Measurement and removal of asbestos in residential dwellings to be demolished-urban transformation experience in Izmir, Turkey

Asbestos has been used extensively in the construction industry for its superior insulation properties before its health hazards were discovered and its use eventually banned. It is likely that many residential buildings built before the 2000s in Turkey contain asbestos. Therefore, it is important to raise awareness of the potential danger of asbestos exposure during demolition work and to identify asbestos-containing materials and ensure their safe removal and disposal. This study is executed to determine the residential dwellings containing asbestos in Izmir, Turkey. The research included field studies to determine asbestos presence in the buildings that were damaged during the 2020 earthquake. Air measurements and bulk samples were taken from 50 buildings that would go through the demolition process. Eleven buildings were found to contain asbestos which corresponds to 22%. The detected asbestos type was 60% chrysotile (white asbestos). Results could be helpful for future demolition work, which are conducted in the same region that includes buildings with similar properties. Also, it is expected that the database created for this study could be useful in other studies in Turkey, where accurate statistical data related with asbestos measurements is essentially non-existent.

A comprehensive model for quantifying construction waste in high-rise buildings in India

The construction industry plays a vital role in the economic development of any country. Concurrently, the sector also generates enormous quantities of construction and demolition waste (CDW) that damages the ecology causing environmental pollution and deteriorating human health. Recently, various governments and other organizations realized the importance of implementing construction waste management (CWM) practices to attain sustainability in construction. The current decade can be called a pathway for achieving the 2030 agenda for sustainable development goals in which CWM plays an inevitable role. However, accurately quantifying construction waste is necessary to successfully implement any CDW management plan. A detailed literature review for the current research revealed that limited information on the magnitude of construction waste is available in India. Therefore, the current paper proposes a practically viable model to estimate the waste generation index (construction waste generated per total floor area) of high-rise residential buildings in India. The waste quantification is being done based on the project documents and expert interviews. The methodology is later validated through a high-rise building with G + 18 stories located in Kerala, India. The study indicated that a high-rise concrete framed structure generates 122.3 kg m-2 of waste during construction. It was also noted that, concrete, aggregates and blocks constitute 92% of the total waste generated in the project. The developed model can also be used as a cornerstone for establishing a construction waste database at the regional level.

Analysis of environmental performance indicators for concrete block manufacturing: embodied energy, CO2 emissions, and water consumption

Concrete block production significantly contributes to environmental degradation. A thorough understanding of its ecological implications is critical for sustainable development. This study investigates concrete block manufacturing's environmental impact by quantifying embodied energy, CO2 emissions, and water consumption via a comprehensive life cycle assessment. An extended life cycle assessment methodology is utilized to quantify the environmental indicators throughout the concrete block production lifecycle. Primary industry data and secondary research data ensure accuracy and reliability. Findings showed that concrete block manufacturing requires 2.5-4.1 times more embodied energy than equal clinker mass. Cement and aggregate production and transportation account for substantial energy needs. Limestone calcination during cement production causes significant CO2 emissions, 2.3-3.3 times higher than the minimum. Water consumption is concerning during curing and washing. Exploring alternative cementitious materials, optimized processes, and water recycling can reduce embodied energy by up to 75%, CO2 emissions by up to 67%, and water consumption by up to 80%. Concrete block manufacturing necessitates considerable energy and generates significant emissions. Implementing sustainable measures can minimize embodied energy, CO2 emissions, and water consumption, enabling environmentally responsible manufacturing. This research emphasizes adopting sustainability practices to mitigate environmental impact. Policymakers, industry professionals, and researchers can employ these insights to develop effective strategies promoting green manufacturing. The concrete block industry can contribute to a sustainable future through sustainable practices.

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.

Characterization of textile effluent treatment plant sludge and its industrial application in fired clay bricks with health risk assessment

The textile industry in Bangladesh faces environmental and health challenges due to the disposal of solid waste from Effluent Treatment Plants (ETPs). To address this issue, a study was conducted using soil from a brick industry near Dhaka, amending it with varying amounts of dry sludge to create clay bricks. The original soil had a loam texture and medium plasticity. The research found that adding 9 wt% of sludge resulted in Grade A commercial bricks with a compressive strength of 15.33 MPa and water absorption of 13.33 wt%, meeting BDS 208 standards. However, these sludge-incorporated bricks experienced more shrinkage during the burning process due to organic content, requiring additional soil to maintain conventional dimensions. Also, to assess the health hazards of these sludge-incorporated bricks, a leaching test was performed, revealing that no toxic heavy metals (Pb, Cd, Cr, Cu, Ni, and Zn) in the leachate exceeded the limits set by the United States Environmental Protection Agency (USEPA). The study indicates that textile ETP sludge can serve as a sustainable raw material for bricks, potentially reducing the environmental burden caused by textile sludge disposal by 28.75%. This innovative approach offers a promising solution to both environmental and health concerns associated with textile waste in Bangladesh's industrial sector.

Relationship between Ra-226 activity concentration in building materials and indoor radon concentration: An example of Russian high-rise residential buildings

The worldwide trend toward the construction of high-rise buildings with high energy efficiency highlights the role of building materials as a source of indoor radon in the modern urban environment. The aim of the study is to analyze the relationship between the Ra-226 activity concentration in building materials and indoor radon concentration using the example of multi-story buildings in Ekaterinburg. Measurements of the activity concentration of natural radionuclides in building materials were carried out using a new non-destructive method. A radon survey conducted early provided the data on indoor radon concentrations in the same apartments. The obtained Ra-226 activity concentrations in building materials in high-rise buildings were found to be relatively low, ranging from 9.1 to 51 Bq/kg. The typical radon entry rate by diffusion from building materials for modern Russian multi-story buildings can be accepted as equal to 0.5 Bq/(m3∙h) per 1 Bq/kg of Ra-226 activity concentration. Ra-226 in building materials has been shown to be a primary source of indoor radon in modern high-rise buildings, where this factor can cause indoor radon concentrations above the reference level of 100 Bq/m3 at low air exchange rates. The activity concentration of Ra-226 in building materials should be considered a separate parameter for regulation within the national radiation protection systems.

Deep learning-based models for environmental management: Recognizing construction, renovation, and demolition waste in-the-wild

The construction industry generates a substantial volume of solid waste, often destinated for landfills, causing significant environmental pollution. Waste recycling is decisive in managing waste yet challenging due to labor-intensive sorting processes and the diverse forms of waste. Deep learning (DL) models have made remarkable strides in automating domestic waste recognition and sorting. However, the application of DL models to recognize the waste derived from construction, renovation, and demolition (CRD) activities remains limited due to the context-specific studies conducted in previous research. This paper aims to realistically capture the complexity of waste streams in the CRD context. The study encompasses collecting and annotating CRD waste images in real-world, uncontrolled environments. It then evaluates the performance of state-of-the-art DL models for automatically recognizing CRD waste in-the-wild. Several pre-trained networks are utilized to perform effectual feature extraction and transfer learning during DL model training. The results demonstrated that DL models, whether integrated with larger or lightweight backbone networks can recognize the composition of CRD waste streams in-the-wild which is useful for automated waste sorting. The outcome of the study emphasized the applicability of DL models in recognizing and sorting solid waste across various industrial domains, thereby contributing to resource recovery and encouraging environmental management efforts.

Net-Zero Embodied Carbon in Buildings with Today's Available Technologies

Greenhouse gas emissions from building construction─i.e., the embodied carbon in buildings─are a significant and growing contributor to the climate crisis. However, our understanding of how to decarbonize building construction remains limited. This study shows that net-zero embodied carbon in buildings is achievable across Japan by 2050 using currently available technologies: decarbonized electricity supply, low-carbon steel, low-carbon concrete, increased timber structures, optimized design, and enhanced building lifespan. The largest emissions savings would come from increased use of timber structures, with annual savings of up to ∼35% by 2050, even in cases where timber replaces low-carbon steel and concrete. Moreover, we show that an expanded domestic timber supply, coupled with responsible reforestation, could improve forest carbon uptake by up to ∼60% compared to the business-as-usual scenario, without the need to increase forest area. This is achieved through a forest-city carbon cycle that transfers carbon stocks of mature trees to cities as building materials and rejuvenates forests through reforestation. Collectively, our analysis demonstrates that the decarbonization of building construction depends not on future technological innovation, but rather on how we design and use buildings with the options we already have.

Biodiversity burdens in Spanish conventional and low-impact single-family homes

Biodiversity loss caused by housing is not a well-defined sector of environmental impact. This research quantifies effects on biodiversity of an average Spanish Single-Family House (SFH) with 180 m2 of built surface. The current Spanish SFH stock GWP amounts to 1.16 Gt CO2eq in a 50-year life cycle, 40 % of which is embodied in the building materials and the 60 % are emissions due to the use of the building. This stock also impacts with 10.2 Gt 1,4-DCB the land, water and human health. SFHs also drive 6052 species extinct in a 50 year life cycle, and account for 3.03 M years of life lost due to premature death or lived with a disability. Divided by the 16 M people living in Spanish SFHs, each one lost 0.19 years of their lives (68.1 days) due to their home's impacts on human health. The article compares a reference conventional building against three low-impact cases, to understand how different building techniques and materials influence environmental outcomes that keep biodiversity loss the lowest possible. Scenarios include a standard brick and concrete house as Scenario 0 (SC0, Base), a timber Passivhaus as Scenario 1 (SC1), a straw-bale house with renewable energies as Scenario 2 (SC2), and an earth bioclimatic house as Scenario 3 (SC3). An initial Global Warming Potential (GWP) analysis was performed to relate previous building Life Cycle Assessment (LCA) studies with biodiversity metrics. Three main biodiversity metrics; ecotoxicity (as midpoint indicator), biodiversity loss and damage to human health (both as endpoint indicators) have been considered. Compared to SC0 with 1292 kgCO2-eq·m-2 (516 embodied) of GWP, we found that SC1 emitted -47.0 % of that, SC2-41.4 % and SC3-80.9 %. Concerning ecotoxicity, where SC0 has 11,399 kg 1,4 DCB, the results are -27.9 % in SC1, -19.2 % in SC2, and -45.6 % in SC3. Regarding biodiversity loss, where SC0 has 7.54 E-06 species.yr·m-2, the impacts are -30.9 % in SC1, -32.6 % in SC2, and -58.6 % in SC3. Human health damage in SC0 being 3.37 E-03 DALY, has been reduced in the timber home (SC1) is -44.2 %, of the Straw SFH (SC2) -39.2 %, and of the earth house (SC3) -67.1 %. This article shows that with current existing technological solutions GWP could be reduced in -80.9 %, ecotoxicity in -45.6 %, biodiversity loss in -58.6 % and human health in -67.1 %. Spanish Single-Family Houses built in timber, earth or straw-bale are real alternatives to current cement traditional building.

Utilization of discarded face masks in combination with recycled concrete aggregate and silica fume for sustainable civil construction projects

The coronavirus (COVID-19) pandemic has not only had a severe impact on global health but also poses a threat to the environment. This research aims to explore an innovative approach to address the issue of increased waste generated by the pandemic. Specifically, the study investigates the utilization of discarded face masks in combination with recycled concrete aggregate (RCA) and Silica Fume (SFM) in civil construction projects. The disposable face masks were processed by removing the ear loops and nose strips, and then cutting them into small fibers measuring 20 mm in length, 5 mm in width, and 0.46 mm in thickness, resulting in an aspect ratio of 24. Various proportions of SFM and RCA were incorporated into the concrete mix, with a focus on evaluating the compressive strength, split tensile strength, and durability of the resulting material. The findings indicate that the addition of SFM led to improvements in both compressive and split tensile strength, while no significant impact on durability was observed.

Co-treatment of steel slag and oil shale waste in cemented paste backfill: Evaluation of fresh properties, microstructure, and heavy metals immobilization

The environmentally sustainable treatment of steel slag (SS) and oil shale waste (OSW) is a significant concern in the field of industrial development. The mining industry also faces challenges related to the high costs and carbon emissions associated with ordinary Portland cement (OPC), leading to environmental pollution. To address these challenges, this study aimed to develop a cost-effective and environmentally friendly binder for cemented paste backfill (CPB) by utilizing SS and calcined oil shale waste (COSW) as primary precursors. Extensive investigations were conducted to evaluate the properties of the CPB sample with varying COSW content, including rheological properties, mechanical strength, and microstructure. The binder sample was comprehensively characterized using isothermal calorimetric analysis, X-ray diffraction (XRD), thermogravimetry (TG), and scanning electron microscopy (SEM). Based on systematic experimentation, an optimal blend ratio for the binder was determined, consisting of 60 wt% SS, 15 wt% COSW, 15 wt% phosphogypsum (PG), and 10 wt% OPC. The exceptional performance of the binder was attributed to the substantial formation of precipitated ettringite (AFt), resulting in a more compact structure and improved mechanical strength. Additionally, a sequential extraction test revealed that the heavy metals in the CPB sample were mainly present in the residual fraction, demonstrating the effective immobilization of heavy metals by the binder.

High-value utilization of modified magnesium slag solid waste and its application as a low-carbon cement admixture

A large amount of magnesium slag solid waste, insufficient comprehensive disposal capacity, high disposal costs, and uncertain environmental stability hinder the low-carbon, green, and sustainable development of magnesium and magnesium alloy smelting. Therefore, this study proposed a high-quality, large-scale, and industrialized disposal method for modified magnesium slag (MMS). Through relevant experimental tests and microscopic characterization methods (physical and chemical performance, hydration heat, resistivity, and microstructure tests), the physical and chemical properties, curing mechanism, and social benefits of MMS low-grade magnesium slag were investigated. The physical and chemical properties, curing mechanism, and social benefits of modified magnesium slag low-carbon Portland cement (MMSPC) produced by MMS as a cement admixture were elucidated. The results showed that (1) the physical and chemical properties of MMSPC met the requirements of the GB 175-2007 "General Portland Cement" standard. (2) A significant difference was observed in the early hydration heat release of fresh MMSPC slurry, confirming a hydration composite effect between MMS and clinker, which was also the key reaction mechanism of MMS replacing clinker to produce MMSPC. (3) The resistivity of MMSPC increased, decreased, and then increased with time, which was mainly controlled by the settling of the aggregate, the dissolution of the binder, and the hydration reaction of the system. However, the variation in resistivity with time and value was influenced by the mixing ratio of the system. (4) MMSPC could also offer certain environmental and economic benefits. Carbon emissions per ton of cement produced were reduced by 7.95%, and the total cost per ton of cement produced was reduced by more than 10%. This study provided a theoretical basis for the high-value disposal of MMS and the reduction of carbon emissions in the cement industry.

A comparative LCA of external wall assemblies in context of Iranian market: considering embodied and operational energy through BIM application

Building envelopes have a critical role in the sustainability of the construction sector. The goals of the current research are assessing the environmental impacts of typical exterior wall assemblies and presenting the best Iranian market option through taking account of both embodied and operational energy. Autodesk Green Building Studio (GBS) is used to determine the operating loads of each wall. Simapro, a life cycle assessment software, is applied for managing data on environmental impacts. The derived results demonstrate that human health is the most severe damage category for all the analyzed walls. Also, the end-of-life stage's environmental impact is insignificant compared to the production and use stages. Reducing carbon emissions has the highest priority, such that replacing 1 m2 of masonry brick wall (the worst option) with prefabricated extruded polystyrene (XPS) drywall (the best option) can result in saving 1257.85 kgCO2eq. The operational phase of the studied walls has a wide range of environmental impacts. Prefabricated Knauf drywall as well as prefabricated XPS drywall consumes less energy for the operating phase mainly due to providing sufficient quantity of isolations that leads to the better total environmental performance. In conclusion, it should be noted that the thermal performance of building materials should be given more attention.

Assessment of the effect of different pulping by-products on enhancing the reuse of rubber waste in producing of cement-mortar

This work deals with avoiding the pollution risks from paper pulping liquors and rubber wastes that result from routine disposal tools; moreover, finding an approach to minimize the drawback of incorporating the rubber waste in weakening the strength of building materials. In this respect, pulping black liquors (BLs) is assessed as a treating agent for rubber waste and substituting the water in cement mortar formulation. The assessment was achieved by testing the mechanical properties, water resistance (reduction in water absorption and dimensional change against water), and morphology. The results showed that all BLs from different pulping agents, used in mixtures with water, provided improvements in both strength and water resistance properties. Kraft black liquor is most effective in providing improvements in compressive strength and flexural strength, as well as resistance to water absorption and change in dimension after exposure to water for 24 h, where the improvements were 688.2 %, 494.3 %, 27 %, and 65.3 %, respectively. It is interesting to note that this investigated route provided improvements in the impact resistance property of mortar. This last property is essential for minimizing accidents on the highway.

Exploration on the occurrence state of fluorine in cement hydration products mixed with high fluorine alkali free liquid accelerator

If there was abundant fluorine in shotcrete, it might leach out and pollute the soil or migrate to corrode the reinforcement.Therefore, this research mainly investigated the basic properties of high-fluorine alkali free liquid accelerator (HF-AFA) and its occurrence forms in cement hydration products.The macro-test results showed that with the increase of HF-AFA dosage, it appeared excellent coagulation promoting property. However, when the HF-AFA dosage exceeded 7.0%, the 1d compressive strength of mortar was lower than 7.0 MPa. In addition, by measuring the early hydration heat of cement, C3A, C3S, C2S and C4AF pastes with and without HF-AFA, and combining XRD and SEM micro-analysis, the occurrence forms of fluorine in different clinker minerals were obtained.The final analysis results indicated that fluorine mainly existed in the form of CaF2, CaAlF5 and Ca2AlF7 crystals in C3A and C3S minerals, while only little CaF2 crystals appeared in C2S and C4AF minerals.

Study on energy use and carbon emission from manufacturing of OPC and blended cements in India

The demand for production of cements is ever increasing to meet the infrastructure development globally. The energy and emission factors available for cements in most of the life cycle assessment (LCA) databases may not exactly suit for all the geographical locations. The main challenge in Indian scenario is the absence of database for LCA study. This study attempts to develop the energy and emission factors for the manufacturing of cements in Indian context. In the present study, five different cement manufacturing plants located in north, south, east, west and central zones of India are considered to assess the energy dissipation and carbon dioxide emission involved during the production of ordinary Portland cement (OPC). Most of the data is collected from the field, so that the energy and emission factors determined will be suitable for the zonal study. The study is then extended to assess the energy consumption and carbon dioxide emission for three blended cements, viz. Portland Pozzolan cement (PPC), Portland slag cement (PSC) and composite cement (CC) with permissible known replacement levels of fly ash, granulated blast furnace slag and both fly ash and slag, respectively. The average energy use and carbon emission is found to be on higher side in India by 15.14% and 12.64%, respectively, compared to other countries in manufacturing of cements. An average energy consumption in manufacturing of PPC, PSC and CC is found to be respectively 24.5%, 35.3% and 43.13% less compared to that of OPC. The CO2 emission intensity for OPC is found to vary between 893 and 940 kg/tonne of cement from five different zones, and an average of respectively 24.8%, 40.97% and 47.18% lower CO2 emission was observed from PPC, PSC and CC compared to OPC. From the inventory results, CC has proven to be a more sustainable cement with low energy consumption and lower CO2 emission compared to other cements.

Cause specific mortality in an Italian pool of asbestos workers cohorts

BACKGROUND

Asbestos is a known human carcinogen and is causally associated with malignant mesothelioma, lung, larynx and ovarian cancers.

METHODS

Cancer risk was studied among a pool of formerly asbestos-exposed workers in Italy. Fifty-two Italian asbestos cohorts (asbestos-cement, rolling-stock, shipbuilding, and other) were pooled and their mortality follow-up was updated to 2018. Standardized mortality ratios (SMRs) were computed for major causes of death considering duration of exposure and time since first exposure (TSFE), using reference rates by region, age and calendar period.

RESULTS

The study included 63,502 subjects (57,156 men and 6346 women): 40% who were alive, 58% who died (cause known for 92%), and 2% lost to follow-up. Mortality was increased for all causes (SMR: men = 1.04, 95% confidence interval [CI] 1.03-1.05; women = 1.15, 95% CI 1.11-1.18), all malignancies (SMR: men = 1.21, 95% CI 1.18-1.23; women = 1.29, 95% CI 1.22-1.37), pleural and peritoneal malignancies (men: SMR = 10.46, 95% CI 9.86-11.09 and 4.29, 95% CI 3.66-5.00; women: SMR = 27.13, 95% CI 23.29-31.42 and 7.51, 95% CI 5.52-9.98), lung (SMR: men = 1.28, 95% CI 1.24-1.32; women = 1.26, 95% CI 1.02-1.53), and ovarian cancer (SMR = 1.42, 95% CI 1.08-1.84). Pleural cancer mortality increased during the first 40 years of TSFE (latency), reaching a plateau thereafter.

CONCLUSIONS

Analyses by time-dependent variables showed that the risk for pleural neoplasms increased with latency and no longer increases at long TSFE, consistent with with asbestos clearance from the lungs. Peritoneal neoplasm risk increased over all observation time.

Study of variation of indoor radon levels in houses and prediction of indoor concentrations using house characteristics and outdoor radon levels

The measurement of 222Rn concentrations in indoor and outdoor air was carried out in certain locations of Mandya city, Karnataka, using the Solid State Nuclear Track Detectors (SSNTD) technique. The annual mean values of 222Rn in indoor and outdoor are found to be 20.5 ± 1.4 and 9.0 ± 0.5 Bq m-3, respectively. The observed mean value of indoor radon concentration is found to be well within the world and the Indian average of 40 and 42 Bq m-3, respectively. Outdoor radon concentrations have been measured in the vicinity of houses where yearlong radon measurements carried out using the SSNTD technique. The seasonal variation in the outdoor radon was studied and the average concentrations during summer, rainy and winter are 9.1, 6.9 and 12.9 Bq m-3 respectively. Considering the possible factors such as house characteristics (Volume, Surface area of building material, Leakage area, etc.), indoor-outdoor temperature difference and outdoor radon concentration into account, the indoor radon levels were predicted using the existing model which is based on the mass balance equation. The results are systematically analysed and discussed. The predicted values are compared with the measured values.

Assessment of natural radioactivity levels and potential radiological risks of commonly used building materials in Uttara Kannada District, Karnataka, India

The main goal of this study is to evaluate the natural radioactivity and potential radiological risks of frequently used building materials in Uttara Kannada district. Using an High purity Germanium Detector (HPGe) detector-based gamma-ray spectrometer, the activity concentration of 226Ra, 232Th and 40K was determined. The activity concentration of 226Ra, 232Th and 40K in the construction materials vary from 13.78 ± 0.90 to 151.9 ± 1.85, 14.21 ± 0.80 to 207.72 ± 2.9 and 55.26 ± 1.20 to 1298.24 ± 25 Bq kg-1 with an average value of 40.57 ± 1.37,60.13 ± 1.70 and 425.38 ± 4.75 Bq kg-1 having a geometric mean of 33.07, 46.49 and 290.20 Bq kg-1, respectively. The mean annual effective dose equivalent was found to be 0.68 mSv y-1 and is less than the International Commission on Radiological Protection proposed acceptable limit of 1 mSv y-1. The estimated radiological hazard parameters show that these building materials are safe to use in the construction of homes and do not offer a substantial source of radiation hazard.

Enhancing road performance of lead-contaminated soil through biochar-cement solidification: An experimental study

The effectiveness of cement-based solidification for remediating heavy metal-contaminated soil diminishes at high levels of contamination. To overcome this limitation, the potential of a biochar-cement composite curing agent to enhance the properties of Pb 2+ contaminated soil was investigated in this study. The permeability, unconfined compressive strength (UCS), and leaching characteristics of the biochar-cement composite material were assessed under varying biochar contents. The results revealed that the addition of 1-5 wt% biochar in cement significantly improved the UCS of the solidified soil. However, excessive biochar contents had a detrimental effect on the strength of samples. Additionally, the incorporation of 3.0% biochar reduced the hydraulic conductivity and porosity to 7.75 × 10-9 cm/s and 43.12%, respectively. Moreover, the biochar-cement composite material exhibited remarkable efficiency in treating highly concentrated Pb2+ contaminated soil, with leaching concentration decreasing significantly with increasing biochar content, falling below the Chinese hazardous waste identification standard. Overall, the utilization of a biochar-cement composite curing agent in the solidification of heavy metal-contaminated soil could be considered a promising subgrade filler technique.

Unveiling patterns in human dominated landscapes through mapping the mass of US built structures

Built structures increasingly dominate the Earth's landscapes; their surging mass is currently overtaking global biomass. We here assess built structures in the conterminous US by quantifying the mass of 14 stock-building materials in eight building types and nine types of mobility infrastructures. Our high-resolution maps reveal that built structures have become 2.6 times heavier than all plant biomass across the country and that most inhabited areas are mass-dominated by buildings or infrastructure. We analyze determinants of the material intensity and show that densely built settlements have substantially lower per-capita material stocks, while highest intensities are found in sparsely populated regions due to ubiquitous infrastructures. Out-migration aggravates already high intensities in rural areas as people leave while built structures remain - highlighting that quantifying the distribution of built-up mass at high resolution is an essential contribution to understanding the biophysical basis of societies, and to inform strategies to design more resource-efficient settlements and a sustainable circular economy.

Stabilization/solidification of heavy metal-contaminated marl soil using a binary system of cement and fuel fly ash

The stabilization/solidification (S/S) method is one of the most effective remediation techniques for treating contaminated soils. Several stabilizers, mostly the cementitious materials, have been used for the S/S treatment. In this paper, the feasibility of utilizing fuel fly ash (FFA) as a partial replacement of ordinary Portland cement (OPC) for the S/S treatment of marl soil contaminated with heavy metals was investigated. Two industrial waste materials, namely steel and electroplating wastes, were used to synthetically contaminate the marl soil. The stabilizers comprising of OPC and FFA were mixed with the contaminated soil at different dosages ranging from 10 to 40%, by mass, and a total of 48 S/S-treated soil mixtures were prepared. A series of experiments, including density, porosity, permeability, unconfined compressive strength (UCS), and toxicity characteristics leaching procedure (TCLP), were carried out on the soil mixtures to evaluate the efficiency of the proposed S/S treatment. Test results showed that the incorporation of FFA at higher volumes reduced the density and increased the porosity and permeability of the treated mixtures. Although FFA addition resulted in reducing the UCS values by an average of 46%, and this reduction was more significant at higher FFA percentages, the UCS values of all mixtures were more than 0.35 MPa (350 kPa), which passed the minimum requirements set by USEPA. In addition, the metal immobilization ability of the proposed treatment was confirmed by the TCLP analysis. As compared to the negative effect of the contamination of the soil by the electroplating waste, the contamination of the soil by steel waste had a higher negative effect. The results of this study would contribute in selecting an environment-friendly treatment of the contaminated soils using industrial waste materials, such as FFA, as a partial replacement of OPC. Nevertheless, the present study is an initial attempt to explore the possibility of utilizing FFA as a partial replacement of OPC in S/S treatment of marl soil contaminated with heavy metals. It is recommended to conduct another study in future including analysis of the treated soil mixtures using XRD, SEM, and FTIR techniques to better understand the stabilization/solidification mechanism and its implications on the test results.

Gabion water barrier structures as a sustainable approach to water and land conservation

Gabions involve low construction technology and are flexible, economically viable, and environmentally friendly. They are now widely accepted as a standard construction material on a global scale. Gabion water barrier structures can be used for a variety of objectives, including flood control, land development, regulation of sediment transport, and catchment restoration. While intense water runoff can cause a large hole or submerge regions in solid water barrier constructions, gabion structures can sink down into the earth and protect the land from environmental and economic damage. The present study reviews the design/construction procedure of gabion water barrier structures and field/laboratory and numerical investigations for their performance in water and land conservation. Various applications of gabion water barrier structures, especially for economic/social impact and environmental degradation control, which qualify the gabion water barrier structures as a sustainable technique for water and land conservation, are reviewed. Future aspects and challenges ahead are also discussed.

Self-assembled silk fibroin cross-linked with genipin supplements microbial carbonate precipitation in building material

The process of microbially induced carbonate precipitation (MICP) is known to effectively improve engineering properties of building materials and so does silk fibroin (SF). Thus, in this study, an attempt was taken to see the improvement in sand, that is, basic building material coupled with MICP and SF. Urease producing Bacillus megaterium was utilized for MICP in Nutri-Calci medium. To improve the strength of SF itself in bacterial solution, it was cross-linked with genipin at the optimized concentration of 3.12 mg/mL. The Fourier transform infrared (FTIR) spectra confirmed the crosslinking of SF with genipin in bacterial solution. In order to understand how such cross-linking can improve engineering properties, sand moulds of 50 mm3 dimension were prepared that resulted in 35% and 55% more compressive strength than the one prepared with bacterial solution with SF and bacterial solution only, respectively with higher calcite content in former one. The FTIR, SEM, x-ray powder diffraction spectrometry and x-ray photoelectron spectroscopy analyses confirmed higher biomineral precipitation in bacterial solution coupled with genipin cross-linked SF. As the process of MICP is proven to replace cement partially from concrete without negatively influence mechanical properties, SF cross-linked with genipin can provide additional significance in developing low-carbon cement-based composites.

Spatial differentiation of carbon emissions reduction potential for construction and demolition waste recycling

Identifying the regional differences and drivers for carbon reduction of construction and demolition waste (C&DW) recycling is essential to combat climate change. This study aims to calculate the carbon reduction potential for C&DW recycling from 2006 to 2021 in China and investigates the spatial differences and driving factors of carbon reduction potential for C&DW waste by combining the Theil index, Gini coefficient, and geographic detector methods. The carbon reduction potential for C&DW recycling in China was "high in the east and low in the west" overall level, with an average annual growth rate of 6.27%. The overall differences in carbon reduction potential for C&DW recycling are decreasing, mainly due to intraregional differences and inter-provincial differences in Northeast China. The population size, urbanization rate, and technological effect are the key factors influencing carbon reduction potential for C&DW recycling. There are two types of interactions between influencing factor pairs: nonlinear enhancement and two-factor enhancement. This study's results can guide policymakers to devise relevant, regionally specific policies.

Automatic identification of illegal construction and demolition waste landfills: A computer vision approach

Dozens of landslide accidents are reported at construction and demolition waste (CDW) landfills worldwide every year. Those accidents could be avoided via timely inspection in which the identification of illegal CDW landfills at a large scale plays a critical role. Traditional field surveys are time-consuming, labor-intensive, which is not effective in large-scale detection of landfills. To address this issue, a methodology is proposed in this study for the automatic identification of CDW landfills in large-scale areas by utilizing semantic segmentation of remote sensing imagery. Deep learning is employed to achieve automatic identification and a case study is conducted to showcase the models. The results shown that: (1) The model proposed in this study can effectively identify CDW landfills, with an accuracy of 96.30 % and an IoU of 74.60 %. (2) DeepLabV3+ demonstrated superior performance over Pspnet and HRNet, though HRNet approached DeepLabV3+ in performance with appropriate optimizations. (3) Case study results indicate the potential existence of 52 CDW landfills in Shenzhen, includng 4 official landfills and 48 suspected illegal CDW landfills, mainly in Longhua, Guangming, and Baoan districts. The method proposed in this study provides an effective approache to identify large-scale illegal CDW landfills and has great significance for supervising CDW landfills.

Evaluation of potential radiological hazards of unfired construction materials containing fly ash in Vietnam

In this study, the specific activities of 226Ra, 232Th and 40K in the unfired construction materials (solid card bricks, 4-hole bricks, pavement bricks) containing fly ash and bottom ash from a coal-fired thermal power plant in Vietnam were measured using the low-level gamma-ray spectrometer with HPGe detector. Also, the 222Rn concentrations in these materials were analyzed using RAD7 radon monitor and then radon mass exhalation rate and emanation fraction of these materials were calculated. The potential radiological hazards for residents living in the model room made of these materials were evaluated. The average specific activity of 226Ra, 232Th and 40K were found as 67.7, 79.3 and 703.5 Bq kg-1, respectively. The total annual effective dose (due to external gamma exposure and internal radon exposure for resident living in the CEN model room made of the unfired brick samples) was found as 0.9 mSv y-1 which is lower than the worldwide average dose of 2.4 mSv y-1. Calculations from ResRad-Build code showed that the doses due to radon exposure account for from 62.3% (at the first year) to 98.8% (at the next 30 years) of the total gamma and radon dose. Under low air exchange to the outside environment, from the 6th year onwards, the total dose may exceed the average dose value from natural radiation exposure sources.

A comparative life cycle assessment on recycled concrete aggregates modified by accelerated carbonation treatment and traditional methods

Recycling of construction and demolition wastes contributes to achieve carbon summit and carbon neutrality early in the construction industry. Accelerated carbonation is a promising new technology for enhancing the properties of recycled concrete aggregates (RCAs) as well as mitigating global warming. This study performed a comparative life cycle assessment on RCAs modified by accelerated carbonation treatment and traditional methods. The effect of different treatment methods on environmental impacts of concrete was evaluated. The key contributors of environmental impacts for concrete incorporating carbonated RCAs were identified. Moreover, a sensitivity analysis on the transport distance of concrete incorporating carbonated RCAs was conducted. Results demonstrated that incorporating carbonated RCAs could significantly reduce the energy demand, environmental impacts and environmental cost compared with natural aggregate concrete. Accelerated carbonation treatment exhibited greater potential than the normal two-stage crushing and heating treatment in mitigating environmental burden, especially for the global warming potential. Cement production and transportation were the primary contributors to environmental impacts of concrete incorporating carbonated RCAs. Sensitivity analysis indicated incorporating carbonated RCAs as alternatives of natural aggregates contributes to lower the environmental impacts of concrete when the natural aggregates are far from urban areas while the recycling center is near the city.

Construction and demolition waste framework of circular economy: A mini review

As the demand for materials continues to increase and building lifespans shorten, the construction industry faces mounting pressure to reduce its material and environmental impacts. Mismanagement of construction and demolition waste (CDW) can have severe environmental consequences. To address this, material recovery and circular economy approaches offer significant potential for reducing construction waste through the sustainable use of resources. Existing circular economy and material recovery models that prioritize recycling and reuse efforts demonstrate a sustained commitment to supporting circular practices in the construction and demolition sector. The goal is to minimize waste production, which poses environmental challenges such as raw material shortages and sustainability concerns. Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement for recruiting relevant literature, this mini review aims to identify the obstacles to implementing circular economy practices in the construction industry, while exploring opportunities for material recovery and circularity. The ultimate aim is to facilitate a fair and smooth transition towards sustainable development, while addressing environmental, social and economic barriers. A more sustainable and circular approach to building construction and management can be attained by considering all the aspects of the CDW cycle, resulting in significant benefits for the environment and society as a whole.

High performance C-A-S-H seeds from fly ash-carbide slag for activating lithium slag towards a low carbon binder

In this work, one-step synthesis of high-performance C-A-S-H (calcium alumina silicate hydrate) seeds from low-calcium fly ash (FA) and carbide slag (CS) by 7 days of mechanochemical mixing was proposed and used to activate lithium slag (LS) cement. The results showed that the seeding effect of C-A-S-H seeds was increased with the increasing Ca/Si (i.e. from 1.0 to 1.5), i.e. the mortar compressive strength of 1 day and 28 days were increased by 67% and 29% with the addition of 1.0% C-A-S-H nano-seeds at Ca/Si = 1.5 in the presence of polycarboxylate superplasticizer (PCE), respectively. Moreover, the chloride resistance of lithium slag cement was improved significantly, i.e. the electric flux was decreased by more than 30% than that of plain lithium slag cement mortar. The performance difference of various C-A-S-H seeds is mainly attributed to their high proportion and polymerization degree, more stretch and three-dimensional foil-like morphology at high Ca/Si. This study provides guidance for obtaining low-cost and high-performance C-A-S-H seeds from wastes and the highly efficient utilization of LS as supplementary cementitious materials (SCMs) in the future.

Pore characteristics of sulfate-activated coal gasification slag cement paste backfill for mining

With the mass production of coal-based solid waste, coal mine filling can effectively consume it. The coal gasification slag is modified and prepared as coal mine filling material to meet the relevant technical requirements, which can realize the recycling of coal mine → coal chemical industry → coal mine. In this paper, in order to explore the evolution law of the mechanical properties and pore structure characteristics of the modified coal gasification slag-cement cemented paste backfill (MCGS-CPB) prepared by sodium sulfate excitation coal gasification slag, a combined macro-meso-micro testing method is used. MCGS-CPB with different sodium sulfate contents (1~5%) were prepared and tested for uniaxial compressive strength (UCS), mercury intrusion (MIP) and microscopic tests. The results show that sodium sulfate has a significant effect on the UCS and pore structure characteristics of MCGS-CPB. The mechanical properties and pore structure characteristics of MCGS-CPB were best when sodium sulfate was doped at 3%; the mechanical properties and pore structure characteristics of MCGS-CPB were deteriorated when the addition of sodium sulfate is higher than 3%. On the meso-scale, when sodium sulfate was doped with 3%, the more harmful pores of MCGS-CPB gradually changed into harmless, less harmful, and harmful pores, and the macroscopic mechanical properties were gradually improved; when the addition of sodium sulfate is higher than 3%, the harmless, less harmful, and harmful pores of MCGS-CPB gradually changed into more harmful pores, and the macroscopic mechanical properties were deteriorated. On a microscopic scale, sodium sulfate can cause MCGS-CPB to form hydration products with expansion properties. The presence of a reasonable amount of sodium sulfate in the pores of MCGS-CPB is beneficial to the development of mechanical properties. However, excessive presence will lead to the formation of expansion stress, gradual formation of micro-expansion cracks, and deteriorate the macroscopic mechanical properties. Hence, the volcanic ash activity of coal gasification slag excited by external addition of sodium sulfate should not exceed 3%. This study provides a reference value for application ratio of sodium sulfate-stimulated MCGS-CPB used in coal mine filling design.

Breaking the cycle of excessive conservatism: Evaluating the γ-radiation dose from building materials

Radionuclide content in building materials is regulated in most European countries by calculating the activity concentration index. The I-index does not account for the properties nor the application of the material but provides a conservative evaluation of the annual γ-radiation dose. Using a Monte Carlo toolkit, EGSnrc, this study calculated doses from building materials in less conservative set-ups by focusing on materials with a potential for recycling NORM residues, such as Portland cement, ceramics, gypsum, and mineral insulation. It was observed that proper consideration of building material geometry strongly affected the indoor dose rate. Regulating low-density materials and finishing materials such as gypsum and insulation under the same framework as high-density and high-bulk materials proved problematic because the doses differ by orders of magnitude. The current reference values for radionuclide concentrations used in calculating the I-index do not apply to most construction materials. For many types of building materials, higher radionuclide concentrations in the material could be allowed without contradicting the annual effective dose reference for the public. This illustrates the potential for boosting the use of NORM residues in various construction applications.

Utilization of solid mine waste in the building materials for 3D printing

3D printing technology is gradually considered to be a rapid development of a green revolution in the field of architecture. Recently, utilizing solid mine waste to replace natural sand not only greatly reduces the 3D printing costs, but also contributes to an environmental sustainability development. However, most solid waste inevitably has an impact on the inherent mechanical strength and printability of concrete materials. It is an urgent requirement to expand the alternative materials and improve the overall property of 3D concrete materials. This paper reported an innovative concrete material that replaced natural sand with fine limestone powders for 3D concrete printing applications. The experimental measurements were performed including microstructures characteristics, flowability, buildability, shrinkability, layer-interface properties, mechanical properties and interlayer bonding strength. Besides, an effective method was proposed to characterize the printable properties of concrete materials and then the reasonable limestone powder replacement ratio was determined. Based on the investigation results, appropriate substituting limestone powder (40%) can effectively improve the grading of the concrete, thus promoting its printability and buildability. Moreover, the microstructures of the 3D printing concrete materials after curing were denser and their mechanical property improved by approximately 45%. With the further increase of replacement ratio, the reduction in the flowability led to a decrease of the printability. A large number of fine particles increased the shrinkage of the curing process and some bubbles were stranded inside the materials due to its increase in the viscosity, thereby reducing the mechanical properties of the hardened material. The produced concrete for 3D printing can be treated as an eco-friendly building material that contributes to the rational development and resource utilization of solid water, thus promoting the sustainable development of construction field.

Leaching performance of concrete eco-blocks: Towards zero-waste in precast concrete plants

This work presents a case study of waste incorporation, where precast concrete block rejects were reincorporated into the production of new recycled concrete blocks which stands for a technically and environmentally viable alternative to natural aggregates. This study therefore evaluated the technical feasibility, first, and the leaching performance, after, of recycled vibro-compacted dry mixed concrete blocks using different percentages of substitution of recycled aggregates (RA) coming from precast concrete block rejects in order to identify those that presented a better technical performance. According to the results, concrete blocks with a 20% of RA incorporation presented an optimum physic-mechanical behaviour. The environmental evaluation based on leaching tests was carried out to identify the most conflictive elements legally regulated according to their pollutant release levels and investigate their different release mechanisms. The leaching study performed in concrete monoliths showed that in blocks with 20% of RA incorporation: Mo, Cr, and sulphate anions presented a higher mobility during the diffusion leaching tests; Sb and Cu presented an average mobility; Ba and Zn exhibited lower mobility levels and their corresponding release mechanisms for each of them. However, the limits for pollutant release in construction materials in a monolithic state were not surpassed by far.

Exploring mudbrick architecture and its re-use in Artaxata, Armenia, during the 1st millennium BC. A multidisciplinary study of earthen architecture in the Armenian Highlands

Mudbrick constructions are extremely common in ancient western Asia, including the 1st millennium structures of the southern Caucasus and Armenian highlands. However, in the Caucasus the geoarchaeological study of these materials to provide insight into building practices and social structure is a topic little researched, especially when focusing on the longue durée. Artashat/Artaxata (Ararat region, Armenia) was the capital of the Armenian Kingdom of the Artaxiads, founded in the eighties of the 2nd century BC, but even before this the site was occupied in the Chalcolithic period, (ca. 5200-3500 BC), Early Iron Age (ca. 1200-900 BC) and in the Urartian period (ca. 800-600 BC) as well. All the previous occupation phases showed communities that made extensive use of earthen constructions as determined during past and recent archaeological excavations. This multidisciplinary study seeks to examine mudbrick architecture as a proxy for environmental and social interactions during the 1st millennium BC combining geoarchaeology, archaeobotany and building archaeology. We analyzed changes and continuities in architectural form and practices, alongside reconstruction of technological and social processes, to identify issues of raw material procurement, attestation of re-use, and consistency of building practices. The results of the geoarchaeological analysis of the earthen building materials used in different parts of the ancient city point to a re-use of materials over time.

Applying thermal demagnetization to archaeological materials: A tool for detecting burnt clay and estimating its firing temperature

Burnt materials are very common in the archaeological record. Their identification and the reconstruction of their firing history are crucial for reliable archaeological interpretations. Commonly used methods are limited in their ability to identify and estimate heating temperatures below ~500⁰C and cannot reconstruct the orientation in which these materials were burnt. Stepwise thermal demagnetization is widely used in archaeomagnetism, but its use for identifying burnt materials and reconstructing paleotemperatures requires further experimental verification. Here we present an experimental test that has indicated that this method is useful for identifying the firing of mud bricks to 190⁰C or higher. Application of the method to oriented samples also enables reconstruction of the position in which they cooled down. Our algorithm for interpreting thermal demagnetization results was tested on 49 miniature sun-dried "mud bricks", 46 of which were heated to a range of temperatures between 100⁰C to 700⁰C under a controlled magnetic field and three "bricks" which were not heated and used as a control group. The results enabled distinguishing between unheated material and material heated to at least 190⁰C and accurately recovering the minimum heating temperature of the latter. Fourier-Transform Infrared Spectroscopy (FTIR) on the same materials demonstrated how the two methods complement each other. We implemented the thermal demagnetization method on burnt materials from an Iron Age structure at Tell es-Safi/Gath (central Israel), which led to a revision of the previously published understanding of this archaeological context. We demonstrated that the conflagration occurred within the structure, and not only in its vicinity as previously suggested. We also showed that a previously published hypothesis that bricks were fired in a kiln prior to construction is very unlikely. Finally, we conclude that the destruction of the structure occurred in a single event and not in stages over several decades.

Use of irradiated PET plastic waste for partially replacing cement in concrete?

Portland cement used in the manufacture of concrete is responsible for an estimated 5-8% of the global CO2 emissions. Recently published work (Schaefer et al., 2018) claims that γ-irradiated PET waste powder can be used as a partial replacement of cement in concrete for reducing its CO2 footprint. More specifically, exposure of PET to γ-irradiation at a dosage of 100 kGy alters its crystal structure and chemical composition, which in turn leads to a smaller reduction in concrete strength compared to non-irradiated PET waste. Hence, making it possible for irradiated PET waste to be used as a raw ingredient in the manufacture of concrete while at the same time diverting significant quantities of PET waste from landfills. The aim of this research was to independently assess and verify the above claims. For this purpose, the effect of different low irradiation dosages (0, 10 and 100 kGy) and different replacement levels (2.5 %, 5 % and 10 % by volume) of cement by PET waste on the consistency and mechanical strength of pastes and mortars was determined in a laboratory investigation. XRD, TGA and DSC were also used to study the effect of irradiation on the microstructure of raw PET waste and the microstructure of paste and mortar samples containing irradiated PET waste powder. Our results indicate that use of γ-irradiated PET waste (exposed to an irradiation dosage of up to 100 kGy) for partially replacing cement does not lead to a significant recovery of mechanical strength lost when non-irradiated PET waste is used.

Comparative environmental assessment of low and high CaO fly ash in mass concrete mixtures for enhanced sustainability: Impact of fly ash type and transportation

The effect of fly ash type on the sustainability of concrete mixtures has yet to be quantified. This study aims to assess the environmental impacts of low calcium oxide (CaO) and high CaO fly ash in mass concrete mixtures from Thailand. The study analyzed 27 concrete mixtures with varying percentages of fly ash as a cement replacement (0%, 25%, and 50%) for 30 MPa, 35 MPa, and 40 MPa compressive strengths at specified design ages of 28 and 56 days. Sources of fly ash have been located between 190 km and 600 km away from batching plants. The environmental impacts were assessed using SimaPro 9.3 software. The global warming potential of concrete is reduced by 22-30.6% and 44-51.4% when fly ash, regardless of type, is used at 25% and 50%, respectively, in comparison with pure cement concrete. High CaO fly ash has more environmental benefits than low CaO fly ash when utilized as a cement substitute. The reduction in environmental burden was most significant for the midpoint categories of mineral resource scarcity (10.2%), global warming potential (8.8%), and water consumption (8.2%) for the 40 MPa, 56-day design with 50% fly ash replacement. The longer design age (56 days) for fly ash concrete showed better environmental performance. However, long-distance transport significantly affects ionizing radiation and ecotoxicity indicators for terrestrial, marine, and freshwater environments. Furthermore, the results show that a high cement replacement level (50%) may not always have a reduced environmental impact on mass concrete when considering long-distance transportation. The critical distance calculated based on ecotoxicity indicators was shorter than those calculated using global warming potential. The results of this study can provide insights for developing policies to increase concrete sustainability using different types of fly ash.

Modeling construction and demolition waste quantities in Tanta City, Egypt: a synergistic approach of remote sensing, geographic information system, and hybrid fuzzy neural networks

A waste management strategy needs accurate data on the generation rates of construction and demolition waste (CDW). The objective of this study is to provide a robust methodology for predicting CDW generation in Tanta City, one of the largest and most civilized cities in Egypt, based on socioeconomic and waste generation statistics from 1965 to 2021. The main contribution of this research involves the fusion of remote sensing and geographic information systems to construct a geographical database, which is employed using machine learning for modeling and predicting the quantities of generated waste. The land use/land cover map is determined by integrating topographic maps and remotely sensed data to extract the built-up, vacant, and agricultural areas. The application of a self-organizing fuzzy neural network (SOFNN) based on an adaptive quantum particle swarm optimization algorithm and a hierarchical pruning scheme is introduced to predict the waste quantities. The performance of the proposed models is compared against that of the FNN with error backpropagation and the group method of data handling using five evaluation measures. The results of the proposed models are satisfactory, with mean absolute percentage error (MAPE), normalized root mean square error (NRMSE), determination coefficient, Kling-Gupta efficiency, and index of agreement ranging between 0.70 and 1.56%, 0.01 and 0.03, 0.99 and 1.00, 0.99, and 1.00. Compared to other models, the proposed models reduce the MAPE and NRMSE by more than 92.90% and 90.64% based on fivefold cross-validation. The research findings are beneficial for utilizing limited data in developing effective strategies for quantifying waste generation. The simulation outcomes can be applied to monitor the urban metabolism, measure carbon emissions from the generated waste, develop waste management facilities, and build a circular economy in the study area.

Study on application and environmental effect of phosphogypsum-fly ash-red mud composite cemented paste backfill

Phosphogypsum (PG) cementitious paste backfill (CPB) was prepared by using PG and fly ash (FA) as the main raw materials, red mud (RM) as the alkaline activator, Portland cement (OPC) as the binder, and silica fume (SF) as the additive, and its properties were investigated to achieve the objective of "treating harm with waste." The results showed that the addition of OPC facilitated the flowability of the slurry, while the addition of RM and SF had the opposite effect. The slurry presented ideal flowability when the water/binder ratio was 0.2 and the superplasticizer (SP) content was 0.7%. The mechanical properties and water resistance were improved significantly with increasing OPC, RM, and SF doping. The strength of the CPB material exceeded 22 MPa after curing at room temperature for 28 days, which met the mine filling requirements. Changes in the ion concentrations of the solution were first monitored during immersion. The dissolution rules of Ca2+ and SO42- at different immersion ages confirmed that RM promoted the continuous hydration of CPB, which was the key to improve water resistance. Microstructural analysis showed that the main hydration products were AFt and C-S-H, which played an important role in the strength development of the material. The leaching results demonstrated that the metal ion content satisfied the requirements of the III categories of Chinese environmental standards (GB/T 14848-2017), indicating that the technology is a reliable and environmentally friendly technology for PG, FA, and RM recovery that can simultaneously support safe mining.

Transforming tree topping waste into flooring: a study on the production and evaluation of oriented strand board finish using urban and garden residues

Oriented strand board (OSB) has become a popular building material for residential construction, but little research has been conducted on its use as a finish floor material. The study investigated the quality and performance of OSB as an alternative to traditional engineered wood products for finish floors. Four types of OSB finish floors using a mixture of garden and urban tree toppings were produced and evaluated, along with different types and levels of resin and mat moisture content. The finish floor panels were subjected to a battery of tests, including concentrated loading, indentation, falling ball impact resistance, abrasion resistance, and surface wettability. The findings showed that urea formaldehyde resin with garden tree toppings performed best in floor surface indentation, abrasion resistance, and falling ball indentation. The phenol formaldehyde resin with garden tree toppings, on the other hand, showed less moisture absorption and swelling during surface wetting tests and better resistance to force application in the concentrated loading test. Our qualitative comparison revealed that OSB finish floor production using 100% garden tree topping strands and 12% urea formaldehyde resin, along with 14% mat moisture content, produced the best results. The study provides valuable insights into the potential use of OSB as a sustainable and cost-effective finish floor material, using waste materials from urban and garden tree toppings.

Finite element simulation study on vertical bearing characteristics of single pile with ram-compacted bearing sphere

The pile with ram-compacted bearing sphere (PRBS)is a kind of special-shaped pile, the calculation formula of single pile bearing capacity stipulated in Chinese Standards JGJ/T 135-2018 is relatively simple, and the factors considered are not comprehensive enough. This article uses the finite element simulation software ABAQUS to simulate and calculate the compressive bearing characteristics of PRBS, and studies the changes in the vertical bearing characteristics of PRBS under different factors and working conditions (different pile lengths, pile diameters, and the diameters of ram-compacted bearing sphere (RBS)). The calculation results indicate that the PRBS still has a large axial force near the enlarged end of the pile bottom, and the RBS bears a large load. The vertical bearing capacity of the PRBS is mainly provided by the RBS, but the pile side friction still has a certain degree of influence on its bearing capacity. The maximum ratio of pile side frictional resistance to applied load can reach 18.41%. Compared with the ordinary pile, the bearing capacity of the PRBS is significantly improved. The ultimate bearing capacity of the PRBS with the RBS diameter of 1m is more than 5 times that of the ordinary pile under the same condition. Pile diameter has little influence on the bearing capacity of PRBS, while the change of RBS diameter has great influence on the bearing capacity of single pile. However, when the RBS diameter is too large, it is easy to cause the uplift of surrounding soil in the construction process and affect surrounding piles. Therefore, it is suggested that the optimal RBS diameter should be 800mm~1200mm. This study provides reference suggestions for the study of piles with ram-compacted bearing sphere.

Measurements of airborne asbestos fibres during refurbishing

Although the use of asbestos fibres in building materials has been prohibited in Norway since 1985, asbestos-containing materials (ACMs) are still found in many buildings. Lack of knowledge and awareness of these materials may lead to exposure during refurbishing. The aim of this study was to investigate the airborne fibre concentration and classify fibres found during the abatement of various ACMs. The release of fibres during short-term work tasks, such as drilling and sawing, was also investigated. Parallel air samples were collected during asbestos abetment of different building materials and analysed with scanning electron microscope (SEM) and phase-contrast microscope (PCM), respectively. Material samples were analysed with SEM. A real-time fibre monitor was used to measure asbestos during short-term work. The highest fibre concentrations were measured for samples collected during the removal of asbestos insulating boards (1.5-4.5 fibres/cm3 [f/cm3]), and the numbers were relatively similar for SEM and PCM. A large difference in asbestos concentrations was found between SEM and PCM when analysing floor materials, which were probably caused by a high number of gypsum fibres that the PCM operator counted. Thin fibres (<0.2 µm in width) were included in the SEM count and constituted up to 50% of the total fibre concentration for the asbestos cement materials. The presence of other inorganic and organic fibres on these samples probably led to similar results between SEM and PCM. Short-term work led to peak concentrations above 30 f/cm3.

Redistribution of radionuclides in wall material and its effects on the room dose rate

Here we investigate the annual effective dose rate obtained from gamma radiation emitted from radionuclides in construction materials in a model room with fixed dimensions. The dose rate is calculated on the whole room area at half the room height. We focus our analyses on a comparison of the annual effective dose rate between the room centre and the room average at half the room height and provide wall-wise quadratic index equations for both. We find that the annual effective dose rate based on the room average is larger than for the room centre due to increased annual effective dose rates for positions in the room closer to the walls. Furthermore, we evaluate the annual effective dose rate under a non-equal distribution of radionuclides in the three wall types (floor and ceiling, long walls, short walls). When considering the room average of the annual effective dose rate, our analysis indicates that it appears advantageous to use construction materials with a higher radionuclide activity concentration for floor and ceiling and the material with a lower radionuclide content for long and short walls, if there is a choice in the construction process.

Modelling of demolition waste generation: Application to Greek residential buildings

The construction sector in Europe is among the biggest waste generators, producing 370 million tonnes of construction and demolition waste (CDW) every year, which contain important secondary materials. Quantification of CDW is important from their circular management and environmental impact point of view. Thus, the overall objective of this study was to develop a modelling methodology for estimating demolition waste (DW) generation. The volumes (m3) of individual construction materials contained in 45 residential buildings in Greece were accurately estimated using computer-aided design (CAD) software and the materials were classified according to European List of Waste. These materials will become waste upon demolition, with a total estimated generation rate of 1590 kg m-2 of top view area and with concrete and bricks representing 74.5% of total. Linear regression models were developed to predict the total and individual amounts of 12 different building materials based on structural building characteristics. To test the accuracy of the models, the materials of two residential buildings were quantified and classified and the results were compared with the model predictions. Depending on the model used, the % differences between models' predictions and CAD estimates for total DW averaged 11.1% ± 7.4% for the first case study and 2.5% ± 1.5% for the second. The models can be used for accurate quantification of total and individual DW and their management within the framework of circular economy.

Advanced exergoenvironmental and thermo-sustainability evaluation of cement plant, splitting the environmental impact into endogenous and exogenous parts: a case study

The paper presents an advanced exergoenvironmental and thermo-sustainability analysis of a dry process, 5-million-ton capacity cement plant with real-time operational data. The analysis was based on component-wise modelling by separating the exergy destruction (ED) into endogenous, exogenous, avoidable and unavoidable parts for the two production lines, L1 and L2. The result shows an exergy efficiency ([Formula: see text]) of 55.58% for L1 and 58.22% for L2. Additionally, the overall exergoenvironmental factor (EEF) was calculated at 6.47% for (L1) and 5.89% for (L2), with the rotary kiln (RK) having the highest (EEF) of 53.7%. Conversely, the advanced exergy analysis showed that the plant's mainstream ED rates are endogenous and unavoidable. The component sustainability index (SI) for L1 and L2 ranged between [Formula: see text] and [Formula: see text], respectively. Similarly, the sustainability results show that the environmental destruction coefficient (EDC) and the environmental destruction index (EDI) were high in L1. Nonetheless, the study identified components with high potential for improvement, making system design and optimization suggestions possible.

Economic viability analysis of recycling waste plastic as aggregates in green sustainable concrete

Plastic waste management is one of the major global challenges at present. Recycling single used plastic waste as partial replacement of natural aggregates in concrete may reduce problems regarding mismanagement of plastic waste and unsustainable utilisation of natural resources as aggregates. This concept has been explored in many studies and positive results are obtained, but it has not been materialized at a large scale due to the uncertainty regarding economic viability. The present study therefore focuses on the economic aspects of using Polyethylene based fine aggregates and Polyethylene Terephthalate based coarse aggregates as partial replacement (10%, 20%, 30% and 40%) of natural fine and coarse aggregates separately and simultaneously, with special emphasis given on environmental and social cost. A material flow diagram using STAN is first developed to calculate plastic waste generation. An industrial survey has been conducted to estimate production cost of plastic aggregates, while social cost as WTP is determined through CVM method. The result shows that the total cost of concrete decreases with increase of replacement percentage and cost reduction varies between 0.65% and 7.58% compare to conventional concrete depending on the percentage and type of replacement without compromising strength. So, alongside being hugely beneficial to environment and society in terms of reduction of leachate and greenhouse gas generation, micro-plastic pollution, requirement of landfill area, mosquito borne diseases, erosion, sedimentation, land loss etc.; the concept of recycling plastic waste as partial replacement of natural aggregates in concrete has been proved to be economically viable and beneficial too.

Microstructure and mechanical behavior of cemented gold/tungsten mine tailings-crushed rock backfill: Effects of rock gradation and content

Without appropriate and responsible waste management in place, the cursory storage of tailings and waste rocks on the surface can cause devastating damage to the planet's ecosystems. To proactively manage or abolish the damage, some techniques such as mine backfill have been already used repeatedly in mines. Microstructure and strength behavior of cementitious tailings-crushed rock backfill (CTCRB) with gold/tungsten tailings and rock contents (e.g., 10%, 20%, 30%, 40%, and 50%) were conducted in this study by using both UCS (unconfined compressive strength) tests (e.g., peak strengths, stress-strain curves, failure modes) and SEM micro-graphs. Key conclusions were shown that: when gradation and content of crushed rock was considered as 1-3 mm and 50% respectively, the UCS value of gold tailings based backfills was 1.02 MPa. In contrast, the UCS value of tungsten mine tailings based backfills was 1.36 MPa when the amount of crushed rock within the filling matrix became 10%. Tungsten tailings based backfills were more sensitive to crushed rock gradation than gold tailings based backfills. CTCRB's stress-strain curvatures were up-concave in the step of pore compaction. With the increase in the content and gradation of crushed rock, tungsten tailings based backfills showed swelling and crushing in complete destruction. Tailings' particle size, crushed rock content and gradation utterly affected the failure modes of CTCRB. Ettringite/CSH gel was found to be the leading hydration materials in the backfill matrix. The micro-cracks within CTCRB specimens were unfavorably correlated with its UCS data. To conclude, this study's main outcomes could give a significant guide for CTCRB's industrial uses.