Effects Of Polycarboxylate Superplasticizer Research Articles

Influence of polycarboxylate superplasticizer and polyacrylamide on mirror effect of fair-faced concrete

This work successfully prepared fair-faced concrete with mirror effect. The gray value standard deviation, porosity, crack rate and glossiness of the concrete surface were used to characterize the apparent quality of fair-faced concrete. The effect of polycarboxylate superplasticizer and polyacrylamide viscosity-modifying admixture on mirror effect of fair-faced concrete was investigated. The changes of hydration products and microstructure of fair-faced concrete were monitored by the measurements of X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM) and mercury intrusion porosity (MIP), and the potential mechanism was analyzed. The results indicate that the polyacrylamide reduces the number and size of Ca(OH)2 and change the morphology of Ca(OH)2 crystals from large-size parallel stacking state to small-size edge corrosion structure. The polyacrylamide can refine the pore size of concrete, the most probable pore size at the optimum dosage is 13.73 nm, which is much lower than that at other dosages. The usage of the polycarboxylate superplasticizer will introduce air, which has adverse effect on the concrete surface. But polycarboxylate superplasticizer can also improve the flowability of concrete and make bubbles easy to discharge. The combined action of polycarboxylate superplasticizer and polyacrylamide contributes the fair-faced concrete for better mirror effect.

Experimental Study on the Effect of Polycarboxylate Superplasticizer on the Performance of Cement-Based Grouting Materials.

Polycarboxylate superplasticizers BMC-L and BMC-S were utilized as modifiers in the formulation of novel cement-based grouting materials. Indoor tests were conducted on 32 groups of cement slurries, varying by water-cement ratio (0.5:1 and 0.6:1) and modifier content (0, 2‱, 4‱, 6‱, 8‱, 10‱, 12‱, and 14‱), to test their density, funnel viscosity, water separation rate, and stone rate. Four groups of slurry modified with BMC-L were selected as the preferred slurry, and the apparent viscosity test, uniaxial, and triaxial compression test of the slurry stone body were conducted. The study investigated the influence of BMC-L on various properties of the slurry, including its apparent viscosity, uniaxial compressive strength, stress-strain relationships, shear strength parameters, and elastic modulus. Ultimately, the pore structure and phase composition of the slurry stone body were detected by Nuclear Magnetic Resonance (NMR) and X-ray Diffraction (XRD), and the impact of BMC-L on slurry performance was examined from a microstructural perspective. Results indicate that the two polycarboxylate superplasticizers exert minimal influence on the density and water separation rate of the slurry. Within the effective incorporation range of the polycarboxylate superplasticizer, increasing the dosage correlates with a decrease in both the stone rate and viscosity of the slurry. BMC-L significantly enhances the mechanical properties of the slurry stone body by promoting more complete cement hydration and reducing porosity. The uniaxial compressive strength of slurry stone body with a 6 ‱ BMC-L dosage reached 29.7 MPa after 7 days and 38.5 MPa after 28 days of curing, representing increases of 118.4% and 64%, respectively, compared to masonry with 0 BMC-L dosage. The shear strength parameters and elastic modulus of the slurry stone body also showed corresponding increases.

Rheological properties of seawater-mixed seashell powder calcined slag cement slurries: Effect of polycarboxylate superplasticizer and temperature

In this study, the effects of temperature and a polycarboxylate superplasticizer (PCE) on the rheological properties of seawater-mixed seashell powder calcined slag cement (SCSC) slurries were examined, revealing the mechanism of action of the PCE in them. The results showed that the shear stress and viscosity of the seawater-mixed SCSC slurries tended to decrease and then increase with increasing PCE content, reaching a minimum value at 0.8% PCE content, reducing the viscosity by 31.8% compared to the SCSC slurry without PCE. Temperature variations did not change the flow pattern of the seawater-mixed SCSC slurries; however, the rheological parameters were greatly affected. The viscosity, shear stress, and consistency coefficient decreased gradually with increasing temperature, whereas the rheological index exhibited the opposite trend.

Effects of polycarboxylate superplasticizer and hydroxypropyl methylcellulose on the properties of ferric-rich sulfoaluminate cement

Ferric-rich sulfoaluminate cement (FR-SAC) is a promising low-carbon cement and is usually used to prepare precast products due to its short setting time. However, the fast setting of FR-SAC paste also leads to its poor fluidity and workability. Polycarboxylate superplasticizer (PCE) and hydroxypropyl methylcellulose (HPMC) can improve the fluidity and viscosity but may affect other properties of FR-SAC products. To get a suitable performance of FR-SAC by adding PCE or HPMC, the properties of FR-SAC paste with PCE and HPMC added and their influence mechanism were explored. The results indicate that PCE adsorbs on the surface of positively charged ettringite in the slurry under the electrostatic attraction, which makes the negatively charged or uncharged FR-SAC particles uniformly dispersed in the slurry, thus regulating the rheology and other properties of FR-SAC paste. The compressive strength of FR-SAC paste increases with the increase of PCE addition. PCE slightly retard the early hydration rate of FR-SAC but does not affect the formation of later hydration products. Adding HPMC to FR-SAC paste can decrease the fluidity and increase the viscosity of FR-SAC paste but has little effect on its hydration properties. Therefore, when PCE and HPMC are used to modulate the rheology of FR-SAC paste, it is necessary to combine the utilization process and compressive strength requirements to keep both the rheological parameters and compressive strength in the suitable condition.

Effect of chain transfer agents in polycarboxylate superplasticizer on slump‐retention of concrete

AbstractTwo types of slump‐retention polycarboxylate superplasticizers (PC‐M and PC‐S) were synthesized by using 3‐mercaptopropionic acid or sodium hypophosphite as chain transfer agents, the effects of polycarboxylate superplasticizers on slump‐retention of cement and concrete were investigated, and the mechanism of action and the structure of polycarboxylate superplasticizers were investigated by using conductivity, complexing Ca2+ concentration, gel permeation chromatography (GPC), nuclear magnetic resonance hydrogen spectroscopy (1H‐NMR), and nuclear magnetic resonance phosphorus spectroscopy (31P‐NMR). The results indicated that the slump flow of cement paste mixed with PC‐M was increased quickly within 60 min and then lost gradually, while PC‐S increased slowly and evenly within 240 min. The slump flow of concrete mixed with PC‐S reached 405 mm after 150 min, but the concrete mixed with PC‐M was almost no fluidity after 150 min. The conductivity of the PC‐M aqueous solution decreased quickly within 45 min, then slowly decreased, while the conductivity of the PC‐S aqueous solution decreased slowly within 180 min. PC‐M had a much greater complexation ability of Ca2+ than PC‐S. The composition and structure of the two slump‐retention polycarboxylate superplasticizers were altered by different chain transfer agents, and the hydrolysis‐adsorption capacity of each component was different. The rate of hydrolyzation‐adsorption of each component was PC‐M3 ≈ PC‐S3>PC‐M1>PC‐M2 ≈ PC‐S1>PC‐S2. The faster the adsorption rate, the faster the slump flow loss of concrete.

Effect of the structure of macromonomer in polycarboxylate superplasticizer on slump-retention of concrete

Three kinds of slump-retention polycarboxylate superplasticizers(52HPC4, 52IPC4, and 52EPC4) were synthesized by using HPEG, IPEG, or EPEG as macromonomers. The effects of polycarboxylate superplasticizers on the slump-retention of cement and concrete were investigated. The mechanism of action was explained by the composition of PCE polymers and monomer sequences (EHE, HHE, or HHH), which were investigated by using conductivity, GPC, 1H-NMR, and 13C-NMR. The results indicated that the slump flow of cement paste mixed with 52EPC4 was increased quickly within 120 min, while 52IPC4 doesn’t change within 240 min. Concrete mixed with 52IPC4 had the best slump-retention performance reaching 440 mm after 150 min, but concrete mixed with 52HPC4 was almost no fluidity after 120 min which had the largest slump flow loss through time than that containing other PCEs, and the conductivity of 52IPC4 aqueous solution decreased more slowly than other PCEs. Because of the highest content of effective PCE polymers, and the largest steric hindrance to ester bond resulting in the concrete had the best slump-retention performance when mixed with 52IPC4, because of the smallest steric hindrance to ester bond resulting in the fastest increase spread flow of cement paste which mixed 52EPC4, because of the highest content of low molecular polymers and the lowest content of effective PCE polymers in 52HPC4 resulting in the smallest initial slump flow of concrete, and the largest slump flow loss through time of concrete, even though the steric hindrance effect was larger than 52EPC4.

Effect of Polycarboxylate Superplasticizer in Ordinary Portland Cement and Sulfate Resistant Cement

Polycarboxylate superplasticizers (PCE) are the most widely used admixtures in today’s cementitious construction materials. The molecular structure has a decisive influence on the effectiveness of PCE, which also can be tailored to serve in a different cementitious system. The current study investigates the influence of the backbone charge density of PCE on the rheology, hydration kinetics, and adsorption behavior of ordinary Portland cement (OPC) and sulfate-resistant cement (SRC). The results indicate that regardless of the PCE type, OPC requires a higher amount of PCE to be adsorbed to induce changing of rheological parameters and hydration kinetics. Regardless of the cement type, the PCE with a higher charge density exhibits higher adsorption behavior, corresponding to lower viscosity measurement. Compared to OPC, SRC is more sensitive to the introduction of both PCEs and has a lower saturation dosage, indicating that SRC generally provides better workability properties regardless of the PCE.

Development of solid waste-based self-insulating material with high strength and low thermal conductivity

Foam concrete as a thermal insulation material has been widely used to meet building energy conservation requirements. In this study, a low-clinker foamed concrete was prepared with an amount of solid waste, including fly ash, carbide slag, and glauber's salt, up to 80%. The effect of polycarboxylate superplasticizers (PCs) in the preparation process was examined to improve the mechanical properties of this particular system. The characteristic of hydration products and the pore structure was analyzed to illuminate the PCs influence on the hydration process. The outcomes demonstrate that the PCs can effectively improve the slurry's fluidity, enhance its compressive strength, and decrease its average diameter. Low-clinker foamed concrete's compressive strength reached 5.3 MPa, and its thermal conductivity reached 0.1556 W/(m·K). It was concluded that foam concrete has the potential to be widely used in green buildings due to its high strength and low thermal conductivity.

Reactivity of cemented paste backfill containing polycarboxylate-based superplasticizer

Superplasticizers are used in the preparation of cemented paste backfill (CPB) to improve its rheological properties. CPB produced from sulphide-bearing tailings can generate acid mine drainage (AMD), which has negative environmental impact. The AMD potential can be assessed based on the reactivity of the CPB when exposed to the atmosphere. However, the effect of superplasticizers on the reactivity of CPB is unknown. This paper presents findings from experimental investigations on the effects of polycarboxylate superplasticizers (PCSP) on the reactivity of CPB containing pyrite. The reactivity of cured CPB specimens was determined by monitoring the rate of oxygen consumption in an enclosed chamber. Microstructural tests, namely mercury intrusion porosimetry, X-ray diffraction, and thermogravimetric analyses were also carried out to have a better understanding of the reactive mechanisms. The results obtained show that the addition of PCSP leads to a proportionate reduction of reactivity. The admixture causes the refinement of the pore structure of the CPB by mainly improving binder hydration and self-consolidation. It was also observed that less pyrite crystals were present in the CPB containing the superplasticizer. High curing temperature was also found to improve binder hydration, leading to a decrease in reactivity of CPB with PCSP. Due to the micro-filer effects on the CPB pore structure, partial replacement of cement with fly ash and blast furnace slag also decreases the reactivity of CPB. These research findings will be valuable for the design of cost-effective, more environmentally friendly and sustainable CPB structures.

Effect of polycarboxylate superplasticizers on the growth of ettringite in deionized water and synthetic cement pore solution

Ettringite is the crucial hydrating phase controlling the rheology of the paste at the beginning of the cement hydration. Yet, while previous studies speculate on how the rheology of the paste depends on the morphology and size of ettringite, only limited data examine this question systematically in the C3A-CaSO4 system, probably linked to characterization limitation arising from the heterogeneous of cement paste and a small proportion of ettringite. On the other hand, polycarboxylate ether/ester (PCE) are well known to greatly modified the morphology and size of ettringite. It remains however unclear how PCE adsorption affects the growth of ettringite. In this paper, the effects of dosages of PCE on the growth of ettringite in deionized water and synthetic cement pore solution were investigated by using X-ray diffraction (XRD), thermogravimetry–differential thermogravimetry (TG-DTG) analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microcopy (SEM) and total organic carbon (TOC) analyzer. Adsorption kinetics and isotherms of PCE on the surface of ettringite crystals were also examined. PCE exerted no effect on the types of products, but its adsorption changed the proportion, stability, and morphology of ettringite. Sulfate ions and PCE were adsorbed on the face of rectangular prism of ettringite crystals preferentially, which limited their growth in the {101¯0} faces and resulted in their longitudinal growth. The inhibition effect of PCE on the growth of ettringite crystals is positive correlated with its adsorption amount on ettringite and is weakened as the crystallization time increases. The adsorption kinetics and isotherms of PCE on the surface of ettringite followed the pseudo-second-order and Freundlich equations respectively.

Effects of polycarboxylate superplasticizer equipped with β-cyclodextrin as the terminal group on the fluidity of montmorillonite-containing cement paste

In this study, β-Cyclodextrin (β-CD) as the terminal group was grafted on polyoxyethylene (PEO) via click reaction for preparing monovinyl β-Cyclodextrin monomer (β-P). Then β-P was employed to synthesize a polycarboxylate superplasticizer with β-CD grafted on the side chain [PAA-g-(β-P) n HPEG]. The functional groups, molecular weights, and molecular weight distributions of synthesized copolymers PAA-g-(β-P) n HPEG were characterized by Fourier transform infrared spectra (FT-IR), 1H nuclear magnetic resonance spectroscopy (1H NMR), and gel permeation chromatography (GPC). The dispersion performance of PAA-g-(β-P) n HPEG in cement paste containing montmorillonite (MMT) clay was tested. Sorption measurement and X-ray diffraction (XRD) analysis revealed that the PAA-g-(β-P) n HPEG intercalated less into the interlayer space of MMT than PAA-g-HPEG only with PEO as the side chain. β-CD as the terminal group grafted on the end of the side chain of PCE effectively hindered PCE sorption on MMT and enhanced the clay-tolerance property of PAA-g-(β-P) n HPEG. This study offered a new idea in designing polycarboxylate superplasticizers to lower their clay sensitivity.

Effect of polycarboxylate superplasticizer on hydration and properties of belite ye’elimite ferrite cement paste

Belite-Ye’elimite-Ferrite (BYF) cements have received increasing attention in view of their lower CO2 footprint and their interesting performances. This work deals with the effect of polycarboxylate superplasticizer (SP) on BYF cement paste. It was found that SP dosage must be low in order to avoid destabilization, and thus improve the resistance to bleeding and segregation. Also, the good affinity of polycarboxylate-based superplasticizer with cement surface improves the cement particles dispersion and causes a significant diminution of the yield stress during the low activity period. Furthermore, it is shown that SP causes a delay in the early age hydration, inducing a decrease in the compressive strength at early age while it increases them after 90 days.

Effects of polycarboxylate superplasticizers with different side-chain lengths on the resistance of concrete to chloride penetration and sulfate attack

The service life of concrete structures shortened by corrosive ions endangers public safety and results in considerable repair costs worldwide. For the objective of producing more sustainable concrete, how do polycarboxylate superplasticizers (PCEs) with different side-chain lengths affect the resistance of concrete to chloride penetration and sulfate attack is studied. The foam and adsorption behavior of PCEs, the heat release of cement hydration, the resistance of concrete to chloride penetration and sulfate attack and the microstructure observation were investigated to achieve the aim. Results show that the shortest side-chain PCE (M400C3.5, nEO = 9) had the best effect on improving the resistance of concrete to chloride penetration and sulfate attack. Among all the tested concrete samples, the concrete containing M400C3.5 exhibited the lowest total porosity and the most compact structure. The largest adsorption amount of M400C3.5 on the cement surface led to the most significant retardation of the initial cement hydration. This retardation may reduce the number of microcracks resulting from fast heat release.

Effects of PCE on the Dispersion of Cement Particles and Initial Hydration.

The effects of polycarboxylate superplasticizers (PCEs) on the dispersing properties and initial hydration of cement particles with various water-to-cement (w/c) ratios was investigated, including the water film thickness (WFT), rheology, fluidity, adsorption of PCEs, zeta potential, degree of hydration, hydration products. The experimental results demonstrate that the initial rheological and fluidity parameters were more sensitive to the PCE dosage at a lower w/c because the WFT and the zeta potential on cement particles change more significantly. Moreover, the higher adsorption amounts of the PCEs at a lower w/c lead to a stronger inhibition of the initial hydration, whilst, at the same PCE dosage, the cement pastes have a more rapid fluidity loss and quicker hydration reactions at a higher w/c due to a lower adsorption amount of the PCE on cement particles.

Effects of polycarboxylate superplasticizer on rheological properties and early hydration of natural hydraulic lime

As one of the main materials for grouting repair, the workability of natural hydraulic lime (NHL) has been concerned widely. In this paper, effects of polycarboxylate superplasticizer (PCE) on rheological properties and early hydration of natural hydraulic lime (NHL2) and their correlations were systematically investigated. Results show that the fluidity of NHL2 paste improves significantly and tends to a stable state at a certain dosage in the presence of PCE. It is found that PCE makes the flocculated structures in paste disassemble and produces more small particles. The results can lead to a decrease in yield stress and plastic viscosity, further improving rheological properties. The retardation effect of PCE on NHL2 hydration can depress the crystallization and early formation of calcium hydroxide Ca(OH)2 and calcium silicate hydrate (C–S–H). The effect can reduce water consumption during mixing, which has a positive influence on rheological properties.

Effect of polycarboxylate superplasticizer on fluidity and rheology of cement slurry containing silica fume

The effect of polycarboxylate superplasticizer on the fluidity and rheology of cement - silica fume - water paste was investigated. The changes of dispersion degree, yield stress and plastic viscosity of paste with different superplasticizer content were analyzed. The results show that the rheological properties of paste with different superplasticizer content conform to Herschel-Bulkley model. The shear thinning of the slurry is manifested as a typical yielding pseudoplastic fluid characteristic. When the content of superplasticizer is less than 1.0%, the plastic viscosity and yield stress decrease and the fluidity increase with the increase of plasticizer content. When the content of superplasticizer is more than 1.0%, the yield stress decreases slightly and the plastic viscosity increases with the increase of plasticizer content. The fluidity decreases with the increase of yield stress, and there is a good correlation between them.

Effect of superplasticizer in anti-washout admixture on paste

Anti-washout admixture used for anti-washout underwater concrete is composed of flocculant (e.g., paste stabilizer), superplasticizer, setting retarder, strengthening agent, etc. Good compatibility among those constitutes is necessary to release the vast material potential of anti-washout admixture. In the study, effects of polycarboxylate superplasticizer on fresh cement paste mixed paste stabilizer of various ionic type were experimentally investigated. Based on the experimental results, the optimizations on the ionic type and molecular weight of paste stabilizer, regarding the compatibility with polycarboxylate superplasticizer, were hence obtained. Additionally, suitable content ranges of polycarboxylate superplasticizer, molecular weight and content of paste stabilizer have been determined through systematic tests, such as saturation point test, fluidity test, and anti-washout test.

Effects of polycarboxylate superplasticizers on fluidity and early hydration in sulfoaluminate cement system

Three polycarboxylate superplasticizers with varied molecular structure, denoted as PCE4, PCE22 and PCE25 were synthesized by radical copolymerizing acrylic acid (AA) and α-methallyl-ω-hydroxy poly (ethylene glycol) with monomer ratio of 4, 22 and 25 respectively. 2-Acrylamido-2-methylpropane sulfonic acid was used to partly replace AA in basis of PCE22 for preparation of PCE18S4. Flow test and adsorption measurement reveal that the higher charged PCE22 and PCE18S4 exhibit stronger adsorption capability on mineral surfaces and hence better fluidizing effect than the lower charged PCE4. Although PCE25 exhibits sufficient adsorption, its dispersion capability is inferior because of the lower side chain density which leads the polymer prone to be crosslinked by Ca2+ ions present in pore solution. As shown in the measurements by XRD, BET and calorimetry, the polymers with higher carboxylate content show stronger suppressive effect on ettringite formation and cement hydration and hence perform better in fluidity retention.

Effects of Polycarboxylate Superplasticizers with Different Functional Units on Early Hydration Behavior of Cement Paste

AbstractEffects of polycarboxylate superplasticizers (PCEs) with different functional units on the flowability, hydration heat, and hydration products of cement paste were investigated. Two kinds o...

Effects of PCEs with various carboxylic densities and functional groups on the fluidity and hydration performances of cement paste

In this research, effects of polycarboxylate superplasticizers (PCEs) with various carboxylic densities and functional groups on the adsorption behavior, dispersing performance as well as hydration characteristics of cement paste were systematically investigated. PCEs with different architectures were synthesized through substituting acrylic groups with sulfonic groups, ester groups, acylamino group, and changing the molar ratio between HPEG and acrylic groups in the PCE backbones under free radical solution polymerization. The molecular structures of different PCEs were characterized by size exclusion chromatography (SEC). The adsorption isotherms and the dispersing properties of different molecular PCEs were measured by total organic carbon measurement (TOC), mini-slump cone and shear rheometer, respectively. Cement hydration characteristics in the function of various molecular PCEs were investigated through X-ray diffraction (XRD), differential thermal analysis-thermogravimetric analysis (DTA-TG) as well as isothermal calorimetry. Results show that carboxylic density and the functional groups in PCE molecules significantly influence the adsorption behavior and the dispersing performance of PCEs. The increase in carboxylic density and integrating sulfonic groups into PCE backbone can enhance the adsorption capability of PCEs onto cement grain surface, which hence generate higher initial dispersing property. PCEs with higher carboxylic density hinder the cement hydration during the induction period, but promote the maximum hydration degree during the acceleration period. Integrating sulfonic group into PCEs backbone significantly promotes the cement hydration, while integrating amide groups or ester groups into the backbone of PCEs depresses the cement hydration process. The variation in cement hydration caused by the addition of different molecular PCEs is almost diminished at 28 d.