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1.
Molecules ; 26(4)2021 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-33672935

RESUMO

Neither the modified Bingham model nor the Herschel-Bulkley model can be used to characterize and calculate the performance of shear thickening of highly flowable mortar because of their incalculability of the rheological parameters. A new exponential rheological model was established to solve the characterization and calculation of shear thickening of the lubrication layer (highly flowable mortar) during the pumping of concrete in this paper. This new exponential rheological model has three rheological parameters, namely, yield stress, consistency coefficient, and consistency exponent. They can quantitatively describe the yield stress, differential viscosity, and shear thickening degree of highly flowable mortar. The calculating results of the rheological parameters of the newly established model for the mortars with different compositions showed that the consistency exponent of mortar decreased with the increase of its sand-binder ratio or the dosage of fly ash in the binder. This indicates that the shear thickening degree of mortar decreases. The consistency exponent of mortar initially decreases and subsequently increases with the increase in silica fume content or the dosage of the superplasticizer. It illustrates that the degree of the shear thickening of mortar initially decreased and subsequently increased. These varying patterns were confirmed by the rheological experiment of mortars.


Assuntos
Materiais de Construção/análise , Modelos Teóricos , Reologia , Resistência ao Cisalhamento , Dinâmica não Linear , Plastificantes/química , Rotação , Torque , Viscosidade
2.
Molecules ; 26(4)2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33672068

RESUMO

The evaluation and interpretation of the behavior of construction materials under fire conditions have been complicated. Over the last few years, artificial intelligence (AI) has emerged as a reliable method to tackle this engineering problem. This review summarizes existing studies that applied AI to predict the fire performance of different construction materials (e.g., concrete, steel, timber, and composites). The prediction of the flame retardancy of some structural components such as beams, columns, slabs, and connections by utilizing AI-based models is also discussed. The end of this review offers insights on the advantages, existing challenges, and recommendations for the development of AI techniques used to evaluate the fire performance of construction materials and their flame retardancy. This review offers a comprehensive overview to researchers in the fields of fire engineering and material science, and it encourages them to explore and consider the use of AI in future research projects.


Assuntos
Inteligência Artificial , Materiais de Construção/análise , Fogo/prevenção & controle , Retardadores de Chama/análise , Aprendizado de Máquina , Redes Neurais de Computação
3.
Carbohydr Polym ; 254: 117461, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33357920

RESUMO

In the work, the non-woven cellulose acetate (CA) nanofiber mats were prepared via electrospinning, and CA nanofiber were incorporated into the core layer of the high-pressure laminates (HPLs). When the concentration of CA was 16 wt%, SEM images demonstrated that the morphology of the CA nanofiber mat was the best, with an average diameter of 654±246 nm. When CA nanofiber mats were incorporated into the core layer of HPLs, the mechanical properties of the resulted HPLs composites were significantly improved. Specifically, the tensile strength and elongation at break of the nanofiber mats reinforced HPLs composites increased remarkably to 40.8 ±1.1 MPa and 27.9 ± 0.9 %, respectively, which were nearly 6 times and 4.4 times higher than those of the pure HPLs. Furthermore, the incorporation of the CA nanofiber mats also significantly improved the flame retardancy of the HPLs, which was revealed from the thermogravimetric analysis (TGA) results.


Assuntos
Celulose/análogos & derivados , Materiais de Construção/análise , Técnicas Eletroquímicas , Nanofibras/química , Celulose/química , Celulose/ultraestrutura , Retardadores de Chama/análise , Formaldeído/química , Humanos , Nanofibras/ultraestrutura , Pressão , Resistência à Tração
4.
Carbohydr Polym ; 254: 117478, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33357930

RESUMO

Waterborne polyurethanes (WBPUs) have been proposed as ecofriendly elastomers with several applications in coatings and adhesives. WBPU's physicochemical properties can be enhanced by the addition of cellulose nanocrystals (CNCs). The way CNCs are isolated has a strong effect on their properties and can determine their role as reinforcement. In this work, CNCs produced using ancestral endoglucanase (EnCNCs) were used as reinforcement for WBPU and compared with CNC produced by sulfuric acid hydrolysis (AcCNC). The enzymatic method produced highly thermostable and crystalline CNCs. The addition of small contents of EnCNCs improved the thermomechanical stability and mechanical properties of WBPUs, even better than commercial AcCNCs. Besides, WBPU reinforced by adding EnCNCs was studied as a coating for paper materials, increasing its abrasion resistance and as electrospun nanocomposite mats where EnCNCs helped maintaining the morphology of the fibers.


Assuntos
Celulase/química , Celulose/química , Química Verde , Nanopartículas/química , Poliuretanos/química , Adesivos/química , Celulase/genética , Celulase/metabolismo , Materiais de Construção/análise , Humanos , Hidrólise , Nanocompostos/química , Nanocompostos/ultraestrutura , Nanopartículas/ultraestrutura , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Ácidos Sulfúricos/química , Água/química
5.
PLoS One ; 15(12): e0243293, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33332375

RESUMO

The main cause of problematic soil failure under a certain load is due to low bearing capacity and excessive settlement. With a growing interest in employing shallow foundation to support heavy structures, it is important to study the soil improvement techniques. The technique of using geosynthetic reinforcement is commonly applied over the last few decades. This paper aims to determine the effect of using geogrid Tensar BX1500 on the bearing capacity and settlement of strip footing for different types of soils, namely Al-Hamedat, Ba'shiqah, and Al-Rashidia in Mosul, Iraq. The analysis of reinforced and unreinforced soil foundations was conducted numerically and analytically. A series of conditions were tested by varying the number (N) and the width (b) of the geogrid layers. The results showed that the geogrid could improve the footing's bearing capacity and reduce settlement. The soil of the Al-Rashidia site was sandy and indicated better improvement than the other two sites' soils (clayey soils). The optimum geogrid width (b) was five times the footing width (B), while no optimum geogrid number (N) was obtained. Finally, the numerical results of the ultimate bearing capacity were compared with the analytical results, and the comparison showed good agreement between both the analyses and the optimum range published in the literature. The significant findings reveal that the geogrid reinforcement may induce improvement to the soil foundation, however, not directly subject to the width and number of the geogrid alone. The varying soil properties and footing size also contribute to both BCR and SRR values supported by the improvement factor calculations. Hence, the output complemented the benefit of applying reinforced soil foundations effectively.


Assuntos
Materiais de Construção , Solo , Argila/química , Materiais de Construção/análise , Fenômenos Geológicos , Iraque , Areia/química , Solo/química
6.
Sci Data ; 7(1): 392, 2020 11 09.
Artigo em Inglês | MEDLINE | ID: mdl-33168822

RESUMO

We constructed a near-real-time daily CO2 emission dataset, the Carbon Monitor, to monitor the variations in CO2 emissions from fossil fuel combustion and cement production since January 1, 2019, at the national level, with near-global coverage on a daily basis and the potential to be frequently updated. Daily CO2 emissions are estimated from a diverse range of activity data, including the hourly to daily electrical power generation data of 31 countries, monthly production data and production indices of industry processes of 62 countries/regions, and daily mobility data and mobility indices for the ground transportation of 416 cities worldwide. Individual flight location data and monthly data were utilized for aviation and maritime transportation sector estimates. In addition, monthly fuel consumption data corrected for the daily air temperature of 206 countries were used to estimate the emissions from commercial and residential buildings. This Carbon Monitor dataset manifests the dynamic nature of CO2 emissions through daily, weekly and seasonal variations as influenced by workdays and holidays, as well as by the unfolding impacts of the COVID-19 pandemic. The Carbon Monitor near-real-time CO2 emission dataset shows a 8.8% decline in CO2 emissions globally from January 1st to June 30th in 2020 when compared with the same period in 2019 and detects a regrowth of CO2 emissions by late April, which is mainly attributed to the recovery of economic activities in China and a partial easing of lockdowns in other countries. This daily updated CO2 emission dataset could offer a range of opportunities for related scientific research and policy making.


Assuntos
Dióxido de Carbono/análise , Materiais de Construção/análise , Monitoramento Ambiental , Emissões de Veículos/análise , Infecções por Coronavirus , Pandemias , Pneumonia Viral
7.
PLoS One ; 15(8): e0237029, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32764793

RESUMO

Paleomagnetic analysis of archaeological materials is crucial for understanding the behavior of the geomagnetic field in the past. As it is often difficult to accurately date the acquisition of magnetic information recorded in archaeological materials, large age uncertainties and discrepancies are common in archaeomagnetic datasets, limiting the ability to use these data for geomagnetic modeling and archaeomagnetic dating. Here we present an accurately dated reconstruction of the intensity and direction of the field in Jerusalem in August, 586 BCE, the date of the city's destruction by fire by the Babylonian army, which marks the end of the Iron Age in the Levant. We analyzed 54 floor segments, of unprecedented construction quality, unearthed within a large monumental structure that had served as an elite or public building and collapsed during the conflagration. From the reconstructed paleomagnetic directions, we conclude that the tilted floor segments had originally been part of the floor of the second story of the building and cooled after they had collapsed. This firmly connects the time of the magnetic acquisition to the date of the destruction. The relatively high field intensity, corresponding to virtual axial dipole moment (VADM) of 148.9 ± 3.9 ZAm2, accompanied by a geocentric axial dipole (GAD) inclination and a positive declination of 8.3°, suggests instability of the field during the 6th century BCE and redefines the duration of the Levantine Iron Age Anomaly. The narrow dating of the geomagnetic reconstruction enabled us to constrain the age of other Iron Age finds and resolve a long archaeological and historical discussion regarding the role and dating of royal Judean stamped jar handles. This demonstrates how archaeomagnetic data derived from historically-dated destructions can serve as an anchor for archaeomagnetic dating and its particular potency for periods in which radiocarbon is not adequate for high resolution dating.


Assuntos
Arqueologia/métodos , Planeta Terra , Campos Magnéticos , Materiais de Construção/análise , Materiais de Construção/história , Fogo/história , Pisos e Cobertura de Pisos/história , História Antiga , Humanos , Israel , Colapso Estrutural/história , Fatores de Tempo , Guerra/história
8.
PLoS One ; 15(6): e0233307, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32492032

RESUMO

Radiocarbon dating is rarely applied in Classical and Post-Classical periods in the Eastern Mediterranean, as it is not considered precise enough to solve specific chronological questions, often causing the attribution of historic monuments to be based on circumstantial evidence. This research, applied in Jerusalem, presents a novel approach to solve this problem. Integrating fieldwork, stratigraphy, and microarchaeology analyses with intense radiocarbon dating of charred remains in building materials beneath Wilson's Arch, we absolutely dated monumental structures to very narrow windows of time-even to specific rulers. Wilson's Arch was initiated by Herod the Great and enlarged during the Roman Procurators, such as Pontius Pilatus, in a range of 70 years, rather than 700 years, as previously discussed by scholars. The theater-like structure is dated to the days of Emperor Hadrian and left unfinished before 132-136 AD. Through this approach, it is possible to solve archaeological riddles in intensely urban environments in the historical periods.


Assuntos
Arqueologia/métodos , Arquitetura de Instituições de Saúde/história , Datação Radiométrica/métodos , Arqueologia/estatística & dados numéricos , Teorema de Bayes , Indústria da Construção/história , Materiais de Construção/análise , Materiais de Construção/história , História Antiga , Humanos , Israel , Datação Radiométrica/estatística & dados numéricos
9.
J Vis Exp ; (160)2020 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-32568225

RESUMO

Construction and demolition waste (CDW), including valuable materials such as plastics, have a remarkable influence on the waste sector. In order for plastic materials to be re-utilized, they must be identified and separated according to their polymer composition. In this study, the identification of these materials was performed using near-infrared spectroscopy (NIR), which identified material based on their physical-chemical properties. Advantages of the NIR method are a low environmental impact and rapid measurement (within a few seconds) in the spectral range of 1600-2400 nm without special sample preparation. Limitations include its inability to analyze dark materials. The identified polymers were utilized as a component for wood-polymer composite (WPC) that consists of a polymer matrix, low cost fillers, and additives. The components were first compounded with an agglomeration apparatus, followed by production by extrusion. In the agglomeration process, the aim was to compound all materials to produce uniformly distributed and granulated materials as pellets. During the agglomeration process, the polymer (matrix) was melted and fillers and other additives were then mixed into the melted polymer, being ready for the extrusion process. In the extrusion method, heat and shear forces were applied to a material within the barrel of a conical counter-rotating twin-screw type extruder, which reduces the risk of burning the materials and lower shear mixing. The heated and sheared mixture was then conveyed through a die to give the product the desired shape. The above-described protocol proved the potential for re-utilization of CDW materials. Functional properties must be verified according to the standardized tests, such as flexural, tensile, and impact strength tests for the material.


Assuntos
Materiais de Construção/análise , Plásticos/química , Resíduos/análise , Madeira/química
10.
Chemosphere ; 253: 126896, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32402467

RESUMO

High concentrations of manganese (Mn2+) and ammonia nitrogen (NH4+-N) in electrolytic manganese residue (EMR) have seriously hindered the sustainable development of electrolytic manganese industry. In this study, an innovative basic burning raw material (BRM) was used to stabilize/solidify Mn2+ and NH4+-N in EMR. The characteristics of EMR and BRM, stabilize mechanism of NH4+-N and Mn2+, and leaching test were investigated. The concentrations of NH4+-N and Mn2+ were 12.8 mg/L and 0.1 mg/L, respectively, when the solid liquid ratio was 1.5:1, and the mass ratio of EMR and BRM was 100:10, at the temperature of 20 °C reacting for 12 h Mn2+ was mostly solidified as bustamite ((Mn,Ca)Si2O6), groutite (MnOOH) and ramsdellite (MnO2). NH4+-N was mostly recycled by (NH4)2SO4 and (NH4)3H(SO4)2. Leaching test results indicated that the concentrations of heavy metals were within the permitted level for the integrated wastewater discharge standard (GB8978-1996). Economic evaluation revealed that the cost of EMR treatment was $ 10.15/t by BRM. This study provided a new research idea for EMR harmless disposal.


Assuntos
Amônia/química , Materiais de Construção/análise , Eletrólitos/química , Compostos de Manganês/química , Nitrogênio/química , Reciclagem , Gerenciamento de Resíduos/métodos , China , Metais Pesados/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise
11.
Environ Monit Assess ; 192(5): 321, 2020 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-32358693

RESUMO

Environmental friendly building materials (BMs) get more attention due to their potential to reduce carbon and air pollutant emissions. However, recycled building materials (RBMs) have no required standard of volatile organic compounds (VOCs) emissions. This study was mainly about the assessment of benzene, toluene, ethylbenzene, and xylene (BTEX), as well as carbonyls emissions from recycled building materials, including gypsum board (GB), calcium silicate board (CSB), fiber cement board (FCB), class I built wall tile (WT), and waterproof gypsum board (WGB). The highest initial and final levels of BTEX were observed on CSB, followed by GB and FCB, and no detectable BTEX were observed on WT and WGB. Benzene was with the highest level among all identified BTEX. Emissions of carbonyls were observed on all materials. The highest initial and final levels of carbonyls were observed on GB, followed by FCB and CSB, while the lowest ones were detected on WT and WGB. The final (96-h) steady-state emissions of BTEX from GB and CSB were 9 and 37 times those from conventional pairs and 27 and 41 times those from low-VOC pairs. Similarly, the final steady-state emissions of carbonyls from GB and CSB were 4.8 and 1.3 times those from conventional pairs and 16 and 2.5 times those from low-VOC pairs. The requirement of evaluation standard for VOC emissions from RBMs is highly recommended to protect consumers. Graphical abstract.


Assuntos
Poluentes Atmosféricos , Materiais de Construção , Monitoramento Ambiental , Poluentes Atmosféricos/análise , Benzeno/análise , Derivados de Benzeno/análise , Materiais de Construção/análise , Reciclagem , Tolueno/análise , Xilenos/análise
12.
Toxicol Appl Pharmacol ; 400: 115041, 2020 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-32428593

RESUMO

Respiratory ailments have plagued occupational and public health communities exposed to World Trade Center (WTC) dust since the September 11, 2001 attack on the Twin Towers in Lower Manhattan. We proposed that these ailments were proposed to be induced by inhalation exposure to WTC particulate matter (WTCPM), that was released during the collapse of the buildings and its subsequent resuspension during cleanup. We investigated this hypothesis using both an in vitro and an in vivo mouse intranasal (IN) exposure models to identify the inflammatory potential of WTCPM with specific emphasis on respiratory and endothelial tissue responses. The in vitro exposure studies found WTCPM exposure to be positively correlated with cytotoxicity and increased NO2- production in both BEAS-2B pulmonary epithelial cells and THP-1 macrophage cells. The in vivo C57BL/6 mouse studies found significant increases in inflammatory markers including increases in polymorphonuclear neutrophil (PMN) influx into nasal and bronchoalveolar lavage fluids (NLF and BALF), as well as increased levels of total protein and cytokine/chemokines levels. Concurrently, NLF, BALF, and serum NO2- levels exhibited significant homeostatic temporal deviations as well as temporal myograohic aortic dysfunction in myography studies. Respiratory exposure to- and evidence -based retention of- WTCPM may have contributed to chronic systemic effects in exposed mice that r resembled to observed effects in WTCPM-exposed human populations. Collectively, these findings are reflective of WTCPM exposure and its effect(s) on respiratory and aortic tissues, highlighting potential dysfunctional pathways that may precipitate inflammatory events, while simultaneously altering homeostatic balances. The tight interplay between these balances, when chronically altered, may contribute to- or result in- chronically diseased pathological states.


Assuntos
Poluentes Atmosféricos/toxicidade , Materiais de Construção/toxicidade , Poeira/análise , Endotélio Vascular/efeitos dos fármacos , Exposição por Inalação/efeitos adversos , Pneumonia/induzido quimicamente , Poluentes Atmosféricos/análise , Animais , Aorta/efeitos dos fármacos , Aorta/fisiopatologia , Biomarcadores/sangue , Líquido da Lavagem Broncoalveolar/química , Líquido da Lavagem Broncoalveolar/citologia , Líquido da Lavagem Broncoalveolar/imunologia , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Materiais de Construção/análise , Endotélio Vascular/fisiopatologia , Humanos , Exposição por Inalação/análise , Pulmão/efeitos dos fármacos , Pulmão/imunologia , Camundongos Endogâmicos C57BL , Cavidade Nasal/efeitos dos fármacos , Cavidade Nasal/imunologia , Cidade de Nova Iorque , Ataques Terroristas de 11 de Setembro , Células THP-1
13.
Chemosphere ; 253: 126754, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32302914

RESUMO

This study sought to analyze the effect of curing temperature on mechanical strength and microstructure of a copper tailing-based geopolymer via scanning electron microscopy (SEM), HCl extraction, nuclear magnetic resonance (NMR), and X-ray diffraction (XRD). The distribution of gel formed in geopolymers tended to be uniform with increasing curing temperature from 25 to 80 °C. Moreover, the percentage of Si sites in C-S-H and N-A-S-H gels increased from 62.08% to 78.94% and more tetrahedral [AlO4] was incorporated into the tetrahedron [SiO4] backbone, leading to an increase of compressive strength from 10.2 to 39.6 MPa. When the curing temperature was increased to 120 °C, the percentage of Si sites in C-S-H and N-A-S-H gel decreased to 69.52%, and the compressive strength decreased to 27.5 MPa. Moderately elevated curing temperature promoted the dissolution of aluminosilicate while curing temperatures above 80 °C hindered it. Excessive curing temperature led to a decrease in the geopolymer alkaline medium.


Assuntos
Silicatos de Alumínio/química , Materiais de Construção/análise , Cobre/química , Resíduos Industriais/análise , Gerenciamento de Resíduos/métodos , Força Compressiva , Microscopia Eletrônica de Varredura , Mineração , Propriedades de Superfície , Temperatura , Difração de Raios X
14.
Artigo em Inglês | MEDLINE | ID: mdl-31991748

RESUMO

Ecofriendly wood-based materials are required by consumers at present. Decorative panels are part of a large group of wood-composite materials, and their environmental properties must not be neglected. More environmentally friendly decorative panels can be achieved by various methods. This paper describes a method of production from larch bark. Tree bark, as a byproduct of the wood industry, is one of the research topics that have gained interest in the last decade, especially for its applications in biobased lignocomposites, with regard to the shrinkage of wood resources. In the present work, the formaldehyde content of decorative boards based on larch bark (0.6 g/cm³) was analyzed when bonded with five different types of adhesive systems: urea-formaldehyde, polyvinyl acetate, the mixture of 70% urea-formaldehyde + 30% polyvinyl acetate, polyurethane, and tannin-based adhesive. A self-agglomerated board was also analyzed. The formaldehyde content of the larch-bark samples was determined with the perforator method (EN 120:2011), and findings showed that all tested samples reached the E1 classification (≤8 mg/100 oven dry). Moreover, 75% of the values of the corrected formaldehyde content were included in the super-E0 class (≤1.5 mg/100 oven dry). In the case of boards bonded with tannin-based adhesive, this natural polymer acted as a formaldehyde scavenger.


Assuntos
Adesivos/química , Materiais de Construção/análise , Formaldeído/análise , Resíduos Industriais/análise , Larix/química , Casca de Planta/química , Madeira/química
15.
Environ Sci Pollut Res Int ; 27(8): 8507-8525, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31907809

RESUMO

The extensive waste produced in construction and demolition activities affects the ecological environment, impeding green development in countries worldwide, including China. China has paid increasing attention to managing construction and demolition waste (CDW). However, most of the existing research only qualitatively studies the factors affecting the recycling of CDW and does not reveal the critical factors. Therefore, based on stakeholder theory and the grey-DEMATEL method, this paper aims to identify and quantitatively analyze the critical factors in CDW recycling from the perspective of China. This paper drew the following conclusions: (1) Stakeholders in China's CDW recycling mainly include the government, CDW production units, and CDW recycling units. (2) Public policy, government subsidies, media promotion, human resources, cost, environmental awareness, technological innovation, and supply chain management are the eight dimensions with 13 factors that constitute CDW recycling in China. (3) For the total relations between factors affecting the recycling of CDW in China, the most influential factor is specific legislation and regulations. The factor with the highest degree of prominence is environmental awareness. The factor with the largest net cause value is the rationality of disposal and landfill charges. The factor with the largest net effect value is experienced construction workers. (4) The critical factors in China's CDW recycling include specific legislation and regulations, mandatory degree of normative standards, environmental awareness, the supply of raw materials for CDW recycling units, and the sale of remanufactured products. Finally, this paper identifies the following management implications: (1) the government should prioritize the task of improving specific legislation and regulations, with a focus on a mandatory degree of normative standards. (2) CDW production units should put the task of improving environmental awareness high on their agenda, with a focus on the supply of raw materials for recycling units. (3) CDW recycling units should prioritize the issue of the sale of remanufactured products. This paper also provides a theoretical basis for revealing the critical factors of CDW recycling in other countries or regions.


Assuntos
Indústria da Construção , Materiais de Construção/análise , Reciclagem/métodos , Gerenciamento de Resíduos , China , Indústria da Construção/economia , Materiais de Construção/economia , Humanos , Resíduos Industriais , Gerenciamento de Resíduos/métodos
16.
Environ Sci Pollut Res Int ; 27(8): 8310-8322, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31900775

RESUMO

As a major participant of the construction industry, small contractors have been increasingly involved in green building construction projects in recent years. However, existing literature indicates that little research has been done to investigate the critical success factors for small contractors to conduct green building construction projects. As a result, this study aims to fill up the gap by identifying the most critical success factors of small contractors and comparing them against large contractors. To achieve these goals, a comprehensive literature review and pilot interviews with experienced industry experts were conducted first, followed by a questionnaire survey administered to 30 small contractors from the construction industry of Singapore. Non-parametric statistical tests were used to analyze the data. Results reported that "laborers with experience in conducting green building construction projects," "incentives/subsidies provided by government," "support of senior management," "return on investment," "commit to changing behavior," "effective communication between stakeholders on goals for sustainable construction," "early contractor involvement," "engaging experts with sound knowledge of green building construction," "cost control," and "competency of project manager" were the top ten critical success factors for small contractors to conduct green building construction projects. Additionally, the comparison results between small and large contractors revealed that eight factors were statistically different assessed by industry practitioners. These factors are "procurement process," "cost control," "commit to changing behavior," "educating clients on benefits in sustainable construction," "laborers with experience in conducting green building construction projects," "hefty levy and tax on unsustainable construction practices," and "public demand for green building construction" and "industrial culture." This study enriches the knowledge by exploring the critical success factors for small contractors to conduct green building construction projects. Furthermore, this study is informative to industry practitioners as well, especially to those small contractors who plan to conduct green building construction projects in the future.


Assuntos
Indústria da Construção , Materiais de Construção/análise , Humanos , Singapura , Gerenciamento de Resíduos
17.
Environ Pollut ; 256: 113393, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31733950

RESUMO

Radon is a natural radioactive gas present in the environment, which is considered as the second most important lung cancer cause worldwide. Currently, radon gas is under focus and was classified as contaminant of emerging concern, which is responsible for serious biological/health effects in human. In presented work we propose the numerical model and analysis method for radon diffusion rate measurements and radon transport parameters determination. The experimental setup for radon diffusion was built in a classical, two chamber configuration, in which the radon source and outlet reservoirs are separated by the sample being tested. The main difference with previously known systems is utilization of only one radon detector, what was achieved by a careful characterization of the Rn-222 source and development of a numerical model, which allows for exact determination of radon transport parameters by fitting simulated radon concentration profile in the outlet reservoir to experimental data. For verification of the developed system, several insulation materials commonly used in building industry and civil engineering, as well as, common building materials (gypsum, hardened cement paste, concrete) were tested for radon diffusion rate through these barriers. The results of radon transmittance, permeability and diffusion coefficients for investigated materials are in compliance with values known previously from the literature. The analysis method is fast and efficient, and requires measurement period varying from a dozen or so hours up to 2-3 days depending on material properties. The described method is entirely based on a numerical analysis of the proposed differential equation model using freely available SCILAB software and experimental data obtained during sample measurements.


Assuntos
Poluentes Radioativos do Ar/análise , Modelos Químicos , Radônio/análise , Poluição do Ar em Ambientes Fechados/análise , Materiais de Construção/análise , Difusão , Humanos , Permeabilidade , Poluentes Radioativos do Solo/análise
18.
Health Phys ; 118(1): 96-105, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31658165

RESUMO

The Ore Mountains (Erzgebirge) and Vogtland are low-mountain regions in the East German state of Saxony. Here, silver deposits were found in 1168. Mining began shortly after, continues at varying intensity to this day, and has left numerous galleries and shafts. Today, eight companies with about 250 miners carry out maintenance at more than 40 small and frequently changing underground construction sites throughout the year. Miners are protected against high radon exposure by radiation protection measures such as ventilations, stoppings made of wood, foil, and expanding foam, and staff rotations. However, some of them still show high annual exposure levels; for example, in 2015 up to 14.4 mSv measured by passive radon dosimeters. Reasons for this include the high radon potential in old mining and the natural density driven mine air current through the galleries. Mine air currents can change directions during the day depending on outdoor temperatures. This paper presents the experiences of the Saxon Radiation Protection Authority in monitoring miners in old mining. For this purpose, the paper looks at seven examples of miners' critical exposures based on measurement curves of radon activity concentration and derives respective radiation protection measures. These encompass, for example, to activate mine fans, erect stoppings, extend ventilation pipes, and change the locations of mine fans. Conclusions are drawn for the operative and strategic radiation protection in old mining.


Assuntos
Guias como Assunto , Mineração , Modelos Teóricos , Exposição Ocupacional/análise , Monitoramento de Radiação/normas , Proteção Radiológica/normas , Radônio/análise , Poluentes Ocupacionais do Ar/análise , Poluentes Radioativos do Ar/análise , Materiais de Construção/análise , Humanos , Monitoramento de Radiação/métodos , Proteção Radiológica/métodos , Poluentes Radioativos da Água/análise , Local de Trabalho
19.
Indoor Air ; 30(1): 40-48, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31544292

RESUMO

The ISO 16000 standard series provide guidelines for emission measurements of volatile organic compounds (VOCs) from building materials. However, polymer-based consumer products such as toys may also release harmful substances into indoor air. In such cases, the existing standard procedures are unsuitable for official control laboratories due to high costs for large emission testing chambers. This paper aims at developing and comparing alternative and more competitive methods for the emission testing of consumer products. The influence of the emission chamber size was investigated as smaller chambers are more suited to the common size of consumer products and may help to reduce the costs of testing. Comparison of the performance of a 203 L emission test chamber with two smaller chambers with the capacity of 24 L and 44 mL, respectively, was carried out by using a polyurethane reference material spiked with 14 VOCs during the course of 28 days. The area-specific emission rates obtained in the small chambers were always similar to those of the 203 L reference chamber after a few hours. This implies that smaller chambers can provide at least useful numbers on the extent of polymer-based consumer product emissions into indoor air, thereby supporting meaningful exposure assessments.


Assuntos
Poluição do Ar em Ambientes Fechados/análise , Materiais de Construção/análise , Monitoramento Ambiental , Polímeros/análise , Compostos Orgânicos Voláteis/análise
20.
Environ Geochem Health ; 42(2): 397-405, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31309375

RESUMO

Asphalt concrete is one of the most important building materials in the modern world, but the leaching potential of metals from this composite material to the environment is poorly understood. In this study, metals leaching from four hot-mix asphalt samples were analyzed: two fresh samples of low-traffic and high-traffic composition and their weathered equivalents collected from roads in the city of Edmonton, Alberta, Canada. A sequential extraction, based on the Community Bureau of Reference method, was applied to study the speciation and potential mobility of metals and metalloids in those samples. Major trace metals identified in all four samples were Mn, P, Ba, Sr, Zn, V, and Ni, with the highest metals concentrations generally found in weathered asphalt concrete. Of the major trace metals, P, Mn, Sr, and Zn were relatively mobile, having large portions of their total concentrations in the exchangeable/acid-soluble and reducible fractions. When considering the most mobile fraction (exchangeable/acid soluble) and using Canada as a model country, up to 180 t P, 440 t Mn, 50 t Ba, 36 t Sr, 11 t Zn, and 0.11-3.2 t of other metals and metalloids (including Cr, Ni, Cu, As, and Pb) could potentially leach from the top layer of Canada's total of paved public roads. To place these amounts into perspective, they were estimated to make up to 22‰ of Canada's annual release numbers into soil, water and air for these same metals and metalloids. However, they are concentrated in a small area around roads and highways, creating the potential for localized soil and groundwater contamination.


Assuntos
Hidrocarbonetos/química , Poluentes do Solo/análise , Oligoelementos/análise , Alberta , Cidades , Materiais de Construção/análise , Monitoramento Ambiental , Poluentes do Solo/química , Oligoelementos/química , Tempo (Meteorologia)
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