Use of heavy fuel fly ash (HFFA) (diesel and cracked fuel) for power generation in Saudi Arabia has generated and accumulated large quantities of HFFA as a byproduct. In this research, HFFA is studied with the emphasis on the utilization of this waste material in concrete blocks and asphalt concrete mixes. Two types of mixes, one with low and other with high cement content, were studied for concrete blocks. Different mixes having varying percentages of HFFA (0% to 25%), as cement/sand replacement or as an additive, were studied. The performance of concrete blocks is evaluated in terms of compressive strength, water absorption, durability and environmental concerns. The results showed that blocks cannot be cast if more than 15% HFFA is used; also there is a marginal reduction in the strength of all the mixes before and after being exposed to the sulfate solution for a period of ten months. HFFA is studied in asphalt concrete mixes in two ways, as an asphalt modifier (3&5%) and as a filler (50%) replacement, the results showed an improvement in stiffness and fatigue life of mixes. However, the stability and indirect tensile strength loss were found to be high as compared to the control mix due to moisture damage, indicating a need of using antistripping agents. On environmental concerns, it was found that most of the concerned elements are within acceptable limits also it is observed that lower concentration of barium is leached out with the higher HFFA concentrations, which indicates that HFFA may work as an adsorbent for this leaching element.
Sustainable development programs focus on reducing traditional energy usage and finding alternative energy sources. Thermal insulation materials can improve energy efficiency and reduce negative environmental impact, and be cost-effective by using low density, strong heat resistance, good thermal conductivity, and durability. Consequently, a novel arrangement of hollow concrete blocks was manufactured on-site in this research. In order to assess the commercial viability of these hollow concrete blocks, four distinct variants (perlite, vermiculite, scoria, and polystyrene) were investigated. Economic viability, fuel energy use, and CO2 emissions were also assessed using experimentally obtained thermal resistance. All the newly produced blocks have fulfilled the compressive strength and absorption criteria set by the standards for non-load-bearing blocks. The perlite and scoria blocks, with their respective lowest dry density of 1544 and 1673 kg/m3, qualified as lightweight concrete blocks. As a result, their thermal conductivity was over 60% lower than that of the commercially made blocks. In addition, the scoria block proved to be the most cost-effective option. When compared to a normal market block, the best scoria wall may enhance the heat resistance by 144%. In terms of the net present value (NPV) for 40 years, this solution cut energy consumption from 272 to 109 $/m2 (about a 150 % reduction). As an additional benefit, constructing a wall out of scoria blocks resulted in a 2.4 and 1.15-fold decrease in CO2 emissions compared to conventional and control blocks. Furthermore, this study emphasizes the potential environmental benefits, such as saving natural resources, energy, and money by using these by-products to make greener concrete masonry units.
Steel tanks are used in industries for several purposes, such as the storage of chemicals, water, oil, petroleum products, etc. These steel tanks are frequ
Strengthening the seismic deficient beam-column joints (BCJs) in reinforced concrete structures is mostly adopted to avoid any devastating consequences of high-intensity earthquakes. To evaluate the performance of BCJs against seismic action, experimental testing of BCJs under cyclic loading is a time-consuming and cost-intensive work due to the requirement of large-scale instrumentation and testing. This paper reports a study on the numerical and analytical modeling of the seismic behavior of BCJs built using normal concrete and retrofitted with ultra-high performance fiber reinforced concrete (UHPFRC). A computer simulation using the nonlinear finite element (FE) method was developed considering a concrete damage approach in modeling both types of concrete, i.e., normal concrete (substrate) and UHPFRC (overlay). The interface between the substrate and overlay was modeled as a cohesive element. The properties of this bonding interaction were experimentally evaluated based on the results of the push-out test. The simulation results benchmarked with the experimental data of a previously published study. It was found that the proposed FE model is in good agreement with the experimental behavior of seismically tested specimens in terms of global load–displacement, ultimate load, and damage evolution. In addition, the use of surface-to-surface cohesive elements played an important role in the bonding interface under cyclic loading. Additionally, an analytical model was developed to predict the shear capacity after retrofitting the BCJ. The results obtained by using the analytical model were consistent with the corresponding experimental values. Finally, a parametric study was carried out to examine the effects of the thickness of UHPFRC jacketing and longitudinal reinforcements ratio of the beam on the performance of the retrofitted BCJs.
This paper reports a study comprising both experimental and analytical works to capture the flexural behavior of pre-damaged reinforced concrete (RC) beams strengthened with different configurations of ultra-high-performance fiber-reinforced concrete (UHPFRC) layers on the beam’s surface. Firstly, a selected mixture of normal concrete and steel reinforcing bars (both used for casting the RC beams) and a selected mixture of UHPFRC (used for strengthening the RC beams) were characterized, followed by preparing 14 RC beam specimens. While one RC beam was used as a control specimen, the other 13 beams were pre-damaged to three levels by applying flexural loads corresponding to 30, 75, and 90 % of the ultimate flexural load-bearing capacity of the control RC beam. The pre-damaged RC beams were strengthened by applying 30 mm-thick UHPFRC layer(s) to their surface(s) using three different strengthening configurations that included a tensile surface, two vertical surfaces, and three surfaces (tensile and two verticals). The strengthened beams were subjected to flexural loading, and the data pertaining to load versus deflection and strain in reinforcing bars were recorded until the failure. While no changing in the pattern of the strain development in reinforcing steel bars and the mode of failure of the strengthened beams were observed, their flexural performance was significantly affected by their degree of pre-damaging and the strengthening configuration. The strengthened RC beams pre-damaged by 30 % showed significantly higher enhancement in the load-bearing capacity than the strengthened RC beams pre-damaged by 75 and 90 % because of the fact that the steel reinforcement in strengthened RC beams with a pre-damage of 30 % did not yield before strengthening, contrary to the beams pre-damaged by 75 and 90 % in which the steel reinforcement bars yielded during the damaging process before strengthening and therefore the steel reinforcement had insignificant contribution in improving the flexural performance after strengthening. The three-sided, two-sided, and one-sided UHPFRC strengthened RC beams showed the highest to the lowest enhancement in the flexural performance. The analytical models were derived to predict the ultimate load-bearing capacities of the strengthened RC beams for all three UHPFRC jacketing configurations. Results obtained using the developed analytical models matched very well with the corresponding experimental results.
This paper presents the results of a study on developing optimized alkali-activated binders (AABs) utilizing selected natural minerals and industrial byproducts as precursor materials in addition to sodium hydroxide and sodium silicate as activators. Four selected precursor materials (natural pozzolana, limestone powder, red mud, and silicomanganese fume) were characterized in terms of their physical and chemical properties. The proportioning of the four precursor materials was optimized based on the results of flow, setting time, and compressive strength tests conducted on trial mortars. After reaching an optimal proportioning of the four precursor materials, the natural pozzolan was partially replaced by ordinary Portland cement (maximum 30% by wt.) to significantly enhance the properties of the AABs. The activator to precursor (A/P) ratio, sodium silicate to sodium hydroxide (NS/NH) ratio, sodium hydroxide (NH) molarity, and water to precursor (W/P) ratio, were varied from 0.3 to 0.6, 1 to 2.5, 8 to14 M, and 0.35 to 0.55, respectively. The influence of these activation parameters (at the optimally selected proportioning of precursor materials) on the physical and mechanical properties of AABs besides their mineral composition and morphology was investigated leading towards selecting the optimum AABs. The compressive strength at 28 days ranged from 28.5 to 32 MPa, 24.15 to 31.8 MPa, 24.2 to 33.1 MPa, 15.33 to 31.16 MPa, and 19.7 to 34.1 MPa, as A/P ratio, NS/NH ratio, NH molarity, W/P ratio, and curing method and duration were varied, respectively. XRD, FTIR, and SEM analyses of the AABs were conducted to validate the trends observed in the compressive strength results with variation in the activation parameters. The main phases detected by XRD included CSH, CASH, Mn-SH, KASH, and NASH. FTIR analysis showed bands that coincide with reported vibration and stretching of Si–O-M (M → Al, Si, or Mn) that are associated with geopolymerization, while SEM imaging showed dense microstructure with a homogenous distribution of polymerization gels that filled the microcracks and voids. Additionally, the effect of curing regimes (oven, steam and ambient-air curing) on the performance of AABs was also examined. The results of the present work enabled to identify the optimum proportioning of the selected precursor materials, optimum combination of A/P ratio, NS/NH ratio, NH molarity, and W/P ratio for producing the AABs with enhanced performance.
Laser-induced breakdown spectroscopy (LIBS) is a powerful elemental detection and quantification technique widely employed across various disciplines, including science, engineering, construction, and medicine. This comprehensive review focuses on the recent advancements and challenges in utilizing LIBS for corrosion detection, specifically emphasizing reinforced concrete structures. While LIBS has demonstrated its reliability in corrosion assessment, its adoption as a standardized method is not yet widespread. Identifying and quantifying contaminant elements in targeted structures are crucial steps in corrosion investigation. This review reveals how LIBS can effectively extract elemental contaminants and their relative intensities from samples, establishing correlations with the degree of corrosion. Given that corrosion rate is time-dependent, rapid and accurate techniques like LIBS are essential for timely measurements, enabling multiple instantaneous assessments of contaminant levels. Various calibration techniques and accuracy-enhancing methods are discussed, including calibration curves, chemometrics, and dual-pulsed LIBS approaches for measuring constituent elements. Furthermore, a range of applications for LIBS in concrete technology, cement paste analysis, soil investigations, fluid analysis, and quality control in cement factories are explored. By providing an in-depth understanding of LIBS capabilities and its potential as a reliable and rapid approach for corrosion rate detection in different materials, this study offers valuable insights to researchers, engineers, and industry professionals in pursuing effective corrosion assessment methodologies.
Several non-destructive test (NDT) methods have been used to assess the quality of built concrete. The most popular NDT methods used for in situ testing of
Extensive research work has been performed on shear strengthening of reinforced concrete (RC) beams retrofitted with externally bonded carbon fiber reinforced polymer (CFRP) in form of strips. However, most of this research work is experimental and very scarce studies are available on numerical modelling of such beams due to truly challenging nature of modelling concrete shear cracking and interfacial interaction between components of such beams. This paper presents an appropriate model for RC beam and to simulate its cracking without numerical computational difficulties, convergence and solution degradation problems. Modelling of steel and CFRP and their interfacial interaction with concrete are discussed. Finally, commercially available non-linear finite element software ABAQUS is used to validate the developed finite element model with key tests performed on full scale T-beams with and without CFRP retrofitting, taken from previous extensive research work. The modelling parameters for bonding behavior of CFRP with special anchors are also proposed. The results presented in this research work illustrate that appropriate modelling of bond behavior of all the three types of interfaces is important in order to correctly simulate the shear behavior of RC beams strengthened with CFRP.
In the global effort to mitigate climate change and reduce CO2 emissions, this study introduces an innovative, pioneering approach that combines artificial intelligence and experimental methods to investigate the CO2 footprint (CO2-FP) in fly ash geopolymer concrete materials. Three powerful non-linear intelligent learners, including Gaussian Process Regression (GPR) with Response Surface Methodology (RSM), Support Vector Regression (SVR), and Standalone Decision Tree Regression (DTR) are employed. The models are developed using seven input features related to the curing temperature, fly ash content, concentrations of coarse and fine aggregates, alkaline activators (Na2SiO3, NaOH) content, and superplasticizer. To identify the most influential input features, three different combinations (combo-1, combo-2, and combo-3) of these features are utilized in model building. The models' performance is assessed using key metrics such as coefficient of correlation (CC), Nash Sutcliffe coefficient efficiency (NSE), Mean Absolute Error (MAE), and Root Mean Square Error (RMSE). During the verification phase, the GPR-3 [Combo-3] model emerges as the most efficient in predicting the CO2-FP, with a high CC value of 0.9645 and NSE value of 0.9292. Consistently, Combo-3 demonstrates superior performance across all the models, underscoring the significance of the selected features. The findings of this study provide valuable guidance to industries and policymakers, enabling them to optimize concrete compositions and minimize CO2 emissions, thus contributing to global environmental sustainability.
Ultra-high performance concrete (UHPC) represents a modern class of cementitious materials characterized by superior strength and durability. However, its comparatively high embodied carbon and energy, relative to normal concrete (NC), pose significant sustainability challenges. This study presents a comprehensive evaluation of 40 UHPC mixes through an integrated life cycle assessment (LCA), incorporating embodied carbon (EC), embodied energy (EE), and compressive strength (CS). The assessment includes raw material product stage (A1–A3), transportation (A4), and maintenance (B2–B5) stages. Both local and global material sourcing scenarios are examined. Findings show that UHPC produced locally in Saudi Arabia exhibits 3.28% to 8.21% higher embodied carbon and 1.33% to 4.34% higher embodied energy compared to global equivalents, highlighting the need for optimization in regional production practices. To evaluate sustainability from a performance-based perspective, an eco-strength index (ESI) is employed, capturing the trade-off between EC and compressive strength. The ESI values range from 7.3 to 14.9 kg·CO2/MPa. A case study involving a single-girder bridge constructed with both UHPC and NC demonstrates that, although UHPC exhibits higher impact per cubic meter, its superior mechanical performance enables material reduction, which in turn results in lower total emissions per meter of bridge length. These results emphasize that when structural efficiency is factored in, UHPC can offer a sustainable solution for high-performance infrastructure applications.
This study investigated the flexural behavior of hollow concrete beams reinforced with GFRP bars with longitudinal openings of different sizes and shapes.
