Alkali-activated concrete (AAC) or binders (AABs) have emerged as a substitute to conventional ordinary Portland cement (OPC)–based concrete owing to
This computational investigation focused on numerical modeling of the shear behavior of ultra‐high‐performance concrete (UHPC) beams reinforced longitudinally with high‐strength rebars and ordinary‐strength steel (stirrups). Nonlinear three‐dimensional finite element model, using the concrete damaged plasticity model and material properties obtained from uniaxial compressive and tensile laboratory tests, was conducted to simulate UHPC concrete beams within a commercial finite element software package ABAQUS 6.13. This investigation included the effects of various parameters; shear span‐to‐effective depth ratio ( a/d ), volume fraction of steel fibers, V f , longitudinal reinforcement ratio, ρ , and stirrups spacing, s , on shear behavior of UHPC beams. Numerical results compared with previously obtained experimental results in terms of shear force–midspan deflection and cracking‐propagation behaviors. The results showed that finite element analysis predicted the shear behavior of UHPC beams in good agreement with the experimental data and predicted the response of the beam with variation in various parameters with a good accuracy.
Many recently developed materials have proven their capability as retrofitting materials for different applications. These materials include carbon fiber-reinforced plastic (CFRP) and ultra-high-performance concrete with steel fiber reinforcement (UHPFRC). In this work, the influence of wrapping the UHPFRC cylinders with CFRP was investigated numerically. Different parameters were considered, including the grades of UHPFRC and configurations of CFRP. A 3D finite element model (FEM) of UHPFRC cylinders wrapped with CFRP under static loading was developed using nonlinear finite element software (ABAQUS). The model was first verified using the experimental results provided in the literature. After that, parametric studies were carried out to study the impact of grades of UHPFRC and the different confining CFRP schemes (fully and partially) on the overall behavior of strengthened cylindrical UHPFRC, as well as the impact of increasing the thickness of CFRP layers on the strength and ductility ratio of the confined specimens. The results indicated that using CFRP to warp the UHPFRC specimens significantly improved their strength and ductility. As expected, the use of CFRP to partially wrap specimens did not show a significant enhancement in the strength of the confined specimens when the CFRP layers were less than 60% of the height.
In this project, the hygro-thermo-mechanical bending behavior of perfect and imperfect advanced functionally graded (AFG) ceramic-metal plates is analytically investigated using an integral plate model for the first time. The plate is assumed to be supported by a two-parameter elastic foundation. Because of the technical problems encountered in the manufacture of AFG, porosities and micro-voids can occur in AFG specimens, which can result in reduced density and strength of materials. Thus, due to the presence of porosity, a modified rule of mixture is adopted to predict the material properties of the AFG plates. The governing equations are deduced by adopting the principle of virtual and an integral plate model. The analytical Navier's method is considered to solve the obtained differential equations for simply supported AFG porous plate. The results obtained are checked by comparing them for non-porous and porous AFG plates with those available in the open literature. Finally, this work will help us to design advanced functionally graded materials to ensure better durability and efficiency for hygro-thermal environments.
The complexity of the hydration process of cementitious materials makes developing universal models that predict their mechanical behavior challenging. The current study used a novel molecular modeling method to develop a bottom-up model of the cement paste that incorporated different contents of the nano-red mud (nRM). A molecular dynamics (MD) simulation and dreiding force field were employed to build the ingredient-based models using the cement clinker phases and nRM oxides. Different cement-nRM mixtures were prepared and macroscopically tested under compression and flexure. In addition, a detailed microstructural analysis using XRD, SEM, EDS, and Raman was carried out on the prepared of nRM. The experimental results were used to validate the results of the developed molecular models. The simulation results demonstrated the capability of the atomistic models for predicting the strength and stiffness of the cement-nRM composites accurately. In addition, the developed hydrated cement model was found with the line of C–S–H-mineral structure (called tobermorite 11 Å). The molecular characterization, in terms of the radial distribution function and fractional free volume, also provided useful information on the local structures of the models. The molecular models of cement-nRM can be further used to predict the durability properties as well as gain deep insights into the mechanical performance of blended mixtures.
Corrosion is a major challenge impacting industries such as construction, petrochemicals, and metallurgy. This study presents an innovative approach to predicting corrosion rates in reinforced concrete by employing laser-induced breakdown spectroscopy (LIBS) and machine learning. Corroded samples were analyzed using LIBS to identify elemental compositions and their intensities, focusing on Si, Al, Fe, Ti, Na, Ca, and Cl as input features for the models. Three different machine learning models (Support Vector Regression (SVR), Gaussian Process Regression (GPR), and Decision Tree Regression (DTR)) were trained to predict corrosion rates. The input features were tested in three combinations: Combo-1 (Si, Al, Cl), Combo-2 (Si, Al, Fe, Ca, Cl), and Combo-3 (Si, Al, Fe, Ti, Na, Ca, Cl). The models' performance was evaluated using metrics such as Mean Absolute Error (MAE), Nash Sutcliffe Efficiency (NSE), Root Mean Square Error (RMSE), and Correlation Coefficient (CC). The results showed that Combo-3 consistently achieved the highest prediction efficiency for SVR (NSE = 0.9734, CC = 0.9874) and GPR (NSE = 0.9785, CC = 0.9900) during testing, highlighting the importance of comprehensive input descriptors. However, for the DTR model, Combo-1 (NSE = 0.9997, CC = 0.9970) exhibited the highest prediction efficiency, demonstrating its capability to accurately predict with fewer descriptors. This research offers valuable insights for industries and policymakers aiming to mitigate the adverse effects of corrosion, emphasizing the potential of combining LIBS with machine learning for precise corrosion rate prediction.
In this study, the effectiveness and efficiency of two different techniques for strengthening of reinforced concrete (RC) beams using ultra-high performance fiber reinforced concrete (UHPFRC) was investigated i.e.; (i) by sand blasting RC beams surfaces and casting UHPFRC in-situ around the beams inside a mold and (ii) by bonding prefabricated UHPFRC strips to the RC beams using epoxy adhesive. Beams under each technique were strengthened in three different strengthening configurations; (i) bottom side strengthening (ii) two longitudinal sides strengthening (iii) three sides strengthening. Bond strength tests were carried out to ascertain the bond between normal concrete and the UHPFRC, for both sand blasting and epoxy adhesive techniques. Test results for retrofitted beams under flexure regarding various behavioral attributes such as crack propagation, stiffness and failure load indicated significant positive developments resulting from the two strengthening techniques. Beams strengthened on three sides showed the highest capacity enhancement, while beams strengthened only at the bottom side showed the least enhancement. However, there were some concerns regarding loss of ductility with increased use of UHPFRC as part of the tensile retrofit. Finite element (FE) and analytical models were developed to predict the behavior of the beam specimens. The result of the models showed good agreement with experimental results, as they were able to predict the behavior of the beams with high accuracy.
Epoxy resins are widely used as construction and repair materials. However, their bond with the concrete substrate under wet conditions is of concern as the loss of compatibility will lead to the failure of the bonded system. The reported study investigated the effect of surface moisture at the epoxy/cement interface using molecular dynamics (MD) simulation. The model of the interface was built using calcium silicate hydrate (C–S–H), as a hydrated cement substrate and diglycidyl ether of bisphenol-F (DGEBF) as an epoxy resin. Subsequently, different layers of water molecules were inserted into the model to represent varying moisture concentrations at the interface. The interfacial properties of the dry and wet models were evaluated in terms of adhesion, debonding, and energy ratios. In addition, the radial distribution function (RDF) was employed to deeply investigate the atomic interaction between the cement surface and epoxy. The results of the model indicated that the adhesion properties were adversely affected by the presence of moisture at the epoxy/cement interface. The degradation in the adhesion at moisture contents of 3% and 6% was 37.49% and 72.02%, respectively. Additionally, it was found that the detachment increased, as evident from the values of debonding, at higher moisture contents due to an increase in the adhesion between the C–S–H and water molecules where the latter form hydrogen bonds with the substrate. This work provides valuable molecular-level insights into the epoxy/cement bond that can be used to design new epoxy resins suited for cement and concrete applications.
The tuned mass damper-clutching inerter (TMDCI), which has been recently developed, has twofold benefits: the mass amplification effect and energy absorpti
Abstract The drive toward sustainable construction materials has encouraged the partial replacement of cement with Recycled Concrete Powder (RCP) in Ultra-High-Performance Concrete (UHPC). This study presents a preliminary evaluation of UHPC incorporating 10%, 20%, and 30% RCP by mass as a cement substitute. Compressive strength tests revealed a ~40% reduction at 10% RCP, ~60% at 20%, and over 75% at 30%, relative to the RCP0 control mix. To enhance the reactivity of RCP and offset these performance losses, a wet carbonation treatment was conducted using magnesium chloride (MgCl 2 ) solutions at 0.1, 0.2, 0.4, and 0.8 M for durations of 30 minutes, 1.5 hours, 3 hours, and 5 hours. The heat of hydration of a UHPC mix with 10% wet-carbonated RCP was measured via isothermal calorimetry. Results showed that shorter carbonation conditions (e.g., 0.4 M MgCl 2 for 30 min) increased cumulative heat release by 16% compared to untreated RCP, indicating improved pozzolanic reactivity. Conversely, higher concentrations and longer durations resulted in a decrease of up to 5%, suggesting inhibitory effects from salt deposition or pore blocking. These findings support the feasibility of optimizing carbonation conditions to improve the performance of RCP in UHPC, enabling more sustainable and durable concrete mix designs.
This paper presents a study on the shear behavior of reinforced concrete (RC) beams strengthened by jacketing the surfaces of the beams using ultra-high performance fiber reinforced concrete (UHPC). The surfaces of the RC beams were prepared by sandblasting and UHPC was cast in situ over the surfaces of RC beams. The beams were strengthened using two different strengthening configurations; (i) two longitudinal sides strengthening (ii) three sides strengthening. The bond between normal concrete and UHPC was examined by conducting splitting tensile strength and slant shear strength tests on composite cylindrical specimens cast using normal concrete and UHPC. The control and strengthened beam specimens were tested using four-point loading arrangement maintaining different shear span-to-depth ratios. The results of tested beams showed the beneficial effects of strengthening the RC beams using UHPC, as evident from enhancement of the shear capacity and shifting of the failure mode from brittle to ductile with more stiff behavior. In addition, a non-linear finite element model (FEM) was developed to examine the sufficiency of the experimental results used to study the shear behavior of control and strengthened beams. The failure loads and the crack patterns determined experimentally matched well with those predicted using the proposed model with a reasonably good degree of accuracy.
Laser-induced breakdown spectroscopy is a remarkable elemental detection and quantification technique employed in various sectors such as science, engineer
Post-tensioned single-cell concrete box girders of variable depth are used in continuous bridges to achieve both economy and aesthetics. In this paper, the
