Polycarboxylate Ether Research Articles

Insights into the viscoelastic properties of cement paste based on SAOS technique

Understanding the viscoelastic properties of cement paste is beneficial to pumping, formwork casting and 3D printing of cement-based materials. This paper presents new insights into the viscoelastic properties of cement paste with various compositions. Several parameters, including critical strain, storage modulus and viscoelastic yield stress obtained from small amplitude oscillatory shear (SAOS) test, are selected to characterize the viscoelasticity of fresh cementitious paste. Results reveal that increasing water-to-cement (w/c) ratio reduces the storage modulus at linear viscoelastic region (LVER) and viscoelastic yield stress of cement paste, whereas higher w/c increases the critical strain. The replacement of cement by fly ash has no significant influence on the critical strain of cement paste. Due to the improvement of cohesive bonding between cement particles by nanoparticles, the incorporation of nano-Fe3O4 particles results in an increase in the storage modulus at LVER, critical strain and viscoelastic yield stress. The critical strain of cement paste gradually increases with the concentration of polycarboxylate ether (PCE) superplasticizer, which possibly can be attributed to the interactions and entanglement of PCE molecules adsorbed onto the solid particles. By contrast, cement pastes with low PCE additions exhibit an increase in the viscoelastic yield stress, while higher PCE additions significantly decrease the storage modulus at LVER and viscoelastic yield stress of cement paste.

A study on the interactions between polycarboxylate ether superplasticizer and montmorillonite

The adsorption of polycarboxylate ether (PCE) superplasticizer on the surface of cementitious materials is a prerequisite for its dispersion and water reduction capability. This paper investigated the adsorption isotherms and kinetics of PCE on montmorillonite (MMT) at 278, 288, 298, and 308 K, respectively. Based on the adsorption behaviors, the critical intercalation concentration of PCE was estimated, and the characterizations of surface adsorption and intercalation were examined. Results show that when its concentration is <0.9 mg/mL, PCE is mainly adsorbed on the surface of MMT. The galleries of MMT are intercalated by the side chain of PCE completely at a concentration of 10 mg/mL. The adsorption isotherms and kinetics of PCE on MMT follow the Freundlich isotherm equation and the pseudo-second-order adsorption equation, respectively. The surface adsorption of PCE is not affected by the temperature, but it presents a lower adsorption saturation at a higher temperature. PCE shows a monolayer thickness of 5.63 nm on the surface, but intercalation conforms to multi-layer adsorption.

Influence of superplasticizer on workability and strength of ambient cured alkali activated mortar

Alkali activated materials contain aluminosilicates, which can be used for building with a low environmental impact by repurposing waste resulting in cost-effective construction. The impact of nature and superplasticizer dosage on fly ash slag-based ambient cured mortar activated with sodium silicate and sodium hydroxide is not yet definitive. This paper studies the influence of various superplasticizers on fly ash-based ambient cured mortar activated with sodium silicate and sodium hydroxide. The effect of superplasticizers was evaluated by adding various superplasticizers including melamine, polycarboxylate ether and naphthalene-based superplasticizers in different dosages from 0 to 3% at 0.5% intervals. Fresh properties of alkali-activated mortar with various percentages of superplasticizer were tested using flow table apparatus and compared with mortar without superplasticizer. The hardened property of the alkali-activated mortar was tested by checking the compressive strength of the mortar cube. From the test results, naphthalene and polycarboxylate ether-based superplasticizers are compliant with alkali-activated mortar. Melamine-based superplasticizer shows a slight reduction on strength of alkali-activated mortar. In the ambient cured mortar, the optimum concentration for naphthalene and polycarboxylate ether-based superplasticizers is 2.0 percent, whereas melamine-based superplasticizer exhibits maximum strength for 2.5 percent. Even though naphthalene and polycarboxylate-based superplasticizers are effective for alkali-activated mortar, the most efficient type is the polycarboxylate ether-based superplasticizer.

Influence of Superplasticizer Dosage on Workability and Mechanical properties of Concrete made with Recycled Aggregate

This study investigated the effect of adding a type of superplasticizer (polycarboxylate ether -PCE) on the workability and mechanical properties of concrete containing recycled coarse aggregate (RCA). The effect of increasing the PCE dosage while changing the water/cement ratio on RCA strength was also studied. To accomplish these goals, three groups of concrete mixtures were prepared. The variable in these groups was the water/cement ratio (0.53, 0.57, and 0.615). In each group, the natural aggregate was replaced by two proportions of RCA (50 and 100%) and different proportions of PCE were added for each replacement ratio. The findings encourage the use of PCE in recycled concrete. It was found that the addition of PCE improves the properties of recycled concrete in terms of workability and compactness. The addition of PCE also compensates for the compressive strength that is lost due to the replacement of natural aggregate with recycled coarse aggregate.

Experimental evaluation on behavior of poly propylene fiber-reinforced concrete containing Poly Carboxylate Ether and E205 additives

Corrosion is a critical challenge that reinforced concretes are facing that need to be addressed considering environmental circumscriptions. This research investigates various characteristics of polypropylene fiber-reinforced concrete experimentally. Six contents of chemical admixtures are investigated regarding rapid chloride permeability, water absorption, electrical resistivity, and compressive strength. Moreover, quantitatively, the energy-dispersive X-ray microanalysis is employed to specify the cementitious matrix’s chemical compositions. Correspondingly, the cementitious matrix’s chemical mechanism is analyzed by utilizing X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and X-ray Fluorescence (XRF) analysis methods. The results indicate that a minor increment in the content of chemical admixtures decreases chloride permeability, while an increase results in an electrical resistivity up urge. Furthermore, the experimental results demonstrate that specimens with polypropylene fiber and polycarboxylate ether perform better than specimens containing polypropylene fiber and E205 in compressive strength. It has been discovered that specimens, including Poly Carboxylate Ether, demonstrated lower water absorption than the levels observed in specimens with E205. According to test results, it can be concluded that the durability and compressive strength of fiber reinforced concrete with polypropylene fibers are increased by the addition of chemical admixtures. • Adding polycarboxylate ether and E 205 to PPFRC, increases the concrete’s resistance. • Polycarboxylate ether and E205 reduce cracks in PPFRC. • Adding polycarboxylate ether and E205 to PPFRC reduces concrete water absorption.

A new approach for proportioning self-consolidating earth paste (SCEP) using the Taguchi method

Rammed earth (RE) construction is an ancient sustainable construction method, which offers various economic and environmental advantages such as the availability of local materials. However, RE construction is a very time-consuming and labor-intensive process due to the consolidation required to achieve the targeted performance. The use of self-consolidating earth concrete (SCEC) can facilitate casting and speed the construction process. However, developing SCEC is challenging due to the presence of clay in earth, which can significantly hinder flowability. Optimizing the paste matrix of SCEC, namely self-consolidating earth paste (SCEP), is essential for achieving targeted workability performance of SCEC. In this study, the Taguchi method was employed to evaluate the effect of various mixture parameters, including clay and admixture type, cement content, and water-to-powder (W/P) and cement-to-clay (Ce/Cl) ratios to proportion SCEP mixtures. These parameters form different binder compositions with various Atterberg limits and water contents to investigate the compatibility and efficiency of different admixture types on the workability and compressive strength of their corresponding SCEP mixtures. Adequate clay dispersion was achieved using sodium hexametaphosphate (NaHMP) whereas polycarboxylate ether (PCE) was only efficient on cement particles. Sodium silicate (NaSil) did not contribute to dispersion of single-powder systems, while sodium polynaphtalene (PNS) and non-esterified polycarboxylate (NE-PC) showed compatibility with both clay and cement particles. Signal-to-noise ratio (S/N) analyses revealed that lower cement content and higher W/P and Ce/Cl resulted in lower admixture demand for targeted workability and marsh cone test (MCT) values. Regarding 1-day compressive strength, to facilitate the demolding process, PNS, PCE and NaSil showed the highest efficiency. As concluded from the analysis of variance (ANOVA), clay and admixture type had the highest contribution on workability, while cement content and W/P were significant on compressive strength. Several theoretical models were also established to predict the workability of SCEP mixtures from Atterberg limits of the corresponding soil. Finally, a new SCEP proportioning approach was proposed based on the established models and compressive strength contours to be used for different earth types.

Effect of anchoring groups of polycarboxylate ether superplasticizer on the adsorption and dispersion of cement paste containing montmorillonite

Four types of polycarboxylate ether (PCE) superplasticizers with -COO- (C-PCE), -NH3+ (D-PCE), –SO3- (S-PCE) and –COOR (H-PCE) were synthesized. Their molecular structures were characterized by Gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance spectrum (1H NMR). The adsorption behavior of PCEs was investigated by adsorption amount and layer thickness on cement paste without and with montmorillonite (MMT). Time-dependent flowability and rheological properties of paste were measured and the effects of these PCEs on the hydration of paste were examined. Based on the adsorption behavior of PCEs and fresh properties of pastes without and with MMT, the sensitivity of these PCEs to MMT was also assessed. Results show that D-PCE, S-PCE and H-PCE exhibit lower adsorption amounts, but thicker adsorption layer on cement paste than that of C-PCE. S-PCE shows the best dispersion and retention capability, even in the presence of 3% MMT, and has the smallest sensitivity index. However, H-PCE is the worst one. Paste with D-PCE exhibits comparable initial flowability to that of C-PCE, but higher flowability loss.

Quantifying the Workability of Calcium Sulfoaluminate Cement Paste Using Time-Dependent Rheology.

Poor workability is a common feature of calcium sulfoaluminate (CSA) cement paste. Multiple chemical admixtures, such as set retarders and dispersants, are frequently employed to improve the workability and delay the setting of CSA cement paste. A quantitative assessment of the compatibility, efficiency, and the effects of the admixtures on cement paste workability is critical for the design of an appropriate paste formulation and admixture proportioning. Very limited studies are available on the quantitative rheology-based method for evaluating the workability of calcium sulfoaluminate cement pastes. This study presents a novel and robust time-dependent rheological method for quantifying the workability of CSA cement pastes modified with the incorporation of citric acid as a set retarder and a polycarboxylate ether (PCE)-based superplasticizer as a dispersant. The yield stress is measured as a function of time, and the resulting curve is applied to quantify three specific workability parameters: (i) the rate at which the paste loses flowability, (ii) the time limit for paste placement or pumping, marking the onset of acceleration to initial setting, and (iii) the rate at which the paste accelerates to final setting. The results of the tested CSA systems show that the rate of the loss of flowability and the rate of hardening decrease monotonously, while the time limit for casting decreases linearly with the increase in citric acid concentration. The dosage rate of PCE has a relatively small effect on the quantified workability parameters, partly due to the competitive adsorption of citrate ions. The method demonstrated here can characterize the interaction or co-influence of multiple admixtures on early-age properties of the cement paste, thus providing a quantitative rheological protocol for determining the workability and a novel approach to material selection and mixture design.

Polycarboxylate ether superplasticizer with gradient structure: excellent dispersion capability and sulfate resistance

Polycarboxylate ether superplasticizer with gradient structure: excellent dispersion capability and sulfate resistance

Experimental study of admixture on Bentonite clay reinforced concrete as a partial substitute to cement

The mortar mixtures were prepared in various proportioned with cement to sand ratio of 1:3 and 1:4. The reinforced concretes were cast for the same flow level but different percentages of clay (0, 5, 10 &amp; 15%) dosage. The prepared motor concrete subjected for structural study and mechanical property analysis. In FTIR spectra shows predominant peaks are observed the presence of admixture and clay in the concrete motor. The XRD spectra indicates the formation tetrahedrally arrangement of silicate and octahedrally arrangement of aluminate groups in clay mixed concrete. The surface morphology significantly improved upon adding of different admixture as examined in SEM image. The mechanical study revealed that the compressive strength increases with increase in clay percentages up to C-2 (10 wt %) due to the strong adhesion because of mixture of water reduce and water repellent which makes better compact and reduce porosity. The addition of slump flow improved due to presence of polycarboxylate ether and the evident workability loss started after the resting time of 25 min.

Effective medium electrical response model of carbon nanotubes cement-based composites

The electrical properties of carbon nanotubes (CNT) cement-based composites have been modeled in previous works by circuit models or homogenization theories. An alternative approach is the use of an effective medium theory with induced polarization: In this work, a new model based on the generalized effective medium theory of induced polarization (GEMTIP) with cylindrical inclusions is proposed. The presented results and discussion show its applicability to interpret the electrical impedance spectra of cylindrical cement samples doped with multi-walled CNTs (MWCNTs). The MWCNTs were dispersed in different media: one nonionic surfactant, two superplasticizers, a cationic type polycarboxylate ether, and an anionic type naphthalene sulfonate. Particle dispersion and their sizes were analyzed by Ultraviolet–Visible (UV–Vis) spectroscopy, and Scanning Electron Microscopy (SEM) measurements. Two electrode electrical impedance spectra were measured and analyzed by circuital models and the proposed GEMTIP model. The results demonstrate the efficiency of the proposed model in describing the Alternating Current (AC) response of cement/CNT composites irrespective of the dispersant agent used to elaborate the samples.

WAYS TO MANAGE THE QUALITY OF NANOCRETE

"This article presents an integrated approach to the design of the concrete composition, which contains a combination of various types of modification of the concrete mixture by introducing a hyperplasticizer based on polycarboxylate ether, as well as reinforcing fibers (anisotropic additive), activation of aggregates, binders and mixing water. It is shown how the reinforcement of concrete cement stone with fibers reduces the formation of shrinkage cracks and increases its frost resistance, and polycarboxylate nanoparticles significantly reduce the amount of water used and the drying time of the material, making the steam treatment stage optional. The article presents the mechanism of action of the hyperplasticizer, the test results of samples-beams and samples-cubes at the age of 28 days, as well as the result. As a result of the action, polycarboxylate particles are adsorbed on the surface of cement grains, repel each other and set the cement mortar in motion. With the help of this approach, a condition is created for the formation of a cement stone nanostructure of various functional actions with the help of nanoparticles already at the initial stage of mixing."

Reinforcement of ultra-low dosage of polycarboxylate ether (PCE) grafted nano-silica sol to the mechanical and durable properties of cement mortar

How good dispersion of nano-SiO2 (NS) plays a great influence on how strong reinforcing efficiency to cement-based materials. In this study, a novel nanohybrid of polycarboxylate ether (PCE) grafted nano-silica sol (PCE@NSS) was prepared by sol–gel methods to chemically adsorb PCE onto NSS. The developed nanohybrid showed a higher ultraviolet–visible (UV–Vis) absorbance and slower sedimentation in alkaline solutions, indicating the better dispersion and stability of PCE@NSS than that of untreated NSS. By this way, only 0.05 wt.% addition of PCE@NSS was helpful to refine the capillary pore size and reduce the total porosity of cement mortar, which in turn improved the compressive and flexural strength of cement mortar by 18.34% and 10.5% at 28 days, respectively. In addition, a reinforcing index (R index) with the ratio of strength enhancement % to dosage % was proposed, indicating that the R index of PCE@NSS showed 10 times higher than that of other NS-based nanomaterials reported in literatures, addressing the highly reinforcing efficiency of PCE@NSS to cement mortar. Furthermore, water absorption coefficient of cement mortar was therefore reduced by 12.7% with 0.2 wt.% addition of PCE@NSS. In conclusion, such an ultra-low dosage of PCE@NSS with better dispersion and stability exhibited great potential to reinforce cement-based materials with highly efficiency, lower cost and reduced carbon emissions.

Synthesis and property of EPEG‐based polycarboxylate ether superplasticizers via RAFT polymerization

AbstractPolycarboxylate ether superplasticizers (PCEs) with comb‐shaped molecular structures have attracted considerable attention in the area of admixtures for construction engineering. However, there are some contradictions in studying the relationship between the molecular structure and property of PCE due to its random structure based on traditional free radical polymerization, which is confused for designing and developing novel PCEs. In this article, a series of reversible addition fragmentation chain transfer (RAFT) polymerization‐based polycarboxylate ether superplasticizers (RPCs) were prepared by the copolymerization of acrylic acid (AA) and ethylene‐glycol monovinyl polyethylene glycol (EPEG). The chemical structure and composition of RPCs were characterized and their adsorption behavior and dispersion properties were conducted. The results demonstrate that the molecular weights of RPCs do not vary significantly with prolonging reaction time, and the actual monomer ratio in RPCs displays a significant change to the feed one due to the monomer reactivity and conversion at higher reaction temperature, which is different from conventional free radical polymerization. The dispersion and adsorption properties of RPCs to cement were evaluated by slurry fluidity tests and total organic carbon (TOC) experiments. The effect of polymerization temperature and time on the dispersion ability has been systematically studied. The results indicate that the dispersion ability and adsorption capacity of RPCs are closely related to their molecular structures. The dispersion ability of RPCs were enhanced with increasing carboxyl group density in a certain range of monomer molar ratios (≤6:1). This study will provide a new platform for designing and developing high‐performance and rational cost‐effective superplasticizers with well‐defined structure and controlled molecular weight.

Both Plasticizing and Air-Entraining Effect on Cement-Based Material Porosity and Durability

The influence of a complex application of both plasticizing and air-entraining effects on concrete with polycarboxylate ether superplasticizer (PCE), air-entraining admixture (AIR), or an anti-foaming agent (AF) is analyzed in this paper with considerations for on the air content, workability, flexural and compressive strength, and freezing–thawing resistance of hardened cement mixtures. The effect of the complex behavior of PCE, AIR, and AF on the porosity of hardened cement mortar (HCM) and freezing–thawing resistance was investigated; freezing–thawing resistance prediction methodology for plasticized mortar was also evaluated. The results presented in the article demonstrate the beneficial influence of entrained air content on consistency and stability of cement mortar, closed porosity, and durability of concrete. Freezing–thawing factor KF depending on porosity parameters can be used for freezing–thawing resistance prediction. With both plasticizing (decrease in the water–cement ratio) and air-entraining effects (increase in the amount of entrained air content), the frost resistance of concrete increases, scaling decreases exponentially, and it is possible to obtain great frost resistance for cement-based material.

Matric suction and its effect on the shape stability of 3D printed concrete

The mix design of 3D printed concrete has adopted various types of binders and additives to enhance its casting performance and shape stability. Matric suction, as an attractive force among partially unsaturated particles of the binders and additives, influences the shape stability of firm cement paste composing 3D printed concrete. Higher matric suction induces higher compressive strength (or green strength) and higher elastic modulus. The extended Mohr–Coulomb failure envelope describes the stress state of the 3D printed concrete considering its matric suction. Variation of the matric suction takes parallel shifting and rotation of the shape failure envelope. The test results on the matric suction finally confirm the effect of binders and additives. Change in the water-to-binder ratio contributes to higher matric suction related to the paralel shift of the Mohr-Coulomb failure envelope, while incorporating nanoclay or polycarboxylate ether affects the internal friction angle of the binder.

Abrasion and Strength of high percentage Graphene Oxide (GO) Incorporated Concrete

Incorporating Graphene Oxide (GO) in concrete composite has been a good alternative to Pristine Graphene due to its hydrophilic nature and its ability to readily disperse in water the consequent cementitious mix. The addition of GO to the cementitious mix has been found to enhance mechanical properties. This paper aims to assess the abrasion resistance of GO incorporated concrete for its application in road pavement design. Experiments for strength in terms of compression, workability in terms of slump and abrasion resistance in accordance with ASTM-C418-20 using a sand-blasting rig are presented in the paper. It is shown that the addition of GO at percentages between 0% to 0.08% (to cement weight ratio), the compressive strength improves by 39% and 26% at 7 days and 28 days, respectively. The addition of GO consequently affected the workability where it was found that the addition of polycarboxylate ether (PCE) (superplasticisers) can drastically improve the workability, which is essential in practical applications. The abrasion was measured for specimens prepared with a high GO percentage between 0.1% to 0.3% and measured at 7 days and displayed a reduction of 70% of abraded volume at 0.3% GO. Finally, the study presents the benefits of using GO where the reduced amount of cement usage will consequently lead to sustainable concrete construction.

An approach to describe the shear-thickening viscosity of cement paste incorporating microfines of manufactured sand

This paper investigates the mechanisms affecting the viscosity in shear thickening regimes of cement pastes. Limestone, slate, and tuff microfines (≤125 μm) with different physical properties obtained in the processing of manufactured sand were employed as additional mineral materials to cement pastes prepared with variable dosages of polycarboxylate ether superplasticizer (PCE) and water-to-cement mass ratios (W/C) of 0.40 and 0.275. Test results show that the addition of microfines reduced the shear thickening properties of cement pastes at a fixed PCE dosage, mainly due to a smaller growth of particle inertial interactions from the pseudo-Newtonian plateau to a given shear rate. But the shear thickening reduction did not always cause a lower increase of the apparent viscosity, Δηthicγ̇, for paste mixtures made with 0.275 W/C, due to a greater enhancement of particle friction contacts. Meanwhile, the shear thickening performance at a given mini-slump flow increased by using the microfines, given the stronger particle friction contacts caused by the increased flow index of Herschel-Bulkley model. This corresponded to a greater Δηthicγ̇ of the pastes. A prediction model of Δηthicγ̇ was proposed based on the mechanisms of particle inertia forces and friction contacts. The model can efficiently characterize particle frictional contact interactions in shear thickening regimes by taking into consideration the flow index, particle packing density, and solid volume fraction, regardless of the W/C and the content and type of microfines.

Effect of Different Chemical Admixtures on Fresh and Hardened Properties of M30 and M40 Grade Concrete

Researchers in the field of concrete technology with the application of different admixtures are always in search of suitable admixtures to improve the workability as well as the strength of any concrete grade. An attempt was made in the present research to use chemical admixtures (superplasticizers) like sulphonated naphthalene based Apple Chemie AC-MENT-ALPHA-X5, polycarboxylic ether based Fosroc Auramix 350, sulphonated naphthalene based Fosroc Conplast SP 430, modified polycarboxylate based Du-bond DUPLAST PC P 2 and modified lignosulphate based Sika PLASTIMENT BV 40 for concrete grades M30 and M40. A literature survey revealed that all identified chemical admixtures are used for 20–25% reduced water content. A study was done to compare M30 and M40 grade concrete in both fresh and hardened states, taking water reduction into account. Experimental results showed that all admixtures demonstrate good paste-up consistency of up to 1%. As the percentage of admixtures increases, there is an increase in surface pores due to more significant air entrainment. Compressive strength results of 1% admixture content for Apple Chemie, Fosroc, and Du-bond were observed to be close to their characteristic compressive strengths for both grades, but Sika and Fosroc Auramix 350 have good compressive strength with less than 1%. As the grade of concrete improves, Conplast's effect reduces, but the Du-bond and Fosroc Auramix 350 perform excellently for split tensile strength. As the grade rises, all admixtures show increasing flexural strength levels. However, Auramix 350, with a 1.5% content for M30 grade, consistently outperforms Sika, which has a 1% content. It helped to employ up to 1% of all admixtures, but Sika reveals a cost increase of 2.5 to 7.3% for 1% and 1.5% admixture additions. The study found that Fosroc Auramix 350 could be used for both grades and still have good workability and strength.

The first experimental evidence for improved nanomechanical properties of calcium silicate hydrate by polycarboxylate ether and graphene oxide

Graphene oxide (GO) efficiently enhances macroscale mechanical properties of cement-based materials. Yet the nanoscale reinforcing mechanism of GO for calcium silicate hydrate (C-S-H), the key binding phase of concrete, remains poorly understood. Moreover, how polycarboxylate ether (PCE)-based superplasticizers affect the nanomechanical properties of C-S-H remains unclear. The intrinsic mechanical properties of the nanocomposites are measured using high-pressure X-ray diffraction. The influences of GO and PCE on the local Ca and Si environments are probed using X-ray absorption spectroscopy. For the first time, we evidence that PCE-induced well-dispersed GO nanoplatelets strengthen the C-S-H basal planes, whereas poorly water-dispersed GO weakly interacts with basal planes and does not strengthen in plane CaO bonds. Both PCE and GO only slightly strengthen C-S-H's c-axis. The bulk modulus of C-S-H/PCE/GO nanocomposite is 190% than pure C-S-H. Functional groups of PCE and GO prefer interacting with the CaO sheets of C-S-Hs instead of silicate tetrahedra.