Showing papers in "Innovative Infrastructure Solutions in 2020"

Emergency remote teaching during Coronavirus pandemic: the current trend and future directive at Middle East College Oman

Abstract: Due to COVID-19 outbreaks worldwide, the academic institutions have been enforced to entirely cancel face-to-face teaching including laboratories and other learning experiences as a mitigation step against the risk posed by the Coronavirus. Accordingly, various measures by the higher education providers have been initiated to implement social isolation strategies, and online teaching is followed with rapid curriculum transformation. The online delivery is more convenient, as it can provide vibrant and dynamic teaching and learning environment. However, due to time constraint, the curriculum transformation is anticipated to occur rapidly without sufficient preparation. Therefore, in this study, the concept of the emergency remote teaching (ERT) including its application and evaluation is thoroughly discussed. The application of the ERT in the Middle East College Oman has been considered as case study. This study draws on CIPP evaluation model to assess the effectiveness of the adopted model, and qualitative data were collected online taking random samples of students and educators. Besides, interview and questionnaire responses, experiences, beliefs, and challenges encountered by the educators and students on the emergency remote teaching were used and analyzed. In addition, students’ weekly attendance segregated with session modes, levels and module nature were considered to evaluate the students’ participation to the online classes. The collected information were analyzed, and based on the analysis outcomes, recommendations were forwarded to serve as an input for future strategies and policies and to improve the performance of teaching learning activities during similar circumstances.

Structural reliability software and calculation tools: a review

Abstract: Structural reliability is now the leading method in the field of design optimization and assessment of civil engineering structures since it offers a rational treatment of the uncertainties in this kind of studies. However, structural reliability problems become more complex with time due to the high number of random variables leading to very complex numerical problems; moreover, they have to deal with complex finite element structural models. So, many reliability calculation tools and software packages have been developed for this purpose. This paper is an important reference for researchers and engineers to help them select the most suitable reliability calculation tool or software package; they will also know their most common area of use through the application examples mentioned for each tool. Several criteria are taken into account in the investigation such as the type of the structure, the probabilistic computational methods, and the budget assigned to the calculation tool.

Artificial neural network back-calculation of flexible pavements with sensitivity analysis using Garson’s and connection weights algorithms

Abstract: The primary objective of this research was to develop a model to accurately predict the modulus of flexible pavement layers from surface deflections measured using the falling weight deflectometer (FWD) device To do so, a synthetic dataset consisting of 10,000 flexible pavements was created using the layered elastic theory The developed dataset contained the moduli values for different pavement sections, and deflections at known distances from the load center Next, the moduli of different asphalt pavement layers consisting of a surface course, base course, and subgrade were calculated using the Artificial Neural Network (ANN) methodology through backcalculation The inputs for the neural network are thicknesses and deflection values at seven distances from the load center The outputs are the moduli for different layers The optimum neural network consists of two hidden layers and has a general architecture of 9-36-18-3 The transfer function is sigmoid for hidden layers and linear for the output layer Results indicate that the ANN model can predict the modulus of different layers accurately with a coefficient of determination (R2) of more than 0999 in all cases For validation, the results from the developed model were compared with typical backcalculation software of ISSEM4, MODCOMP, MODULUS, WESDEF, and BAKFAA as well as 386 LTPP sections Moreover, an analysis was conducted to assess the contribution of inputs in moduli prediction for each of the pavement layers using the Garson algorithm and the Connection Weight methods It was concluded that the results from the latter method are in better agreement with the theories Finally, the significance of different input variables was assessed using an indirect method by excluding each from the analysis and checking of the model predictability power It was concluded that in order of significance, the base layer thickness, 1st geophone deflection, and the AC layer thickness are the variables that their exclusion causes large errors

Influence of structural parameters on the properties of fibred-foamed concrete

Abstract: The demand for novel technology for manufacturing lightweight concrete has increased in the global construction industry. Therefore, studies that explore alternative lightweight concrete systems for structural applications are urgently needed. The objective of this study is to develop structural fibred-foamed concrete (SFFC) by the addition of polypropylene (PP) fibre, fly ash (FA), and silica fume (SF). Foamed concrete (FC) was obtained by replacing sand with FA. The properties of the FC were enhanced with PP fibre and fine SF. SFFC with dissimilar densities of FC (1000, 1300, 1600, and 1900 kg/m3) is essential for examining compressive, flexural, and splitting tensile strengths, drying shrinkage, and creep. The FC with a density of 1000–1900 kg/m3 and compressive and splitting tensile strengths of 10–70 MPa and 1.1–4.81 MPa, respectively, have been made by the addition of PP fibre and fine SF. Fine SF and PP fibre considerably improved the hardened strength of the FC. Additionally, the inclusion of PP fibre significantly enhanced the tensile strength and increased the creep resistance and drying shrinkage. Therefore, SFFC can be used as a substitute lightweight concrete material for the production of structural concrete applications in the construction industries today.

Numerical analysis and preliminary design of topside of an offshore platform using FGM and X52 steel under special loads

Abstract: This study investigates the behavior of the topside of an offshore platform under hydrocarbon explosion and wind. Topside is designed for a combination of loads arising from types of equipment, fixed and rotating machinery, and cranes, apart from the gravity loads. While the wind loads are calculated using a gust factor and applied at different levels of the deck, a preliminary analysis is carried out using SAP2000 nonlinear. The design check carried following the code confirmed that the chosen sections satisfy the design requirements, both in strength and serviceability criteria. The topside of a typical offshore platform is highly vulnerable to fire and hydrocarbon explosion, causing extreme pressure and temperature in the confined areas. Pressure caused by the hydrocarbon explosion is rapid and results in an impulsive force of short duration. It damages the structural components and affects the overall performance of the topside considerably. The blast load is applied as an overpressure on the beams and columns and analyzed using ABAQUS explicit. The current study investigates the structural adequacy of members, constructed with X52 steel and functionally graded material (FGM). A comparison of the results showed that FGM offers more resistance to the displacement of beams and columns. Under the action of blast overpressure, members with FGM showed a significant reduction in both the plastic stain and Von-Mises stress at the beam–column connections in comparison with that of X52 steel.

Characterization studies on coal gangue for sustainable geotechnics

Abstract: Global rise in greenhouse gas emissions (GHG) is triggered mainly due to the consumption of fossil fuels for power generation and domestic usage. Among the fossil fuels, coal is a primary contributor to global GHG with substantial emissions generated during its mining and combustion process. Coal gangue, a residue produced during the coal mining process, has found sparse utilization in civil engineering applications. To gauge the feasibility of using coal gangue for geotechnical and geoenvironmental applications, comprehensive characterization study was performed which include understanding the geotechnical, mineralogical, chemical and leaching behavior. Further, to evaluate the environmental impacts associated with coal gangue utilization, carbon footprint assessment (CFA) was performed. The geotechnical properties of coal gangue revealed its potential as fill material in the construction of embankments and retaining walls. Mineralogical and chemical characteristics of coal gangue are comparable to coal combustion residues like coal ash and fly ash which are widely used in bulk civil engineering applications. The leaching studies revealed the presence of trace elements in coal gangue; however, their concentration levels were found to be well below permissible limits. The CFA has shown that utilization of coal gangue in mechanically stabilized earth wall construction resulted in a net savings of 1709 CO2 (kg) emissions. Based on the characterization studies, it can be inferred that coal gangue is a potential alternative to the existing conventional geomaterials like soils and other recycled materials.

Utilization of industrial waste—based geopolymers as a soil stabilizer—a review

Abstract: Ordinary Portland cement (OPC) and lime (L) are widely used in the soft and weak soil stabilization. Various studies have suggested that the production of cement produces high amount of CO2 gas which is mainly responsible for global warming. An alternative to OPC and L are geopolymers which are less costly, have high strength and durability and produces lesser CO2 in comparison with OPC and L. Moreover, the production of a geopolymer consumes less energy. This review paper focuses on the studies about the utilization of industrial waste-based geopolymers as a soil stabilizer. In this review, only the geopolymers derived from industrial solid waste have been considered. Effects of different parameters of geopolymers such as different percentage mixes (%), molarity (M), temperature (T), curing time (days), alkaline activator ratio (AA) and water/binder (w/b) ratio on the geotechnical properties of soil have been discussed. Further, effects of morphological and microstructural behavior of geopolymers on the geotechnical properties of soil have also been discussed. In this review, it has been found that 5–20% mixing of geopolymer, 8–12 M molarity, 25–45 °C T, 7–28 days of curing, 1.5–2.5 AA ratio and 0.35–0.85 w/b ratio are the optimal range of parameters of geopolymer which gives a significant improvement in the geotechnical properties of soil. Further, morphological and microstructural analysis studies show that the formation of C–S–H gel, silicate, calcite and aluminate compounds are mainly responsible for the improvement in the geotechnical properties of soil. The soil stabilized using industrial waste-based geopolymers have potential applications in the ground improvement, subbase and base course of flexible pavements. Moreover, this soil stabilization technique not only utilizes the industrial solid waste in a more purposeful manner but also is very cost-effective and eco-friendly.

A comparative study of various hybrid neural networks and regression analysis to predict unconfined compressive strength of travertine

Abstract: In this paper, the relationships between engineering properties of travertine rock samples including uniaxial compressive strength, density, Brazilian tensile strength and compressional and shear wave velocities were evaluated. The Bukan travertine mine located in Iran was considered as case study here. Various data analysis approaches including simple regression method, multiple regression method and artificial neural network (ANN) have been used for finding optimum estimation model for uniaxial compression strength of travertine rocks. Rock sample preparations difficulties and conducting expensive tests such as UCS motivated many researchers to study different regression methods to estimate UCS from other rock mechanic tests. In this paper, different statistical methods as well as some ANN optimization algorithms that were used by several researchers are compared to find the optimum solution for UCS estimation problem of travertine rock samples. These optimization tools comprising genetic algorithm, particle swarm optimization and imperialist competitive algorithm were applied to improve the efficiency of ANN analysis. Finally, after comparing all of the presented methods, the best results were obtained by ANN-PSO algorithm.

An experimental-based python programming for structural health monitoring of non-engineered RC frame

Abstract: Most of the damages were experienced on the buildings which were conventionally built without any consideration of IS codal provisions conveniently called non-engineered structures. Non-engineered structures are frequently affected by vibrations due to various natural and artificial sources. Thus, it needs special attention. It is, therefore, necessary to check the performance of non-engineered structures through various health monitoring techniques. A piezoelectric-ceramic (PZT) sensor-based technique called electromechanical impedance (EMI), in which the sensors efficiently operate at a high-frequency range and can typically detect damage at the initial level which is implemented for the purpose. In this research work, experimental tests are performed on the non-engineered reinforced concrete frame using EMI technique by utilizing a PZT sensor which is bonded to the structure using the high-strength epoxy adhesive. The experiment is carried out to identify and locate the damages using frequency variations, and the severity was checked using extracted equivalent parameter; damage index. Second, a Python programming is developed by the authors to identify and quantify the damage index and root mean square deviation index in the frame. The frequency responses obtained from the experimental tests are used in the programming. The performance of the program is compared with the experimentally calculated parameters to check the efficiency of the programming. According to the results of the comparison, it is observed that python programming can be effectively used for damage detection.

Strength characterization of concrete using industrial waste as cement replacing materials for rigid pavement

Abstract: The excessive use of cement in the construction industry has caused many undesirable consequences. Replacement of cement with industrial by-products like fly ash (FA), ground granulated blast furnace slag (GGBFS), silica fume (SF), metakaolin, rice husk ash, etc., as the mineral admixtures offers several advantages in this modern era of sustainability in construction practice. This paper presents the experimental investigations for assessing the strength properties of the concrete made using the pozzolanic waste materials, i.e. supplementary cementitious materials (SCMs) such as FA, GGBFS and SF as the cement replacing materials. Eight trial mixes were prepared using these materials with varying amount of ordinary Portland cement. These SCMs were kept in equal proportions in all the eight trial mixes. Moreover, superplasticizer was also used for bringing improvement in the workability. The compressive strengths corresponding to the curing period of 7, 28, 40 and 90 days along with the flexural and indirect tensile strengths corresponding to 7, 28 and 40 days curing were evaluated. The study concludes that industrial waste materials can be used as partial replacement of cement and can render sustainable concrete for use in the rigid pavement construction.

Effectiveness of Pongamia pinnata oil as rejuvenator for higher utilization of reclaimed asphalt (RAP) material

Abstract: An increasing trend in utilization of the reclaimed asphalt pavement (RAP) for pavement recycling is being noticed due to its cost-effectiveness and environmental sustainability. Most of the studies recommend to add RAP only up to 30% except a few which recommends up to 50% based on the convenience in field application. However, there is a scope for higher RAP utilization through the addition of rejuvenators or recycling agents. In this study, a non-edible oil (i.e. Pongamia oil) obtained from Pongamia pinnata was used as a rejuvenator for design of recycled hot mix asphalt (HMA) with higher RAP content. Rheological tests revealed that about 5% dosage of the rejuvenator is adequate to meet the performance in terms of rutting and fatigue cracking. The rejuvenated binder was found to be thermostatically stable when exposed to temperature up to 230 °C as observed from thermogravimetric analysis (TGA). The performance of the HMA containing a varying percentage of RAP (30% to 70%) with the addition of a softer binder and with the addition of rejuvenator was studied or compared in terms of volumetric properties, indirect tensile strength (ITS), moisture sensitivity, resilient modulus, rutting and intermediate temperature cracking. Results indicate that by adding the Pongamia oil as a rejuvenator, RAP up to 60% may be used in the production of HMA without affecting the performance significantly.

Column repair and strengthening using RC jacketing: a brief state-of-the-art review

Abstract: Seismic retrofitting and/or the strengthening of RC columns has been a popular area of research for decades. Currently, reinforced concrete jacketing is considered as the most common technique for repairing and strengthening of deficient and/or damaged RC columns. In general, this technique is a practical solution to recover and improve the load-carrying capacity and stiffness of reinforced concrete columns in earthquake-prone countries. It is a simple method that can be applied to any column cross section for rehabilitating structural elements by encasing the old member in a stiff jacket. The importance of this approach comes from its ability to improve the load-carrying capacity, strength, and stiffness of any column section significantly without the need for experienced labor or complicated installations process. This paper summarizes and compares general conclusions of recent investigations on columns retrofitting using reinforced concrete jacketing. As a part of this study, experimental, analytical, and numerical studies were reviewed and their findings were collected and discussed.

Characteristic Evaluation of Geopolymer Concrete for the Development of Road Network: Sustainable Infrastructure

Abstract: A large quantity of the rural roads in the world has been connected with all traditional concrete roads and has a low volume of traffic. The common problem for such kinds of roads is sustainability and durability. Geopolymer concrete (GC) roads offer an alternate to the traditional cement-based concrete roads. An acceleratory pavement track (APT) with six segments has been constructed to evaluate the practical approaches of fly ash-ground granulated blast furnace slag (GGBFS)-based GC in the sustainable development of rural road network. This paper presents the non-destructive testing (NDT) on APT to check the quality of GC. Moreover, the mechanical, microstructural, and durability characteristics have been analyzed on samples prepared at the time of APT construction. In this paper, efforts have been made to elaborate on the corrosion resistance and chloride resistance of GC after 28 days of ambient curing. The highest compressive strength of 56.63 MPa was obtained for mix with 70% FA, 30% GGBFS, and 0.4 S/B ratio sample after 28 days of ambient curing, and this value is strengthened by rebound hammer result, i.e., 55.7 MPa, conducted on APT without load revolution. The increase in the number of load repetitions on APT found a decrease in rebound and ultrasonic pulse velocity values. Geopolymer concrete mix with 30% GGBFS attained superior NDT behavior upon load repetitions on APT, and similar improved characteristics were identified on laboratory-based testing.

Properties of eco-friendly pervious concrete containing polystyrene aggregates reinforced with waste PET fibers

Abstract: A huge amount of expanded polystyrene (EPS) and PET plastics are produced every year all around the world. However, if not treated properly, after their consumption, EPS and PET caused numerous environmental problems. Therefore, the utilization of these wastes in concrete production can contribute to the sustainability of construction materials. This experimental study aims to investigate the behavior and properties of pervious concrete incorporating both EPS aggregates and waste PET fibers. A total of ten concrete mixtures were designed with different percentages of PET fibers and the same amount of EPS content. The investigated parameters included: abrasion resistance, dry density, compression as well as flexural strength, porosity ratio and water permeability coefficient. From the results obtained in this study, it has been shown that the proposed mixes are reliable to use in the construction field. The compressive strength, abrasion resistance and density decreased by incorporating EPS and PET fibers. However, the flexural strength increased by using PET fibers up to 1% in volume. On the other hand, the porosity ratio and the water permeability coefficient increased through the addition of PET fiber. The empirical models among different properties were also provided. This experimental study can be contributed to promote sustainable construction materials as mixtures contained a considerable amount of waste materials.

Multi-input performance prediction models for flexible pavements using LTPP database

Abstract: Pavement performance prediction is a primary concern for pavement researchers and practitioners. The impact of climatic conditions and traffic characteristics on pavement performance is indisputable. The main objective of this study is to investigate the combined effect of both climate and traffic loading on pavement performance. Multi-input performance prediction models in terms of the well-known Pavement Condition Index (PCI) are proposed. The Long-Term Pavement Performance (LTPP) database is used for the models development and validation. Data from 89 LTPP sections including 617 observations from the Specific Pavement Studies (SPS-1) with no maintenance activities are collected. These data cover the four climatic zones (wet, wet freeze, dry, and dry freeze) in the USA, different pavement structures, and different levels of traffic loading. Based on these data, PCI prediction models are developed using two modeling approaches: multiple linear regression analysis and artificial neural networks (ANNs). The proposed models predict the PCI as a function of climatic factors, namely average annual temperature, standard deviation of monthly temperature, precipitation, wind speed, freezing index, total pavement thickness, and weighted plasticity index. Additionally, traffic loading, expressed in terms of the classical equivalent single-axle loads, is considered. The regression model yielded a coefficient of determination (R2) value of 0.80, whereas the ANNs model results in a relatively higher R2 value of 0.88. The proposed models are not only simple and accurate; they also have the potentials of being adopted in countries experiencing similar climatic conditions and traffic loading.

Influence of nanomaterial on high-volume fly ash concrete: a statistical approach

Abstract: This work is focused on the mechanical properties of ternary blended nanoconcrete replacing cement with fly ash and nanosilica in the optimized percentage. Ternary blended nanoconcrete mix is designed with 0.45 water-to-binder ratio and 438 kg/m3 of cementitious content in all mixtures with a combination of various percentages of nanosilica and 40% of fly ash by weight of cement. The mechanical properties like compressive, split tensile and flexural strength tests at the age of 7, 14 and 28 days are performed. With the addition of nanosilica, the enhancement was observed in all mechanical properties, but when the dosage of nanosilica was more than optimum, bleeding as well as segregation in concrete was observed. Response surface method was used in predicting the values of compressive strength in this work, which was found to be in agreement with the experimental observations with at least 95% confidence levels.

The use of soil bioengineering to overcome erosion problems in a pipeline river crossing in South America

Abstract: Exposed pipelines are susceptible to geotechnical–hydraulic phenomena and to a high-risk level of failures caused by scouring or erosive processes in the river bed and river banks. Currently, in the prevention, maintenance, or remediation of river crossings, traditional engineering techniques are generally applied, which often leads to insufficient solutions concerning technical, financial, and environmental issues. The soil bioengineering methods, using vegetation in combination with inert materials for soil stabilization and protection against erosion, can be an alternative, a complementary tool, or even a substitute for traditional engineering practice. In this context, this work aims to present one case study of an exposed pipeline in which were used some soil bioengineering approaches to prevent natural erosion processes at pipeline river crossings. Compared to conventional methods, the soil bioengineering techniques used in the presented case study have proved to be advantageous in economic, environmental, and aesthetic aspects.

Evaluation of the accuracy of commonly used empirical correlations in predicting the compression index of Iraqi fine-grained soils

Abstract: Several empirical correlations were proposed in the literature to predict the compression index of fine-grained soils using either of the soil properties such as the liquid limit, plasticity index, initial void ratio and natural moisture content. However, the accuracy of these correlations to predict the compression index of Iraqi fine-grained soils has not been investigated before. Hence, this research has been carried out to evaluate the effectiveness of the available correlations in predicting the compression index of fine-grained soils collected from different regions in Iraq. A methodology, based on statistical analysis, has been employed to analyse the differences between predicted and measured compression index values. In addition, a database of properties of fine-grained soils has been collected from the literature to enable the statistical assessment. The results showed a significant scatter in the prediction among the examined correlations, where most of the correlations performed poorly in the predictions. However, it has been shown that the correlations proposed by Rendon-Herrero (J Geotech Eng 109(5):755–761, 1983) and Al-Khafaji and Andersland (J Geotech Eng 118(1):148–153, 1992) provided a good estimate of the compression index compared with other empirical correlations.

COVID-19 from mysterious enemy to an environmental detection process: a critical review

Abstract: The recent global emergence of an unusual viral pneumonia of COVID-19 epidemic was firstly started in Wuhan city, Hubei province in China in December 2019. Regrettably, it is still sweeping the planet, and it cannot be controlled up till now. By May 2020, the unexpected spread of this disaster had caused more than 3,759,967 cases and 259,474 deaths in 114 countries from Asia to the Middle East, Europe, and the USA. Considering its fatal nature, it has evolved as a major challenge for the world. This is necessitating a quick and steep intervention in order to save millions of people’s lives across the globe. The knowledge about the nature and evolution of the COVID-19 virus in water, soils, and other environmental compartments can be addressed through wastewater and sewage. Wastewater-based epidemiology approach can be used as an early indicator of the infection within a specific population. The basic aim of this review article is trying to provide a prompt, and valuable reference guides about COVID-19. Some important questions were addressed, such as, its origin, transmission, clinical symptoms, diagnosis, environmental aspects, and the possible indoors and outdoors airborne transmission minimization strategies that may benefit specialists.

The COVID-19 pandemic: biological evolution, treatment options and consequences

Abstract: The spread of novel coronavirus SARS-CoV-2, the cause of the pandemic COVID-19 has emerged as a global matter of concern in the last couple of months. It has rapidly spread around the globe, which initially began in the city of Wuhan, People’s Republic of China and is hypothesized to originate from the group of Rhinolophus bats. Till date, there has been no clinically proven vaccine against the SARS-CoV-2 and thus the doctors are employing the other well-known techniques, which have previously successfully tackled similar other human coronaviruses. To prevent the further spread of COVID-19, doctors are advising isolation of the infected patients, and also regular washing of hands and the use of face mask for the common people. In the wake of the COVID-19 outbreak, the countries are going for nationwide lockdown as the only preventive measure to avert community transmission of this disease, which is having economic, social and psychological effect on the general mass. Therefore, this comprehensive review article encapsulates the biological evolution of human coronaviruses, probable treatment and control strategies to combat COVID-19 and, its impact on human life.

Influence of recycled concrete aggregates and blended cements on the mechanical properties of pervious concrete

Abstract: The paper presents the results of an investigation conducted to study the strength properties of pervious concrete containing coarse recycled concrete aggregates (RCA) In this study, 13 pervious concrete mixes were prepared with the use of RCA replacing coarse natural aggregates (NA) by 0, 25, 50, 75 and 100% Keeping the water–cement (w/c) ratio constant, Viscosity Modified Agent (VMA) was added at 08% by weight of binder content Being environmentally advantageous, 30% Fly Ash (FA) has been added with 70% Ordinary Portland Cement (PC) in the binder of control mix Despite being environmentally safe product, metakaolin (MK) also tends to enhance the properties of concrete containing RCA Therefore, keeping the PC content 70% for all mixes, FA was replaced with MK at two different levels of 5% and 10% to improve the properties of pervious concrete made with RCA Specimens in the form of cubes, cylinders and beams were prepared for studying the mechanical properties at different ages of curing The test results showed that there was significant loss in compressive, splitting tensile and flexural strength of pervious concrete while increasing the percentage of RCA replacing NA Addition of 5% MK compensated the decrement noticed in the strength properties after replacement of NA with RCA The mix with 25% RCA and 5% MK was having almost same compressive strength as that of reference mix 10% MK further enhanced the strength properties and it was concluded that loss of compressive strength in pervious concrete due to addition of 50% RCA can be compensated by the addition of 10% MK

Microbial geo-technology in ground improvement techniques: a comprehensive review

Abstract: Microbial geo-technology is an innovative eco-friendly technique that uses microbes to improve and strengthen weak or marginal soils. Bio-mediated ground improvement techniques have gained a lot of attention amongst researchers since the past decade. In this review article, an attempt has been made to investigate the different factors that affect the process of biological improvement overall including the type of microbes, quantity of microbes used, cementation solution molarity, pH of the system, treatment method, temperature, degree of saturation, density of soil, nutrient availability, etc. Enhancement in different properties of the treated soil as reported by other researchers was explored and investigated, and proper conclusions were drafted keeping all the factors into consideration. Identification of potential applications and challenges which could be faced in the in situ application of the technique was worked upon, and suggestions were provided. Finally, the limitations and future scope of microbial geo-technology were highlighted.

Effect of compaction time delay on compaction and strength behavior of lime-treated expansive soil contacted with sulfate

Abstract: Application of lime as an additive for controlling the volume change behavior and improving the strength of expansive soils has been in use over several decades. However, the contamination of lime-treated expansive soil with sulfate always results in the deterioration of treated expansive soil. Therefore, this paper highlights the effect of sodium sulfate solution on compaction and strength behavior of lime-treated expansive soil. Further, the effect of compaction time delay and contact period of sulfate solution with lime-treated soil is also brought out in this paper. To bring out the above effects, the lime contents corresponding to the initial consumption of lime (ICL) and ICL ± 1% were used along with sulfate solutions of 5000, 10,000 and 20,000 ppm. The experimental study showed that upon mixing the lime-treated expansive soil with sulfate solutions, the maximum dry unit weight decreased and optimum moisture content increased with increase in concentration of sulfate solutions when compacted without any compaction delay. With compaction time delay, the lime-stabilized soils mixed with distilled water led to the formation of flocs and aggregation of clay particles and decreased the maximum dry unit weight and optimum moisture content. However, the effect of compaction time delay was negligible on maximum dry unit weight as the formation of flocs and aggregation of clay particles were inhibited in lime-treated soil mixed with sulfate solutions. These changes in dry unit weights and soil structure were reflected on the strength of lime-treated expansive soil as well.

Contribution of two artificial intelligence techniques in predicting the secondary compression index of fine-grained soils

Abstract: Fine soils have the particularity of producing very slow settlement over time, particularly secondary settlement, also known as creep. The coefficient Cα that characterizes the creep phenomenon seems difficult to evaluate in the laboratory and in situ. Two approaches are proposed in this article for a better and faster prediction of that coefficient. The first approach is based on machine learning using multi-gene genetic programming, and the second one uses hybridization of particle swarm optimization algorithms and artificial neural networks. A regression analysis allowed identifying the determinant parameters to be used in the calculations. A database from several sites, and containing 203 samples, was utilized. The findings showed that a good agreement exists between the predicted and measured values. This also indicates that these two techniques can be quite interesting for engineers when they have to design works on compressible soils.

Evaluating the use of steel scrap, waste tiles, waste paving blocks and silica fume in flexural behavior of concrete

Abstract: Steel scrap is a waste product of steel plate manufacturing industry. A large quantity of steel scrap is produced by drilling every year. The disposal of those steel scraps is a major issue in Iraq and all over the world. The landfill is one of the methods for disposing the scraps albeit it produces soil pollution. What is worse is that in Iraq there is no waste separation system in a sense that all the waste materials are dumped in soil especially in the desert, and it is harmful to the environment. One way to alleviate the situation, the present study suggests that steel scrap is added with concrete, and the mechanical and physical properties were studied. Waste materials, such as terrazzo tile and paving block, are dumped in landfills. Such action destroys the environment. Recycling these materials and using them as fine and coarse aggregate in new concrete mixes would eliminate the problem. Additionally, these waste materials are considered as non-degradable. Silica fume has been employed as a partial replacement by weight of cement at percentages of (8%, 12%, and 16%) to enhance the concrete that contains the waste materials. This paper examines the workability of addition of steel scrap to the weight of concrete by the percentages of (0.6%, 1.2%, and 1.8%) as well as the addition of porous tile and paving block as partial substitute by percentages of (15%, 30%, and 45%) for coarse and fine aggregate, respectively. Concrete samples were produced and subjected to compression strength, water absorption and split tensile tests. A reduction in strength was observed for all concretes that contain porous tiles waste as the percentage increased, in relation to the control concrete. On the other hand, concrete that contains waste paving blocks shows an increment in strength at the percentages of (15% and 30%) and reduction at the percentage of 45%. Based on the compressive strength test results, steel scrap samples being at 0.6%, 1.2%, and 1.8% show that the strength increased of the samples with 0.6% and decreased of those at 1.2% and 1.8%. Thus, this research demonstrates that the use of three waste materials-crushed tiles waste, steel scraps and paving blocks waste as components of concrete is technically feasible in the manufacture of concrete.

Some studies on microstructural behaviour and unconfined compressive strength of soft soil treated with SiO2 nanoparticles

Abstract: The nanoparticles are basically the smallest particles known in the soil environment. Soil being a particulate material and its essential particles have a different size range. On the other hand, nanoparticles range between 1 and 100 nm and most properties of nanoparticles are size-dependent. In this paper, an experimental study was conducted to study the improvement of strength characteristics of soil treated with SiO2 nanomaterial. Also, X-ray diffraction tests were performed on collected soil samples and nanomaterial. Furthermore, scanning electron microscope analysis was performed to identify the underlying mechanisms of nanomaterials. Soft soils of two types were collected and were treated with nano-silica (SiO2) additive at percentages of 0.5%, 1.0%, 1.5%, and 2.0%. The test outcomes revealed that the unconfined compressive strength increased significantly with increasing percentage of nano-silica. Moreover, a decrease in maximum dry density and increase in optimum moisture content of treated soil were observed. The addition of nanoparticles increased the sample’s reactivity even at an early age and subsequently strength was increased. Therefore, the main aim of this paper was to stabilize soft soil deposits for utilization of various geotechnical applications for sustainable environment.

Investigating the effect of elevated temperatures on the properties of mortar produced with volcanic ash

Abstract: During the recent years, the use of pozzolanic materials (e.g., volcanic ash) in concrete and cement manufacturing has increased significantly since it can reduce the environment hazard associated with using Portland cement. In this paper, the effect of elevated temperatures on the physical and mechanical characteristics of building mortar produced with volcanic ash is experimentally explored. In order to evaluate the performance of the mortar, four different proportions of volcanic ash (0, 5, 15, and 25%)—as weight replacement of the cement—were prepared. A series of tests were conducted after 28, 90, and 120 days under different temperatures (25, 200, 500, and 800 °C). This paper demonstrates that the replacement of cement by a proportion of volcanic ash can sustain an acceptable level of compressive strength and improve the overall characterization of the mortar while reducing the amount of CO2 released. The mortar with 15% ratio of the volcanic ash replacement showed better flexural and the tensile strength. This paper also highlights that the volcanic ash replacement affects the late-age properties of the mortar more than the early age ones at both ambient and elevated temperatures.

Performance of green fibre-reinforced composite made with sodium-carbonate-activated slag as a binder

Abstract: Fibre-reinforced composites offer outstanding performance due to the presence of short fibres in the composite. However, the high content of Portland cement used in this type of composites embodied it with high carbon. The production of Portland cement is very energy-intensive and emits a large volume of carbon dioxide into the environment. Therefore, developing a greener binder that totally or at least partially eliminates the use of traditional Portland cement will contribute significantly to reduction in the embodied carbon of the fibre-reinforced composites used for various construction applications. This paper presents the performance of an eco-friendly fibre-reinforced cementitious composite made with sodium-carbonate-activated slag as a binder. The performance of the developed composite was evaluated in terms of its mechanical, shrinkage, permeability properties and non-destructive properties. A microstructural investigation was also carried out to understand the microstructure of the developed composite. The developed composite exhibited a compressive strength, tensile strength and flexural strength of 38.6 MPa, 2.1 MPa and 4.9 MPa, respectively. The corresponding porosity, sorption and chloride ion penetration are 4.9%, 0.18 mm and 458 coulombs, respectively.

Treatment of an expansive soil using vegetable (DISS) fibre

Abstract: This paper presents the study of treatment of an expansive soil with vegetal fibres. The soil studied is swelling clay from the region of Souk Ahras (Algeria). The use of fibres as reinforcement has shown a certain efficiency which increases the bond between the soil grains due to the friction between the soil particles and the fibre material. The vegetal fibres used are DISS crushed fibres. The influence of the vegetable fibre content on the global behaviour of the soil is studied; by highlighting the role of the inclusion rate of fibre in the soil mass (1, 2 and 3% of content by weight), this will be studied by a series of behaviour and mechanical performance tests. The DISS fibres have undergone chemical-thermal treatment to extract the sugars and soluble substances contained in the vegetal to avoid the decomposition of the latter in the soil. The results will be compared to those of unreinforced soil. Experimental results show that the swelling potentials are reduced by the addition of vegetal fibres, the cohesion of the soil treated is increased, and the soil is more ductile. It has also been shown that 2% of the DISS fibre content is a critical value for reducing the swelling potential of the clay soil.

Improving the geotechnical properties of high expansive clay using limestone powder

Abstract: Soils are the most used construction materials in engineering projects, such as embankments, highways, and railways, in which huge amounts of soil are required. Unfortunately, sometimes, these soils are high expansive clay that makes problems to these projects, and at the same time, there are waste and by-product materials such as limestone powder that has not appropriately exploited in Iraq and causes environmental problems. This study aims to investigate the effect of limestone powder on the geotechnical properties such as unconfined compressive strength (UCS), compressibility indices, Atterberg limits, and swelling characteristics of high-plasticity clay (CH) in Erbil city in the Kurdistan Region of Iraq as this region is rich in limestone rocks. The high expansive clay was treated by different percentages (6%, 12%, 18%, 24%, 30%, and 36%) of limestone powder. The results indicated that the geotechnical properties could be improved by using limestone powder. Also, the optimum percentage of limestone powder that can be added to expansive soil is recommended.