Superabsorbent Polymer Hydrogels Research Articles

Performance enhancement of cement mortar with superabsorbent polymer composite internally embedded with porous ceramsite sand

Superabsorbent polymer (SAP), which can act as water reservoir, was an internal curing (IC) agent with great potential to reduce the shrinkage and cracking of cement-based materials. However, the volume shrinkage of SAP after water release will lead to the formation of additional voids, which will lead to a clear reduction of mechanical properties. In present work, a novel SAP composite with a rigid skeleton (IP-PS) was synthesized by embedding in-situ polymerized SAP hydrogel into the pores of porous ceramic (PS). The results demonstrated that the compressive strength of IP-PS0.054 was above 10 % higher than that of SAP0.054 in the early and late stages, the compressive strength of IP-PS0.054 at 28 days reached 97.71 % of that of the control group, which was predominantly ascribed to the support provided by the embedded skeleton. The development of self-desiccation was also notably delayed by the incorporation of IP-PS, as evidenced by the approximately 12 % reduction compared to SAP0.054 and 47 % reduction compared to Control group in 7-day autogenous shrinkage, which was on account of the enhanced water storage and durable IC capacity of IP-PS. Furthermore, the impermeability of cement-based materials was also improved by the in-situ polymerized hydrogel modification.

Experimental Study of a Superabsorbent Polymer Hydrogel in an Alkali Environment and Its Effects on the Mechanical and Shrinkage Properties of Cement Mortars.

As internal curing self-healing agents in concrete repair, the basic properties of superabsorbent polymers (SAPs), such as water absorption and release properties, are generally affected by several factors, including temperature and humidity solution properties and SAP particle size, which regulate the curing effect and the durability of cementitious composites. This study aimed to investigate the water retention capacities of SAPs in an alkaline environment over extended periods by incorporating liquid sodium silicate (SS) into SAP-water mixtures and examining the influence of temperature. The influence of SAP particle size on mortar's water absorption capacity and mechanical behavior was investigated. Two mixing techniques for SAPs (dry and pre-wetting) were employed to assess the influence of SAP on cement mortars' slump, mechanical properties, and cracking resistance. Four types of SAPs (SAP-a, SAP-b, SAP-c, and SAP-d), based on the molecular chains and particle size, were mixed with SS to study their water absorption over 30 days. The results showed that SAPs exhibit rapid water absorption within the first 30 min, exceeding 85% before reaching a saturation point, and the chemical and temperature variations in the water significantly affected water absorption and desorption. The filtration results revealed that SAP-d exhibited the slowest water release rate, retaining water for considerably longer than the other three types of SAPs. The mechanical properties of SAP mortar were reduced due to the addition of an SAP and the improved cracking resistance of the cement mortars.

Design and manufacture of new hybrid hydrogel and superabsorbent polymer for controlled release of fulvic acid based on grafted xanthan gum/gelatin using electron irradiation and its use in fodder corn cultivation

A humic acid-gelatin (HA-Gel) hydrogel, a gallic acid-xanthan gum (GA-XG) hydrogel, a HA-Gel/GA-XG hydrogel, and superabsorbent polymer (SAP) of HA-Gel/GA-XG/polyacrylamide (PAM) hydrogel were synthesized using electron beam irradiation method. The capability of synthesized hydrogels in loading and controlled release of fulvic acid (FA) was studied. The chemical and physical structure of sorbents was confirmed by various analyses. The effect of irradiation dose on mechanical properties, gel percentage, swelling, and absorbency under load (AUL) of the sorbents was investigated. By changing the hydrogel structures into the SAP form, its swelling capacity was increased from 37 to 320 g/g. Both hybrid hydrogel and SAP were reusable for up to 7 cycles. The maximum fertilizer loading capacities for SAP and hybrid hydrogel were 402.1 and, 175.5 mg g−1, respectively. In comparison to hydrogels, the SAP showed a slower FA-release performance. Thus, in soil media, 86 % of FA was released in 15–20 days from the hybrid hydrogel while with the SAP, 81 % of FA was released in 30–35 days. The significant improvement in the growth of fodder corn treated with FA-loaded SAP in the greenhouse media in comparison to the control groups showed the effective performance of the designed SAP, favoring its practical applications.

Dalbergia nigra (Vell.) grown using hydrogel planting methods in the establishment of a silvopastoral system in a degraded soil

This work tested the use of a superabsorbent polymer (hydrogel) in a silvopastoral system with Brazilian-rosewood (Dalbergia nigra (Vell.) Allemão ex Benth.) in a degraded pasture area. The experimental site is part of the Bananal do Norte experimental farm, Cachoeiro de Itapemirim, Espírito Santo, Brazil. Over 480 seedlings were planted and submitted to the treatments: Dry hydrogel (DRY); Hydrated hydrogel around the root ball (HAR); Hydrated hydrogel mixed with soil (HMS); and water only (WAT). The design was in randomized blocks, with three repetitions. The tested variables were plant survival, height and root collar diameter until 672 days after planting, soil moisture at 93 days after planting and total biomass and leaf chemical analysis at 184 days after planting. Survival was positively influenced by the application of the hydrogel, but there was little or no effect regarding the application method. The hydrogel and its application techniques did not alter growth in height and root collar diameter. The polymer did not influence the development in biomass and nutritional content of the leaves, but did influence the biomass distribution. The use of the superabsorbent polymer was therefore not effective in accelerating plant growth and anticipating the stages in the implantation of the silvopastoral system. Keywords: agroforestry, brazilian-rosewood, degraded pasture.

Durability of Concrete with Superabsorbent Polymer (SAP) Assessed Using Depth of Carbonation and NDT Ultrasonic Methods.

The paper concerns destructive and non-destructive (NDT) evaluation of the effect of the addition of superabsorbent polymer (SAP) used as a carrier of mixing water and a means of internal curing on the durability of concrete. The research concerns testing of five concretes-an ordinary reference concrete and four concretes differing in the content of mixing water introduced into the concrete mix in the form of pre-saturated SAP particles (25%, two variants of 50% and 75% of the total mixing water in the form of SAP hydrogel). The research consisted of 4 stages of tests. The subsequent stages involved the analysis of the effect of using SAP as a carrier of mixing water on the particular characteristics of concrete mix and hardened concrete, i.e., consistency and density of concrete mix (1st stage), carbonation tested using two indicators-phenolphthalein and thymol phenolphthalein (2nd stage), and finally: the homogeneity of the concretes' structure by means of ultrasonic method (determination of ultrasonic pulse velocity) 28 days after production (3rd stage) and 3 years after production (4th stage). The ultrasonic pulse (or wave) velocity was then correlated with the content of water applied in the form of SAP hydrogel. The statistical analysis of results showed that the method of introducing the mixing water into the concrete mix in the form of pre-absorbed superabsorbent polymer, although it changed the concrete mix consistency, did not significantly affect the concrete ability to resist carbonation. Meanwhile, after 3 years, the densification of the microstructure of concrete with SAP has been observed.

ZnO-Loaded SA-g-Poly (AC-co-EBS) Hydrogel Nanocomposite as an Efficient Adsorption of Tetracycline and Phenol: Kinetics and Thermodynamic Models

A synthetic superabsorbent polymer hydrogel nanocomposite was prepared by the free radical graft co-polymerization method. This study included the preparation of two surfaces: first sodium alginate-g-(acrylic acid-co-sodium; 4-ethenylbenzenesulfonate), SA-g-poly (Ac-co-EBS) hydrogel, and second surface hydrogel after zinc oxide loading SA-g-poly (Ac-co-EBS). Hydrogel nanocomposite was prepared from different monomers for the removal of pollutants. The physical characterizations of nanocomposite have been studied using several techniques like UV-vis, FTIR, FE-SEM, TEM, EDX, and XRD. The data from the adsorption study show that E% increases with increasing contact time, with the best agitation time of 1 h, after which the adsorption becomes constant. The increase in adsorbent amount 0.01–0.1 g, the percentage removal of tetracycline (TC) and phenol (PH) increased from 60.639–97.085 and 487.71–94.05%, respectively, and Qe decreased 606.39–97.08 to 487.1831–94.456 mg/g on hydrogel. The ∆H value is endothermic. All processes of adsorption are considered spontaneous, from a negative value of ∆G to a positive value of ∆S. The release of the TC drug was studied in conditions similar to those in the human body in terms of acidity and temperature. The cumulative release of TC drug in 3 h was 50.65%, 42.33%, pH = 7.5 and pH 1.2, respectively.

Improving Coffee Bean Drying Performance Using Polydryer (Dryer Assisted with Superabsorbent Polymer)

Superabsorbent polymer is a material that can swell hundreds to thousands of times after absorbing moisture. Studies that combined the use of this material in coffee bean drying have not yet been widely disclosed. In this study, a dryer assisted with superabsorbent polymer (Polydryer) was applied to improve the drying performance of coffee beans. The materials for superabsorbent polymer hydrogel (polygel) were cassava starch and acrylic acid. Based on this study, the use of polygel and heater was able to alleviate humidity while signifying the temperature inside the drying chamber. This condition certainly aided the drying process because it provided a greater driving force for free and bound water to diffuse from the inner coffee bean particle to the environment. Normal and intermittent drying modes were also carried out to compare the drying performance. The normal operation mode required 14 h to attain a product moisture content of below 12%. Meanwhile, the intermittent drying mode, where the heater operated merely in the initial stage, took 72 h to reach the maximal 12% product moisture content. Further improvement of the Polydryer was done by using three chambers arranged in series and operating in the normal mode, resulting in a more efficient drying system with a swifter process of 7 h. The results indicated that coffee bean drying using the Polydryer was effective and can be used to substitute conventional methods, especially during the night‐time and rainy season. Besides, the dried coffee beans were free of insects, rot, mold, and foreign matter and were in a specialty grade category.

Influence of nano alumina reinforced superabsorbent polymer on mechanical, durability, microstructural and rheological properties of cementitious materials

Superabsorbent polymers (SAPs) are widely used in concrete for their promising effect in internal curing and crack sealing. Nano materials are efficient in improving the permeability and porosity of concrete with their smaller size and larger surface area. In this research , polyacrylamide (PAM) as superabsorbent polymer (SAP) along with nano alumina (NA) is proposed for small percentage of replacement in cement and their effects on mortar concrete were studied for mechanical and microstructural properties under self-curing and wet curing conditions. This study investigates the combined influence of nano alumina and polyacrylamide superabsorbent polymer hydrogel on chemical durability of cement mortar with HCl, CaCl2, and Na2SO4 immersion for 180 days. The effectiveness of replacing cement by composite mixture of polyacrylamide superabsorbent polymer and nano alumina at 0.1%, 0.2%, 0.3%, 0.4% and 0.5%, by weight, was investigated. Nano alumina modified by SAP was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR) studies. Results indicate that NA/SAP combination in concrete improves hydration of cement enhancing the mechanical properties in concrete and similar properties are obtained in self-curing conditions indicating that SAP is good internal curing agent in concrete and NA is useful in filling up micro pores in concrete enhancing their strength. Hence, a composite admixture is proposed in concrete through this work for low-shrinkage, compact and dense concrete for the application in practical engineering.

Salicylic Acid and Superabsorbent Polymers Could Alleviate Water Deficit Stress in Camelina (Camelina Sativa L.)

ABSTRACT Agronomic management and application of growth regulators mitigated the negative effects of water deficit and improved seed oil yield and other traits in camelina. This study assessed the effects of salicylic acid (SA) foliar application and soil application of superabsorbent polymer hydrogel (SPH) on the growth and antioxidant production of camelina (Camelina sativa L.) in 50% and 75% field capacity (FC) groups, as well as in a well-watered treatment. Application of SA and SPH significantly increased camelina yield and its components in 75% FC and well-watered treatments. In the control (no SA or SPH), water deficit reduced seed oil by 13% and 35% in 75% FC and 50% FC, respectively. Application of SA and SPH increased seed oil by 5% and 11%, respectively. Photosynthetic rate (A), stomatal conductance (gs), and chlorophyll content decreased in the 75% FC and 50% FC treatments. Application of SA and SPH increased in A (26% and 19%) and gs (17% and 12%) compared to the control. Superoxide dismutase (SOD), peroxidases (POD), catalases (CAT), and ascorbate peroxidase (APX) activity increased with increased drought stress. The activity of these enzymes increased when SA was applied. Generally, foliar application of SA was more effective than soil application of SPH in camelina to alleviate the injurious effects of drought stress.

Effect of Superabsorbent Polymer Hydrogels in the Advancement of Cementitious Materials– A Review

Effect of Superabsorbent Polymer Hydrogels in the Advancement of Cementitious Materials– A Review

Investigation on Performances and Functions of Asphalt Mixtures Modified with Super Absorbent Polymer (SAP).

The super absorbent polymer (SAP) has been attracting extensive concerns due to its strong capacity in water absorption and retention. The amorphous hydrogels formed by the post-absorbent SAP have the potential of clogging the micro-cracks in asphalt materials and refraining the rainwater from infiltrating. This provides the possibility of applying SAP in asphalt pavements to seal or fill the cracks and relieve the distresses caused by rainwater infiltration in the underlying layers. Before exploring the cracking sealing mechanism of SAPs in asphalt pavements, a series of experiments were performed to evaluate the feasibility and influences of SAPs in asphalt mastics and asphalt mixtures on their mechanical performances and functionalities. Firstly, the basic properties of SAPs were analyzed, and then the rheological properties of the asphalt mastics using SAP replacing mineral powder (10%, 20%, 30%, and 40% by volume) were explored. The water stability and infiltration reduction effect of the asphalt mixtures incorporated with SAP were evaluated by the Marshall stability test, immersion Marshall stability test, freeze-thaw splitting strength test, Cantabro test, and permeability test. The test results indicated that SAPs could be used in the asphalt mixtures to partially substitute mineral powder with desirable mechanical performances. When less than 10% of the mineral powder was replaced by the SAP, the high-temperature performance and fatigue life of the asphalt mastics could be improved to some extent, but both declined after the content of the SAP was larger than 10%. Due to the hydrogels formed by SAPs after water absorption, the water stability of the asphalt mixtures deteriorated with the increased content of SAPs. Moreover, the results from the permeability tests implied that the SAP hydrogels could fill the seepage channels in the material, thus improving the migration and infiltration resistances of the asphalt mixtures. With the increased contents of SAPs, the permeability coefficients of the asphalt mixtures could be reduced up to 55%. Based on the research findings in this study, when an appropriate amount of SAP was added in the asphalt materials, desirable temperature stability, water stability, and fatigue resistance could be achieved regarding actual requirements from applications. At the same time, the addition of SAPs could effectively refrain the infiltration and migration of rainwater in asphalt pavements, thus potentially mitigating the effect of water erosion on the underlying layers.

Effect of super-absorbent polymer on swelling pressure of compacted bentonite infiltrated by alkaline solutions

The application of bentonite in geological disposal of radioactive waste is still under evaluation, especially concerning the decreased swelling pressure of pure bentonite exposed to alkaline groundwater. In this paper, in order to improve the chemical resistance of bentonite to alkaline solutions, super-absorbent polymer (SAP), a hydrophilic polymer with much higher swelling ability than that of bentonite, was dry-blended with Gaomiaozi (GMZ) bentonite and compacted into blocks of different dry densities. Swelling pressure of the bentonite-SAP composites infiltrated with deionized water, NaOH and KOH alkaline solutions were tested, accompanied with scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and X-ray diffractometer (XRD) tests conducted on the selected specimens. Results showed that, for the specimens hydrated by deionized water, the swelling pressure increased with increasing SAP content, dry density and concentration of NaOH solutions. With increasing concentration of KOH solutions, however, the swelling pressure decreased obviously and tended to undergo a slow long-term degradation. Results of SEM, MIP and XRD indicate that the SAP hydrogels swell extensively to clog the inter-aggregate pores and coat the aggregates (for high density specimens) or montmorillonite stacks (for low density specimens), while do not insert into the interlayer spaces. The swelling pressure was therefore mainly contributed by the crystalline swelling of montmorillonite and the osmotic swelling of SAP. The SAP chains could be associated with the montmorillonite crystallites, protecting them from chemical attack and thus improving the chemical resistance of bentonite to alkaline solutions.

Alkali Lignin-Based Hydrogel: Synthesis, Characterization, and Impact on Soil Water Retention From Near Saturation to Dryness

Highlights A lignin-based hydrogel was synthesized and shown to possess a swelling ratio of 2013%. The hydrogel contained important hydrophilic hydroxyl groups and macropores for water retention. The hydrogel improved soil water retention in silt loam soil at high matric potentials and in the dry soil range. Increasing hydrogel concentration increased water retention in a loamy fine sand soil at high and low matric potentials. Abstract. Superabsorbent polymers (hydrogels) have been proposed as soil amendments to increase the amount of plant-available water in the soil. Synthetic hydrogels have been widely investigated for use in agriculture. Due to increasing environmental concerns related to synthetic hydrogels, naturally sourced hydrogels are of interest because of their potential for increased biodegradability and biocompatibility. A lignin-based hydrogel was synthesized for this study, and its swelling properties and water absorption capacity were determined. The hydrogel was characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and gas pycnometry. A hanging water column, pressure plate apparatus, and dew point potentiometer were used to measure the soil water retention curve from saturation to oven-dryness for silt loam and loamy fine sand soils after amendment with the lignin-based hydrogel. Results showed a maximum swelling ratio in deionized water of 2013% of the hydrogel’s original mass, 1092% in tap water, and 825% in a 0.9% NaCl solution. The FTIR spectra of the hydrogel showed the presence of O-H bonds from the lignin structure, which renders the hydrogel reactive to a crosslinker and forms insoluble bonds, thereby allowing the hydrogel to swell when exposed to water. SEM images of the lignin hydrogels indicate large macropores, which allowed for water absorption. Applying hydrogels significantly increased the soil's water-holding capacity at 0.3% (w/w) treatment. Hydrogel treatment significantly increased water retention at saturation or near saturation by 0.12 cm3 cm-3 and at field capacity by 0.08 cm3 cm-3 for silt loam soil at 1% (w/w) treatment compared to the control treatment with no added lignin hydrogel. Hydrogel application increased water retention over the range of the soil water retention curve from -3 to -15,000 cm for the loamy fine sand soil at 1% (w/w) treatment. However, the application of lignin-based hydrogel did not affect plant available water capacity (PAWC) in either soil tested. These results serve as preliminary evidence upon which further lignin-based hydrogel amendment studies could be built by testing higher concentrations of hydrogel in the soil. Keywords: Lignin, Soil water retention curve, Super absorbent polymers, Swelling capacity, Water retention.

A better picker-upper: Superabsorbent “gel sheets” with fabric-like flexibility

<h2>Summary</h2> Materials to absorb aqueous liquids are either foldable cloth/paper towels (convenient to use but poorly absorbent), or superabsorbent polymer hydrogels (highly absorbent, but fragile when dried). Here, we create "gel sheets" that combine the best attributes from the above. Macrosized sheets (10 × 10 cm) are prepared by foam templating, followed by plasticization and ambient drying. The dried sheets are macroporous, flexible, soft, and robust; they can be folded, rolled up, and cut with scissors, much like fabrics. At the same time, like hydrogels, they substantially absorb water and <i>expand as they absorb</i>, which is unlike any sponges or towels. The sheets also absorb viscous liquids like blood and viscoelastic liquids like polymer solutions. Absorbed liquid is retained within the sheet when lifted, whereas excess liquid drips from towels. Such gel sheets could be used to clean up spills in homes, labs, and hospitals, and for absorbing biological fluids during surgeries.

The Impacts of Bio-Based and Synthetic Hydrogels on Soil Hydraulic Properties: A Review.

Soil hydraulic properties are important for the movement and distribution of water in agricultural soils. The ability of plants to easily extract water from soil can be limited by the texture and structure of the soil, and types of soil amendments applied to the soil. Superabsorbent polymers (hydrogels) have been researched as potential soil amendments that could help improve soil hydraulic properties and make water more available to crops, especially in their critical growing stages. However, a lack of a comprehensive literature review on the impacts of hydrogels on soil hydraulic properties makes it difficult to recommend specific types of hydrogels that positively impact soil hydraulic properties. In addition, findings from previous research suggest contrasting effects of hydrogels on soil hydraulic properties. This review surveys the published literature from 2000 to 2020 and: (i) synthesizes the impacts of bio-based and synthetic hydrogels on soil hydraulic properties (i.e., water retention, soil hydraulic conductivity, soil water infiltration, and evaporation); (ii) critically discusses the link between the source of the bio-based and synthetic hydrogels and their impacts as soil amendments; and (iii) identifies potential research directions. Both synthetic and bio-based hydrogels increased water retention in soil compared to unamended soil with decreasing soil water pressure head. The application of bio-based and synthetic hydrogels both decreased saturated hydraulic conductivity, reduced infiltration, and decreased soil evaporation. Hybrid hydrogels (i.e., a blend of bio-based and synthetic backbone materials) may be needed to prolong the benefit of repeated water absorption in soil for the duration of the crop growing season.

Adsorptive Removal of Methylene Blue Dye Using Biodegradable Superabsorbent Hydrogel Polymer Composite Incorporated with Activated Charcoal

Hydrogels have attracted great attention as good adsorbents due to their extraordinary water retention capacity, unique hydrophilic nature, biocompatibility, and abundance in availability. In this work, a superabsorbent polymer (SAP) hydrogel and its composite were synthesized, with the introduction of activated charcoal (SAP-AC) for deep removal of the ecotoxic organic dye methylene blue (MB). The formation of the hydrogel was confirmed by FTIR analysis, and scanning electron microscopy (SEM) revealed the appearance of a porous microstructure due to the incorporation of AC. A continuous upflow column was set up, and the adsorption parameters were optimized using an experimental Doehlert uniform array design. The residual concentration of MB was analyzed by UV-Vis spectrophotometry at 665 nm (λmax). The experimental data were also discussed in terms of adsorption kinetics and adsorption isotherm models. Accordingly, MB adsorption followed pseudo second-order kinetics and better fits the Freundlich isotherm, suggesting a chemisorption mechanism and a multilayer MB adsorption system. The maximum adsorption capacity was 202.84 mg g−1 (96.96%) using the SAP and 213.2 mg g−1 (99.48%) using the SAP-AC. The present study proved that the synthesized composite hydrogel has good activity and selectivity for deep removal of the MB dye and can be effectively used in wastewater treatment.

Laboratory Determination of the Impact of Incorporated Alkali Lignin-Based Hydrogel on Soil Hydraulic Conductivity

Superabsorbent polymers (hydrogels) have been studied for their ability to influence soil hydraulic conductivity because they can store and release water due to their swelling properties. However, concerns related to the increased use of synthetic hydrogels necessitates a switch to bio-based hydrogels, which are renewable and more biodegradable in comparison to synthetic hydrogels. In this study, we synthesized a lignin-based hydrogel and amended a silt loam soil with it at concentrations of 0, 0.1, and 0.3% (w/w). A laboratory permeameter, double membrane tension infiltrometer, and evaporation method were used to measure the saturated (Ks), near saturated, and unsaturated hydraulic conductivity (K) of the samples, respectively. Saturated hydraulic conductivity was significantly decreased by the application of hydrogel at 0.1 and 0.3% (w/w) in comparison to the control treatment. The application of 0.3% (w/w) lignin-based hydrogel only significantly decreased hydraulic conductivity at −1 cm soil water pressure head. Hydraulic conductivity in the 0.1 and 0.3% (w/w) treatments increased along the K(θ) curve in the unsaturated zone (−750 cm &lt; h &lt; −10 cm) in comparison to the control treatment, which we hypothesized was due to bound water in the hydrogel being released and creating a wider path for the movement of water. The 0.1 and 0.3% hydrogel treatments also tended to store more water than the control treatment, especially after 24 h of evaporation. The implication of this study is that lignin-based hydrogels could swell and retain water in saturated soils and the bound water could be released to enhance the flow of soil water in unsaturated soil, thereby reducing the water stress of plants, which require less energy to move and absorb water.

Application of Polyacrylic Hydrogel in Durability and Reduction of Environmental Impacts of Concrete through ANN.

While adding superabsorbent polymer hydrogel particles to fresh concrete admixtures, they act as internal curing agents that absorb and then release large amounts of water and reduce self-desiccation and volumetric shrinkage of cement that finally result in hardened concrete with increased durability and strength. The entrainment of microscopic air bubbles in the concrete paste can substantially improve the resistance of concrete. When the volume and distribution of entrained air are adequately managed, the microstructure is protected from the pressure produced by freezing water. This study addresses the design and application of hydrogel nanoparticles as internal curing agents in concrete, as well as new findings on crucial hydrogel–ion interactions. When mixed into concrete, hydrogel particles produce their stored water to power the curing reaction, resulting in less volumetric shrinkage and cracking and thereby prolonging the service life of concrete. The mechanical and swelling performance qualities of the hydrogel are very sensitive to multivalent cations found naturally in concrete mixes, such as aluminum and calcium. The interactions between hydrogel nanoparticles and alkaline cementitious mixes are described in this study, while emphasizing how the chemical structure and shape of the hydrogel particles regulate swelling behavior and internal curing efficiency to eliminate voids in the admixture. Moreover, in this study, an artificial neural network (ANN) was utilized to precisely and quickly analyze the test results of the compressive strength and durability of concrete. The addition of multivalent cations reduced swelling capacity and changed swelling kinetics, resulting in fast deswelling behavior and the creation of a mechanically stiff shell in certain hydrogel compositions. Notably, when hydrogel particles were added to a mixture, they reduced shrinkage while encouraged the creation of particular inorganic phases within the void area formerly held by the swelled particle.

Hydrophobic hydrogels as internal curing agent for concrete: The double benefit of super high water content and excellent anti-ion permeability

Owing to their high water content, conventional superabsorbent polymer (SAP) hydrogels can serve as internal curing agents for concrete fabrication. However, the hydrophilic network in such hydrogels permits ion diffusion, which induces severe steel corrosion inside concrete in the marine environment. Herein, we introduce a brand-new hydrogel, termed “hydrophobic hydrogels”, for concrete curing. On one hand, these hydrogels possess super high water content (up to 99.6 wt%), which is even higher than that in normal SAP hydrogels; on the other hand, the anhydrous inhomogeneous hydrophobic structures can significantly retard or stop the ion permeation, which is significantly superior to SAP hydrogels. With ion diffusion measurement, the hydrophobic hydrogels achieve much better ion resistance than SAP hydrogels, with 2–5 orders' decrease in ion permeation rate. Among diverse hydrophobic hydrogels, the polymer's hydrophobicity and glass transition directly determine the permeation performance. Hydrogels with a more hydrophobic network and higher polymer Tg possess better anti-ion diffusion properties. At the optimal state, the poly(phenyl acrylate) hydrophobic hydrogels can completely stop the permeation process. Owing to the double benefit, the hydrophobic hydrogel cured concretes demonstrate a notable decrease in ion permeation compared to SAP hydrogel cured concrete, with only 1/20 of ion permeation to that in SAP groups with an electric flux test upon coated on the surface layers. Owing to the double benefit from super high water content and excellent anti-ion permeability, these hydrophobic hydrogels may serve as ideal candidates as concrete curing agents in the future.

Conditions for selection of superabsorbent polymer hydrogel for cement compositions

Conditions for selection of superabsorbent polymer hydrogel for cement compositions