Fresh Emulsion Research Articles

Demulsification of steam-assisted gravity drainage (SAGD) emulsions under high temperature and high pressure: Effects of emulsion breaker and reverse emulsion breaker dosages

Effective treatment of complex emulsions formed during steam-assisted gravity drainage (SAGD) production is crucial for oil/water separation and subsequent processing. However, it remains challenging due to the complexity of SAGD emulsions, and there are only very limited studies on demulsification under simulated SAGD conditions. This study systematically characterized the comprehensive properties of a fresh field SAGD emulsion with about 84.6 % water and 15.4 % bitumen, and then achieved effective demulsification under a simulated SAGD condition at 135 °C and 60 psi via adding a poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) copolymer (as a model emulsion breaker or EB) combined with a branched polyethylenimine (PEI, as a model reverse emulsion breaker or REB) in a bench-scale bottle test setup. The effects of EB and REB dosages on the demulsification of the SAGD emulsion were evaluated based on the properties of the separated phases. Dynamic interfacial tension, zeta potential, and coalescence time were measured to reveal the demulsification mechanisms of EB and REB. The highly interface-active EB facilitated oil dehydration by displacing the natural interface-active species at the interfaces, disrupting the rigid interfacial films and promoting water droplet coalescence, while the cationic REB aided water de-oiling by neutralizing oil droplet surface charges, disrupting the rigid interfacial films and promoting the approach and coalescence of oil droplets in aqueous media. This work has improved the understanding of SAGD emulsion characteristics, the effects of EB and REB dosages on the demulsification performance, and the underlying demulsification mechanisms in SAGD operations. The results provide useful insights for developing effective and cost-efficient chemical approaches to address challenging emulsion issues in oil production.

Impact of injection pressures on properties, microscopic behavior, and microexplosions in biodiesel-emulsified fuel with biosurfactant

Water in biodiesel emulsified fuel improves air–fuel mixing and reduces combustion temperature, thereby lowering nitrogen oxides (NOx) emissions in diesel engines. Studies on emulsified fuel formation often use chemical surfactants. However, biosurfactants, which are natural and eco-friendly, remain unexplored. Additionally, the common-rail fuel injection system increases the pressure, temperature, and shear forces of emulsified fuel, thereby altering its properties and emulsified fuel droplet size and distribution. This study investigates the influence of biosurfactant concentration (1–3 %) and fuel injection system pressures (34.5, 69.0, and 103.5 MPa) on emulsified fuel properties. We utilised microscopy and a customized MATLAB image-processing code, along with a hot-plate technique and high-speed camera, to analyze droplet size distribution and micro-explosion behaviours. The findings demonstrate that increasing the concentrations of biosurfactants from 1 % to 3 % leads to an increase in the density by 1.07 % and viscosity by 10.81 %% but lower surface tension by 16.499 % in emulsified fuel, subsequently reducing particle size, delaying micro-explosion, and lowering peak temperature. On the other hand, all fuel properties undergo a notable reduction after passing through the fuel injection system, with increases in fuel pressure and injection through the nozzle’s orifices. In the case of fresh emulsion, with initial values of 841 kg/m3 density, 2.35 mm2/s viscosity, and 26.9 mN/m surface tension, these properties decreased to 829 kg/m3, 2.05 mm2/s, and 25.23 mN/m respectively, under an injection pressure of 103.5 MPa due to increasing the heating and shear forces generated by the fuel injection system while particle size distribution decreased from 2-4 µm to 1–2 µm from the fuel tank to the injector spray. The micro-explosion time of droplets from the fuel tank and injector spray operated at 34.5 MPa, 69.0 MPa, and 103.5 MPa was found to be 1.72 s, 1.97 s, 2.21 s, and 2.34 s, respectively. Correspondingly, the peak temperatures recorded were 272 °C, 277 °C, 282 °C, and 288 °C respectively.

Characteristics of virgin coconut oil (VCO) microencapsulation using O/W emulsification and complex coacervation methods

Virgin coconut oil (VCO) is produced by processing the flesh of coconut (Cocos nucifera L.). It has beneficial health effects due to the medium-chain fatty acids (MCFA), vitamins, and antioxidant contents. Since liquid VCO is not widely accepted by consumers for direct consumption, further processing into powder VCO can be achieved using microencapsulation methods, such as single-layer emulsification (SL), layer-by-layer emulsification (LBL), and complex coacervation (CC). Therefore, the present work aimed to determine the characteristics of microencapsulation of VCO powder by emulsification and coacervation complex methods over 30 days of storage period. Results showed that SL VCO emulsion remained stable for three days of storage, while LBL VCO emulsion experienced syneresis. The particle size of the reconstituted VCO powder was also larger than the fresh emulsion. LBL microcapsule had the highest yield at 74.17%, and there was an increase in moisture content (MC) during 30 days of storage in CC microcapsule. Meanwhile, MC of SL microcapsule was constant, and the equilibrium MC of LBL was retained during 15 days of storage. A microencapsulation efficiency of up to 78.65% was obtained for CC, and the value decreased for all microcapsules during the 30 days of storage. Different oxidative characteristics were also reported, resulting in increased peroxide value of VCO powder. Furthermore, all microcapsules had amorphous and glassy surface morphology, as well as different characteristics and stability during storage.

Pickering Emulsion Properties Generated by Nanofibrillated Cellulose Isolated from Oil Palm Fruit Bunch (OPEFB) as a Stabilizer

This study aims to find the optimal nanofibrillated cellulose (NFC) concentration isolated from oil palm empty fruit bunch (OPEFB) particles to form stable pickering emulsions against creaming and coalescence. The emulsification process is based on a combination of homogenizer and ultrasonication. Pickering emulsion was prepared by mixing the dispersed phase (palm oil) and the dispersing phase (NFC concentration of 0.05 - 0.7 w/v%) at the ratio of 10:90. Fresh emulsion has a milky white appearance and is homogeneous. However, some samples' creaming process occurred on the 30th day of storage. Microscopic observations show that the droplets are round with various sizes. Differences in NFC concentrations significantly affect droplet size, zeta potential, rheology, and emulsion stability. Increasing the NCF concentration resulted in smaller droplet sizes, viscosity, zeta potential, and pickering emulsion stability. The emulsion has high stability against coalescence and creaming. NFC at 0.7 w/v% generates an emulsion with the best characteristics and high stability against creaming and coalescence. OPEFB-based NFC has the potential as a pickering emulsion stabilizer particle that can be applied to the food and non-food industries.

Combination of carrageenan with sodium alginate, gum arabic, and locust bean gum: Effects on rheological properties and quiescent stabilities of partially crystalline emulsions

In the present study, carrageenan (CG) was combined with sodium alginate (SA), gum arabic (GA), and locust bean gum (LBG) to obtain four gum combinations (CG, CG + SA, CG + GA, and CG + LBG). The effects of different combinations on rheological properties and quiescent stabilities of PCEs were systematically investigated through characterization of fresh emulsion related parameters (rheological properties, forces between proteins, zeta potentials, surface tensions, interfacial adsorption properties, and multiple light scattering) and storage related parameters (visual appearance, creaming index, viscosities, particle sizes, and microscopic morphology). Rheological results indicated that CG PCEs had the highest apparent viscosities of 7.77–41.91 Pa·s at 0.01 s−1, followed by CG + SA PCEs (2.35–30.62 Pa·s), CG + GA PCEs (2.37–21.16 Pa·s), and CG + LBG PCEs (2.06–19.93 Pa·s). At low thickener concentration (0.02 %), CG PCE exhibited weak gel structure due to higher G′ than G″ at all frequencies, while CG + SA, CG + GA, and CG + LBG PCEs had entangled network due to intersection between G′ and G″. After three months of storage, CG + SA PCEs showed the lowest creaming index values (11.47–17.75 %), which were significantly lower than CG PCEs (15.35–20.85 %), CG + GA PCEs (15.97–24.42 %), and CG + LBG PCEs (17.13–21.71 %). Meanwhile, all the samples except for 0.02 % CG + SA PCE completely lost fluidity, and their viscosities were above 14,000 mPa·s. It was further found that CG stabilized emulsions showed severe droplet flocculation induced by hydrophobic interactions among adsorbed proteins. Combination of CG with SA, GA, and LBG, especially CG + SA, formed strong network structure and reduced contribution of hydrophobic interactions, which effectively inhibited flocculation of fat droplets, thereby improving rheological properties and storage stabilities of PCEs.

Oil-in-water emulsion gels stabilized with cellulosic polymers and chitosan: Themorheological and physical-chemical evaluation

This research evaluated the use of different polymer ratios, hydroxypropyl methylcellulose (HPMC) and methylcellulose (MC) with chitosan (CHI), in the production of emulgel by emulsification. The concentration was fixed at 2 % (w/v) for all polymers. 60/40 sunflower oil-in-water emulgels were made with a cellulosic polymer:chitosan ratio of (80:20), (70:30), and (60:40), respectively. The objective was to study how different proportions of a cellulosic polymer combined with chitosan can affect the stability, microstructure, and rheology of the emulgels to be used as potential oil carrier systems. Droplet size and microscopy results show oil-in-water (O/W) emulgels, and their interface was stabilized by mixing polymeric pairs, HPMC:CHI or MC:CHI. In the thermal analysis, it was identified in the entire temperature range studied (5 to 85 °C) that both emulgels, HPMC:CHI and MC:CHI, were presented as gels (G′ > G″). Thus, the addition of CHI to the systems modified their gelling behavior. Microscopy revealed that the emulsions at the 7th and 10th week of storage showed similar characteristics to the fresh emulsion. Therefore, these results indicate that the emulgels present good thermal resistance, the predominance of elastic behavior, and can retain high concentrations of oil in their structure (96 to 99 %).

Effects of environmental stimuli on the physicochemical and rheological properties of chitosan-macroalgal polyphenol stabilized Pickering emulsion

In this study, Pickering emulsions stabilized by chitosan (CS), chitosan-Laminaria japonica polyphenols (CP) and chitosan-Ascophyllum nodosum polyphenols (CB) were fabricated. This study also evaluated the stability of CS, CP, and CB under different environmental factors including pH (2–9), NaCl concentrations (0–500 mM), heat treatments (50–100 °C) and storage period (0–8 weeks). The characterization on interfacial layer of emulsion droplets demonstrated that macroalgal polyphenols could combined with the amorphous regions of chitosan particles through hydrogen bond and electrostatic interactions, providing stronger dual wettability with enhanced ability of interfacial layer in stabilizing Pickering emulsions. All three emulsions showed best droplet distribution, highest emulsion stability and specific surface area at pH 6 and 0 mM NaCl concentration as fresh emulsion. Moreover, CS, CP, and CB exhibited the rheological behaviour of pseudoplastic fluids at different pH and NaCl concentration. It should be noted that CP and CB exhibited higher emulsion stability than CS under a variety of environmental stresses. Overall, this research proved that chitosan-macroalgal polyphenol co-stabilized Pickering emulsion had enhanced stability against various environmental stimuli, which could be utilized as potential delivery and protection system for hydrophobic bioactive compounds.

Comparative study of high‐intensity ultrasound and high‐pressure homogenization on physicochemical properties of peanut protein‐stabilized emulsions and emulsion gels

AbstractThe physicochemical properties of peanut protein‐stabilized emulsions and emulsion gels prepared by high‐intensity ultrasound (HIU) and high‐pressure homogenization (HPH) were compared. The effects of different ultrasound emulsification conditions (ultrasonic time and power, protein concentration, and oil phase percentage) on the initial particle size and stability of peanut protein‐stabilized emulsions were investigated. It was observed that the optimal HIU emulsification conditions consisted of a concentration of 4% (w/v) proteins, a volume percentage of 30% (v/v) oil, and an ultrasonic treatment at 300 W for 20 min. Compared with the two emulsions prepared by HPH at 300 and 500 bar, respectively, the HIU‐prepared fresh emulsion showed a larger particle size, similar zeta potential but higher interfacial protein concentration and apparent viscosity. Additionally, the HIU‐prepared emulsion had lower flocculation and coalescence indices and was more resistant to gravitation separation during storage. The cold‐set gel strength of the HIU‐prepared emulsion was stronger than that of the HPH‐prepared emulsion (300 bar), but weaker than that of the emulsion (500 bar). The non‐adsorbed proteins from the HIU‐prepared emulsion had unique structural characteristics, such as higher molecular weight, more unordered secondary structures, and stronger surface hydrophobicity, which likely explained why the HIU‐prepared emulsion possessed better physical stability and gelling ability.Practical ApplicationsHigh‐pressure homogenization (HPH) is currently the most frequently used method in the food industry to produce emulsions. However, a high‐pressure homogenizer is expensive and not easy to operate. In contrast, high‐intensity ultrasound (HIU) emulsification is considered a cost‐effective technique. In this study, a peanut protein‐stabilized emulsion was successfully produced by HIU emulsification method. Its physical stability was significantly better than that of the emulsions made by HPH. This work provides new knowledge for the application of peanut protein as a natural emulsifier combined with ultrasonic technology in the food industry.

Characterization of encapsulated γ-oryzanol powder by spray drying using whey protein and maltodextrin as wall materials.

Characterizations of encapsulated γ-oryzanol powder (EOP) using whey protein concentrate (WPC) and maltodextrin as wall materials were studied. Rice bran oil (RBO) with 2% γ-oryzanol was encapsulated using different concentrations of WPC (0.2-1.0%) combined with 10% of maltodextrin before spray drying. The physicochemical characteristics and reconstitution of EOP were investigated. The results found that different concentrations of WPC affected EOP characteristics. The EOP coated 1% WPC exhibited low moisture content and water activity (aw) containing high γ-oryzanol content and encapsulation efficiency. Morphology of EOP using SEM displayed spheroid shape with smooth and crack-free surface. However, EOP emulsion had relatively larger particle size and lower solubility index than the fresh emulsion after reconstitution, but a good creaming stability of reconstituted EOP was observed. Therefore, it can be concluded that using 1% WPC combined with 10% maltodextrin provided good performance of encapsulated RBO with 2% γ-oryzanol using spray drying. According to physicochemical characteristics, the EOP has good potential as a food ingredient for food industry and as an excipient for pharmaceutical and cosmetic industries.

Emulsion stability of sugar beet pectin increased by genipin crosslinking

This work aimed to enhance the emulsifying properties of sugar beet pectin (SBP) by adopting a crosslinking strategy that covalently bridged the amino groups (–NH2) of lysine residues of the proteinaceous moiety using genipin (GP) as the crosslinker. Compared to control-SBP (C-SBP), GP crosslinked SBP (G-SBP) was larger in molecular weight (from 3.04 × 105 g/mol to 1.31 × 106 g/mol) and mean radius of gyration (from 34.8 nm to 39.2 nm), and showed a more compact conformation, as supported by analysis of high-performance size exclusion chromatography coupled with multiple angle light scattering (SEC-MALLS) and atomic force microscopy (AFM). G-SBP was featured by a new absorbance peak at ~595 nm, resulting in a distinct blue color of the aqueous solution. G-SBP suffered a slight decrease in interfacial properties and emulsifying activities in comparison to C-SBP, leading to a lower specific surface area and a larger volume-weighted mean diameter (d4,3) for the fresh emulsion. Nevertheless, the G-SBP stabilized emulsion was more stable than the C-SBP stabilized emulsion during storage for 21 d with d4,3 increasing from 0.541 μm and 0.425 μm to 0.625 μm and 1.66 μm for G-SBP and C-SBP, respectively. The improved emulsifying stability of G-SBP can be ascribed to the combination of the following two aspects: 1) G-SBP exerted a lager viscosity-enhancing effect to slow down droplet collision and flocculation; 2) the carbohydrate moiety of G-SBP formed a dense and compact hydrated layer providing strong steric stabilization for the oil droplets to resist flocculation and coalescence. Altogether, this work demonstrates that GP is a favorable agent to crosslink the side chains of SBP and modify its emulsification performance.

Surface evolution of synthetic bilgewater emulsion

Bilgewater is a regulated shipboard produced waste stream that often contains oil-in-water emulsion. Fundamental knowledge of emulsion surface changes is required for improved wastewater treatment; however, limited information is currently available. We have reported the first surface characterization of synthetic bilgewater emulsions using time-of-flight secondary ion mass spectrometry (ToF-SIMS) coupled with optical microscopy. A Navy standard bilgewater solution consisting of a hydrocarbon and detergent mixture is used as the synthetic bilgewater emulsion model. Both fresh and aged emulsion samples are analyzed to determine their droplet size distributions (DSDs) and surface chemical composition. Our results show that fresh emulsions are largely mono-modal with hydrocarbon fragments as the main surface composition. Aged emulsions are also mono-modal with slightly larger size. Both SIMS spectral comparison and Principal Component Analysis (PCA) show that some surfactant components appear on the fresh emulsion surface while larger molecular weight components appear at the aged bilge droplet surface. Our results indicate that the oil-water interface evolves after emulsion droplet formation. More importantly, surface evolution not only changes the bilgewater DSD, but also alters the surface chemical composition and reactivity.

Effect of polysaccharides from Polygonatum sibiricum on lipid-metabolism related mRNA and protein expression in hyperlipidemic mice

To study the effect of polysaccharides from Polygonatum sibiricum on mRNA and protein expressions of blood lipid metabolism in hyperlipidemic mice. The mice were randomly divided into 6 groups, namely the blank control group, the hyperlipidemia model group, the simvastatin group, and low, middle and high-dose PSP groups (200, 400, 800 mg·kg⁻¹·d⁻¹). Each group of the mice was administrated intragastrically for 14 days, respectively. Subsequently, every group of mice, except for the blank control group, was intraperitoneally injected with 75% fresh egg yolk emulsion for establishing the hyperlipidemic mice model. Upon completion of the administration, the contents of TC, TG, LDL-C and HDL-C in serum of each group were investigated in details. In particular, the mRNA expression levels of PPAR-α, PPAR-β, PPAR-γ, SREBP-1c, IL-6 and TNF-α of the liver tissues were detected by Real-time PCR, and the protein expression levels (including PPAR-α, PPAR-β, PPAR-γ, SREBP-1c, IL-6, TNF-α) were examined by Western blot. Consequently, the obtained results showed that the contents of the serum TC, TG, LDL-C of low, middle and high-dose PSP groups significantly decreased compared with those of the hyperlipidemia model group. Simultaneously, there were significant differences between middle-dose and high-dose PSP groups (P<0.01). In striking contrast, the contents of serum HDL-C of low, middle and high-dose PSP groups significantly increased, while obvious differences were also observed between middle-dose and high-dose PSP groups (P<0.01). Moreover, middle-dose and high-dose PSR groups could up-regulate the protein and mRNA expressions of PPAR-α, PPAR-β (P<0.05) compared with those of the hyperlipidemia model group, and down-regulate the expressions of PPAR-γ,SREBP-1c, IL-6 and TNF-α(P<0.05) compared with those of liver tissues of the hyperlipidemia model group. In conclusion, all of the above results suggested that PSP could inhibit the oxidation of the liver lipid, and regulate the expression levels of the corresponding genes and proteins relating to the lipid metabolism, so as to play a critical role for preventing hyperlipidemia.

Performance-Graded Specifications for Asphalt Emulsions Used in Chip Seal Preservation Treatments

This paper details the development of a framework for emulsion performance-grade (EPG) specifications for chip seal treatments. Chip seals are preservation surface treatments that are designed to improve the condition of the pavement surface while mitigating deterioration of the overall pavement structure. Asphalt emulsions used in chip seals often are selected based on factors that are not necessarily related to performance. Aggregate loss and bleeding have been identified as the most critical chip seal distresses that are related to binder performance. Storage stability, sprayability, and drain-out have been determined to be the most critical constructability concerns. For this study, binder and mixture test methods were identified to reflect the failure mechanisms for each critical distress type. The emulsion residue test methods that were identified to capture chip seal performance are the multiple stress creep and recovery test for bleeding and the dynamic shear rheometer frequency sweep test for low-temperature aggregate loss. The fresh emulsion test methods that were identified to capture chip seal constructability are the three-step shear test and storage stability test. The proposed EPG specifications for the fresh emulsion properties that are related to constructability were developed using statistical analysis of the binder test results. The proposed EPG specifications for the residual binder properties were developed by defining the temperature-independent relationships between the emulsion residue properties and mixture performance that correspond to each critical distress. Preliminary specification limits were then established based on the values of the binder properties that correspond to the critical mixture performance thresholds.

Excellent anti-fouling performance of PVDF polymeric membrane modified by enhanced CaA gel-layer

Calcium alginate gel-layer polymeric membranes with excellent anti-fouling ability were developed via dip-coating method through sodium alginate and calcium chloride to form gel-layers onto different polyvinylidene fluoride membranes. SEM, FT-IR, DCA and mechanical properties were operated for characterization. Comprehensive investigation of anti-fouling ability including PWF, FRR%, long-term performances with fouling resistances were conducted. Results showed a significant improvement after cross-linking, in which recovery rate reached to 99.2% and kept steady while contact angle decreased remarkably. Enhanced gel-layer with MWCNTs-COOH was also developed and applied in the commercial PVDF MF membrane and applied in fresh milk emulsion concentration.

Stabilization of oil-in-water-in-oil (O1/W/O2) Pickering double emulsions by soluble and insoluble whey protein concentrate-gum Arabic complexes used as inner and outer interfaces

Soluble (SC) and insoluble (IC) complexes were obtained from interacting whey protein concentrate-gum Arabic, at pH of 4.0, using biopolymer mass ratios of 2:1 and 3:1, respectively. Particles (SPT) were produced from IC and dried at different temperatures. Higher temperatures induced a higher contact angle, modified the protein secondary structure to a greater extent, and decreased the interfacial tension to lower values. The O1/W primary emulsion and the O1/W/O2 double emulsions were stabilized with SC and SPT, respectively. The mean droplet size of the fresh primary emulsion and of the double emulsions increased to from 0.62 to 0.66 μm and from (9.34–4.35 to 10.45–4.63 μm) after 76 days of storage, respectively. Confocal micrographs permitted to observe the inner oil droplets surrounded by SC, and the double emulsion water droplets by SPT. Hydrophobic particles obtained from IC represent a viable alternative for substituting the use of synthetic surfactants in W/O2 interfaces.

Performance-Related Specifications for Asphalt Emulsions Used in Microsurfacing Treatments

This paper details the development of a framework for emulsion performance grade (EPG) specifications for microsurfacings. Microsurfacings are preservation surface treatments designed to improve the condition of the pavement surface while mitigating deterioration of the overall pavement structure. Asphalt emulsions used in microsurfacings are often selected on the basis of factors that are not necessarily related to performance. Rutting and thermal cracking have been identified as the most critical microsurfacing distresses related to binder performance. In the assessment of fresh emulsion properties, storage stability and mixability have been determined to be the most critical constructability concerns. For this study, binder and mixture test methods were identified to reflect the failure mechanisms for each critical distress type. The two emulsion residue test methods that were identified to capture microsurfacing performance were ( a) the multiple stress creep and recovery test for rutting and ( b) the dynamic shear rheometer frequency sweep test for thermal cracking. The identified critical fresh emulsion properties that related to constructability included storage stability and viscosity measured at a low shear rate. The proposed EPG specifications for fresh emulsion properties related to constructability were developed by using statistical analysis of the binder test results. The EPG specifications for residual binder were developed by defining the temperature-independent relationships between the emulsion residue properties and the mixture performance that corresponded to each critical distress. Preliminary specification limits were then established on the basis of the values of the binder properties that corresponded to the critical mixture performance thresholds.

Factors influencing the structure build-up of fresh cement asphalt emulsion paste

Fresh cement asphalt emulsion mortar (CA mortar) is required to be highly flowable for grouting when it is employed in slab track structure. Segregation and bleeding easily occur after placement. In essence, it is because fresh CA paste has a low rate of structure build-up. However, limited information is reported about the thixotropy of CA paste. A thixotropy model based on structure parameter, which is deduced from constant shear rate test, is proposed to study the structure build-up of CA paste. In the model, the initial structure parameter and the rate of structure build-up are used to describe the evolution law of the structure parameter with resting time, which can be employed to quantitatively evaluate the structure build-up process of CA paste. The thixotropy model is used to study the influence of every constituent on the structural build-up process of CA paste. Results show that asphalt emulsion and superplasticizer dosage are two main factors influencing the structure build-up of CA paste, but water-to-cement ratio and viscosity-modified agent dosage have little effect on the structure build-up of CA paste.

The role and interaction of superplasticizer and emulsifier in fresh cement asphalt emulsion paste through rheology study

The workability and mechanical properties of cement asphalt emulsion (CA) mortar are unstable due to the complex interaction between cement and asphalt emulsion. To reveal the interaction between cement and asphalt emulsion, the effect of emulsifier and superplasticizer on the rheology of cement paste and asphalt emulsion is investigated, respectively, and the effect of the interaction between emulsifier and superplasticizer on the rheology of cement paste is studied in this paper as well. Results show that the apparent viscosity and yield stress of asphalt emulsion increase with superplasticizer and emulsifier dosage. Emulsifier can change the yield stress and apparent viscosity of cement paste, and its effect on cement paste differs greatly with the type and dosage of emulsifier. Some emulsifiers can increase the yield stress of cement paste, but some emulsifiers can decrease the yield stress of cement paste. Emulsifier has interaction with superplasticizer, thus affecting the reducing water effect of superplasticizer on cement paste. There is a competition relationship between emulsifier and superplasticizer when they are adsorbed by cement particles. The mixing method, in which superplasticizer is mixed with cement before emulsifier added, is beneficial to obtain a lower apparent viscosity of cement paste for all tested emulsifiers.

Viscosity prediction of fresh cement asphalt emulsion pastes

Cement asphalt emulsion (CA) composite materials are becoming promising building materials in recent years. Assessing their rheological behavior is crucial for the success of a particular application. Fresh CA pastes with different asphalt emulsion to cement mass ratios (AE/C) have significantly different compositions, and design of their rheological properties is not an easy task. The minimum apparent viscosity of CA pastes with different AE/C is predicted by a viscosity prediction model. The model parameters include maximum particle packing density (ϕ m) and an adjusting factor b. A predictive model of CA composite particles is proposed, in which the maximum particle packing density of CA pastes can be determined by the maximum particle packing density of cement paste, the maximum particle packing density of asphalt emulsion, and the volume fraction of asphalt in asphalt-cement system. The predictive model requires different adjusting factor b for CA pastes with anionic and cationic asphalt emulsion when the predicted ϕ m is used for viscosity prediction. The proposed viscosity prediction equations do offer a simple and reliable method for the viscosity prediction of CA pastes with a wide AE/C range, and can be used to design the rheological properties of CA pastes.

The thixotropic behavior of fresh cement asphalt emulsion paste

The workability of grouting cement asphalt emulsion (CA) mortar is governed by the intrinsic thixotropic behavior of CA paste, but limited information is reported about the thixotropic behavior of CA paste. A new thixotropy method of constant shear rate test is proposed to study the thixotropic behavior of CA paste with different asphalt emulsion to cement ratios (AE/C). In the model, the initial structure parameter and the structure rebuilding rate are used to quantitatively describe the structure rebuilding process, the characteristic time of de-flocculation is used to evaluate the de-flocculation process, and the equilibrium shear stress is used to study the irreversible change of CA paste in the thixotropy test. Results show that CA pastes have significantly different thixotropic behavior compared to cement paste. The initial structure parameter and structure rebuilding rate of CA pastes are much smaller than cement paste, and the structure rebuilding rate decreases significantly with AE/C. The characteristic time of de-flocculation of cement paste changes little at different resting time, however, it increases significantly at the first 5min resting time and then keep stable for CA pastes. The equilibrium shear stress of cement paste does not change in 20min, but it increases with time for CA pastes due to the demulsification of asphalt emulsion.