Carbonate Concretions Research Articles

Effect of low carbon marble dust powder, silica fume, and rice husk ash as tertiary cementitious material on the mechanical properties and embodied carbon of concrete

The recent decade has seen a surge in study towards cost-effective, ecologically benign, as well as socially advantageous cement replacements. Alternatives include industrial and agricultural waste, which can be recycled, repurposed, as well as renewed. However, using these wastes as supplementary cementitious materials (SCM) saves energy as well as reduces cement use, which helps reduce CO2 emission. Therefore, this research investigation is to use the silica fume (SF), rice husk ash (RHA), as well as marble dust powder (MDP) individually as SCM and combine as tertiary cementitious materials (TCM) for determining the fresh (workability), hardened (dry density, splitting tensile and compressive strength) and durability (carbonation depth, and water absorption) properties of concrete. In this regard, 345 concrete samples were made with 1:1.5:3 mix ratio and cured for 28 days. The outcome has been demonstrated that the workability, dry density, water absorption and carbonation depth of concrete is getting reduced with growing the SF, RHA and MDP as SCM and TCM in concrete. Besides, the compressive and split tensile strength are increased by 10.44% and 9.544% respectively at 9% of SF, RHA and MDP as TCM for 28 days. Besides, the embodied carbon of concrete is decreasing while amount of SF, RHA and MDP as SCM and TCM is increasing. It has been observed that the use of 9% TCM is offering good results for construction sector and reduce the consumption of cement in concrete which helps to decrease the carbon emission in the environment.

Hybrid fiber reinforced ultra-high performance coal gangue geopolymer concrete (UHPGC): Mechanical properties, enhancement mechanism, carbon emission and economic analysis

The low carbonization of ultra-high performance concrete (UHPC) has become a hot topic for sustainable development in the construction industry. Calcined coal gangue was used as aggregate and binder to prepare ultra-high performance coal gangue geopolymer concrete (UHPGC) in this paper. The hybrid reinforcement effect of steel fibers, calcium carbonate whiskers (CW), and carbon nanotubes (CNTs) on UHPGC was studied in the experiment. The results indicated that when the mixing ratio of straight steel fibers and hooked-end steel fibers was 2:1, the 28 d-compressive strength of UHPGC reached 145.94 MPa. However, excessive hooked-end steel fibers deteriorated the reinforcement effect of adjacent fibers and reduced the mechanical properties of UHPGC. CW and CNTs had a more significant improvement in the flexural properties of UHPGC. The bridging effect of CNTs and CW dispersed the stress on the matrix and delayed the formation and development of micro-nano cracks. Meanwhile, CNTs and CW improved the fiber bridging energy dissipation, thereby improving the flexural properties of UHPGC. The UHPGC had the highest flexural strength and flexural deflection of 13.59 MPa and 4.12 mm, respectively. The UHPGC prepared in this paper had lower carbon emissions and economic costs compared to traditional UHPC. Overall, this study provided valuable references for the resource utilization of coal gangue and the multi-scale strengthening and toughening of UHPGC.

Skin Anatomy, Bone Histology and Taphonomy of a Toarcian (Lower Jurassic) Ichthyosaur (Reptilia: Ichthyopterygia) from Luxembourg, with Implications for Paleobiology

A partial ichthyosaur skeleton from the Toarcian (Lower Jurassic) bituminous shales of the ‘Schistes Carton’ unit of southern Luxembourg is described and illustrated. In addition, associated remnant soft tissues are analyzed using a combination of imaging and molecular techniques. The fossil (MNHNL TV344) comprises scattered appendicular elements, together with a consecutive series of semi-articulated vertebrae surrounded by extensive soft-tissue remains. We conclude that TV344 represents a skeletally immature individual (possibly of the genus Stenopterygius) and that the soft parts primarily consist of fossilized skin, including the epidermis (with embedded melanophore pigment cells and melanosome organelles) and dermis. Ground sections of dorsal ribs display cortical microstructures reminiscent of lines of arrested growth (LAGs), providing an opportunity for a tentative age determination of the animal at the time of death (>3 years). It is further inferred that the exceptional preservation of TV344 was facilitated by seafloor dysoxia/anoxia with periodical intervals of oxygenation, which triggered phosphatization and the subsequent formation of a carbonate concretion.

Development of a learner model tool for predicting strength and embodied carbon for lightweight concrete production

The demand for sustainable concrete in meeting the net zero carbon target places a burden in optimizing concrete response to structural strength that satisfy acceptable embodied carbon. In most cases, a low carbon concrete is deficient in structural requirement and vice versa. This dilemma informs the need for a tool that can predict compressive strength as well as embodied carbon using the same input data. Since the use of alternative materials as cement replacement to enhance sustainability is emerging in the quest for a sustainable concrete, an optimal material that satisfy both conditions of structural integrity and sustainability is still lacking. Paucity of data in the emerging lightweight low carbon concrete using alternative materials, portends an upheave in the bias for prediction of the behaviour of lightweight low carbon concrete. This study therefore uses concrete data of lightweight low carbon concrete from laboratory experiment for the prediction of compressive strength and embodied carbon with their performance evaluated using eight machine leaning regression models. The results obtained indicates that the XG boost regression model exhibited excellent performance with a low Mean Squared Error (MSE) of 50.15, Mean absolute error(MAE) = 5.26, Mean absolute percentage error(MAPE) = 11.76 %, Explained variance score = 0.97, Root mean square error(RMSE) = 7.08 and a high R squared value of 0.96. The tool predicted compressive strength and embodied carbon for lightweight carbon concrete using multiple output regression such that the output can be limited to the yearly structural embodied carbon threshold to achieving 2050 net zero target. The developed tool when compared with concrete of similar mix ingredients performed more than 95 % in predicting concrete compressive strength and associated embodied carbon. In line with the inclusion of embodied carbon in carbon regulations of buildings in the UK as suggested by the professionals in the construction industry, the developed learner model and prediction tool has integrated concrete strength and embodied carbon to initiate a holistic approach to design and construction, balancing performance, cost, and environmental impact.

Research Progress in Corrosion Behavior and Anti-Corrosion Methods of Steel Rebar in Concrete

The corrosion of steel rebars is a prevalent factor leading to the diminished durability of reinforced concrete structures, posing a significant challenge to the safety of structural engineering. To tackle this issue, extensive research has been conducted, yielding a variety of theoretical insights and remedial measures. This review paper offers an exhaustive analysis of the passivation processes and corrosion mechanisms affecting steel rebars in reinforced concrete. It identifies key factors such as chloride ion penetration and concrete carbonization that primarily influence rebar corrosion. Furthermore, this paper discusses a suite of strategies designed to enhance the longevity of reinforced concrete structures. These include improving the concrete protective layer’s quality and bolstering the rebars’ corrosion resistance. As corrosion testing is essential for evaluating steel rebars’ resistance, this paper also details natural and accelerated corrosion testing methods applicable to rebars in concrete environments. Additionally, this paper deeply presents an exploration of the use of X-ray computed tomography (X-CT) technology for analyzing the corrosion byproducts and the interface characteristics of steel bars. Recognizing the close relationship between steel bar corrosion research and microstructural properties, this paper highlights the pivotal role of X-CT in advancing this field of study. In conclusion, this paper synthesizes the current state of knowledge and provides a prospective outlook on future research directions on the corrosion of steel rebars within reinforced concrete structures.

Carbonation of waste concrete: An effective and green strategy for enhancing its heavy metals removal from wastewater

Water pollution, especially Pb2+, Cd2+, Co2+, and Ni2+ released from industrial and mine wastewater, harms human health and is a global environmental concern. At the same time, the effective disposal of waste concrete originating from constructs is a global challenge. In this study, carbonated recycled concrete powder (CRP) is efficiently prepared by carbonizing waste concrete powder, which not only might enhance its adsorptive performance but also sequestrate CO2 in the form of mineral carbon. Characterization techniques revealed CRP forms calcium carbonate and highly polymerized silica gel. Batch adsorption experiments indicate that the CRP is found to have strong adsorption properties. The maximum equilibrium adsorption capacities calculated by the Langmuir model were determined as 997.03, 199.56, 148.85, and 76.69 mg/g for Pb2+, Cd2+, Co2+, and Ni2+, respectively, outperforming most waste concrete and industrial wastes reported. The adsorption mechanism mainly includes electrostatic interactions, precipitation, and ion exchange. This study proposes a method to synthesize low cost, good performance, high chemical stability, and facile preparation adsorbent using waste concrete powder, with promising applications in wastewater treatment.

Biotic and abiotic processes in Ediacaran spheroid formation

Organic-rich shales from the uppermost Doushantuo Fm. (South China) record one of the most negative carbonate carbon isotopic excursions in Earth’s history, known as the Shuram excursion, and contain meter to micro-size spheroids. In this study, we use Raman and energy dispersive spectroscopy to identify and describe the most common diagenetic spheroids to refine our understanding of the profound perturbations of the carbon cycle and the evolution of pore fluid chemistry imprinted in the sedimentary Precambrian record, especially in the late Ediacaran. The presence of 13C-depleted carbonate concretions or organic matter (OM) enclosed by lenticular dolomitic structures within the host shale unit suggests OM remineralisation and anaerobic oxidation, resulting in authigenic carbonate precipitation during the earliest stages of sediment diagenesis. Other mineralogical features, however, point to high levels of primary production, such as apatite bands that host spheroidal microfossils with highly fluorescent quartz and OM within abiotic concretions. These observations highlight the importance of considering co-occurring biotic and abiotic processes in explaining the formation of diagenetic spheroids in ancient sedimentary environments. From an astrobiology perspective, the interplay of biotic and abiotic processes reflects the complexity of early life systems and the environments that may exist on other terrestrial planets. Understanding the signatures of biotic and abiotic interactions in the Doushantuo Fm. is crucial for identifying potential biosignatures in extraterrestrial materials, thereby enhancing our understanding of life’s universality and adaptability in diverse and extreme environments.

Identification of the Effect of Concrete Carbonation on the Strength of Cooling Tower Structures Using the Monte Carlo Simulation Method

Identification of the Effect of Concrete Carbonation on the Strength of Cooling Tower Structures Using the Monte Carlo Simulation Method

Fish otoliths from the bathyal Eocene Lillebælt Clay Formation of Denmark.

Few deepwater otolith associations from the Eocene have been found so far. The small assemblage of aragonitic-preserved otoliths from the Lillebælt Clay Formation described here therefore adds to the understanding of early Palaeogene deep-sea fish faunas. These otoliths were obtained from a level at about the Ypresian/Lutetian interface and may thus be older than the otoliths previously described from Trelde Næs from mold casts from carbonate concretions. Only 14 otoliths were recovered from about 6,000 kg processed bulk samples. The assemblage also differs in the composition and contains three new species and one new genus: Diaphus? duplex n. sp., Bregmaceros danicus n. sp. and the ophidiid Pronobythites schnetleri n. gen, n. sp. In addition, the new genus Treldeichthys n. gen. in Acanthomorpha incertae sedis is established for T. madseni (Schwarzhans, 2007). The small assemblage also differs in composition from comparable associations described from southwest France and northern Italy on the species level but shows some relationship on a higher systematic level. The mechanism and timing of the colonization of the deep sea by selected groups of fishes is discussed, particularly in respect to the depth migration of demersal fishes.

MODERN APPROACHES TO THE USE OF COMPOSITE MATERIALS IN CONSTRUCTION

A review of the literature on scientific approaches in the development of composite materials and building structures made of composites is carried out. When creating and manufacturing traditional and new composite materials, for example, by additive manufacturing, and when creating structures and structures in engineering calculations, new techniques, finite element computational software systems, and neural network technologies are used, which are used in the creation of modern metal and composite materials, analysis of mechanical characteristics of materials, forecasting loads on the structure, optimization of structures and calculation of their construction characteristics. The distinctive features of modern composite materials are shown. The main types of composite materials are considered: talc, diatomite, calcium carbonate, gibbsite, barium sulfate, feldspar, nepheline, aragonite, calcium carbonate, wool, silk, cotton, linen, jute, wood pulp, asbestos, fiberglass, metal fibers, quartz fibers, basalt fibers, polyamide fibers, polyester fibers, polyvinyl alcohol fibers, carbon fibers, viscose fibers. The physical and mechanical characteristics of composite materials (based on epoxy, aluminum, carbon, magnesium, and nickel matrices) and traditional (steel, aluminum, brick, concrete) building materials are presented. The disadvantages of such composite materials as carbon fiber, fiberglass, organoplastics, textolite, carbon concrete, and polystyrene concrete are presented. Deformation diagrams of some types of fibers for composite materials are considered: high-modulus carbon fibers, high-strength carbon fibers, aramid fibers, glass fibers, and basalt fibers. The advantages of the system of external reinforcement of building structures with composite materials are described. Examples of reinforcement of building structures are considered: reinforced concrete reinforcement; reinforcement of floor slabs; reinforcement of columns; and reinforcement of brick walls.

SEDIMENTOLOGIA, ESTRATIGRAFIA E MINERALOGIA DA FORMAÇÃO SOLIMÕES NO IGARAPÉ DIABINHO AFLUENTE DO RIO ENVIRA FEIJÓ-ACRE

The Igarapé Diabinho, is a tributary on the right bank of the Envira river, which is part of the Juruá river basin in the central region of the State of Acre (municipality of Feijó). It is in a U-type valley, carving out the sediments known as the Solimões Formation, considered as of Late Miocene to Pliocene age. In this stream, as well as in many regions of Acre, these sediments are partly covered by alluvial (fluvial-lacustrine) sediments from the Quaternary. The rocky exposures along the Diabinho stream show a succession of massive silt-clay sediments, green to cream in color, with vertical columnar concretions, scattered irregular calcite concretions, and gypsum venulations. These sediments are in turn covered by other compact sandy silts cemented by friable carbonates or even partially covered by a layer of horizontal discoid concretions of calcitic limestone. It is common in this area to locally occur accumulations of remains of fossil bones of vertebrates and plant trunks, constituting a basal conglomerate. For this study, three vertical stratigraphic profiles were described approximately 15 meters apart and rock samples were collected in addition to fossil bones along the profiles, which were subjected to granulometric analysis and mineralogical identification with the aid of X-rays diffraction (XRD), transmitted light optical microscopy and scanning electron microscopy (SEM/SED) with semiquantitative analysis. The sediments have a silty-sandy grain size with little clay, manganese, and carbonate concretions. The main minerals identified in these sediments by XRD and optical microscopy in thin sections were quartz, smectite, kaolinite, illite, albite, microcline, muscovite, chlorite, and hematite. In fragments of fossil vertebrate bones, scanning electron microscopy and semiquantitative analyses allowed the identification of the presence of apatite as the main constituent in addition to the presence of calcite, rhodochrosite, siderite, goethite, hematite, and gypsum.

Water recycling in teaching laboratories for civil construction courses

Civil construction courses have laboratories for the development of educational activities. The activities involve the production of construction elements that require the consumption of treated water to prepare materials and wash equipment, generating liquid effluents at the end of each class. The reuse of liquid effluents generated in the civil construction educational laboratory was studied with the aim of reducing the demand for treated water and reducing the liquid waste discharged into the public sewage system. The effluent generated was collected, quantified and treated by primary decantation, generating reused water. Concrete was produced with reused water as a replacement for treated water, with contents of 20, 50, 80 and 100% and compared to the control concrete, 100% treated water. Parameters of axial compression strength and durability by natural carbonation were evaluated. Concretes with up to 50% reused water presented the same carbonation as the control concrete, and concretes produced with 80 and 100% reused water presented carbonation (2.5 mm), a result slightly higher than the carbonation of concretes produced with up to 50% reused water (1.5 mm). Considering the test results, it can be concluded that it is possible to reuse up to 50% of the reused water in the production of concrete without compromising mechanical resistance and durability. For educational purposes, it is possible to use 100% of the reused water produced, that is, pure, contributing to sustainability and with the guarantee that such use does not cause any harm to the health of teachers, technicians or students. It should also be considered that such use becomes efficient and can be an alternative to treating the waste and its subsequent release into the public network or directly into nature.

Influence of Corrosion on Lifespan of Reinforced Concrete Structures: A Comprehensive Review

Carbonation-induced corrosion is a major concern for reinforced cement concrete (RCC) structures, impacting their long-term durability and structural integrity. This review synthesizes the findings on the deterioration mechanisms in concrete structures, focusing on carbonation, chloride-induced corrosion, and time-dependent deterioration. The analysis includes discussions on predictive likelihood methods for estimating bridge reliability, the impact of environmental factors on carbonation, and standardized testing methods for assessing concrete durability. The review highlights the importance of understanding material characteristics and environmental conditions in designing durable concrete structures, emphasizing the processes of carbonation, its impact on rebar corrosion, and strategies for mitigation. Sheltered concrete carbonation resistance in metropolitan tropical climates is 10-20% lower than open exposure. SCM concretes exhibit equivalent or greater long-term carbonation resistance to OPC concretes, as evidenced by the increase in carbonation depth ( Δ xd) at ages greater than 5 years. The paper concludes with recommendations for integrating advanced modeling techniques and empirical studies to develop robust maintenance strategies and improve concrete mix designs for enhanced durability.

Effect of sea salt on carbonation and CO2 uptake in cement mortar

Previous studies mainly focused on the effects of concrete carbonation on chloride ion penetration due to the resulting reinforcement corrosion. However, it is still being determined what influence sea salt, which is common in coastal areas, has on the carbonation of cement based building materials. Thus, cement mortar samples were immersed in simulated seawater and then submitted to an accelerated carbonation test at a CO2 concentration of 5 % and a relative humidity of 58 %. For the samples that underwent different carbonation cycles, weight changes and carbonation depth were measured, and the associated mechanisms were demonstrated by combined thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The results showed that salt crystals do not significantly change the pore size distribution and composition of cement mortar, but effectively influence the carbonation rate. The carbonation rate of the cement mortar sample containing sea salt was 36 mm/year0.5, 36.8 % lower than that of the control sample. Carbonate crystals efficiently occupy the pore volume in the size range of 0.02–0.15 μm and significantly reduce the carbonation rate. The results can provide a research basis for estimating the carbonation rate and measuring the CO2 uptake of cement-based building materials in coastal regions.

A Study on the Thermodynamic Response of Double-Armed Thin-Walled Piers under an FRP Anti-Collision Floating Pontoon Fire

Abstract: As a potential fire scenario for bridge structures, the safety impact of an FRP anti-collision floating pontoon fire on bridge structures cannot be ignored. Taking the FRP anti-collision floating pontoon fire that occurred in a continuous rigid-frame bridge as the engineering background, the damage condition of the actual bridge fire scene was first investigated. In addition, FDS 5.3 software was used to simulate the FRP anti-collision floating pontoon fire scenario. Furthermore, the thermal–structural coupling method was used to investigate the thermodynamic response of double-armed thin-walled piers under fire. The results show that the FRP anti-collision floating pontoon fire causes localized concrete carbonization and spalling on the surface of the P2 pier, and the FRP anti-collision floating pontoons are largely destroyed. The fire has the greatest impact on the P2-1 pier, with the highest temperature of 667 °C on the windward side and the highest temperature of 326 °C on the leeward side. The temperature impact range is 6 m above the bearing platform, and the maximum damage depth of pier body concrete is 84.58 mm. The deformation and stress of the P2 pier under fire do not show significant changes and do not exceed the allowable limits for structural deformation and material stress. Therefore, the impact of this fire accident on the structural safety of the continuous rigid-frame bridge is minor. This study's results provide reliable guidance for the fire safety assessment and post-fire structural repair of the continuous rigid-frame bridge.

Storing CO2 while strengthening concrete by carbonating its cement in suspension

Cement is a key constituent of concrete and offers a large sequestration potential of carbon dioxide (CO2). However, current concrete carbonation approaches are hindered by low CO2 capture efficiency and high energy consumption, often resulting in weakened concrete. Here, we conceptually develop and experimentally explore a carbonation approach that resorts to injecting CO2 into a cement suspension subsequently used to manufacture concrete, turning the carbonation reaction into an aqueous ionic reaction with a very fast kinetics compared to traditional diffusion-controlled approaches. This approach achieves a CO2 sequestration efficiency of up to 45% and maintains an uncompromised concrete strength. The study shows that the CO2 injection rate influences the polymorph selectivity of mineralized calcium carbonate (CaCO3) depending on the local environmental conditions and impacts the strength of concrete. The technological simplicity of the proposed approach enables a reduced carbon footprint and promising prospects for industrial implementation.

Carbonated Durability of Premixed Concrete with Carbon Dioxide as an Admixture

The cement manufacturing industry emits a large amount of CO2 during the production process, exacerbating environmental problems such as greenhouse effect. To solve this problem, researchers in the engineering field have developed a large number of new technologies and products to reduce carbon emissions when using Portland cement concrete. Among them, injecting CO2 into fresh concrete is a direct approach to the topic. However, further research is needed on its carbon sequestration efficiency and whether it will have adverse effects on the durability of concrete structures. This article summarizes the current research status of pre mixed concrete using CO2 as an admixture, analyzes its carbon sequestration efficiency, and based on a concrete carbonation durability life prediction model, analyzes the impact of CO2 injection on carbonation durability life during concrete mixing.

Mechanical properties and hydration mechanism of low carbon concrete with recycled aggregate

Collaborative and effective disposal of construction and industrial solid waste is of great significance for protecting the ecological environment. In this paper, low carbon concrete with recycle aggregate (LCCRA) mainly made of phosphogypsum, fly ash, slag and recycled aggregate was studied. The uniaxial compression test was carried out to determine the stress-strain relationship of LCCRA and a constitutive model for LCCRA under uniaxial compressive loading was established. Scanning Electron Microscopy (SEM) was used to explore the hydration process of LCCRA. The results demonstrated that the uniaxial compressive strength of LCCRA achieved 30.8 MPa with a 100 % replacement rate of recycled coarse aggregate and a water-binder ratio of 0.54. The constitutive model of LCCRA under uniaxial compression fits well with the experimentally measured stress-strain curve. SO42− in low carbon cementitious materials reacts with [SiO4]4-, [AlO4]5- to generate C–S–H gel, C-A-S-H gel and AFt crystals, which enhance the density of LCCRA interfacial transition zone (ITZ) and thus improve its basic mechanical properties.

Study of the impact of sediments on the mechanical behavior of concrete and towards the penetration of carbon dioxide

Dam reservoirs are exposed to a loss of water storage capacity due to the phenomenon of siltation. This particularity can be expressed by the siltation of reservoirs and the entrainment of particles transported by watercourses. Siltation of reservoirs is a critical state which causes a reduction in the storage capacity of dams. Algeria is characterized by a semi-arid climate, which annually loses a considerable volume of water storage. The carbonation of concrete is influenced by a number of parameters which accelerate its kinetics. These parameters are the porosity of the concrete, the quantity of lime contained in the cement, the concentration of CO2 in the atmosphere and the humidity of the environment. It should be noted that, water being the vector for moving aggressive agents, carbon dioxide can only diffuse through the concrete if the latter is not completely saturated and not perfectly dry at the same time. Another factor increasing the permeability of concrete is the amount of limestone added to the cement during its manufacture at the factory. This permeability allows the diffusion of CO2 or other aggressive agents in the concrete. The addition of limestone to cement must therefore be used with caution. The objective is to propose economically competitive and easy-to-implement formulations which allow the valorization of these materials in the making of ordinary concrete by partial substitution of cement (10, 20 and 30%) and its influence on the progress of long-term carbonation after six years of curing in the open air. The sediment is treated by calcination at 750°C to make it active. Natural carbonation tests were carried out on the study concretes in order to evaluate their durability. The results obtained confirmed the possibility of producing concretes incorporating calcined sludge at dosages of up to 30% without compromising the quality of these concretes from the point of view of behavior in the face of attacks by the dissolution of carbon dioxide from the air in the interstitial solution of concrete, meeting economic, ecological and technological objectives.

Statement of Retraction: Characteristics and significance of microfossils in carbonate concretions of the Upper Triassic succession, Ordos Basin, China

Statement of Retraction: Characteristics and significance of microfossils in carbonate concretions of the Upper Triassic succession, Ordos Basin, China