Cyclic freezing and thawing (FT) are a primary cause of cracking in concrete, yet current assessment procedures in Germany rely heavily on qualitative estimation using the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM) capillary suction, internal damage and freeze-thaw (CIF) and Capillary de-icing freeze-thaw (CDF) tests. Although these standard tests provide a general overview of the condition of concrete damage in specimens through the estimation of water saturation through capillary suction, mass of surface delamination, qualitative open surface damage, and relative dynamic modulus of elasticity, they do not take quantitative analysis of voids, including cracks and air pores, directly into account. To address this, we propose a novel workflow utilizing deep learning-based semantic segmentation with Fourier-based slice-to-volume registration by combining 2D light microscopy (LM) of petrographic sections and 3D micro-computed tomography (μCT). We segment cracks, air pores, and aggregates in both modalities and employ feature matching alongside spatial harmonics analysis for 3D shape description. The best proposed 3D registration framework through feature matching demonstrated a success rate of 89.75%, achieving a dissimilarity of 5.21% in relative root mean square error (RRMSE) terms and thereby significantly surpassing the performance of compared 2D-only methods adapted from the body of research. Our approach enables precise, automated, and verifiable quantification of voids across CT and LM modalities and paves the way for advanced computational modeling-based methods to investigate moisture transfer mechanisms for more accurate assessments of frost damage in concrete, service life prediction models, deep learning applications for multimodal data fusion, and more comprehensive FT damage simulations.

The high consumption of natural aggregates in concrete production has led to increased exploitation of natural resources, causing environmental degradation. At the same time, the natural stone industry, particularly Onyx stone processing, generates a significant amount of solid waste that has not been optimally utilized. This study aims to evaluate the effect of using Onyx stone waste as a partial substitution for coarse aggregate on the compressive strength of concrete cylinders and the aesthetic quality of concrete surfaces. A quantitative approach with a pure experimental method was employed. Concrete cylinder specimens with a diameter of 150 mm and a height of 300 mm were prepared with Onyx waste substitution levels of 0%, 10%, 20%, and 30%, with five specimens for each variation. Compressive strength testing was conducted at 28 days in accordance with SNI 1974:2011, while aesthetic aspects were evaluated through visual observation of the concrete surface. The results indicate that Onyx waste substitution of up to 10% does not cause a significant reduction in compressive strength compared to control concrete, with an average value of 28.16 MPa. However, substitutions of 20% and 30% result in statistically significant strength reductions. In terms of aesthetics, higher Onyx content enhances surface color variation and texture. Therefore, the use of Onyx stone waste is recommended as an alternative coarse aggregate up to a maximum level of 10% to achieve environmentally friendly concrete with adequate mechanical performance and improved aesthetic value.

Purpose The growing trend of infrastructure development leads to the depletion of natural resources. Researchers are continually seeking suitable substitutes to mitigate the depletion of natural resources and conserve them. In view of this, this study aims to develop a few innovative concrete mixes with recycled refractory brick (RRB), which is a key by-product from different steel, refractory and other ancillary industries, as a partial to total replacement for fine aggregate. Design/methodology/approach In this investigation, M25-grade concrete with two different types of design mix ratios with 1:1.98:3.78 and 1:2.17:3.74 were produced with a w/c ratio of 0.45. The RRB has been used as a substitute for fine aggregate by weight at 00%, 10%, 20%, 30%, 40%, 50%, 70% and 100% levels. The compressive strength of different concrete mixes has been evaluated after 7 and 28 days of curing periods with potable water having an approximate temperature of 23 ± 2°C. Particle size gradation (mm), fineness modulus, consistency (%), specific gravity and water absorption (%) tests for the raw materials and compression test after 7 and 28 days for the concrete specimens have been conducted. Moreover, the experimental outcomes have also been confirmed through an artificial neural network (ANN). Findings Experimental investigation reveals that, after a seven-day curing period, the sample with 40% and 50% RRB, and after 28 days, samples with 20% replacement of RRB yielded the highest compressive strength, which are 33%, 39% and 15%, respectively. Based on the microstructural analysis, it has been evident that the development of CH and CSH gels fills up the micro pores and results in an improvement in compressive strength. Similar to the experimental output, the proposed ANN model confirmed similar output with the least error percentage of ± 2%–4%. Originality/value The residual mechanical strength and potential of RRB incorporated concrete may be considered appropriate for a wide range of applications under harsh climatic conditions, in particular under high temperature gradients. Deployed ANN to offer specific evaluations of compressive strength short of relying on traditional models, considering complex relationships. The sustainable concrete with recycled refractory brick fine aggregate suits eco-friendly construction, structural and/or nonstructural uses in compliance with IS 10262, IS 516, IS 456. The ANN model complements IS design, accurately predicting strength and optimizing mixes for sustainable construction practices.

High-strength concrete used in modern infrastructure is highly vulnerable to strength degradation and explosive spalling when exposed to elevated temperatures. This study investigates the combined effect of Ground Granulated Blast Furnace Slag (GGBS), Silica Fume, and Polypropylene (PP) fibers on the thermal resistance and residual mechanical performance of M60 grade concrete. GGBS and silica fume were used as partial replacements of cement to enhance strength and microstructural density, while PP fibers were incorporated to control cracking and mitigate spalling under thermal exposure. Concrete specimens were subjected to elevated temperatures of 400°C, 600°C, and 800°C using a controlled heating regime, followed by natural cooling to ambient conditions. Residual compressive strength and flexural strength tests were carried out to evaluate post-heating performance. The results demonstrate that the synergistic incorporation of GGBS, silica fume, and PP fibers significantly improves thermal stability and strength retention compared to conventional M60 concrete. The developed concrete mix shows strong potential for application in fire-prone structures such as high-rise buildings, tunnels, and industrial facilities using economical and locally available materials. The thermal mix retained higher residual strength at 400°C, 600°C, and 800°C compared to conventional concrete.

• The acoustic activity in pre-notched concrete specimens under 3 PB is studied. • The analysis is realized within the frame of Non-Extensive Statistical Mechanics. • The “Variable Returns” parameter of the counts of the hits is employed. • q-Gaussian distributions fit almost perfectly the Probability Distribution Function. • The entropic index q provides signals designating onset of crack propagation. The conditions governing crack propagation in prismatic, concrete specimens, are explored, taking advantage of the Acoustic Emissions recorded during an experimental protocol comprising of standardized bending tests. The time series of the Acoustic Emissions are modelled adopting the concepts of Non-Extensive Statistical Mechanics, as formulated by means of Tsallis entropy and entropic index. The innovation of the present approach lies in the fact that the acoustic data are analyzed using a parameter exhibiting transient characteristics and strong fluctuations, namely, the “Variable Returns” of the “counts” of the acoustic hits. Moreover, the evolution of this parameter is modelled using q-Gaussian- rather than Gaussian-distributions, since the processes that take place while brittle materials are loaded up to fracture are characterized by memory effects and, also, long-range interactions, rendering the traditional Boltzmann-Gibbs Statistical Thermodynamics inadequate for proper modelling. The analysis reveals that Tsallis formalism for the Non-Extensive Statistical Mechanics, models quite satisfactorily the mechanical response of the loaded system and, also, that the q-Gaussian distribution fits almost perfectly the respective Probability Distribution Functions. Deviations are observed only for the tails of the experimental distributions, which correspond to an extremely small portion of the overall number of the acoustic hits that were recorded. In addition, it is revealed that the temporal variation of the entropic index is characterized by a global maximum, which designates entrance into the stage of impending macroscopic fracture and provides a Structural Health Monitoring tool that, under certain conditions, could be interesting from the engineering point of view.

Abstract To evaluate the detection capability of a concrete scanner for Glass Fiber Reinforced Polymer (GFRP) bars, two-dimensional scanning experiments were carried out on concrete specimens reinforced with GFRP bars of various diameters and spacings using a PS1000 concrete scanner. The results indicate that the instrument can effectively identify the position and burial depth of GFRP bars with diameters of 14 mm and 11 mm, while its detection sensitivity for small-diameter bars (8 mm) is limited, resulting in missed detections. The boundary effect and bar spacing also influence the detection results. It should be noted that the PS1000 scanner cannot directly identify the diameter of the bars, although its detection performance (signal clarity and missed detections) is correlated with bar diameter. The findings provide experimental evidence and engineering reference for the application and optimization of non-destructive testing technology for GFRP bars.

To systematically investigate the strain rate dependent mechanical behavior of the concrete interfacial transition zone (ITZ) at the mesoscale, uniaxial compression tests were conducted on mesoscopic concrete specimens under different strain rate conditions by combining optical microscopy and digital image correlation (DIC) techniques. The variations in key mechanical parameters of the ITZ, including thickness, elastic modulus, and Poisson's ratio, were analyzed over a strain rate range of 10⁻⁴ to 10⁻² s⁻¹. The experimental results indicate that, within the investigated strain rate range, the thickness of the ITZ shows no significant variation with strain rate, exhibiting good geometric stability. In contrast, the elastic modulus of the ITZ increases markedly with increasing strain rate, demonstrating a pronounced strain rate strengthening effect, while the Poisson's ratio gradually decreases as the strain rate increases, showing an opposite strain rate dependent response to that of the elastic modulus. Further comparative analysis reveals that the strain rate sensitivity of the mechanical parameters of the ITZ is significantly higher than that of the mortar and aggregate phases, indicating that the interfacial region plays a more prominent regulating role in the overall mechanical response of concrete under varying loading rates. With increasing strain rate, the differences in mechanical properties between the ITZ and the adjacent mortar and aggregate phases gradually diminish. Higher strain rates can effectively suppress the localized weakening effect of the ITZ, thereby promoting a more homogeneous mechanical response of concrete at the mesoscale. The results of this study provide experimental support for mesoscale mechanical modeling and constitutive relationship development of concrete under different loading rate conditions.

The growing demand for concrete has exacerbated the depletion of natural aggregates, necessitating the exploration of alternative materials derived from waste streams. This study examines the feasibility of using blood cockle shells (Anadara granosa), a coastal waste by-product, as a partial replacement for coarse aggregates in structural concrete. Unlike most previous studies that emphasize fine aggregate or filler substitution, this research focuses on coarse aggregate replacement and its influence on both fresh and hardened concrete performance. An experimental program was conducted using 150 mm concrete cube specimens with replacement levels of 0%, 5%, 10%, and 15% by weight, designed in accordance with SNI 03-2834-2000 for a target strength of 25 MPa. All specimens were water-cured and tested at 7, 14, 21, and 28 days. Workability was evaluated through slump tests, while compressive strength was measured using standard compression testing. Results show that workability increased with higher shell content, whereas compressive strength reached an optimum value of 26.5 MPa at 5% replacement before declining at higher substitution levels. These findings demonstrate that low-percentage substitution of blood cockle shell is technically viable and offers a sustainable pathway for structural concrete applications.

Concrete is one of the most widely used construction materials; however, its production leads to significant environmental issues such as high carbon dioxide emissions from cement manufacturing and depletion of natural sand resources. This experimental study focuses on the development of sustainable concrete by incorporating eco-friendly and waste materials as partial replacements for conventional constituents. Neem leaf powder is used as a partial replacement for cement due to its pozzolanic and antibacterial properties, while styrene-butadiene-styrene (SBS) polymer waste is used as a partial replacement for fine aggregate to enhance bonding and crack resistance. The study involves laboratory-based casting, curing, and testing of concrete specimens to evaluate workability and strength characteristics. The results are expected to demonstrate reduced cement consumption, effective utilization of agricultural and polymer waste, improved durability, and overall enhancement in sustainability. This research promotes the use of low cost, environmentally friendly materials in concrete for sustainable construction practices.

Ultrasound measurements are used for monitoring the structural health of concrete. The elastic waves propagating in concrete structures are attenuated by scattering and intrinsic attenuation. Both quantities have to be determined for a detailed material characterization and for realistic numerical simulations of wave propagation in such structures. We present in this paper a numerical approach to determine the intrinsic attenuation of concrete. For this purpose, a realistic digital three-dimensional concrete specimen is created that accounts for correct volume fractions of aggregates of different sizes embedded into a mortar matrix. Using a viscoelastic finite difference scheme, we perform simulations of the ultrasound wave field in these digital models with different attenuation levels. The numerical observations are compared with results from ultrasonic measurements on a sample of saturated concrete to estimate the intrinsic attenuation. Embedded sensors are used for those long-term laboratory experiments. For this saturated concrete, we obtain Q=130 in a frequency band around 60 kHz.

This study examined the effects of controlled interface texture and tack coat application rate on interface shear strength (ISS). The interaction between these two factors has not yet been explored. Double-layered asphalt concrete (AC) specimens were prepared using (i) a new hot-mix asphalt (HMA) layer and (ii) an aged field core as a bottom layer, with a new HMA layer as the top layer. Direct shear tests were conducted on these specimens with varying texture depths and orientations, using SS-1 h tack coat at residual application rates of 0, 0.04, 0.06, and 0.08 gal/yd². Controlled texture depths were generated on new HMA and field cores. The top HMA layer was compacted over each bottom layer using a gyratory compactor, and ISS was evaluated under horizontal deformation using the direct shear test. Shearing was done parallel, perpendicular, and at 45° to the texture orientation. The highest value of ISS was observed at 0.06 gal/yd² in most conditions. Two-way ANCOVA indicates that the texture depth is significant in all groups, while the application rate is significant in most cases, except perpendicular texture-shear orientations. Interactions between application rate and texture were mostly insignificant, except for the smooth surface specimens. For conventional milled surfaces, the application rate is marginally significant. Three-way ANCOVA confirmed a strong texture-shear orientation effect, with perpendicular orientations yielding the highest ISS, followed by 45° and parallel orientations. New HMA specimens show a sharp increase in ISS due to texture depth compared to the field cores. This study found that controlled grinding/grooving enhances interlayer bonding and reduces tack coat dependence.

The improper disposal of Waste Polythene Water Sachets (WPWS) has become a significant environmental concern, contributing to drainage blockages, soil degradation, and pollutants to the environment. This study explores the potential of repurposing WPWS as a replacement for Ordinary Portland Cement (OPC) in the production of concrete paving stones. Experimental mixes were prepared with replacement levels of 50%, 60%, and 70% WPWS alongside a control in triplicate samples, and each specimen was cured using portable water for 7, 14, and 28 days before subjecting the concrete stones specimen on compressive strength and sorptivity tests. The result indicates linear increase in strength development across all curing age and 28-days provides 4304.76, 2819.04 and 2990.47 kg/m3 densities of concrete and compressive strength of 20.1, 18.2 and 19.9 N/mm2 for pave stones impregnated with WPWS by 50, 60 and 70% respectively. The durability of the polymer concrete was minimally affected through sorptivity haven significant value of inflow of water at the middle age curing of pave stone at 70% replacement compared with 50 and 60% of WPWS but however, minimal value of 1.0954 (mm/min-??) was obtained at 70% of WPWS at 28-days compare to control, 50 and 60% replacement. The perception of this study demonstrates that incorporating WPWS into paving stones offers a sustainable waste management solution, reduces environmental hazards, and aligns with circular economy principles. These findings provide a foundation for optimizing mix design and enhancing the bonding characteristics of recycled polyethylene materials in concrete production.

Abstract This study investigated the working performance of mortar after CO 2 injection and mixing. Three curing regimes — carbonation curing, water curing, and combined carbonation-water curing (WC) — were employed to identify the most effective environment and method for curing and strength enhancement. The influence of recycled aggregate strength on the damage evolution of recycled concrete was analyzed using model concrete specimens and the digital image correlation (DIC) technique. The results indicate that specimens subjected to combined carbonation-water curing exhibited the lowest porosity, with a reduction of 1.7%–2.0% compared with those under carbonation curing alone, which showed the highest porosity. Moreover, the damage evolution process demonstrated clear regularity, and the strain development exhibited a relatively predictable trend. The higher the water-to-cement ratio of the CO 2 -injected mixed mortar, the lower its fluidity, with reductions ranging from 7.3% to 13.3%. Conversely, a lower water-to-cement ratio resulted in a greater loss of workability after CO 2 injection mixing. In addition, a pronounced strength difference between the new and old mortar matrices led to strain concentration within the old mortar region.

The construction industry, particularly the production of Portland cement, is a significant contributor to global carbon dioxide emissions and natural resource depletion. This study investigates the feasibility and effectiveness of partially replacing cement with two widely available by-products: Fly Ash (FA), a industrial waste from coal combustion, and Rice Husk Ash (RHA), an agricultural residue. The primary objective is to develop concrete mixes that not only reduce the environmental footprint but also maintain or enhance the mechanical and durability properties. Experimental programs were designed to cast and test concrete specimens with varying replacement levels of cement with FA (15%, 25%, 35%) and RHA (5%, 10%, 15%). The key parameters evaluated include workability (slump test), compressive strength at 7, 28, and 56 days, split tensile strength, water absorption, and resistance to sulphate attack. The results indicate that a ternary blend of 70% OPC, 25% FA, and 5% RHA yields an optimal balance. This mix achieved a 28-day compressive strength comparable to the control (0% replacement) while demonstrating a 22% reduction in water absorption and superior resistance to sulphate exposure. Microstructural analysis via Scanning Electron Microscopy (SEM) revealed a denser matrix with reduced calcium hydroxide content, explaining the improved durability. The study concludes that the synergistic use of FA and RHA presents a viable, eco-friendly pathway for producing high-performance, sustainable concrete, contributing directly to the circular economy and greener construction practices.

This paper presents an experimental framework that allows damage identification and retrofitting assessment in reinforced concrete (RC) beam with implemented piezoelectric lead zirconate titanate (PZT) sensors embedded into the concrete matrix. The study was conducted with concrete prepared from 30% refuse-derived fuel (RDF) fly ash and 70% cement as part of research on sustainable materials for structural health monitoring (SHM). Electromechanical impedance (EMI) was employed for detecting structural degradation, with progressive damage and evaluation of recovery effects made using root-mean-square deviation (RMSD) and conductance changes. Concrete beam specimens with dimensions of 700 mm × 150 mm × 150 mm and embedded with 10 mm × 10 mm × 0.2 mm PZT sensors were cast and later subjected to three damage stages: concrete chipping (Damage I), 50% steel bar cutting (Damage II), and 100% steel bar cutting (Damage III). Three retrofitting stages were adopted: reinforcement welding (Retrofitting I and II), and concrete patching (Retrofitting III). The results demonstrated that the embedded PZT sensors with EMI and RMSD analytics represent a powerful technique for early damage diagnosis, reserved retrofitting assessment, and proactive infrastructure maintenance. The combination of SHM systems and sustainable retrofitting strategies can be a promising path toward resilient and smart civil infrastructure.

Crushing is a critical step in the efficient utilization of quasi-brittle materials such as ores and solid wastes. During this process, materials undergo fracture, and the product particles are ejected, carrying significant kinetic energy. This study investigates typical quasi-brittle materials—concrete and quartz glass—by conducting impact crushing tests using a drop-weight apparatus under varying contact modes and input energy levels. High-speed camera was employed to capture the fracture patterns of the materials and the trajectories of the ejected particles, enabling the calculation of kinetic energy during crushing. The results indicate that under point contact loading, both kinetic energy and its proportion increase significantly with rising input energy. In contrast, under surface contact loading, the kinetic energy and its proportion exhibit minimal change as input energy increases. The average ejection velocity of particles from quartz glass specimens during crushing was 6.28 m/s, which is 2.21 times that of concrete specimens. Moreover, the average proportion of kinetic energy in quartz glass crushing was 5.049%, approximately 14.43 times greater than that in concrete. Enhancing material toughness and adopting surface contact loading help reduce both the kinetic energy and its proportion during crushing. This research contributes to minimizing kinetic energy loss and improving the efficiency of energy utilization in crushing processes.

The brittle characteristics of fiber-reinforced concrete make it difficult to capture the time-varying properties during its flexural failure. This study employed high-speed imaging to investigate the effects of polypropylene fiber, polyvinyl alcohol fiber (PVA), and basalt fiber on the fracture behavior of concrete. The influence mechanisms of fibers on concrete fracture performance were thoroughly revealed by analyzing failure time, crack growth rate, fracture development process, and flexural strength. The results show that fibers significantly extend the time to flexural failure in concrete. At a fiber volume fraction (FVF) of 0.3%, the fracture times of PVA-reinforced concrete and basalt fiber-reinforced concrete increased by 23% and 17%, respectively, compared to plain concrete. Their average crack growth rates were 27.0 m/s and 28.6 m/s, respectively, which are lower than the 33.3 m/s observed in plain concrete. In the initial frame capturing crack initiation, the average crack growth rate was 35.7 m/s for fiber-reinforced concrete and 31.5 m/s for plain concrete. By the second frame, these rates increased to 67.8 m/s and 63.1 m/s, respectively. The cracking process in both plain and fiber-reinforced concrete specimens exhibited a “fast-to-slow” pattern. At approximately 1.5 ms, the crack shown in the second frame had propagated to about two-thirds of the specimen height. Compared to plain concrete, the flexural strengths of polypropylene fiber-reinforced concrete increased by 39.2%, 22.9%, and 26.2%; basalt fiber-reinforced concrete increased by 10.0%, 0.2%, and 9.3%; and PVA-reinforced concrete increased by 9.0%, 7.0%, and 10.6% at FVFs of 0.1%, 0.2%, and 0.3%, respectively.

Regarding the issues arising from the addition of external curing agents in the application of epoxy resin in cement-based materials, this paper explores the feasibility of endogenous curing of epoxy resin in the alkaline environment of cement-based systems. It further analyzes and investigates the curing characteristics of epoxy resin without external curing agents and their impact on the performance of cement-based materials. Differential scanning calorimetry, mechanical property testing, microstructural observation, and electrochemical impedance spectroscopy were used to study the mechanism of sodium hydroxide (NaOH) catalyzing the process of bisphenol-A epoxy resin (E-51)-based curing, the influence of moisture and temperature on curing kinetics, and the performance of epoxy resins in mortar and self-healing concrete. The results showed that E-51 achieved self-curing under alkaline conditions in the absence of an external hardener. However, moisture significantly inhibited the reaction process. Elevating the temperature and reducing environmental humidity effectively promoted the curing reaction. In cement-based materials, E-51 exhibited endogenous curing by the inherent alkalinity of the system, remarkably enhancing the compressive strength of mortar. At 60 °C, mortar containing 10% E-51 (by cement mass) exhibited a 1.5-fold higher compressive strength than that of the control group without E-51 at 14 days of curing. It demonstrated higher healing efficiency in a microencapsulated self-healing concrete system than the traditional curing agent systems. Concrete specimens with damage induced by loading at 60% of their compressive strength exhibited 100% recovery of ultrasonic pulse velocity after storing indoors for 28 d. The findings of this study can provide theoretical basis and technical support for the application of epoxy resins in cement-based materials without the need for curing agents.

This study investigates the axial compressive behaviour of very-low-density lightweight concrete confined with fibre-reinforced polymer (FRP) jackets to improve understanding of its structural performance. The research aims to evaluate how confinement level, concrete strength, density, and fibre type influence confined strength and ductility in square sections. An experimental program was conducted using 150 mm × 150 mm × 300 mm lightweight concrete specimens with a target density of approximately 1550 kg/m³, wrapped with carbon FRP (CFRP) and glass FRP (GFRP) in two-an- three-layer configurations. Axial compression tests were used to establish stress–strain relationships and to determine key parameters, including confined strength ratio and ultimate strain ratio. The results show that FRP confinement produces substantial increases in both compressive strength and strain capacity, with fʹcu/fʹc values up to about 3.29 and εcu/εco ratios exceeding 20, confirming the high confinement efficiency attainable in very-low-density mixes. Higher strength concrete achieved greater ultimate stress but lower ultimate strain, whereas lower density concrete developed larger ultimate strains under effective jacketing. Comparisons between CFRP and GFRP revealed that, in some cases, GFRP confinement provided comparable or superior enhancement of strength and deformability, emphasising the role of material compatibility and installation quality. Overall, the findings extend the experimental database for FRP-confined lightweight concrete at densities near 1550 kg/m³ and highlight the need for refined predictive models and design provisions tailored to this density range.

High-strength straight anchor bolts materials require longer embedment lengths in the concrete so the headed bars are employed to significantly reduce the required embedment length of these bars. But they impose concentrated stress on a small concrete surface under the head. In this study, behavior of headed bolts was numerically studied using 3D finite element method (FEM). First, an experimental program consists of four concrete specimens with variations only in head diameter was conducted. Second, FEM program consists of 22 concrete specimens was conducted. The effect of concrete cover thickness around the head was ranging from 85mm to 510mm. This variation resulted in a broad range of concrete cover-to-stud diameter ratios from 5 to 30. Additionally, studying the impact of head geometry (hexagonal, square, circular, and pentagonal) was performed. The effect of head diameter from 12mm up to 50mm was examined. This study also assessed the effect of using high strength concrete under the head region. The results showed that all specimens exhibited localized compressive failure of the concrete beneath the headed bars. Due to its increased number of sides, the hexagonal head performed better than the square head. When compared to a headed bar with a diameter of 12mm, the ultimate local pressure of headed bars with diameters of 15, 17, 20, 25, 30, 40, and 50mm dropped by 53, 60, 68, 76, 78, 87, and 90%, respectively. When the concrete cover-to-stud diameter increased from 5 to 30, there was a noticeable improvement in the final local pressure and the related slip under the rebar head. Overall performance of the bars improved with increase of the members number of the head. When high strength concrete was used under the head, the ultimate local pressure of headed bars increased by 29-152%. Many new formulas were proposed for estimating ultimate local pressure of headed bars.