Materials and Structures最新文献

The phase assemblage evolution of binders with novel supplementary cementitious materials (SCM_S) during exposure to adverse environments needs to be quantified to accelerate their adoption, and further optimize binder formulation. As such, the interaction between chloride and cementitious matrices with novel SCMs needs to be quantified. The goal of workgroup 2 of RILEM TC EBD-298 is to assess the methods used to quantify chloride binding. This state-of-the-art report reviews the standardized and novel methods to measure chloride binding through an average content (acid/water soluble) or a specific bound content per phase (XRD, TGA, SEM–EDS, …). Each method is presented with respect to our current understanding of chloride binding and speciation in cementitious materials. The discussion around the purpose, use and reporting of each method highlights the gaps limiting the comparison between studies, in particular the lack of standard protocol, and complementary characterization. This review is the groundwork for a “cookbook” of experimental workflows to investigate chloride binding in modern cementitious binders.

An innovative steel reinforced concrete frame with replaceable high damping concrete wall (SRC-HDCW) is proposed. The HDCW contains a polyvinyl alcohol fiber-reinforced rubber concrete wall panel and ten fuses made by low yielding point (LYP) steel. Two SRC-HDCWs are designed for the quasi-static cyclic test, in which the one is directly loaded to overall failure to verify its seismic performance. The other one is repaired by installing a new set of HDCW when it reaches the limit value of elastic–plastic story drift. The earthquake-resilient behavior is demonstrated through the rehabilitation in bearing capacity and stiffness. The failure mode, yielding pattern, hysteretic characteristics and ductility are analyzed. According to the features of obtained skeleton curve and hysteretic loop, a restoring force model based on quadri-linear skeleton curve as well as the corresponding hysteretic rule is proposed. The shear capacity and the initial stiffness of this hybrid structure are deduced. The relationship between initial stiffness and its degeneration at loading (unloading) path is fitted, in which the pinching behavior is considered. The predicted hysteretic curves are found to agree closely with those of the experimental specimens.

Rutting is a severe distress that significantly compromises the durability and service life of asphalt pavements. To clarify the creep failure mechanism of bitumen and enable accurate and practical failure time prediction, this study investigated the influence of viscoplastic deformation on the rutting performance and failure behavior of bitumen through long-term creep tests. For the first time, an Eyring’s activated flow model was applied in conjunction with the time–temperature superposition principle to accurately characterize the viscoplastic flow behavior of bitumen. A novel rutting failure criterion based on the unrecoverable deformation observed in the creep and recovery test was proposed to predict the rutting failure of bitumen under varying stress and temperature conditions in long-term creep tests. The consistent relationship between the plastic creep rate and failure time observed in both bitumen across varying temperatures indicates that the rutting failure is predominantly governed by a plasticity-controlled mechanism. Eyring’s activated flow rule effectively captures the evolution of viscoplastic flow in bitumen under varying stress and temperature conditions, while the time–temperature superposition principle proves effective in developing master curves across a wide temperature range. The proposed failure criterion demonstrates high accuracy in predicting the failure time of long-term creep tests. Moreover, the parameters governing bitumen failure were found to be insensitive to temperature variations. This study provides a robust foundation for developing predictive tools that remain reliable under diverse environmental conditions.

Many studies have employed the Alternate Load Path method to investigate the progressive collapse of building structures, yet they often neglect the influence of blast loads, which leads to inaccurate predictions of buildings structures progressive collapse mechanism. In this paper, a comparative experimental analysis was conducted on six reinforced concrete substructures subjected to explosion loads and one ALP-designed benchmark structure to examine their progressive collapse mechanism. The results indicated that the column-end force–time curves of the rubber test device exhibited higher peak forces with shorter durations, whereas those of the airbag test device showed lower peak forces but longer durations. The initial blast-induced damage in the substructures significantly reduced their rotational resistance capacity and accelerated the premature fracture of longitudinal reinforcements at beam ends. Consequently, the blast-damaged substructures exhibited a worse ductility performance compared with the benchmark structure. Moreover, during static pushdown loading, the vertical deformation profile of the benchmark substructure evolved from a double-curved shape to a straight line, while the blast-damaged substructures deformed primarily in a straight-line mode from the outset due to initial blast damage. These findings might provide valuable experimental evidence and design insights for enhancing the blast resistance design and progressive collapse analysis of building structures.

To address the anchor challenges of CFRP tendons used as cables, this study investigates the fatigue performance of a bonded CFRP tendon anchor system employing a three-segment anchorage design. Fatigue tests were conducted under a maximum stress of 0.5 (f_{u}) and stress ranges between 500 and 800 MPa. The fatigue failure mechanism was analyzed based on the bond–slip behavior between the CFRP tendon and the bonding medium. The effects of cyclic loading on tendon and sleeve stress, bond stress evolution in the anchor zone, and tendon stiffness were also evaluated. The results indicate that the anchor system withstood 2 million cycles under a 500 MPa stress range at 0.5 (f_{u}) maximum stress. Fatigue life was influenced by the stress range, with failure modes shifting from tendon splitting to tendon slippage as the stress range increases. Tendon axial strain progressively decreased and then stabilized with loading cycles, accompanied by a 22% increase in axial stiffness after 2 million cycles. The steel sleeve exhibited a slight increase in axial strain under cyclic loading, though the associated stress levels and amplitudes remained low. Within the anchor zone, bond stress and its amplitude were highest near the loading end, and bond stress within the tensioning end anchorage exceeded that in the fixed end. Fatigue failure initiated at the bonded interface near the loading end and propagated toward the free end, ultimately leading to global tendon slippage. Based on the fitted S–N curve, a stress range below 365 MPa is recommended for the three-segment anchor system with a fatigue lifespan exceeding 100 million cycles.

The aging of bituminous binders is a complex process that is influenced by a number of environmental factors including temperature, sunlight, humidity and reactive oxygen species (ROS) found in the troposphere. The effect of two of these factors, humidity and reactive oxygen species (ROS), are investigated in an environmental aging setup called the Viennese Binder Aging (VBA) method. Three unmodified and one polymer modified binder (PmB) were aged under conditions of varying duration (2 and 3 days), water exposure modes (direct versus indirect) and humidity levels. Additionally, experiments were conducted without the incorporation of ROS. Fourier transform infrared (FTIR) spectroscopy and Dynamic Shear Rheometer (DSR) were used for analysis. One binder showed accelerated aging due to the combination of ROS and humidity. Furthermore, a marginal increase in polybutadiene degradation due to humidity was detectable. However, when ROS were removed from the test setup, increasing the humidity levels did not increase the aging of any of the binders. The fact that the synergistic effects of humidity and ROS only affected the aging of one of the binders shows the complexity of this matter and highlights the importance of incorporating environmental factors into laboratory aging.

In this study, 3D numerical models for fresh concrete are established based on computational fluid dynamics (CFD) and discrete element method (DEM), respectively, and the comparative analysis is conducted to explore their advantages and characteristics in simulating the flowability of fresh concrete. To validate the reliability of proposed models, the simulated results are compared with experimental data obtained from this paper and other literature. According to the applicability of each numerical method, the influence of rheological parameters and coarse aggregate properties on the flowability of fresh concrete is further investigated. The findings indicate that both CFD and DEM models are capable of accurately predicting the flowability of fresh concrete, as evidenced by the strong correlation between the simulated and experimental results. The CFD model provides valuable insights into the rheological mechanisms governing the flow behavior of fresh concrete, while the DEM model excels at capturing the influence of constituent material properties. Within the specified ranges of yield stress (200–350 Pa) and plastic viscosity (30–60 Pa·s), an increase in the rheological parameters of the concrete mixture results in a decrease in both slump and slump flow. The relationship between coarse aggregate particle size and flowability is found to be non-monotonic, with slump and slump flow initially increasing and then decreasing as the maximum particle size increases from 16 to 31.5 mm. Additionally, when the density of coarse aggregates increases from 2.3 to 2.9 g/cm³, both slump and slump flow exhibit an increasing trend.

Growing concerns about the environmental impact of modern construction materials, particularly concrete, have renewed interest in earth-based construction. While chemical binders like cement and lime are commonly used to improve strength and durability, they increase embodied energy and limit recyclability. As a promising sustainable alternative, Enzyme-Induced Calcite Precipitation (EICP) enhances mechanical performance through calcium carbonate precipitation. However, its application to fine-grained soils remains limited, particularly regarding the influence of curing conditions and environmental factors on performance. This study explores EICP stabilization of compacted raw earth using soybean-derived urease in juice (SJ) and fine powder (SP) form, focusing on the effects of curing temperature (25 °C, 40 °C and 60 °C) and relative humidity RH (30%, 50% and 90%) on the mechanical performance and durability against water erosion. Results show that highest strength is reached at 25 °C and at 60 °C for SP and SJ stabilized samples, respectively. SP-stabilized samples showed no erosion in drip tests under all conditions except at RH = 90%, where erosion depth reached 2.88 mm. SJ samples instead were less erosive when cured at 60 °C, with an erosion depth of 3.35 mm. Results finally showed that drier samples (equalized at RH = 30%) are stronger and stiffer for both SJ and SP stabilizations. These findings underscore the critical role of curing conditions—specifically temperature and relative humidity—in the efficiency of EICP stabilization. They also demonstrate that the suction concept, widely accepted for unsaturated soils, remains applicable to EICP-stabilized soils, which are engineered materials incorporating calcium carbonate crystals and soybean-derived organic matter.

The demand for sustainable, energy-efficient buildings has accelerated the development of eco-efficient materials such as earth-based mortars (EBMs) reinforced with plant-based additives. This study investigates the impact of incorporating bamboo particles (0, 3, 6, and 9 vol%) on the hygrothermal, mechanical, and environmental performance of EBMs intended for interior wall render/plaster (non-structural). Bamboo particles were characterized by water absorption, bulk density, scanning electron microscopy (SEM), and moisture buffer value (MBV). The mortars were evaluated using mercury intrusion porosimetry (MIP), MBV, water vapor permeability (WVP), thermal conductivity, bulk density, compressive and flexural strength, post-peak toughness, and a cradle-to-site life cycle assessment (LCA; A1–A4) with eco-efficiency indicators. Bamboo addition decreased bulk density (up to ≈ 14%) and thermal conductivity (up to ≈ 30%), while enhanced MBV (up to ≈ 41%) and WVP generally increased within the tested range, and MIP/SEM indicated a more open pore network and modified interfacial bonding. Capillary absorption and drying index increased, indicating greater porosity and improved vapor diffusion. At higher bamboo contents, compressive strength was reduced, whereas post-peak toughness and crack resistance improved, with clear post-peak gains. LCA results were largely driven by hydrated lime and cement, while biogenic carbon associated with bamboo partially offset climate burdens. Overall, eco-efficiency improved on hygrothermal axes with application-dependent trade-offs on mechanical performance, consistent with the non-structural nature of interior plasters. These results highlight the potential of bamboo-reinforced earth mortars as low-carbon, moisture-regulating materials for interior application and climate-resilient building. The scientific contribution lies in combining microstructural evidence (MIP/SEM), multi-domain performance tests and LCA into quantitative eco-efficiency indicators, with explicit consideration of biogenic carbon to quantify carbon-performance trade-offs of bamboo in EBMs.

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