Search Results (91)

To enhance the performance of microencapsulated phase change material (MPCM) mortar, hydroxypropyl methyl cellulose (HPMC) was incorporated. This study tested the mortar’s consistency, water retention, water absorption, compressive strength, and thermal conductivity under varying contents of MPCM (as an equivalent volume replacement of sand) and mass contents of HPMC. The results indicate that increasing both MPCM and HPMC contents reduces mortar consistency. Specifically, when HPMC content is 0.05%, 0.10%, and 0.15%, the mortar’s consistency decreases by approximately 24.38%, 35.34%, and 41.30%, respectively, in MPCM-free mortar, with a maximum combined reduction of 74% observed in the 0.15% HPMC and 4% MPCM formulation. MPCM shows a negligible effect on water retention, while HPMC positively influences this property, though not significantly. In contrast, HPMC has little impact on water absorption, whereas MPCM significantly increases it: as MPCM content rises from 0% to 1%, 2%, 3%, and 4%, the mortar’s water absorption increases by 22.55%, 58.82%, 121.57%, and 200.00%, respectively. Both HPMC and MPCM additions lead to reductions in the mortar’s compressive and bond strengths. Notably, a 0.10% HPMC content decreases thermal conductivity by approximately 12% compared to mortar without HPMC. Using the corresponding fitting formulas, predictive values for various performance indicators can be accurately derived. Full article

Freeze–thaw durability of 3D-printed engineered cementitious composites (3DP-ECC) is strongly affected by print-induced interlayer defects and anisotropy, particularly in cold regions. This study investigated Cast-ECC and Z-direction 3DP-ECC incorporating Yellow River sediment (YRS) as an equal-mass replacement for quartz sand at 0–100%. Compressive, three-point bending, and four-point bending tests, relative dynamic elastic modulus (RDME), XCT, MIP, SEM–EDS, and Weibull damage modeling were used to evaluate degradation up to 150 freshwater freeze–thaw cycles. Moderate YRS replacement (25–50%) improved particle packing, reduced visible defects, and refined the pore structure, thereby enhancing frost resistance. The R50 mixture showed the best residual performance: after 150 cycles, compressive strength decreased from 55 to 46 MPa in Cast-ECC and from 54 to 44 MPa in 3DP-ECC, corresponding to retention rates of 83.6% and 81.5%, respectively. The residual peak load in four-point bending of 3DP-ECC-R50 was 15.4% lower than that of Cast-ECC-R50, confirming the detrimental role of interlayer defects under loading perpendicular to the layers. RDME-based Weibull fitting described the overall damage evolution (R² = 0.876–0.994), while XCT, MIP, and SEM–EDS indicated that interlayer discontinuities, pore-structure evolution, and local microstructural degradation governed anisotropic deterioration. The results support durability-oriented design of YRS-based 3DP-ECC in cold regions. Full article

Drying in granular porous media is governed by coupled thermal and hydraulic processes that can be substantially modified by biological activity. This proof-of-concept study investigated how surface heating and fungal colonization influence the evolution of thermal conductivity (λ) and matric suction (ψ) as functions of volumetric water content ${\theta }_v$ in Ottawa 20/30 sand. Four treatments were examined: sterile sand at 22 °C (T1), sterile sand at 28 °C (T2), fungal-amended sand with 10% biomass and 9-day incubation (T3), and fungal-amended sand with 15% biomass and 30-day incubation (T4). Samples were instrumented to monitor ${\theta }_v$, λ, and ψ during controlled evaporation using synchronized HYPROP and VARIOS measurements on the same specimen. Across all treatments, λ increased with ${\theta }_v$ (that is, λ declined as drying progressed), and ψ reflected the transition from hydraulically connected to disconnected pore water. Heating shortened the drying time but did not materially change the form of the λ–${\theta }_v$ relationship or generate strong matric gradients in sterile sand. Low biomass (T3) produced thermal and hydraulic responses comparable to the heated sterile control (T2), indicating limited pore-scale modification at early colonization. In contrast, high biomass (T4) widened the effective saturation range, maintained low and nearly uniform ψ across depth, and exhibited the steepest mid-range λ–${\theta }_v$ slope with a higher peak λ (~4 Wm⁻¹K⁻¹), consistent with hyphae and extracellular polymers stabilizing thin water films. A soil water retention curve (SWRC) analysis using the van Genuchten model further indicated increased water retention and delayed air entry with an increasing fungal biomass, with approximate air-entry values increasing from ~1.8 kPa (T3) to ~3.0 kPa (T4). Tests were terminated upon tensiometer cavitation rather than complete gravimetric dryness, constraining observations at very low ${\theta }_v$. These results indicate that heating primarily affects the rate of drying, whereas fungal networks alter the pathway by preserving hydraulic and thermal continuity at relatively high ${\theta }_v$. This behavior suggests a potential role of bio-mediated structuring in influencing near-surface thermo-hydraulic processes relevant to energy foundations, soil covers, and desiccation management in biologically active or bio-engineered soils. Full article

Soil salinity poses a major challenge to agricultural productivity, especially threatening food security in arid and semi-arid areas. Traditional soil reclamation methods, such as leaching, chemical amendments, and drainage engineering, usually need large amounts of water, involve high costs, and can lead to environmental problems. This review compiles existing knowledge on innovative strategies for managing saline soils, focusing on buried interlayer systems that use materials like straw, sand, gravel–sand mixtures, and biochar. These interlayers improve soil hydraulic properties by preventing capillary rise, encouraging salt leaching, and reducing surface salt buildup. Biochar stands out as a particularly useful material because of its stability, large surface area, porosity, and high cation exchange capacity. These features help improve soil structure, increase water retention, and effectively retain sodium. Evidence from lab and field tests shows that buried biochar layers can stop salt from moving upward, aid in desalinating the root zone, and boost crop yields. While straw and sand interlayers show potential in reducing salinity, biochar is noted for its multifunctionality and long-term effectiveness in addressing salinity problems. The success of buried biochar systems depends on several factors, including the properties of the biochar, how much is used, how deep it is buried, and the specific soil and climate conditions. This review highlights how these systems work, compares their performance, and points out research gaps, advocating for their potential as a sustainable, resource-efficient way to manage salinity and improve soil health over the long term. A substantial proportion of the existing evidence is derived from controlled laboratory studies, and the buried biochar layer approach remains an emerging technique that requires further validation under field conditions. Still, significant knowledge gaps persist regarding long-term performance and water-salt dynamics, while site-specific soil variability and scalability challenges may limit the effective implementation of biochar interlayer systems under field conditions. Full article

Flexible concrete blankets (FCBs) are emerging as a promising material for slope protection and surface stabilization, offering advantages of light weight, ease of installation, and environmental adaptability. This study investigates the mechanical properties, freeze–thaw resistance, and microstructural evolution of FCBs fabricated with varying cement–sand ratios and high alumina cement dosages. A series of mechanical tests, including compressive, flexural, and tensile strength evaluations, were conducted alongside freeze–thaw cycling tests (up to 125 cycles) to assess mass loss and strength retention. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were employed to elucidate the hydration mechanisms and damage evolution at the microstructural level. The results demonstrate that FCBs exhibit ductile failure behavior, with peak tensile strengths ranging from 3.1 to 4.5 MPa and tensile strain capacities ranging from 5 to 16%. The optimal mix achieved a compressive strength of 51.2 MPa after 28 days of curing. Freeze–thaw cycling induced a two-stage degradation pattern, with damage initiation occurring at approximately 50 cycles and significant deterioration beyond 75 cycles. After 125 cycles, mass loss ranged from 4.39% to 4.99%, and compressive strength retention varied between 78% and 83%, depending on the mix composition. Mixtures with balanced cement–sand ratios (1:1) and moderate Portland cement content demonstrated superior frost resistance, whereas high alumina cement-rich mixtures exhibited pronounced structural loosening due to phase transformations of unstable hydration products. These findings provide a theoretical and experimental basis for optimizing the composition of FCBs to achieve enhanced mechanical performance and durability in cold-region engineering applications. Full article

Nature-based solutions, including green infrastructure (GI), are considered sustainable tools for stormwater treatment. GI elements (rain gardens, green roofs, etc.) are increasingly applied as integrated approaches for climate change mitigation and environmental pollution reduction. This study focused on investigations of rain gardens for reducing stormwater polluted by residual chlorine after the disinfection of outdoor spaces. Laboratory (column test) and field tests were carried out to evaluate the infiltration capacities of an experimental rain garden model, as well as its efficiency for retaining residual chlorine. The experiments were conducted using simulated rain garden layers composed of waste materials that remained after different production processes. The average infiltration coefficient values obtained were 2.55 × 10⁻⁵ m/s, 2.45 × 10⁻⁵ m/s, 2.24 × 10⁻⁵ m/s, 3.4 × 10⁻⁵ m/s, 1.28 × 10⁻⁵ m/s, 1.84 × 10⁻⁵ m/s (laboratory test), and 1.39 × 10⁻⁵ m/s (field test). These values correspond to the characteristics of sand–gravel substrates. A chlorine retention efficiency of 82.5–87% was obtained. Granulometric analysis confirmed fraction size suitability for rain garden filtration. This research indicates the potential of rain gardens for reducing stormwater pollution, providing a basis for future research and practical implementation. Full article

In urban plantings, mined sand and scoria are commonly used as low-nutrient substrates to improve plant establishment and growth. However, reliance on mined materials conflicts with sustainability policies promoting resource circularity and waste reuse. Construction wastes are readily available, and while their high alkalinity and density may limit plant growth, incorporating organic matter, like pine bark, can ameliorate these issues. We investigated whether construction waste amended with pine bark can support plant growth. We evaluated physical and chemical properties of 12 substrates combining four mineral components—scoria (mined), sand (recycled), crushed concrete (recycled), and crushed rock (recycled)—with pine bark (10%, 20%, and 50% v/v). We then tested eight of these substrates in a container experiment, evaluating the growth of two woody shrubs: Alyogyne huegelii and Goodenia ovata. All mineral components were alkaline (pH 9.2–12.3), with crushed concrete remaining hyper-alkaline despite pine bark addition. Greater pine bark volumes improved air-filled porosity but reduced water retention. Substrates with 50% v/v pine bark had lower plant biomass compared to those with 10% v/v. However, plant biomass was similar across all mineral components. This demonstrates that construction waste–pine bark substrates can support plant growth in urban plantings, supporting broader sustainability goals in cities. Full article

Rheology plays an important role in the 3D concrete printing technology, because it directly governs the flowability and shape retention of the material, impacting both the printing process and the final quality of the obtained structure. Local raw materials such as Portland cement, washed sand, and tap water were used for the preparation of 3D-printed concrete mixtures. The solid-state polycarboxylate ether with an anti-foaming agent was used as superplasticizer. The Portland cement was partially replaced (by volume) with a natural zeolite additive in amounts ranging from 0% to 9% in 3D-printed concrete mixtures. A rotational rheometer with coaxial cylinders was used in this research for the determination of rheological characteristics of prepared 3D-printed concrete mixtures. The Herschel–Buckley model was used to approximate experimental flow curves and assess rheological parameters such as yield stress, plastic viscosity, and shear-thinning/thickening index. The additional experiments and calculations, such as water bleeding test and evaluation of the carbon footprint of 3D-printed concrete mixtures, were performed in this work. The replacement of Portland cement with natural zeolite additive positively influenced rheological and stability-related properties of 3D-printed concrete mixtures. Natural zeolite additive consistently reduced water bleeding, enhanced yield stress under increasing shear rates, and lowered plastic viscosity, thereby improving flowability and mixture transportation during the 3D printing process. As the shear-thinning/thickening index remained stable (indicating non-thixotropic behavior in most cases), higher amounts of natural zeolite additive introduced slight thixotropy (especially under decreased shear rates). These changes contributed to better shape retention, layer stability, and the ability to print taller and narrower structures without collapse, making natural zeolite additive suitable for use in the optimized processes of 3D concrete printing. A significant decrease in total carbon footprint (from 3% to 19%) was observed in 3D-printed concrete mixtures with an increase in the mentioned amounts of natural zeolite additive, compared to the mixture without this additive. Full article

This study investigates sustainable alternatives for thermal regulation in building materials by incorporating modified basic oxygen furnace slag (MBOFS) as a partial replacement for natural aggregates in concrete. MBOFS was produced by injecting oxygen and silica sand into molten BOF slag to reduce free CaO and MgO, enhancing stability and suitability for cementitious composites. Characterization revealed high mid-infrared emissivity (up to 95.92% in the 8–13 μm range), low solar reflectivity, and high absorptance—properties favorable for passive radiative cooling. Optical, physical, mechanical, and thermal evaluations included spectral analysis, tests for density, porosity, compressive strength, and indoor irradiation with heat flux and temperature monitoring. Increasing MBOFS content raised thermal resistance from 0.034 to 0.069 m²·K/W and lowered thermal transmittance from 3.644 to 3.235 W/m²·K. Higher heat storage capacity and higher emissivity (thermal radiation) suppress the thermal transmittance, thus improving the thermal resistance of the building walls. The 60% replacement showed the most balanced surface thermal response, whereas higher ratios yielded greater energy retention. These results demonstrate that MBOFS can enhance insulation, radiative cooling, and mechanical performance, advancing climate-responsive concrete for urban heat island mitigation. Full article

To promote the resource utilization of high-titanium blast furnace slag (HTBFS) and advance the development of lightweight prefabricated structures, this study developed a lightweight HTBFS concrete composite beam (HTC composite beam) by replacing natural gravel and sand in concrete with HTBFS coarse and fine aggregates, and incorporating fly ash ceramsite to reduce self-weight. Symmetrically two-point bending tests were conducted on five HTC composite beams with different reinforcement ratios and precast heights, one Integrally cast HTC beam, and one ordinary concrete composite beam. The failure modes, load-carrying capacities, and deformation characteristics were evaluated. The loading process was also simulated using Abaqus, and the numerical results were compared with experimental data for validation. The results indicate that HTC composite beams satisfy the plane-section assumption; increasing the reinforcement ratio improves the load-carrying capacity, and the precast height has positive effect of HTC composite beams’ load-carrying. Compared with the ordinary concrete composite beam, the HTC composite beam exhibited a 12.30% higher load-carrying capacity, smaller deflection, and better deformation capacity. Multiple energy-based indices demonstrated that HTC composite beams possess favorable post-cracking plastic deformation capacity and stiffness retention. The difference between the finite element simulations and experimental results was less than 5%, confirming both the reliability of the numerical model and the accuracy of the experimental data. An economic analysis revealed that this structural system has significant potential for carbon reduction and cost savings, with an overall saving of approximately 141,000–500,000 CNY. These findings provide theoretical and engineering support for the application of HTC composite beams in prefabricated construction and have positive implications for reducing project costs and promoting the industrialization and low-carbon development of prefabricated buildings. Full article

CO₂ circulation between subsurface wells is a promising approach for geothermal energy recovery from deep saline formations originally developed for Carbon Capture and Storage (CCS). This study evaluates the feasibility, operability, and performance of sustained CO₂ flow between an injector and a producer at the Canadian Aquistore site, a location with active CO₂ injection and an established geological model. A high-resolution sector model, derived from a history-matched parent simulation, was used to conduct a comprehensive uncertainty analysis targeting key operational and subsurface variables, including injection and production rates, downhole pressures, completion configurations and near-wellbore effects. All simulation scenarios retained identical initial and boundary conditions to isolate the impact of each variable on system behavior. Performance metrics, including flow rates, pressure gradients, brine inflow, and CO₂ retention, were analyzed to evaluate CO₂ circulation efficiency. Simulation results reveal several critical findings. Elevated injection rates expanded the CO₂ plume, while bottomhole pressure at the producer controlled brine ingress from the regional aquifer. Once the CO₂ plume was fully developed, producer parameters emerged as dominant control factors. Completion designs at both wells proved vital in maximizing CO₂ recovery and suppressing liquid loading. Permeability variations showed limited influence, likely due to sand-dominated continuity and established plume connectivity at Aquistore. Visualizations of water saturation and CO₂ plume geometry underscore the need for constraint optimization to reduce fluid mixing and stabilize CO₂-rich zones. The study suggests that CO₂ trapped during circulation contributes meaningfully to permanent storage, offering dual environmental and energy benefits. The results emphasize the importance of not underestimating subsurface complexity when CO₂ circulation is expected to occur under realistic operating conditions. This understanding paves the way to guide future pilot tests, operational planning, and risk mitigation strategies in CCS-enabled geothermal systems. Full article

In this study, a slow-release fertilizer (SRF) was obtained by occluding NPK 10–10–10 into two matrices and compared with the uncoated mineral fertilizer (F). The first matrix, FOMI, used biosolids/paper sludge at 3:1 (w/w); the second, FOMII, used biosolids/clay at 1:1 (w/w). Materials and pellets were physiochemically and microbiologically characterized. Release kinetics were evaluated in water and in soil columns packed with acid-washed sand; matrix-only controls and sand blanks confirmed negligible background N, P, and K. The uncoated mineral fertilizer (F) showed a rapid burst, whereas occlusion slowed release. FOMII reduced release relative to F, and FOMI produced the slowest, controlled profiles: kinetic fits yielded lower k values for FOMI than for FOMII and F. FOMI also exhibited higher water-retention capacity (WRC) and cation-exchange capacity (CEC), consistent with its greater organic-matter content. In soil, FOMI released less than 15% at 48 h and no more than 75% at 30 d, meeting European Committee for Standardization (CEN) SRF criteria; FOMII released faster than FOMI but slower than F, which exceeded 90% within the test period. Therefore, FOMI is a biodegradable, low-cost SRF that improves fertilizer-use efficiency while returning organic matter to agricultural soils; FOMII shows intermediate yet beneficial performance. Full article

Biopolymers have recently been introduced as eco-friendly alternatives to other chemical cementitious additives for sandy soil stabilization, especially in pavement construction. The resilient modulus (M_R) is a key metric considered in the mechanistic design of pavement layers that ensures a safe and economic design based on guaranteed accurate values. This study investigated the effects of dehydration on the M_R of biopolymer-treated sand. Prepared specimens were subjected to two different curing conditions. The first set underwent closed-system curing (CSC) for periods of 7, 14, and 28 days. The second set of specimens was cured at different levels of suction by controlling relative humidity (RH) using different salt solutions (0.27, 1.0, 9.7, 21.0, 54.6, 113.7, and 294 MPa), referred to as dehydration curing (DC). The soil water retention curve (SWRC) was measured over the entire suction range to evaluate the dehydration curing and to link the results of suction levels and dehydration regime. M_R tests were conducted on both sets of specimens using a dynamic triaxial system to simulate different confining, traffic, and dynamic stresses. The results showed a significant increase in M_R (i.e., up to eight times) for specimens cured under DC conditions that was proportional to the suction level across different zones of the SWRC. Scanning electron microscopy revealed a phase change from hydrogel to film, which enhanced cementation and bonding between particles. in addition, CSC treatment resulted in a 10–30% reduction in M_R. A new regression model is proposed to predict the M_R of biopolymer-treated sand as a function of confining stresses, dynamic stresses, and suction. These findings will assist pavement engineers and designers in achieving safe, sustainable, and economic designs. Full article

This study advances alkali-activated cementitious materials (AACMs) by developing a ground-granulated blast furnace slag/high-calcium fly ash (GGBS/HCFA) composite that incorporates Tuokexun desert sand and by establishing a clear linkage between activator chemistry, mix proportions, curing regimen, and microstructural mechanisms. The innovation lies in valorizing industrial by-products and desert sand while systematically optimizing the aqueous glass modulus, alkali equivalent, HCFA dosage, and curing temperature/time, and coupling mechanical testing with XRD/FTIR/SEM to reveal performance–structure relationships under thermal and chemical attacks. The optimized binder (aqueous glass modulus 1.2, alkali equivalent 6%, and HCFA 20%) achieved 28-day compressive and flexural strengths of 52.8 MPa and 9.5 MPa, respectively; increasing HCFA beyond 20% reduced compressive strength, while flexural strength peaked at 20%. The preferred curing condition was 70 °C for 12 h. Characterization showed C-(A)-S-H as the dominant gel; elevated temperature led to its decomposition, acid exposure produced abundant CaSO₄, and NaOH exposure formed N-A-S-H, each correlating with strength loss. Quantitatively, acid resistance was weaker than alkali resistance and both deteriorated with concentration: in H₂SO₄, 28-day mass loss rose from 1.22% to 4.16%, with compressive/flexural strength retention dropping to 75.2%, 71.2%, 63.4%, and 57.4% and 65.3%, 61.6%, 58.9%, and 49.5%, respectively; in NaOH (0.2/0.5/0.8/1.0 mol/L), 28-day mass change was +0.74%, +0.88%, −1.85%, and −2.06%, compressive strength declined in all cases (smallest drop 7.77% at 0.2 mol/L), and flexural strength increased at lower alkalinity, consistent with a pore-filling micro-densification effect before gel dissolution/cracking dominates. Practically, the recommended mix and curing window deliver structural-grade performance while improving high-temperature and acid/alkali resistance relative to non-optimized formulations, offering a scalable, lower-carbon route to utilize regional desert sand and industrial wastes in durable cementitious applications. Full article

Lost circulation, a prevalent challenge in drilling engineering, poses significant risks including drilling fluid loss, wellbore instability, and environmental contamination. Conventional plugging materials often exhibit an inadequate performance under high-temperature, high-pressure (HTHP), and complex formation conditions. To address that, this study developed a high-performance gel–resin composite plugging material resistant to HTHP environments. By optimizing the formulation of bisphenol-A epoxy resin (20%), hexamethylenetetramine (3%), and hydroxyethyl cellulose (1%), and incorporating fillers such as nano-silica and walnut shell particles, a controllable high-strength plugging system was constructed. Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) confirmed the structural stability of the resin, with an initial decomposition temperature of 220 °C and a compressive strength retention of 14.4 MPa after 45 days of aging at 140 °C. Rheological tests revealed shear-thinning behavior (initial viscosity: 300–350 mPa·s), with viscosity increasing marginally to 51 mPa·s after 10 h of stirring at ambient temperature, demonstrating superior pumpability. Experimental results indicated excellent adaptability of the system to drilling fluid contamination (compressive strength: 5.04 MPa at 20% dosage), high salinity (formation water salinity: 166.5 g/L), and elevated temperatures (140 °C). In pressure-bearing plugging tests, the resin achieved a breakthrough pressure of 15.19 MPa in wedge-shaped fractures (inlet: 7 mm/outlet: 5 mm) and a sand-packed tube sealing pressure of 11.25 MPa. Acid solubility tests further demonstrated outstanding degradability, with a 97.69% degradation rate after 24 h in 15% hydrochloric acid at 140 °C. This study provides an efficient, stable, and environmentally friendly solution for mitigating drilling fluid loss in complex formations, exhibiting significant potential for engineering applications. Full article