Characterization and Applications of Red Mud, an Aluminum Industry Waste Material, in the Construction and Building Industries, as well as Catalysis.

The disposal of red mud (RM), a waste material generated by the aluminum industry, remains a global environmental concern because of its high alkalinity and smaller particle size, which have the potential to pollute air, soil, and water. Recently, efforts have been made to develop a strategy for reusing industrial byproducts, such as RM, and turning waste into value-added products. The use of RM as (i) a supplementary cementitious material for construction and building materials, such as cement, concrete, bricks, ceramics, and geopolymers, and (ii) a catalyst is discussed in this review. Furthermore, the physical, chemical, mineralogical, structural, and thermal properties of RM, as well as its environmental impact, are also discussed in this review. It is possible to conclude that using RM in catalysis, cement, and construction industries is the most efficient way to recycle this byproduct on a large scale. However, the low cementitious properties of RM can be attributed to a reduction in the fresh and mechanical properties of composites incorporating RM. On the other hand, RM can be used as an efficient active catalyst to synthesize organic molecules and reduce air pollution, which not only makes use of solid waste but also lowers the price of the catalyst. The review provides basic information on the characterization of RM and its suitability in various applications, paving the way for more advanced research on the sustainable disposal of RM waste. Future research perspectives on the utilization of RM are also addressed.

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

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

Construction Building Materials as a Potential for Structural Supercapacitor Applications.

Emerging demands to achieve zero carbon emissions and develop renewable energy resources necessitate the development of appropriate energy storage systems. To achieve this, several alternatives to conventional energy storage devices, such as Li-ion batteries or capacitors to more sustainable and scalable energy storage systems, are being explored. Supercapacitors, possess unique characteristics that include high power, long life, and environmental-friendly design. They may be used to bridge the energy-power gap between typical capacitors and fuel cells/batteries. Recently, structural supercapacitors being capable of storing electrochemical energy besides bearing mechanical load have caught the attention of researchers. As such, efforts have been made worldwide to study both the fundamental and applied aspects of structural supercapacitors. Further, the possibility of using construction materials for interdisciplinary applications is being studied because they are relatively cheap and easily available. Thus, construction materials can be considered as potential candidates for the development of structural supercapacitors. Herein an overview on the use of construction materials, such as Portland cement concrete, geopolymer concrete, and bricks, as a component of structural supercapacitors has been presented.

Characterization, Processing, and Application of Heavy Fuel Oil Ash, an Industrial Waste Material - A Review.

Heavy fuel oil ash (HFOA) is generated as an industrial waste material during the combustion of heavy fuel oil in power/desalination plants. With increasing energy demands, a significant volume of HFOA is generated. It is generally disposed of in landfills, causing environmental pollution, as it contains several toxic elements. Recently, efforts were made towards developing strategies for reusing industrial waste materials and creating value-added products from the waste materials. Despite significant information available in the literature on the utilization of HFOA, there is still a need for a thorough and systematic review on the characterization and utilization of HFOA in various applications. Consequently, this paper aims to present a critical review of the literature on HFOA generation, its chemical composition, physical properties, morphology, and applications. It is encouraging to note that HFOA has been used in several potential applications, such as the preparation of activated carbon and carbon nanotubes, metal recovery, environmental pollutant removal, polymer composites and construction materials, etc. However, the development of several value-added materials utilizing HFOA and its applications in other areas such as coatings, cathodic protection systems, and phase change materialswould emerge as a new topic of research. It is expected that this review will act as a precursor for further research on the use of HFOA in industrial applications. Since the use of HFOA will lead to environmental, economic, and technical benefits, research in the utilization of this industrial waste material is highly recommended.

A statistical approach to optimizing concrete mixture design.

A step-by-step statistical approach is proposed to obtain optimum proportioning of concrete mixtures using the data obtained through a statistically planned experimental program. The utility of the proposed approach for optimizing the design of concrete mixture is illustrated considering a typical case in which trial mixtures were considered according to a full factorial experiment design involving three factors and their three levels (3(3)). A total of 27 concrete mixtures with three replicates (81 specimens) were considered by varying the levels of key factors affecting compressive strength of concrete, namely, water/cementitious materials ratio (0.38, 0.43, and 0.48), cementitious materials content (350, 375, and 400 kg/m(3)), and fine/total aggregate ratio (0.35, 0.40, and 0.45). The experimental data were utilized to carry out analysis of variance (ANOVA) and to develop a polynomial regression model for compressive strength in terms of the three design factors considered in this study. The developed statistical model was used to show how optimization of concrete mixtures can be carried out with different possible options.

Development of UHPC mixtures utilizing natural and industrial waste materials as partial replacements of silica fume and sand.

In the exploratory study presented in this paper, an attempt was made to develop different mixtures of ultrahigh performance concrete (UHPC) using various locally available natural and industrial waste materials as partial replacements of silica fume and sand. Materials such as natural pozzolana (NP), fly ash (FA), limestone powder (LSP), cement kiln dust (CKD), and pulverized steel slag (PSS), all of which are abundantly available in Saudi Arabia at little or no cost, were employed in the development of the UHPC mixtures. A base mixture of UHPC without replacement of silica fume or sand was selected and a total of 24 trial mixtures of UHPC were prepared using different percentages of NP, FA, LSP, CKD, and PSS, partially replacing the silica fume and sand. Flow and 28-d compressive strength of each UHPC mixture were determined to finally select those mixtures, which satisfied the minimum flow and strength criteria of UHPC. The test results showed that the utilization of NP, FA, LSP, CKD, and PSS in production of UHPC is possible with acceptable flow and strength. A total of 10 UHPC mixtures were identified with flow and strength equal to or more than the minimum required.

Effect of the key mixture parameters on shrinkage of reactive powder concrete.

Reactive powder concrete (RPC) mixtures are reported to have excellent mechanical and durability characteristics. However, such concrete mixtures having high amount of cementitious materials may have high early shrinkage causing cracking of concrete. In the present work, an attempt has been made to study the simultaneous effects of three key mixture parameters on shrinkage of the RPC mixtures. Considering three different levels of the three key mixture factors, a total of 27 mixtures of RPC were prepared according to 3(3) factorial experiment design. The specimens belonging to all 27 mixtures were monitored for shrinkage at different ages over a total period of 90 days. The test results were plotted to observe the variation of shrinkage with time and to see the effects of the key mixture factors. The experimental data pertaining to 90-day shrinkage were used to conduct analysis of variance to identify significance of each factor and to obtain an empirical equation correlating the shrinkage of RPC with the three key mixture factors. The rate of development of shrinkage at early ages was higher. The water to binder ratio was found to be the most prominent factor followed by cement content with the least effect of silica fume content.

A simple and reliable setup for monitoring corrosion rate of steel rebars in concrete.

The accuracy in the measurement of the rate of corrosion of steel in concrete depends on many factors. The high resistivity of concrete makes the polarization data erroneous due to the Ohmic drop. The other source of error is the use of an arbitrarily assumed value of the Stern-Geary constant for calculating corrosion current density. This paper presents the outcomes of a research work conducted to develop a reliable and low-cost experimental setup and a simple calculation procedure that can be utilised to calculate the corrosion current density considering the Ohmic drop compensation and the actual value of the Stern-Geary constants calculated using the polarization data. The measurements conducted on specimens corroded to different levels indicate the usefulness of the developed setup to determine the corrosion current density with and without Ohmic drop compensation.

Effect of silica fume substitution by limestone powder and cement kiln dust on the shrinkage, durability, and sustainability of UHPC.

Silica fume is usually used in UHPC, three times more than that for normal concrete, to enhance mechanical properties and durability. However, silica fume (SF) is an expensive material and has high production costs. This work is aimed at investigating the shrinkage and durability performance of previously developed UHPC mixtures utilizing the two calcareous waste materials, namely limestone powder (LSP) and cement kiln dust (CKD), by partially replacing the silica fume. The optimally selected mixtures of UHPC, having flow and strength above the minimum required, were used for detailed investigation in terms of shrinkage and durability characteristics. The results showed that by replacing SF with up to 20% of LSP and up to 20% of CKD, the mechanical properties of UHPC remained satisfactory compared to the control mixture with 100% SF. However, the ultimate shrinkage was higher for mixtures incorporating LSP or CKD, indicating the need for more volume of steel fibers to compensate for the shrinkage strains. The developed UHPCs also exhibited high resistance against reinforcement corrosion and sulfate attack, making them suitable for use in aggressive exposure conditions. However, special attention needs to be paid to the CKD content, where it is recommended to limit the content of CKD to about 15% or less to control the durability performance of the UHPCs. In addition, the sustainability analysis of developed UHPC mixtures was carried out using the life-cycle assessment and eco-strength intensity index. The results indicated that the UHPC mixtures possess a higher life-cycle and are therefore more sustainable.

Optimum design and performance of a base-isolated structure with tuned mass negative stiffness inerter damper.

In order to increase the efficiency of the structures to resist seismic excitation, combinations of inerter, negative stiffness, and tuned mass damper are used. In the present work, the optimum tuning frequency ratio and damping of the tuned mass negative stiffness damper-inerter (TMNSDI) for the base-isolated structure were determined by employing the numerical searching technique under filtered white-noise earthquake excitation and stationary white noise. The energy dissipation index, the absolute acceleration, and the relative displacement of the isolated structure were considered as the optimum parameters, obtained by their maximization. Evaluations of base-isolated structures with and without TMNSDI under non-stationary seismic excitations were investigated. The efficiency of the optimally designed TMNSDI for isolated flexible structures in controlling seismic responses (pulse-type, and real earthquakes) were evaluated in terms of acceleration and displacement. A dynamic system was used for deriving the tuning frequency and tuned mass negative stiffness damper inerter (TMNSDI) for white noise excitation by using explicit formulae of the curve fitting method. The proposed empirical expressions, for design of base-isolated structures with supplementary TMNSDI, showed lesser error. Fragility curve results and story drift ratio indicate reduction in seismic response by 40% and 70% in base-isolated structure using TMNSDI.

Finite Element Modelling of Corrosion-Damaged RC Beams Strengthened Using the UHPC Layers.

This paper describes a study on finite element modeling (FEM) carried out on the ABAQUS platform for the prediction of flexural strength of corrosion-damaged reinforced concrete (RC) beams strengthened using layers of ultra-high-performance concrete (UHPC). Considering different combinations of the degree of reinforcement corrosion and thickness and configuration of UHPC layers, a total of twenty-two corroded, un-strengthened, and strengthened RC beam specimens were tested to record their flexural behavior. Following the flexural testing, the FEM was carried out considering the degradation in the diameter and the yielding strength of the corroded reinforcing bars. The cohesive surface bonding approach was used to simulate the interfacial bond stress slip between the corroded bars and surrounding concrete. The results of the FEM were validated using the experimental test results of the respective beam specimens. The FEM results (including crack pattern, flexural strength, stiffness, and linear and nonlinear behavior of the strengthened RC beams) were found to be in close agreement with the corresponding experimental test results. This indicates that the proposed FEMs can capture the flexural behavior of the corroded RC beams strengthened using layers of UHPC with high accuracy. Furthermore, a parametric study was carried out using the validated FEMs to investigate the effects of varying the compressive strength and thickness of UHPC layers on the flexural strength of the corroded strengthened RC beams.

Evaluating Rutting Resistance of Rejuvenated Recycled Hot-Mix Asphalt Mixtures Using Different Types of Recycling Agents.

Growing environmental pollution worldwide is mostly caused by the accumulation of different types of liquid and solid wastes. Therefore, policies in developed countries seek to support the concept of waste recycling due to its significant impact on the environmental footprint. Hot-mix asphalt mixtures (HMA) with reclaimed asphalt pavement (RAP) have shown great performance under rutting. However, incorporating a high percentage of RAP (>25%) is a challenging issue due to the increased stiffness of the resulting mixture. The stiffness problem is resolved by employing different types of commercial and noncommercial rejuvenators. In this study, three types of noncommercial rejuvenators (waste cooking oil (WCO), waste engine oil (WEO), and date seed oil (DSO)) were used, in addition to one type of commercial rejuvenator. Three percentages of RAP (20%, 40%, and 60%) were utilized. Mixing proportions for the noncommercial additives were set as 0−10% for mixtures with 20% RAP, 12.5−17.5% for mixtures with 40% RAP, and 17.5−20% for mixtures with 60% RAP. In addition, mixing proportions for the commercial additive were set as 0.5−1.0% for mixtures with 20% RAP, 1.0−1.5% for mixtures with 40% RAP, and 1.5−2.0% for mixtures with 60% RAP. The rutting performance of the generated mixtures was indicated first by using the rutting index (G*/sin δ) for the combined binders and then evaluated using the Hamburg wheel-track test. The results showed that the rejuvenated mixtures with the commercial additive at 20 and 60% RAP performed well compared to the control mixture, whereas the rejuvenated ones at 40% RAP performed well with noncommercial additives in comparison to the control mixture. Furthermore, the optimum percentages for each type of the used additives were obtained, depending on their respective performance, as 10%, 12.5%, and 17.5% of WCO, 10%, 12.5−17.5%, and 17.5% of WEO, <10%, 12.5%, and 17.5% of DSO, and 0.5−1.0%, 1.0%, and 1.5−2.0% of the commercial rejuvenator, corresponding to the three adopted percentages of RAP.

Preparation, Characterization, and Evaluation of the Anticorrosion Performance of Submicron/Nanocarbon from Jute Sticks.

Jute stick, one of the most commonly and abundantly available agricultural waste product, was converted to a value-added submicron/nano jute carbon by using pyrolysis and high-energy ball milling techniques. The submicron/nano jute carbon was characterized using FE-SEM, TEM, EDS, XRD, XPS and Raman spectroscopy. The anticorrosive performance of the submicron/nano jute carbon was investigated through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and salt spray techniques, on mild steel plates coated with a mixture of epoxy resin and the submicron/nano jute carbon. The electrochemical impedance of the steel coated with the composite coating was two orders of magnitudes higher than that of the specimen coated with neat epoxy. Consequently, the corrosion rate of specimens coated with composite coating was 13-20 times higher than that of steel coated with neat epoxy coating. The salt spray results also indicate an improvement in the corrosion resistance performance of the composite coating compared to the neat epoxy. The uniform distribution of the submicron/nano jute carbon particles in the epoxy resin improved the denseness of the composite coating by acting as a barrier against the diffusion of chloride, moisture, and oxygen, thus, improving the corrosion resistance of the developed coating.

Utilization of Portland cement with limestone powder and cement kiln dust for stabilization/solidification of oil-contaminated marl soil.

Stabilization/solidification (S/S) is a technique that has been widely used to treat contaminated soils using several types of stabilizers, such as ordinary Portland cement (OPC). In this research, marl soil that was collected from eastern Saudi Arabia was contaminated by either diesel or crude oil at different dosages (i.e., 2.5, 5, and 10% by the dry weight of the soil) and tested to assess its geotechnical and environmental properties. Thereafter, the contaminated soil was stabilized using OPC, limestone powder (LSP), and cement kiln dust (CKD) at different proportions. The contaminated-stabilized soils were evaluated by measuring the changes in their geotechnical properties, and both metal and hydrocarbon contents. Results of this investigation indicated that the S/S treatment of the contaminated soils enhanced the compaction characteristics with a significant improvement in the unconfined compressive strength (UCS) results, and all of S/S-treated mixtures were found to pass the strength criterion of the U.S. Environmental Protection Agency (USEPA) (i.e., 340 kPa after 28 days of curing). Moreover, The UCS results of the stabilized soils were compared to the minimum strength requirements for both paved and unpaved road materials (i.e., 1380 and 690 kPa, respectively). Finally, scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses were used to elucidate the changes in the microstructure of the stabilized soils.