Addition Of Superabsorbent Polymer Research Articles

The effect of superabsorbent polymer on various scale of pore structure in ultra-high performance concrete

The addition of superabsorbent polymer (SAP) mainly has two opposite effects on the pore structure of ultra-high performance concrete (UHPC): the densification of microstructure due to internal curing (IC) and the increase of large voids by swollen SAP particles. To further elucidate these effects on various properties of UHPC, the pore structure of internally cured UHPC is studied in a wide range of 3 nm–10 mm (in diameter), by two methods of micro X-ray computed tomography (μ-CT) and mercury intrusion porosimetry (MIP). Owing to the different measurable pore scale, each method provides different total porosity and pore size distribution. The SAP voids significantly increase the porosity in the size range of 267 µm–2.7 mm, whereas IC makes the pore structure finer within 3–100 nm. In particular, the microstructural change due to the IC has a more decisive influence on the compressive strength than larger SAP voids. In addition, it is discovered that the positive effect of heat-treatment (HT) for UHPC is diminished due to the applied IC. The IC and HT have to share limited amounts of raw materials and space necessary to promote the hydration reaction. However, the IC consumes parts of them before the HT does, thereby limits conventional positive effect of the HT.

Influence of superabsorbent polymer on the splitting tensile strength and fracture energy of high-performance concrete

Superabsorbent polymers (SAP) addition as an internal curing (IC) agent in concrete is an approach being adopted for the mitigation of autogenous shrinkage. Micro-voids created by SAP are arguably believed to be detrimental to the mechanical properties especially the fracture tendencies of the concrete. This paper presents the report of an experimental study of SAP’s influence on the splitting tensile strength and fracture energy of low water/binder (W/B) high-performance concrete (HPC). Reference HPC mixtures (M1F, M1S, M2 and M3) designed for a 28-day minimum cube compressive strength of 70 N/mm2 (MPa) were examined for the effect of SAP grain size, content and binder type on the above stated properties. Wedge splitting test was carried out on 100 mm cube specimen of HPC containing varied SAP contents (0.2, 0.3 and 0.4 by weight of binder (bwob)) and SAP sizes, cured by water immersion for 28, 56 and 90 days respectively. The results obtained was plotted as splitting force (Fsp in kN) against the crack mouth opening displacement (CMOD in mm) for computing the work of fracture (Wf), which is the area under the Fsp CMOD curve. The study concludes that the splitting tensile strength and fracture energy of the HPCs are not directly affected by SAP addition (i.e. neither grain size nor content).

Combination of polypropylene fibre and superabsorbent polymer to improve physical properties of cement mortar

Polypropylene (PP) fibres are commonly used to restrict early shrinkage and control micro-crack propagation in mortars. However, increased porosity along with reduction in mechanical properties due to PP fibre addition is a concern. The study explores application of superabsorbent polymers (SAPs) to improve mechanical properties and permeability of PP fibre-reinforced mortar. The effect of SAP addition on fresh and hardened properties of fibre-reinforced mortar including flow, mechanical strength, elastic modulus and permeability are investigated. Experimental results show that a combination of SAP and PP fibre offers about 20% improvement in compressive strength. SAP addition increases the resistance of mortar to water penetration by up to 60%, whereas water absorption and coefficient of sorptivity is reduced by up to 46% and 66%, respectively, compared to the control. Improvement in permeability is linked to increased hydration due to SAP addition and blocking of voids by swelled SAP particles upon contact with incoming moisture. In a nutshell, a combination of SAP and PP fibre offers improvement in mechanical properties and permeability of cementitous composite, which is crucial to the serviceability and longer service life of civil infrastructure.

Superabsorbent Polymer Properties and Concentration Effects on Water Retention under Drying Conditions

Superabsorbent polymer (SAP) efficiency in water absorption and release depends on soil properties and SAP type and concentration. Our objective was to examine the effects of soil texture, SAP concentration and properties on water absorption and release from soil–SAP mixtures during 10 h of drying. Four SAP types, five SAP concentrations, and five soils were used. Initial water quantity absorbed by SAPs (53–171 g g⁻¹ of SAP) was more than two orders of magnitude greater than that absorbed by soils (0.35–0.53 g g⁻¹ of soil). Water absorption by soil–SAP mixtures (i) significantly improved water holding capacity relative to the soil, and (ii) increased with an increase in SAP concentration and soil clay content. The ability of soil–SAP mixtures to retain water after 5 h of drying relative to the initial water content was greater than that of the soils alone, especially in coarse-textured soils. After 5 h of drying, the specific amount of water retained by a unit weight of SAP in the soil–SAP mixture was higher than that at 0 h. This observation suggests a continued absorption of water by SAPs from soils during the first 5 h of drying. The fraction of water loss from SAP with large-size beads (BJ-2101M) was smallest in all the mixtures among the four SAPs after 10 h drying. Our results showed that addition of SAPs to soils not only decreases water loss to evaporation from soils but also from the SAPs, especially for a SAP with large size beads.

An investigation into the influence of superabsorbent polymers on the properties of glass powder modified cement pastes

This study examines superabsorbent polymer (SAP) absorption, mechanical strength, hydration, and electrical resistivity of glass powder modified cement pastes. The absorption of SAP was monitored using optical microscopy and shown to be higher when glass powders were used. Addition of SAP was found to improve hydration due to internal curing. The cement pastes with SAP exhibited a decreased compressive strength due to macrovoid formation. The glass powder modified cement pastes experienced a large reduction in electrical resistivity as a result of SAP addition; increased pore connectivity in these cement pastes is suggested as a possible cause of the reduction in electrical resistivity.

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.

Use of superabsorbent polymers (SAP) as concrete additive

Superabsorbent polymers (SAP) are new, very promising multipurpose chemical admixtures for concrete. They make available a number of new possibilities with respect to the control of free water in the mixture. In turn they contribute to the control of the rheological properties of fresh concrete and to the mitigation of autogenous and plastic shrinkage through internal curing. Furthermore, pore systems built up as a result of SAP addition seem to remain stable regardless of the consistency of the concrete, the addition of superplasticizers, or the method of placement and compacting. Thus, SAP can be used as an alternative to air-entrainment agents. This article presents these and other potential practical applications of SAP in concrete construction.

Determination of time zero in high strength concrete containing superabsorbent polymer and nano-silica

The autogenous shrinkage is a phenomenon that occurs due to the appearance of tensile stresses in capillary pores. Inherent in the hydration process, not depending on external interference. In high strength concrete, autogenous shrinkage is most pronounced, due to the refinement of microstructure, the high cement content, presence of mineral addictions and low water/cement ratio, which interfere in the transport of water curing. In this context, Superabsorbent polymers (SAP) stand out for their ability to reduce or eliminate the autogenous shrinkage, because they absorb large amounts of water, which is subsequently released into the matrix, avoiding self-desiccation and the onset of tensile stresses (internal curing). However, studies show that SAP can reduce the mechanical strength, which can be compensated by addiction of Nano-silica (NS). In this paper, the effect of these additions in Time Zero (T0) was evaluated. T0 determines the time at which the material starts to behave as a solid, with the development of a rigid mineral skeleton to oppose the volumetric variations that occurs in the paste, which can lead to cracking, compromising esthetics, durability, and structures safety. The ultrasonic pulse velocity test performed the T0, which measures the velocity of propagation of an ultrasonic wave through the material and is taken as the time when a sudden change occurs at this velocity. Nine blends were made containing SAP and NS, where it was found that SAP addition increases the T0 (up to 11%), while NS decrease its value (in 55%).

Effects of SAP on the properties and pore structure of high performance cement-based materials

Water-to-binder ratio (w/b) directly affects the pore structure and performance of concrete, and drying conditions enhance the influence of water-to-binder ratio. Superabsorbent polymer (SAP) is effective to adjust the water in the concrete. In this paper, the effect of SAP and extra water on drying shrinkage, pore structure and the permeability of high performance cement-based material with w/b from 0.18 to 0.24 were studied to reveal the adjusting role of SAP for the influence of water-binder ratio at a 60% of relative humidity (RH). The permeability was determined through the vacuum saturation method, the diffusion of steady-state Cl− ion and carbonation testing. The structure of harden mortar and SAP voids were evaluated by mercury intrusion porosimetry (MIP) and backscatter electronic microscopy (BSEM). At the same effective w/b, SAP reduces the strength, and raises the drying shrinkage and permeability. However, the effect of SAP on the above properties is exactly opposite when the same total w/b is used. The greater the SAP particle size is, the more obvious those favorable effects are. SAP can weaken the effect of total w/b. The addition of SAP also results in the formation of the hydration diffusion layer in SAP void and the refinement of pore structures.

Addition of Super Absorbent Polymer for Upgrading of Cement Quality in Iraqi Oil Wells

This study focuses on the use of an optimum amount of Sodium Polyacrylate (SP) for designing cement slurry with the high performance of rheological properties and displacement efficiency. A laboratory study has been carried out on the cement slurry which prepared with SP as superabsorbent polymer. SP has been providing an internal water source that helps in the hydration process, and curing and ultimately increases the cement strength. Also improves the cement performance by improving the cement stability. Several batches were prepared to determine the proper amount of SP to add it in the cement slurry. Also, we studied its effect on cement density, amount of free water in order to observe the rheological properties, and thickening time. Results indicate that the designed cement rheological properties are directly influenced by the shear rate and shear stress on the mix and pump of the cement with the increase of the SP concentration for the rheological improvement. Laboratory data are presented to highlight Polyacrylate’s positive effect on compressive strength, fluid loss control, and free water. 
 This is an open access article under the CC BY-NC license https://creativecommons.org/licenses/by-nc/4.0/

Combined application of cyanobacteria with soil fixing chemicals for rapid induction of biological soil crust formation

ABSTRACTCombined applications of cyanobacteria with soil fixing chemicals were investigated to generate artificially induced biological soil crust (BSC). Polyvinyl alcohol (PVA) and Tacki-Spray (TKS7) chemicals composed of bio-polysaccharides and tackifiers were examined under laboratory conditions. Following singular applications of chemicals, the mean weight diameter values of soil treated with TKS7 were 1.4–2.5 times higher than those of soil treated with PVA and thus TKS7 was selected for further tests for application with cyanobacteria (Nostoc Vaucher ex Bornet & Flahault, Phormidium Kützing ex Gomont, and Scytonema arcangeli Bornet ex Flahault). Combined application of cyanobacteria and different concentrations of TKS7 enhanced soil aggregate stability, resulting in mean weight diameter values of 0.58–0.69 mm and was comparable to TKS7 singular application (0.18–0.40 mm). Surface hardness values were also highly improved by the combined application of cyanobacteria with TKS7 (4.5 MPa) compared to singular treatment of cyanobacteria (2.3 MPa). In addition, superabsorbent polymer (SAP) was applied as a water-holding material and nutrient supplement in soil. The SAP promoted cyanobacterial cell growth under dry conditions. Chlorophyll a content of soil was improved by the addition of SAP (CST1: 2.93 µg g−1) compared to singular treatment of cyanobacteria (C: 2.25 µg g−1). These results suggest that combined application of cyanobacteria with TKS7 and SAP can induce BSC formation faster than singular application of cyanobacteria. The novel method presented herein can be applied to restoration of degraded soils in arid and semiarid areas.

Superabsorbent Polymers as a Means of Improving Frost Resistance of Concrete

Abstract Superabsorbent polymer (SAP) was introduced in cementitious materials about 15 years ago. Since then, several studies on the frost resistance of concrete with SAP have been published. However, an up-to-date review across the different studies is missing. This paper presented a literature review on how SAP influences concrete frost resistance. Moreover, it also presented a larger experimental study on the topic. The conclusions that were drawn from the experimental study were in line with the extract of the pool of results from the literature, first of all that SAP addition can improve frost resistance of concrete. The improvement was attributed to voids created by SAP. As was clearly demonstrated in the paper, it was crucial to document the void structure of the hardened concrete. Other factors than SAP could lead to void formation. For example, residue of surfactant on SAP particles, originating from the production of suspension polymerized SAP, can have an air entraining effect in concrete. Therefore, assuming that SAP generated voids are the only voids may lead to erroneous conclusions. When SAP is used, it is, in principle, possible to produce concrete with a pre-defined void structure as regards total void volume and void size. However, the optimum SAP void structure in relation to frost resistance is not known, and as long as the target is not clear, it is hard to use the design option of controlled void structure in a constructive way.

Internal curing by superabsorbent polymers in ultra-high performance concrete

To limit self-desiccation and autogenous shrinkage that may lead to early-age cracking of ultra-high performance concrete (UHPC), internal curing by means of superabsorbent polymers (SAP) may be employed. Cement pastes and UHPC with water-to-cement ratio below 0.25, with or without SAP, were studied. The absorption capacity of a solution-polymerized SAP was first determined on hardened cement pastes by SEM image analysis. It was observed that the SAP cavities become partially filled with portlandite during cement hydration. Isothermal calorimetry showed that water entrainment with SAP delays the main hydration peak, while after a couple of days it increases the degree of hydration in a manner similar to increasing the water-to-cement ratio. Internal curing by SAP is effective in reducing the internal relative humidity decrease and the autogenous shrinkage. Although the mechanical properties are affected by SAP addition, it is possible to reach compressive strengths of almost 150MPa at 28days.

Effect of superabsorbent polymer (SAP) on the performance of polyvinyl alcohol (PVA) fiber-reinforced strain-hardening cement composites

This paper reports the effect of superabsorbent polymer (SAP), a promising chemical admixture for multifunction cement composites, on the fresh and hardened properties of polyvinyl alcohol (PVA) fiber-reinforced strain-hardening cement composite (PVA-SHCC). Two types of PVA-SHCC mixtures were prepared and investigated to evaluate the effect of SAP introduction. The PVA fiber volume content was fixed at 2.0% and content of SAP was 1.0% by the binder mass. It was found that the SAP particles lead to the deterioration in the slump. It is also confirmed that the addition of SAP within 1% into cement composite improves the hardened properties, such as compressive, flexural and direct tensile performances, of PVA-SHCC due to internal curing in the cement matrix.

Effect of superabsorbent polymers (SAPs) on rheological properties of fresh cement-based mortars — Development of yield stress and plastic viscosity over time

Superabsorbent polymers (SAPs) are a new, promising, multipurpose chemical admixture for concrete. This article addresses the rheological behaviour of fresh, cement-based mortars modified with SAP. Two types of SAP with differing water absorption and desorption kinetics were used. Additionally, for one the grading was varied. Three reference mortars were investigated. The rheological properties of these fresh mortars were tested for 90min by continuous flow rheometry. It was found that the distinct kinetics of water uptake inherent in the SAP samples, as governed by their particular chemical structures, is the major factor that governs the rheological properties of fresh mortar. Furthermore, the grading of SAP distinctly affects the development of yield stress and plastic viscosity over time. The particular effects of specific SAP addition on the rheological characteristics of a mortar depend on the water-to-binder ratio, the dosage of superplasticizer, and the dosage of silica fume, if present.

Effect of pre-soaked superabsorbent polymer on shrinkage of high-strength concrete

Pre-soaked super-absorbent polymer (SAP) was incorporated into high-strength concrete (HSC) as an internal curing agent to study its effects on early-age shrinkage and mechanical properties. On the basis of the capillary stress based model for shrinkage prediction of concrete, together with the experimental results of cement hydration kinetics, evolution of internal temperature and humidity, development of pore structure and mechanical properties, the working mechanism of SAP was discussed. Results indicate that the addition of pre-soaked SAP significantly reduces the autogenous shrinkage as well as the early-age shrinkage of HSC under drying condition. In sealed HSC specimens, the drop of internal humidity caused by the self-desiccation effect is notably postponed by addition of pre-soaked SAP. The addition of pre-soaked SAP slightly reduces the compressive strength of HSCs and this effect is more pronounced in early-age concrete. Furthermore, an insightful comparison of the behaviours of the internal curing water introduced by the pre-soaked SAP and the additional free mixing water in concrete was made. Results indicate that the internal curing water behaves differently from the additional mixing water in influencing the cement hydration kinetics, pore structure of hardened cement pastes and the mechanical strength of concrete, due to the different spatial distribution of the two types of water in the concrete bodies. The shrinkage-reducing effect on HSC due to the addition of extra internal curing water incorporated by pre-soaked SAP is much stronger than that of the additional mixing water. Besides, the internal curing water shows much less strength-reducing effect than the additional mixing water. In virtue of the shrinkage prediction model, the working mechanism of pre-soaked SAP in reducing autogenous shrinkage of HSC is proposed on the basis of the following two aspects. The participation of internal curing water in cement hydration process leads to a total volume gain of the hardening cement pastes. Meanwhile, the release of internal curing water from the pre-soaked SAP postpones the drop of internal humidity. The synergistic effect of these two factors effectively reduces the autogenous shrinkage of HSC.

The use of superabsorbent polymers to reduce cracking of bonded mortar overlays

The use of superabsorbent polymers (SAP) was found to significantly improve cracking characteristics of normal strength bonded mortar overlays containing silica fume. Mortars were designed with two water/binder ratios and three different SAP contents and tested for relevant material properties such as tensile strength, tensile relaxation, elastic modulus and drying shrinkage. With respect to overlay cracking, SAP addition generally resulted in an improvement in all tested properties, especially with respect to increasing relaxation and reduced elastic modulus. To observe cracking in real bonded overlays, mortars were cast on a rigid substrate and their cracking behavior observed for a period of approximately 7weeks. The results indicate that SAP additions of 0.4% and 0.6% are very effective in reducing cracking in bonded mortar overlays with water/binder ratios of 0.45 and 0.55, respectively.

Design and control shrinkage behavior of high-strength self-consolidating concrete using shrinkage-reducing admixture and super-absorbent polymer

In the present study, self-consolidating concrete (SCC) with 28 days compressive strength of 110 MPa was fabricated. Its workability, hydration heat evolution, chloride penetration resistance, and mechanical properties were analyzed. To enhance its volume stability, shrinkage-reducing admixture (SRA) and super-absorbent polymer (SAP) were used, and their effect on autogenous shrinkage, drying shrinkage, and strength of the concrete were evaluated. The results indicate that high-strength SCC can be achieved using a carefully designed ternary binder system (made with cement, fly ash, and silica fume), water-reducing admixture, and low water-to-binder ratio (W/B = 0.20). Addition of SRA and SAP into the concrete significantly reduced autogenous shrinkage and slightly reduced drying shrinkage. SAP is more effective in reducing autogenous shrinkage at later age, and the effect of SRA is better than that of SAP for drying shrinkage reduction.

Influence of super absorbent polymer on soil water retention, seed germination and plant survivals for rocky slopes eco-engineering

To improve the utilization of water resources on rocky slopes eco-engineering, super absorbent polymer (SAP) with the function of water retention was applied. Super absorbent polymer in three levels, 0.15%, 0.3% and 0.45% were mixed with sandy loam soil. This study was aimed to evaluate the saturated water content, evaporation rate and water holding capability of SAP treated soils, determine seed germination rate and plant survivals in soil with SAP by absorbing and spraying experiments. The addition of SAP to the sandy loam soil resulted in a significant increase of the soil water retention compared to the controls. Also, the seed germination was significantly higher in SAP amended soil than in the soil without SAP, survival times of grass and woody were prolonged under water stress. 0.30% SAP treatment was the optimum selection for sandy loam soil improvement on steep rocky slopes. These studies indicated that SAP with good water retention properties, was very effective in enhancing water uptake and utilization of water for plants growth, and could be expected to have wide potential applications in rocky slopes eco-engineering.

Effects of super-absorbent polymer on dry matter accumulation and nutrient uptake of Pinus pinaster container seedlings

Super-absorbent polymer (SAP) is a widely studied cross-linked hydrophilic polymer used as water absorbent material. However, little information is available concerning the effects of SAPs on the growth and nutrient accumulation in forest container seedlings. The present study was conducted to quantify the effects of SAP applied with or without fertilizer on the dry matter and nutrient uptake of Pinus pinaster container seedlings. SAP addition with fertilizer increased dry matter along with increased seedling emergence time. However, no effect was found without fertilizer. Compared with fertilizer only, rapid accumulation time of nitrogen (N) and potassium (K) was 7 days longer resulting from SAP addition. The maximum daily N and K accumulations in the fertilized seedlings increased by 9.31 and 10.44 %, respectively, whereas those of the unfertilized seedlings did not differ significantly. SAP addition had little effect on phosphorous (P) uptake, except for an increase in the maximum daily P accumulation under fertilized conditions. The shoot and root of P. pinaster with SAP had 8.61 and 13.70 % higher yields, respectively, than those that received fertilizer only. Compared with fertilizer only, SAP addition with fertilizer increased the N and K contents by 7.15 and 10.04 %, respectively, whereas the P content did not differ significantly. Under fertilized conditions, N, P, and K uptake increased by 17.17, 10.13, and 20.33 %, respectively, from SAP addition. Hence, SAP could be used as a nutrient absorption enhancer (mainly N and K) in forest container seedlings, aside from being a water absorbent material.