A hybrid artificial intelligence approach for modeling the carbonation depth of sustainable concrete containing fly ash

One of the major challenges in the civil engineering sector is the durability of reinforced concrete structures against carbonation during the physico-chemical process of interaction of hydrated cementitious composites with carbon dioxide. This aggressive process causes carbon penetration into the reinforcement part, which affects the behavior of the structure during its lifetime due to corrosion risk. A countermeasure is using alternative cementitious materials to improve concrete texture and resist increased carbonation depth (CD). Considering that the CD test requires a long time and a skilled technician, this study strives to provide an alternative approach by moving from traditional laboratory-based methods towards artificial intelligence (AI) techniques for modeling the CD of sustainable concrete containing fly ash (CCFA). Despite the development of single AI models so far, it is undeniable that utilizing metaheuristic optimization techniques in the form of hybrid models can improve their performance. To this end, a new hybrid model from the integration of biogeography-based optimization (BBO) technique with artificial neural network (ANN) is developed for the first time to estimate the CD of CCFA. The error distribution results revealed that 59% of the ANN predictions had errors within the range of (- 1 mm, 1 mm], while the corresponding percentage for the ANN-BBO predictions was 70%, indicating an 11% reduction in the prediction errors by the proposed hybrid model. Furthermore, A10-index highlighted a performance improvement of 78% for the hybrid model, which met the closeness of the predicted values to the observed ones, so that the value of this index for models of ANN and ANN-BBO was 0.5019 and 0.8947, respectively. Analyzing the cross-validation confirmed the reliability and generalizability of the developed model. Also, the three most influential variables in estimating the CD were exposure time (27%), carbon dioxide concentration (22%), and water/binder (18%), respectively. Finally, the superiority of the ANN-BBO model was verified by comparing it with previous studies' models.

Photometric stereo data for the validation of a structural health monitoring test rig

Photometric stereo uses images of objects illuminated from various directions to calculate surface normals which can be used to generate 3D meshes of the object. Such meshes can be used by engineers to estimate damage of a concrete surface, or track damage progression over time to inform maintenance decisions. This dataset [1] was collected to quantify the uncertainty in a photometric stereo test rig through both the comparison with a well characterised method (coordinate measurement machine) and experiment virtualisation. Data was collected for 9 real objects using both the test rig and the coordinate measurement machine. These objects range from clay statues to damaged concrete slabs. Furthermore, synthetic data for 12 objects was created via virtual renders generated using Blender (3D software) [2]. The two methods of data generation allowed the decoupling of the physical rig (used to light and photograph objects) and the photometric stereo algorithm (used to convert images and lighting information into 3D meshes). This data can allow users to: test their own photometric stereo algorithms, with specialised data created for structural health monitoring applications; provide an industrially relevant case study to develop and test uncertainty quantification methods on test rigs for structural health monitoring of concrete; or develop data processing methodologies for the alignment of scaled, translated, and rotated data.

Mitigation strategies to reduce particulate matter concentrations in civil engineering laboratories

In the departments of civil engineering, many experiments are conducted in laboratories for educational and research purposes. Varying degrees of respirable dust are generated as the outcome of these experiments, which could cause harm to instructors' and students' health. This study is devised to highlight the importance of indoor air quality in university laboratories. As part of the research, four different particulate matter (PM) sizes (PM1.0, PM2.5, PM4.0, and PM10) were measured during specific experiments-sieve analysis, preparation of the concrete mixture, crushing aggregate by jaw crusher, dynamic triaxial compression test, sieve analysis of silt specimen, cleaning sieve by an air compressor, and proctor compaction test-being conducted periodically in the laboratories of civil engineering departments. The measured values are mainly high compared to indoor air quality standards. Mitigation strategies were applied to reduce indoor air PM levels in the three experiments that contained the highest PM levels. The results have shown that mitigation strategies applied as control measures could make a remarkable difference in protecting instructors and civil engineering students.

Coupling relationships between urban block spatial morphology and microclimate in severe cold regions

This study investigates the relationship between urban block spatial morphology and microclimate in severe cold regions, using Shenyang, China as a case study. We employed computational fluid dynamics theory-based numerical simulation software and a controlled variable approach to analyze the microclimate effects of four key aspects: street conforming line ratio, street interface density, street aspect ratio, and building roof forms. The primary findings are as follows: Decreasing conforming line ratios initially increase average wind speed and temperature. Lower interface densities reduce average wind speed but raise temperature. Higher aspect ratios correspond to increased wind speed and decreased temperature. Additionally, upward sloping roofs correlate with higher average wind speed and temperature. This research provides a perspective for evaluating urban microclimates, considering human perception of urban block space. It also suggests spatial layout design strategies for different types of streets in severe cold regions, considering the climate environment.

A systematic review of the role of 4D printing in sustainable civil engineering solutions

This systematic review, not financially supported by any funding body, aims to synthesize the current knowledge on the applications, potential benefits, and challenges of 4D printing in civil engineering, with a focus on its role in sustainable solutions. Comprehensive searches were conducted in Scopus, Web of Science, and Google Scholar using related keywords. Articles that discussed 4D printing within civil engineering and construction contexts, encompassing both conceptual and empirical studies, were included. The findings suggest that 4D printing, with its time-responsive transformation feature, can enhance design freedom, improve structural performance, and increase environmental efficiency in construction. However, challenges persist in material performance, scalability, and cost. Despite these, ongoing advancements signal potential future developments that could widen the opportunities for large-scale applications of 4D printing in civil engineering. The potential use of renewable, bio-based materials could also lead to more sustainable construction practices. This review highlights the transformative potential of 4D printing, underlining the need for further research to fully leverage its capabilities and address current limitations. 4D printing emerges as a promising avenue for sustainable civil engineering solutions, offering a transformative approach that calls for continued exploration and development.

Antecedents of civil engineering students' entrepreneurial intentions: Dataset article

The Kingdom of Morocco has implemented significant reform projects over the past decade to promote youth entrepreneurship. In light of these efforts, it is essential to examine the antecedents of entrepreneurial intentions among students. To this end, the current data article aims to explore the antecedents of civil engineering students' entrepreneurial intentions. Thus, we collected data from civil engineering students using a self-administered questionnaire through Google Forms. We employed the partial least squares structural equation modeling (SEM) to analyze the collected dataset. The data analysis using SmartPLS software showed that entrepreneurial attitude, entrepreneurial capacity, and subjective norms positively and significantly affect the civil engineering students' entrepreneurial intention. The insights from this study can be used by Moroccan higher education institutions (HEI) managers to identify crucial elements that can improve students' inclination towards entrepreneurship.

Interrelated dataset of rebound numbers, ultrasonic pulse velocities and compressive strengths of drilled concrete cores from an existing structure and new fabricated concrete cubes

Two test series were examined using nondestructive measuring methods by six independent laboratories before determining their compressive strength. The nondestructive test methods used were the rebound hammer and ultrasonic pulse velocity measurement. Two types of geometries were investigated: drilled cores and cubes. The measurement procedure for each of these datasets is conditioned to the geometry and is therefore different. The first series consists of 20 drilled cores (approximately diameter/height = 10 cm/20 cm) from the 55-year-old Lahntal Viaduct near Limburg, Germany. After preparation in the first laboratory, the lateral surface of the drilled cores was tested with the rebound hammer using a given pattern. Every laboratory tested every drilled core at different locations. Ultrasonic measurements in transmission were performed repeatedly at predefined points on the flat surfaces of the specimen. The second series consisted of 25 newly manufactured concrete cubes of a mix with a target concrete strength class of C30/37. The edge length was 15 cm. Each laboratory received five specimens of this test series. Thus, contrary to the first series, each specimen was tested by only one laboratory. Two side faces of each cube were tested with the rebound hammer. In addition, ultrasonic measurements were performed by one laboratory. The time of flight was measured between the tested side faces of the rebound hammer at different positions. For both series, rebound hammers were used to determine the R-value as well as the Q-value. The rebound hammer models within the laboratories were always the same, while they differed between the laboratories. The ultrasonic measurements took place with different measurement systems and couplants. Finally, both specimen series were tested destructively for compressive strength. The dataset contains the raw data summarized in tabular form. In addition, relevant calculated data are included in some cases. For the ultrasonic measurements, the time of flight has already been converted into the ultrasonic velocity. Besides, in addition to the raw data of the compressive strength test (force, weight, and geometry values), the calculated compressive strengths and densities are also provided.

Low frequency ultrasonic pulse-echo datasets for object detection and thickness measurement in concrete specimens as testing tasks in civil engineering

The dataset contains raw data gathered with the ultrasonic pulse-echo method on concrete specimens. The surfaces of the measuring objects were automatically scanned point by point. Pulse-echo measurements were performed at each of these measuring points. The test specimens represent two typical testing tasks in construction industry: the detection of objects and the determination of dimensions to describe the geometry of components. By automating the measurement process, the different test scenarios are examined with a high repeatability, precision and measuring point density. Longitudinal and transversal waves were used and the geometrical aperture of the testing system was varied. The low-frequency probes operate in a range of up to approximately 150 kHz. In addition to the specification of the geometrical dimensions of the individual probes, the directivity pattern and the sound field characteristics are provided. The raw data are stored in a universally readable format. The length of each time signal (A-scan) is two milliseconds and the sampling rate is two mega-samples per second. The provided data can be used for comparative studies in signal analysis, imaging and interpretation as well as for evaluation purposes in different, practically relevant testing scenarios.

Growing role of concrete in sand and climate crises

Concrete production poses multiple sustainability challenges, including resource over-exploitation and climate change. Here we show that growing global demand for buildings and infrastructure over the past three decades has quadrupled concrete production, reaching ∼26 Gt/year in 2020. As a result, annual requirements for virgin concrete aggregates (∼20 Gt/year) exceeded the extraction of all fossil fuels (∼15 Gt/year), exacerbating sand scarcity, ecosystem destruction, and social conflict. We also show that despite industry efforts to reduce CO₂ emissions by ∼20% per unit of production, mainly through clinker substitution and improved thermal efficiency, increased production has outweighed these gains. Consequently, concrete-related CO₂ emissions have tripled between 1990 and 2020, and its contribution to global emissions has risen from 5% to 9%. We propose that the policy agenda should focus more on limiting production growth by changing how concrete structures are designed, constructed, used, and disposed of to address the sand and climate crises.

Road to zero: Research and industry perspectives on zero-emission commercial vehicles

Medium-and heavy-duty vehicles (MHDVs) comprise only a small fraction of vehicles on the road but disproportionately contribute to greenhouse gas emissions and air pollution from the transportation sector. Given the large variety of vehicle types-ranging from heavy-duty pickup trucks and box trucks to full-size buses and Class 8 tractor semi-trailers-and applications, multiple technologies offer opportunities to decarbonize MHDVs including battery-electric vehicles, hydrogen fuel cell vehicles, and sustainable liquid fuels. Here we provide an overview of the status, opportunities, challenges, and uncertainties for these competing-and potentially complementary-technologies, including consideration of supporting infrastructure and prospects for future success. We find a bright outlook for zero-emission vehicles and discuss remaining barriers and uncertainties around fleet decisions and changes to vehicle operation, infrastructure, manufacturing, and future fuel and technology trends that can be informed through analysis.

Monitoring the impact of climate extremes and COVID-19 on statewise sentiment alterations in water pollution complaints

The COVID-19 pandemic and associated prevention policies can directly or indirectly alter the sentiment of individuals while registering water pollution complaints, but observational evidence remains limited. Here, we conducted a sentiment analysis on over 10,000 water pollution complaints from residents in Alabama, USA (2012-2021) to better understand how and to what extent COVID-19 has altered emotion (polarity score-based) and attitude (subjectivity) of water pollution complaints. We found that the 2017 state-wise drought significantly increased the percentage of negative water pollution complaints by +35%, with no significant alternation in attitude before the COVID-19 pandemic. Since COVID-19, the percentage of negative and subjective water pollution complaints significantly decreased and increased by -30 and +20%, respectively, and these sentiment alternations were maintained by 2021. This study provides a new direction for environmental governance and management, requiring a timely response to changes in the public's emotions and attitudes during the next climate extremes and pandemics.

Cities can benefit from complex supply chains

Supply chain complexity is perceived to exacerbate the supply disruptions or shocks experienced by a city. Here, we calculate two network measures of supply chain complexity based on the relative number-horizontal complexity-and relative strength-vertical complexity-of a city's suppliers. Using a large dataset of more than 1 million annual supply flows to 69 major cities in the United States for 2012-2015, we show that a trade-off pattern between horizontal and vertical complexity tends to characterize the architecture of urban supply networks. This architecture shapes the resistance of cities to supply chain shocks. We find that a city experiences less intense shocks, on average, as supplier relative diversity (horizontal complexity) increases for more technologically sophisticated products, which may serve as a mechanism for buffering cities against supply chain shocks. These results could help cities anticipate and manage their supply chain risks.

Urban agriculture in walkable neighborhoods bore fruit for health and food system resilience during the COVID-19 pandemic

Urban agriculture is the key to creating healthy cities and developing resilient urban food systems in uncertain times. However, relevant empirical evidence is limited. This study quantitatively verified the association of access to local food through urban agriculture with subjective well-being, physical activity, and food security concerns of neighborhood communities in the context of the COVID-19 pandemic. The target was Tokyo, Japan, where small-scale local food systems are widespread in walkable neighborhoods. We found that diversity in local food access, ranging from self-cultivation to direct-to-consumer sales, was significantly associated with health and food security variables. In particular, the use of allotment farms was more strongly associated with subjective well-being than the use of urban parks, and it was more strongly associated with the mitigation of food security concerns than the use of food retailers. These findings provide robust evidence for the effectiveness of integrating urban agriculture into walkable neighborhoods.

Low frequency ultrasonic dataset for pulse echo object detection in an isotropic homogeneous medium as reference for heterogeneous materials in civil engineering

The dataset presented contains ultrasonic data recorded in pulse echo mode. The investigated specimen is made of the isotropic homogeneous material polyamide and has a drill hole of constant diameter running parallel to the surface, which was scanned in a point grid using an automatic scanner system. At each measuring position, a pitch-catch measurement was performed using a sampling rate of 2 MHz. The probes used are arrays consisting of a spatially separated receiving and in-phase transmitting unit. The transmitting and receiving sides each consist of 12 point-shaped single probes. These dry-point contact (DPC) probes operate according to the piezoelectric principle at nominal frequencies of 55 kHz (shear waves) and 100 kHz (longitudinal waves), respectively, and do not require a coupling medium. The measurements are performed with longitudinal (100 kHz) and transverse (55 kHz) waves with different geometric orientations of the probe on the measurement surface. The data presented in the article provide a valid source for evaluating reconstruction algorithms for imaging in the low-frequency ultrasound range.

Construction and demolition waste as recycled aggregate for environmentally friendly concrete paving

Recycled aggregates (RA) from construction and demolition waste (CDW) instead of natural aggregates (NA) were analysed in the manufacture of new eco-friendly concrete. Fine (FRA) and coarse (CRA) recycled aggregates were used in different percentages as substitutes of natural sand and gravel, respectively. The results revealed that the use of RA in percentages of up to 50 wt.% is feasible. Additionally, RA were used to produce paving blocks in accordance with industrial requirements. Thus, values of water absorption lesser than 6.0% and tensile strength upper than 3.6 MPa were obtained, which are similar to those of a reference sample and within the limit values established by the regulations. These results were achieved by reducing the incorporation of cement, thereby saving production costs and minimizing environmental impact.

An Improved Animal Migration Optimization Algorithm to Train the Feed-Forward Artificial Neural Networks

The most important and demanding part of the artificial neural network is the training process which involves finding the most suitable values for the weights in the network architecture, a challenging optimization problem. Gradient approaches and the meta-heuristic approaches are two methods extensively used to optimize the weights in the network. Gradient approaches have serious disadvantages including getting stuck in local optima, inadequate exploration, etc. To overcome these disadvantages, meta-heuristic approaches are preferred in training the artificial neural network instead of gradient methods. Therefore, in this study, an improved animal migration optimization algorithm with the Lévy flight feature was proposed to train the multilayer perceptron. The proposed hybrid algorithm is named IAMO-MLP. The main contributions of this article are that the IAMO algorithm was developed, the IAMO-MLP algorithm can successfully escape from local optima, and the initial positions did not affect the performance of the IAMO-MLP algorithm. The enhanced algorithm was tested and validated against a wider set of benchmark functions and indicated that it substantially outperformed the original implementation. Afterward, the IAMO-MLP was compared with ten algorithms on five classification problems (xor, balloon, iris, breast cancer, and heart) and one real-world problem in terms of mean squared error, classification accuracy, and nonparametric statistical Friedman test. According to the results, the IAMO was successful in training the multilayer perceptron.

Effect of overburden confining stress on hydraulic performance of geosynthetic clay liners (GCLs)

Geosynthetic clay liners are a rapidly evolving geosynthetic product used in most hydraulic barrier applications in the geo-environmental industry. Continuous research has led to new insights to overcome the shortcomings faced in deploying GCLs in the field. These include shrinkage due to shear failure on side slopes, the effect of temperature variation, and inadequacy of minimum timely confinement to achieve optimum hydraulic performance. This paper presents previous experimental data and an additional dataset from this research gathered to observe the effect of overburden confining stress on GCL hydraulic conductivity and how the findings can be used to predict the performance of a geosynthetic clay liner for a given field application. An inverse power relationship is identified between these two parameters along with the reduction in the order of the degree of hydraulic conductivity depending on the permeant material passing through. A relationship is determined to estimate the GCL hydraulic conductivity as a function of the overburden confining stress, given that it is pre or post hydrated and the permeant liquid passing through the product. It is proposed that the relationship can be used to predict the GCL hydraulic performance in the field and provide guidance in improving the serviceability of hydraulic barrier designs.

Investigation of Taguchi optimization, equilibrium isotherms, and kinetic modeling for cadmium adsorption onto deposited silt

The feasibility of deposited silt as an adsorbent to eliminate Cadmium (Cd) from aqueous solution is assessed in this study. The optimum adsorption condition was determined with the help of the Taguchi experimental design. The treatment process of the deposited silt is controlled by various parameters like pH of the solution; a dose of deposited silt; initial Cd metal concentration, and contact time are optimized in batch mode. It also recognizes the contribution of each well-regulated factor. The outcomes of experiments show that the major contribution of the controllable factors for Cd removal is the pH of the solution > stirring time > dose of deposited silt > initial concentration of Cd metal ions. Analysis of Variance (ANOVA) was used to determine significant parameters which contribute to the adsorption process. Results indicate that cadmium removal is mostly influenced by pH 88.17 %, followed by contact time 5.86%, adsorbent dose, 2.41%, and initial metal ion concentration 0.60%. Cadmium adsorption data well fitted to the Langmuir isotherm model. The pseudo-second-order is the best model that explained cadmium adsorption kinetics.

Geotechnical evaluation of clayey materials for quality burnt bricks

Understanding of clayey materials properties continues to elude brick manufacturers, hence unsure of their application for brick making purposes. The raw materials were assessed geochemically, mineralogically, physically and technologically. The geochemical result showed that the fluxing oxides K₂O, N₂O, CaO, MgO and MnO are generally low in content with average abundance ranging from 0.06% to 1.78%. The Fe₂O₃ content varies (4.8–25.5%) thus reflects heterogenous stability in tonality. Most of the studied samples have relatively high Al₂O₃ content which suggest the bauxitic composition from which kaolinite minerals might have resulted from. The XRD analysis revealed the presence of kaolinite and chlorite as the major clay minerals while quartz, feldspar, talc and hornblende were present as non-clay minerals. For DTA, the threshold of new crystallization processes were attained at 1000 °C. The SEM analysis revealed the presence of some stroma in all samples although with sizes >50 nm. These pores were suggested to constitute a capillary system where molten mineral occupy as temperature increases. The Atterberg's limit indicated that the studied materials are inorganic silts with high compressibility and organic clays properties since it plotted below the A-line of plasticity chart. The compressive strength (CS) for brick specimens made from kaolinite-rich material are relatively higher than chlorite-rich specimens. This was attributed to the ineffective pore connection within the kaolinite interstitial particles compared to the chlorite-rich specimen, hence increasing the density. The water absorption (WA) test on twenty brick specimens showed that the pore volume and capillarity for bricks which are chlorite-dominated were comparatively higher, thus absorbing more water molecules. These results revealed that majority of the studied clayey material are not suitable for double storey construction bricks but meet the requirements for single-storey construction when compared with SANS standards.

Mathematical model for the duration of runoff formation determined from the road surface

Introduction

Many scientists were engaged in the problems of studying the runoff formation conditions from the water-intake basins area and studying the operation of rainwater drainage systems and its calculations. Among them: Alekseev M. I., Belov М. М., Dykarevskyi V. S., Kurganov А. М., Zhuk V. M., Tkachuk S. G., Salchuk V. L., Tkatchuk O. A., Shevchuk O. V., Dziopak J., James W., Horton R., Huber W., Mays L. W., Rossman L. A., Weitman D. [1–9] and others. The drainage systems calculation is implemented based on empirical or semi-empirical studies for pipes or open water bodies. Unlike the generally accepted conditions for the urban city areas drainage elements calculation, highways have the features of runoff and the formation of maximum runoff. Artificial surfaces of surface runoff are characterized by low water absorption, significant longitudinal and transverse slopes. According to State Building Norms DBN V.2.3–4:2015 «Highways. Part I. Design. Part II. Construction», the largest longitudinal slope for a category I road is 40 %, the carriageway transverse slope on straight sections is 25 %. In the world of engineering practice there is no single generally accepted approach to the construction of hydrographs of rainwater inflow to surface drainage structures. Therefore, the question remains open in terms of establishing the estimated rain duration and the surface runoff volume from the roads surface in particular.

Goal and problem

To explore and establish the main factors and their parameters for the surface runoff formation from road surfaces.

Research methods

In engineering practice, forecasting the estimated rain duration is defined as the time from its beginning to the time of collection by the drainage system. This research is based on the prediction method and analysis of the factors, which influence the effluents movement on the coating surface of the linear in the plan water-intake basins. Conducting research with the forecasted natural meteorological phenomenon and at the minimum estimated rain intensity values according to climatic conditions of Ukraine.

Results

The analysis of known methods for duration of surface runoff formation determining performed. For its determination, it is suggested to take into account the surface wetting duration and the influence of the viscous component of the friction force between the runoff layers. An analytical dependence for the surface runoff formation duration determining for highways with asphalt concrete pavement and variable longitudinal slope in the range from 0‰ to 30‰ is obtained. The influence of wastewater viscoelastic properties is determined. The influence of the calculated precipitation intensity on the surface runoff formation duration for linear water-intake basins is determined.

Conclusions

A mathematical model for determining the surface runoff formation duration for linear water-intake basin, namely highways, taking into account the estimated highway slope, the width of the carriageway, the estimated rainfall. A comparative analysis with existing methods is performed.

Dynamic transparency in design: the revival of environmental sustainability in design elements of Iraqi buildings

Buildings in Iraqi cities such as Baghdad and Mosul suffer from several problems such as the application of new materials in modern buildings that changed not just the identity of architectural heritage but also the quality of thermal comfort in façade design. This, unfortunately, adds to the damage regarding environmental sustainability and cultural values away from adaptable solutions to improve energy efficiency in building performance. One of the measures that must be taken to correctly plan in harmony with the Iraqi cities is to ensure the environmental control as part of the overall performance of building façade to maintain an active, healthy indoor environment while preserving the propriety of facade design elements, screen pattern, order and details. Therefore, there are many sustainable trends that vary in their usefulness such as biomimetics examples inspired from natural models in which form and function dictate one another. This is in order to maintain the integrated design relation between transparency, function, and elegance in the overall performance of façade elements. The research question is, how important is the choice of material in developing a sustainable element that revives environmental control while preserving the identity and values of façade design? The main goal of the research study is to identify the role of advanced technologies and the choice of smart glazing materials to revive the quality of thermal comfort in a way that not just sustains the identity of facade elements socially and culturally, but also to be responsive to the changes of climate conditions. Therefore, this research utilizes more than one technological tool such as Revit as a BIM tool with the application of smart dynamic materials such as Photovoltaics and Electrochromic in order to restore part of the design expression and enhance the building performance through its elements in contemporary façade design and its details. In this work, it can be seen that applying a set of technological tools allows to clearly illustrate the impact of smart dynamic materials to improve the quality of design and comfort while protecting the identity of contemporary façade elements when compared to static or traditional materials, aesthetically, and functionally.

Non-destructive characterization of physical and chemical clogging in cylindrical drip emitters

Characteristics and deposition pattern of clogging material on cylindrical drip emitters was studied using non-destructive methods of evaluation. Two sets of four cylindrical emitter samples were collected from farm lands. One set of sample emitters was analyzed using Computed Tomography (CT). Other set was dissected and the clogging material extracted was analyzed using Energy Dispersive X-Ray Fluorescence (EDXRF) and X-Ray Diffraction (XRD). CT scans revealed the geometric properties of emitters and the spread of clogging material on the emitter surface. EDXRF analysis found statistically significant inverse relationship between the proportion of physical clogging and chemical clogging materials. XRD analysis indicated presence of physical and chemical clogging materials in their crystalline forms. Emitters having transverse flow path and the boundary optimized with curvature found with the least deposition of physical clogging materials. Corresponding proportion of chemical clogging (as Ca) was found to be much higher. All the samples were found with more clogging material closer to the outlets. Efforts to optimize emitter geometry shall also take into account the outlet area optimization and chemical clogging for obtaining best results.

Determination of the hydraulic conductivity function of grey Vertosol with soil column test

Expansive soils exhibit swell-shrink behaviour in wet-dry periods resulting in distresses on light-weight structures founded on/in them. Therefore, it is essential to investigate the climate-ground interaction when designing structures on expansive soils. Laboratory-based models are preferred to investigate the climatic-ground interaction of expansive soils due to the uncontrollability of the boundary conditions and expenses associated with field monitoring. More flexibility in analysing the climatic-induced hydraulic responses in expansive soils can be achieved by finite element modelling of data from physical model tests. However, these laboratory-based models regularly encounter the effects of boundary flaw, preferential flow paths and entrapped air that needs to be accounted for when numerically simulated. In this study, the authors aim to numerically model the hydraulic responses in an instrumented Vertosol soil column (ISC) under controlled laboratory conditions. The effects of the preferential flow paths and boundary flaws were incorporated into a modified hydraulic conductivity as a practical approach to model the hydraulic responses in ISC. Influence of the entrapped air was rectified by a suitable correction factor. These findings present a practical method for geotechnical practitioners to accurately estimate the suction and volumetric water content profiles in laboratory-based expansive soil model tests.

A comparison study between CFD analysis and PIV technique for velocity distribution over the Standard Ogee crested spillways

A comprehensive study was performed to compare flow rate, mean velocity, vertical velocity distribution, and locations where the maximum velocity, d_m, occurs on standard Ogee-crested spillways using experimental and numerical models. Five different models were constructed from rigid foam according to the specifications of the United States Army Corps of Engineers (USACE). The velocity of the flow was recorded along the downstream curve of the model for all models with different non-dimensional head ratios H/H_d of 0.50, 1.00, and 1.33. Particle Image Velocimetry (PIV) was used to measure the flow velocities. Velocity distributions were obtained by analyzing a series of captured images using Matlab codes. A commercially available Computational Fluid Dynamics (CFD) software package, Flow-3D, was used for modelling the experimental model setups. Flow-3D analyzes the Reynolds-averaged Navier-Stokes equations and is widely verified for use in the field of spillway flow analysis. The maximum difference between numerical and experimental results in mean velocity values that do not exceed 6.2% for all values of head ratios. The interpolated values of recorded maximum velocity by the PIV technique are smaller than those values numerically computed. In the lower d_m locations, the percent difference between these regions reaches -8.65%; the upper locations are 2.87%. The vertical location (d_m) drops to the lower location when the upstream head increases, and the distance from the spillway axis decreases linearly.

Simulation study for natural ventilation retrofitting techniques in educational classrooms - A case study

Building retrofitting plays a critical role in achieving sustainable development and is an efficient way to improve the indoor air quality (IAQ) of existing spaces. The IAQ in classrooms has a significant impact on the health and academic achievement of students. However, improving the IAQ of existing classrooms is challenging if minimum architectural modifications are allowed. Different natural ventilation retrofitting techniques were proposed to improve the IAQ in existing classrooms at Jordan University of Science and Technology, which is located in a hot arid region. Computer simulations were used to analyze the ventilation rate, indoor operative temperature, relative humidity, and CO₂ concentration in the base Case classroom and after the implementation of the proposed retrofitting techniques. Simulation results were compared with those obtained in the base case to determine the most efficient natural ventilation retrofitting technique. The best results were obtained by using a solar chimney to assist a wind tower, which resulted in an increase in the comfort hours during the occupation time, an improvement in the average monthly ventilation rate range, a decrease in the CO2 concentration, and an improvement in the relative humidity ratio. An energy-saving of 39% would be achieved compared with the use of split unit air condition systems. Economic assessment of the proposed system using net present value indicates positive economic viability.

Enforcement of legal remedies against construction projects time overrun in Ethiopia: A critical appraisal

Construction time overrun is one of the common inefficiencies of public construction projects in Ethiopia. Laws and standard construction contracts stipulate different legal remedies against project time overrun. This paper is meant to unravel these legal remedies and their application to construction project time overrun in public construction projects in Ethiopia. To this end, the magnitude of time overrun, its common causes, and the practical implementation of legal remedies against it is exposed through literature review, primary data obtained from 18 roads and 10 public building projects, and interviews of 10 key informants. The result showed, although time is not the essence of construction contract in international standard conditions of contracts, it is a fundamental obligation the breach of which would give rise to termination of the contract under the laws and standard conditions of contracts applicable to public works in Ethiopia. However, the paper established that the practical implantation of these legal remedies against time overrun in public construction projects is very erratic although time overrun is a rampant challenge of the construction industry of the country in general and public construction projects in particular.

Thermal storage properties of lightweight concrete incorporating phase change materials with different fusion points in hybrid form for high temperature applications

In this study, the thermal storage properties of lightweight concrete incorporating two types of phase change materials (PCM) with two different fusion points were investigated. Two types of PCM, polyethylene glycol (PEG) and paraffin (PRF), were impregnated into porous aggregates using high temperatures. The PCM aggregates were mixed with concrete at different proportions of PEG/PRF aggregates from 0/100 to 100/0 with 25% intervals. The experimental series consisted of thermal property tests (such as thermal conductivity, specific heat, and latent heat), and some basic properties (such as compressive strength, density, water absorption, and abrasion resistance). The results showed that incorporating PCM aggregates into lightweight concrete helped increase the workability, lower the moisture absorption, and increase the mechanical properties. For thermal properties, both thermal conductivity (k) and specific heat were found to depend strongly on the state of PCM. The latent heat of lightweight concrete with PCM aggregates in hybrid form were found to be higher than that of single type PCM aggregates.

The effect of using polyethylene terephthalate as an additive on the flexural and compressive strength of concrete

The annual consumption of plastics in Nigeria has increased drastically and plastic wastes recycling has become one of the major challenges in recent times. Polyethylene Terephthalate (PET) has been selected in this study to ascertain its possible use as an additive in concrete construction. The study used the experimental research design in carrying out its work. The PET was pulverized so that it can mix with the concrete. The pulverized PET was used in concrete with percentages of 5 %, 10 %, and 15 % by weight of conventional fine aggregate. Four types of concrete specimens including the control were prepared. The flexural and compressive strength of the concrete specimens were tested, after a curing period of 3 days, 7 days, 14 days, and 28 days respectively. The result showed that the concrete specimen containing PET at 5 % by weight showed higher compressive strength than other specimens. The flexural strength of concrete specimens containing PET aggregate was below that of the control concrete.

Influence of chemical treatment on the properties of cement-paper hybrid composites for ceiling board application

This study evaluates the effect of treated and untreated jute fiber/eggshell particulate reinforced cement-paper matrix composites for ceiling board application. Treated jute fiber (TJF) was obtained by immersing untreated jute fiber (UJF) into 1.25 M sodium hydroxide (NaOH) solution in a shaker water bath maintained at 40 °C for 4 h. Eggshells (ESP) were pulverized and sieved to -75μm. Samples were prepared by varying the fiber volume fraction from 0.5 to 2.5 wt.% in the composites. While other constituents such as the binder (cement) and eggshell were kept constant. An hydraulic press cold compaction molder was utilized in the production of the hybrid composites in a predetermined mix ratio designed based on previous research. The samples produced were cured for 7 and 14 days, then sundried for 36 h. The physical, thermal, mechanical and wear behaviour of the produced composites were evaluated while the surface morphology of the fractured splitting tensile samples were analyzed. The result reveals that TJF/ESP hybrid composites had better performance than UJF/ESP hybrid composites in most of the tests carried out. Increase in the number of curing days was found to also enhance the properties of the composite produced in majority of the test evaluated. The 0.5 wt.% UJF/ESP gave the least performance of all the composites developed. While 2.5 wt. % TJF/ESP showed an optimum properties among the composites tested. When compared with standard, it is concluded that the hybrid composites developed can be suitable for ceiling boards and also find possible application in wall partitioning.

Numerical study of pedestrian suspension bridge with innovative composite deck

The increasing trend of using light and slender deck in pedestrian bridge has raised the issue of instability under pedestrian movement. The suspension pedestrian bridges are more vulnerable as lateral vibration often occurred in such type of bridges. Hence, the current paper targeted to develop a pedestrian suspension bridge with a new type of composite deck using Glass Fibre Reinforced Polymer (GFRP) in the bottom layer and laminated glass in the top layer. The safety and serviceability of the developed pedestrian bridge is rigorously investigated. The performance of the suspension pedestrian bridge is comprehensively investigated by monitoring important response parameters such as stress, deflections, natural frequencies and accelerations under pedestrian loads and compared with current bridge design code requirements. The developed suspension pedestrian bridge with new type of composite deck could adhere the requirements of the bridge design code. Hence, the suspension pedestrian bridge mentioned in this paper is recommended for pedestrian use for its standard safety and serviceability.

Role of local town planning authorities in building collapse in Nigeria: evidence from Enugu metropolis

The current spate of building collapse in Nigeria has continued to attract research efforts to unravel the causes and possible remedies. Although cases of building collapse in Nigeria has been associated with several factors, those factors associated with building plan approval process have not adequately investigated, especially in a rapidly expanding colonial city of Enugu. The study investigated the role of local town planning authorities in the increasing cases of collapsed buildings in Nigeria using Enugu as a case study. A well-structured questionnaire was administered to the three Chief Town Planners in the three planning approval offices and oral interviews randomly selected 30 developers in ongoing construction projects within Enugu metropolis were conducted. Using content analysis and descriptive statistics the data collected were analyzed. It was observed that due to poor staffing and lack of engagement of building professionals, the planning approval authorities were not effective in scrutinizing, vetting and evaluating building drawings submitted for approval as well as in supervising and monitoring the level of compliance of buildings under construction with the operational building codes and bye-laws in the study area. The study concludes that these lapses in the roles of local building approval authorities can contribute to the increasing cases of collapsed buildings in Enugu Metropolis. It recommends that government should take proactive steps by engaging the right number of building professionals in her planning approval offices and ensuring strict enforcement of the existing physical development legislation and punishment of offenders.

Impact of atmospheric boundary layer inhomogeneity in CFD simulations of tall buildings

Recently, there has been a growing interest in utilizing computational fluid dynamics (CFD) for wind analysis of tall buildings. A key factor that influences the accuracy of CFD simulations in urban environments is the homogeneity of the atmospheric boundary layer (ABL). This paper aims to investigate solution inaccuracies in CFD simulations of tall buildings that are due to ABL inhomogeneity. The investigation involves two steps. In the first step, homogenous and inhomogeneous ABL conditions are generated in an empty computational domain by employing two different modelling approaches. In the second step, the homogenous and inhomogeneous conditions are each applied to an isolated tall building, and simulation results are compared to investigate impact of ABL inhomogeneity on wind load predictions. The study finds that ABL inhomogeneity can be a significant source of error and may compromise reliability of wind load predictions. The largest magnitude of inhomogeneity error occurred for pressure predictions on the windward building surface. Shortening the upstream domain length reduced inhomogeneity errors but increased errors due to wind-blocking effects. The study proposes a practical approach for detecting ABL inhomogeneity that is based on monitoring sensitivity of key output metrics to variations in upstream domain length.

Process parameters optimization for eco-friendly high strength sandcrete block using Taguchi method

The need for developing sustainable cement-based materials is crucial for the prevention of environmental degradation and promotion of sustainable technologies. In the present study, a sustainable cement-based material was developed for sandcrete block production using coconut shell ash (CSA). The product development was executed using the Taguchi robust design approach, in which an L18 mixed level orthogonal array was adopted. The process parameters investigated were the end-web to center-web (E/C) ratio of the sandcrete block, water-cement (W/C) ratio and CSA content. The evaluated responses include the compressive strength (CS), bulk density (BD) and water absorption (WA). The result obtained showed that for the CS, all the process parameters had a statistically significant effect at 0.05 alpha level, while only the W/C ratio had a statistically significant effect on the BD and WA. The optimal settings of the process parameters for CS and BD were obtained at E/C ratio of 1:2, W/C ratio of 0.65 and CSA content of 5% while that for WA was obtained at E/C ratio of 1:1, W/C ratio of 0.65 and CSA content of 20%. The developed sandcrete blocks are suitable for load-bearing masonry units and areas with moisture exposure.

Cost-benefit analysis of the production of ready-mixed high-performance concrete made with recycled concrete aggregate: A case study in Thailand

In the current green concrete structures, recycled concrete aggregate is used as recycled concrete waste. In this process, concrete waste is collected and crushed using a recycling procedure in order to produce crushed concrete which is then used in structural concrete where it replaces natural aggregate which is coarse. The recycled aggregate concrete is a sustainable concrete waste which in the long term can replace the demand for natural aggregate, a process which would, in turn, lead to its preservation. However, most concrete industries have been observed to be reluctant in the production of recycled aggregate concrete and utilization in its maximum potential. Industries are yet to embrace it not only due to its uncertain material performance but also due to its unexplored manufacturing plant operations which are yet to be established. This research aims to use of a cost-benefit analysis model of the production of ready-mixed high-performance concrete made with recycled concrete aggregate in Thailand. The model focuses on the evaluation of the financial effects which favor the recycled aggregate concrete manufacturing operations instead of the ordinary concrete. Research findings indicate that regardless of the manufacturing plant used, the price of recycled concrete aggregate cannot decrease below the price of natural aggregate concrete. The key result of this research is that recycled concrete aggregate manufacturing set-ups can be used in the industrial-scale manufacture of recycled concrete and at low prices. In addition, overhead bin type and front-end loader type of plants can be used to lower the incremental costs of recycled concrete aggregate. However, the demand and supply factors and the pricing effects of recycled concrete pose various difficulties which are hardly accounted for.

Assessing the policy issues relating to the use of bamboo in the construction industry in Nigeria

The Nigerian government has promoted industrial development based on the area of policy implementation. The development of policy and the use of bamboo in the construction company is very significant because of the role of bamboo cultivation in reducing environmental pollution. Bamboo, in its existence, applies to the environment in absorbing carbon dioxide of about 35% and releases to the environment a high amount of oxygen. This carbon dioxide absorbs by bamboo reduces the ozone layer depletion in the aspect of climate change. Another significance of bamboo is that it creates an environment that reduces the light intensity to protect against ultraviolet emissions. The use of Bamboo is considerable in the construction industry and also as useful reinforcement material. This research discusses the effects of policy issues relating to the use of bamboo in the construction industry in Nigeria. And also, study the significance of bamboo implementation in terms of bamboo used for biomass as a source for bio-energy, furniture, and building development. Also, how bamboo cultivation will affect economic growth in Nigeria. This study also discusses the three policy dimensions as it pertains to implementing bamboo policy in Nigeria and suggested ways of developing bamboo policy for proper regulations.

Numerical and experimental study on wind environment at near tower region of a bridge deck

The Large Eddy Simulation (LES) turbulence model was used to investigate the wind environment over the deck near bridge tower and was verified using the wind tunnel tests. Compared with the wind tunnel tests, the computational fluid dynamics (CFD) approach was more convenient for the investigations of the local wind field. It was found that the influence of bridge tower on the wind flow can increase rapidly the wind speed on vehicles while bearing off a narrow zone near the tower. The dangerous situation can be effectively compromised by installing a proper local windshield barrier (WSB) with varying heights and porosity ratios along the bridge span. The length of the influence region of tower on the wind environment over the bridge deck was about 7 times of the tower width, implying a proper length of local windshield barriers on each side of the tower. Parametric studies demonstrated that the length of local WSB with different porosity ratios could affect the slope of equivalent wind speeds, indicating that the shorter the length of local WSB was, the rapider the wind speed of the tower influence region varied.

Buckling of thin skew isotropic plate resting on Pasternak elastic foundation using extended Kantorovich method

The extended Kantorovich method (EKM) is implemented to numerically solve the elastic buckling problem of thin skew (parallelogram) isotropic plate under in-plane loading resting on the Pasternak elastic foundation. EKM has never been applied to this problem before. Investigation of the EKM accuracy and convergence is conducted. Formulations are based on classical plate theory (CPT). Stability equations and boundary conditions terms are derived from the principle of the minimum total potential energy using the variational calculus expressed in an oblique coordinate system. The resulting two sets of ordinary differential equations are solved numerically using the Chebfun package in MATLAB software. In-plane compression and shear loads are considered along with various boundary conditions and aspect ratios. Results are compared to the analytical and numerical solutions found in the literature, and to the finite element solutions obtained using ANSYS software. The effects of the skew angle, stiffness of elastic foundation, and aspect ratio on the buckling load are also investigated. For plates with zero skew angle, i.e. rectangular plates, with various boundary conditions and aspect ratios under uniaxial and biaxial loading resting on elastic foundation, the single-term EKM is found accurate. However, more terms are needed as the skew angle gets bigger. The multi-term EKM is found accurate in the analysis of rectangular and skew plates with various boundary conditions and aspect ratios under uniaxial, biaxial, and shear loading resting on elastic foundation. Using EKM in buckling analysis of thin skew plates is found simple, accurate, and rapid to converge.

Phosphorus removal from secondary wastewater effluent using copper smelter slag

This study investigated the use of copper smelter slag for the removal of phosphorus from secondary wastewater effluent through batch tests. The media was physically and chemically characterized and showed presence of Fe2O3 (45.22%), SiO2 (14.98%), Al2O3 (3.21%), CaO (1.99%), SO3 (1.77%) and MgO (1.33%). Scanning electron microscopy monographs revealed smooth and flat surface and no heterogeneity on the surface of the slag with visible micro pores before the experiment and less visible after the experiment. The point of zero charge of the media was 5.0. Equilibrium was reached after 4 h at 29.5 ± 0.71% phosphorus removal efficiency and media dosage of 0.4/100 mL. The kinetic data was best described by Pseudo second order equation. More than one mechanisms were involved in the adsorption of phosphorus onto copper smelter slag as suggested by multi-linearity of intra particle diffusion model. Ninety seven percent (97.5 ± 0.0%) removal efficiency was achieved at an equilibrium dosage of 160 gL-1. The equilibrium isotherm was described better by Langmuir equation with observed maximum adsorption capacity of 0.16 mg P g-1 media and the experimental maximum adsorption capacity was 0.26 mg P g-1 media. Regeneration studies showed low performance with maximum efficiency of 11.7% revealed during the first regeneration trial therefore low practical benefits. Copper smelter slag is a poor adsorbent for phosphorus and further studies on the media should be conducted.

Clean vehicles, polluted waters: empirical estimates of water consumption and pollution loads of the carwash industry

Carwash stations use large volumes of water and release harmful chemicals into the environment through their operations. While a significant body of literature has focused on exploring water use in the carwash industry, none has provided comprehensive information on both the pollution loads of the wastewater emanating from this industry and water consumption. Understanding how much water is used and the pollution loads of wastewater from this industry is useful to ensure adoption of water conservation measures and design wastewater recycling systems given the dwindling freshwater resources globally. This study estimated the freshwater quantities used to wash different vehicle types and the pollution loads of the resulting wastewater in the Kumasi Metropolis. Seven proxy carwash stations were purposively selected and monitored to estimate the water used to wash six different categories of vehicles. Composite wastewater samples from three carwash stations were analysed for concentrations of different contaminants which were used to compute pollution loads. Using R software, one-way ANOVA with Tukey's (HSD) post-hoc testing and 2-sample t-test at 95% confidence interval were employed to test statistical differences. After an 8-week monitoring campaign involving 3,667 vehicles, the study showed that average water used for each vehicle type were in the order: Motorbike - 97L (95% CI: 90-103L); Salon car - 158L (95% CI: 154-161L); SUV - 197L (95% CI:191-203L); Buses/Coaches - 370L (95%CI:351-381L); Articulated truck 1,139L (95% CI:916-1,363L); Graders/Loaders - 1405L (95% CI:327-2,483L). Overall, the carwash industry in the Metropolis uses about 1000m³ of freshwater daily and discharges the resulting wastewater into waterways untreated. The wastewater has a low Biodegradability Index (0.3-0.4) and is characterized by a mildly alkali pH (7.6-8.6) with high levels of Sulphates (40.8-69.8 mg/L), COD (990-1413 mg/L), TSS (1260-3417 mg/L) and E. coli (2.3-4.7 × 10³ CFU/100mL). Pollution loads of BOD and COD were up to 2tons/year and 6tons/year respectively. Stipulated effluent discharge guideline values were mostly exceeded - in some cases by up to 68 times. To avert the unbridled wastage of freshwater, the study recommends enforcement of wastewater recycling for all carwash stations and promulgation of a tax system that rewards stations that recycle wastewater and surchages those wasting freshwater.

Retrofitting ancient timber glulam mortise & tenon construction joints through computer-aided laser cutting

This study is aimed to rationalise and demonstrate the efficacy of utilising laser cutting technique in the fabrication of glulam mortise & tenon joints in timber frame. Trial-and-error experiments aided by laser cutter were conducted to produce 3D timber mortise & tenon joints models. The two main instruments used were 3D modelling software and the laser cutter TH 1390/6090. Plywood was chosen because it could produce smooth and accurate cut edges whereby the surface could remain crack-free, and it could increase stability due to its laminated nature. Google SketchUp was used for modelling and Laser CAD v7.52 was used to transfer the 3D models to the laser cutter because it is compatible with AI, BMP, PLT, DXF and DST templates. Four models were designed and fabricated in which the trial-and-error experiments proved laser cutting could speed up the manufacturing process with superb quality and high uniformity. Precision laser cutting supports easy automation, produces small heat-affected zone, minimises deformity, relatively quiet and produces low amount of waste. The LaserCAD could not process 3D images directly but needed 2D images to be transferred, so layering and unfolding works were therefore needed. This study revealed a significant potential of rapid manufacturability of mortise & tenon joints with high-quality and high-uniformity through computer-aided laser cutting technique for wide applications in the built environment.

Tung oil as an effective modifier for sulfur polymer cement and its performance in galvanic waste encapsulation

The data on the performance of sulfur polymer cement crosslinked with tung oil polymerization modifier are presented. Specimens of sulfur polymer cement (SPC) were prepared with different doses of tung oil in amounts of up to 8.85% of the sulfur mass. The obtained SPCs were used as binders to encapsulate two galvanic wastes differing in their toxic metal composition: waste I and waste II with loadings of approximately 25 and 50% of the composites' mass, respectively. For comparative purposes, appropriate samples of the SPCs and their composites with galvanic wastes were obtained using very similar doses of dicyclopentadiene sulfur modifier. Waste II was also encapsulated using SPC, in which a mixture of tung oil and dicyclopentadiene in a 1:1 weight ratio was used as the modifier. Crosslinking of the tung oil to the SPC matrix was assessed by FT-IR. The obtained SPCs and their composites with galvanic wastes were characterized by SEM and tested for water sorption capacity, compressive strength and metal leaching toxicity using TCLP and EN standards. The effectiveness of the tung oil binding to the SPC network was evidenced by the complete disappearance of methine C–H stretching vibrations at 3010 cm⁻¹ and the double bond –C=C– wagging vibrations at 990 cm⁻¹ in the FT-IR spectrum after processing with sulfur. SEM observations revealed that all the specimens prepared with dicyclopentadiene had a glassy-like fracture surface and also showed fewer cavities and defects in cements and composites when compared to their counterparts prepared with tung oil. The water sorption capacities of all the specimens were below 1%, where the values of those prepared with the tung oil were two to three fold higher than the values of their counterparts prepared with dicyclopentadiene. The pH of the TCLP leachates was in the range of 2.75–2.98, and a decreasing trend in the pH value was found with an increasing modifier dose. The TCLP leachate pH from the waste I monoliths with dicyclopentadiene were generally lower by 0.1–0.35 when compared to the corresponding monoliths with tung oil. The toxic metals immobilization order revealed from the TCLP test (leachate pH around 2.85) is Cd > Sr ≥ Zn > Cu > Ni > Cr > Pb, while the resulting order from the EN test, due to a higher leachate pH of about 5.9, follows Cd > Pb > Zn > Cu ≥ Ni > Sr > Cr. An increased tung oil dose from 2 to 8.85% enhanced the SPC compressive strength by three to four fold, while the same increase of the dicyclopentadiene dose led to an increase of this parameter for less than two fold. The addition of galvanic wastes to the SPCs resulted in a further increase in compressive strength for the corresponding SPC samples.

Numerical study on failure process and ultimate state of steel bearing under combined load

The limit state and deformation performance of steel bearing under seismic load is one of the most critical points to consider the effective or rational design of bridge against strong ground motion. In the 2016 Kumamoto earthquake, various bridges are damaged by the earthquake. Among the components of the bridge, steel bearings are the most damaged part of the bridge, which affects the functionality of the entire bridge. Since the 1995 Southern Hyogo Prefecture Earthquake, several studies about the ultimate state of steel bearing during earthquake carried out. However, there are a few studies on analyzing the failure processes and ultimate state of steel bearing when various loads assumed at the time of the earthquake. Therefore, the study investigates the failure process and ultimate state of pin bearing and pin-roller bearing under combined load using static push-over analysis. First, the bridge axis and perpendicular bridge axis horizontal loading directions proposed depending on the actual earthquake directional behavior of the bridge. Then the analysis of each bearing conducted and clarified the failure process of each bearing that leads to failure based on the von mises stress yield criteria. Three-dimensional finite element method used to analyze the bearings. The analysis result found that set bolt and pin neck tensile failure were the probable failure mode of pin bearing, and failure mode of pin-roller bearing depends on vertical and horizontal loading direction. In the future, the result used to propose a new seismic resistance design and reinforcement method of bearings that satisfies the required performance.

Preparation, characterization, and evaluation of compressive strength of polypropylene fiber reinforced geopolymer mortars

The study of the fiber-matrix interface represents a crucial topic to determine the mechanical performance of geopolymer-based materials reinforced with polypropylene fibers (PPF). This research proposes the use of natural zeolite in the preparation geopolymers mortars through alkaline activation with NaOH, Ca(OH)₂ and Na₂SiO₃, and with river sand as a fine aggregate. PPF were incorporated into the geopolymer-based mortar matrix in different proportions like 0, 0.5, and 1 wt.%. The mortars were cured for 24 h at 60 °C and then aged for six days more at room temperature. All samples analyzed through compressive strength were also characterized by X-ray diffraction, thermal analysis, Infrared Spectroscopy, and scanning electron microscopy techniques. The results indicated that the best mix design among the ones used: NaOH (10 M), Na₂SiO₃/NaOH = 3, Ca(OH)₂ = 1.5 wt.% and PPF = 0.5 wt.%. The optimum mix design showed a compressive strength of 4.63 MPa on average. Besides, the fibers enhanced the compressive strength of those samples which the PP fibers probably have better dispersion inside the matrix of the geopolymer mortar.

The potential of industrial waste: using foundry sand with fly ash and electric arc furnace slag for geopolymer brick production

The purpose of this study was to investigate the best ratio of waste foundry sand (WFS), fly ash (FA), and electric arc furnace slag (EAF slag) for the production of geopolymer bricks. In this research study, WFS, FA, and EAF slag were mixed at the ratio of 70:30:0, 60:30:10, 50:30:20, and 40:30:30 with 8M sodium hydroxide (NaOH) and 98% purity sodium silicate (Na₂SiO₃) with a ratio of Na₂SiO₃/8M NaOH = 2.5. The mixtures were compacted in 5 cm × 5 cm x 5 cm molds and cured at an ambient temperature for 28 days. Then, their compressive strength was analyzed. The results showed that the geopolymer bricks with the highest compressive strength were those mixed at the 40:30:30 ratio, with a compressive strength of 25.76 MPa. The strongest bricks were also analyzed using the leaching test to ensure the production involved non-hazardous materials. To compare the environmental impacts of geopolymer bricks and concrete bricks, their effects on climate change, ozone depletion, terrestrial acidification, human toxicity, terrestrial ecotoxicity, and fossil fuel depletion were examined from cradle to grave using SimaPro 8.0.5.13 software. The results of the life cycle assessment (LCA) from cradle to grave showed that the environmental impact of geopolymer brick production was lower in every aspect than that of concrete production. Therefore, geopolymer brick production can reduce environmental impact and can be a value-added use for industrial waste.

Relationships among compressive strength and UPV of concrete reinforced with different types of fibers

This paper determines the effect of steel, glass, and nylon fibers on the compressive strength and ultrasonic pulse velocity (UPV) of fiber reinforced concrete. The influence of different fiber types, fiber volume fraction, and water to cement ratios on the compressive strength of fiber reinforced concrete was tested using the compression test machine (CTM) and ultrasonic pulse velocity tester. Experiments were carried out at different ages on more than 100 cylindrical specimens. A comparison between the experimental results and equations available in the literature for prediction of compressive strength in terms of UPV was conducted to better evaluate the accuracy of available methods, when the type and volume fraction of fibers change. A new empirical equation that accounts for the presence of different types of fibers and fiber volume fraction is proposed to better estimate the compressive strength of steel, glass, and nylon fiber reinforced concrete.

Study of sweetened seawater transportation by temperature difference

This study evaluates the vapor transportation by transmission pipelines during seawater desalination. This study seeks to reach a high rate of water transportation during desalination. Hence, the results obtained from this research are closer to reality than other analyses. Other benefits of this research include increasing efficiency, studying the element-to-element transmission, and considering flow as a compression case. The water desalination system comprises three parts of evaporation, transportation, and condensation. In the transportation part, equations of continuity, momentum, and energy are implemented, and the temperature of the vapor is calculated at the beginning of the condensation pipe. Other achievements of this study include the division of transportation lines to small elements and the implementation of vapor condensation in transportation lines. This study used pipelines with diameters of 1, 2, and 4 m to transmit vapor to Ramsar city and the heights of Takhte Soleiman, 16 km away from the city with the elevation of 2000 m. The results show that diameter, transportation length, and temperature differences are, respectively, the most influential factors on the efficiency of sub-atmospheric vapor transportation. The outcomes of this study were presented as the outflow of condensed water at the destination. Considering the margin of safety in calculations, it was scientifically proved that the results obtained in this study were approximately 10% more than results derived from other studies in the literature that are based on the incompressibility of fluids.

Investigating the expansion characteristics of geopolymer cement samples in a water bath and compared with the expansion of ASTM Class-G cement

In selecting the binder composition for oil well application, its stability is an important design parameter. This paper presents the results of an experimental study conducted for comparing the linear expansion characteristics of geopolymer cement with the traditionally used ASTM Class G cement system. The expansion test was done in a water bath at 60 °C subjected to different curing intervals. The linear expansion of a cement system defines as the dimensional changes occur in the system, which is sometimes required to avoid the cement shrinkage during the hydration phase. In the case when the desired level of expansion is not achieved in the system, then the commercially available expandable materials are added in the class G cement system that enables the system to expand to the desired level. Shrinkage in the cementing system causes the formation of a microannulus or induces a gap that may allow the migration of fluid, hence the integrity of the system could be lost. This experimental study has revealed that the geopolymer cement tends to expand 0.15%–0.2% without the addition of any admixture, whereas the ASTM Class G cement has shown a lower value of linear expansion, which was obtained less than 0.1% after 18 days of curing. In the case of Class G cement, the addition of expandable material helped to increase the expansion; in the case of a geopolymer system, the additive has further accelerated the expansion.

Improving the characteristics of dispersive subgrade soils using lime

Dispersive soil arises significant problems that need attention in geotechnical Engineering. Such soils are easily erodible and keep apart due to the difference in moisture content and exchangeable sodium. This study focuses on enhancing sub-grade of the road by stabilizing dispersive soil with lime, and it provides better index properties, reduces dispersivity, increases Unconfined compression strength, and California Bearing Ratio value with an increasing lime quantity and curing in different test conditions. The effective lime content should be 7% to 9 % of dry soil weight as it provides high strength and quality of subgrade pavement rating.

Effect of cations and anions on flocculation of dispersive clayey soils

Dispersivity of clay soils is one of the most important issues that should be considered in civil engineering projects. Dispersive soils are clay soils that are easily washed in water with low concentrations of salt; these clay soils usually contain high levels of sodium ions in their adsorption cation sites. Kaolin, sepiolite (fibrous clay), and bentonite soils are among the most important and useful industrial materials. Therefore, in this study, these three clay soils were selected to investigate dispersivity potential by adding 4% of dispersive materials (Sodium hexametaphosphate) and performing shear strength, crumb, double hydrometer, pinhole tests, and chemical experiments. Results indicated a change in the Sodium Adsorption Ratio (SAR) in the following order: kaolin > sepiolite > bentonite. Stabilization practices using chemical methods were done after performing soil divergence with sodium hexametaphosphate. CaCl₂, CaSO₄, AlCl₃, and Al₂ (SO₄)₃ were used for chemical stabilization to assess the effect of ion valence on soil improvement parameters. Results obtained for chemical properties showed that, stabilization potential was in the following order: kaolin > sepiolite > bentonite; meaning that clay soils with lower cation exchange capacity have more remediation potential and are more susceptible to dispersion. The role of calcium and aluminum cations was prominent in improving mechanical and dispersivity properties, respectively. In general, further dispersion potential of clays in the same Na⁺ concentration was found to be related to a decrease in the cation exchange capacity, specific surface area, and plastic index. Soil dispersion was directly associated with diffuse double layer and electrostatic forces while; soil strength parameters were mainly dependent on cementation and connection of soil particles to each other. Consequently, it was observed that, clay soils with suitable engineering properties (higher strength and compaction or lower Atterberg limits) are more sensitive to dispersion compared to other types of clay with higher CEC and plasticity values.

Durability of self-consolidating concrete containing natural waste perlite powders

Perlite is a natural glassy volcanic rock used in construction applications requiring improved lightweight, thermal, and acoustic properties. During processing of raw perlite (i.e., cutting and fractioning to different sizes), large amounts of powders are collected and stored as waste materials. This paper evaluates the effect of waste perlite (WP) powders on durability and long-term transport properties of self-consolidating concrete (SCC). Different mixtures prepared with 580 kg/m³ powder using various combinations of WP, limestone filler (LF), metakaolin (MK), and silica fume (SF) are tested over 2-years period. Test results showed that WP confers particular benefits to the SCC compressive strength and its evolution over time, particularly when used in combination with MK and SF. Water permeability, carbonation, and chloride ion migration curtailed when WP concentration reached 220 and 260 kg/m³. In contrast, the resistance against freeze/thaw remarkably improved, given the pozzolanic reactions and porous nature of such powders that accommodated the disruptive expansive stresses resulting from frost attack.