Environmental Exposure Conditions Research Articles

Single-parameter concrete carbonation model for varying environmental exposure conditions

Carbonation-induced reinforced steel concrete corrosion is a prominent concern related to engineering design and maintenance. The Durability Index (DI) approach was developed in South Africa to address this concern and enhance the durability performance of reinforced concrete structures. This approach relies on durability index tests, which are associated with transport mechanisms linked to specific deterioration processes. The carbonation of concrete is primarily influenced by the microstructure and transport characteristics of the concrete. Environmental exposure conditions also influence the rate of carbonation. The focus of the research reported here was to develop a carbonation model that could predict the rate of carbonation of concrete exposed to, or sheltered from, rain, with the permeability coefficient (k) from the Oxygen Permeability Index (OPI) test (DI test) as the key unifying variable. The model development was based on natural carbonation data and the drying profiles (experimentally measured) of 48 different concretes. Concrete microstructure was varied by varying the water-to-cement ratio, curing conditions, and by using SCMs. The resulting carbonation model was able to predict the rate of carbonation of concrete, allowing for different exposure conditions. A unique feature of this model is its use of a single material property, the 'k' value, to effectively address both CO2 diffusion and the drying process within concrete. The model displayed sensitivity towards the influence of variation in CO2 concentration, concrete microstructure, and the environmental exposure conditions, making this a simplified, effective and practical concrete carbonation prediction model.

Indoor environmental quality assessment in passively ventilated classrooms in Germany and estimation of ventilation energy losses

In this field study we present an approach for the comprehensive and room-specific assessment of parameters with the overall aim to realize energy-efficient provision of hygienically harmless and thermally comfortable indoor environmental quality in naturally ventilated non-residential buildings. The approach is based on (i) conformity assessment of room design parameters, (ii) empirical determination of theoretically expected occupant-specific supply air flow rates and corresponding air exchange rates, (iii) experimental determination of real occupant-specific supply air flow rates and corresponding air exchange rates, (iv) measurement of indoor environmental exposure conditions of T, RH, cCO2, cPM2.5 and cTVOC, and (v) determination of real energy demands for the prevailing ventilation scheme. Underlying assessment criteria comprise the indoor environmental parameters of category II of EN 16798-1: Temperature T = 20 °C–24 °C, and relative humidity RH = 25 %–60 % as well as the guide values of the German Federal Environment Agency for cCO2cPM2.5 and cTVOC of 1000 ppm, 15 μg m−3, and 1 mg m−3, respectively.Investigation objects are six naturally ventilated classrooms of a German secondary school. Major factors influencing indoor environmental quality in these classrooms are the specific room volume per occupant and the window opening area. It is concluded that the rigorous implementation of ventilation recommendations laid down by the German Federal Environment Agency is ineffective with respect to anticipated indoor environmental parameters and inefficient with respect to ventilation energy losses on the order of about 10 kWh m−2 a−1 to 30 kWh m−2 a−1.

Nanoscale Evaluation of the Degradation Stability of Black Phosphorus Nanosheets Functionalized with PEG and Glutathione-Stabilized Doxorubicin Drug-Loaded Gold Nanoparticles in Real Functionalized System.

Two-dimensional black phosphorus (2D BP) has attracted significant research interest in the field of biomedical applications due to its unique characteristics, including high biocompatibility, impressive drug-loading efficiency, phototherapeutic ability, and minimal side effects. However, its puckered honeycomb lattice structure with lone-pair electrons of BP leads to higher sensitivity and chemical reactivity towards H2O and O2 molecules, resulting in the degradation of the structure with physical and chemical changes. In our study, we synthesize polyethylene glycol (PEG) and glutathione-stabilized doxorubicin drug-assembled Au nanoparticle (Au-GSH-DOX)-functionalized BP nanosheets (BP-PEG@Au-GSH-DOX) with improved degradation stability, biocompatibility, and tumor-targeting ability. Transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy indicate the nanoscale degradation behavior of synthesized nanoconjugates in three different environmental exposure conditions, and the results demonstrate the remarkable nanoscale stability of BP-PEG@Au-GSH-DOX against the degradation of BP, which provides significant interest in employing 2D BP-based nanotherapeutic agents for tumor-targeted cancer phototherapy.

Environmental Durability of Bio-Based and Synthetic Thermoplastic Composites in Large-Format Additive Manufacturing.

This research investigates the durability of large-format 3D-printed thermoplastic composite material systems under environmental exposure conditions of moisture and freeze-thaw. Durability was evaluated for two bio-based composite material systems, namely wood-fiber-reinforced semi-crystalline polylactic acid (WF/PLA) and wood-fiber-reinforced amorphous polylactic acid (WF/aPLA), and one conventionally used synthetic material system, namely short-carbon-fiber-reinforced acrylonitrile butadiene styrene (CF/ABS). The moisture absorption, coefficient of moisture expansion, and reduction of relevant mechanical properties-flexural strength and flexural modulus-after accelerated exposure were experimentally characterized. The results showed that the large-format 3D-printed parts made from bio-based thermoplastic polymer composites, compared to conventional polymer composites, were more susceptible to moisture and freeze-thaw exposure, with higher moisture absorption and greater reductions in mechanical properties.

Infrastructure, durability and sustainability in one concept

In this paper, the increase of the concrete structure durability is investigated through the implementation of restoration techniques aimed at achieving this goal through the use of specific advanced systems.Over time, concrete infrastructures are often subjected to the action of dynamic loads of variable amplitude that can establish different stress configurations. To this scope, a special fibre-reinforced cementitious mortar has been developed. This product has been subjected to small and large-scale dynamic bending tests and it has shown high fatigue properties.Concrete infrastructures can also be affected by different degradation phenomena that can occur depending on environmental exposure conditions. The most frequent phenomena certainly include carbonation and chloride attack. In this regard, this article shares Mapei’s experience with the use of elastic cementitious mortar, emphasising the high level of protection offered both in terms of protection against carbonation and against the ingress of chlorides.To this scope, numerous laboratory tests performed on these types of membranes are shared, as well as the tests performed on samples taken from existing structures, 18 years after application, for an in-depth evaluation of the durability increase over time.Finally, a small focus on a new range of Mapei products is carried out. The Mapei Zero product range has been the object of an important research and development work to reduce the carbon footprint of these materials underlining an increasing attention to environmental sustainability.

Microstructural and strength variations in natural sands exposed to diverse environmental conditions

Climatic variation affects the physicochemical properties of geomaterials and its impact on the mechanical performance of infrastructure depends on the nature and origin of the material. The long-term behavior of sand, like any other construction material, can only be fully understood by evaluating its engineering properties under extreme climatic conditions such as repeated cycles of freezing-thawing (FT), wetting-drying (WD), and heating-cooling (HC). In this study, sand samples of different origin, including beach sand and dune sand (relatively aged sands), and quarry dust (relatively young grains) were subjected to 20 independent cycles of FT, WD, and HC. Scanning electron microscopy, x-ray diffraction, and x-ray fluorescence tests were performed for microstructural, surface texture, and chemical composition of the sand samples. Moreover, direct shear test results present the engineering properties such as peak shear strength, strain at failure, and friction angle of each sand sample at the end of various cycles. It is concluded that the findings of this study may provide an improved understanding of how natural sands of different origins respond to various environmental exposure conditions.

Chloride penetration in reinforced slag-based concrete beams under combined effects of loads and drying–wetting cycles

The use of concrete incorporating slag is necessary due to global environmental concerns, but the decrease in concrete durability caused by environments rich in chloride ions requires more advanced concrete mix designs, especially in coastal areas. The aim of this study was thus to assess the influence of slag addition on the transport of chloride ions in reinforced concrete (RC) beams under sustained bending moments, considering two conditions of environmental chlorine exposure: drying–wetting cycles and soaking. The results showed that the chloride diffusion coefficient (CDC) increased in tension zones and decreased in compression zones when the sustained bending load in the concrete beam was increased. However, it was also found that the addition of slag can significantly reduce the chloride diffusion depth and CDC for both environmental conditions, with a more significant effect under drying–wetting cycles. The chloride concentration on the surface of slag concrete in the compression zone was greater than that in the tension zone and greater than that in both the tension and compression zones of the ordinary concrete. A prediction model was established for describing the chloride penetration characteristics of concrete beams subjected to sustained bending moment. The proposed model is a reasonable approach for predicting chloride distribution in RC beams with slag addition subjected to bending moments.

Cure cycle optimisation of structural epoxies used in composite civil infrastructure through the use of TTT diagrams

Adhesive bonding is becoming increasingly common in civil infrastructure construction due to the increased use of advanced composites. Due to the large scale of the structures and their application in outdoor settings, the conditions during adhesive curing are substantially different from those in other industries. However, little information exists on curing conditions of commonly used adhesives in civil infrastructure applications making the design of such adhesive-bonded joints difficult. This paper presents a study investigating different phase transitions involved in the curing process of Sikadur® −30, a commonly used adhesive in civil infrastructure applications. A time–temperature-transformation cure diagram was developed for this epoxy system. Oscillatory rheological data were used to determine the gel times. Differential scanning calorimetry tests were used to estimate the time taken for vitrification. Unreacted system and fully reacted system glass transition temperatures were determined to be −48 °C and 70 °C, respectively. Reaction kinetic simulations were carried out for the Sikadur® −30 epoxy system based on the obtained experimental data. The numerical predictions were validated against a comprehensive experimental program. Predictions were shown to be in excellent agreement with the experimental results. This research provides the pathway for structural composite designers to determine important information such as pot life and curing times under different environmental exposure conditions for better design of advanced composite bonded joints.

Effects of soundscape on Chinese children's social interaction measured by self-reported behavioral expectations

Soundscape research has achieved some progress in enhancing the quality of urban space to support mixed uses. However, there is little evidence of promoting individual development and social relationship. Accordingly, the present study investigated the effects of soundscape on children's social interaction measured by self-reported behavioral expectations (Interaction, Nonparticipation, Avoiding) in the laboratory settings. Environmental exposure conditions were eight soundscape stimuli and one control condition (No sound), presented alongside visual recordings from a schoolyard or an urban park. Results showed that the soundscapes had significant effects on children's behavioral expectations and these effects did not differ significantly between the schoolyard and the urban park. Compared to No sound, Children's sounds and Nature sounds predisposed children to interactions, while Animal sounds and Classical music elevated children's intention to stay alone in the environment. Comparisons to the control group aside, correspondence analyses suggested the relationships between various soundscapes and behavioral expectations categories: Human movement sounds, Children's sounds, Adults' sounds, and Nature sounds were associated with Interaction; Animal sounds and Classical music were associated with Nonparticipation; Motorized transport sounds and Electro-mechanical sounds were associated with Avoiding. These findings on children's behavioral expectations indicate that the soundscape can influence children's decisions about contact and interaction with others in the environment, thereby fostering or impeding children from establishing and maintaining social relationships.

A Review on Analysis of Damage Diagnosis and the Vibration Characteristics of Steel Bridge Structures

Cracks or crevasses in girder steel bridges caused by moist environmental issues such as corrosion have the possibility of causing structural destruction, resulting in the loss of unanticipated events, assets, and human life. This obliteration can be overlooked if cracks are resolved early. The cracks in the bridge girder alter its strength and vibration characteristics. The current study examines various studies in the field of crack detection/damage detection that have been conducted using various numerical and experimental techniques. Analysis of finite elements (FEA) can be highly useful in protecting a structure from damage and cracks. The review deals with the investigation of damage commencing from environmental exposure conditions which can be studied via various numerical and experimental investigations by means of simulation techniques. By dint of these software-aided techniques, the research can be carried out in a simple and effortless manner. FEA enables engineers to conduct the simulation of a designed model rather than creating a physical model for testing. The current study looks at the effect of damage initiation and propagation using software-operated techniques The Applications of finite element methodology, which requires a software package for dynamic simulations, are presented and highlighted in terms of innovation and future research in studying crack attributes of natural and mode shapes.

Dynamic analysis of sheep Brucellosis model with environmental infection pathways.

We develop a mathematical model for the transmission of brucellosis in sheep taking into account external inputs, immunity, stage structure and other factors. We find the the basic reproduction number $ R_0 $ in terms of the model parameters, and prove the global stability of the disease-free equilibrium. Then, the existence and global stability of the endemic equilibrium is proven. Finally, sheep data from Yulin, China are employed to fit the model parameters for three different environmental infection exposure conditions. The variability between different models in terms of control measures are analyzed numerically. Results show that the model is sensitive to the control parameters for different environmental infection exposure functions. This means that in practical modeling, the selection of environmental infection exposure functions needs to be properly considered.

RILEM TC 277-LHS report: lime-based mortars for restoration–a review on long-term durability aspects and experience from practice

For conservation interventions of historic masonry generally lime-based mortars such as pure air lime mortars, lime-pozzolan mortars, natural hydraulic lime mortars and ternary mortars (lime-pozzolan-cement) are used. The main reason is that their hygric and mechanical (strength and ductility) performance are easy to adapt to most existing historic masonry (compatibility requirements). Although the basic appropriateness of lime-based mortars for restoration is undisputed, there are also some limitations in the application of these mortars. In this report a review is given of the theoretical backgrounds and further of laboratory research developments in the field of lime-based binders and mortars over the past decades. Furthermore, practical experiences in positive and negative sense (damage cases) are elaborated. Drawbacks and points of attention are being dealt with, which are essential for a durable application of lime-based mortars for the conservation of historic masonry. In general, it is concluded that points of attention should be addressed through a thorough evaluation of their potential and through testing of their suitability. For these mortars, even more than for modern cement-based mortars, specifically, environmental exposure conditions and application conditions should be considered.

Association between smoking and hypertension under different PM2.5 and green space exposure: A nationwide cross-sectional study.

Smoking has been widely reported to have a significant relationship with hypertension, but the past description of this relationship has not been uniform. In addition, there has been a lack of research to discuss the impact of environmental exposure on the relationship between smoking and hypertension. Therefore, this study estimates the association between smoking and hypertension in middle aged and elderly people in China under different PM2.5 (fine particulate matter) concentrations and the green space exposure conditions. Individual sample data from the China Health and Retirement Longitudinal Study in 2018 and the long-term average exposure concentration of fine particles and green space exposure for all participants were used with a multilevel binary logistic mixed effects model. Adjustments were made for sociodemographic characteristics and other health behaviors including drinking, physical activity, and social activity. The normalized difference vegetation index (NDVI) and PM2.5 concentration stratification were assigned with the median of the population exposure concentration as the dividing line, and the dual environmental factor stratification was assigned in combination with the two types of environmental exposure. The analysis was also stratified using age groups. A total of 10,600 participants over the age of 45 were included in the study. The effects of smoking on hypertension were diverse under different environmental exposure conditions. There was a significant relationship between smoking behavior and hypertension in the Low-NDVI group, and the effect value of this relationship was significantly different from that in the High-NDVI group. Furthermore, for respondents exposed to low green spaces and high PM2.5 environments at the same time (Low-NDVI/High-PM2.5 group), their smoking behavior may lead to an increase in the risk of hypertension. In addition, the risk of hypertension caused by smoking in the middle-aged (45-64) was significant under low green space exposure, but the effect difference between the different age groups was not significant. The relationship between smoking and hypertension was different under different environmental exposure conditions. Exposure to low green spaces may strengthen the association between smoking and hypertension risk. When participants were exposed to both low green spaces and high PM2.5 concentrations, the risk of hypertension caused by smoking was significantly higher than that of those who were exposed to high green spaces and low PM2.5 concentrations.

In-vitro cell culture model to determine toxic effects of soil Arsenic due to direct dermal exposure

Arsenic (As) is one of the most toxic environmental pollutants, classified as a Class I carcinogen. Anthropogenic activities have led to an increase in As contamination of soils. Using animal models to study the health impacts of As is time and cost-prohibitive, hence attempts have been made to develop in-vitro cell culture models. However, most studies so far have not represented realistic environmental exposure conditions. We exposed Human Immortalized Keratinocyte (HaCaT) and Primary Human Dermal Fibroblasts (HDFa) cells to the water-soluble fraction of arsenic extracted from As spiked Immokalee soil to study the effect of soil As on skin cells. The impact of As was determined through cell viability, cell migration, and quantitative assessment of the expression of cadherins, CD44, and Zeb1 using Western Blotting and In-cell Western. Our data indicated that HaCaT cells were more susceptible to As-induced cellular transformation than HDFa cells. At concentrations above 225 mg/kg of soil As, cellular responses were impacted, and changes in the expression of proteins were observed in HaCaT cells. The work presented here is a methodical approach to studying the impacts of toxic elements such as As through innovative cellular models using realistic environmental conditions, that can be readily adapted for different exposure pathways. • Human skin cells exposed to the water-soluble soil As showed decreased viability. • Uptake of soil As by keratinocytes was higher than that of fibroblasts. • Soil As impacted cell-to-cell adhesion and migration in skin cells. • Soil As induced epithelial to mesenchymal transformation in skin cells. • A human cell culture model to test soil As toxicity was developed.

Optimization of mixture parameter for physical and mechanical properties of reactive powder concrete under external sulfate attack using Taguchi method

• Taguchi analysis has been used to determine optimum mix design parapeter of RPC exposed to different Na 2 SO 4 solutions and exposure conditions. • Optimized level for RPC mixture with different water to binder ratio, steel fiber contents, and silica fume contents depends on different external sulfate attack exposure conditions. • RPC appears to be sustainable and durable material under different external sulfate attack exposure conditions. Reactive powder concrete (RPC) is defined as a cementitious composite material with an optimized size of granular constituents, very low water-to-binder ratio (w/b), pozzolanic materials like silica fume (SF), and discontinuous fiber reinforcement. RPC applications include bridge decks and girders, seismic columns, wind turbine towers, and pile foundations. Especially, a durable and robust RPC pile foundation with long service life is essential in building construction because continuous maintenance is impossible. Moreover, natural in-situ conditions such as water table, temperature, and sulfate concentration in soil to which the pile foundation is exposed are critical and related to deteriorating the pile foundation. Therefore, the Taguchi design of experiments (DOE) was used in this research to determine the optimal RPC mixture with beneficial characteristics against external sulfate attack (ESA). Mixture design parameters included steel fiber content (0, 1 and 2 %), w/b (0.16, 20 and 0.24), and SF content (15, 20 and 25 %). In contrast, environmental conditions of ESA exposure contained three different sodium sulfate (Na 2 SO 4 ) concentrations (0.35, 1.05, and 3.15 M), cyclic and continuous exposure at normal temperature (20 °C), and continuous exposure at elevated temperatures (40 °C and 60 °C). The analytical and statistical investigation evaluated mass change, compressive strength, and modulus of rupture in RPC mixtures exposed to these conditions for 52 weeks. Test results show that cyclic exposure and increased solution temperature in ESA facilitate RPC damage. If measured after air drying, RPC mixtures subjected to cyclic ESA are especially susceptible to failure. Taguchi analysis indicated the optimum parameters’ level for mass change as: 0 % steel fiber, w/b = 0.16, and 20 % SF content; for the compressive strength: 2 % steel fiber, w/b = 0.24, and 20 % SF content; and, for modulus of rupture: 2 % steel fiber, w/b = 0.20, and 25 % SF content. In conclusion, RPC appears to be sustainable and durable material under different ESA exposure conditions.

Self-healing recovery and micro-structural properties of slag/fly-ash based engineered cementitious composites under chloride environment and tidal exposure

Self-healing behavior of Engineering Cementitious Composites (ECC) has received a lot of attention due to its influence on the durability and mechanical performance of composite structures exposed to marine environment. However, very few studies have reported mechanical recovery of self-healing ECC under marine environmental exposure conditions. This paper reportes an experimental study of self-healing induced mechanical recovery of pre-damaged slag/fly ash based ECC and chloride transport behavior in ECC exposed to simulated marine environmental for up to 120 days. The results show obvious regaining of tensile properties of pre-damaged slag/fly ash based ECC due to self-healing. At the micro-scale level, the presence of abundance fly ash particles facilitates the stress transfer between the fiber and the matrix after self-healing, leading to fiber-bridging strength recovery to roughly the same level as that of the control specimen. Furthermore, the ultimate tensile strength shows a slight recovery for all ECC specimens under tidal and submerged environmental conditions, as compared to the 28-day result. However, as the slag replacement level increases, some inconsistencies emerge. Because of high chloride content and oxygen content, as well as the action of tidal impact, concrete deterioration and corrosion are more intense in tidal and splash zones.

Systematic review in 2000-2020 on early childhood developmental conditions of environmental noise exposure

Systematic review in 2000-2020 on early childhood developmental conditions of environmental noise exposure

An Experimental Study on Structural Concrete Containing Recycled Aggregates and Powder from Construction and Demolition Waste.

For complete utilization of construction and demolition (C&D) waste, an investigation of all size fractions of C&D waste generated during the recycling process should be conducted. In this work, the effects of three recycled concrete materials with different sizes (recycled coarse aggregate (RCA) with a size of 4.75–25 mm, recycled fine aggregate (RFA) of 0.15–4.75 mm, and recycled powder (RP) smaller than 0.15 mm) produced from concrete waste on the fresh and hardened mechanical properties of concrete were evaluated. The replacement ratios of natural coarse and fine aggregates by RCA and RFA were 30, 60, and 100%, and those of ordinary Portland cement for RP were 10, 20, and 30%. The results showed that the concrete properties deteriorated with increasing replacement ratio regardless of the type of recycled materials. The properties were reduced in the order of the use of RFA, RCA, and the simultaneous use of RCA and RFA. In addition, concrete with 30% RP showed lower mechanical strength than concrete with 100% RCA and 100% RFA. However, all concretes could be applicable for structural purposes under different environmental exposure conditions. In particular, concretes with 10% RP and 20% RP showed better cost-benefits compared to natural aggregate concrete with 100% ordinary Portland cement. These promising findings provide valuable initiatives for the effective and complete recycling of C&D waste.

Impact of the Height of Buildings on the Maintainability of Natural Stone Claddings

The buildings’ surroundings’ environmental exposure conditions (e.g., orientation, location, altitude, distance from the sea, temperature, precipitation, presence of damp, exposure to prevailing winds, among others) have a considerable influence on the performance and durability of their envelope. Furthermore, the intensity of these conditions can vary significantly with the height of the building and, consequently, influence the degradation of different parts of the same building in different ways. In a tall building, the upper part is more prone to higher solar radiation levels, temperature variations, and exposure to wind–rain action. On the other hand, external elements at the bottom are more susceptible to high levels of pollution, especially in city centres. In this sense, the main purpose of this study was to analyse the degradation processes in buildings with different heights and understand whether the processes and maintenance requirements are statistically different. A sample of 203 natural stone claddings (NSC), located in Portugal, was used as case study. The sample was collected based on the diagnosis of the degradation condition of these claddings through in situ visual inspections. To predict the degradation process of NSC over time, a stochastic service life prediction model, based on Petri nets (PN), was implemented. This model allows evaluating the performance of NSC by encompassing the uncertainty of the future performance of the claddings. The results obtained through the degradation and maintenance models were compared with real case studies to highlight the real impact of buildings’ height subjected to environmental exposure conditions on the maintainability of NSC.

Estimating Concrete Strength From Nondestructive Testing With Few Core Tests Considering Uncertainties

Abstract Important facilities constructed during last decades of 20th century are near completion of design life. For extending their service life or to evaluate these for new demands (loads), assessment of strength of concrete in existing structure becomes necessary, a task generally performed with nondestructive tests (NDT); ultrasonic pulse velocity (USPV) and rebound hammer being most commonly executed. Compressive strength is estimated using empirical expressions relating NDT to partially destructive tests (PDT) such as core test. For the development of structure-specific expressions, results of adequate number (depending on variability and desired confidence level) of PDT are essential but these might not be available due to operational constraints. Correlation expressions from literature could be used in such cases but having been developed for different ingredients, curing regimes, and environmental exposure conditions, there would be associated uncertainties. A practical method for the estimation of these uncertainties is not readily available in the literature. This article proposes the statistical approach of resampling for quantifying the uncertainty of indirect strength estimates using expressions from literature. Parametric (probability distribution) and nonparametric (bootstrap) tools are employed and demonstrated with a case study from India. Both parametric and nonparametric approaches could capture across-member variability whereas overall uncertainty incorporation, as well as repeatability, was better in nonparametric approach. Parametric approach is traditionally used and well accepted by practitioners in contrast to nonparametric methods, which have certain advantages. The detailed methodology enumerated in the article would be very useful for practitioners across the world.