Search Results (63)

The widespread application of concrete with specific functions has become indispensable in modern technology. However, the persistent issue of electromagnetic pollution poses a serious hazard to human health, electronic equipment, and military operations. Although various conventional electromagnetic absorbing materials have been incorporated, the achievable EMW-absorption performance is still restricted, with only a narrow effective absorption bandwidth. This study investigates the application of advanced 3D-printing technology to produce concrete with enhanced EMW-absorption properties with the incorporation of SAP (super-absorbent polymers). To achieve this, concrete samples with three SAP occupying the concrete volumes (0 vol.%, 20 vol.%, and 40 vol.%) and three methods (pretreatment-addition) were examined to provide an in-depth analysis of the properties and microstructures. The study reveals superior electromagnetic absorption in concrete enhanced with SAP compared to the untreated counterpart. Specifically, samples subjected to 40 vol.% Dry Treatment SAP exhibited exceptional performance, achieving 98.77% absorption at 7.53 GHz frequency with a peak reflectance of −19.12 dB, outperforming unmodified absorbing resin concrete by 25.44%. Moreover, microscopic analysis revealed irregular void distribution within the concrete, while the 3D-printing and -mixing processes led to SAP particle fractures, forming a complex 3D structure, thereby enhancing EMW-absorption performance. Ultimately, by selecting appropriate SAP pre-treatment and mixing methods based on the specific frequency range, this study provides crucial references and practical guidance for the application of EMW-absorbing concrete in military and technological contexts. Full article

To investigate the fracture behavior of super-absorbent polymer (SAP) internally cured polyvinyl alcohol (PVA) fiber-reinforced concrete (SAP-PVAC), three-point bending tests were carried out. This study systematically examined the effects of (1) PVA fiber content and (2) initial crack-depth-to-beam-height ratios (a₀/D) on the failure modes, fracture toughness (K_IC), and residual flexural tensile strength (f_R,1) of SAP-PVAC beams. The test results demonstrate that SAP particles have a weakening effect on concrete strength (reduce about 6%). Still, the addition of PVA fibers can effectively improve the crack-resistance performance of SAP-PVAC and significantly increase the residual flexural tensile strength by 4.5–42%. The softening performance of the concrete is affected by the initial crack-height ratio. An increase in a₀/D leads to an obvious increase in the crack opening displacement but has little impact on the fracture toughness, while the fracture energy shows a downward trend. SEM microscopic analysis reveals that the synergistic effect of SAP and PVA fibers exhibits a positive promoting effect on the toughening and crack resistance of SAP-PVAC specimens. These results establish a theoretical framework for SAP-PVAC fracture assessment and provide actionable guidelines for its shrinkage-crack mitigation structure engineering applications. Full article

To achieve sustainable agriculture development in arid regions, it is imperative to improve the soil quality of arid sandy soils. This study explored the effects of the combined application of organic–inorganic fertilizers with soil conditioners on the physiological characteristics, yield, and quality of rapeseed in arid sandy lands. The aim was to provide a technical reference for improving sandy soil and increasing rapeseed yield in arid regions. This field study designed six treatments (control group: organic fertilizer + chemical fertilizer (CK); T1: organic fertilizer + chemical fertilizer + super absorbent polymer (SAP); T2: organic fertilizer + chemical fertilizer + humic acid (PI); T3: organic fertilizer + chemical fertilizer + attapulgite (PII); T4: organic fertilizer + chemical fertilizer + PI + PII; HF: chemical fertilizer) to evaluate their effects on the nutrient absorption, physiological characteristics, yield, and quality of rapeseed. The results showed that the combination of organic–inorganic fertilizers with SAP, PI, PII, or PI + PII could significantly reduce the salinity of sandy soil while increasing the nutrient content in various parts of rapeseed. Among the combinations, the SAP treatment (T1) had the most significant effect, with the following specific impacts: (1) Alleviation of salt stress: The SAP treatment increased the root potassium ion content by 63.09% and reduced sodium ion content by 60.16% compared with CK, significantly increasing the potassium/sodium ratio. (2) Physiological improvement: The SAP treatment increased the total chlorophyll content (TCC), superoxide dismutase/catalase activity, and dry matter accumulation by 86.85%, 161.58%, and 376.8%, respectively, compared with CK. (3) Yield and quality enhancement: The SAP treatment increased rapeseed yield and the crude protein content in stems and leaves by 148.32% and 86.05%, respectively, but decreased crude fiber content by 43.59% compared with CK. (4) Economic benefits: The net revenue (NR) of the SAP treatment reached 197.62 USD per hectare, which was significantly higher than that of other treatments. A comprehensive evaluation showed that the combined application of organic–inorganic fertilizers with SAP enhanced plant antioxidant enzyme activity and photosynthetic efficiency, synergistically enhancing the yield and quality of rapeseed in sandy areas. This study provides an economically efficient solution for sustainable agricultural development in arid regions. Full article

The tensile strength of stabilized clayey soil is a key indicator of its resistance to cracking and directly governs its performance when used as subgrade fill. In this study, ordinary Portland cement and polyacrylate-based super-absorbent polymers (SAP) were combined to stabilize four typical high-water content clayey soils sourced from Northern Bavaria. The optimal SAP content was determined based on absorption capacity by the tea-bag method. Subsequently, the effects of cement content and curing period on the Brazilian tensile strength (BTS) of clayey soils were investigated, and the correlation between Brazilian tensile strength and unconfined compressive strength (UCS) was discussed. The results indicated the following: the optimal SAP content was 0.3%; the BTS increased significantly with higher cement content and a longer curing period; the failure modes of BTS specimens were revealed, including multiple non-through fracture, non-central fracture, and central fracture; a strong linear correlation was established between BTS and UCS, with the proportional coefficient ranging from 0.129 to 0.233. The findings of this study can provide a valuable reference for the design and application of cement-SAP stabilized soils in practical engineering. Full article

The performance of resin anchoring agents in deep coal mine roadways is significantly compromised by water-bearing and chemically aggressive conditions, posing a major threat to support system reliability. This study aims to systematically quantify this performance deterioration and develop a more resilient material solution for these challenging environments. A comprehensive experimental program was conducted, including uniaxial compression, pull-out, and interface shear tests, accompanied by the systematic improvement of the resin formulation and microstructural analysis via Scanning Electron Microscopy (SEM). The results showed that increasing borehole water content to 30% reduced the compressive strength of conventional resin by over 40%, while acidic environments (pH = 5) caused a 70% drop in its interfacial shear strength. In contrast, an improved formulation incorporating hydroxypropyl acrylate and a super absorbent polymer (SAP) exhibited a 20% higher initial strength, maintained over 85% of its strength under water saturation, and retained functional residual strength in acidic conditions. SEM analysis confirmed that the improved resin’s denser microstructure suppressed interfacial microcrack formation. The findings demonstrate that the improved formulation provides a robust material basis for enhancing the long-term durability and safety of anchorage support systems in extreme underground engineering environments. Full article

Understanding the hydration kinetics of cement paste is essential for adjusting the early-age performance of concrete. Low-field nuclear magnetic resonance (LF-NMR) has emerged as an innovative technique to evaluate cement hydration progress by analyzing the evolution of transverse relaxation time (T₂) signals. This study provides insights into the influence of a super-absorbent polymer (SAP) as an internal curing agent and calcium oxide (CaO) as an expansive agent (EA) on LF-NMR spectroscopy of cement paste for the first time. The chemical compositions of the cement and CaO-based EA were determined by X-ray fluorescence, while the morphological characterizations of the cement, SAP and CaO-based EA materials were characterized by scanning electron microscopy. Based on the extreme points in the first-order derivatives of the T₂ signal maximum amplitude curve, the hydration progress was analyzed and identified with four stages in detail. The results showed that the use of the SAP with a higher content retarded the hydration kinetics more evidently at a very early age, thus prolonging the duration of the induction and acceleration stages. The use of the CaO-based EA shortened the induction, acceleration and deceleration stages, which verified its promotion of hydration kinetics in the presence of the SAP. The combination of 3 wt% SAP and 2 wt% CaO consumed more water content synergistically in the first 100 h by hydration reactions. These findings revealed the roles of SAP and CaO-based EA (commonly adopted for low-shrinkage concrete) in adjusting hydration parameters and the microstructure evolution of cement-based materials, which would further offer fundamental knowledge for the early-age cracking control of concrete structures. Full article

As the average temperature in summer rises and heat waves occur more frequently, the urban heat island (UHI) phenomenon is becoming a social problem. Asphalt road pavement stores heat during the day, raising the surface temperature, and releases the stored heat at night, thereby aggravating the UHI phenomenon. Government authorities often spray water to lower the temperature of road pavement for the safety and convenience of citizens. However, the effect is immediate and does not last long. Therefore, in order to reduce the urban heat island phenomenon by spraying water, the recovery time of the surface temperature must be delayed. In this study, Super Absorbent Polymer (SAP), a highly absorbent polymer that absorbs 100 to 500 times its weight in water, was applied to asphalt road pavement. SAP is commonly used in diapers, feminine hygiene products, soil moisturizers, and concrete, and its scope is gradually expanding. The purpose of this study is to reduce the urban heat island phenomenon by mixing the SAP into asphalt and to increase the latent heat flux by evaporating the water absorbed by the SAP, thereby delaying the recovery time of the surface temperature of the road pavement. In this study, the performance of asphalt mixtures mixed with the SAP and the thermal characteristics according to the mixing amount were analyzed. In this study, the physical properties and temperature reduction performance of the asphalt mixture according to the SAP type and content were studied. The results of indoor and outdoor experiments on asphalt mixtures using the SAP showed that they satisfied the mechanical performance criteria as asphalt pavement materials and that the temperature recovery delay effect was improved. Full article

Recycled concrete incorporating additional super-absorbent polymer (SAP) and machine-made stone powder (MSP) was prepared using a two-factor, four-level orthogonal test. To enhance the frost resistance of recycled concrete and improve its mechanical properties, such as compressive and flexural strength, the prepared concrete underwent 200 freeze–thaw cycles. Before freeze–thaw cycles, the amount of SAP has a predominant influence on the mechanical properties of recycled concrete in comparison with MSP. After 200 cycles of freeze–thaw, the influence of MSP became more significant than that of SAP. Typically, the compressive strength and flexural strength exhibited a trend of initially increasing and then decreasing as the contents of SAP and MSP increased. The optimized recycled concrete was identified as S16M6, containing 0.16% SAP and 6% MSP, as demonstrated by the minimal strength loss after freeze–thaw cycles. This study also proposed a linear regression model for predicting the mechanical properties which offered valuable guidance for the engineering application of recycled concrete mixed with SAP under the freeze–thaw cycle environment. Full article

As precious cultural heritage, earthen sites are susceptible to various natural factors, leading to diverse forms of degradation. To protect earthen sites, the effects of super absorbent polymers (SAPs) on soil water retention, physical properties, and color compatibility at different concentrations were studied. After applying SAP treatment to an earthen site with different degrees of weathering, we drew the following conclusions. SAP-2 improved soil water retention capacity, increased soil water content, and slowed down the precipitation of soluble salts. At the same time, SAP-2 had the least effect on soil color difference and reduced the development of cracks by filling soil pores and enhancing the cohesion between soil particles, thus giving the earthen sites better weathering resistance. Therefore, the results provide a useful reference for the surface cracking of earthen sites in semi-arid areas and the degradation caused by flaking and block spalling. Full article

In light of the growing plastic waste problem worldwide, including in agriculture, this study focuses on the usefulness of both conventional, non-degradable plastics and environmentally friendly bioplastics in the agricultural sector. Although conventional plastic products are still essential in modern, even ecological agriculture, the increasing contamination by these materials, especially in a fragmented form, highlights the urgent need to search for alternative, easily biodegradable materials that could replace the non-degradable ones. According to the literature, polymers are widely used in agriculture for the preparation of agrochemicals (mostly fertilizers) with prolonged release. They also play a role as functional polymers against pests, serve as very useful super absorbents of water to improve crop health under drought conditions, and are commonly used as mulching films, membranes, mats, non-woven fabrics, protective nets, seed coatings, agrochemical packaging, or greenhouse coverings. This widespread application leads to the uncontrolled contamination of soil with disintegrated polymeric materials. Therefore, this study highlights the possible applications of bio-based materials as alternatives to conventional polyolefins or other environmentally persistent polymers. Bio-based polymers align with the strategy of innovative agricultural advancements, leading to more productive farming by reducing plastic contamination and adverse ecotoxicological impacts on aquatic and terrestrial organisms. On the other hand, advanced polymer membranes act as catching agents for agrochemicals, protecting against environmental intoxication. The global versatility of polymer applications in agriculture will not permit the elimination of already existing technologies involving polymers in the near future. However, in line with ecological trends in modern agriculture, more “green” polymers should be employed in this sector. Moreover, we highlight that more comprehensive legislative work on these aspects should be undertaken at the European Union level to guarantee environmental and climate protection. From the EU legislation point of view, the implementation of a unified, legally binding system on applications of bio-based, biodegradable, and compostable plastics should be a priority to be addressed. In this respect, the EU already demonstrates an initial action plan. Unfortunately, these are still projected directions for future EU policy, which require in-depth analysis. Full article

The water-retaining and yield-increasing capacity of super-absorbent polymer (SAP) are essential for soil remediation in arid and semi-arid areas. Water availability is an increasing challenge to plant development and crop yield. During the growing seasons in 2021 and 2022, the present study was conducted to evaluate the effect of the addition of different amounts of SAP on the development and yield of green beans (Phaseolus vulgaris L. cv Bronco) under varying water deficit stresses, compared with the control treatment without SAP and water deficit stress. The results demonstrated that a 50% reduction in water requirement (WR) resulted in significant decreases in leaf fresh weight, specific leaf area, leaf total chlorophyll content, pod number, leaf free water content, pod fresh weight per plant, and yield. Decreases were also found in pod total chlorophyll content, carotenoids, dry matter and total protein, leaf proline content, and crude fiber content. Additionally, leaf water saturation deficit was significantly increased under the stress compared with the full irrigation at 100% WR. However, irrigation at 75% WR increased pod contents of ascorbic acid, total sugars, and leaf bound water. The current study also indicated that addition of SAP significantly enhanced the above-mentioned growth characteristics under irrigation at 50% and 75% WR. Treatment with SAP at 3 g/plant was the most effective in mitigating the adverse effects of water deficiency, especially at the irrigation rate of 75% WR. Pearson’s correlation analysis showed significantly positive correlations between the growth parameters, as well as pod yield, under water stress and SAP. This study provides a promising strategy for green bean cultivation by adding SAP to soil to alleviate water shortage stress. Full article

Extreme weather and the declining organic matter content of soils cause serious sustainability problems in agriculture. Therefore, soil conditioner composites (chicken manure, bentonite and super absorbent polymer) were developed and tested in an integrated apple orchard characterized by poor nutrient and water management to study their effects on soil, leaf and fruit attributes. Composites with higher doses of additives increased soil organic carbon by 4–9 g/kg, and organic nitrogen by 1.8–2.8 g/kg compared to the control (p < 0.05). Similarly, soil nitrate content steadily increased from 8–10 mg/kg to 30–38 mg/kg by composites. Composites effectively elevated leaf N, K, Ca, and Mg while not affecting the leaf P (p < 0.05). Treatments significantly enhanced the yields by 14–63% on average compared to the control. Treatments with bentonite improved the fruit weight by 2% and 24% compared to the chicken manure. On average, composite treatments increased the titratable acidity of fruits by 26–43% compared to the control and 0.5–10% compared to the treatment containing solely chicken manure. Overall, the developed organic-based composites are able to cope with changing circumstances that could help mitigate the negative effects of climate change, especially in arid areas, thus contributing to sustainable nutrient management. Full article

In this study, the influence of a super absorbent polymer (SAP) addition on the thermal properties of phase change material (PCM) was investigated. It was found that adding SAP reduced the melting temperature of PCM and improved phase separation properties. While the addition of 1.0 wt% of SAP to PCMs decreased latent heat by 3 J/g to 24.4 J/g, the addition was determined to be necessary to prevent leaks from a functional duct unit (FDU) and assure product stability. The results obtained from a series of brine refrigeration tests indicate that the supercooling temperature decreased by 0.3 °C to 1.7 °C when 1.0 wt% of SAP was added to PCM. The addition of SAP to PCM appears to promote supercooling by encouraging condensation during phase change. As a result of applying SAP-added PCM to the FDU, the isothermal operation performance was improved compared to existing refrigerators. Full article

Concrete self-healing technology is an effective method for autonomously repairing cracks, which can reduce the maintenance costs of concrete components and prolong their service life. This study investigates the mechanical properties and self-healing abilities of mortar with internally mixed superabsorbent polymers (SAPs) and crystalline admixtures (CAs). The compressive strength and recovery rate of the specimens were evaluated, and the self-healing performance of concrete specimens was assessed through water absorption tests and optical microscopy observation of healed cracks. Microscopic analysis of the crack fillings was conducted using SEM-EDS and XRD tests, revealing the mechanism of the synergistic effect of SAPs and CAs on self-healing. The results indicate that the physical filling effect of SAPs’ water absorption and expansion almost completes the healing action before the 7-day healing age, with a weakened healing ability after this age. The chemical action of CA activation continues to heal cracks up to the 90-day healing age. When SAPs and CAs are incorporated together into the concrete matrix, the mortar specimens exhibit the best healing ability before the 7-day healing age. As water is released from the SAPs, the ongoing activation reaction of CAs shows the most effective healing result at the 90-day age. SEM-EDS analysis confirmed that the addition of CAs increases the Ca/Si ratio of calcium silicate hydrated, transforming it from an amorphous cluster structure to a needle-like structure. Furthermore, the internal curing effect of SAPs promotes the activation reaction of CAs, resulting in a greater quantity of more densely structured calcium silicate hydrated. Full article

In this investigation, a comprehensive assessment was conducted on the cooperative effects of Super Absorbent Polymers (SAP), limestone powder, and white cement within the realm of fair-faced concrete. We discerned that while white cement augments the color vibrancy of the concrete, its accelerated hydration rate potentially induced early-stage cracks and compromised performance. To mitigate these challenges, SAP was incorporated to regulate early hydration, and limestone powder was introduced as a fortifying agent to bolster the mechanical robustness of the concrete. Our findings highlighted not only the capability of SAP to enhance concrete workability and longevity but also the pivotal role of limestone powder in amplifying its mechanical attributes. Microscopic evaluations, undertaken via Scanning Electron Microscopy (SEM), unveiled the potential of both SAP and limestone powder in refining the microstructure of the concrete, thereby elevating its performance metrics. Synthesizing the research outcomes, we pinpointed an optimal amalgamation of SAP, limestone powder, and white cement in fair-faced concrete, offering a valuable reference for prospective architectural applications. Full article