Preparation and Charcterization of Konjac Superabsorbent Polymer

A superabsorbent polymer was prepared by grafting sodium acrylate （ SA ） onto Konjac flour using potassium persulfate （KPS） and N, N＇-methylene bis acrylamide （ MBA ） as an initiator and crosslinker , respectively. The effect of various preparation conditions on its water absorbency was investigated. When the Konjac Flour content was 3.0g, the acrylic acid （AA） content was 30.0 g, the amount of initiator was 0. 150 g, the neutralization degree of monomer was 85% , the reaction temperature was 60 ℃ and the amount of crosslinker was 0.025 g, the polymer＇s absorbency was 750 times in pure water and 279 times in tap water at ambient temperature. It had also high water retention. The graft efficiency reached 67% . The analyses of FT-IR and SEM indicate that sodium acrylate is grafted on the polysaccharides of Konjac flour.

A Novel Method for Studying the Re-Swelling Capacity of Superabsorbent Polymers in An Artificial Crack

Re-swelling capacity is a key factor influencing the self-sealing efficiency of superabsorbent polymers (SAPs) in concrete.In this paper,a new parameter (re-swelling ratio,η),the volume ratio of the crack which was filled with the expansive SAPs and the dry SAPs,was given to quantify the re-swelling capacity of a single SAPs particle.An innovative immersion test was used to study the η value of SAPs in the hardened cement paste with an artificial crack.Moreover,the influence of the crack width and particle size on the sealing efficiency of SAPs in the cracked paste was investigated by a water permeability test.The results showed that the mass ratios of the expansive SAPs in an artificial crack were less than those in a free state.The η value of SAPs in the hardened paste with an artificial crack increased with the increase of the crack width due to the restricting effects of the crack.The expansive SAPs in the cracked paste could totally seal or partly seal the crack within the original void.Moreover,the sealing efficiency of SAPs slightly increased with the rise of the crack width (0.25 to 0.5 mm) and the reduction of the particle size.This research demonstrates that the crack width in concrete and the particle size of SAPs are the key factors influencing the re-swelling behavior of SAPs which should be taken into consideration when designing the self-sealing concrete containing SAPs.

Experimental Synthesis of Polyacrylic-Type Superabsorbent Polymer and Analysis of Its Internal Curing Performances

A solution polymerization method has been used to synthesize a polyacrylic-type superabsorbent polymer(SAP).The influence of various influential factors,such as the temperature,neutralization degree,cross-linking agent,and initiator,on the water absorption capacity of SAP has been investigated.The results show that the absorption can display a non-monotonic behavior depending on the synthesis conditions.The absorption can also change according to the pH,ion types and ion concentration.As the pH value increases,the water absorption capacity decreases significantly.It also decreases if the N^(a+)concentration becomes higher and becomes particularly low in solutions containing Mg^(2+).With the addition of SAP,the compressive strength of cement mortar decreases;the internal relative humidity can be maintained at 96%within 200 hours;and autogenous shrinkage can be reduced by nearly 69%.

An Investigation into the Performances of Cement Mortar Incorporating Superabsorbent Polymer Synthesized with Kaolin

Cement-based materials are fundamental in the construction industry,and enhancing their properties is an ongoing challenge.The use of superabsorbent polymers(SAP)has gained significant attention as a possible way to improve the performance of cement-based materials due to their unique water-absorption and retention properties.This study investigates the multifaceted impact of kaolin intercalation-modified superabsorbent polymers(K-SAP)on the properties of cement mortar.The results show that K-SAP significantly affects the cement mortar’s rheological behavior,with distinct phases of water absorption and release,leading to changes in workability over time.Furthermore,K-SAP alters the hydration kinetics,delaying the exothermic peak of hydration and subsequently modifying the heat release kinetics.Notably,K-SAP effectively maintains a higher internal relative humidity within the mortar,reducing the autogenous shrinkage behavior.Moreover,K-SAP can have a beneficial effect on pore structure and this can be ascribed to the internal curing effect of released water from K-SAP.

Hydration, microstructure and autogenous shrinkage behaviors of cement mortars by addition of superabsorbent polymers

Superabsorbent Polymer(SAP)has emerged as a topic of considerable interest in recent years.The present study systematically and quantitively investigated the effect of SAP on hydration,autogenous shrinkage,mechanical properties,and microstructure of cement mortars.Influences of SAP on hydration heat and autogenous shrinkage were studied by utilizing TAM AIR technology and a non-contact autogenous shrinkage test method.Scanning Electron Microscope(SEM)was employed to assess the microstructure evolution.Although SAP decreased the peak rate of hydration heat and retarded the hydration,it significantly increased the cumulative heat,indicating SAP helps promote the hydration.Hydration promotion caused by SAP mainly occurred in the deceleration period and attenuation period.SAP can significantly mitigate the autogenous shrinkage when the content ranged from 0 to 0.5%.Microstructure characteristics showed that pores and gaps were introduced when SAP was added.The microstructure difference caused by SAP contributed to the inferior mechanical behaviors of cement mortars treated by SAP.

Effect of superabsorbent polymer on mechanical properties of cement stabilized base and its mechanism

Superabsorbent polymers(SAPs)are cross-linked polymers that can absorb and retain large amounts of water.In recent years,a growing interest was seen in applying SAPs in concrete to improve its performance due to its efficiency in mitigating shrinkage.This paper presents findings in a study on effect of SAPs on performance of cement-treated base(CTB),using the experience of internal curing of concrete.CTB specimens with and without SAPs were prepared and tested in the laboratory.Tests conducted include mechanical property testing,dry shrinkage testing,differential thermal analysis,mercury intrusion porosimetry and scanning electron microscope testing.It was found that 7-day and 28-day unconfined compressive strength of CTB specimens with SAPs was higher than regular CTB specimens.28d compressive strength of CTB specimens with SAPs made by Static pressure method was 5.87 MPa,which is 27%higher than that of regular CTB specimens.Drying shrinkage of CTB specimens with SAPs was decreased by 52.5%comparing with regular CTB specimens.Through the microstructure analysis it was found that CTB specimens with SAPs could produce more hydration products,which is also the reason for the strength improvement.

Synthesis of Acrylic Acid/Kaoline Powder Superabsorbent Composite by Inverse-suspending Polymerization

An acrylic acid/kaoline powder superabsorbent composite with a water absorbency of the superabsorbent composite about 1/800 was synthesized by inverse\|suspending polymerization reaction between acrylic acid monomer and kaoline ultrafine powder. The influence of the dispersant agent on the configuration of the products in the inverse suspension polymerization is investigated. The influences of the kaoline powder,cross\|linker,initiator,neutralization degree and the volume ratio of oil to water phase on the water absorbency of the superabsorbent composites are discussed in the paper.

Super-absorbent swellable polymer as grouting material for treatment of karst water inrush

Grouting is the most commonly used method to control water inrush in underground engineering.Traditional cement-based materials are easy to dilute and hard to coagulate under the influence of large flow and high-velocity water inrush.To address these deficiencies,a new type of polymer grouting material with an excellent expansion ratio was synthesised.The material quickly absorbs water and has an expansion ratio of 1:300.The material is composed of a superabsorbent polymer(SAP),glycerol,and ethanol.The effects of water quality on the expansion ratio and expansion rate of the material were examined,and the best solid–liquid ratio for the slurry was determined by fluidity measurements.A karst specially designed pipeline water inrush test device showed that 800 g of SAP can achieve 0.6 m/s water flow blockage in the smooth pipeline,demonstrating that the ability of the SAP slurry to block water inrush is superior to those of other materials.This study provides a reference for water inrush plugging,and has important implications for the reduction and control of karst pipeline-type water inrush disasters,ensuring the safety of construction sites and preventing loss of life and damage to property.

Properties and Structure of Microcrystal Muscovite Composite Superabsorbent

Microcrystal muscovite composite superabsorbents（MMCSA） were prepared by water solution polymerization using acrylic acid, acrylamide and itaconic acid as comonomers and microcrystal muscovite as an inorganic additive. Properties, such as water absorbency, salt absorbency, gel strength, water retention capacity and structure of MMCSA characterized by SEM and XRD, were investigated. Water absorbency, salt absorbency, gel strength, water retention capacity and thermostability were enhanced by incorporation of suitable amount of microcrystal muscovite. Water absorption of MMCSA was rapid, requiring 24.55 min to reach 63% of equilibrium absorbency（1218 g/g）. Microcrystal muscovite was physically combined into the polymeric network without destroying its polycrystalline structure and microcrystal muscovite composite superabsorbent had some irregular, undulant, and small microporous holes with sheet-like microcrystal muscovite distributed in the polymeric matrix.