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.

Mechanical property of strain-hardening cementitious composites modified with superabsorbent polymers

In order to improve the tensile property, flexuralproperty and drying shrinkage of strain-hardening cementitiouscomposites （SHCC）, mixtures quantitatively modified withsuperabsorbent polymer （SAP） were investigated. Theuniaxial tensile test, the four-point bending test, thecompressive test, the drying shrinkage test and theenvironmental scanning electron microscope （ESEM） wereemployed to investigate the tensile strain capacity, flexuraldeformation capacity, compressive strength, drying shrinkage,crack width and self-healing of SHCC. The experimentalresults show that SHCC modified with SAP particles exhibitsexcellent ductility and deformability, and the tensile strain isup to about 4.5% and the average crack width is controlledaround 40 μm. Meanwhile, the drying shrinkage of SHCCmodified with SAP particles can reduce by about 60%.Furthermore, the self-healing behavior is observed in thecracks of specimen after three cycles of high-low relativehumidity curing, and the self-healing products can completelyfill the cracks of SHCC specimens modified with SAPparticles. It is, therefore, feasible to produce SHCC materialmodified with SAP particles, while simultaneously retaininghigher material ductility.

Effects of superabsorbent polymer particles on flexural properties and self-healing behavior of ECC

In order to improve the self-healing behavior and the recovery of mechanical properties of engineered cementitious composites(ECC),the approach of incorporating superabsorbent polymer(SAP)in mixtures is investigated.The rapid water penetration test and four-point bending test were conducted to evaluate the effects of self-healing on the water permeability and mechanical properties of pre-damaged ECC.The self-healing process and self-healing products were observed by the environment scanning electron microscope(ESEM)and energy dispersive X-ray spectroscopy(EDS).The experimental results show that all ECC mixtures exhibit excellent flexural capacity,meanwhile maintaining a crack width below 50μm.The incorporation of SAP particles in ECC can apparently improve the mechanical recovery of ECC mixtures after 10 healing curing cycles,such as flexural deformation and flexural stiffness.The flexural stiffness of ECC containing 4%SAP particles after self-healing can be recovered to 80%.The self-healing test results show that when the water permeability of ECC mixtures incorporating SAP particles is close to zero,only three healing cycles are needed.When ECC incorpora ting more SAP particles,the accelerated self-healing process can be finished in the first three cycles,and self-healing product is mixed Ca(OH)2/CaCO 3 with CaCO 3 being a major component in the later stage.It is,therefore,feasible to produce ECC materials incorporating SAP particles,while simultaneously maintaining higher material ductility and self-healing behavior.

Superabsorbent polymer for water management in forestry

The effectiveness of a superabsorbent polymer of sodium polyacrylate was studied, with emphasis on water management, i.e., absorption, retention and desorption in the soil. The polymer was applied in plots with a sandy soil near Grandola (southern Portugal). Characterization of the most relevant physical and chemical properties of the polymer was made, namely, its specific gravity, particle diameter, capacity of water absorption and desorption. In the plots with and without the polymer, soil moisture was continuously monitored, and grassland biomass samples were collected and weighed. The results reflected the effective role of the polymer both in the improvement of the water regime in the soil and in the substantial increment of grassland productivity.

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.

Influence of CaO-based expansive agent,superabsorbent polymers and curing temperature on pore structure evolution of early-age cement paste

Cracks easily generate in concrete at early age owing to the shrinkage deformation.CaO-based expansion agent(CEA)and superabsorbent polymers(SAP)have been extensively used for the mitigation of concrete shrinkage.The macroscopic properties of concrete are highly determined by the microstructure.In this study,the influence of CEA and SAP addition on the pore structure evolution of cement paste under different curing temperatures was evaluated via low-field nuclear magnetic resonance spectroscopy.Test results indicated that,in cement paste,a higher CEA content led to a higher porosity and a larger most probable pore diameter(MPPD).Meanwhile,SAP addition increased the porosity and MPPD of CEA cement paste at early age but decreased them after 7 d,and a higher SAP content always brought a higher porosity and MPPD.Furthermore,the addition of SAP led to a lower porosity and MPPD of CEA cement paste than that of plain cement paste after 14 d.Moreover,the porosity and MPPD of CEA cement paste decreased first and subsequently increased as the curing temperature raised.

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%.

Factors Influencing Strength of Super Absorbent Polymer(SAP)Concrete

Super absorbent polymers (SAPs) are gradually being applied in concrete production as internal curing agents. SAP can effectively reduce early age autogenous shrinkage of concrete, alleviate the hazards caused by concrete cracking and improve its freeze–thaw resistance. However, the relationships between SAP dosage, SAP particle size and the water–cement ratio of concrete have certain influences on the evolution of the compressive strength of SAP-incorporated concrete. In this study, experiments were conducted to investigate the relationships between the water–cement ratio of concrete, the SAP dosage and SAP particle size. The significant factors influencing concrete strength are determined and equations are proposed for predicting the strength of SAP-incorporated concrete at 3, 7 and 28 days. The findings from this study, such as the SAP dosage should not be larger than 0.2%, are expected to form a theoretical basis for the rational use of SAP as an additive to concrete. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

Study on the Expansion of a Cement-Based System Containing Sap Polymer and Supplementary Cementing Materials

In this paper, the addition of admixed superabsorbent polymer (SAP) improved the microstructure and durability-related properties in a cement-based system with supplementary materials. This is an important issue in real construction projects when good durability properties are required. This study investigates the effect of SAP on the systems using cement replacement by fly ash and silica fume considering the strength properties and durability properties of paste under sulfate attack of cement-based system. The replacement considered in the study was of 10% silica fume and 20% fly ash in each case, the dosage of SAP was 0.25% of the total amount of cementitious material. The results showed that the addition of SAP in the cement-based system improved the compressive strength and reduced expansion to sulfate attack. Scanning electron micrographs showed that utilization of fly ash with silica fume and silica fume with SAP resulted in a much denser microstructure, thereby, leading to an increase in compressive strength and lower expansion under sulfate attack.

Assessment of Super Absorbent Polymer (SAP) on Plant Available Water (PAW) in Dry Lands

One of the ways of overcoming the cost of irrigation is through in-situ water harvesting at the plant roots. Super absorbent polymer (SAP) can facilitate water harvesting at the plant roots. This study attempted to assess the effect of SAP on plant available water (PAW) of different soils. In this study, SAP was sequentially added at the rate of 0.2%, 0.3% and 0.5% of the soil weight and its impact assessed in clay, sandy clay and sandy loam soils. The moisture retention characteristics of the original and SAP treated soils were studied using soil water retention curves (SWRC) and results modelled using Gardner model. PAW was estimated from SWRC as the difference between moisture content at 1.5 and 3 bar in all soils. The difference in PAW between original and treated soils was assessed at 5% level of significance. The WRC of all the samples was adequately found to be described by the Gardner model (Coefficient of determination R2 ≥ 98% and residual standard error (RSE) ≤ 0.04). SWRC changed with increase in SAP percentage in clay, sandy clay and sandy loam soils. Clay had a higher change in water retention then sandy clay and lastly sandy loam. Plant available water content (PAW) in all soils increased. In clay soil it increased with increase in SAP from 0.3291 at zero SAP to 0.6223 at 0.5% SAP. Sandy clay soil increased in PAW from 0.2721 at zero SAP to 0.5335 at 0.5% SAP and Sandy loam soils from 0.1691 at zero SAP to 0.3461 at 0.5% SAP. Hence, from the study SAP can be used to conserve irrigation water in the plant roots and therefore reducing the cost since PAW has been increased.

纳米二氧化硅负载丙烯酰胺型SAP内养护性能研究

设计制备了纳米二氧化硅(NS)负载丙烯酰胺型高吸水树脂(SAP),探究了不同NS负载量的SAP对砂浆自收缩、干燥收缩和力学性能的影响。结果表明,丙烯酰胺型SAP能够完全消除砂浆自收缩,而随着NS负载量增加,负载型SAP对自收缩的抑制作用降低,但仍保持在80%以上。SAP及额外水的引入增加了砂浆的干燥收缩,但随着NS负载量增加,负载型SAP对缓解干燥收缩有积极作用。SAP及额外水的引入降低了砂浆的力学性能,但随着NS负载量增加,负载型SAP显著改善了砂浆的力学性能。其中,负载50%(相对于丙烯酰胺的质量分数)NS的SAP对砂浆力学性能影响最小,试样在28 d龄期的抗压强度与抗折强度仅损失5.6%与2.2%。热重(TG)以及背散射扫描电子显微镜(BSE)结果表明,随着NS负载量增加,负载型SAP内养护试样的水化程度显著提高,微观结构明显改善。

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.

Fabric changes induced by super-absorbent polymer on cementelime stabilized excavated clayey soil

This paper studies the microstructure variation induced by super-absorbent polymer(SAP)to understand the mechanism of macroscopic strength improvement of stabilized soil.The fabric changes of cement elime stabilized soil were analyzed with respect to the variation of SAP content,water content,lime content and curing time,using mercury intrusion porosimetry(MIP)tests.It can be observed that the delimitation pore diameter between inter-and intra-aggregate pores was 0.2 mm for the studied soil,determined through the intrusion/extrusion cycles.Experimental results showed that fabric in both inter-and intra-aggregate pores varied significantly with SAP content,lime content,water content and curing time.Two main changes in fabric due to SAP are identified as:(1)an increase in intra-aggregate pores(<0.2 mm)due to the closer soilecementelime cluster space at higher SAP content;and(2)a decrease in inter-aggregate pores represented by a reduction in small-pores(0.2e2 mm)due to the lower pore volume of soil mixture after water absorption by SAP,and a slight increase in large-pores(>2 mm)due to the shrinkage of SAP particle during the freezeedry process of MIP test.Accordingly,the strength gain due to SAP for cementelime stabilized soil was mainly due to a denser fabric with less interaggregate pores.The cementitious products gradually developed over time,leading to an increase in intra-aggregate pores with an increasing proportion of micro-pores(0.006e0.2 mm).Meanwhile,the inter-aggregate pores were filled by cementitious products,resulting in a decrease in total void ratio.Hence,the strength development over time is attributable to the enhancement of cementation bonding and the refinement of fabric due to the increasing cementitious compounds.

Effects of different concentrations of super-absorbent polymers on soil structure and hydro-physical properties following continuous wetting and drying cycles

Super-absorbent polymers(SAPs)are widely used chemical water-saving materials,which play an active role in the accumulation of soil water and the improvement of soil structure.Little is known about their performance with repeated usage or about factors influencing their efficiency under alternate wetting and drying cycles.In this study,various concentrations of SAP(0,0.1,0.2 and 0.3%)in soil following three continuous wetting and drying cycles(T1,T2 and T3),were studied to determine effects on soil structure stability and hydro-physical properties.The results indicated that the SAP improved soil water supply capacity under conditions of mild drought(T2)and sufficient irrigation(T3)at concentrations of 0.2 and 0.3%,but a reduction was observed under severe drought conditions(T1),which was negatively correlated with the SAP concentration.The physical adsorption of the SAP by soil and the chemical connection between the SAP and soil mineral colloids as Si-O-Si bonds,-OH bonds and different crystalline silica were the important factors that directly lead to the reduction of water retention capacities of the SAP with alternating wet and dry conditions.Compared with the control,the soil liquid phase ratios of the SAP treatments were increased by8.8-202.7%in the T1 and T2 cycles,which would have led to a decrease in the soil air phase ratios.After repeated wetting and drying cycles,the SAP treatments increased the amount of>0.25 mm soil aggregates and the contents of water-stable macro-aggregate(R_(0.25)),and decreased the amount of<0.053 mm soil aggregates,especially with higher concentrations of the SAP.Increases in mean weight diameter(MWD)and geometric mean diameter(GMD),and declines in fractal dimension(D)and unstable aggregates index(E_(LT))were all observed with the SAP treatments,which indicated an improvement in soil stability and structure.It was concluded that the distribution and stability of soil aggregates and soil water supply capacity was closely related to SAP concentration,soil moisture condition and the interaction between the SAP and soil particles.

Influence of Suspension Parameters on Water Absorbency of Starch-g-poly( sodium acrylate) Synthesized by Inverse Suspension Polymerization

Superabsorbents starch grafted sodium polyacrylate was prepared by inverse suspension polymerization, using toluene as the continuous phase, potassium persulfate as the initiator. The effect of suspension parameters, such as volume ratio of continuous phase and dispersed phase, type and dosage of suspending agents, on water absorbency of the starch grafted polymer was studied. Different starch derivatives were also investigated. Superabsorbents made of cationic starch has higher water absorbency than that made of native corn starch.

Influence of Reaction Parameters on Water Absorbency of Starch Grafted Superabsorbents

Superabsorbents starch grafted sodium polyacrylate was synthesized by inverse suspension polymerization, using toluene as the continuous phase, potassium persulfate as the initiator. The effect of reaction parameters, such as starch pretreatment temperature, neutralization degree of monomer, reaction time and temperature, concentration of initiator, molar ratio of monomer and starch, on water absorbency of the starch grafted polymer was studied. The effects of the last two parameters were investigated by uniform design method, and the prediction equation was obtained.

Post-treatments of Super Absorbent Polymer

Properties of high absorbency and modulus (gel strength) were both needed in applications of superabsorbent polymer (SAP). Generally, the absorption characteristic and gel strength reach a crossover point for a given system. Beyond this point, a given property will show improvement at the expense of another property. To synthesize SAP with properties superior to this optimum value, further modification in the process becomes essential. In our post-treatment modification of superabsorbent polymer, neither the variety of the crosslinkers, nor their amount was found the effective factors to the polymer performance, but the liquor ratio of the treating liquid to polymer. The combination of the chemical treating and heat-treating method was also explored. But this didn’t put any positive effect on SAP’s properties.

SAP和聚丙烯纤维双掺对混凝土抗压强度及抗渗性能的影响

隧道等地下工程混凝土主体结构渗漏为常见质量问题,严重影响结构的安全、正常使用功能及耐久性,因此混凝土的抗渗性能成为研究焦点。采用双掺SAP和聚丙烯纤维提高混凝土的抗渗性能,在混凝土中分别掺入质量比为胶凝材料0.1%,0.3%,0.5%的SAP,并同时分别加入1,2,3kg/m3的聚丙烯纤维,进行抗压与抗渗试验。结果表明:单掺0.1%~0.3%SAP时几乎不影响混凝土的抗压强度,但掺量为0.5%时,抗压强度会显著降低;双掺0.1%SAP和0~2kg/m3聚丙烯纤维可略微提升混凝土抗压强度,并且显著改善其抗渗性能;经对比,掺入0.1%~0.3%SAP和0~2kg/m3聚丙烯纤维时,可保证混凝土的抗压强度,提高抗渗性能,有效降低混凝土的渗水风险。

含SAP水泥基材料动态力学性能演变规律研究

关于高应变速率下含高吸水树脂(SAP)水泥基材料力学行为的研究较少,本文通过压汞法和图像法研究了含SAP水泥基材料的总孔隙率和宏观孔(>100μm)孔隙率;分析了SAP粒径和补偿水对改性材料准静态(10~(-5)s^(-1))和动态(60~110 s^(-1))力学性能的影响;基于裂缝扩展行为的研究,解析了高应变速率下水泥基材料的破坏行为。结果表明:添加补偿水和增大SAP粒径均会提升材料的宏观孔孔隙率和总孔隙率,从而降低准静态和动态压缩作用下试样的抗压强度和弹性模量;添加补偿水和增大SAP粒径还会提高水泥基材料的抗压强度动态增加因子和弹性模量动态增加因子,这是由于总孔隙率和宏观孔孔隙率的增加会引起裂缝扩展路径的改变、破碎程度的增加以及应变响应的延迟。