Sustainable concrete production using toxic foundry sand and its subsequent effect on water contamination

Amid growing concerns about diminishing river sand resources and escalating environmental apprehensions related to toxic landfill waste, this study explores the potential of Toxic Foundry Sand (TFS) as a substitute for Standard Fine Aggregate (SFA) in concrete production. The investigation into various TFS replacement ratios in M20 concrete focuses on their impact on workability and compressive strength. Although TFS exhibits properties similar to fine aggregate, making it a promising candidate for partial replacement, differences in bulk density and fineness modulus compared to river sand suggest that TFS should be utilized as a partial replacement only. The study proposes an optimal replacement ratio of 30 % TFS and 70 % SFA to achieve satisfactory compressive strength in M20 concrete. The workability of fresh concrete remains unaffected in both nominal and 70:30 mixes, ensuring ease of mixing on the job site. As an innovative aspect, the study includes testing the water exposed to TFS-infused concrete for portability. Prolonged exposure to water on TFS-infused concrete (70:30 mix) raises concerns, as certain parameters such as chloride and hardness exceed acceptable limits. Therefore, careful control and treatment of Toxic Foundry Sand Contact Water (TFSCW) are deemed crucial on job sites to address potential water quality issues and ensure overall environmental safety.

CO2 utilization for concrete production: Commercial deployment and pathways to net-zero emissions

Approximately 10 % of global anthropogenic CO2 emissions arise from the cement and concrete industry driven by urban expansion and a constant need for infrastructure renewal. Reusing waste CO2 to make new construction materials produces circular carbon flows and constitutes a key step toward a carbon-negative economy. To establish a holistic view of the field, this paper examines upscaled technologies with industrial deployments for utilizing CO2 in manufacturing cement-based materials and analyzes their interplay for attaining net-zero emissions (NZE) in the concrete sector. By scrutinizing the status quo, it suggests that NZE agendas should be diversified catering to the wide-ranging built products. Small-sized precast elements and lightweight components lead the way in carbon-neutral manufacturing, while the market-dominating ready-mix concrete is by far difficult to decarbonize and relies on the incorporation of pre‑carbonated ingredients, preferably sourced from alkaline wastes, to leverage large-scale CO2 utilization. To expedite the race to NZE, it is necessary to combine the development of CO2 utilization and low-CO2 cement to create decarbonization strategies tailoring for individual products. In this regard, the paper reveals credible pathways and research needs to facilitate their implementation in sustainable construction.

Bio-corrosion in concrete sewer systems: Mechanisms and mitigation strategies

The deterioration of concrete sewer structures due to bio-corrosion presents critical and escalating challenges from structural, economic and environmental perspectives. Despite decades of research, this issue remains inadequately addressed, resulting in billions of dollars in maintenance costs and a shortened service life for sewer infrastructure worldwide. This challenge is exacerbated by the absence of standardized test methods and universally accepted mitigation strategies, leaving industries and stakeholders confronting an increasingly pressing problem. This paper aims to bridge this knowledge gap by providing a comprehensive review of the complex mechanisms of bio-corrosion, focusing on the formation and accumulation of hydrogen sulfide, its conversion into sulfuric acid and the subsequent deterioration of concrete materials. The paper also explores various factors affecting bio-corrosion rates, including environmental conditions, concrete properties and wastewater characteristics. The paper further highlights existing corrosion test strategies, such as chemical tests, in-situ tests and microbial simulations tests along with their general analytical parameters. The conversion of hydrogen sulfide into sulfuric acid is a primary cause of concrete decay and its progression is influenced by environmental conditions, inherent concrete characteristics, and the composition of wastewater. Through illustrative case studies, the paper assesses the practical implications and efficacy of prevailing mitigation techniques. Coating materials provide a protective barrier against corrosive agents among the discussed techniques, while optimised concrete mix designs enhance the inherent resistance and durability of the concrete matrix. Finally, this review also outlines the future prospects and challenges in bio-corrosion research with an aim to promote the creation of more resilient and cost-efficient materials for sewer systems.

Effect of banana tree leaves ash as cementitious material on the durability of concrete against sulphate and acid attacks

The construction industry's rapid growth poses challenges tied to raw material depletion and increased greenhouse gas emissions. To address this, alternative materials like agricultural residues are gaining prominence due to their potential to reduce carbon emissions and waste generation. In this context this research optimizes the use of banana leaves ash as a partial cement substitution, focusing on durability, and identifying the ideal cement-to-ash ratio for sustainable concrete. For this purpose, concrete mixes were prepared with BLA replacing cement partially in different proportions i.e. (0 %, 5 %, 10 %, 15 %, & 20 %) and were analyzed for their physical, mechanical and Durability (Acid and Sulphate resistance) properties. Compressive strength, acid resistance and sulphate resistance testing continued for 90 days with the intervals of 7, 28 and 90 days. The results revealed that up to 10 % incorporation of BLA improved compressive strength by 10 %, while higher BLA proportions (up to 20 %) displayed superior performance in durability tests as compared to the conventional mix. The results reveal the potentials of banana leave ash to refine the concrete matrix by formation of addition C-S-H gel which leads towards a better performance specially in terms of durability aspect. Hence, banana leaf ash (BLA) is an efficient concrete ingredient, particularly up to 10 % of the mix. Beyond this threshold, it's still suitable for applications where extreme strength isn't the primary concern, because there may be a slight reduction in compressive strength.

Chloride-induced corrosion of steel in concrete-insights from bimodal neutron and X-ray microtomography combined with ex-situ microscopy

The steel-concrete interface (SCI) is known to play a major role in corrosion of steel in concrete, but a fundamental understanding is still lacking. One reason is that concrete's opacity complicates the study of internal processes. Here, we report on the application of bimodal X-ray and neutron microtomography as in-situ imaging techniques to elucidate the mechanism of steel corrosion in concrete. The study demonstrates that the segmentation of the specimen components of relevance-steel, cementitious matrix, aggregates, voids, corrosion products-obtained through bimodal X-ray and neutron imaging is more reliable than that based on the results of each of the two techniques separately. Further, we suggest the combination of tomographic in-situ imaging with ex-situ SEM analysis of targeted sections, selected based on the segmented tomograms. These in-situ and ex-situ characterization techniques were applied to study localized corrosion in a very early stage under laboratory chloride-exposure conditions, using reinforced concrete cores retrieved from a concrete bridge. Several interesting observations were made. First, the acquired images revealed the formation of several corrosion sites close to each other. Second, the morphology of the corrosion pits was relatively shallow. Finally, only about half of the total 31 corrosion initiation spots were in close proximity to interfacial macroscopic air voids, and > 90% of the more than 160 interfacial macroscopic air voids were free from corrosion. The findings have implications for the mechanistic understanding of corrosion of steel in concrete and suggest that multimodal in-situ imaging is a valuable technique for further related studies.

Supplementary Information

The online version contains supplementary material available at 10.1617/s11527-024-02337-7.

Liquid concrete as a gastrointestinal tract foreign body

Gastrointestinal foreign bodies present a common clinical challenge. We present an unusual case of a 58-year-old construction worker who ingested liquid concrete that risked solidifying in his stomach. Gastroscopy revealed only partial solidification and pyloric obstruction, which were successfully resolved through endoscopic fragmentation and mechanical removal. To protect the gastric mucosa during elimination, liquid paraffin and a cellulose-based formula were administered. Complete gastrointestinal evacuation was achieved within 3 days, with no complications observed. This case emphasises the urgency of the early removal of concrete.

Sustainable approaches in concrete production: An in-depth review of waste foundry sand utilization and environmental considerations

This review critically evaluates the potential of Waste Foundry Sand (WFS) as a substitute for fine aggregate in concrete, conducting a comparative analysis of its physical and chemical properties against those of natural sand. The study synthesizes findings from various research experiments to determine concrete's most effective WFS replacement percentage. It compiles and analyzes data on how different WFS ratios affect concrete's mechanical properties, including modulus of elasticity and compressive strength. The review also consolidates research on the impact of WFS on concrete's workability, density, and flowability. A key finding is that WFS, categorized as a non-hazardous waste, possesses a diverse particle size distribution, rendering it suitable for recycling in various industrial applications.The study identifies that a 20%-30% replacement of WFS in concrete significantly improves properties such as voids, specific gravity, and density. However, it is essential to note that exceeding a 30% WFS replacement can result in increased carbonation depth and decreased resistance, primarily due to sulfur trioxide (SO3). Further observations indicate that incorporating higher levels of WFS in self-compacting concrete reduces its flowability and increases water permeability. Moreover, the review highlights the regulatory and classification challenges associated with using WFS, particularly its classification as waste, which hampers its widespread adoption in construction. In conclusion, the study recommends implementing End-of-Waste (EoW) regulations to facilitate sustainable recycling and environmental protection. Additionally, it includes a bibliometric analysis of foundry sand research spanning from 1971 to 2020, providing a comprehensive summary of the field's historical and recent developments.

An investigation of neutron shielding and activation performances of four types of concrete for carbon ion therapy facility

Carbon ions have unique physical and biological properties that allow for precise targeting of tumors while minimizing damage to surrounding healthy tissues. The emitted neutrons dominate the radiation field in the treatment room and pose challenges for radiological shielding. Concrete is extensively utilized in the construction of radiotherapy facilities due to its good shielding characteristics, and it can be easily poured into the desired shapes and thickness. The difference in composition of concrete affects the characteristics of neutron attenuation and activation performance. Therefore, the purpose of this study is to clarify the shielding properties and activation performances of four types of concrete for carbon ion therapy facilities. The Monte Carlo method is used to analyze the neutron spectra from thick targets upon carbon ion bombardment. Furthermore, the deep attenuation efficiency of the secondary neutron in different compositions of concrete is discussed. The shielding design is developed to ensure compliance with the prescribed dose limit outside the shielding during operation. Finally, the induced radioactivity in concrete is estimated for both short-term and long-term operation. The produced radionuclides inventories and depth profiling are determined. This study reveals the shielding and radioactivity issue of carbon ion therapy facilities and is expected to aid in the design or construction of similar facilities.

Prediction of compressive strength of concrete based on improved artificial bee colony-multilayer perceptron algorithm

There are many factors that affect the compressive strength of concrete. The relationship between compressive strength and these factors is a complex nonlinear problem. Empirical formulas commonly used to predict the compressive strength of concrete are based on summarizing experimental data of several different mix proportions and curing periods, and their generality is poor. This article proposes an improved artificial bee colony algorithm (IABC) and a multilayer perceptron (MLP) coupled model for predicting the compressive strength of concrete. To address the shortcomings of the basic artificial bee colony algorithm, such as easily falling into local optima and slow convergence speed, this article introduces a Gaussian mutation operator into the basic artificial bee colony algorithm to optimize the initial honey source position and designs an MLP neural network model based on the improved artificial bee colony algorithm (IABC-MLP). Compared with traditional strength prediction models, the ABC-MLP model can better capture the nonlinear relationship of the compressive strength of concrete and achieve higher prediction accuracy when considering the compound effect of multiple factors. The IABC-MLP model built in this study is compared with the ABC-MLP and particle swarm optimization (PSO) coupling algorithms. The research shows that IABC can significantly improve the training and prediction accuracy of MLP. Compared with the ABC-MLP and PSO-MLP coupling models, the training accuracy of the IABC-MLP model is increased by 1.6% and 4.5%, respectively. This model is also compared with common individual learning algorithms such as MLP, decision tree (DT), support vector machine regression (SVR), and random forest algorithms (RF). Based on the comparison of prediction results, the proposed method shows excellent performance in all indicators and demonstrates the superiority of heuristic algorithms in predicting the compressive strength of concrete.

A life cycle assessment of cardboard waste in low stress grade concrete applications

Utilising cardboard waste for the partial substitution of cement within concrete has the potential to yield significant sustainability benefits. Cardboard waste is abundantly available, and a significant proportion of this material is disposed of in landfill. However, conversion of waste cardboard into kraft fibres (KFs) for concrete implementation can be utilised in the building and construction industry. Therefore, identification of sustainability variables associated with cardboard waste in concrete is vital. In this study, two KF composites satisfied the criteria for low stress grade concrete and were subsequently evaluated. SFKF5 mix design contained 5% KFs and SFKF105 contained 10% KFs with 5% metakaolin (MK). Both composites had silica fume (SF) as a fibre modification technique for durability purposes. A life cycle assessment (LCA) determined the environmental effect of waste cardboard integration. A Monte-Carlo simulation was utilised as the sensitivity analysis to investigate transportation and energy manufacturing greenhouse gas (GHG) emission variables. LCA results of SFKF105 had a savings of 11%, 8%, 4% and 1% for terrestrial acidification potential, global warming potential (GWP), terrestrial ecotoxicity potential (TEP) and human toxicity potential, respectively. SFKF5 revealed savings of 3%, 2% and 4% for GWP, TEP and marine eutrophication potential, respectively. The additional travel requirements of KFs and MK to the cement batching plant for composite production did not surpass the embodied energy and travel emissions of the control. However, this was negated due to the additional energy requirements to manufacture KFs. The control, SFKF5, and SFKF105 had an average total of 572, 1023 and 997 kgCO2-eq/m3, respectively.

Use of buffer treatment to utilize local non-alkali tolerant bacteria in microbial induced calcium carbonate sedimentation in concrete crack repair

Concrete often suffers cracks due to its low tensile strength. The repair process can vary ranging from surface coating, grouting, and strengthening. Microbial induced calcium carbonate sedimentation process (MICP) is a process of utilizing non-pathogenic bacteria to produce calcium carbonate through its urease activity in crack repair (filling). It is known as an alternative crack repair method that does not utilize Portland cement. In general, the bacteria used in MICP are alkali tolerant bacteria that have a higher chance of surviving the high alkalinity environment in concrete. However, in some regions, alkali tolerant bacteria are difficult to acquire and unavailable locally. This study introduced a technique to utilize non-alkali tolerant bacteria in MICP using buffer treatment. Instead of injecting bacteria directly onto the crack surface, the buffer solution was applied onto the crack surface prior to the bacteria injection. Results from the laboratory indicated a higher bacteria survival rate when the buffer treatment was applied to the medium. For the crack filling, with the buffer treatment, the crack was completely filled within 21-28 days. The microstructure results also showed that the crystal deposits from both laboratory and crack surface were similar in both physical appearance and phase composition.

Recycling facemasks into civil construction material to manage waste generated during COVID-19

Growing plastic pollution in the context of COVID-19 has caused significant challenges, exacerbating this already out-of-control issue. The pandemic has considerably boosted the demand for personal protective equipment (PPE), such as facemasks and gloves, all over the globe, and mismanaging this growing plastic pollution has harmed the environment and wildlife significantly. To mitigate negative environmental impacts, it is necessary to develop and implement effective waste management strategies. This present study estimated the daily facemask generation throughout the pandemic in Iran based on the distribution of urban and rural populations and, likewise, the daily generation of hand gloves in the COVID-19 era and the amount of medical waste generated by COVID-19 patients were calculated. In the next step, the quantities of discarded facemasks dumped into the Caspian Sea, the Persian Gulf, and the Gulf of Oman from the coastal cities were determined. Finally, the innovative alternatives for repurposing discarded facemasks in civil construction materials such as concrete, pavement, and partition wall panel were discussed.

Prediction and optimization of hardened properties of concrete prepared with granite dust and scrapped copper wire using response surface methodology

Urban growth in the developing world has prompted researchers to seek alternatives to fine aggregate due to the severe environmental impact of extensive natural sand depletion. On top of that, the accumulation of non-biodegradable dumps, solid trash such as scrapped copper wire (SCW), and industrial remnants like granite dust (GD) have reached alarming levels. Therefore, incorporating these two waste materials in concrete offers a potentially sustainable solution. The study aims at substituting natural fine aggregate with GD as well as incorporating SCW for predicting and optimizing the compressive and splitting tensile strength of concrete using response surface methodology (RSM). Two independent variables, the volumetric percentages of GD (10 %, 20 %, and 30 %) and SCW (0.1 %, 0.3 %, and 0.5 %) in a concrete mix ratio of 1:1.5:3, were utilized to create probabilistic models for compressive and splitting tensile strength at 7 and 28 days. The experimental design employed central composite design (CCD) of RSM and the results of both ANOVA and regression analysis in terms of several statistical functions demonstrated a strong correlation between the predicted values of the responses and the actual experimental results. The developed models were validated by conducting experiments using optimized proportions of GD (23.32 %) and SCW (0.37 %). Finally, the strengths of the optimum content mix yielding 25.12 MPa and 3.266 MPa, respectively for compressive and splitting tensile at 28 days ensure the efficiency of the models due to the substantial similarity between experimental and predicted values. Therefore, integrating GD and SCW for higher-strength concrete in mass production can be a cost-effective alternative, fostering increased recycling of waste and supporting sustainable growth in building construction.

Distribution and release of PFAS from AFFF-impacted asphalt: How does it compare to concrete?

Aqueous film forming foam (AFFF)-impacted asphalt and concrete may serve as potential secondary sources of per- and polyfluoroalkyl substances (PFAS) to the environment through surficial leaching. We aimed to understand the vertical distribution and surficial release of PFAS from AFFF-impacted asphalt and concrete cores collected from various locations (∼10-70 m distance between samples). Among the PFAS analyzed, 6:2 FTS was observed as having the highest concentration in the surface layer (0 - 0.5 cm) of concrete (225 µg kg-1) and in the runoff from the concrete (2600 ng L-1). PFOS was detected at the highest concentration in the surface layer (0 - 0.5 cm) of asphalt (47 µg kg-1) and associated runoff (780 ng L-1). The total mass of PFAS released during three rainfall simulations accounts for a fraction of the total mass in the surface layer (0 - 0.5 cm), ranging from 0.10 - 9.8% and 0.078 - 2.4% for asphalt and concrete cores, respectively. Asphalt exhibited a higher release rate than concrete, demonstrated by the higher total release coefficient of PFAS (4 - 16 m-2) compared to that of concrete cores (1 - 5 m-2). These results suggested that, similar to concrete, AFFF-impacted asphalt may be a secondary source of PFAS to the environment.

Evaluation of radiological health risk caused by the use of fly ash in cement and concrete production and its storage

As a result of firing pulverized coal in thermal power plants, enormous amounts of fly ash (FA) are produced as industrial waste. The release into the atmosphere and storage of this industrial waste remains one of the major environmental problems that threaten human health by contributing to air, water, and soil pollution. The recovery and reuse of FA in the construction industry is the only economic solution to the existing problem. In this study, the potential radiological risk caused by the usage of FA in concrete and cement production as a main component and its storage in landfill sites was evaluated for people and works by estimating radiological parameters (activity concentration and alpha index, annual effective doses, and the corresponding excess lifetime cancer risks) based on activity concentrations of terrestrial radionuclides in FA. Also, the radiological risk to the workers working in the FA landfill site was evaluated using the Residual Radioactivity Onsite 7.2 code. The average activity concentrations of terrestrial radionuclides in FA samples from the Tunçbilek lignite coal-fired thermal power plant at Kütahya province of Turkey were measured as 417, 156 and 454 Bq kg-1 for 226Ra, 232Th and 40K, respectively. When using up to 35% by mass of FA in cement and concrete, the average values of the radiological parameters revealed that they were within the recommended safety limits. However, code estimations showed that a regular worker in FA storage would be exposed to a total effective dose rate greater than 3 mSv y-1.

Investigation the effect of nanocarbon tube prepared from tea waste on microstructure and properties of cement mortar

Environmental contamination and the massive high cost of waste disposal have been a huge concern for scholars throughout the globe, prompting them to alternatives of recycling waste materials in various implementation fields. The rising expenditure on disposal and the shortage of naturally main resources such as aggregate have increased interest in reusing recycled waste materials to manufacture concrete and mortar. The annual consumption of a country's population of hundreds of tons of black tea results in considerable numbers of discarded teabags. These huge quantities are disposed in landfills without being recycled or otherwise used. Moreover, such landfills are considered one of the country's biggest global issues. Therefore, the aim of this experimental work is to investigate the influence of nanocarbon tube produced from tea waste as cement replacement materials in mortar mixtures. Cement mortar mixes contain four replacement levels (1%, 2%, 3%, and 4%) of cement with nanocarbon tube produced from tea waste. The compressive strength, ultrasonic pulse velocity, and water absorption were tested to demonstrate the effect of the nanocarbon tube made from recycled tea waste on the mechanical properties of the mortar mix. The fresh properties such as flow rate were evaluated in accordance to specific standards. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDX) analyses were performed to demonstrate the microstructure of the mixtures. The results show that the fresh properties (flowability) of mortar containing nanocarbon tubes from tea waste were improved with the increase of the replacement ratio. In addition, the compressive strength was improved by substitution of up to 2%. For the other levels of substitution, it decreased with an increasing replacement percentage. In contrast, the density had increased with the increase of substitution levels of the tea waste. Based on the results of the experiments, it seems that the suggested biomixture could increase the compressive strength of the material by up to 2% of the replacement at 28 days of curing.

Retrofitting of concrete for rigid pavement using bacterial: A meta-analysis

Cracking in tension causes damage to regular concrete. When the surface of the concrete cracks, liquids can enter and damage the structure. Remediating concrete in rigid pavements is time-consuming, costly, and challenging. Concrete cracking can be reduced using sustainable solutions, such as concrete bacteria. Using concrete bacteria is an innovative method for continuously retrofitting concrete, improving its durability, and reducing maintenance costs. Several studies have explored the possibilities of a wide range of bacteria and demonstrated concrete retrofitting. However, in these extensive studies of sustainable solutions, the role of concrete bacteria in retrofitting concrete for rigid pavement has not been clarified. This meta-analysis aims to compare and contrast the performance of various microorganisms in concrete restoration, considering the bacteria concentration, total concrete components, and water/cement ratio. Data from 371 articles were entered into the initial database and 37 articles into the final database for meta-analysis. Low concentrations (10 CFU/mL) of Bacillus subtilis increased the compressive strength after 28 days at 46.8 MPa, and the optimum concentration of Bacillus subtilis was 105 CFU/mL, resulting in an optimum compressive strength of 58.2 MPa after 28 days, an optimum water/cement ratio of 0.3, and the optimum total ingredients (cement, fine and coarse aggregates) ranging from 2000 to 2400 kg/m3. This meta-analysis study supports a new approach to selecting concrete bacteria and developing sustainable advances in concrete technology.

OCCUPATIONAL HEALTH AND SAFETY PRACTICES AMONG WORKERS IN BLOCK/CONCRETE CONSTRUCTION INDUSTRIES IN GOMBE METROPOLIS, GOMBE STATE, NORTHEAST, NIGERIA

Introduction

The block/concrete industry is often seen as a driver of economic growth in developing countries. A wide range of people mainly unskilled form the bulk of workers in these industries. According to the International Labor Organization, about 60,000 fatal accidents occur annually on these construction sites. This study aimed to determine the knowledge of hazards and practices of occupational safety measures among the workers in these industries.

Methodology

A descriptive cross-sectional study was done among 295 respondents selected using a multi-stage sampling technique. A structured, interviewer-administered-electronic questionnaire was used to obtain information from the respondents. Data were analyzed using SPSS version 23. Quantitative variables were summarized using tables and charts. The chi-square test was used to examine the relationship between socio-demographic characteristics and knowledge and practice. Statistical significance was determined at a p-value of ≤0.05.

Results

All the respondents were males, with a mean age of 28.9 ± 6.9 years. Most (70%) of the respondents have good knowledge while 49% have good practices in occupational safety. The age, level of education, and status of the worker were associated with knowledge of occupational hazards and practices. There was a statistically significant relationship between the knowledge of hazards and the practice of occupational safety (p = 0.000).

Conclusion

The knowledge of occupational hazards among the study participants was high while safety practices were not adequate. Therefore, the health authorities should educate workers on safety practices and encourage the management of the factories to provide safety measures to protect the workers.

Eco-friendly concrete incorporating palm oil fuel ash: Fresh and mechanical properties with machine learning prediction, and sustainability assessment

Rising natural resource consumption leads to increased hazardous gas emissions, necessitating the concrete industry's focus on sustainable alternatives like palm oil fuel ash (POFA) to replace cement. Also, advanced machine learning (ML) techniques can uncover previously unreported insights about the effects of POFA that may be missing from the literature. Hence, this study investigates the influence of varying concentrations of POFA on fresh and mechanical characteristics with quantifying ML approaches and microstructural performance, as well as the environmental impact of structural concrete. For this, cement substitutions of 5 %, 15 %, 25 %, 35 %, and 45 % (by weight of cement) were utilized. POFA enhanced the overall concrete workability, with slump increments ranging from approximately 9 %-55 % and compacting factor increments of 4 %-12 %. Mechanical performance of POFA concrete improved up to 25 % replacement levels, with the highest enhancements observed in compressive (4.5 %), splitting tensile (36 %), and flexural (31 %) strength, for the mix containing 15 % POFA. The finer particle size of POFA improved microstructural performance by reducing porosity, aligning with the enhanced mechanical strength. The environmental impact of POFA was assessed by measuring eCO2 emissions, revealing a potential reduction of up to 44 %. Incorporating 5 %-15 % POFA yielded ideal mechanical performance results, significantly enhancing sustainability and cost-effectiveness. Regarding the ML approach, it can be observed that a low regression coefficient (R2) contrasts sharply with the higher R2 values for the random forest (RF) and the ensemble model, indicating satisfactory precision prediction with experimental results.

Strength and durability characteristics of steel fiber-reinforced geopolymer concrete with addition of waste materials

In general, all countries in the world use ordinary Portland cement concrete for the construction purpose; this ordinary Portland cement (OPC) gives good mechanical properties and durability to the buildings. The binder cement and the filler aggregate are the ingredients widely used in the process of concrete. Natural resources are used to extract both filler and binder elements. In India, the fast-growing sectors like infrastructure, smart cities development, and real estate consume concrete in large quantity. Also, India is the second largest cement manufacturer in the world. The need of cement is increasing day to day, even though the country is manufacturing the cement more than the required demand. In an average, the cement manufacturing industries produce 6% of CO2; for example, if industries produce 1 tonne of cement, they also emit 1 tonne of CO2. This brings us environment changes and produces more pollution to the country. To handle this situation, after many research, geopolymer concrete has been developed. Geopolymer concrete (GC) is all about mixing of source materials to the alkaline solution. Fly ash (FA) that is collected from the power plant is used in GC. The FA-based GC gives more strength when compared to the normal OPC concrete. Under ambient and steam curing, the compression, flexural strength, and tensile strength of FAGC and steel-reinforced geopolymer (SFGC) were tested and results were compared with normal concrete. FAGC mix proportions were studied under different ratios for sodium hydroxide and sodium silicate with 10 M. When compared with normal cement, the strength given by FAGC achieved good strength under ambient temperature. FAGC was further tested for the acid, sulfate, water absorption, and sorptivity test and compared with OPC concrete.

Evaluation of sealants to mitigate the release of per- and polyfluoroalkyl substances (PFAS) from AFFF-impacted concrete: Characterization and forecasting

Per- and polyfluoroalkyl substances (PFAS) within concrete pads impacted by historical firefighting training using aqueous film-forming foam (AFFF) may be potential secondary sources of PFAS due to surficial leaching. This study aimed to (i) characterize the effectiveness of two commercially available sealants (Product A and Product B) in mitigating leaching of five PFAS (e.g., PFOS, PFOA, PFHxS, PFHxA, 6:2 FTS) from concrete surfaces at the laboratory-scale, and (ii) develop a model to forecast cumulative leaching of the same five PFAS over 20 years from sealed and unsealed concrete surfaces. Laboratory trials demonstrated that both sealants reduced the surficial leaching of the five PFAS studied, and Product B demonstrated a comparatively greater reduction in surface leaching than Product A as measured against unsealed controls. The cumulative PFOS leaching from an unsealed concrete surface is estimated by the model to be about 400 mg/m2 over 20 years and reached asymptotic conditions after 15 years. In contrast, the model output suggests asymptotic conditions were not achieved within the modeled time of 20 years after sealing with Product A and 85% of PFOS was predicted to have leached (∼340 mg/m2). Negligible leaching of PFOS after sealing with Product B was observed ( < 5 × 10-9 mg/m2). Results from modeled rainfall scenarios suggest PFAS leachability is reduced from sealed versus unsealed AFFF-impacted concrete surfaces.

Durability of concrete incorporating organic light-emitting diode (OLED) display waste as cement binder replacement

The use of supplementary cementitious materials is customary in contemporary concretes. Different industrial by-products and waste materials have been investigated earlier for such applications. In this paper, the use of organic light-emitting diode glass (OLED) display waste as a partial replacement of cement binder in concretes has been explored. Concretes with 10%, 20%, and 30% substitution (by weight) of ordinary Portland cement (OPC) by OLED powder were developed, and the resulting mechanical properties and durability characteristics were evaluated. The results showed that OLED addition leads to strength improvement of up to 8% after 28-day age. Also, the resistance to chloride-ion penetration and sulfate attack improved considerably. The chloride binding capacity for the developed concretes was also investigated. It was demonstrated that the OLED powder incorporation is beneficial in improving the corrosion resistance of the modified concrete. The enhanced mechanical and durability properties of modified concrete point toward the excellent performance of OLED-incorporated concrete for improved service life. Incorporating OLED display waste in concrete as a partial cement replacement can also reduce environmental burden and concrete cost.

Spatiotemporal dynamics of abstract and concrete semantic representations

Dual Coding Theories (DCT) suggest that meaning is represented in the brain by a double code: a language-derived code in the Anterior Temporal Lobe (ATL) and a sensory-derived code in perceptual and motor regions. Concrete concepts should activate both codes, while abstract ones rely solely on the linguistic code. To test these hypotheses, the present magnetoencephalography (MEG) experiment had participants judge whether visually presented words relate to the senses while we recorded brain responses to abstract and concrete semantic components obtained from 65 independently rated semantic features. Results evidenced early involvement of anterior-temporal and inferior-frontal brain areas in both abstract and concrete semantic information encoding. At later stages, occipital and occipito-temporal regions showed greater responses to concrete compared to abstract features. The present findings suggest that the concreteness of words is processed first with a transmodal/linguistic code, housed in frontotemporal brain systems, and only after with an imagistic/sensorimotor code in perceptual regions.

Feasibility of utilising porous aggregates for carbon sequestration in concrete

Carbon sequestration in concrete has attracted increasing research attention. CO₂ may be permanently stored in the cement paste of concrete by chemical reaction with the hydration products of cement, but this method leads to a significant reduction of the pH value of the concrete pore solution and may thus put the steel reinforcement at risk of corrosion. This paper proposes a new method for carbon sequestration in concrete using the space in porous coarse aggregates; the method involves presoaking the porous aggregates in an alkaline slurry and then using them for CO₂ sequestration. The potential of utilising the space in the porous aggregates and the cations in the alkaline slurry is first discussed. An experimental study aiming to demonstrate the feasibility of the proposed method is then presented. The results show that CO₂ can be successfully sequestrated and fixed as CaCO₃ in the open pores of coarse coral aggregate presoaked in a Ca(OH)₂ slurry. The amount of CO₂ sequestration by concrete produced using the presoaked coral aggregate was around 20 kg/m³. Importantly, the proposed CO₂ sequestration method did not affect the strength development of the concrete or the pH value of the concrete pore solution.

Towards quantifying the effect of pump wave amplitude on cracks in the Nonlinear Coda Wave Interferometry method

In Non-Destructive Testing and Evaluation (NDT&E), an ultrasonic method called Nonlinear Coda Wave Interferometry (NCWI) has recently been developed to detect cracks in heterogeneous materials such as concrete. The underlying principle of NCWI is that a pump wave is used to activate the crack breathing which interact with the source probe signal. The resulting signal is then measured at receiver probes. In this work, a static finite element model (FEM) is used to simulate the pump wave/crack interaction in order to quantifies the average effect of the pump waves on a crack. By considering both crack opening and closure phases during the dynamic pump wave excitation, this static model aims to determine the pump stress amplitude for a given relative crack length variation due to the dynamic pump wave excitation at different amplitudes. Numerical results show, after reaching certain stress amplitude, a linear relationship between the relative crack length variation and the equivalent static load when considering a partially closed crack at its tips. Then, numerical NCWI outputs, e.g., the relative velocity change θ and the decorrelation coefficient K_d, have been calculated using a spectral element model (SEM). These results agree with previously published experimental NCWI results derived for a slightly damaged 2D glass plate.

Using SWMM for emergency response planning: A case study evaluating biological agent transport under various rainfall scenarios and urban surfaces

To assist in emergency preparedness for a biological agent terrorist attack or accidental pathogen release, potential contaminant levels and migration pathways of spores spread by urban stormwater were evaluated using a Storm Water Management Model (SWMM) of U.S. Coast Guard Base Elizabeth City, North Carolina. The high temporal-spatial resolution SWMM model was built using spore concentrations in stormwater runoff from asphalt, grass, and concrete collected from a point-scale field study. The subsequent modeled contamination scenarios included a notional plume release and point releases mimicking the field study under three rainfall conditions. The rainfall scenarios included a 6-hour natural rainfall event on Dec. 8, 2021 and two design storms (2-year and 100-year events). The observed spore concentrations from asphalt and concrete from the actual field experiment were applied to calibrate the washoff parameters in the SWMM model, using an exponential washoff function. The calibrated washoff coefficient (c₁) and exponent (c₂) were 0.01 and 1.00 for asphalt, 0.05 and 1.45 for grass, and 2.45 and 1.00 for concrete, respectively. The calibrated SWMM model simulated spore concentrations in runoff at times and magnitudes similar to the field study data. In the point release modeled scenario, the concrete surface generated 55.6% higher average spore concentrations than asphalt. Similarly, in the field experiment, a 175% (p < 0.05) higher average spore concentration in surface runoff was observed from concrete than from asphalt. This study demonstrates how SWMM may be used to evaluate spore washoff from urban surfaces under different precipitation amounts, intensities, and durations, and how visualized spatial migration pathways in stormwater runoff may be used for emergency planning and remediation.

Deep learning-based prediction for time-dependent chloride penetration in concrete exposed to coastal environment

The application of deep learning methods in civil engineering has gained significant attention, but its usage in studying chloride penetration in concrete is still in its early stages. This research paper focuses on predicting and analyzing chloride profiles using deep learning methods based on measured data from concrete exposed for 600 days in a coastal environment. The study reveals that Bidirectional Long Short-Term Memory (Bi-LSTM) and Convolutional Neural Network (CNN) models exhibit rapid convergence during the training stage, but fail to achieve satisfactory accuracy when predicting chloride profiles. Additionally, the Gate Recurrent Unit (GRU) model proves to be more efficient than the Long Short-Term Memory (LSTM) model, but its prediction accuracy falls short compared to LSTM for further predictions. However, by optimizing the LSTM model through parameters such as the dropout layer, hidden units, iteration times, and initial learning rate, significant improvements are achieved. The mean absolute error (MAE), determinable coefficient (R²), root mean square error (RMSE), and mean absolute percentage error (MAPE) values are reported as 0.0271, 0.9752, 0.0357, and 5.41%, respectively. Furthermore, the study successfully predicts desirable chloride profiles of concrete specimens at 720 days using the optimized LSTM model.

Diffusion potentials in saturated hardened cement paste upon chloride exposure

The diffusion potentials can cause significant errors in corrosion-related investigations of reinforced concrete structures (half-cell potential mapping, potentiometric sensors). Therefore, an improved understanding of the diffusion potentials in cement-based materials is needed. This study investigates the permselective behavior and its implication for the arising diffusion potentials. A diffusion cell is used to study the diffusion potentials in hardened cement pastes with imposed NaCl gradients. The cement pastes consist of ordinary Portland cement (OPC) and blast furnace cement (BFC) with water-cement ratios of 0.30-0.70. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is used to determine the concentration profiles of Cl, Na, K and Ca in the cement pastes with a high spatial resolution (100 µm). For the BFC pastes, considerable differences in the Cl- and Na+ mobilities are found, indicating their permselective behavior. Despite the permselective behavior, the measured diffusion potentials are small (- 6 to + 3 mV) for all investigated cement pastes due to the high pH levels (13-14) in the pore solutions. However, when using the diffusion cell, the pH differences interfere with the measured diffusion potentials. The interfering pH differences need to be considered for an accurate measurement of the diffusion potentials in cement pastes.

Recycling of water treatment sludge in concrete: The role of water-binder ratio from a nanoscale perspective

For eutrophic water bodies, potassium permanganate is an effective pre-oxidant to remove algae and its residue in water treatment sludge. Recycling water treatment sludge in concrete is an environmentally friendly and high-value utilization measure. However, little research has been done on the effect of manganese-rich drinking water sludge ash (DWSA) on concrete. The effect of water-binder ratio (w/b) on strength, shrinkage and microstructural characteristics of concrete containing DWSA was investigated, and the structural behavior was explained from a nanoscale perspective. The results show that recycling 10 % DWSA in concrete improved the strength and shrinkage resistance of the samples. Reducing the w/b effectively increased the strength of DWSA-modified concrete and reduced the shrinkage deformation. The paste with high w/b had higher contents of non-evaporated water and calcium hydroxide, as well as higher reaction degree of DWSA. Nanoscale characterization shows that reducing the w/b reduced the volume fraction of pore and unhydrated phases in the matrix and increased the proportion of high-density C-S-H. Meanwhile, reducing the w/b also reduced the interfacial transition zone width of DWSA-modified concrete. Recycling DWSA in concrete effectively reduced the total carbon footprint and cost of the mixture. The combined application of reducing the w/b and incorporating DWSA effectively improved the economic and environmental benefits of concrete material. For the concrete modified with 10 % DWSA (w/b = 0.3), its cost and carbon emissions are reduced by 14 %-21 % and 19 %-25 % compared with the reference sample, respectively. Overall, this study reveals the action mechanism of DWSA in cement system at different w/b from nanoscale perspective, and gives a new insight on determining the optimal w/b in full-scale application of DWSA concrete.

Quantification of the variability and penetration of per- and poly-fluoroalkyl substances through a concrete pad

Historical use of aqueous film forming foams (AFFF) containing per- and poly-fluoroalkyl substances (PFAS) for fire-fighting activities has contributed to widespread contamination of infrastructure which can represent an ongoing source of PFAS to the surrounding environment. A concrete fire training pad with historical use of Ansulite and Lightwater AFFF formulations had PFAS concentrations measured to quantify spatial variability of PFAS within the pad. Surface chips and whole cores of concrete through to the underlying aggregate base were collected over the 24 × 9 m concrete pad and depth profiles of PFAS concentrations in nine cores were analysed. PFOS and PFHxS dominated the PFAS for surface samples, along the depth profile of cores and in the underlying plastic and aggregate material, with substantial variability in the concentrations of PFAS in the samples. Although there was variability of individual PFAS along the depth profile, higher surface concentrations of PFAS generally followed the designed movement of water across the pad. Total oxidisable precursor (TOP) assessments of one core indicated additional PFAS were present along the entire length of the core. This study highlights concentrations of PFAS (up to low μg/kg) from historical use of AFFF can occur throughout concrete, with the variable concentrations throughout the profile.

PFAS contaminated asphalt and concrete - Knowledge gaps for future research and management

Per- and polyfluoroalkyl substances (PFAS) are now widespread in the environment. Globally, airfields and paved firefighting training surfaces are particularly affected due to extensive use of aqueous film forming foams (AFFF). This PFAS contamination in exposed concrete and asphalt has not been widely addressed. This review focusses on PFAS interaction with concrete and asphalt, traversing extraction, analytical identification/quantification, PFAS fractionation via differential adsorption on organic and inorganic substrates, and reuse options for contaminated concrete and asphalt. A total of 24 knowledge gaps and management challenges for concrete and asphalt characterisation and management have been identified.

Bioconcrete-Enabled Resilient Construction: a Review

Concrete, the ubiquitous cementitious composite though immensely versatile, is crack-susceptible. Cracks let in deleterious substances causing durability issues. Superseding conventional crack-repair methods, the innovative application of microbially induced calcium carbonate precipitation (MICCP) stands prominent, being based on the natural phenomenon of carbonate precipitation. It is eco-friendly, self-activated, economical, and simplistic. Bacteria inside concrete get activated by contacting the environment upon the crack opening and filling the cracks with calcium carbonate-their metabolic waste. This work systematizes MICCP's intricacies and reviews state-of-the-art literature on practical technicalities in its materialization and testing. Explored are the latest advances in various aspects of MICCP, such as bacteria species, calcium sources, encapsulations, aggregates, and the techniques of bio-calcification and curing. Furthermore, methodologies for crack formation, crack observation, property analysis of healed test subject, and present techno-economic limitations are examined. The work serves as a succinct, implementation-ready, and latest review for MICCP's application, giving tailorable control over the enormous variations in this bio-mimetic technique.

Survival of livestock-associated methicillin-resistant Staphylococcus aureus CC398 on different surface materials

BACKGROUND

Zoonotic livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) is widely spread in pig herds in many countries. However, the knowledge regarding the survival of LA-MRSA in the pig farm environment is currently limited. The aim of this study was to assess the survival of LA-MRSA on different surface materials found in the farm environment. The study investigated the survival of two different LA-MRSA strains belonging to the clonal complex (CC) 398 on four different surfaces: stainless steel, polypropylene plastic, K30 concrete and commercial concrete disk coupons. The survival of the bacteria over time was determined by the viable count method and, where possible, fitting a model to the observed data by using nonlinear least squares method to calculate the half-life ([Formula: see text]) for different strain and material combinations.

RESULTS

The study showed that the half-life of the bacteria was longer on polypropylene plastic ([Formula: see text]=11.08-15.78 days) than on stainless steel ([Formula: see text]=2.45-7.83 days). On these materials, both LA-MRSA strains survived through the 14 week observation period. The bacterial decay was fastest on the concrete surfaces, where LA-MRSA became undetectable after 3-9 weeks.

CONCLUSIONS

The survival of LA-MRSA in the pig farm environment may be affected by different surface materials. A more frequent sampling protocol (< 7 days) is needed to determine the half-life on concrete surfaces.

Effects of chopped CFRP fiber on mechanical properties of concrete

Enhancing concrete's mechanical properties has become a prominent field in recent years. Numerous studies investigated the possibility of enhancing the mechanical properties of concrete by adding additive materials. Few studies investigated the effects of copped CFRP on the tensile strength of normal-strength concrete (NSC) and low-strength concrete (LSC). In this study, the effects of Chopped Carbon Fiber Reinforced Polymer (CCFRP) on the mechanical properties of LSC and NSC were investigated. The method of the study was experimentally investigating the effects of CCFRP on the mechanical properties of LSC and NSC. Different volume fractions (0%, 0.25%, 0.5%, and 0.75%) of chopped carbon fibers were added to the concrete mix for the 13 MPa and 28 MPa concrete grades, and five mix trials were conducted to achieve concrete with 13 MPa and 28 MPa. The ratios (1:1.5:2.5) for the normal strength mix and (1:2.6:4.1) for the low strength mix were chosen. Three tests were conducted to evaluate the effects of chopped CFRP on the mechanical properties of concrete: compressive strength, tensile strength, and flexural strength. A total of 120 pieces were cast, including 24 beams, 48 cubes, and 48 cylinders. The casted cubes were 15 × 15 × 15 cm and the cylinders were 15 cm in diameter and 30 cm in length. Prism beams with a 15 × 15 cm cross-section and a 56 cm length were tested under a single point load. The samples were tested at 7 and 28 days of age, and the sample density was recorded. The results revealed that adding 0.25% CCFRP increased the compressive strength of LSC from 9.5 MPa to 11.2 MPa which is about 10% enhancement and slightly affected the compressive strength of NSC by about 5%. On the other hand, adding 0.25% CCFRP to both LSC and NSC increased split tensile strength from 2.5 MPa to 3.6 MPa which is about 44% enhancement for NSC and 16.6% for LSC. Similar improvements were made in flexural strength of normal strength increased from 4.5 MPa to 5.4 MPa. Whereas the effects on LSC were unremarkable. As such, this study recommends 0.25% CCFRP fiber as the ideal dosage.

Inter-muscular coordination during running on grass, concrete and treadmill

Running is an exercise that can be performed in different environments that imposes distinct foot-floor interactions. For instance, running on grass may help reducing instantaneous vertical impact loading, while compromising natural speed. Inter-muscular coordination during running is an important factor to understand motor performance, but little is known regarding the impact of running surface hardness on inter-muscular coordination. Therefore, we investigated whether inter-muscular coordination during running is influenced by running surface. Surface electromyography (EMG) from 12 lower limb muscles were recorded from young male individuals (n = 9) while running on grass, concrete, and on a treadmill. Motor modules consisting of weighting coefficients and activation signals were extracted from the multi-muscle EMG datasets representing 50 consecutive running cycles using non-negative matrix factorization. We found that four motor modules were sufficient to represent the EMG from all running surfaces. The inter-subject similarity across muscle weightings was the lowest for running on grass (r = 0.76 ± 0.11) compared to concrete (r = 0.81 ± 0.07) and treadmill (r = 0.78 ± 0.05), but no differences in weighting coefficients were found when analyzing the number of significantly active muscles and residual muscle weightings (p > 0.05). Statistical parametric mapping showed no temporal differences between activation signals across running surfaces (p > 0.05). However, the activation duration (% time above 15% peak activation) was significantly shorter for treadmill running compared to grass and concrete (p < 0.05). These results suggest predominantly similar neuromuscular strategies to control multiple muscles across different running surfaces. However, individual adjustments in inter-muscular coordination are required when coping with softer surfaces or the treadmill's moving belt.

Suitability of remediated heat-treated soil in concrete applications

Significant quantities of soil are adversely impacted by organic contaminants, including per- and poly-fluoroalkyl substances (PFAS). One proven technology for remediating PFAS affected soils is excavation and heat-treatment which destroys the PFAS, but renders the soil as an industrial waste that is normally diverted to landfill. This study investigated alternative uses for heat-treated industrial waste (HIW) soils as components in concrete, as aggregate replacement and as partial substitution of cement binder. At a replacement rate of 100% fine aggregate and ≈15% coarse aggregate, concretes made with HIW soil exhibited a strength of 47.2-48.3 MPa after 28 days' curing, compared with a reference concrete of 49.7-53.1 MPa, making the HIW ideal for aggregate replacement. Overall, the study demonstrated a novel, holistic approach to (1) remediating PFAS-affected soils, (2) diverting contaminated soil away from landfill, (3) reducing the use of high quality quarried concrete aggregates and (4) producing normal-strength concretes with a lower embodied carbon footprint than existing approaches. This study reveals that in Australia, up to 93% of all contaminated soil currently sent to landfill annually could instead be used a resource for mid-strength concretes, suitable for many applications.

Cement Composites with Carbon-based Nanomaterials for 3D Concrete Printing Applications - A Review

3D concrete printing (3DCP) is an emerging additive manufacturing technology in the construction industry. Its challenges lie in the development of high-performance printable materials and printing processes. Recently developed carbon-based nanomaterials (CBNs) such as graphene, graphene oxide, graphene nanoplatelets, and carbon nanotubes, have various applications due to their exceptional mechanical, chemical, thermal, and electrical characteristics. CBNs also have found potential applications as a concrete ingredient as they enhance the microstructure and modify concrete properties at the molecular level. This paper focuses on state-of-the-art studies on CBNs, 3DCP technology, and CBNs in conventional and 3D printable cement-based composites including CBN dispersion techniques, concrete mixing methods, and fresh and hardened properties of concrete. Furthermore, the current limitations and future perspectives of 3DCP using CBNs to produce high-quality composite mixtures are discussed.

Behaviour of rubberised concrete with waste clay brick powder under varying curing conditions

Recently, there has been a worldwide scarcity of pure water for curing concrete and this has called for alternative curing conditions including utilisation of sea water. An experimental study was conducted to examine the mechanical behaviour of rubberised concrete with waste clay brick powder (WCBP) under different conditions of curing including water and sea water. The samples of rubberised concrete incorporated with WCBP were cured in water and sea water for 90 days curing period. The findings showed that the conventional and modified concrete mixtures which were cured in sea water illustrated reduced compressive and split tensile strengths compared with corresponding mixes cured in water. Among specimens cured in each curing condition, concrete mixes with 5% WCBP showed increased compressive and split tensile strengths compared with the control concrete mixes. The lowest compressive and split tensile strength findings were noticed with rubberised concrete incorporated with WCBP. The comparisons of densities of specimens cured in water and sea water showed no significant distinctions between the curing conditions. Compressive strength seemed to be less sensitive to conditions of curing compared with split tensile strength. From the findings, minor reductions in compressive strengths for samples cured in sea water compared with those cured in water were suggested to be reflections of possibility of utilising sea water as a curing agent in areas where pure water is very scarce. The findings in this study seem to suggest that the use of sea water in concrete curing should not be feared and could be welcome, particularly in offshore constructions and isolated islands.

Environmental, economic and experimental assessment of the valorization of dredged sediment through sand substitution in concrete

The integrated life cycle assessment (LCA), life cycle cost assessment (LCC) and laboratory-based experimental assessment were applied to provide insight for early stage decision-making on the valorization of the dredged sediments. The objective was to find a viable and sustainable solution for the valorization of the dredged sediment in concrete, holding up a certain level of standard concrete performance without compromising in terms of economy and environment. For the sensitivity analysis, parametric life cycle inventories were developed to assess the sensitivity of environmental and economic costs to the rate of sand substitution by sediment, as well as the variations in the concrete components. The workability of fresh concrete and the compressive strength of hardened concrete at 28 days were assigned as the quality indicators to evaluate the influence of sand substitution by sediment on the concrete performance. The compressive strength evaluation in the laboratory demonstrated that a maximum rate of sand substitution in concrete up to 40 % by predominantly sandy sediment could sustain the concrete strength class. However, LCA and LCC negated the rate of sand substitution by sediment higher than 20 %. The integrated environmental, economic, and experimental assessments demonstrated that the substitution of sand by predominantly fine sediment downgrades the strength class of concrete, even in the low rate of incorporation (10 %) and increases the environmental and economic costs. Inferred from the results, the maximum rate of sustainable sand substitution by sediment in concrete could be optimized through a compromise between the expected mechanical strength and workability of the concrete, the economic and environmental impacts of the superplasticiser and the sediment transport. Overall, integrating environmental and economic cost assessments into the laboratory-based assessment of the valorization scenarios would determine the threshold for the sustainable rate of incorporation of sediment in valorization scenarios.

A two-step approach for calculating chloride diffusion coefficient in concrete with both natural and recycled concrete aggregates

This paper presents an analytical approach to calculate the effective diffusion coefficient of chlorides in concrete with both natural and recycled concrete aggregates. In the approach the concrete is treated as a composite consisting of three phases, namely mortar, natural aggregate plus interfacial transition zone, and recycled concrete aggregate plus interfacial transition zone. The effective diffusion coefficient of chlorides in the composite is calculated through two steps. The first step is to calculate the effective diffusion coefficients of chlorides in the natural aggregate plus interfacial transition zone and in the recycled concrete aggregate plus interfacial transition zone by using multilayer spherical approximation, the results of which provide the information about the quality of recycled concrete aggregate in terms of chloride penetration resistance. The second step is to calculate the effective diffusion coefficient of chlorides in the three-phase concrete composite by using effective medium approximation, the results of which provide the information about the influence of recycled concrete aggregate on the diffusivity of recycled aggregate concrete. The analytical expression of the effective diffusion coefficient is derived and carefully compared with the results obtained from both the experiments and numerical simulations, which demonstrates that the present analytical model is rational and reliable. The analytical expression presented can be used to predict the service life of recycled aggregate concrete exposed to chloride environment.

Life cycle assessment of material footprint in recycling: A case of concrete recycling

Meeting the current demand for concrete requires not only mining tons of gravel and sand, but also burning large amounts of fossil fuel resources in cement kilning. Consequently, concrete recycling is crucial to achieving a material-efficient society, especially with the application of various categories of concrete and the goal of phasing out fossil fuels. A comparative life cycle assessment (LCA) is used to assess the engineering material footprint (EMF) and the fossil fuel material footprint (FMF) in closed-loop recycling of three types of concrete: siliceous concrete, limestone concrete, and lightweight aggregate concrete. This study aims to investigate the impact of (i) concrete categories, (ii) methods to model recycling, and (iii) using renewable energy sources on the material footprint in concrete recycling. The results highlight that the concrete recycling system can reduce 99% of the EMF and 66-93% of the FMF compared with the baseline system, in which concrete waste is landfilled. All three recycling modeling approaches indicate that concrete recycling can considerably reduce EMF and FMF compared with the baseline system, primarily resulting from the displacement of virgin raw materials. Using alternative diesels is more sensitive than adopting renewable electricity in reduction of the FMF in concrete recycling. Replacing diesel with electrolysis- and coal-based synthetic diesel for concrete recycling could even increase the FMF, while using biodiesel made from rapeseed and wood-based synthetic diesel can reduce 47-51% and 84-89% of the FMF, respectively, compared to the virgin diesel-based recycling system. Finally, we discussed the multifunctionality and rebound effects of recycling, and double-counting risk in material and energy accounting.

Recycling/reuse of plastic waste as construction material for sustainable development: a review

The exponential rise in the production of plastic and the consequential surge in plastic waste have led the scientists and researchers look out for innovative and sustainable means to reuse/recycle the plastic waste in order to reduce its negative impact on environment. Construction material, converting waste plastic into fuel, household goods, fabric and clothing are some of the sectors where waste plastic is emerging as a viable option. Out of these, construction material modified with plastic waste has garnered lot of attention. Modification of construction material with plastic waste serves a dual purpose. It reduces the amount of plastic waste going to landfills or litter and secondly lessens the use of mined construction materials, thereby mitigating the negative impact of construction industry on environment. This paper summarizes the developments with regard to the use of plastic waste as a constituent of construction material. Inclusion of plastic waste as a binder, aggregate, fine aggregate, modifier or substitute of cement and sand in the manufacturing of bricks, tiles, concrete and roads has been comprehensively reviewed. Also, the influence of addition of plastic waste on strength properties, water absorption, durability, etc. has been thoroughly discussed. The research studies considered for this review have been categorized based on whether they dealt with the use of plastic waste for bricks and tiles or in concrete for road construction.

Development of concrete reference material for quality assurance/quality control of gamma radioactivity measurement for nuclear power plant decommissioning waste

The Korea Research Institute of Standards and Science has developed a new concrete reference material (RM) for measuring gamma-emitting radionuclides, such as 134Cs, 137Cs, 65Zn, 241Am, and 60Co, to improve and maintain the quality assurance and quality control of the radioactivity measurement in radioactive waste generated during the decommissioning of nuclear power plants. In this study, cement, SiO2, and bentonite, which are the main components of concrete, were mixed in an appropriate ratio with radionuclides. For certification and homogeneity assessment, 10 bottles were randomly selected, two sub-samples were collected from each bottle, and radionuclides were measured via HPGe gamma spectrometry. The results of the homogeneity tests using a one-way analysis of variance on 241Am, 134Cs, 137Cs, 65Zn, and 60Co in the concrete RM fulfilled the requirements of ISO Guide 35. Coincidence summing and self-absorption correction were performed on measurement results by introducing the Monte Carlo efficiency transfer code and Monte Carlo N-Particle transport code. The reference values for five radionuclides (60Co, 65Zn, 241Am, 134Cs, and 137Cs) in the RM were in the range of 15-40 Bq/kg, and the expanded uncertainty was within 10% (k = 2). To the best of our knowledge, this was the first study to develop concrete RM for measuring gamma-emitting radionuclides.

Advances on concrete strength properties after adding polypropylene fibers from health personal protective equipment (PPE) of COVID-19: Implication on waste management and sustainable environment

Using Health personal protective equipment (PPE) such as face masks, safety foot shoes and protective suits has expanded dramatically due to COVID-19 pandemic leading to a widespread distribution of the PPE, particularly the face masks, in the environments including streets, dump sites, seashores and other risky locations. The environmental degradation of polypropylene, the essential plastic component in single-use face masks (SUM), takes between 20 and 30 years and thus it is essential to develop experimental approaches to recycle the polypropylene or to reuse it in different ways. This paper explores the integration of SUM into concrete structures to improve its mechanical properties. We first to cut the inner nose wire and ear loops, then distribute the PPE material among five different mixed styles. The PPE were applied by volume at 0%, 1%, 1.5%, 2.0%, and 2.5%, with tests focusing on UCS, STS, FS, and PV to determine the concrete's overall consistency and assess the improvement in its mechanical properties. The results showed that adding PPE improves the strength properties and general performance of the concrete specimens. The pattern of rising intensity started to fade after 2%. The findings demonstrated that adding PPE fibers enhanced the UCS by 9.4% at the optimum 2% PPE. The PPE fibers, on the other side, are crucial in calculating the STS and FS of the reinforcement concrete.

A bibliometric analysis of research trends in life cycle assessment of fresh concrete and mortar during 1997-2021

The construction industry relies heavily on concrete as a fundamental material. According to the shift towards environmental sustainability in recent years, studies on life cycle assessment (LCA) of concrete and mortar and reducing their environmental impacts have increased significantly. This paper provides insights into studies performed in LCA of fresh concrete and mortar until 2021 by using a bibliometric method. To achieve this goal, 283 documents were selected from the Scopus database for bibliometric analysis. VOSviewer and Publish or Perish tools were used to perform bibliometric analysis and data visualization. Various aspects of existing documents, including top sources, countries, and authors, were analyzed. Citation analysis was conducted to identify articles with the most citations. Co-occurrence analysis has been used for analyzing keywords to identify research trends and future research directions. The number of studies in this area has grown significantly in recent years, according to the results. Among all subject areas, engineering and environmental science are recognized as the main areas of existing researches. Journal of Cleaner Production is one of the leading journals in this field. Among the productive countries, the USA is recognized as the leader. However, de Brito J. from Portugal is the most prolific author in this field. The most influential document in this field was written by Habert et al., which includes the highest citations among all documents. Keyword analysis indicates that "Fly Ash" has the most occurrence among all keywords. However, "Recycled Aggregates" recorded the highest annual average growth rate in recent years.

Tritium transport in non-saturated concrete under temperature fluctuations

This work studies the effect of the environmental conditions on tritium transport in concrete cells storing radioactive waste. Water with high concentration of tritium was leaking from drains situated in these concrete cells, which indicates flow of water and tritium transport in these cells. 2D numerical models together with temperature and humidity measurements suggested that this leak of tritiated water is caused by a combination of thermo-hydraulic processes occurring in the unsaturated concrete, that comprise capillary rise from the groundwater, evaporation and condensation due to temperature gradients caused by seasonal temperature fluctuations outside. Following this conceptual model, numerical models have been developed to study the tritium transport in the concrete. Model results show that tritium concentration varies according to evaporation and condensation processes inside the concrete cell. An analysis of tritium fluxes revealed that differences in transport mechanisms in liquid and gas can cause concentration gradients of tritium in zones of high water content very different or even opposite to those in zones with low water content. From our numerical calculations, we conclude that there is no release of tritiated water to the groundwater.

A review on sustainable use of agricultural straw and husk biomass ashes: Transitioning towards low carbon economy

In order to mitigate the problems associated with the deposition of biomass ashes, it becomes essential to use these materials efficiently. One solution to the problem is utilization of these wastes in the concrete industry. Due to the massive development of infrastructure, the demand for cement is tremendously rising which results in the surge of cement concrete by 30 billion tonnes every year. Plant-based straw and husk ashes are residual waste containing high amounts of silica, which can also be accommodated as a pozzolanic material in concrete. This study presents a complete review of various husk and straw ashes and their impacts on the fresh and hardened properties of concrete including its preparation, microstructure, workability, compressive strength, splitting tensile strength and flexural strength. Special emphasis has been given to the durability characteristics of concrete focussing on porosity, water penetration, carbonation, acid resistance, sulphate, and chloride attack. The data gathered shows that fineness of ashes provides filler and pore refinement effect and gains additional hydration products, resulting in an improvement of the mechanical and durability properties of concrete. The addition of ashes as supplementary cementitious materials in concrete enhances the mechanical performance up to a certain replacement. The optimum level of replacement for rice husk ash, wheat straw ash, and sugarcane straw ash was observed at 10-20%. While wheat husk ash, groundnut husk ash, rice straw ash, and millet husk ash provide optimum strength gains at 10% replacement of OPC. An increase in the replacement content of mostly ashes has a positive effect on water absorption and resistance to acid, sulphate, and chloride attacks.

Geopolymer concrete as green building materials: Recent applications, sustainable development and circular economy potentials

Environmental degradation and increased greenhouse gas emissions force communities to achieve sustainable green building and construction materials. The environmental and financial aspects of sustainable development and circular economy strongly depend on the recycling of wastes into new products. Geopolymers gained increasing attention because of their eco-friendly and superior mechanical characteristics and their ability to utilize numerous wastes as precursors. Although there are numerous studies on geopolymer, little attention was focused on geopolymer concrete (GeoC). Hence, This review follows the Preferred Reporting Items for Systematic Reviews (PRISMA) investigated in detail GeoC. The first part of this study explores the recent synthesis processes, different precursors, and applications of geopolymer concrete (GeoC) in numerous sectors as well as the mechanical, microstructural, and physical related characteristics of GeoC developed from various wastes. The second part discusses in detail the contributions of GeoC to the sustainable development goals (SDGs) stated by the United Nations. The last part discusses the implementation of different wastes to develop GeoC-based circular economy to provide recommendations and prospects for GeoC science and technology. An eco-friendly, sustainable, structurally sound GeoC matrixes can be developed from numerous industrial, municipal, and agricultural wastes. Such GeoC is a good candidate to traditional concrete and some other building materials. GeoC is strongly contribute into 12 SDGs of the main 17 SDGs. Optimizing the elements of GeoC would decrease its cost and thus promote a green circular economy.

An Overview of Characterisation, Utilisation, and Leachate Analysis of Clinical Waste Incineration Ash

As industrial globalisation and waste output continue to grow, solid waste management is one of the most pressing worldwide environmental challenges. Solid wastes include both the heterogeneous mass of urban throwaways and the homogeneous accumulations of agricultural, industrial, and mineral wastes. Clinical waste (CW) has a significant negative influence on both human health and the environment. To dispose hazardous CW, a proper waste management system should be necessary, and incineration should be the best possible option for reducing the volume of this hazardous waste. Incineration is being developed in Malaysia as a means of disposing clinical and hazardous waste. Currently, 170 common CW treatment facilities with 140 incinerators are accessible around the country. The combustion procedure kills pathogens and reduces waste volume and weight, but it leaves a solid residue known as clinical waste ash (CWA), which raises heavy metal, inorganic salt, and organic compound levels in the environment. Because metals are not eliminated during incineration, dumping CWA in a landfill could contaminate groundwater. Leachate is the liquid created when waste decomposes in a landfill and water filters through it. The most common method of disposing of CW ashes is to transfer them to a landfill. Landfills should install a top cover after closure for hazardous waste landfills. Due to a lack of space and the high expense of land disposal, recycling technologies and the reuse of ash in various systems have developed. Clinical waste incineration fly ash (CWIFA), a solid waste substance from CW incineration, typically includes mobile heavy metals and can cause significant pollution when reused. The standard requirement for removing CWIFA in dumpsites should be below the metal limit stated by the U.S. Environmental Protection Agency (USEPA). Much recent research on the usage of CWIFA has concentrated on mitigating their effects on the environment. Several studies have confirmed the utilisation of CWIFA in the construction field and agriculture to reduce the leaching of its hazardous components into the environment. Compressive strength decreased with the percentage amount of CWIFA due to the substitution of cement with CWIFA. CWIFA mix with 20% cement is the broad-scale application of CWIFA for geotechnical constructions. Heavy metals (Cd, Cu, Ni, Pb, and Zn) are strongly immobilised by the cementitious matrix. Solidification/stabilisation (S/S) materials can be dumped in landfills with less environmental protection than untreated waste. When utilising a CWIFA in mortar, the primary environmental concern is if any harmful materials leach out during the initial curing process or throughout the life of the mortar. Toxicity characteristic of leaching procedure (TCLP) analysis of all CWIFA specimens found amounts of heavy metals below regulatory limits. Solidification of waste with cement and solidified waste has become a popular way of minimising the atmosphere's emissions. The amount of CWIFA generated is expected to increase nationally and globally. There is an immediate need for further evaluation of ash leachate investigations for proper disposal and usage of ash in construction materials.

Discovering Graphical Heuristics on Fire-Induced Spalling of Concrete Through Explainable Artificial Intelligence

Fire-induced spalling of concrete continues to be an intriguing and intricate research problem. A deep dive into the open literature highlights the alarming discrepancy and inconsistency of existing theories, as well as the complexity of predicting spalling. This brings new challenges to creating fire-safe concretes and primes an opportunity to explore modern methods of investigation to tackle the spalling phenomenon. Thus, this paper leverages the latest advancements in explainable Artificial Intelligence (XAI) to vet existing theories on fire-induced spalling and to discover solutions/heuristics to predict spalling of concrete mixtures. The developed heuristics are in the form of graphs and nomograms. The proposed solutions allow interested researchers and engineers to graphically identify the propensity of a given concrete mixture to spalling directly and with ease. For example, we report that concrete mixtures with a combination of moderate water/binder ratio (of about 0.3), low heating rate (less than 2.5°C/min), moderate rise in temperature (less than 500°C), and have moisture content (less than 3%) are expected to be less prone to spalling. Further, findings from this research showcase the potential for developing simple (i.e., one-shot) and graphical (coding-free and formula-free) XAI-based solutions and web applications to address decades-long problems in the area of concrete research.