Search Results (35)

The performance of a building drainage system, “BDS”, is determined by the complexity of internal airflow and pressure dynamics, governed by unsteady wastewater flows from randomly discharging appliances such as WCs, sinks, and baths. Designers attempt to optimise system safety by equalising pressure and incorporating ventilation pipes and active devices such as AAVs and positive pressure reduction devices (PPRDs). However, failures within these systems can lead to foul gases and potentially hazardous microbes entering habitable spaces and posing a risk to public health. This study, for the first time, develops a novel model that simulates the effect of air from the sewer on BDS performance, which describes the correlation between system airflow and air pressure under the influence of air from the sewer. A combination of full-scale laboratory experiments representing a 3-storey building and real-world data from a 32-storey test rig configured as a building demonstrated that sewer air significantly modifies airflow and air pressure within a BDS. These findings are crucial for modern urban environments, where the prevalence of tall buildings amplifies the risks associated with air pressure transients. This work paves the way for updating codes to more effectively address real-world challenges. Full article

Achieving adequate frost resistance in cementitious composites made with low-clinker binders remains challenging, as conventional air-entraining admixtures often show limited effectiveness in such systems. This study examines an alternative approach that involves incorporating preformed polymeric microspheres to create a stable air–void system and enhance freeze–thaw durability. Cementitious composites were prepared using a low-clinker binder containing fly ash and ground granulated blast furnace slag (GGBFS) as supplementary cementitious materials, with natural sand partially replaced by fine recycled aggregate derived from concrete waste. The influence of polymeric microspheres on workability, compressive strength, pore structure, and frost resistance was evaluated. Compared to the reference mixture (32.8 MPa), the mortar modified with polymeric microspheres exhibited clearly higher compressive strength—about 25% greater after 28 days—while the AEA-modified mixture showed a slight reduction. Total porosity measured by MIP was 18% for REF, 19% for AEA, and 17% for PPMThe results showed that adding polymeric spheres initially introduced a network of discrete voids that improved the material’s resistance to early freeze–thaw cycles. However, due to the prolonged hydration of the low-clinker system, hydration products progressively filled the initially created voids after the partial degradation of the polymeric spheres. Consequently, the air–void system gradually disappeared, leading to a loss of frost resistance at later ages. After 100 cycles, the PPM mixture exhibited a 75% loss in flexural strength and a 35% loss in compressive strength, whereas the AEA mixture retained its durability, with compressive strength loss limited to 6%. This finding suggests that, although early tests may indicate improved performance, the long-term durability of low-clinker cementitious composites incorporating fine recycled aggregate cannot be reliably enhanced by preformed polymeric spheres alone. Full article

To mitigate flood damage caused by overflow from a levee, it is essential to prevent the levee failure or extend the time to breaching. Although turfgrass on a levee slope is effective in suppressing erosion, insufficient maintenance can reduce its coverage. When overtopping occurs under such non-uniform turfgrass conditions, the flow tends to entrain air. In spillways, air entrainment is known to reduce friction loss; therefore, it may also contribute to lowering shear stress and erosion depth. This study conducted flume experiments with artificial turf arranged in various patterns on levee slopes to investigate flow patterns, air entrainment, and erosion. The flow pattern changed depending on the turf arrangement and overflow depth, and air entrainment occurred due to water surface fluctuations around the turfgrass. The inception point of air entrainment was found to be similar to or shorter than that observed in stepped spillways. Furthermore, the experiments showed a tendency for erosion depth to decrease once air entrainment is fully developed. This finding is significant because it suggests that erosion can potentially be minimized not only by reinforcing the levee structure itself but also by modifying flow characteristics through designs that promote air entrainment. Full article

The use of 3D printing holds significant promise to transform the construction industry by enabling automation and customization, although key challenges remain—particularly the control of fresh-state rheology. This study presents a novel formulation that combines potassium-rich biomass fly ash (BFAK) with an air-entraining plasticizer (APA) to optimize the rheological behavior, hydration kinetics, and structural performance of mortars tailored for extrusion-based 3D printing. The results demonstrate that BFAK enhances the yield stress and thixotropy increases, contributing to improved structural stability after extrusion. In parallel, the APA adjusts the viscosity and facilitates material flow through the nozzle. Isothermal calorimetry reveals that BFAK modifies the hydration kinetics, increasing the intensity and delaying the occurrence of the main hydration peak due to the formation of secondary sulfate phases such as Aphthitalite [(K₃Na(SO₄)₂)]. This behavior leads to an extended setting time, which can be modulated by APA to ensure a controlled processing window. Flowability tests show that BFAK reduces the spread diameter, improving cohesion without causing excessive dispersion. Calibration cylinder tests confirm that the formulation with 1.5% APA and 2% BFAK achieves the maximum printable height (35 cm), reflecting superior buildability and load-bearing capacity. These findings underscore the novelty of combining BFAK and APA as a strategy to overcome current rheological limitations in digital construction. The synergistic effect between both additives provides tailored fresh-state properties and structural reliability, advancing the development of a sustainable SMC and printable cementitious materials. Full article

Organic polymer introduction effectively enhances the toughness, bond strength, and durability of ordinary cement-based materials, and is often used for concrete repair and reinforcement. However, the entrained air effect simultaneously induced by polymer and the inhibitory action on cement hydration kinetics often lead to degradation in mechanical performances of polymer-modified cement-based composite (PMC). Nanomaterials provide unique advantages in enhancing the properties of PMC due to their characteristic ultrahigh specific surface area, quantum effects, and interface modulation capabilities. This review systematically examines recent advances in nano-reinforced PMC (NPMC), elucidating their synergistic optimization mechanisms. The synergistic effects of nanomaterials—nano-nucleation, pore-filling, and templating mechanisms—refine the microstructure, significantly enhancing the mechanical strength, impermeability, and erosion resistance of NPMC. Furthermore, nanomaterials establish interpenetrating network structures (A composite structure composed of polymer networks and other materials interwoven with each other) with polymer cured film (The film formed after the polymer loses water), enhancing load-transfer efficiency through physical and chemical action while optimizing dispersion and compatibility of nanomaterials and polymers. By systematically analyzing the synergy among nanomaterials, polymer, and cement matrix, this work provides valuable insights for advancing high-performance repair materials. Full article

Geopolymer, as a sustainable, low-carbon gel binder, is regarded as a potential alternative to cement. Freeze–thaw (F-T) resistance, which has a profound influence on the service life of structures, is a crucial indicator for assessing the durability of geopolymer composites (GCs). Consequently, comprehending the F-T resistance of GCs is of the utmost significance for their practical implementation. In this article, a comprehensive and in-depth review of the F-T resistance of GCs is conducted. This review systematically synthesizes several frequently employed theories regarding F-T damage, with the aim of elucidating the underlying mechanisms of F-T damage in geopolymers. The factors influencing the F-T resistance of GCs, including raw materials, curing conditions, and modified materials, are meticulously elaborated upon. The results indicate that the F-T resistance of GCs can be significantly enhanced through using high-calcium-content precursors, mixed alkali activators, and rubber aggregates. Moreover, appropriately increasing the curing temperature has been shown to improve the F-T resistance of GCs, especially for those fabricated with low-calcium-content precursors. Among modified materials, the addition of most fibers and nano-materials remarkably improves the F-T resistance of GCs. Conversely, the effect of air-entraining agents on the F-T resistance of GCs seems to be negligible. Furthermore, evaluation and prediction models for the F-T damage of GCs are summarized, including empirical models and machine learning models. In comparison with empirical models, the models established by machine learning algorithms exhibit higher predictive accuracy. This review promotes a more profound understanding of the factors affecting the F-T resistance of GCs and their mechanisms, providing a basis for engineering and academic research. Full article

Channel fire poses a great threat to personnel safety and structural strength, in which the temperature profile is worthy of attention. In this paper, the longitudinal temperature profile of a ceiling jet induced by a wall-attached fire with different channel slopes was experimentally investigated using a 1:8 reduced-scale channel. The results show the following: (1) For channel fire with a horizontal ceiling, the influence of the burner aspect ratio and source-ceiling height on the temperature profile is monotonous in the cases considered in this work. With a larger burner aspect ratio and larger source-ceiling distance, more ambient air could be entrained; hence, the longitudinal temperature under the ceiling decays faster. (2) For channel fire with an inclined ceiling, when the burner aspect ratio and source-ceiling distance remain constant, the asymmetric entrainment induced by the flame under larger channel slope leads to more hot smoke being transported upstream. Consequently, the temperature profile is not symmetric, with higher temperatures upstream and lower temperatures downstream. (3) Combining the influence of the burner aspect ratios, source-ceiling distance, and burner aspect ratio, the characteristic length scale was modified. Based on this, a model describing the ceiling temperature profile was proposed and then verified with previous data. Full article

LED polymer multilayer films offer clear advantages over single-layer coatings, such as minimized particle settling, finer control over particle distribution, and more precise spectral tuning. However, the standard “coat–dry–coat” process for these multilayer systems often traps air bubbles, degrading film quality and uniformity. This study investigates the air entrainment mechanism in multilayer film formation. Bubbles form when the cured bottom layer exhibits a low contact angle, which destabilizes the advancing liquid front. High-speed microscopy captured these interfacial dynamics, and contact-angle measurements quantified the wetting behavior. Numerical simulations further demonstrated that reduced wettability and vortex formation drive air entrainment. To mitigate air entrainment, a semi-cured slot die coating approach was proposed to modify the surface wettability and suppress the flow instabilities. Incorporating temperature-dependent viscosity into the simulation model improved its predictive accuracy, cutting the error in predicted coating-gap limits from 11.49% to 4.99%. This combined strategy delivers reliable, bubble-free multilayer films and paves the way for more consistent, high-quality LED polymer applications. Full article

This study investigated the technical feasibility and antimicrobial potential of incorporating ornamental rock, limestone, and ginger waste into coating mortars with the aim of developing an innovative and sustainable solution for civil construction. This study evaluated the synergistic action of these materials on the microbiological and mechanical resistance of mortar, contributing to the greater durability and efficiency of the coatings. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analyses were performed to characterize the morphology, chemical composition, and crystalline structure of the added materials, confirming their suitability for the cement matrix. Tests in the fresh state evaluated parameters such as density, consistency index, and entrained air content, demonstrating the viability of the formulations, whereas flexural and compressive strength tests indicated significant improvements in the mechanical performance of the modified mortar. Microbiological tests demonstrated a significant reduction in microbial colonization, indicating the action of ginger’s bioactive compounds, such as gingerol and shogaol, which have antimicrobial properties and are effective in inhibiting the growth of pathogenic microorganisms, as confirmed by the reduction in the bacterial colony count from 4 × 10² to 1 × 10² CFU mL⁻¹. Comparisons with conventional compositions indicate that the proposed approach outperformed traditional formulations in terms of both mechanical resistance and microbiological control. Thus, the results validate this research as a promising strategy for improving the durability and performance of coating mortars, reducing maintenance costs, and promoting the sustainable use of alternative materials in civil construction. Full article

This research focuses on the impact of a pozzolanic additive (zeolite) on the durability properties of concrete and the evaluation of the surface finish of the final product (concrete). Durability is one of the key characteristics of concrete that ensures the performance of concrete structures, landscaping elements, and products over their lifetime and beyond. To reduce CO₂ emissions, replacing part of traditional cement with pozzolanic additives is necessary. We tested concrete mixes in which up to 20% of cement was replaced with a pozzolanic additive. Concrete flow and entrained air content were measured. The following properties of hardened modified concrete were determined: density, ultrasonic pulse velocity, water absorption, freeze–thaw resistance, and mechanical properties after 7 and 28 days of curing. The compressive strength values were normalised and expressed in MPa/g to obtain a deeper insight into the effect of a pozzolanic additive on the mechanical properties of concrete. The test results showed that the pozzolanic additive selected for testing reduced the flowability, density, and ultrasonic pulse velocity; increased entrained air content; and reduced the porosity of concrete. The compressive strength results at 28 days (normalised and expressed in MPa/g) showed that all specimens modified with up to 20% zeolite had a higher compressive strength than that of the reference specimen (from 0.0138 to 0.0164). Freeze–thaw resistance results showed that 15% was the optimum content of zeolite additive that could replace cement in the mix to obtain concrete with appropriate durability properties. Concrete surface finish evaluation tests showed that 15% of the pozzolanic additive is recommended to obtain a good-quality surface finish of exposed concrete. Full article

Semi-flexible pavement (SFP) mixture consists of porous matrix asphalt mixture and cement-based grouting material. This composite material gains advantages from both the rigid cementitious material and flexible asphalt mixture. It exhibits excellent anti-rutting capability while no joints are needed. However, SFP is prone to cracks in the field. This study employs water-based epoxy resin and emulsified asphalt as polymer additives to modify the grouting material. A response surface methodology (RSM) model was employed for multi-factor and multi-response optimization design. The ratio of water-based epoxy resin to emulsified asphalt (w/e ratio), polymer content, defoamer content, and mixing speed were considered in the model. Fluidity, compressive strength, and fracture energy were selected as response indicators. It was found that a low mixing speed was not able to produce grouting slurry with acceptable fluidity. The addition of higher polymer contents would lower the compressive strength of the grouting material due to the low stiffness of the polymer and entrained air produced during mixing. The addition of defoamer eliminated the bubbles and, therefore, increased the strength and fracture energy of the samples. By solving for the optimal model solution, the values of optimized parameters were determined to be a w/e ratio of 0.64, polymer content of 3.3%, defoamer content of 0.2%, and mixing speed of 2000 rpm. Microstructural analysis further confirmed that the synergistic effect of water-based epoxy resin and emulsified asphalt can effectively make the microstructure of the hardened samples denser. The anti-cracking ability of the SFP mixture can be increased by 22% using optimally designed grouting material. The findings in this study shed light on the design of toughness-reinforced SFP materials. Full article

The conventional piano key weir (PKW), characterized by a rectangularly cranked planform, is an effective discharge structure. Its hydraulic performance is primarily influenced by several geometrical parameters, including crest length, key width, and weir height. To enhance its hydraulic efficiency, each key is modified with an isosceles triangle at both the crest and the vertical base surface. In this way, the weir crest is extended both up and downstream; the key floor is lowered accordingly, resulting in a triangular prism-shaped floor. Laboratory tests are conducted to compare the hydraulic performance of this modified weir with that of the standard design. The results demonstrate that the geometrical adjustments noticeably improve the overflow discharge. With an equilateral triangle extending the crest length by ~23%, the discharge capacity is enhanced by 16–20% within the examined flow conditions. The modified weir outperforms the conventional design in terms of hydraulic performance. The improvements can be attributed to several factors: elongated crest length enhancing the flow capacity; triangular upstream overhangs improving the inflow condition along the inlet key’s height; lowered inlet key floor increasing the flow volume, promoting better flow movement towards the crest; lowered outlet key floor reducing the submergence effect under high flow conditions; and the triangular crest of the inlet key facilitating jet spreading and promoting air entrainment. These modifications make the redesigned PKW a promising option for improved hydraulic performance in engineering applications. Full article

This paper presents an experimental study aimed at improving the performance of polymer cement mortar by evaluating the properties of acrylic ester redispersible polymers, synthesized using a change in polymerization method from emulsion monomer to monomer dropwise addition methods, along with the use of a functional additive in the form of a foaming agent. To achieve the research objectives, a polymer with a glass transition temperature of −11 °C was synthesized by fixing the monomer ratio, particle-size distribution, and glass transition temperature, and the physical properties of the polymer cement mortar were assessed. The results showed that polymers synthesized using the modified polymerization method increased elongation at break and possessed a 35% smaller average particle size. The use of the foaming agent also resulted in enhanced tensile strength. The polymer cement mortars made with these respective polymers demonstrated improvements in compressive strength 11~25%, flexural strength 53~77%, bond strength 78~113%, volumetric changes 65~88%, and water absorption 30~70%. These findings suggest that changes in the polymerization method and the incorporation of functional additives influence the average particle size and air entrainment control properties of the polymers, thereby positively impacting the performance of the cement hydrates. Full article

This study investigates the relationship between the molecular structure and foaming of poly(ethylene glycol) and poly(propylene glycol) triblock copolymers in Portland cement pastes. Four copolymers with different molecular structures were studied at varying concentrations. All copolymers showed a reduction in surface tension of the cement pore solution; however, only some of them demonstrated foaming and air entraining in cement paste. The results indicated that the molecular structure parameter, hydrophilic-to-lipophilic balance (HLB), has a direct relationship with the foaming and air-entraining performance of the copolymers. The total organic carbon measurements showed very small adsorption of these non-ionic copolymers on hydrating cement particles due to the lack of surface charge needed to interact with the heterogeneously charged surface of hydrating cement. In addition, these copolymers did not seem to affect the flow of cement paste due to a lack of adsorption on cement particles. The cement paste modified with the copolymers showed increased water sorption compared to the control paste due to the increased capillary porosity and slight increase in pore surface hydrophilicity. However, the freeze-thaw resistance was shown to improve with an increase in the number of air voids in the modified cement pastes. The findings establish the relationship between molecular properties of copolymers and their air-entraining performance in cement paste to mitigate the damages caused by freeze-thaw action. Full article

The vertical profiles of aerosol optical properties are vital to clarify their transboundary transport, climate forcing and environmental health influences. Based on synergistic measurements of multiple advanced detection techniques, this study investigated aerosol vertical structure and optical characteristics during two dust and haze events in Lanzhou of northwest China. Dust particles originated from remote deserts traveled eastward at different altitudes and reached Lanzhou on 10 April 2020. The trans-regional aloft (~4.0 km) dust particles were entrained into the ground, and significantly modified aerosol optical properties over Lanzhou. The maximum aerosol extinction coefficient (σ), volumetric depolarization ratio (VDR), optical depth at 500 nm (AOD₅₀₀), and surface PM₁₀ and PM_2.5 concentrations were 0.4~1.5 km⁻¹, 0.15~0.30, 0.5~3.0, 200~590 μg/m³ and 134 μg/m³, respectively, under the heavy dust event, which were 3 to 11 times greater than those at the background level. The corresponding Ångström exponent (AE_440–870), fine-mode fraction (FMF) and PM_2.5/PM₁₀ values consistently persisted within the ranges of 0.10 to 0.50, 0.20 to 0.50, and 0.20 to 0.50, respectively. These findings implied a prevailing dominance of coarse-mode and irregular non-spherical particles. A severe haze episode stemming from local emissions appeared at Lanzhou from 30 December 2020 to 2 January 2021. The low-altitude transboundary transport aerosols seriously deteriorated the air quality level in Lanzhou, and aerosol loading, surface air pollutants and fine-mode particles strikingly increased during the gradual strengthening of haze process. The maximum AOD₅₀₀, AE_440–870nm, FMF, PM_2.5 and PM₁₀ concentrations, and PM_2.5/PM₁₀ were 0.65, 1.50, 0.85, 110 μg/m³, 180 μg/m³ and 0.68 on 2 January 2021, respectively, while the corresponding σ and VDR at 0.20–0.80 km height were maintained at 0.68 km⁻¹ and 0.03~0.12, implying that fine-mode and spherical small particles were predominant. The profile of ozone concentration exhibited a prominent two-layer structure (0.60–1.40 km and 0.10–0.30 km), and both concentrations at two heights always remained at high levels (60~72 μg/m³) during the entire haze event. Conversely, surface ozone concentration showed a significant decrease during severe haze period, with the peak value of 20~30 μg/m³, which was much smaller than that before haze pollution (~80 μg/m³ on 30 December). Our results also highlighted that the vertical profile of aerosol extinction coefficient was a good proxy for evaluating mass concentrations of surface particulate matters under uniform mixing layers, which was of great scientific significance for retrieving surface air pollutants in remote desert or ocean regions. These statistics of the aerosol vertical profiles and optical properties under heavy dust and haze events in Lanzhou would contribute to investigate and validate the transboundary transport and radiative forcing of aloft aerosols in the application of climate models or satellite remote sensing. Full article