Search Results (190)

Reinforced concrete (RC) deep beams constructed with low-strength concrete are susceptible to sudden splitting failures in the strut region due to shear–compression stresses. To mitigate this vulnerability, various strengthening techniques, including steel plates, fiber-reinforced polymer sheets, and cementitious composites, have been explored to confine the strut area. This study investigates the structural performance of RC deep beams with low-strength concrete, strengthened externally using an Engineered Cementitious Composite (ECC) layer. To ensure effective confinement and uniform shear distribution, shear reinforcement was provided at equal intervals with configurations of zero, one, and two vertical shear reinforcements. Four-point bending tests revealed that the ECC layer significantly enhanced the shear capacity, increasing load-carrying capacity by 51.6%, 54.7%, and 46.7% for beams with zero, one, and two shear reinforcements, respectively. Failure analysis through non-linear finite element modeling corroborated experimental observations, confirming shear–compression failure characterized by damage in the concrete struts. The strut-and-tie method, modified to incorporate the tensile strength of ECC and shear reinforcement actual stress values taken from the FE analysis, was used to predict the shear capacity. The predicted values were within 10% of the experimental results, underscoring the reliability of the analytical approach. Overall, this study demonstrates the effectiveness of ECC in improving shear performance and mitigating strut failure in RC deep beams made with low-strength concrete. Full article

This paper evaluates the synergistic effect of polyvinyl alcohol (PVA) fibers and nanosilica (nS) on the mechanical behavior and deformation properties of engineered cementitious composites (ECCs). ECCs have gained a reputation for high ductility, crack control, and strain-hardening behavior. Nevertheless, the next step is to improve their performance even more through nano-modification and fine-tuning of fiber dosage—one of the major research directions. In the experiment, six types of ECC mixtures were made by maintaining constant PVA fiber content (0.5, 1.0, 1.5, and 2.0%), while the nanosilica contents were varied (0, 1, 2, 3, and 5%). Stress–strain tests carried out in the form of compression, together with unrestrained shrinkage measurement, were conducted to test strength, strain capacity, and resistance to deformation, which was highest at 80 MPa, recorded in the concrete with 2% nS and 0.5% PVA. On the other hand, the mixture of 1.5% PVA and 3% nS had the highest strain result of 2750 µm/m, which indicates higher ductility. This is seen to be influenced by refined microstructures, improved fiber dispersion, and better fiber–matrix interfacial bonding through nS. In addition to these mechanical modifications, the use of nanosilica, obtained from industrial byproducts, provided the possibility to partially replace Portland cement, resulting in a decrease in the amount of CO₂ emissions. In addition, the enhanced crack resistance implies higher durability and reduced long-term maintenance. Such results demonstrate that optimized ECC compositions, including nS and PVA, offer high performance in terms of strength and flexibility as well as contribute to the sustainability goals—features that will define future eco-efficient infrastructure. Full article

Concrete structures increasingly face dynamic loading conditions, such as seismic events, vehicular traffic, and environmental vibrations, necessitating enhanced energy dissipation capabilities. The damping ratio, a critical parameter quantifying a material’s ability to dissipate vibrational energy, is typically low in conventional concrete, prompting extensive research into strategies for improvement. This review comprehensively explores the impact of advanced concrete types—such as Engineered Cementitious Composites (ECCs), Ultra-High-Performance Concrete (UHPC), High-Performance Concrete (HPC), and polymer concrete—on enhancing the damping behavior. Additionally, key mix design innovations, including fiber reinforcement, rubber powder incorporation, and aggregate modification, are evaluated for their roles in increasing energy dissipation. External factors, particularly curing conditions, are also discussed for their influence on the damping performance. The findings consolidate experimental and theoretical insights into how material composition, mix design, and external treatments interact to optimize dynamic resilience. To guide future research, this paper identifies critical gaps including the need for multi-scale numerical simulation frameworks, standardized damping test protocols, and long-term performance evaluation under realistic service conditions. Advancing work in material innovation, optimized mix design, and controlled curing environments will be essential for developing next-generation concretes with superior vibration control, durability, and sustainability. These insights provide a strategic foundation for applications in seismic-prone and vibration-sensitive infrastructure. Full article

This study investigates the feasibility of pumice-based internal curing based on the 3D printability of engineered cementitious composites (ECCs) for water-scarce environments and arid regions. Natural river sand was partially replaced with the presoaked pumice lightweight aggregates (LWAs) at two different levels, 30% and 60% by volume, and 50% of the cement was replaced with slag to enhance sustainability. Furthermore, 2% polyethylene (PE) fibers were used to improve the mechanical characteristics and 1% methylcellulose (MC) was used to increase the rheological stability. Pumice aggregates, presoaked for 24 h, were used as an internal curing agent to assess their effect on the printability. Three ECC mixes, CT-PE2-6-10 (control), P30-PE2-6-10 (30% pumice), and P60-PE2-6-10 (60% pumice), were printed using a 3D gantry printing system. A flow table and rheometer were used to evaluate the flowability and rheological properties. Extrudability was measured in terms of dimensional consistency and the coefficient of variation (CV%) to evaluate printability, whereas buildability was determined in terms of the maximum number of layers stacked before failure. All of the mixes met the extrudability criterion (CV < 5%), with P30-PE2-6-10 demonstrating superior printing quality and buildability, having 16 layers, which was comparable with the control mix that had 18 layers. Full article

Freeze–thaw damage is a critical durability challenge in cold climates that leads to surface spalling, cracking, and degradation of structural performance. In northern China, the severity of winter conditions further accelerates the degradation of concrete infrastructure. This study investigates the reinforcement of frost-damaged concrete using engineered cementitious composites (ECC) prepared with Yellow River sedimentary sand (YRS), employed as a 100% mass replacement for quartz sand to promote sustainability. The interface bonding performance of ECC-C40 specimens was evaluated by testing the impact of various surface roughness treatments, freeze–thaw cycles, and interface agents. A multi-factor predictive formula for determining interface bonding strength was created, and the bonding mechanism and model were examined through microscopic analysis. The results show that ECC made with YRS significantly improved the interface bonding performance of ECC-C40 specimens. Specimens treated with a cement expansion slurry as the interface agent and those subjected to the splitting method for surface roughness achieves the optimal reinforced condition, exhibited a 27.57%, 35.17%, 43.57%, and 42.92% increase in bonding strength compared to untreated specimens under 0, 50, 100, and 150 cycles, respectively. Microscopic analysis revealed a denser interfacial microstructure. Without an interface agent, the bond interface followed a dual-layer, three-zone model; with the interface agent, a three-layer, three-zone model was observed. Full article

This paper reviews the applications and performance advantages of ultra-high-performance concrete (UHPC), engineered cementitious composite (ECC), and recycled aggregate concrete (RAC) in composite flexural members. UHPC is characterized by its ultra-high strength, high toughness, excellent durability, and microcrack self-healing capability, albeit with high costs and complex production processes. ECC demonstrates superior tensile, flexural, and compressive strength and durability, yet it exhibits a lower elastic modulus and greater drying shrinkage strain. RAC, as an eco-friendly concrete, offers cost-effectiveness and environmental benefits, although it poses certain performance challenges. The focus of this review is on how to enhance the load-bearing capacity of composite beams or slabs by modifying the interface roughness, adjusting the thickness of the ECC or UHPC layer, and altering the cross-sectional form. The integration of diverse concrete materials improves the performance of beam and slab elements while managing costs. For instance, increasing the thickness of the UHPC or ECC layer typically enhances the load-bearing capacity of composite beams or plates by approximately 10% to 40%. Increasing the roughness of the interface can significantly improve the interfacial bond strength and further augment the ultimate load-bearing capacity of composite components. Moreover, the optimized design of material mix proportions and cross-sectional shapes can also contribute to enhancing the load-bearing capacity, crack resistance, and ductility of composite components. Nevertheless, challenges persist in engineering applications, such as the scarcity of long-term monitoring data on durability, fatigue performance, and creep effects. Additionally, existing design codes inadequately address the nonlinear behavior of multi-material composite structures, necessitating further refinement of design theories. Full article

The integration of fiber-reinforced cementitious composites (FRCCs) with fiber-reinforced polymer (FRP) bars represents a significant advancement in concrete technology, aimed at enhancing the structural performance of reinforced concrete elements. The incorporation of fibers into cementitious composites markedly improves their mechanical properties, including tensile strength, ductility, compressive strength, and flexural strength, by effectively bridging cracks and optimizing load distribution. Furthermore, FRP bars extend these properties with their high tensile strength, lightweight characteristics, and exceptional corrosion resistance, rendering them ideal for applications in aggressive environments. In recent years, there has been a notable increase in interest from the engineering research community regarding this topic, primarily to solve the issues of aging and deteriorating infrastructure. Researchers have conducted extensive investigations into the structural performance of FRCC and FRP composite systems. This paper presents a systematic literature review that surveys experimental and analytical studies, findings, and emerging trends in this field. A comprehensive search on the Web of Science identified 40 relevant research articles through a rigorous selection process. Key factors of structural performance, such as bond behavior, flexural behavior, ductility performance assessments, shear and torsional performance, and durability evaluations, have been documented. This review aims to provide an in-depth understanding of the structural performance of these innovative composite materials, paving the way for future research and development in construction materials technology. Full article

This study applied precast engineered cementitious composite (ECC) shells to replace conventional concrete in precast assembled monolithic composite beams to enhance mechanical performance. A new type of precast monolithic ECC composite beam was proposed. Five ECC composite beams and one reinforced concrete (RC) composite beam were designed and fabricated for the experimental study. The failure pattern, failure mechanism, load-bearing capacity, deformability, and stiffness degradation were quantitatively analyzed through the tests. The main findings were as follows: ECC composite beams developed finer and more densely distributed cracks compared to RC composite beams, without significant concrete spalling. The peak load of ECC composite beams was 8.2% higher than that of RC composite beams, while the corresponding displacement at peak load increased by 29.3%. The ECC precast shell delayed crack propagation through the fiber bridging effect. The average load degradation coefficient of the ECC composite beams was 8.2% lower than that of the RC beam. The stiffness degradation curve of ECC composite beams was more gradual than that of RC composite beams, providing an optimization basis for the design of precast beams in structures with high seismic demands. As the shear span ratio increased from 1.5 to 3, the load-bearing capacity decreased by 32.0%. When the stirrup ratio increased from 0.25% to 0.75%, the ultimate load-bearing capacity improved by 28.8%. Furthermore, specimens with higher stirrup ratios showed a 40–50% reduction in stiffness degradation rate, demonstrating that increased stirrup ratio effectively mitigated brittle failure. Full article

Engineered cementitious composites (ECCs), known for their superior ductility and strain-hardening behavior compared to conventional concrete, have been predominantly studied with polyvinyl alcohol (PVA) fibers. However, the potential economic and technical advantages of incorporating steel fibers into ECCs have been largely overlooked in the literature. This study investigates the mechanical performance of ECC reinforced with different types of steel fibers, including straight, twisted, hooked, and hybrid fibers of different lengths, as compared to PVA. The inclusion of various supplementary cementitious materials (SCMs) such as slag and fly ash with each type of steel fiber was also considered at a constant fiber volume fraction of 2%. The mechanical properties were assessed through compressive strength, splitting tensile strength, and four-point flexural tests along with calculations of toughness, ductility, and energy absorption capacity indices. This study compares the mechanical properties of different ECC compositions, revealing that ECCs with hybrid steel fibers (short and long) achieved more than twice the tensile strength, 12.7% higher toughness, and 36.4% greater energy absorption capacity compared to ECCs with PVA fibers, while exhibiting similar multiple micro-cracking behavior at failure. The findings highlight the importance of fiber type and distribution in enhancing an ECC’s mechanical properties, providing valuable insights for developing more cost-effective and resilient construction. Full article

This study explores the impact of thermal cycling and rubber particle content on the static and dynamic compressive properties of rubber–polyethylene fiber-reinforced engineered cementitious composites (RPECC). Through static and dynamic compression tests, supplemented by scanning electron microscopy and energy-dispersive X-ray spectroscopy, the mechanical behavior and microstructural evolution of RPECC under thermal cycling were analyzed. Results indicate that increasing rubber content from 10% to 30% enhances toughness and strain capacity but reduces the static compressive strength of ECC by up to 17.9% at 30%. Thermal cycling reduced strength: static and dynamic compressive strengths decreased by 18.0% and 41.2%, respectively, after 270 cycles. Dynamic tests demonstrated that RPECC is sensitive to strain rate. For example, C-20 specimens exhibited increases in dynamic strength of 6.9% and 9.9% as strain rate rose from 60.2 s⁻¹ to 77.4 s⁻¹ and 110.8 s⁻¹, respectively, and the dynamic increase factor correlated linearly with strain rate. By contrast, excessive rubber content (30%) diminishes dynamic strengthening, indicating that 20% rubber is optimal for enhancing strain rate sensitivity. Thermal cycling facilitates the formation of hydration products, such as calcium hydroxide, and creates interfacial defects, further deteriorating mechanical performance. These findings provide a reliable foundation for optimizing RPECC mix design and ductility in environments subject to temperature fluctuations and dynamic loading. Full article

This paper investigates the effects of the basalt-fiber-reinforced polymer (BFRP) and polyethylene (PE) hybrid fiber ratio on the mechanical properties and durability of engineered cementitious composites (ECC). First, four different PE-BFRP hybrid fiber ECC mixtures were systematically prepared by controlling the fiber volume ratio of PE and BFRP fibers. The workability and mechanical properties of the hybrid fiber ECC (HFECC) were then evaluated using flowability tests and multi-scale mechanical tests, including compressive strength, flexural strength, bending toughness, and tensile performance. After that, the durability of HFECC with different fiber ratios was comprehensively assessed through freeze–thaw cycle tests and rapid ion migration tests. Finally, the interface morphology of fibers within the matrix was observed using scanning electron microscopy (SEM). The results show that an appropriate hybrid of PE and BFRP fibers can synergistically enhance the crack resistance and toughness of ECC, improving its failure mode. The best performance in terms of flowability and mechanical properties was observed for the HFECC mixture with 1.30% PE fiber volume and 0.30% BFRP fiber volume. With the increase in BFRP fiber content, the freeze–thaw resistance and chloride ion erosion resistance of HFECC were gradually enhanced. This study provides experimental and theoretical support for the design and engineering application of high-performance hybrid fiber ECC materials. Full article

Engineered cementitious composites (ECCs) exhibit superior mechanical properties (MPs) and excellent crack control capabilities, making them widely used in practical engineering applications. However, the MPs of ECCs in frozen states (FSs), particularly their flexural properties (FPs), still need to be better understood. MP tests were designed for frozen ECC samples to investigate the service performance of ECCs in an FS. The samples underwent 0 to 300 freeze–thaw cycles (FTs), followed by compressive and flexural tests at a constant freezing temperature of −18 °C. The compressive properties (CPs) and FPs of the samples and their influencing mechanisms were analyzed. Based on this analysis, a life prediction model (LPM) for freeze–thaw-damaged (FTD) ECCs was established using the entropy weight method and the GM(1,1) model to predict the durability changes of ECCs in FS. The results indicate that with an increasing number of FTs, the uniaxial compressive strength (CS), elastic modulus (E), initial crack strength, and ultimate strength of ECCs in the FS are higher than those in the thawed state (TS), with a notable increase in brittleness at ultimate failure. The overall stiffness of the specimens increased under high FTs. The established model effectively predicts the durability changes of ECCs in the FS. Full article

In order to enhance the durability of concrete frame beams, a U-shaped engineered cementitious composites (ECC) protective layer is applied at the end of the frame beams. The bond between the ECC protective layer and the concrete is reinforced by incorporating notches and grooves in the occupancy plate. The development and resistance to cracking of reinforced concrete (RC) frame beams and frame beams with an ECC protective layer were investigated using monotonic loading tests. The test results show that the average value of crack spacing in the negative moment zone of the RC frame beam specimen is in close agreement with the crack spacing calculated according to the GB50010 Code for Design of Concrete Structures. While the dispersion of crack width in the negative moment zone of the RC frame beam specimens is considerable, the distribution pattern of crack width undergoes a gradual change with increasing load. When the maximum crack width calculation method of GB50010 is employed in the negative moment zone of RC frame beams, the crack width should be increased by approximately 1.25 times. Furthermore, the crack spacing and crack width of the ECC protective layer are markedly smaller than those of RC frame beams. Full article

Engineered Cementitious Composite (ECC) has emerged as a promising solution with which to address the longstanding challenge of cracking in the tensile zone of reinforced concrete beams. This study conducts an experimental and analytical exploration of the flexural performance of ECC-concrete composite beams reinforced with hot-rolled ribbed steel bars. Sixteen beams, featuring diverse reinforcement ratios and ECC layer thicknesses, underwent rigorous testing through a four-point bending setup. The experimental findings underscore a substantial improvement in crack resistance and flexural bearing capacity of ECC-concrete composite beams reinforced with steel bars. Building on these results, a theoretical model was formulated to predict the moment-deflection responses of ECC-concrete composite beams incorporating steel bars. Furthermore, practical and simplified methods were introduced to predict flexural bearing capacity and effective moment of inertia, as well as anticipate failure modes, offering a user-friendly approach for engineering applications. Validation of the proposed approaches was achieved through simulation results, demonstrating a high degree of accuracy when compared with the experimental outcomes. Moreover, the average crack width at serviceability limit states of composite beams was sensitive to specimen size and the yield strength of steel bars, and a size effect was also observed for ductility expressed as deflection. Full article

Engineering Cementitious Composites (ECC) has gained significant attention in civil engineering due to its excellent tensile strength, crack width control capability, and remarkable ductility. This study examines the influence of the ECC strength and reinforcement on the flexural behavior of ECC slabs through four-point flexural tests. The results demonstrate that ECC is well suited for flexural applications. During flexural tests, the fibers within the ECC provide a bridging effect, allowing the ECC in the tensile zone to sustain a load while developing a dense network of fine microcracks at failure. This characteristic significantly enhances the crack resistance of ECC slabs. Despite the relatively low flexural capacity of unreinforced ECC slabs, they achieve 59.2% of the capacity of reinforced ECC slabs with a reinforcement ratio of 1.02%, demonstrating the potential for using unreinforced ECC in low-load-bearing applications. Further findings reveal that high-strength ECC (HSECC) not only improves the flexural capacity of unreinforced ECC slabs but also maintains excellent ductility, enabling a better balance between the load-bearing capacity and deformation ability. However, while reinforcement enhances both the flexural capacity and energy absorption, an excessively high reinforcement ratio significantly compromises ductility. Additionally, this study proposes a simplified calculation method for the flexural capacity of ECC slabs based on the axial force and moment equilibrium, providing theoretical support for their design and application. Due to their excellent flexural behavior, ECC slabs exhibit significant potential for use in flexural components such as bridge deck slabs and link slabs in simply supported beam bridges. With continued research and optimization, their application in engineering practice is expected to become more widespread, thereby improving the cracking resistance and durability of concrete structures. Full article