Addition Of Superabsorbent Polymers Research Articles

Influence of superabsorbent polymers on the chloride ingress of mortar measured by chloride diffusion and a quasi-steady-state migration test

The ingress of chloride ions is a serious threat for concrete structures. Superabsorbent polymers (SAPs) are interesting additions to cementitious systems due to their property of absorbing water during mixing and releasing it at a later time to provide internal curing, thereby reducing shrinkage and promoting durability. In addition, SAPs can improve the regain in impermeability of cracks by swelling and blocking the crack and promoting autogenous healing. The current study investigates the influence of the addition of SAPs without additional mixing water to the chloride ingress in cracked mortar via diffusion and quasi-steady-state migration testing. Filtration tests showed that the charge-screening effect in a NaCl solution is more dominant than for cement filtrate solution during swelling of SAPs. After wet/dry cycling for a month, subsequent chloride diffusion tests with 2 and 6 weeks of exposure showed that the addition of SAPs improved the performance with respect to a reference mix with the same total water-to-cement ratio. A reference mix with the same effective water-to-cement ratio as the SAP mix had a comparable performance to the SAP mix. One set of chloride diffusion experiments showed that the SAP mix was the only one successfully preventing chloride ingress into the deepest zone of the crack. The superior performance of the series with SAPs was also confirmed by migration testing where cracked and healed specimens obtained a migration coefficient which was only 12 % higher than uncracked specimens.

Self‐healing characteristics of superabsorbent polymers in epoxy coating for corrosion inhibition of carbon steels

AbstractThis study evaluated the self‐healing characteristics of superabsorbent polymers (SAP) in epoxy polyamide paint systems applied using brush application. The SAP underwent preliminary characterization to determine its primary properties and was then incorporated into the epoxy primer at different percentages. The epoxy‐SAP coating systems then underwent various tests to evaluate their self‐healing capability. Excellent adhesion is obtained with the coating system composed of initial epoxy primer, epoxy‐SAP layer, final epoxy primer, and an epoxy enamel topcoat. Electrochemical impedance spectroscopy (EIS) reveals that the addition of SAP increased the charge transfer resistance and pore resistance and decreased the double layer capacitance of the coating system in a span of 5 h, confirming the self‐healing of the coating. Maximum corrosion protection for 5 h is obtained between 15 to 20 wt% SAP. Lastly, it is determined through long‐term immersion tests that the addition of SAP in the coating significantly decreases the rust formation; however, the coating starts to peel off due to the swelling of SAP after 2–3 days.

Effect of superabsorbent polymers on the interlayer bonding properties of 3D printing mortar

To investigate the impact of internal curing using superabsorbent polymers (SAPs) on the interlayer bonding properties of 3D printed mortar, this study examined the interlayer bonding properties of 3D printed mortar with different types of SAPs incorporated. The experimental results demonstrated that the addition of SAPs could enhance the interlayer bond strength of 3D printed mortar to a certain extent, with the maximum split tensile strength increased by 48.78%. The study employed the layered casting tensile method, which is simple and efficient, to assess the interlayer bond strength of the printed mortar.
 To investigate the influence of internal curing using superabsorbent polymers (SAPs) on the interlayer bond strength of 3D printed mortar, this study examined the interlayer bond strength of 3D printed mortars with different types of SAP added. The experimental results show that the addition of SAP can enhance the interlayer bond strength of 3D printed mortar to a certain extent, with a maximum splitting tensile strength increase of 48.78%. In order to evaluate the interlayer bond strength of printed mortar, this study used the layer casting tensile method, which is simple and efficient.

Influence of Superabsorbent Polymer in Self-Compacting Mortar

Self-compacting concrete (SCC) is an innovative type of concrete that does not require vibration for compaction; however, it needs attention in relation to the control of thermally generated cracks, due to the hydration heat generated mainly during the curing process in pieces with large concrete volume. In this study we investigated the addition of Superabsorbent Polymers (SAP) as internal curing elements in self-compacting mortar (SCM), as well as its thermal and mechanical characteristics, looking to obtain the optimal proportion of materials in a way that is useful as the basis of self-compacting concrete use, focusing on large volume structures. This work stands out for studying an alternative for shrinkage control, in an unconventional cementitious composite, highlighting the thermal analysis of the mixture. In the experimental program, laboratory trials were conducted using self-compacting mortar with the addition of 0%, 0.1%, and 0.2% of SAP either for CPII-E-32 and CPV-ARI and with samples undergoing both dry and submerged curing. Among the results obtained, the reduction of variation in temperature in samples with added SAP stand out, and it is possible to presume it as being a viable way of mitigating the temperature spikes in large volume concrete parts. By contrast, the compression and tensile tests indicated a reduced strength, except in the tensile trial on the CPII-E-32, which the addition of SAP resulted in an increase in strength.

Characterization and under Water Action Behaviour of a New Plaster-Based Lightened Composites for Precast.

Plaster is a construction material widely used for the production of prefabricated parts in building construction due to its high capacity for hygrothermal regulation, its good mechanical performance, and its fireproof nature, among other factors. Its historical use has been linked to ornamental elements, although more recent research is oriented towards the industrialisation of plaster composites and the design of prefabricated parts for false ceilings and interior partitions. In this work, the behaviour against water of four new plaster-based composite materials is studied, using additions of two types of super absorbent polymers (sodium polyacrylate and potassium polyacrylate) and a lightening material (vermiculite) in their manufacturing process. In addition, the transmission of water vapour through the samples was studied together with the water absorption capacity of the samples in order to check the suitability of the use of plaster-based materials exposed to these environments. The results of this study show that composites with the addition of super absorbent polymers as well as vermiculite significantly improve their water performance compared to traditional materials up to 7.3% water absorption with a minimal (13%) reduction in mechanical strength compared to current materials with similar additions. In this sense, a plaster material is obtained with wide possibilities of application in the construction sector that favours the development of sustainable and quality buildings, in line with Goal 9 for Sustainable Development included in the 2030 Agenda.

The sensitivity of Acoustic Emission (AE) for monitoring the effect of SAPs in fresh concrete

Fresh concrete is characterized by numerous processes taking place simultaneously such as settlement, hydration, early-age cracking and shrinkage. Those processes have a strong impact on the strength and durability, hence monitoring the material at an early stage is essential to ensure the required performance. Acoustic Emission (AE) is a non-destructive, highly sensitive technique that records elastic waves propagating through the medium and has proven to be adequate to monitor the complex processes taking place at an early age. In this study, the method of AE is applied on fresh concrete cubes with or without the addition of SuperAbsorbent Polymers (SAPs). SAPs are particles that have been recently used for internal curing or self-healing of cementitious materials. The water-releasing action of SAPs is accompanied by high AE activity. The purpose of this study is to investigate the possibility to control the internal curing of concrete based on real-time AE data, as well as to make projections towards the final mechanical properties while still at a young age, in order to ensure the desired concrete performance.

The Effect of Superabsorbent Polymers on Mechanical Characteristics and Cracking Susceptibility of Alkali-Activated Mortars Containing Ground Granulated Blast-Furnace Slag and Copper Slag

In an attempt to increase sustainability of construction materials, both ground granulated blast-furnace slag (GGBS) and, less popular, copper slag (CS) can be used in alkali-activated composites. However, such composites are often more susceptible to cracking, triggered by the self-desiccation processes. The addition of superabsorbent polymers (SAP) may enable internal curing of concrete and prevent excessive cracking. Thus, this paper aims to evaluate the effectiveness of SAP as an internal curing agent for alkali-activated slag mortars containing GGBS and CS. The samples were activated by sodium silicate using 6.5% Na2O by mass of precursor. The evaluation was based on the analysis of mechanical properties, autogenous shrinkage, and water absorption capacity of two types of SAPs. Depending on the type of polymer, a higher alkali concentration in SAP solutions speeds up early age reactions up to 7 days. After this period, SAP collapses and reactions follow at the same pace as the reference sample. In the presence of CS, SAP with higher absorption and smaller particles well-distributed in the mix leads to a higher extension of reactions, observed in higher values of autogenous shrinkage (AS). This results in increased compressive strength of GGBS-CS mortars, achieving values 8.8% greater than the reference sample (without SAP) at 6 months. Although its leads to higher cracking susceptibility, SAP can improve mechanical properties and promote new applications for sustainable material containing copper slag.

Effect of Superabsorbent Polymers on the Self-Healing Properties of Pre-Damaged Concrete

Cracks in concrete structures reduce bearing capacity, durability, and safety. This paper reveals the effect of superabsorbent polymers (SAP) on the self-healing property of pre-damaged concrete based on mechanical properties tests, mercury intrusion porosimetry, scanning electron microscopy, and energy dispersive spectrometer. The experimental results show that SAP reduces the mechanical properties of the SAP-modified concrete under the same W/C ratio, but a small amount of SAP can improve the later strength under the 0.35 W/C ratio. The addition of SAP increased the volume of small capillary pores (<20 μm) and large capillary pores (>100 μm) and significantly reduced the former with an increase in age. The SEM-EDS analysis indicates that the water released by SAP promotes the formation of C-S-H gel. AFt in the cracks is the main reason for self-healing, and the addition of CO2 to produce calcium carbonate is another one. Furthermore, this study finds that SAP-modified concrete has the best self-healing effect and the densest structure when the W/C ratio is 0.35 and the SAP content is 0.25%. The self-healing performance makes the SAP-modified concrete have broad application prospects.

Effect of superabsorbent polymers on mechanical strength and cracking of mortar and concrete with water to cement ratios of 0.4 and 0.5

AbstractMost studies of adding superabsorbent polymers (SAP) into concrete focus on high‐strength concrete, while this paper aims to understand the influence of SAP on “ordinary concrete” at a w/c ratio being 0.4 or 0.5. The proposed experiments include the effect of particle size, mixing methods, and dosages on the restrained shrinkage and mechanical properties of mortar and concrete. Mortar with varying dosages of SAP (0.1, 0.2, and 0.3 wt.%) and two types of SAP (type‐a of 30–60 mesh and type‐d of 300–400 mesh) was studied to evaluate the effect of SAP on mortar's cracking and strength. Two mixing processes of SAP (dry and pre‐wetted) were used to examine the effect of SAP on the mortar's shrinkage and mechanical properties. Furthermore, concrete specimens with a w/c ratio of 0.5 were prepared to investigate the cracking performance of concrete using the restrained squared concentric ring test method, a new approach which can predict the cracks location and pattern to evaluate the restrained shrinkage of concrete. The result revealed that the addition of SAP in a prewetted state decreased the mechanical properties at early curing age. The addition of 0.3 wt.% SAP was found to have mitigated the restrained shrinkage while prolonging the time to cracking of cementitious composites. The major finding is that adding SAP to ordinary concrete reduces shrinkage and improves mechanical strength, which should be further looked into and explored in its application in engineering work.

Evaluation of mix design strategies to optimize flow and strength of mortar internally cured with superabsorbent polymers

A straightforward mix design method was developed for proportioning mortars containing superabsorbent polymers (SAPs). When modified by introduction of a typical amount of SAP (i.e., 0.2% by weight of cement), the 0.42 w/c ordinary Portland cement (OPC) mortars required addition of extra water and/or high-range water reducing admixture (HRWRA) to achieve a minimum target percent flow in mortar flow table tests. At high w/c (≥0.49), SAP accelerated compressive and flexural strength development. In all mortars tested, the addition of SAP either preserved or increased compressive and flexural strength values relative to SAP-free mortar with the same w/c.

Rheological characterization of cemented paste backfills containing superabsorbent polymers (SAPs)

The addition of superabsorbent polymers (SAP) to cemented paste backfill (CPB) made from tailings slurries may offer a good alternative to the dewatering components of the conventional CPB production owing to their high-water absorption and retention capacities. Therefore, an experimental program was implemented to characterize the rheological behavior of CPB incorporating an SAP. Two types of binder comprising a general use Portland cement (GU) and a blended binder (GUSL) consisting of 80% ground granulated blast furnace slag (GGBFS) and 20% GU were used. Two different binder proportions, Bw (=100 × Mbinder/Mdry-tailings) of 4.5 and 7% were tested. An SAP dosage (ratio of the dry mass of SAP to the volume of the tailings slurry) of 30 and 34 kg/m3 was assessed in this study. Results showed that the SAP addition distinctly reduced the yield stress (τ0) and the infinite shear viscosity (μ∝) and increased the small cone (H = 150 mm) slump height (s) of such mixtures over time. Moreover, The SAP-thickened tailings CPB (SAP-TT CPB) showed a severe shear-thinning behavior marked by a negative flow index (n < 0) and moderate to extremely low yield stress (τ0 in the range 21–78 Pa), while the corresponding reference CPB without SAP added (Ref) exhibited a normal shear-thinning behavior with moderate to slightly high yield stress (τ0 in the range 76–206 Pa).

Innovative SuperAbsorbent Polymers (iSAPs) to construct crack-free reinforced concrete walls: An in-field large-scale testing campaign

Although a lot of research has been performed with the use of Superabsorbent polymers (SAPs) in cementitious materials, there is still a lack of studies describing the use of SAPs in large-scale concrete structures under realistic conditions. This paper presents results of an in-field testing campaign where SAPs were used in a large-scale demonstrator. Commercial SAPs and in-house-developed SAPs (constituted of an alkali-stable and alkali-unstable crosslinker, for a tailored swelling behavior) were used. Five reinforced-concrete walls (14 m × 2.75 m × 0.80 m) were built and monitored with regards to shrinkage-cracking with demountable strain gauges and optical-fiber sensors. A laboratory campaign was performed simultaneously to characterize the concrete mixtures. The addition of SAPs promoted a reduction of up to 75% of shrinkage strains in the first 7 days. No cracks have developed in the SAP walls up to 5 months, while the reference wall cracked 5 days after casting.

Mechanism and erosion resistance of internally cured concrete including super absorbent polymers against coupled effects of acid rain and fatigue load

This study explored a novel method for inhibiting the effects of acid rain erosion and fatigue loading in concrete by incorporating super absorbent polymers (SAP). Three different dosages and four particle sizes of SAP were considered to evaluate the erosion resistance to a simulated acid rain solution (pH = 3.0) for eight test cycles. The mass loss, compressive strength, flexural strength, and erosion depth as well as the results of X-ray diffraction (XRD) and the mercury intrusion porosimetry (MIP) testing were employed to explore the erosion behavior and mechanism of the internally cured concrete with SAPs. The results show that the coupled effects of acid rain and fatigue loading has a remarkable influence on the performance degradation of concrete. The erosion of concrete by acid rain was delayed and weakened with the addition of SAP, particularly when 0.10% SAP was added with a particle size of 100–120 mesh. Moreover, the SAP promoted hydration, which lessened the deterioration caused by pore deformation and improved the internal pore structure.

Influences of cation valence on water absorbency of crosslinked carboxymethyl cellulose

Anti-drought is a global challenge. The addition of superabsorbent polymers (SAPs) in soil can lower down the water percolation and evaporation. However, the salt-tolerance and repeating water absorbency (RWA) of prepared SAPs have not satisfied the requirements for implementation. This research investigated the influence of cation valence (Na+, Ca2+ and Al3+) on the structural variations of a crosslinked carboxymethyl cellulose (CCMC) using carboxymethyl cellulose (CMC) cross linked by epichlorohydrin (ECH). The results showed that higher addition of NaOH resulted in higher water absorbency (WA) due to the existence of more carboxyl group. The prepared CCMC sample with 5% CMC and 3% NaOH (CCMC53) was a qualified SAP with WA of 969.0 g/g in deionized water. The salt resistance and the hydrophilicity of sample CCMC53 decreased with the increase of cation valence in the solution. The introduction of Na+ resulted in the replacement of H+ from carboxyl group in sample CCMC53-Na. The coordination of carboxyl group and Ca2+ was bidentate chelating and tridentate bridging for carboxyl group and Al3+. The introduction polyvalent cations benefited the stabilization of carboxyl group, however, retarded the swelling ability of sample CCMC53 and hence resulted in lower WACS. The RWA of sample CCMC53 in deionized water and salt solution dropped the most in the first absorption cycle and then reached constant after a few more cycles. It was necessary to control the first swelling degree of SAP in order to keep the RWA at a higher level.

The influence of water-to-cement ratio and superabsorbent polymers (SAPs) on solid-like behaviors of fresh cement pastes

Solid-like behaviors of fresh cement pastes are gaining increased attention with the emergence of 3D concrete printing. It is known that the fresh cement paste exhibits a “two-step yielding” in the solid regime. This study aims to achieve a more comprehensive understanding of “two-step yielding” behavior of the cement pastes with different water-to-cement ratios and with the addition of SAPs. The influence of water-to-cement ratio and SAPs on the solid-like behaviors of cement pastes were investigated by the constant shear rate test using a rotational rheometer. The results demonstrate that changes in the solid-like properties of the fresh cement pastes, such as static yield stress, critical strain, elastic limit, and tangent modulus, do not necessarily follow the same pattern since different aspects of solid-like properties can be attributed to the different particle interactions among cement systems. The results further emphasize that, for a better understanding of the influence of the mixture design parameter on the shape stability of 3D printed concrete, it is necessary to determine its impact on all aspects of solid-like behaviors, from pure elasticity to elasto-viscoplasticity, other than the static yield stress alone.

Early-age and long-term strength development of high-performance concrete with SAP

Internal curing of high-performance concrete (HPC) by the addition of Superabsorbent Polymers (SAP) has been proven to be effective in mitigating autogenous shrinkage. The issues of concern in research, however, is the extent to which strength development is impacted by the voids created by SAP as cement hydrates with age. In this study, the influence of SAP content, size, binder type, water/binder ratio (W/B) and curing age on the early-age and long–term strength development of a low W/B HPC was examined. HPC mixtures designed for a minimum 28-day target cube strength of 70 MPa (i.e. C55/67 – C100/115) were studied with 25 g/g extra water provided for SAP absorption. Mortar (50 mm) and concrete (100 mm) cubes were cast and cured in water for different hydration periods. The results reveal that the compressive strength of the HPC mixtures decreased slightly (both for the early-age and long-term) as SAP content increased. Statistical examination of the results further revealed that W/B and SAP contents significantly influenced the strength development while a simulation of the SAP’s water absorption into Powers’ Model show compatibility for prediction of strength development trends in HPC with SAP.

Early age shrinkage phenomena of 3D printed cementitious materials with superabsorbent polymers

3D printing of cementitious materials is a novel construction method, capable of producing complex geometries without the use of expensive formwork. However, due to the lack of molding, additional shrinkage will be induced and the risk of crack formation will increase. As cracks introduce ingress paths for chemical substances, it will harm the durability of the printed element. One potential way to tackle this disadvantage is by including superabsorbent polymers (SAPs) in the cementitious material. As these polymers are able to absorb part of the mixing water and to release it during hardening, they induce internal curing and can mitigate self-desiccation, plastic and autogenous shrinkage. Additionally, as drying shrinkage and the related early-age crack formation are major issues in printed structures, the mitigating effect of the SAPs on the latter is also investigated. Three different SAPs (bulk-polymerized monovalent salt polyacrylates with an irregular shape and different size) were used in this research to fabricate printed elements and their influence on the durability and the mechanical properties was correlated with the microstructural changes. First results showed that in general, the addition of superabsorbent polymers mitigates shrinkage in printed materials up to 200%. Inclusion of SAPs also reduced the nanoporosity in the pore size range of 100 nm–500 nm and increase the amount of voids with a diameter above 700 nm, resulting in less microcracks and a decreased amount of preferential ingress paths for chemical substances. On the other hand, the total air content increases with the addition of SAPs, proportional to the amount of SAPs and additional water added, due to the formation of macropores. The addition of SAPs did not seem to have a pronounced influence on the mechanical properties of the printed specimens with a reference water-to-cement ratio of 0.37.

The Influence of Superabsorbent Polymers and Nanosilica on the Hydration Process and Microstructure of Cementitious Mixtures

Superabsorbent polymers (SAPs) are known to mitigate the development of autogenous shrinkage in cementitious mixtures with a low water-to-cement ratio. Moreover, the addition of SAPs promotes the self-healing ability of cracks. A drawback of using SAPs lies in the formation of macropores when the polymers release their absorbed water, leading to a reduction of the mechanical properties. Therefore, a supplementary material was introduced together with SAPs, being nanosilica, in order to obtain an identical compressive strength with respect to the reference material without additives. The exact cause of the similar compressive behaviour lies in the modification of the hydration process and subsequent microstructural development by both SAPs and nanosilica. Within the present study, the effect of SAPs and nanosilica on the hydration progress and the hardened properties is assessed. By means of isothermal calorimetry, the hydration kinetics were monitored. Subsequently, the quantity of hydration products formed was determined by thermogravimetric analysis and scanning electron microscopy, revealing an increased amount of hydrates for both SAP and nanosilica blends. An assessment of the pore size distribution was made using mercury intrusion porosimetry and demonstrated the increased porosity for SAP mixtures. A correlation between microstructure and the compressive strength displayed its influence on the mechanical behaviour.

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.

Influence of Barchip fiber on early-age autogenous shrinkage of high-strength concrete internally cured with super absorbent polymers

High-strength concrete (HSC) usually suffers the high early-age autogenous shrinkage owing to the low water-binder (w/b) ratio. Barchip fiber and super absorbent polymers (SAPs) have been utilized to reduce the autogenous shrinkage of HSC at early age. The relationship between autogenous shrinkage and ultrasonic velocity of internally cured high-strength concrete (ICC) reinforced with Barchip fiber was studied utilizing the non-contact shrinkage test. Experimental study and corresponding analysis demonstrated that: (1) the autogenous shrinkage and ultrasonic velocity of concrete decreased with the volume percentage of Barchip fiber increasing, and decreased with the addition of SAPs; (2) models for predicting early-age autogenous shrinkage strain and ultrasonic velocity of ICC reinforced with Barchip fiber considering the fiber volume percentage and age were proposed; (3) the model of early-age autogenous shrinkage strain based on the results of ultrasonic velocity at different ages and at 28 d with no addition of Barchip fiber was proposed; (4) the prediction model of early-age autogenous shrinkage strain of ICC reinforced with Barchip fiber based on the age-dependent parameter on ultrasonic velocity was proposed.