and Blast Resistance of Alfa Reinforced Concrete

      Beya Tahenti, Zied Kammoun, Abderraouf Trabelsi

      Abstract

      Concrete is a widely used construction material renowned for its durability, workability, resistance, and cost-effectiveness. However, due to the increasing incidence of terrorist attacks and industrial accidents, there is a growing need to enhance concrete’s resistance to blast and ballistic impacts. This improvement is particularly important because concrete’s low tensile strength, compared to its compressive strength, makes it vulnerable under such extreme conditions. One method of improving the characteristics of concrete is by incorporating fibers into the mixture. Natural fibers are gaining interest in recent years due to the increasing demand for eco-friendly materials. In the current work, Alfa fibers were chosen. Eight different formulations with Alfa fiber content ranging from 0 to 100 kg/m³ were tested to assess the concrete’s properties. The measured mechanical properties showed that the inclusion of fibers slightly reduces compressive strength compared to ordinary concrete. However, flexural strength increased, with an optimal fiber content of 15 kg/m³. Ballistic resistance to bullet impacts was determined by measuring penetration depth, crater area, and the lost mass of the ejected fragment. The Alfa-reinforced concrete exhibited lower penetration depth, smaller crater area, and reduced lost mass compared to the reference concrete, with optimal values achieved with 15 kg/m³ of fibers. Moreover, the blast resistance of the proposed concrete was investigated. Experimental observations demonstrated that the inclusion of Alfa fibers enhanced the concrete’s response. The fibers were crucial for maintaining slab integrity by limiting crack propagation. The results support the use of Alfa fibers for reinforcing concrete in both civilian and military construction projects.

2. Sustainability of Materials and Structures

   1. Frontmatter

   2. New Insights on Sustainable Development in Construction

      Vyacheslav R. Falikman

      Abstract

      Global population growth and rapid urbanization demand enormous construction activities and building materials use. Current practices for the management of construction and structures are far from sustainable. Major facilitators for vital transformational change are identified as targeted improvements of codes and regulations, financial incentives together with research and education. Suggested operational instruments for design and integrity management of buildings and infrastructure include explicit consideration of circular economy, life cycle environmental impact assessments, biomimetics, increased use of advanced modelling and analysis methods as well as targeted utilization of new technologies, including data processing and storage technologies. Proposed by the Joint Committee on Structural Safety comprising experts from RILEM, IABSE, fib, CIB, ECCS, IASS, and joined by other organizations, GLOBE Consensus aims to sensitize the global community, including policy makers, industry leaders and decision makers, to the critical importance of the human-transformed environment for sustainable development at global and national levels. A significant step forward is the new fib Model Code for Concrete Structures, approved by the scientific community in 2023, which was developed as a unified design code for new and existing structures during their full life cycle. This document is the basis for the development of the next generation of codes and standards for the design of structural concrete worldwide.

   3. Image-Based Petrographic Analysis of Aggregates for Concrete Production

      Elske Linß, Patrick Hunhold, Daniel Garten, Galina Polte, Katharina Anding, Sandro Weisheit

      Abstract

      A method for automated petrographic analysis of natural aggregates using hyperspectral and colour (RGB) images and AI algorithms in the form of deep learning networks is presented. Certain constituents of aggregates can negatively affect the functional properties of the produced concrete and cause damage such as alkali-silica reaction or other damage patterns. The aim of the research was to reliably and automatically classify a selection of aggregates used in concrete production based on their spectral properties using RGB and hyperspectral images. For this purpose, RGB images were acquired using VIS line scan cameras and hyperspectral images of various natural aggregates were acquired using a hyperspectral camera in a selected spectral wavelength range from 960 to 1700 nm and analysed using segmentation, dimension reduction (multivariate data analysis methods) and AI application. A convolutional network (CNN) were used to classify the dimensionally reduced hyperspectral images and RGB images. As a result, a mean detection rate of 89–98% was achieved for classification into the three upper classes ‘non-critical’, ‘critical I’ and ‘critical II’. At the same time, concrete durability tests were carried out to investigate the damage potential of selected critical aggregates in concrete.

   4. Circularity of Construction Materials: Precedence Between Elements Based on Digital Models for Demolition

      André Mantelatto, Melody Njuguna, Artur Kuzminykh, Manuel Parente, José Granja, Miguel Azenha

      Abstract

      Modern demolition practices must comply with the principles of the circular economy, which in turn is enhanced by the adoption of digital technologies. Methodologies such as Building Information Modelling (BIM) facilitate an integrated approach to planning throughout the life cycle of a construction asset based on data and models. Challenges arise, particularly in the asset’s end-of-life phase, due to the absence of BIM models and limited interoperability. By conceptualizing an asset destined for demolition or renovation and adopting the viewpoint that it’s a repository of construction materials and products for potential reuse, the data can be harnessed to design a simplified deconstruction process. Making this data available in an open format that allows integration with secondary materials markets increases the possibility of planning the demolition process based on demand. This approach promotes circularity, encouraging the reuse of construction products, upcycling, and recycling of materials.

      This article describes a methodology for extracting asset data, facilitating the integration with optimization algorithms for demolition sequence. It illustrates an approach to applying a methodology for extracting precedence relationships between construction elements of a building from the geometric component of a BIM model, adapted for demolition. Thus, by adopting information management techniques, open data formats available, and IT tools and applications distributed publicly, the proposed methodology enhances optimization based on BIM models and is geared towards finding deconstruction activities complying with circular principles and sustainable practices.

   5. Influence of the Corrosion Process on the Formation of Crack Patterns in Reinforced Concrete: Experimental and Numerical Study

      O. Loukil, L. Adelaide, V. Bouteiller, M. Quiertant

      Abstract

      Extending the service life of reinforced concrete (RC) structures is paramount for sustainable infrastructure development, reducing environmental impact and minimizing resource consumption. This research investigates the degradation mechanisms of RC specimens exposed to chloride-induced corrosion, utilizing accelerated testing with impressed currents (50, 100, and 200 µA/cm2). By combining experimental measurements of corrosion product thickness and crack characteristics with numerical modeling, we aim to provide a comprehensive understanding of the degradation process. The validated numerical model will contribute to the development of predictive tools for assessing and enhancing the long-term performance of RC structures, thus promoting more sustainable construction practices.

   6. Concrete and Climate Change: Adapting to Rising Temperatures and Reducing Environmental Impacts

      Affes Hatem, Salem Nehme Georges

      Abstract

      This article examines the relationship between concrete and climate change. This relationship is often discussed from a one-sided perspective. A headline such as “The impact of concrete” or “Concrete and carbon emissions” is usually captivating. However, the impact of climate change, rising temperatures on concrete, and the urgent need for adaptation strategies are less discussed. As the built environment expands, concrete production is expected to contribute significantly to carbon emissions, exacerbating the climate crisis. On the other side of the equation, this rise in global temperature may require introducing special measures for concrete production. Emerging solutions like Cyment, a volcanic tuff-based additive, demonstrate how cement replacement can reduce clinker dependence while maintaining mechanical performance. This article discusses different approaches to reducing the environmental impact of concrete and the impact of global warming on the concrete industry. By understanding the challenges of concrete production in the context of climate change, this article aims to stimulate dialogue and action towards a more sustainable and resilient built environment.