Fatigue bond behavior between high-strength lightweight aggregate concrete and high-strength steel bars

The findings of this paper provide essential knowledge for the effective and economical design of deep beams subjected to pure torsion. As a result, this paper studies the torsional behavior of nine high-strength concrete (HSC) deep beams reinforced by cross-inclined stirrups. The test parameters comprised stirrup type (conventional stirrups and cross-inclined stirrups), inclination angle (45 and 60 degrees), stirrup spacing (100, 150, and 200 mm), the main longitudinal bars (4∅12 and 4∅18), and the side longitudinal bars (without and 4∅12). Torsional moment capacity, crack pattern, twisting angle, strain on longitudinal and transverse reinforcement, and torsional deformation characteristics in terms of stiffness and ductility were used to evaluate the tested beams’ torsional response. Test results clearly indicated that using the cross-inclined stirrup reinforcement improved the evaluated deep beams with conventional stirrups’ torsional capacity, stiffness, ductility, and overall performance. Reducing stirrup spacing from 200 to 100 mm increased torsional capacity by 49% for conventional stirrups and 65% for cross-inclined stirrups. An ABAQUS three-dimensional finite element model was built to evaluate the model’s ability to replicate the experimental beams’ torsional behavior. A theoretical model for ultimate torque calculation was also created. Compared to experimental findings, numerical and theoretical investigations were satisfactory.

Microstructure parameters of concrete have a significant influence on macroscopic mechanical properties. In this article, the pore size distribution, gassing fraction and compressive strength of concrete were obtained through the liquid nitrogen adsorption test, thermogravimetric test of cement paste and the compressive performance test of concrete. At the same time, based on the hexagonal close-packed pore model of concrete, the relationship between concrete microstructure parameters (pore volume fraction and gas evolution fraction) and macro-parameters (compressive strength) were established. The results show that the distribution of micro-pores in higher strength concrete is more uniform, while the distribution of medium and large pores in lower strength concrete is wider. In the temperature range of 100 °C∼500 °C, the concrete with lower compressive strength can precipitate more gas. With the increase of gassing fraction (BcG/Wc ), the compressive strength is positively correlated with gassing fraction (correlation coefficient 0.9323). The compressive strength is negatively correlated with pore volume fraction (correlation coefficient 0.9444) with the pore volume fraction (Vc /(1-Vm )). Compared with the measured results of concrete compressive strength, the mathematical calculation results based on the three-dimensional spherical pore model are basically consistent with them, and the error range is less than 10%, which indicates the reliability of the theoretical calculation model. The influence of the gas evolution fraction (internal gel) on the mechanical properties of concrete is more significant (change rate), and the influence of pore volume fraction is second.

This study investigates the influence of palm oil fuel ash (POFA), in micro- and nanoparticle sizes, as a partial cement substitute in high-strength concrete (HSC). Thirteen mixtures incorporating varying proportions of micro-POFA (10%–30%) and nano-POFA (2%–8%) were assessed for workability, mechanical properties, durability, and microstructural characteristics. The optimal formulation—10% micro-POFA combined with 4% nano-POFA—yielded a peak compressive strength of 100.7 MPa at 91 days, alongside enhanced tensile, flexural, and elastic properties, with markedly reduced water permeability. Thermal resistance evaluations confirmed adequate strength retention up to 800 °C. Scanning electron microscopy identified a denser matrix and refined interfacial transition zone, attributed to heightened pozzolanic reactivity. Ensemble machine learning models accurately predicted compressive strength outcomes, complemented by a graphical user interface enabling real-time strength estimation for practical engineering applications. These findings affirm the viability of optimized micro–nano POFA blends in sustainable, high-performance concrete development.

Knowledge of the behavior of high-strength concrete reinforced with bamboo fibers remains limited with respect to compressive deformability and flexural fracture energy. The effect of alkali-treated bamboo fibers (1.0% and 1.5% by weight of cement; 2% NaOH) on the fresh-mix properties, mechanical performance, compressive deformability, and flexural fracture energy of high-strength concrete was evaluated. The addition of fibers increased the air content and reduced the consistency of the mix. The compressive strength changed by + 4% and − 6%, while the strain corresponding to peak stress increased by 11% and 7%. The splitting tensile strength decreased by 14%, whereas the flexural tensile strength increased significantly by 12%. A more pronounced effect was observed for fracture energy, which increased significantly: Gf,δ by 20% and 143%, and Gf, CMOD by 20% and 33%. The increase in fracture energy may be associated with delayed microcrack initiation in the notch-tip zone, limited microcrack coalescence, and short-term load retention near the peak value, as confirmed by the flexural response curves and by the analysis of the evolution of the principal tensile strain ε₁ concentration zone. Scanning electron microscopy revealed only minor qualitative changes in fiber surface morphology after alkali treatment.

Impact of loading rate and elevated temperatures on the pull-out behaviour of inclined hooked-end steel fibres embedded in normal and high-strength concrete

Ultra-High Performance Concrete (UHPC) is an advanced construction material characterized by exceptional strength, durability, and ductility. This thesis presents a detailed analysis of UHPC including its properties, applications, and future scope in modern infrastructure. New types of concrete such as High Strength Concrete (HSC), High Performance Concrete (HPC), very high performance concrete (VHPC), Self Compacting Concrete (SCC), Ultra High Performance Concrete (UHPC) and Ultra- High Strength Concrete (UHSC) are being constantly developed in order to meet the increasing demand for improved mechanical properties and durability

High-strength concrete (HSC) exhibits excellent compressive strength but is inherently brittle, making it prone to sudden failure under dynamic or impact loads. The incorporation of polyethylene terephthalate (PET) flakes or fibers derived from recycled plastic bottles has emerged as a sustainable approach to enhancing the mechanical performance of HSC, particularly in terms of impact resistance and energy absorption. PET addition not only contributes to improved toughness and ductility but also promotes environmental sustainability by recycling post-consumer plastic waste. This review synthesizes recent advances (2023–2025) in PET-incorporated high-strength concrete, focusing on fresh properties, hardened mechanical properties, durability, microstructural interactions, and methods for evaluating impact resistance and energy absorption. Key durability tests such as water absorption, carbonation depth, density/unit weight, dry shrinkage, along with microstructural characterization techniques including X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR), are also discussed to understand the long-term performance of PET-enhanced HSC.

The effects of exposure to petroleum products (diesel and petrol) on the properties of normal-strength concrete (NSC), reactive powder concrete (RPC) and high-strength concrete (HSC) were investigated. Reductions in the mechanical characteristics of RPC specimens after exposure to petroleum products for 90 days were insignificant, while significant deterioration occurred in NSC and HSC specimens. Significantly, after exposing all the specimens to petroleum products for 180 days, all the mechanical characteristics of RPC, NSC and HSC specimens deteriorated. In contrast to NSC, oil products were unable to fully infiltrate the innermost part of RPC due to the presence of silica fume, which enhances concrete durability by forming a secondary gel and increasing its density by reducing pores. In addition, a very small amount of water is used in RPC. The impacts of diesel on the concrete characteristics were greater than the effects of petrol. The rates of increase in tensile strength, compressive strength, modulus of rupture and modulus of elasticity of the specimens increased gradually as the period of exposure to air was increased. In contrast, the rates of decrease in compressive and tensile strength gradually decreased with an increase in the immersion time in oil products.

This study investigates the shear behavior of high-strength concrete (HSC) beams with large circular web openings subjected to elevated temperatures. Internal (steel fibers at 0.5% and 1.0% by volume) and external (ferrocement jackets) retrofitting techniques were evaluated. Nine beams were experimentally tested, including solid control specimens, un-strengthened beams, and retrofitted beams. Exposure to 500°C resulted in a shear capacity reduction of up to 68% for beams with 150mm openings. After thermal exposure, steel fibers enhanced the residual shear strength by up to 16.4%, while ferrocement jackets achieved recovery levels of up to 14.5%. A parametric finite element study was conducted considering opening diameters ranging from 100 to 200mm and temperature levels between 400 and 600°C, demonstrating strong agreement with experimental results (average deviation ≤ 3%). The findings provide validated insights into the combined effects of geometric discontinuities and thermal degradation and support the development of effective retrofitting strategies for HSC beams under fire conditions.

Concrete is a versatile composite material widely used in both small- and large-scale construction due to its high compressive strength and availability. Increasing environmental concerns and demand for raw materials have encouraged the use of clay pozzolana as a partial replacement for cement. This study investigates the feasibility of substituting cement with clay pozzolana in proportions ranging from 0% to 25%. A slump test was conducted to evaluate fresh concrete properties, while mechanical properties such as compressive, tensile, and flexural strength were tested at 7, 28, and 56 days. Results showed that higher replacement levels reduced the induction period and setting times. Clay pozzolana improved microstructure and pore distribution, enhancing early hydration. Concrete mixes were prepared at a constant water-cement ratio of 0.35, and Poly Carboxylic Ether (PCE) admixture was used for performance improvement. Water absorption was measured at 28 days, and durability tests at 56 days. A cost comparison with M50 grade concrete indicated potential economic benefits. KEYWORDS: Clay Pozzolana, Cement Replacement, High-Strength Concrete, Poly Carboxylic Ether (PCE) & Hydration Process

The production of high-strength concrete (HSC) remains heavily dependent on cement and natural sand, despite the urgent need to reduce the carbon footprint of construction materials. Meanwhile, substantial quantities of palm oil fuel ash (POFA) and coal bottom ash (CBA) remain underutilized, and most existing studies treat ultrafine metakaolin (UFM), heated POFA (HPOFA), or CBA in isolation rather than as an integrated eco-concrete system. This study develops and evaluates an innovative HSC in which UFM and HPOFA serve as blended binders and CBA partially replaces natural fine aggregate. The main objective is to quantify the influence of ternary system on strength development relating to time, permeability, sulfate resistance and microstructural characteristics. A full factorial experimental program was conducted on HSC mixes containing 10–15% UFM, 20–30% HPOFA, and 0–20% CBA as fine aggregate. The results showed that 15% UFM maximizes compressive strength for binary blend, while a combined 15% UFM and 20% HPOFA is optimal for ternary blend. Overall, optimization of the UFM and HPOFA with CBA as fine aggregate system identified 10% UFM, 20% HPOFA and 10% CBA as the best-performing combination. The incorporation of 10–15% UFM with 20–30% HPOFA reduces permeability to 1.80–1.97 × 10−13 cm/s. The mixer containing 15% UFM and 20% HPOFA exhibits only 14.2, 8.6 and 11% reductions in compressive strength, tensile strength, and UPV, respectively, after 300 days of immersion in 5% Na2SO4 solution. Microstructural analysis confirms that UFM and HPOFA refine the pore structure, limit sulfate ion ingress, and diminish ettringite-induced microcracking. The life cycle assessment (LCA) indicates that mixes with 15% UFM and 30% HPOFA in the presence of 10–20% CBA achieve the lowest environmental impacts. The study offers mechanistic insights and practical mix-design guidance for regions with similar waste profiles and aggressive sulfate environments.

This study investigates the potential of hybrid natural pozzolanic materials, namely pumice and scoria powder, as partial cement substitutes in high strength concrete (HSC). By incorporating these materials at varying percentages (10%, 15%, 20%, 25% and 30% of cement weight) alongside a consistent superplasticizer dosage of 1.6%, the compressive strength, split tensile strength and Scanning electron microscopy analysis along with durability through strength loss after 30 days in sulfuric acid were tested. Compressive strength tests were used to evaluate performance at 28 days, and strength loss was measured after 30 days of exposure to sulfuric acid. The microstructure of the samples was examined using scanning electron microscopy. The findings showed that the HSC mixes HSC0, HSC10, HSC15, and HSC20 had respective compressive strengths of 63.02, 64.44, 62.07, and 60.30MPa. Pozzolanic activity was responsible for the improved performance at subsequent curing stages. The addition of pozzolanic elements enhanced acid resistance, with strength losses of 8.25%, 9.87%, and 12.93% for HSC0, HSC10, and HSC25, respectively. Notably, HSC0 had a denser calcium-silicate-hydrate (C-S-H) matrix. The results show that adding pumice and scoria to high-performance concrete as sustainable additives can have positive effects on durability and strength. Even though adding 20% pozzolanic material does not increase strength beyond 10%, it may still be taken into consideration for certain uses where other advantages like sustainability or the idea of green concrete are more important.

Investigation of production and performance evaluation of high-strength lightweight concrete (HSLWC) produced with regional volcanic aggregates (RVA)

This study investigates the axial compressive behavior of initially damaged recycled aggregate concrete (RAC) prisms confined with carbon fiber-reinforced polymer (CFRP). Monotonic compression tests evaluated the effects of the recycled aggregate replacement ratio, concrete strength, initial damage level, and the number of CFRP layers. Results indicate that CFRP confinement significantly enhances RAC load-bearing and deformation capacities. Conversely, increasing the replacement ratio reduces compressive strength, particularly in high-strength concrete. Initial damage negatively impacts axial performance by primarily reducing the turning point strength, an effect not fully mitigated by additional CFRP layers. Furthermore, a constitutive stress–strain model incorporating a damage evolution parameter was developed for 30 to 60 MPa structural-grade RAC. Although precise ultimate strain prediction remains intrinsically challenging due to stochastic premature CFRP rupture at square corners, the proposed model reasonably captures primary mechanical trends, providing an acceptable theoretical basis for structural rehabilitation.

Kaolinite based admixture for rapid hardening high strength concrete

The development of sustainable high-performance concrete has increasingly emphasized the incorporation of natural fibers to improve mechanical and impact resistance. This study presents a comprehensive and novel investigation of multiple natural fibers, coconut (0.5–1.5%), flax (0.1–0.5%), jute (0.15–0.55%), and bamboo, hemp, and kenaf (0.25–1.25%), evaluated in two concrete grades (M25 and M80). In addition to experimental assessment, probabilistic reliability modeling was integrated to characterize the stochastic nature of impact behavior in natural fiber-reinforced concrete (NFRC). Repeated impact testing in accordance with ACI 544-2R demonstrated that coconut fiber at 1–1.25% provided the highest impact resistance, increasing failure counts by 65% in M25 and 83% in M80 relative to the control concrete. Kenaf (0.75–1%) and bamboo (0.5–1%) exhibited moderate improvements of up to 20%, whereas jute, flax, and hemp produced comparatively modest gains of 5–10%. Despite substantial improvements in impact resistance, compressive strength remained comparable to that of the control concrete. Ductility indices and post-cracking ratios revealed distinct post-peak deformation mechanisms governed by fiber type, including pull-out, rupture, and interfacial slip. To further quantify performance differences, a grade–fiber synergy analysis was proposed to evaluate the interaction between concrete strength and fiber efficiency across grades. The probabilistic characterization of impact resistance was performed using Weibull statistics, supplemented by bootstrap resampling and Bayesian uncertainty analysis, enabling assessment of reliability and parameter stability. The results establish a reliability-based framework for optimizing NFRC formulations to improve structural resilience under dynamic loading.

Mechanism of shrinkage and cracking in high-strength concrete regulated by internal humidity under extreme drying environments

Preparation of high-strength artificial aggregate from alkali-activated yellow phosphorus slag and application in high-strength lightweight concrete

Prediction of Mechanical Properties of Quaternary Blended High Strength Concrete Exposed to Elevated Temperature and Aggressive Conditions Using a Transformer Based Regression Model.