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Impact of Molecular Structure on Zeta Potential and Adsorbed Conformation of .ALPHA.Allyl.OMEGA.-Methoxypolyethylene Glycol-Maleic Anhydride Superplasticizers
Abstract
α-Allyl-ω-methoxypolyethylene glycol - maleic anhydride copolymers were synthesized with side chain lengths nEO from 0-130 and characterized by aqueous GPC. A representation of their molecular conformation (e.g. worm-, brush- or star-like polymers) was developed. The amount of polymer adsorbed on cement rapidly decreases with increasing side chain length nEO. Zeta potential measurements using the electroacoustic method in cement paste with w/c = 0.5 indicate that worm-like copolymers with nEO ≤ 7 adsorb flat ("train" type) and form a densely packed, thin polymer film. In this case, the adsorbed amount of copolymer is high. For star polymers with nEO ≥ 34, preferred orientation of the polymer main chain is perpendicular to the cement surface ("tail" type). The result is a thick polymer layer, with a second electrochemical double layer on top. For star polymers, the adsorbed amount is low because of the higher surface occupancy of horizontally layered side groups.
... On the other hand, the adsorption monolayer on the surface of cementitious materials can be formed by the preferred adsorbed PCE molecular and steric repulsion force develops as it starts to overlap, resulting in the decrease of attractive force between particles needed to be overcame for paste to flow and the enhancement of workability of paste [12]. PCE shows the different adsorption affinity on cement minerals and early hydration products, presenting the larger and quicker adsorption on C 3 A and C 4 AF, while the surface of C 2 S, C 3 S has lower adsorption [13,14]. It is believed that the adsorption of PCEs is closely related to the molecular structures of PCEs [15,16]. ...
... PCEs with different side chain length can be synthesized and their effects on the adsorption are shown in Figure 11. The largest adsorbed value of 1.2 mg/g for PCE with nEO of 7 can be observed, while that with nEO of 130 exhibits the smallest value (0.3 mg/g) [13]. Generally, the stronger hindrance of adsorption is produced for PCE with longer side chain than that with shorter side chain during the adsorption process [32,63]. ...
... It means that the decreased adsorption induced by competitive adsorption of SO 4 2is the main reason for the decrease in flow area with Na 2 SO 4 , while the Figure 11. Effect of side chain length of PCE on its adsorbed amount [13]. phenomenon caused by NaCl ascribes to the effect of ions on adsorbed amount and molecular size of PCE. ...
Adsorption of polycarboxylate ester/ether (PCE) superplasticizer on the cementitious materials and steric effect of its side chain determine to its dispersion and water-reducing capability. This paper reviews the effect of molecular structure of PCE and characteristics of cementitious system on its adsorption behavior, and build up the relationship between adsorption of PCE and its dispersion performance. The role of adsorbed and non-adsorbed PCE on its dispersion properties in different water-to-binder ratio system are discussed and analyzed. The adsorption amount of PCE increases with its increased carboxylate density and length of main chain as well as molecular mass, while its steric repulsion depends on the side chain length that affects the adsorption conformation in a large degree. In a constant water-to-binder ratio system, more adsorbed PCE is beneficial to the enhancement of dispersion capability paste. Apart from that adsorbed PCE, the non-adsorbed PCE with appropriate molecular mass also plays a lubrication and favors to the decrease of frictions between particles, resulting in the improvement of workability of paste at a low water-to-binder ratio. This article can provide a better understanding on the adsorbed behaviors of PCE and a theoretical basis on the improvement of dispersion capability of PCE and the design of PCE used for low water-to-binder system.
... Comparable results were also reported by Plank and Bernhard in their work on α-Allyl-ω-methoxypolyethylene glycol-maleic anhydride copolymer adsorption onto cement. They noticed a rapid decrease in polymer adsorption with increasing sidechain length, which was attributed to the higher surface occupancy of the larger side group leading to hindrance in adsorption [37]. We observed a similar trend in our related work, where umbrella sampling free adsorption energy analysis using molecular dynamic (MD) simulations also revealed that HPAM has higher adsorption-free energy than SPAM [38]. ...
... Plank and Bernhard also noticed similar zeta potential behaviour in their work, where the polymers with larger side chains brought about a more significant change in zeta potential despite having lower adsorbed amounts than polymers with smaller side chains. They attributed this phenomenon to the steric effect of the larger side chains moving the shear plane of the zeta potential further away from the positively charged particle surface, resulting in an apparent decrease in zeta potential [37]. Thus, the large, sulfonated side chain may move the shear plane of zeta potential slightly further away from the CaCO3 surface, thus imposing an apparent negative charge measurement on the instrument. ...
In this work, the consolidation of calcium carbonate (CaCO3) by polyacrylamide (PAM) of different molecular weights, charge densities, and functional groups was investigated via oscillatory rheology and unconfined compressive strength (UCS) analysis. Oscillatory rheology showed that the storage modulus G′ was approximately 10 times higher than the loss modulus G″, indicating a highly elastic CaCO3 sample upon consolidation via PAM. Both oscillatory rheology and UCS analysis exhibited similar trends, wherein the mechanical values (G′, G″, and UCS) first increased with increasing polymer dosage, until they reached a peak value (typically at 3 mgpol/gCaCO3), followed by a decrease in the mechanical values. This indicates that there is an optimum polymer dosage for the different PAM-CaCO3 colloidal systems, and that exceeding this value induces the re-stabilisation of the colloidal system, leading to a decreased degree of consolidation. Regarding the effect of the PAM molecular weight, the peak G’ and UCS values of CaCO3 consolidated by hydrolysed PAM (HPAM) of different molecular weights are very similar. This is likely due to the contour length of the HPAMs being either almost the same or longer than the average distance between two CaCO3 particles. The effect of the PAM charge density revealed that the peak G′ and UCS values decreased as the charge density of the PAM increased, while the optimum PAM dosage increased with decreasing PAM charge density. The higher likelihood of lower-charge PAM bridging between the particles contributes to higher elastic energy and mechanical strength. Finally, regarding the PAM functional group, CaCO3 consolidated by sulfonated polyacrylamide (SPAM) typically offers lower mechanical strength than that consolidated with HPAM. The bulky sulfonate side groups of SPAM interfere with the surface packing, reducing the number of polymers able to adsorb onto the surface and, eventually, reducing the degree of consolidation of CaCO3. The zeta potential of the PAM-CaCO3 samples became more negative with increasing PAM concentration due to the saturation of the particle surface. Good agreement between oscillatory rheology and UCS analysis could accelerate PAM screening for optimum CaCO3 consolidation.
... As shown in Figure 2-2, electrostatic repulsion takes place with the particles all negatively charged due to adsorption [142]. This mechanism is detected as the main dispersion mechanism when zeta potential becomes more negative after superplasticizer addition [149]. [150] Steric hindrance can take place by avoiding an overlapping of the adsorbed layers, or by protruding side chains of PCE into pore solution [147,151,152] (Figure 2-3). ...
... [150] Steric hindrance can take place by avoiding an overlapping of the adsorbed layers, or by protruding side chains of PCE into pore solution [147,151,152] (Figure 2-3). When zeta potential becomes less negative or even positive, steric hindrance is assumed to be the main dispersion mechanism of a superplasticizer polymer [149]. [150] State of the art -Superplasticizers and their mechanisms in cementitious systems ...
This thesis debutes a systematic study of the rheological behavior of cements blended with both metaphyllosilicates and calcined common clays. With their addition, the flow resistance, yield stress and viscosity of blended cement pastes increase in parts significantly as shown via rotational viscometer tests. The analysis of single-phase materials reveals the influence of mineralogical composition of raw clays, especially their concentration of kaolinite, different types of 2:1 phyllosilicates, and quartz. The correlation of rheological behavior with physical characteristics of metaphyllosilicates and calcined common clays, such as particle size, zeta potential, water demand, and surface area is evaluated critically.
The dispersion performance of a broad variety of superplasticizer (lignosulfonates, NSF polycondensate, polycarboxylate-based co-polymers (PCEs)) is determined via mini slump tests and rotational viscometer tests. The demand for superplasticizer is directly linked to the flow resistance of the respective reference mixture. It increases to different extents depending on the calcined clay added, its water demand, particle fineness, and negative zeta potential; the latter mainly resulting from kaolinite content. Regardless of their increased demand, the performance of superplasticizers in calcined clay blended cements is as efficient as it is in plain cements. In case of PCEs, a higher anionic charge density enables a better initial dispersion. All conventional macromonomers exhibit an overall good to excellent dispersion performance. Metamuscovite is the only phase that perturbs the performance of superplasticizers and is sensitive towards the type of superplasticizer.
The use of calcined clays can lead to rapid slump loss, which is stronger with the addition of conventional PCEs than with NSF polycondensate as time related mini slump tests and rheological tests show. The addition of lignosulfonates may limit this phenomenon, but often goes along with significant retardation effects. This thesis investigates one possible solution to prevent rapid slump loss, namely the introduction of hydroxyethyl methacrylate into the PCE polymer. Its decomposition into ethylene glycol and carboxyl groups in alkaline media leads to a later adsorption of the latter and can enable a subsequent dispersion. The study reveals the total phyllosilicate content in clay as well as the specific surface area of the calcined clay as decisive parameters for the functionality of this special type of polymer.
Complementing tests study the early hydration of calcined clay blended cements in the presence of superplasticizers via isothermal calorimetry, as well as in situ XRD and ultrasound method on selected samples. The early hydration kinetics depend mainly on the characteristics of the calcined clay as well as on the superplasticizer dosage. Overall, the retardation is minor in calcined clay blended cements. This is related to the increased surface area which favors the formation of early hydration products - despite the adsorption of superplasticizers onto binder particle surfaces. An enhanced ettringite formation of calcined clay blended cements enables an unhindered silicate hydration and transformation of ettringite to hemicarboaluminate, even in the presence of most superplasticizers.
This thesis reveals the suitability of a wide array of calcined common clays and their limitations as future SCM regarding their impact on rheological behavior in combination with the correct choice of superplasticizer. A fair assessment and a careful selection provided, their use can meet the high demand for sustainable cementitious materials and help improving the ecological footprint of modern concrete.
... Several studies reported that the non-neutralized solution of APEG PCEs is more effective as compared to MPEG PCEs. This excellent performance is attributed to its molecular "star shape" which is a consequence of the relatively low copolymerization tendency of the allyl ether radical resulting from resonance stabilization [35]. The possibility of bulk polymerization (which allows producing a PCE solution possessing reasonably low viscosity at up to 70 wt% solid content) and the high effectiveness of the acid form present the main advantages of APEG PCEs. ...
... It is worth noting that the affinity of the PCE polymer to the cement grains varies according to the chemical composition of the individual PCE (in particular the specific anionic charge amount resulting from the number of carboxylate groups and their repartition along the main chain in alternating or block mode, polydispersity in molecular structure also shows clear impact) [53]. Two examples of adsorption isotherms representative for a high-range water-reducing and a slump retaining PCE are presented in Fig. 8. PCE adsorption could be followed by zeta potential measurements (reliably only for side chains of <20 EO units) [35], and the adsorbed amount of PCEs can be quantified via the depletion method from the residual PCE concentration present in the filtrate using total organic carbon (TOC) measurement [54]. ...
2021 marks the 40th year since polycarboxylate superplasticizers (PCEs) have been invented by Nippon Shokubai company in Japan. This invention clearly represents a major breakthrough and milestone in modern concrete technology. In this review article, at first Dr. Hirata – the main inventor of PCE superplasticizers – reports on the history behind their invention and market entry. Thereafter, recent developments and innovations in PCE technology are presented. As of today, the market offers a wide range of chemically different PCE products, among them HPEG and IPEG PCEs have occupied the largest market share because of their superior cost-effectiveness. At this moment, novel types of PCEs including EPEG and GPEG PCEs are being introduced, thus enriching the family of vinyl ether (VPEG) superplasticizers. In spite of the huge success of PCEs, also challenges in specific applications such as their sensitivity towards clay contaminants or the viscous (“sticky”) flow behavior of concrete mixed at low w/c ratios became obvious and will be addressed. Furthermore, as the concrete industry currently undergoes a fundamental transition to low-carbon binders in order to reduce anthropogenic CO2 emission, PCE superplasticizers suitable for such low or zero clinker binders including calcined clay blended cements or alkali activated slags are being sought and the current state-of-the-art in this field will be discussed. Finally, the future perspectives of PCE technology in a dramatically changing industry are assessed and the pivotal role of PCEs in this mega transition faced by the construction industry will be pointed out.
... The highest priority in terms of modifying the structural components of the cement stone can be put on the use of superplasticizers, given that the main rheological parameter of the commercial concrete mixture is its placeability, while the consistency of the mix (P3 and P4) with a sufficiently low watercement ratio of up to 0.4 is possible only with chemical plasticization of the system (Berg et al., 2012;Nesvetaev et al., 2003;Plank & Sachsenhauser, 2006;Patil et al., 2016;Salamanova et al., 2015). ...
... According to numerous studies, APEG PCEs are more effective than MPEG PCEs in their non-neutralized form. The "star shape" of the substance's molecules, resulting from resonance stabilization's comparatively low propensity to copolymerize the allyl ether radical, is credited with this higher performance (Plank and Sachsenhauser, 2006). The two main benefits of APEG PCEs are their potential for bulk polymerization, which enables the creation of PCE solutions with relatively low viscosities at solid contents of up to 70%, and their high acid form efficacy. ...
Modern concrete frequently uses a variety of chemical admixtures, like setting time-retarding admixtures, viscosity-modifying admixtures (VMA), and superplasticizers (SPs). These chemical admixtures greatly impact cement components like film-forming capacity, flowability, and film drying time. Currently, the market provides a broad variety of chemically distinct polycarboxylate (PCE) products; of these IPEG and HPEG PCEs have a wide market share due to their cost-effectiveness. New PCE types such as GPEG and EPEG PCEs are currently being introduced, which will expand the family of vinyl ether (VPEG) SPs. In summary, this study examines the chemistry, functionality, the interaction between the chemical structure of PCEs and their behavior with concrete and/or cement-based materials (CBM). The performance of concrete and/or CBM is significantly influenced by the chemical structure of PCE, along with their main chain, anchoring group, side chain, molecular weight, and structure. In conclusion, more precise quantitative micro-analytical methodologies and modelling tools are required to get a comprehensive grasp of the variables influencing the microstructure of concrete and to apply PCE SPs to create more durable concrete.
... Compared to MPEG PCE, which is less efficient in reducing viscosity, the non-neutralizing solution of APEG PCE is more effective. This is mainly attributed to the "star-shaped" molecular structure of APEG PCE, which is the result of the relatively low tendency of copolymerization of allyl ether radicals due to resonance stabilization [87]. Among all PCEs, HPEG PCE shows excellent water reduction and the highest dosage effectiveness at a competitive price. ...
... This was an expected result, since SPAM possessed sulfonate side groups, which are bulkier than the carboxylate groups, hence interfering with the surface adsorption [33]. Similar findings were reported by Plank and Sachsenhauser [61], where they mentioned that the lower adsorption of polymers with larger side chains is due to higher surface occupancy of the larger side group. The range of steric repulsion distance of both F3330 and AN125 detected by the AFM was very similar. ...
This study investigates the interaction of polyacrylamide (PAM) of different functional groups (sulfonate vs. carboxylate) and charge density (30% hydrolysed vs. 10% hydrolysed) with calcium carbonate (CaCO3) via atomic force microscopy (AFM) and partly via molecular dynamic (MD) simulations. The PAM used were F3330 (30% hydrolysed), AN125 (25% sulfonated), and AN910 (% hydrolysed). A total of 100 ppm of PAMs was prepared in 0.1% NaCl, 3% NaCl, and 4.36% NaNO3 to be employed in AFM experiments, while oligomeric models (30 repeating units) of hydrolysed polyacrylamide (HPAM), sulfonated polyacrylamide (SPAM), and neutral PAM (NPAM) were studied on a model calcite surface on MD simulations. AFM analysis indicated that F3330 has a higher average adhesion and interaction energy with CaCO3 than AN125 due to the bulky sulfonate side group of AN125 interfering with SPAM adsorption. Steric repulsion of both PAMs was similar due to their comparable molecular weights and densities of the charged group. In contrast, AN910 showed lower average adhesion and interaction energy, along with slightly longer steric repulsion with calcite than F3330, suggesting AN910 adopts more loops and tails than the slightly flatter F3330 configuration. An increase in salt concentration from 0.1% to 3% NaCl saw a reduction in adhesion and interaction energy for F3330 and AN125 due to charge screening, while AN910 saw an increase, and these values increased further at 4.36% NaNO3. MD simulations revealed that the salt ions in the system formed salt bridges between PAM and calcite, indicating that the adhesion and interaction energy observed from AFM are likely to be the net balance between PAM charged group screening and salt bridging by the salt ions present. Salt ions with larger bare radii and smaller hydrated radii were shown to form stronger salt bridges.
... The compressive strength values obtained for these samples, measured after 3, 7, and 28 curing days, were 50, 58.8, and 66 MPa, respectively. Generally, PCEs with high zeta potential exhibit good compressive strength values, which in turn are correlated with better adsorption of superplasticizer molecules [36]. The aim of this work is to study the compatibility of a polymer with silica fume in HPC. ...
The incorporation of polycarboxylate ether superplasticizer (PCE)-type polymers and silica fume (SF) in high-performance concretes (HPC) leads to remarkable rheological and mechanical improvements. In the fresh state, PCEs are adsorbed on cement particles and dispersants, promoting the workability of the concrete. Silica fume enables very well-compacted concrete to be obtained, which is characterized by high mechanical parameters in its hardened state. Some PCEs are incompatible with silica fume, which can result in slump loss and poor rheological behavior. The main objective of this research is to study the influence of three types of PCEs, which all have different molecular architectures, on the rheological and mechanical behavior of high-performance concretes containing 10% SF as a partial replacement of cement. The results show that the carboxylic density of PCE has an influence on its compatibility with SF.
... The compressive strength values obtained for these samples, measured after 3, 7 and 28 curing days, were 12 50, 58.8 and 66 MPa, respectively. Generally, PCEs with high zeta potential exhibit good compressive strength values, which in turn are correlated with a better adsorption of superplasticizer molecules [36]. ...
The incorporation of polycarboxylate ether superplasticizer (PCE) type polymer and silica fume (SF) in high-performance concretes (HPC) leads to the achievement of remarkable rheological and mechanical improvements. In the fresh state, PCEs are adsorbed on cement particles and dispersants, in turn promoting the workability of the concrete. Silica fume enables a very well compacted concrete to be obtained, which is characterized by high mechanical parameters in its hardened state. Some PCEs are incompatible with silica fume, which can result in the loss of slump and in poor rheological behavior. The main objective of the research is the study of the influence of three types of PCEs, which all have a different molecular architecture, on the rheological and mechanical behavior of high-performance concretes containing 10% of SF as a partial replacement of cement. The results show that the carboxylic density of PCE has an influence on its compatibility with SF.
... Previous research has shown the compatibility and the dispersive effectiveness of PCE type superplasticizers with calcined clay blended cements. They are known to provide desirable workability improvements and water-reducing abilities compared to other generations of superplasticizers [17]. Although numerous research has evaluated the use of dispersing agents in terms of rheology or compatibility with clay minerologies, barely any study has been conducted on studying the use of superplasticizers as a way to influence pozzolanicity. ...
The declining availability of promising supplementary cementitious materials (SCMs) in the recent past, such as fly ash and ggbfs, has opened new recesses in the domain of alternative binders. It is therefore imperative and urgent to develop more lasting and consistent alternatives, for addressing the need to diminish the carbon footprint of cement production. The potentialities of utilizing mixed layer excavated clays that are obtained as by-products of repair and construction activities, as possible SCMs have been well established in past literature. However, understanding the relationship between particle deagglomeration and pozzolanic properties via non-energy-intensive methods, is still an open niche yet to be fully explored. This study is an attempt at understanding the use of dispersive mechanisms such as super-plasticizers and storage in suspension to possibly impact surface charges of clay agglomerates and eventually, their reactivity. It is found that dispersive agents added to ground clay particles can enhance pozzolanicity of mixed layer clay particles and thereby reduce dependence on energy intensive methods such as grinding for activation.KeywordsSCMrheologyreactivitymixed layer claysexcavated clays
... Основний ланцюг таких комбінованих полімерів забезпечує адсорбцію головним чином завдяки електростатичній взаємодії з поверхнею і несе функціональні групи карбонових кислот. За хімічною природою основний ланцюг може бути представлений акриловою (CH 2 =CH-COOH), метакриловою (CH 2 =C(CH 3 )COOH), малеїновою (HOOC-CH=CH-COOH) кислотами, радикалами вінілу (CH 2 =CH-) або алільною групою (CH 2 =CH-CH 2 -) [254,266,281,308,343]. ...
В монографії наведено результати досліджень, спрямованих
на визначення критеріїв вибору і закономірностей впливу ефективних
пластифікуючих добавок та отриманих на їх основі багатофункціональних
комплексних добавок на процеси структуроутворення лужних цементів
системи Na2O–CaO–Al2O3–SiO2–H2O. Запропоновано механізм пластифікуючої
і модифікуючої дії складних та простих поліефірів, етоксильованих і
багатоатомних спиртів, карбонових кислот та їх солей, а також амонієвих
сполук, лігносульфонатів і поліорганогідридсилоксанів. Розроблено науково-
методичні основи проектування складів бетонів і розчинів на основі цементних
систем різного ступеня розрідження. Запропоновано принципи вибору і
систематизацію поверхнево-активних речовин для управління властивостями
композиційних матеріалів на основі лужних цементів. Наведено технологічні
основи і обґрунтовано техніко-економічну ефективність хімічної модифікації
композиційних матеріалів.
Монографія буде корисною для студентів, аспірантів, докторантів
і наукових співробітників, які займаються дослідженнями та виробництвом
цементів, будівельних розчинів і бетонів.
... This reason may be a high concentration from Ca 2þ on the AAS O-H stretching -OH -OH 1,646 Fig. 12. GPC results of PFS superplasticizer: (a) with addition of NAS; and (b) without addition of NAS. This may be because the long side chains of PCb SP can shift the shear plane between the stern layer (fixed layer in which oppositely charged ions surround the charges on the particle surface) and the diffuse layer (the area that contains positive and negative ions beyond the stern layer "charge cloud") to a greater distance from the AAS surface (Plank and Sachsenhauser 2006). At this greater distance, the zeta potential curve shifted to the isoelectric point (zeta potential equals zero), decreasing the negative value of zeta potential (Habbaba and Plank 2010). ...
The current study aims to construct a synthetic polymer (or family of polymers) with superior plasticizing properties in a highly alkaline medium. An invented laboratory-prepared superplasticizer (SP), namely phenol-formaldehyde sulfonilate (PFS), was synthesized, and its performance was measured against two types of commercial superplasticizers [naphthalene-based (Nb) and polycarboxylate-based (PCb)]. Fourier transform infrared (FTIR) and gel permeation chromatography (GPC) tests were performed to verify the admixture's stability in a highly alkaline medium. The interaction between different SPs and alkali-activated slag (AAS) surface was investigated via zeta potential and adsorption measurements. The flowability, setting time, and compressive strength developments were evaluated for AAS mixes. The hydration products' morphologies and phase compositions were studied using scanning electron microscope (SEM) and X-ray diffraction (XRD). The results reveal that the prepared PFS SP has a high stability against the highly alkaline medium. The dispersing efficiency of PFS SP resulted from the highly negative zeta potential value (−49.8 mV) compared with Nb (−41.5 mV) and PCb (−15.8 mV), as well as its high adsorption percentage as PFS, Nb, and PCb adsorbed by 18.5%, 9.2%, and 3.7%, respectively. The PFS SP enhanced the physico-mechanical properties for AAS because it combined several advantages at the same time compared to commercial superplasticizers; for instance, AAS pastes admixed with PFS SP have superior workability, acceptable setting time, and high early strength.
... PCE adsorption can be tracked experimentally via zeta potential measurements (reliably only for side chains of <20 EO units) [34] and quantification is possible via total organic carbon (TOC) analysis of the amount of unadsorbed PCE polymer. Other methods such as HPLC and SEC can also be applied. ...
At first, a critical overview of current polycarboxylate (PCE) technology including the chemistry of different kinds of PCEs, characteristic molecular properties, their interaction with cement and application aspects are discussed. In the following, the classification and chemistry of clays and clay minerals is presented. In addition, the interaction of PCE superplasticizers with clay minerals and in particular the very harmful chemical sorption of PCE by montmorillonite (MMT) clay which causes a substantial reduction or even complete loss of PCE dispersing effectiveness are introduced. Possible mitigation strategies from the open literature to remedy the negative effects of clay are outlined. Over the last years, calcined clays have gained substantial attention as supplementary cementitious material (SCM). This paper also covers their chemistry and properties as well as their different interaction mode with PCE superplasticizers. Finally, future concepts in PCE technology regarding enhanced clay tolerance and enhancement of the fluidity of Limestone-Calcined Clay Cement (LC³) are proposed.
... However, the Marsh funnel flow of the mixture containing this admixture was low. The fact that the admixture has a short main chain causes the amount of anionic functional groups on the main chain to decrease and, consequently, a weakening of the electrostatic effect (Ferrari et al., 2011;Mardani-Aghabaglou et al., 2013;Peng et al., 2013;Plank and Sachsenhauser, 2006;Qiu et al., 2011;Wang et al., 2018). ...
1 2 3 4 In this study, the effect of main and side chain lengths of polycarboxylate ether-based high-range water-reducing admixtures (WRAs) on the fresh properties, compressive strength and water absorption of cementitious systems containing 0, 15, 30 and 45 wt% fly ash was investigated. For this purpose, three WRAs with the same molecular weight but different chain lengths were produced. According to the test results, the flowability of the paste and mortars was negatively affected when the length of the main and side chains of the admixture was longer or shorter than a certain value. This adverse effect is thought to arise from weakening of the adsorption of the admixture with an increase in its chain lengths. However, when the main and side chain lengths of the admixture were shorter or longer than a certain value, the time-dependent flow properties of the mortar mixtures improved. The main and side chain lengths of the WRAs did not have a significant effect on the compressive strength and water absorption capacity of the mortar mixtures. However, irrespective of the admixture characteristics, with an increase in fly ash substitution, the flow and time-dependent flow properties of the mixtures were negatively affected but their water absorption decreased.
... 6,16,19,20 In addition, the dense polymer film layers on the cement particles may be destroyed due to steric effect when the side chains are longer than a certain value. 21,22 As it was reported earlier by several researchers, in the water-reducing admixture-bearing cementitious systems, the admixture adsorbed on the cement particles improves the fluidity, while the free polymer in the solution improves the workability retention of the system. [22][23][24][25][26] It was demonstrated that the ability of HRWRA to be adsorbed on cement particles improves by reducing interlacing of polymer chains in the solution with shortening of its side chains. ...
The effect of the length of main and side chains of high-range water-reducing admixture (HRWRA) on some fresh and hardened properties of self-consolidating concretes (SCCs) was researched. For this purpose, three polycarboxylate ether-based HRWRA admixtures with different side and main chain lengths were synthesized. For a given SCC slump-flow value, the admixture requirement was the least when the admixture having a medium side chain length (2400 g/mol) was used. Moreover, decreasing the main chain length of the admixture improved the fresh properties’ retention of SCC. The fact was attributed to the increase in free polymer in the mixture by increasing the side chain length of the admixture. The main and side chain lengths of the HRWRA admixture were significantly influential on the early compressive strength of SCC mixtures but had a negligible effect on their 7- and 28-day compressive strength and 28-day water absorption.
... First, it should be noted that PCE molecules are easier to stretch instead of being squeezed by particles in a low concentration suspension, the -COOgroups in FA-PCE and IA-PCE are isolated distributed on the main chain, while-COOgroups in MAH-PCE appeared as pairs on the main chain. Besides, these three "star-like" PCEs, adsorbed on the surface of particles through "tail" adsorption, that is, the main chain is perpendicular to the cement surface [48]. In this case, some of -COOgroups in FA-PCE and IA-PCE will be exposed on the surface of the polymer layer, while a few of -COOgroups in MAH-PCE will be exposed. ...
Polycarboxylate ether (PCE) superplasticizers with three different anchoring groups were synthesized by copolymerizing allyl polyoxyethylene ether with trans-butadiene (FA), cis-butenedioic anhydride (MAH), and itaconic acid (IA), respectively. The interactions between PCEs and cementitious materials were revealed by adsorption properties, Ca²⁺ binding capacity of PCE, and zeta-potential of paste. The effects of anchoring groups in PCEs on the flowability and rheological properties of cementitious pastes were studied. Results indicated that the density and local configuration of –COO– groups in PCEs significantly affect their adsorption behavior and dispersibility in cementitious pastes. Most of the –COO– groups are isolated on the backbone of FA-PCE, while for the MAH-PCE, only pairs of –COO– groups present the backbone. All the –COO– groups directly connect to the main chains in FA- and MAH- PCEs, whereas half of the –COO– groups in IA-PCE indirectly connect to the main chains through hydrophobic methylene, which has a potential to curl and reduce its “accessible” –COO– groups. FA-PCE with a large specific charge density exhibit excellent flowability and rheological properties in cementitious pastes.
... Changes in ZP indicate the adsorption of (super)plasticizers onto binder components on the one hand and the formation of hydration phases on the other. When the ZP becomes less negative or even positive, steric hinderance is assumed to be the main dispersion mechanism of a superplasticizer polymer, like it is known for PCE [62]. An absolute differentiation between adsorption-related and hydration-related change of ZP is hence impossible, but the trend in ZP is used for comparison in combination with rheological measurements and calorimetric studies. ...
Workability of cementitious systems is often limited when blending them with calcined clays. The first part of the study compares for the first time results of zeta potential measurements on both, raw/calcined clays in water and synthetic cement pore solution as well as on a Portland limestone cement replaced by 30 wt% of calcined clay. This helps to identify critical parameters that reduce the workability, also over time. The second part evaluates the time-related flow behavior via mini slump test and rotational viscometer and, by using isothermal calorimetry, early hydration kinetics of different calcined common clays with two polycarboxylate-based (PCE) superplasticizers. The results reveal a high negative zeta potential resulting from high kaolinite content. A large specific surface area enhances floc-culation and nucleation, while an increasing amount of phyllosilicates and soluble aluminum ions accelerate ettringite formation also with the addition of PCE. Tailor-made PCE, however, can compensate rapid loss in flowability and enable a sufficient workability period without affecting early strength development significantly for most calcined clay blended systems.
... Новые пластифицирующие добавки созданы с учетом состава вяжущего материала, с разным соотношением электростатического и стерического фактора в макромолекуле, в зависимости от условий синтеза. Согласно предположению автора указанной работы [22] молекулы поликарбоксилатного суперпластификатора с высокой анионной плотностью заряда показывают лучшую адсорбцию и хороший диспергирующий эффект, в то время как сохраняемость таких систем может ухудшаться. ...
В статье рассмотрено одно из основных направлений развития наноинженерии строительных материалов. Модификация композиционных материалов на основе цемента поликарбоксилатами. Рассмотрены особенности механизма действия поликарбоксилатных суперпластификаторов на свойства бетона в сравнении с традиционными пластифицирующими добавками на основе сульфированных нафталини или меламинформальдегидных соединений. Представлены перспективы развития наноинженерии в модификации материалов на основе цемента.
The article discusses one of the main directions of development of nanoengineering of building materials. Modification of cement-based composite materials with polycarboxylates. The features of the mechanism of action of polycarboxylate superplasticizers on the properties of concrete are considered in comparison with traditional plasticizing additives based on sulfonated naphthalene- and or melamine-formaldehyde compounds. Prospects for the development of nanoengineering in the modification of cement-based materials are presented.
... A PCE in a solid state prepared by a simple technique is expected to be obtained. In this manner, it was reported that a type of α-allyl-ω-methoxy polyethylene glycol-maleic anhydride PCE [1], a PCE copolymerized by allyl ether and maleic anhydride [2] or by methoxy polyethylene glycol (MPEG), maleic anhydride and sodium acetate [3] were synthesized in a non-aqueous system. Liu et al [4] reported some interesting results regarding the solid PCE prepared by non-solvent polymerization in one-step method. ...
A novel polycarboxylate superplasticizer (PCE) with energy saving preparation was elaborately designed and synthesized by using acrylic acid (AA), hydroxypropyl acrylate (HPA) and isopentenyl polyethylene glycol (IPEG) as monomers. To investigate the effects of the preparation method on the effectiveness of PCE, the PCEs were prepared from energy-saving method and common method respectively, and the hydration heat evolutions of the cement pastes containing these PCEs were comparatively probed. Furthermore, the working mechanisms of the PCEs by different preparations were identified via adsorption behavior, adsorption kinetic and Zeta potential of the PCE on cement surfaces. The results showed that, this novel PCE prepared in an energy saving manner can significantly prolong the hydration process and present a stronger adsorption capacity. In addition, the adsorption of this PCE on cement surface exhibited a characteristic of pseudo first order kinetic equation model. The evaluation in energy conservation showed that, this energy saving preparation can save 1.548×10 ⁴ kJ per 10 ton production. The aim of this study is to provide a new avenue to synthesize a PCE with economical method which achieves energy-saving preparation. Due to the indispensable application in construction industry, the innovations from this study contribute to the low energy-consumption production and high eco-effectiveness of the novel PCE, which has potential applications in low-emission building materials.
... To investigate, at first the electrical charge of the CC particles dispersed in DI water, 0.03 M NaOH (pH = 12.5) and SCPS was captured by zeta potential measurements. These experiments were devised to elucidate the effects of different ionization of the surface resulting from different pH values and ion concentrations in the pore solution (Plank and Sachsenhauser, 2006). Fig. 6 displays the zeta potentials of all meta clays as a function of the dispersing fluid. ...
Polycarboxylate (PCE) comb polymers were selected as potential dispersant for suspensions prepared from individual calcined clay samples. It was anticipated that mechanistically their dispersing effect relies on adsorption onto positively charged surfaces of the meta clays which was to be proven. Furthermore, the structural differences between two specifically selected PCE kinds were assumed to result in different dispersing performance.
Using spread flow tests, the dispersing effectiveness of the PCEs on four different meta clay samples (meta kaolin, meta muscovite, meta illite and meta montmorillonite) was assessed. Moreover, the surface chemistry of the meta clays dispersed in synthetic cement pore solution (SCPS) was captured via zeta potential and sorption measurements to elucidate the interaction of the superplasticizers with the calcined clay samples.
In accordance to common knowledge, the results confirmed the high water demand of calcined clays which made them asking for superplasticizers when used in mortar and concrete. It was found that the zeta potential (surface charge) of the meta clays initially was negative, but converted to positive via uptake of Ca²⁺ ions from the pore solution, especially in Ca²⁺-rich cementitious systems. Sorption measurements revealed that the PCE superplasticizers adsorbed onto these positively charged surfaces and thus achieved dispersion. The methallyl ether (HPEG) based PCE vastly outperformed the methacrylate ester (MPEG) based PCE. Surprisingly, meta illite could not be dispersed satisfactorily, in spite of high PCE adsorption. The results contribute to understand at a glance the dispersing mechanisms of PCE superplasticizers in naturally occurring calcined clays with various clay mineral compositions and to select the adequate superplasticizer easily.
... Thus, the adsorption amount of the admixture is reduced and the steric effect is weakened. In addition, Plank and Sachsenhauser (2006) and Wang et al. (2018) found that the polymer film layers formed on the cement surface are destroyed due to the steric effect of long side chains. This causes the adsorption amount of the admixture to decrease. ...
In this study, the effect was investigated of side chain length changes of polycarboxylate-ether-based high-range water-reducing (HRWR) admixture on fresh properties, compressive strength, and water adsorption capacity of cementitious systems. For this aim, three HRWR admixtures having same raw materials, anionic/nonionic group ratio, free nonionic group content, and main chain length but different side chain length and molecular weight were synthesized. The effect was investigated of the mentioned admixtures on the properties of mixtures containing 0%, 15%, 30%, and 45% of fly ash. According to the test results, regardless of fly ash utilization ratio, the flowability of the mixtures was positively affected with the increase of the water-reducing admixture side chain length to a certain value. However, utilization of admixtures having the longer side chain length than a certain value adversely affected the flow properties of the mixtures. It is thought that this situation is due to the reduction of the admixture efficiency (steric effect) by increasing the possibility of intertwining of polymers of admixture having higher side chain length. The admixture with 2,400 g=mol of side chain molecular weight (length) showed the best performance in terms of fresh properties. The change of HRWR admixture properties had no significant effect on the strength and water adsorption capacity of the mixtures. Moreover, regardless of HRWR admixture properties, the time-dependent flowability of the mixtures was adversely affected and the water adsorption capacity was decreased with the utilization of fly ash. This effect was more pronounced with increasing replacement ratio of fly ash.
... the adsorption of the admixture and its steric effect [26,33,35]. In addition, the destruction of the polymer film formed on the cement particles and reduction in the steric hindrance originated from very long side chains further reduce the adsorption of the admixture [36,37]. Thus, irrespective of the admixture dosage, owing to its longer side chain, PCE-SC3000 exhibited a larger Marsh flow time than that of PCE-SC2400. ...
Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures, most previous reports on the cement-admixture compatibility did not provide sufficient information on the structure of the admixture. Hence, the evaluation and generalization of the reports on the cement-admixture compatibility are challenging. In this study, three different polycarboxylate-ether-based water-reducing admixtures with the same free nonionic content, anionic/nonionic molar ratio, and main chain length and different side chain lengths were produced. The compatibility of these admixtures with a CEM I 42.5 R-type cement was investigated. In addition, an analysis of variance was performed on the experiment results to evaluate the contributions of the admixture type, admixture/cement ratio, and elapsing time to the Marsh funnel flow time, mini-slump, slump flow, and compressive strength. The water-reducing admixtures having long or short side chains reduced the initial flow characteristics of the cementitious systems. However, the admixture having the shortest side chain was better with regard to flow retention. The side chain length of the admixture did not have significant effects on the compressive strength and water absorption capacity of the mortar mixtures and mini-slump performances of the cement paste mixtures. Regarding the behaviors of the admixtures in the cementitious systems, an optimal admixture side chain molecular weight is proposed.
Concretes containing dispersed fillers, reactive rock powders, microsilica and micro-hydrated kaolins are the object of research. The structural topology of such materials is predetermined by the activity of the dispersed filler. The unstable nature of the disperse systems, due to the high free surface energy, was used to increase the adhesion of cement to stone materials. Directional control of structure formation of reactive powder concretes is achieved by triboelectrification providing creation of transition layer on the surface of mineral material which interacts well with both cement and mineral substrate. An experimental research method based on a laboratory apparatus of a vortex layer is presented, which allows to form a triboelectric effect on the surface of fine-grained fillers. To break the aggregating effect of electromagnetic forces at the first stage of preparation of cement mortar for mixing cement with microfillers used energy-saturated high-speed mixers, and at the second stage for mixing cement composition with sand used traditional fillers.
The geochemical processes of polyphosphates (poly-Ps) are important for phosphorus (P) management and environmental protection. Water-soluble ammonium polyphosphate (APP) containing various P species has been increasingly used as an alternative P-fertilizer. The various P species coexistence and the chelation of poly-Ps with mental would trigger the P's competitive adsorption and affect the APP's adsorption intensity on goethite, compared to single orthophosphate (P1). P adsorption behaviors of APP1 with two P species and APP2 with seven P species on goethite were investigated via batch experiments in comparison to the traditional P-fertilizer of mono-ammonium phosphate (MAP). Co-adsorption of P1 and pyrophosphate (P2) on goethite was investigated by molecular dynamics (MD) simulation. The more Fe³⁺ dissolved from goethite as a bridge due to the chelation of poly-Ps in APP and contributed to the stronger APP adsorption on goethite compared with MAP. Ion chromatography and spectral analysis showed P1 and P2 in APP were mainly adsorbed by goethite via mainly forming bidentate complexes. The goethite preferentially adsorbed P1 at lower APP concentration but increased the poly-Ps’ adsorption at higher APP concentration. MD simulation showed that electrostatic interaction and hydrogen bonds played a key role in water-phosphates-goethite systems. The P1 pre-adsorbed on goethite could be replaced by P2 at high P2 concentration. The results develop new insights regarding the selective adsorption of various P species coexistence in goethite-rich environments.
The incorporation of polycarboxylate superplasticizers may increase the risk of shrinkage cracking of cement-based materials. Co-adding shrinkage-reducing admixtures (SRAs) may decrease the compressive strength or arise the incompatibility problem. Designing a novel superplasticizer with excellent shrinkage-reducing function by modifying molecular structures of polycarboxylate superplasticizers can be a promising approach.
This study aims to synthesize a novel shrinkage-reducing polycarboxylate superplasticizer (SR-PCA) possessing shrinkage-reducing and water-reducing functions and to investigate its performance and working mechanisms in cementitious systems. The results indicate that SR-PCA improves the fluidity of cement paste and has a distinguished fluidity retention capability. SR-PCA prolongs the cement hydration induction period, hinders the nucleation and growth of C-S-H in the acceleration period, while enhances hydration degree and refines the pore structure at later ages. Moreover, it can also be deduced that most PCA adsorbs on the cement surfaces, however, SR-PCA is mainly in the pore solution. The shrinkage-reducing mechanism of SR-PCA in cement-based materials is attributed to lowering the surface tension of the pore solution, due to the presence of the unreacted esterification macromonomers (AA-C4-PE-600) and the unadsorbed SR-PCA molecular.
Polycarboxylate ether (PCE) superplasticizers with different molecular structure were synthesized by copolymerizing macro-monomer with cis-butenedioic anhydride (MAH) and trans-1,2-ethenedicarboxylic acid (FA). Gel permeation chromatography, specific charge density, Fourier transform infrared spectroscopy, ¹H and ¹³C nuclear magnetic resonance were used to characterize these co-polymers. Their Ca²⁺ binding capacity, adsorption behaviors, retardation effects and dispersion efficiency were investigated by the calcium-ion selective electrode, total organic carbon, X-ray Photoelectron Spectroscopy, zeta potential, calorimetry measurements, mini-cone and rheological tests. Results indicated that PCE containing more FA possesses the higher density of –COO– groups, due to the higher reactivity of FA than MAH. The high density of –COO– groups in PCEs significantly affects their adsorption behaviors, retardation, and dispersion of cement pastes. Intermolecular chelation between –COO– groups and Ca²⁺ is dominated for FA-PCE, while the main coordination modes between –COO– in MAH-PCE and Ca²⁺ are intramolecular chelation owing to more adjacently distributed –COO– groups. FA-PCE exhibits larger adsorption amount and thicker adsorption layer compared with MAH-PCE. Hence, the FA-PCE demonstrated stronger dispersion efficiency, with which the cement pastes showed excellent flowability and rheological properties, correspondingly.
Previously, it was shown that zeta potential could be used as a metric to determine friction reducer (FR) performance. Specifically, the extent of and how quickly the FR reaches peak friction reduction in source water. A correlation postulated from the previous work is zeta potentials relationship to an FR's stability during mechanical or chemical degradation. In other words, can zeta potential be used as a metric to determine the extent of polymer breaking and can this relationship be translated to regained conductivity? This paper describes a laboratory study of zeta potential measurements to track breaker reaction rates, stability of broken polymer dispersions, and the relationship between chemical degradation of FRs and regained conductivity.
The approach of this investigation involves measuring zeta potential of frac fluids formulated using anionic and cationic FRs with varying types and concentrations of breakers at different temperatures and times. These metrics are then correlated with regain conductivity. A quantitative relationship exists between zeta potential, fluid rheology, and regain conductivity. Zeta potential evaluation of degraded FR's in frac fluids correlate to performance in regain conductivity testing. These measurements can expedite the selection of chemical breakers with respect to performance. Zeta potential measurements of degraded FR are indicative of broken FR dispersion stability which has impact on regain conductivity. Tracking behavior of cationic FR's using zeta potential reveals the materials can become anionic with time and temperature and become susceptible to agglomeration with iron. Zeta potential measurements can be used during a chemical breaker selection process as a viable supplement to industry standard tests for assessing the comparative effectiveness of chemical breakers in frac fluids.
To explain the incompatibility of some superplasticisers with class F fly ash, the effectiveness and mechanisms of superplasticisers based on lignosulfonate (LS), polynaphthalene (PNS) and polycarboxylates (PCE-1 and PCE-2) in dispersing the fly ash pastes were studied. The most effective superplasticisers, PCEs (PCE-1 and PCE-2), produced almost no additional electrostatic repulsion, are adsorbed in low amounts, and exhibited negligible adsorbed layer thickness. It is suggested that the excellent dispersing abilities of PCEs rely on the molecules remaining in the liquid phases of the pastes. For the inefficacy of LS and PNS, the absorption of molecules and bridging flocculation are the most likely causes. Superplasticiser molecules that entered the fly ash through the pores on the fly ash surface lost their dispersing abilities. The highly negatively charged LS and PNS can attract several fly ash particles to form the bridging flocculation, which reduced the dispersion of the fly ash pastes.
In this paper, using maleic anhydride (MA), allyl polyethylene glycol (AP), methyl allyl sulfonate (SM) as monomer and ammonia persulfate (KPA) as initiator, a polyether high-performance water-reducing agent for polyglycolic acid (PR) on good compatibility in sulphoaluminate cement (SAC) was synthesized by solution polymerization and orthogonal design. And the effects of various factors (reaction time, branched length and density of PR etc.) on the performance of PR were also studied. Results show that the optimum formula was as follows: the polymerization degree of AP was 56, the mass molar ratio of three monomers was n (MA): n (AP): n (SM) = 3:2:1, the amount of AP accounted for 9% of the total molar content of monomer, the reaction temperature was 65 °C, and the reaction time was 5 h.
Представлены результаты разработки высококачественных бетонов линейки классов от В7,5 до В30 с использованием местных сырьевых материалов и суперпластификатора на основе эфиров поликарбоксилатов. С использованием добавки MasterPozzolith 3150W проведены исследования по изучению динамики набора прочности, жизнеспособности, подвижности и склонности к седиментации бетонной смести, что благоприятно отразится на перекачиваемости и формовании конструкций.
The results of the development of high-quality concretes of a line of classes from B7.5 to B30 using local raw materials and a superplasticizer based on polycarboxylate ethers are presented. Using the additive MasterPozzolith 3150W, studies have been carried out to study the dynamics of strength gain, viability, mobility and the tendency to sedimentation of concrete sweep, which will have a beneficial effect on the pumpability and formation of structures.
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.
Polyether macromonomers have shown diversified structures recently. In this work, a series of polycarboxylate superplasticizers (PCEs) were synthesized via copolymerization using a novel macromonomer, ethylene–glycol monovinyl polyethylene glycol (EPEG). The molecular structures were modified by varying the side chain length, carboxylate density and integrating sulfonic group. The synthesis reaction of PCEs with high reaction conversion ratio was achieved through rapid reaction(20–30 min) at low temperature (5-20℃). The fluidity of PCEs, the rheological parameters and the compressive strength of mortar were measured. The adsorption behavior and zeta potential of the cement particles were also measured. Results have shown that PCEs with short side chain and high carboxylate density had high adsorption ability, high dispersion capacity in mortar. In addition, PCEs with sulfonic group had increased adsorption amount on the cement surface. These results could allow further progress in the application of EPEG macromonomer.
Graphene oxide (GO) is a promising candidate for reinforcing cement composites due to its prominent mechanical properties and good dispersibility in water. However, the severe agglomeration of GO nanosheets in the Ca2+ ion loaded environment of a freshly mixed cement composite is the main obstacle against the mentioned goal. Recent studies, based on the SEM images, have shown that the incorporation of pozzolans can ameliorate the GO agglomeration in cement matrix. Considering the fact that, for identifying the GO dispersion in cement matrix, SEM characterization is not preferred due to the hydrated cement matrix complexity and presence of small dosages of GO, this research has investigated the potential of Metakaolin (MK) as a highly reactive pozzolan against GO agglomeration in the non-hydrated environment of simulated cement pore solution (SCPS) for different MK/GO weight ratios. Additionally, the interaction between MK and GO in water is evaluated through different characterization methods. Visual investigation and UV-vis spectroscopy revealed that there should be a probable interaction between MK particles and GO nanosheets in water which was interpreted by Lewis acid–base interaction and further examined by FTIR spectroscopy. Moreover, the zeta potential measurements indicated that the increase in MK/GO weight ratio could lead to higher adsorption of GO on the surface of MK particles which was confirmed by the particle size analysis. Almost all of the conducted experiments on the MK–GO hybrid in simulated cement pore solution showed that different dosages of MK particles were incapable of preventing GO agglomeration; thus, despite the proposed mechanisms in previous studies, MK cannot effectively restrict the unfavorable effects of Ca2+ ions on GO dispersion in SCPS and analogously in the hydrating cement matrix.
With the rapid development of the construction industry, it is necessary to synthesize environment-friendly functional polymers, especially when developing “green” construction industry types. Herein a novel solid-state polycarboxylate superplasticizer (PCE) with low energy-consumption was designed and synthesized. In industrial application, solid-state PCE has exhibited better cement paste fluidity and concrete slump compared to liquid-state PCE. A life cycle assessment (LCA) of the PCE synthesis, the packaging materials used, and the transportation of the PCE were conducted based on the ReCiPe method. The results indicated that liquid-state PCE has a far greater environmental impact at >60% than solid-state PCE, which is less significant at <40%. The inventory data that are associated with the production of the new polymer are disclosed for the first time to enrich the related database in this field. This study demonstrates the optimization of the state and synthesis technique of a functional polymer, improving the performance and lowering the environmental impacts involved in producing the polymer, while reducing the risks to human health and protecting the ecosystem at the same time.
The rheology and hydration properties of oil well cement paste at medium and low temperature are of great importance for cementing marine shallow formation. This paper studies the effect of one kind of polycarboxylate-based dispersant (PW1010) on the performance of oil well cement paste and compares it with sulfonated aldehyde-ketone condensation polymer dispersant (SAF). The influence of PW1010 and SAF on the rheological properties of oil well cement paste is investigated, and is analysed by adsorption isotherm and Zeta potential tests. The influence of PW1010 on the hydration of oil well cement is conducted by compressive strength measurements, isothermal calorimetry (ICC), X-ray diffraction (XRD), thermogravimetric analyzer (TGA), mercury intrusion porosimetry (MIP) and permeability. The results show that an oil well cement paste containing PW1010 has better rheological properties at medium and low temperature than that containing SAF, because PW1010 has comb-like structure, which provides stronger steric hindrance effect. Moreover, even though PW1010 delays the hydration of oil well cement, it increases the early-age compressive strength and reduces the permeability at medium and low temperature. This is mainly because PW1010 improves the dispersion of cement particles and reduces the porosity and large pores of the hardened cement. This study has important significance for ensuring the well cementing proceeding smoothly and improving cementing quality.
Graphene can not only toughen cement-based materials, but also give them sensing ability. However, the uniform dispersion of graphene in a cement matrix is the major problem in the fabrication process. Four polycarboxylate superplasticizers (PCEs) with different charge densities and side-chain lengths were synthesized and the effects of their microstructures on the dispersibility of graphene in deionized water and in solution in cement pores were examined by UV-Vis spectroscopy, dynamic light scattering and optical microscopy with a large depth of field. A mechanism for the dispersion of graphene in the two media was also proposed. In deionized water, PCEs with a higher charge density showed more electrostatic repulsion, which improved the graphene dispersion efficiency. Conversely,PCEs with a lower charge density and longer side-chains gave a lower graphene dispersion. In solution in the cement pores, however, a PCE with a high charge-density produced a low graphene dispersibility, due to a cross-linking Ca²⁺-bridging effect. This effect was insignificant in cement pores for a solution containing low charge-density PCEs. Moreover, it was found that PCEs with the longer side-chains produced the worst graphene dispersion efficiency in both media. Overall, PCEs with a low charge density and relatively short side chains are more suitable for the preparation of graphene-composited cement pastes.
A new method of polymer characterization, based on permeation studies using nanoscale pores, was recently proposed by Brochard and de Gennes. In the present paper, we study how this method, initially developped for star polymers can be extended to comb-like polymers.
Today, superplasticizers are often used as high-range water reducers, to make concrete stronger by lowering the water-cement ratio. To achieve water reduction levels as high as 30 p.c., superplasticizers have to be used at high dosages ranging between 5 and 20 L/cu.m. Sometimes, however, unexpected behavior was experienced with particular cement-superplasticizer combinations. The origin of these incompatibility problems has to be investigated in each particular case.
This paper summarizes the relation between the molecular structure and the dispersion-adsorption mechanisms of 3 types of comb-type superplasticizers used in Japan. The action mechanisms of comb-type superplasticizers and the compatibility of cements and superplasticizers are influenced by the molecular structure of polymers such as copolymer components and the grafted chain length of poly (ethylene-oxide) (PEO). Many reports regarding concrete research have investigated the influence of comb-type superplasticizers on the fluidity of concrete and the production of selfcompacting concrete. However, many have not considered the effect of the molecular structures of comb-type superplasticizers. This paper should be useful for engineers and researches studying the action of comb-type superplasticizers in the production of concrete with comb-type superplasticizers, and for understanding any new properties of such concrete.
Different polycarboxylate polymers (PCPs) have been characterised and their microstructure investigated by size exclusion chromatography, 1H and 13C nuclear magnetic resonance spectroscopy. These polymers are comb-like with a sodium polymethacrylate backbone (PMAANa) on which poly(ethylene oxide) (PEO) chains are randomly grafted as shown by 13C NMR measurements. Since they are mostly used as superplasticisers in cementeous applications, their behaviour has been investigated at high pH in various salt solutions; average radii were determined at room temperature by static and dynamic light scattering and phase diagrams were determined as a function of temperature. We tried to evaluate the influence of different parameters (ion valence, cations, anions, PCP molecular weight, PEO length and grafting degree). A few experiments on homopolymers (PEO and PMAANa) have been equally performed in order to better understand the behaviour of PCPs in solution.
A series of polycarboxylic acid-based copolymers with block and graft groups of polyethlene oxide (PEO) chains was synthesized; effects of the different PEO chains on the fluidity, Zeta potential and adsorption in cement paste and performances of the copolymer in concrete were discussed. It was proved that properties of the copolymer were affected by the length and density of PEO graft and block chains, and that copolymers with some block PEO chains at a certain length and moral percent had good performances in the water-reducing capability and fluid-retaining ability. Experimental results indicated that this kind of copolymers could be used as a high-range water-reducer because of the effects of electrostatic repulsive force and steric hindrance; one of its applications was to produce high-flowing concrete by incorporating with mineral admixtures, such as fly ash, etc.
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