Materials and Structures最新文献

Water absorption in earthen structures can frequently lead to irreversible damage. Moisture can penetrate these materials through driving rain, flooding, or capillary rise. Improving the durability of earthen materials is essential to encourage the use of earth-based construction techniques. Unlike conventional stabilizers such as cement or lime, biopolymers are derived from organic matter, have a lower carbon footprint, and can potentially be recycled. To assess their effectiveness, imbibition tests were carried out with increasing hydric solicitations to provide data on the absorption kinetics of bio-stabilized samples. Both non-stabilized and stabilized samples (with the addition of tannin, lignin sulphonate, and wool) were mechanically tested after undergoing capillary rise and their cohesiveness was assessed by immersion. The water absorption coefficient (A-value) was determined for all rammed earth (RE) samples, together with the maximum compressive stress measured through unconfined compressive strength (UCS) tests. The results showed low A-values for lignin sulphonate stabilized RE samples. Tannin stabilization significantly improved cohesiveness when samples were immersed in water and resulted in a fourfold increase in compressive strength. This research highlights the potential of using tannin to stabilize earthen materials, particularly to improve their water resistance.

This study presents a multi-method framework for the tensile characterization of Ultra-High Performance Concrete (UHPC) with enhanced autogenous healing capacity, developed to reflect realistic service-life conditions. The primary objective is to assess the reliability and compatibility of different test methods for identifying tensile constitutive behaviour in self-healing UHPC. To this end, a UHPC mix containing crystalline admixtures was cast on-site, then cut into thin beams and double-edge wedge splitting (DEWS) specimens. These were pre-cracked, subjected to sustained deformation using external bracing, and exposed to various environmental conditions. Tensile performance was evaluated through DEWS, direct tension (DT), and four-point bending (4PB) tests, with simplified inverse analysis used to extract tensile laws from 4PB data. Results showed a consistent, though modest, increase in tensile strength over time across all methods except DEWS specimens with narrow initial cracks, where early healing limited further evolution. DEWS and inverse analysis provided comparable results, while DT tests were more affected by residual deformation and exhibited lower values and greater scatter. Statistical comparisons using Bland–Altman analysis and Deming regression confirmed the robustness of DEWS and 4PB methods and identified systematic deviations in DT measurements. While the methodology shows strong potential for application in structural-scale UHPC assessment, further validation with a broader dataset and different UHPC formulations is necessary to ensure generalizability and refine its predictive capabilities.

Managing ash from biomass combustion is a significant environmental challenge, while the construction industry is increasingly seeking sustainable alternatives to traditional, energy-intensive binders. This study evaluates the potential of two types of biomass ash (BA-a and BA-b) as eco-friendly stabilizing agents for making compressed earth bricks (CEBs), focusing on how hygrothermal curing conditions influence their long-term performance. The experimental program involved adding these ashes in different proportions (0, 5, 10, 15, and 20% by weight) into soil to produce stabilized CEBs, labeled BBA-a(X%) and BBA-b(X%). The specimens were cured under controlled hygrothermal conditions (40 °C and 100% RH) for 7, 28, 60, and 180 days, then tested for mechanical, thermal, and durability properties. The results reveal different behaviors depending on the type of biomass ash used. BA-b exhibits strong pozzolanic activity, significantly improving mechanical performance, with a maximum compressive strength of 33.34 MPa at 180 days for 20% addition, compared to 11.60 MPa for the control bricks at the same age. Conversely, BA-a primarily enhances thermal performance, achieving a thermal conductivity as low as 0.722 W/m·K at 20% addition after 180 days, versus 0.952 W/m·K for the control bricks. The data clearly demonstrate the gradual activation of pozzolanic reactions under hygrothermal curing, with notable performance enhancements between 28 and 180 days. This study highlights the positive impact of hygrothermal conditions in accelerating the development of mechanical and thermal properties in biomass-ash-stabilized CEBs. Overall, the findings support using biomass ashes as effective, eco-friendly stabilizers for producing high-quality CEBs, especially suitable for construction in hot and humid environments.

Textile-reinforced mortar (TRM) has emerged as a promising technique for retrofitting masonry structures due to its distinct advantages over traditional methods, such as increased strength and deformation capacity, improved crack resistance, and enhanced durability. This paper presents a comprehensive review of TRM technologies, highlighting their advantages over traditional fibre-reinforced polymer (FRP) systems, including improved fire resistance, reversibility, and compatibility with historic substrates. This paper also provide insights into the current state of knowledge, reviews the benefits, practical limitations, and future potential of TRM in retrofitting applications. The benefits include its lightweight nature, ease of application, and compatibility with various substrate materials, making it suitable for a wide range of masonry structures. Practical limitations, such as the need for skilled application and concerns over long-term performance, are also discussed critically. Lastly, the study explores recent innovations in textile materials and eco-friendly mortars, emphasizing the role of TRM in advancing sustainable construction practices. By identifying current challenges and future research directions, this work aims to support the broader adoption of TRM systems in both heritage conservation and modern structural engineering.

This review provides a comprehensive analysis of recent research on the incorporation of natural polysaccharides (NPS) into unfired clay-based materials (UCBM). It explores the interactions between polysaccharides and clay, highlighting their influence on the overall performance of UCBM. Additionally, the review examines the fundamental mechanisms governing the interactions among clays, water, and polysaccharides. By assessing the effect of different NPSs on UCBM, this study highlights their versatility, potential advantages, and possible applications of such materials. The findings highlight the potential of NPS as effective modifiers for improving the performance of UCBM.

This study employed a multi-scale approach to investigate the impact of aging on the physicochemical composition and interfacial adhesion behavior within asphalt-aggregate systems. Combining laboratory experiments with molecular dynamics (MD) simulations, it systematically characterized the evolution of virgin asphalt, short-term and long-term aged asphalt. The experimental techniques included saturate, aromatic, resin, and asphaltene (SARA) fractionation, gel permeation chromatography (GPC), elemental analysis, and atomic force microscopy (AFM). The results show oxidative aging promotes asphalt hardening through increased oxygen content and growth in large molecular-size fractions. Aggregates (albite, calcite) exhibit enhanced interfacial adhesion owing to intensified electrostatic interactions, with the adhesion work sequence being albite > calcite > quartz. These alkaline aggregates impose a greater inhibition effect on molecular diffusion. While short-term aging increased adhesion work (69.89% increase with albite) through enhanced molecular polarity and pull-off tensile strength (POTS) by 2.44–3.81%. Long-term aging caused POTS reductions of 3.74–8.55%, the further increase in simulated adhesion work unravels the underlying discrepancy between the molecular-scale adhesion energy and macroscopic mechanical behavior. Z-axis concentration profiles confirmed aging-induced accumulation of polar molecules towards aggregate surfaces, with higher aggregation density on albite than quartz, providing a molecular-scale explanation for reinforced interfaces from a mobility perspective. This study bridges molecular-scale mechanisms with macroscopic performance, providing insights for optimizing asphalt-aggregate interfaces in pavement durability.

In this paper, Engineered Cementitious Composites were prepared by using recycled concrete fine aggregate instead of natural sand using Response Surface Method (RSM). Box-Behnken Design (BBD) was used to construct recycled fine aggregates engineered cementitious composites (ECC) by using different regenerated fine aggregates (RFA) replacement rate (λ), water-binder ratio (w_eff/c) and PE fiber volume content (V_PE). Based on the regression analysis of the above three indices, the RFA-ECC mix ratio design was optimized, and a systematic RFA-ECC mix ratio design method was proposed. At the same time, RFA was modified using a solution containing Na₂O·nSiO₂, HCl, and SiH₄. The results show that λ is the main factor affecting the mechanical properties of RFA-ECC, followed by w_eff/c, and V_PE is the least. When λ is 50%, w_eff/c is 0.28, V_PE is 2%, the specimens have good mechanical properties. The modification results show that Na₂O·nSiO₂ has the most obvious strengthening effect on RFA, followed by HCl, and the effect of SiH₄ is relatively general. The microscopic analysis results showed that the presence of RAF did not change the properties of the bonding interface between fiber and matrix.

This study investigates the multifunctional performance of cement mortars modified with microparticles of boron oxide (B₂O₃), lead oxide (PbO), bismuth oxide (Bi₂O₃), and tungsten oxide (WO₃) at varying dosages (1-5 wt.%), with a goal to improve mechanical strength, thermal fatigue resistance, and radiation shielding against both primary and secondary products. Among all additives, mortar modified with 3 wt.% PbO exhibited the highest 28-day compressive strength of 47.6 MPa (55.56% more than the control) due to its dense particle packing. WO₃ addition resulted in a 35.94% increase in strength at 2 wt.%, attributed to its fibrous morphology and improved matrix interlocking. Under thermal fatigue testing, WO₃-modified mortars exhibited superior durability with only 12.36% strength loss after 400 cycles, compared to 20.26% for the control. Radiation shielding study revealed that 2 wt.% B₂O₃ achieved the lowest Total Effective Dose Rate (TEDR) of 17.20 mSv/min, a 70.88% reduction compared to the control. WO₃ also showed balanced shielding effectiveness (TEDRs: 26.43-28.27 mSv/min). Microstructural analysis confirmed the inert nature of PbO, Bi₂O₃, and WO₃, while B₂O₃ exhibited chemical interaction, forming boric compounds. WO₃ emerged as the most balanced additive, offering a synergistic enhancement of structural integrity, durability, and comprehensive radiation protection under realistic mixed-field conditions.

Based on problems in actual engineering construction, this paper utilized the coupling smoothed particle hydrodynamics (SPH) and discrete element method (DEM) to study the segregation of fresh self-compacting concrete (SCC). The relationship between rheological parameters of mortar and SCC was established using mortar film thickness theory. Rheological tests were performed on mortar with different water-to-binder ratios. The Bingham model for mortar was fitted via least squares, providing rheological parameters for SPH-DEM simulation. The coupling SPH-DEM simulated slump-flow and L-box tests, with mortar represented by SPH units and coarse aggregates represented by DEM particles. Results showed average relative errors of 2.1% for slump flow and 3.5% for blocking ratio. Simulation and experimental values agreed closely, supporting this approach to study SCC segregation. Numerical simulations of vibration-induced segregation were conducted, quantitatively analyzing coarse aggregate settling. Effects of water-to-binder ratio, mortar rheology, and mortar film thickness on segregation ratio were examined. When mortar film thickness ranged from 2.22 to 3.33 mm, the segregation ratio decreased with increasing thickness. This study could provide effective guidance for SCC engineering application.

The extensive application of mineral admixtures and additives has revealed that when the shear rate increases, the shear rate-shear stress curve of some fresh wet shotcrete materials increasingly diverges from a linear relationship. Previous studies on pressure loss in wet shotcrete employed the Bingham model to characterize the rheological behavior of the lubricating layer and concrete. When fresh wet shotcrete displays nonlinear rheological characteristics, there is a notable deviation in the predictive model of pumping pressure loss. This study addresses this deficiency by extending analytical predictions of pumping pressure loss in wet shotcrete to encompass nonlinear rheological models, including the Herschel–Bulkley (H–B) model and the Modified Bingham (M–B) model. The experimental test of wet shotcrete pumping is conducted to validate the feasibility of the proposed model. The investigation indicated that at a lubricating layer thickness of 3 mm, the pumping pressure loss predicted by the H–B model in shear flow mode agrees well with the experimental data within the range of the tested mixtures, but the M–B model exhibits considerable inaccuracies. This study offers theoretical and technological support for advancing research on wet shotcrete pumping technology, which will help promote the promotion and application of wet shotcrete