The large-scale use of recycled aggregates (RA) in high-grade construction applications is currently hindered by the high variability of their physical properties. Current quality control relies on manual sorting, which is labor-intensive and limits scalability. This study presents RAMSES (Recycled Aggregates Mass estimation and Segmentation), an automated framework based on deep learning, designed to bridge the gap between high-speed production and rigorous material characterization. A central contribution of this work is the introduction of a large-scale, publicly available dataset comprising 90,000 labeled and batch-weighed aggregate instances. This extensive dataset supports a strong statistical robustness across diverse RA compositions and serves as a benchmark for automated waste characterization. Using this dataset, RAMSES performs simultaneous instance segmentation and direct mass estimation from 2D images. By integrating a dual-branch architecture, the model effectively decouples morphological features from instance-dependent density factors. The framework achieves high precision in particle identification (mean Average Precision mAP@[0.5:0.95] = 0.84, mAP@0.5 = 0.91) and a 0.3% relative error in total mass prediction, which meets industrial requirements for batch monitoring. By providing a scalable alternative to manual inspection, this approach improves the consistency of RA-based concrete mixes, directly supporting the transition to a circular construction economy.

CO2 can be absorbed and mineralized as solid carbonates in a range of construction materials. Accurate measurement of CO2 content and uptake in cement-based and other construction products is important for the development as well as the certification of novel mineral carbonation products, processes, and practices. However, measurement is complex as samples can range from fine powders to blocks with varying levels of heterogeneity, different solid carbonate phases can be present, and measurement methods may require correction for interferences. When and where the CO2 content is measured is also important. Numerous techniques are available for measuring the solid CO2 content of a sample, from which the CO2 uptake can be calculated. Here, a critical review of the most relevant methods is presented; the most used methods are thermogravimetric and combustion analysis, however, diffraction-based, spectroscopic, wet-chemical, and other methods can also be used for this purpose. Advantages and disadvantages of the various test methods are discussed. Aspects of sample preparation, result interpretation, measurement limitations and possible interferences, as well as the use of complementary methods are highlighted. Important aspects of conversion of measured solid CO2 contents to calculated CO2 uptake are highlighted.

Among various strategies for CO2 mineralization, the carbonation of recycled concrete aggregate (RCA) has emerged as a highly promising approach. Atmospheric carbonation of RCA during storage on recycling platforms offers a low-cost solution, although it is a time-intensive process. Despite its potential, there is a notable lack of standardized test methods to evaluate the CO2 binding capacity and carbonation rate of RCA. This study introduces a novel test method, termed the Instantaneous Binding Rate (IBR) method, which measures the instantaneous CO2 binding rate of an RCA sample placed in a closed cell over a short duration. The binding rate is periodically measured over several weeks, and the total quantity of CO2 bound is calculated by integrating the time-dependent binding rate. The IBR method is validated using crushed mortar samples under natural carbonation conditions and is compared with conventional methods, including thermogravimetric analysis (TGA) and loss on ignition (LOI). A strong correlation is observed between the results of the three methods. Notably, both LOI and IBR methods enable the testing of larger RCA sample masses, overcoming the limitations of the TGA method. Furthermore, the IBR method reveals the significant impact of moisture conditions on the CO2 uptake of RCA, highlighting its utility in understanding RCA carbonation behavior.

The aim of this work was to investigate the evolutionary mechanisms of an artificial sedimentary agglomerate formed by cathodic polarization in natural seawater during its abandonment to a natural environment. Previous studies indicate that the mineralogical evolution of the material is controlled by kinetic factors and/or the local precipitation of aragonite on the brucite surface. However, the observation of the precipitation of metastable phase precipitation during the initial immersion of this material (in powder form) has suggested the possibility of a more complex mechanism. The present study builds upon previous experimental work and includes thermogravimetric analysis and infrared spectrometry. The results are analyzed using numerical experimentation to evaluate the proposed hypotheses. Findings show that the transformation mechanism is characterized by the precipitation of metastable calcium carbonate phases. Under supersaturation conditions, these hydrated phases form on the brucite surface, limiting the mineral’s contact with the solution. The subsequent transformation of these amorphous phases into aragonite further reduces brucite–solution interaction, which explains the persistence of brucite both in the residual powder after 120 h of immersion and in the consolidated material after more than 20 years of exposure to natural seawater.

The expanding global construction industry is driven by the need to develop sustainable alternatives to replace natural resources in concrete manufacturing. Reusing construction materials and increasing reuse effectiveness have emerged as popular study areas. Recently, the durability of recycled aggregate concrete (RAC) has drawn attention of numerous researchers worldwide. This review paper discusses the different approaches used to predict the durability of RAC (deterministic, probabilistic, and artificial intelligence). In addition, a critical review of the parameters more influential on the RAC durability performance is presented, including replacement ratio, particle size, chemical admixtures and additives, mixing technique, and curing conditions. Several contradictory results concerning the chloride ingress, carbonation, air and water permeability in the RAC are reported and discussed. The methods used to enhance the characteristics coarse recycled aggregate (CRA) are also categorised and summarised. We have found that complex, non-linear, and multivariable mechanisms control chloride ingress, carbonation, and permeability, rendering conventional modelling techniques inadequate. It is therefore advised to use artificial intelligence methods supported by comprehensive databases to provide precise durability predictions. The performance of RAC is greatly impacted by the adhered mortar (AM) in CRA; its increased porosity and water absorption result in weaker interfacial transition zones (ITZs), decreasing impermeability, and weakening resistance to carbonation and chloride ingress. Therefore, we have also reported that strengthening the microstructure or altering AM characteristics are the main treatment strategies used to increase RAC durability performance. By enhancing RAC performance and lowering the ecological footprint of construction and demolition waste, CRA carbonation stands out among these techniques as a potential technology that offers both technical and environmental benefits.

Recycled aggregate (RA) are typically stored in large stockpiles for several months after crushing. This study investigates whether such stockpiles can act as carbon sinks through natural concrete carbonation. To evaluate this, the CO2 uptake of a stockpile from an existing plant was modelled by taking into account the main driving-forces of carbonation, i.e., diffusion, permeation due to wind and CO2 binding by RA. Input parameters were determined from samples collected after crushing using new experimental devices. A 4-month carbonation was simulated under optimal conditions, i.e., in the absence of water-saturation of the stockpile by rain. The effects of various parameters were discussed through numerical simulations and analysis of characteristic times. The results show that gas diffusion alone is insufficient for deep carbonation, with significant carbonation limited to the top few centimeters of the stockpile. Although wind-driven advection could enhance deeper carbonation, it would require highly favorable conditions, such as continuous high speed wind. Over 4 months, the CO2 uptake only represents less 1 % of the stockpile binding capacity, which does not compensate for the emissions from the machines used on the platform. The change in the pile surface area due to samplings also does not increase the CO2 uptake. We conclude that it would be conservative not to take into account the CO2 uptake that occurs during RA storage in life cycle assessments.

Accelerated carbonation of recycled concrete aggregates (RCA) in industrial CO2-rich environments is a promising technique to enhance CO2 sequestration while improving RCA properties. This study investigates the influence of temperature (50–110 °C), initial water saturation degree (0.34–0.93), and RCA particle size (0–4 mm) on carbonation efficiency in a fixed-bed reactor under controlled conditions, simulating cement plant flue gases. Results highlight that water saturation degree is a key parameter, as it influences both CO2 transport in the pore system and the dissolution of reactive phases. Temperature significantly impacts water saturation degree evolution, which in turn affects reaction kinetics. For each initial water saturation degree, an optimal temperature maximizes carbonation, reaching degrees above 40 % after only 2 h carbonation. Particle size also influences carbonation efficiency: finer RCA exhibit higher carbonation rates. A novel Macro-TGA methodology was employed to quantify carbonate formation in 500 g samples, offering a more representative assessment compared to classical thermogravimetric analyses. Finally, water absorption tests before and after carbonation showed a slight reduction, with a maximum decrease of 2.7 % at 80 °C and 0.93 initial water saturation degree. However, no direct correlation between water absorption and carbonation degree was observed, suggesting complex porosity evolution that requires further investigation.

Recycled aggregates are primarily composed of concrete, natural stones, and bricks obtained through sorting, crushing, and sieving of construction and demolition waste. They offer a promising route toward reducing the consumption of natural resources and minimizing landfill use in civil engineering, thus supporting circular economy and contributing to more sustainable construction practices. This study specifically investigates the mechanical behavior of compacted fine recycled aggregates for road pavement base layers, with a focus on the effects of relative humidity and carbonation. Cylindrical samples with a compactness of 0.69 were subjected to controlled curing conditions over 30 and 100 days. Three relative humidity levels (53

The use of CO2-rich hot gases from cement plants or combustion processes is considered as an attractive method to accelerate the carbonation of recycled concrete aggregates (RCA). However, there is limited knowledge regarding the kinetics and mechanisms of accelerated carbonation induced by wet gas with a temperature of approximately 80°C. Water transport and temperature influence several parameters of the carbonation of cement-based materials, thus understanding and predicting their overall effect remains complex. The present study combines experimental and numerical investigations into the effects of temperature on carbonation processes. The experimental study focuses on understanding the effects of temperature on the evolution of the carbonation front, changes in chemical composition, and moisture transport within a cement-based material during carbonation in controlled conditions. The experimental data obtained serve as calibration parameters for a thermo-hydro-chemical coupled model of carbonation. The carbonation model incorporates heat transfer between the cement-based material and the external environment, considering the influence of temperature on water transfer, as well as the dissolution and carbonation of hydration products.

The urge to preserve natural resources, to reduce cement production CO 2 emissions and to recycle concrete waste conducted to the French national program FastCarb. It is aimed at using recycled concrete aggregates (RCAs), once carbonated with CO 2 coming from cement production sites, as a replacement for natural aggregates. The carbonation step serves to reduce the porosity of the old cement paste and to improve future concrete properties. Two different carbonation processes (rolling drum (P1), fluidized bed (P2)) were tested and the resulting RCAs were mixed in different weight proportions with natural aggregates to elaborate new concretes. Raman investigations were then conducted on some sections to analyze the carbonated phases and their spatial distribution. Results indicated a difference in polymorphs distributions. Process P1 seems to generate more vaterite than process P2, which mainly generates calcite and aragonite. They also allowed to appreciate the thickness of the interface between the old and the new cement pastes.

The construction sector is one of the largest consumers of natural resources, but also a producer of a considerable amount of waste. Construction and Demolition Waste can be transformed into recycled aggregates and used as a substitute for natural aggregates, either in road construction or concrete, which is one way to reduce the environmental impacts of the construction industry. In order to increase the use of recycled aggregates in high value-added materials like concrete, it is important to guarantee the quality of the produced aggregates. The recycling industry therefore needs new methods to automate the characterization of recycled aggregates. In a previous work we showed that deep convolutional networks can classify the different constituents of recycled aggregates, achieving an average accuracy of 97%. In this work, we propose a novel network architecture called RACNET designed to estimate the mass, the class and the binary mask of recycled aggregates from only 2D images. This could replace advantageously manual sorting tests as well as other geometric characterization tests (like particles size distribution), allowing for a real-time monitoring of recycled aggregates composition. We also present a prototype which preform automatic characterization of a flow of aggregates in real conditions, showing that our approach could be used in real industrial environments

Reinforced concrete is the most widely used building material but its durability in terms of concrete cover performance and corrosion of steel rebar is still a key point to be studied. To address this topic, within the frame of the national project PERFDUB, two series of eleven reinforced concrete specimens (with metric dimensions) were cast with innovative concrete mixes representative of the French experience, two shapes of rebar and two concrete covers. Then, these specimens were exposed in two natural exposure sites, one in Epernon for carbonation (XC4) and a second one in La Rochelle in the Atlantic Ocean in a tidal zone for chloride ions (XS3m). Their corrosion was carried out using non-destructive testing. In addition, in order to follow the corrosion evolution more accurately in a continuous way, two series of three specimens were casted with embedded sensors and were exposed in two other outdoor sites in Marne-la-Vallée (XC4) and in Eqiom facility (XS3e). The first results of this 20-year project in terms of corrosion of these reinforced concrete specimens obtained with laboratory and field equipment and with monitoring are presented in this paper.

The stability of sedimentary aggregate used for the stabilization of dykes in coastal area is investigated. This material is formed by cathodic polarization in seawater and is composed of marine sediments and calcareous deposit (brucite (Mg(OH)(2)) and aragonite (CaCO3)). Once the electrical current is switched off, this material could be subject to physical and mineralogical evolution, which may threaten the integrity of the protected structures. Few studies have been done on the pure calcareous deposit but not on this agglomerate, which is the major point of this study. For this purpose, 5 materials formed in laboratory were immersed during 18 months in natural seawater in the absence of electric current. Porosity and mineralogical composition (XRD and TGA/DTG) analyses were carried out at different times and an accelerated test was set up to evaluate a longer behavior of these aggregates. As the pure calcareous deposit, the ageing of these materials is characterized by a dissolution of brucite favoring the precipitation of aragonite. Contrary to thermodynamic expectations, this transformation takes place with a molar yield of less than 0.5 during the first 6 months of immersion. This implies a loss of material during this period, which is however slowed down in time by the local precipitation of aragonite and limits the dissolution reactions. Moreover, the mass ratio of these two phases (Mg(OH)(2)/CaCO3) is stable in the vicinity of 18 months of abandonment in natural seawater with a very low porosity variation (lower than 10%), which is an indication of this material stability.

The CO2 emissions due to the production of cement is a partly reversible phenomenon known as carbonation. The CO2 uptake occurs at each step of the life cycle of a structure, from the cradle to the grave as soon as concrete surfaces are in contact with atmospheric CO2. After concrete crushing, this carbon sink is amplified by the increase of material surface. However, the study of the carbonation of recycled aggregates is difficult to carry out in the laboratory or in situ. Physico-chemical modelling is therefore a powerful tool which should make it easier to explore the CO2 uptake. We propose here results from numerical simulations of carbonation at both the grain and the stockpile scales obtained during the French Project “Fastcarb”. Our purpose is to evaluate the efficiency of a process on recycled aggregates, and the influence of parameters assumed to control the CO2 uptake rate, such as ambient CO2 concentration, grain size and water content. Experimental data, gas diffusion tests and CO2 binding capacity and rate tests, give order of magnitude of time and length scales of interest through dimensionless numbers and are input to the full numerical model. The used model is formulated in terms of mass conservation equations for both water and CO2. Both dimensionless numbers and numerical results confirm that an accelerated process using industrial gases with high concentration (pCO2~20%) should be preferred to an atmospheric carbonation (pCO2~0.04%) to take full advantage of the CO2 uptake by recycled aggregates on short time scale.

Recycled aggregates compacted in road layers are made of a majority of concrete aggregates which can mineralize atmospheric CO2. Previous studies showed that carbonation modifies the microstructure of recycled concrete aggregates, but little information is available in the case of compacted recycled aggregates. Further-more, carbonation kinetics depends on CO2 diffusion through the compacted material, which is linked its microstructure. This paper presents an investigation of the evolution of both microstructure and CO2 diffusion coefficient of compacted recycled aggregates during carbonation in two different environments by X-ray to-mography. Segmented 3D images were analyzed to fully extract resolved pore structures. In addition, the CO2 diffusion coefficient variations were investigated by calculating the macroscopic diffusivity tensor in the segmented 3D images. We show that the numerical results are very similar to previous experimental results from gas diffusion tests and that the diffusivity coefficients can be estimated by using only the larger pore network (pore size > 5.5 mu m). These findings suggest that nondestructive imaging approaches, such as micro-Computed Tomography (mu CT), are a relevant alternative to experimental characterization methods.

Marine bacterial biomineralisation by CaCO3 precipitation provides natural limestone structures, like beachrocks and stromatolites. Calcareous deposits can also be abiotically formed in seawater at the surface of steel grids under cathodic polarisation. In this work, we showed that this mineral-rich alkaline environment harbours bacteria belonging to different genera able to induce CaCO3 precipitation. We previously isolated 14 biocalcifying marine bacteria from electrochemically formed calcareous deposits and their immediate environment. By microscopy and µ-Raman spectroscopy, these bacterial strains were shown to produce calcite-type CaCO3. Identification by 16S rDNA sequencing provided between 98.5 and 100% identity with genera Pseudoalteromonas, Pseudidiomarina, Epibacterium, Virgibacillus, Planococcus, and Bhargavaea. All 14 strains produced carbonic anhydrase, and six were urease positive. Both proteins are major enzymes involved in the biocalcification process. However, this does not preclude that one or more other metabolisms could also be involved in the process. In the presence of urea, Virgibacillus halodenitrificans CD6 exhibited the most efficient precipitation of CaCO3. However, the urease pathway has the disadvantage of producing ammonia, a toxic molecule. We showed herein that different marine bacteria could induce CaCO3 precipitation without urea. These bacteria could then be used for eco-friendly applications, e.g., the formation of bio-cements to strengthen dikes and delay coastal erosion.

Recycled concrete aggregates (RCA) incorporate hydrates that can be carbonated. The FastCarb project aims to mineralize CO2 within RCA, improving the quality of these aggregates by the clogging of the porosity and finally decreasing the CO2 impact of concrete in structures. It has two main objectives: to optimize in laboratory conditions the accelerated carbonation process which can be transposed at an industrial scale at a suitable cost and to show that the process could be used in industrial conditions. This paper presents firstly the results obtained in laboratory conditions: it confirms that it is possible to store between 10 and 50 kg of CO2/t of RCA depending on several factors (natural carbonation, water content, temperature, size of RCA…) and that the treatment allows an improvement of the properties like the water absorption. The feasibility of accelerated carbonation has been also demonstrated by setting up two industrial-scale demonstrators. The first results without optimization showed a CO2 capture rate in the order of 3–4 %, i.e. 30 kg of CO2 per ton of crushed concrete. 80 t of carbonated RCA were produced and used to produce C25/30 and C45/55 concretes. The measurement of the main properties (performance in the fresh state, mechanical performance, and durability) shows that the use of the carbonated RCA doesn’t affect these properties. A variety of precast products (blocks, curbs, stairs) and parts of cast-in-situ structures (construction of walls) were fabricated showing the feasibility of using these aggregates in real situations. Finally, our project considers whether the accelerated carbonation process is environmentally acceptable and economically viable. The first results show that the distance of transport (by trucks) is a major factor and that transportation should be limited to maintain a positive impact of the accelerated carbonation (i.e. local sources of CO2 should be used). The LCA and the economic study confirm that the sand fraction of RCA is the most interesting material for the uptake of CO2. This is also interesting for a circular economy objective because recycled concrete sand is not easily used in concrete made with RCA.