Surface-active Additives Research Articles

INVESTIGATION OF SURFACE PROPERTIES OF MODIFIED BITUMEN COMPOSITIONS

One of the main reasons for premature destruction of road surfaces is the poor quality of road bitumen. An effective way to improve the quality of a bitumen binder is to modify it with polymer or surface-active additives. The goal is to determine the effect of the concentration of modifiers on surface tension in binary "bitumen-surfactant", "bitumen-polymer" and triple "bitumen-surfactant-polymer" systems. The methodology of the work included measuring the surface tension of modified bitumen systems depending on the quantitative content of additives in bitumen. Results and discussion: As follows from the analysis of the data obtained, in bitumen systems with a limited concentration of polymer AG-4I (C≤1 g/dm3), the effect of reducing surface energy at the interface with air is achieved by concentrating surfactants in the surface layer, which are part of the structure of the bitumen itself. The extreme nature of the change in surface tension was also recorded in AC-2 bitumen compositions. Conclusion: In the "bitumen-AG-4I-AS-2" triple systems, the change in the specific surface energy at the "liquid-gas" interface is not an additive value, taking into account the separate contribution of AG-4I and AS-2. The concentration threshold of additives to achieve a minimum surface tension varies in comparison with binary compositions. With the combined administration of AG-4I (C=1g/dm3) and AC-2 (C=1g/dm3), the surface tension decreased by 9.30 mN/m compared with unmodified bitumen.

Amide/Amino-Based Functional Additives for Lubricants: Structure, Antimicrobial Activity and Wear Resistance.

The lubricating properties of the lubricants were tested under boundary friction conditions; it was found that the surface-active additives had reduced the wear mark and thus the value of the Goz/40 parameter (limiting load of wear). The introduction of a surfactant containing amide compounds into the oils and greases was highly effective in slowing down the oxidation process. Lubricants containing mono-15 ([3-(N,N,N-dimethylbuthylamine)propyl]hexadecanamide chloride) and 15-4-15 (tetramethylene-bis [3-(N,N,N-dimethylamine)propyl]hexadecanamide) additives were characterised by higher oxidation stability compared to the unmodified lubricants. Both of the analysed substances showed bactericidal properties against Staphylococcus aureus and Salmonella enteritica. Tests of antibacterial activity in the lubricants with the addition of mono-15 and 15-4-15 confirmed that these lubricants can be considered bactericidal against Gram-positive and Gram-negative bacteria.

Surface forces and friction between Langmuir-Blodgett polymer layers in a nonpolar solvent

Optimization of boundary lubrication by tuning the confined molecular structures formed by surface-active additives such as surfactants and polymers is of key importance to improving energy efficiency in mechanical processes. Here, using the surface forces apparatus (SFA), we have directly measured the normal and shear forces between surface layers of a functionalised olefin copolymer (FOCP) in n-dodecane, deposited onto mica using the Langmuir-Blodgett (LB) technique. The FOCP has an olefin backbone decorated with a statistical distribution of polar-aromatic groups, with a structure that we term as “centipede”. The effect of lateral confinement, characterised by the surface pressure, Πdep, at the air–water interface at which the LB films are transferred, was examined. Normal force profiles revealed that the thickness of the LB films increased significantly with Πdep, with the film thickness (t > 20 nm) inferring a multi-layered film structure, consistent with the interfacial characterisation results from synchrotron X-ray reflectivity (XRR) measurements. The coefficient of friction, µ, between the LB films spanned two orders of magnitude from superlubricity (µ ∼ 0.002) to much higher friction (µ > 0.1) depending nonlinearly on Πdep, with the lowest friction observed at the intermediate Πdep. Molecular arrangement upon LB compression leads to the multilayer film with a structure akin to an interfacial gel, with transient crosslinking facilitated by the intra- and inter-molecular interactions between the functional groups. We attribute the differences in frictional behaviour to the different prevalence of the FOCP functional groups at the lubricating interface, which depends sensitively on the degree of compression at the air–water interface prior to the LB deposition. The LB films remain intact after repeated compression (up to pressures of 10 MPa) and shear cycles, indicating strong surface anchorage and structural robustness as a load-bearing and shear-mediating boundary layer. These unprecedented results from the friction measurements between LB films of a statistical copolymer in oil point towards new strategies for tailoring macromolecular architecture for mediating efficient energy dissipation in oil-based tribological applications.

MODIFIED COMPOSITE CEMENTS IN THE SYSTEM СаО–Al2O3–SO3–H2O

Problem statement. One of the most important issues today is the reconstruction, reinforcement of buildings and structures, as well as the creation of new construction materials with the required physical and mechanical properties. The solution to this problem is possible through controlling and regulating the properties of the initial components of the concrete mixture, increasing the amount of surface components at the interface. To control the properties of construction materials, and thus to obtain the cement stone with the specified physical and mechanical properties is possible by means of using various mineral and surface-active additives in the composition of hardened cement stone. Development of sulfoaluminate compositions based on calcium sulfates, alumina cement and surface-active substances (surfactants) makes it possible to significantly expand the raw material base and the scope of application. The purpose of article – obtaining a composite binder with increased density, water resistance and improved technological factors. Conclusions. Alumina cement G-40, 50 and gypsum G-5-II in the ratio of 30−70 % (with hemihydrate gypsum being its main material) have been used in the research to achieve the set purpose. Their properties have been determined as well as the optimal ratio of components for obtaining a specific mineralogical composition with the maximum content of chemically bound water is carried out. Studies have shown that increased content of calcium sulfate has a positive effect on the amount of ettringite and that the optimal value is in the range of 30−40 % by weight of the composition. The exact ratio of components can be determined based on their mineralogical compositions and hydration process conditions. At the ratio of AC-40/G % – 70/30 % a considerable amount of calcium hydroaluminates remain; compressive and flexural strength is 14 and 10 MPa, respectively. When conducting research, the effect of plasticizers on the main technological and physical and mechanical properties of composite binders has been established: the Sika Viscocrete G additive has the greatest plasticizing effect. The composite binders presented above can be used for the manufacture of dangerous structures.

Oligo(2-alkyl-2-oxazoline)-based graft copolymers for marine antifouling coatings

Poly(ethylene glycol) (PEG)-based graft copolymers have been widely applied for the modification of poly(dimethyl siloxane) (PDMS)-based coatings that resist marine biofouling. In this research, we synthesized oligo(2-alkyl-2-oxazoline) (OAOXA)-based graft copolymer analogues, and subsequently tested their applicability in the formulation of structurally similar coatings, aiming to highlight the influence of polymer composition on biopassive properties. In particular, poly(dimethyl siloxane methacrylate)-co-oligo(2-alkyl-2-oxazoline)methacrylate copolymers were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization, starting from oligo(2-ethyl-2-oxazoline)- and oligo(2-methyl-2-oxazoline)-methacrylate macromonomers (OEOXMA and OMOXMA, respectively). Amphiphilic copolymer films with OAOXA grafts were found to be more hydrophilic with respect to those obtained using PEG analogues. PDMS coatings containing the graft copolymers as surface additives were tested towards the settlement of the macrofouler Ficopomatus enigmaticus and the diatom Navicula salinicola. The biofouling experiments indicated that OAOXA-containing films showed a comparable and in some cases improved performance with respect to their PEG-based counterparts, thus highlighting how OAOXA-based graft copolymers represent a valid alternative to PEG derivatives as surface-active additives to design antibiofouling coatings.

(Digital Presentation) Importance of Electrified Interfaces in Researchable Metal Anode Batteries: Ionic Liquid Electrolyte Composition and Electrode Preconditioning

Electrode/electrolyte interface is an important part of many electrochemical systems, as its local structure, so called electric double layer (EDL), defines mechanism of charge transfer and stability of the device. Alkaline metal anodes possess high theoretical capacity due to ability of metal-ions to pack in the dense crystal structure, however, their application is rather limited due to formation of dendrites from non-uniform metal deposition and/or poor quality of the interphase. Experimentally, it was found that variation of ionic liquid (IL) electrolyte composition (salt concentration, presence of cosolvent) and applied current density for the formation cycling, i.e., cycling to activate electrode surface before utilisation, significantly affect dendritic growth and stability of metal anode. This presentation aims to show the molecular level relationships between interfacial structure, value of metal deposition potential and the interphase formation with ionic liquid electrolyte of different compositions (salt concentration, presence of cosolvent). Each electrolyte composition results in a particular interfacial metal-ion solvation environment which controls the reductive stability, metal-ion deposition potential, and ultimately the composition and properties the solid-electrolyte interphase (SEI). The latter is dependent on the EDL composition such as the IL cation/metal cation-IL anion ratio or the presence of other surface active additives. Based on this work, our group at Deakin University developed a theoretical framework to choose an optimum current density for the formation cycling of lithium/sodium metal anodes with ionic liquid electrolytes of different composition (salt concentration, presence of cosolvent). Details of these findings are published in following literature [1, 2].

Lubrication mechanism of a strong tribofilm by imidazolium ionic liquid

Friction modifiers (FMs) are surface-active additives added to base fluids to reduce friction between rubbing surfaces. Their effectiveness depends on their interactions with rubbing surfaces and may be mitigated by the choice of the base fluid. In this work, the performance of an imidazolium ionic liquid (ImIL) additive in polyethylene-glycol (PEG) and 1,4-butanediol for lubricating steel/steel and diamond-like-carbon/diamond-like carbon (DLC—DLC) contacts were investigated. ImIL-containing PEG reduces friction more effectively in steel—steel than DLC—DLC contacts. In contrast, adding ImIL in 1,4-butanediol results in an increase in friction in steel—steel contacts. Results from the Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and focused ion beam-transmission electron microscopy (FIB-TEM) reveal that a surface film is formed on steel during rubbing in ImIL-containing PEG. This film consists of two layers. The top layer is composed of amorphous carbon and are easily removed during rubbing. The bottom layer, which contains iron oxide and nitride compound, adheres strongly on the steel surface. This film maintains its effectiveness in a steel—steel contact even after ImIL additives are depleted. Such film is not observed in 1,4-butanediol where the adsorption of ImIL is hindered, as suggested by the quartz crystal microbalance (QCM) measurements. No benefit is observed when the base fluid on its own is sufficiently lubricious, as in the case of DLC surfaces.This work provides fundamental insights on how compatibilities among base fluid, FM, and rubbing surface affect the performance of IL as surface active additives. It reveals the structure of an ionic liquid (IL) surface film, which is effective and durable. The knowledge is useful for guiding future IL additive development.

Interphase phenomena during humidification electrostatic fiber concrete

Objective. The targets of modern construction require the search and development of new efficient technologies. The main trend in building architecture is the creation of spectacular (buildings-symbols, objects of competitions of countries) objects and structures that attract the attention of people and add to the list of unique attractions. To implement such projects, it is necessary to introduce high-tech advanced techniques, which is the electrostatic method of manufacturing fiberreinforced concrete.Method. The paper considers a new method of forming products and structures from fiber-reinforced concrete using electrostatics. An important place in the method is occupied by the physics of interfacial phenomena, namely wetting and capillary effects. The electrostatic deposition of layers of dry concrete mixture on the shaping frame occurs with the help of electrostatic sprayers.Result. This method allows saving cement, due to the use of a water-cement ratio close to the theoretical value. The issue of compaction of applied layers of dry concrete mix due to wetting with water with surface-active additives is discussed. In this regard, the kinetics of filling through and dead-end capillaries with water and other aspects of the new technology are considered. A hydrophilic binder has been developed using calcium lignosulfonate additive, which makes it possible to demonstrate the effectiveness of the electrostatic method in the future.Conclusion. The processes of wetting and the kinetics of liquid filling capillaries and channels of various shapes between the particles of the dry concrete mixture, as well as the compaction of the powder system as a result of moisture, will make it possible to realize difficult and unique projects in reality. The developed hydrophilic cement based on the surface-active additive LST (0.25%) contributes to the effect of interfacial electrostatic adhesion, thereby improving the properties of fiber-reinforced concrete.

Crystal substrate inhibition during microbial transformation of phytosterols in Pickering emulsions.

Water-oil interface of bacterial cell-stabilized Pickering emulsions is an exceptional habitat for microbial assimilation of both hydrophobic nutrients solubilized in oil phase and hydrophilic ones solubilized in water phase. Crystal substrate inhibition, i.e., decreasing phytosterol degradation with the increase loading of crystal phytosterols, is always observed during microbial transformation of phytosterols into steroid synthons in Mycolicibacterium sp (China Center of Industrial Culture Collection, CICC 21,097) cell-stabilized Pickering emulsions. In the present work, we confirmed that crystal substrate inhibition was attributed to the interaction between M. neoaurum and phytosterol crystals that led to the detachment of bacterial cells from the oil-water interfaces in bacterial cell-stabilized Pickering emulsions. Under the selected operation condition (25ml BEHP per 40ml water, 60g/L glucose, 25g/L phytosterols), the product androst-4-ene-3, 17-dione (AD) and androsta-1, 4-dien-3, 17-dione (ADD) concentration increased linearly with the progress of microbial transformation and reached almost 6g/L at the 11th day. This is a paradigm for microbial transformation of crystal substrates as well as in the presence of other surface active additives (such as chitosan and nonionic surfactants) in bacterial cell-stabilized Pickering emulsions. KEY POINTS: • Microbial transformation of crystal phytosterols in Pickering emulsions • Crystal substrate inhibition occurring during microbial transformation • Interaction between phytosterol crystals and bacterial cells leading to demulsification.

Stable and Efficient Lithium Metal Anode Cycling through Understanding the Effects of Electrolyte Composition and Electrode Preconditioning

Stable metal anode cycling for high energy density batteries can be realized through modification of electrolyte composition and optimization of formation protocols, i.e., electrode interphase preconditioning conditions. However, the relationship between these and the electrochemical performance is still unclear due to a lack of molecular level understanding of electric double layer (EDL) changes with modification of these two parameters. Herein, we examine the impact of ionic liquid (IL) electrolyte composition (salt concentration and cosolvent) and preconditioning cycling conditions on Li anode performance through EDL changes affecting both the solid–electrolyte interphase (SEI) and deposition morphology. Each electrolyte composition results in a particular interfacial Li-ion solvation environment, which controls the reductive stability, Li deposition potential, and ultimately the composition of properties of the SEI. The latter is dependent on the EDL composition such as the IL cation/Li-anion ratio or the presence of other surface active additives. It is found that in a superconcentrated electrolyte, a high current density (≥10.0 mA cm–2/1.0 mAh cm–2) is beneficial during the metal anode preconditioning step, compared with the case of low Li salt-containing IL. This correlates with a predominance of Lix(anion)y (x > y) at a highly negatively charged interface, which is present when higher current densities are used for preconditioning, as suggested by molecular dynamics simulations. In contrast, for the lower viscosity superconcentrated electrolyte containing 20 wt % of ether cosolvent, a more moderate preconditioning step current density (6.0 mA cm–2/1.0 mAh cm–2) leads to an optimized deposition morphology and improved cycling performance. This is a consequence of the competing processes of ion transport at the interface, which controls the Li+ ion flux and the intrinsic reduction kinetics occurring at the more negative electrode.

Preparation and Characterization of Fenofibrate Microparticles with Surface-Active Additives: Application of a Supercritical Fluid-Assisted Spray-Drying Process.

In this study, supercritical fluid-assisted spray-drying (SA-SD) was applied to achieve the micronization of fenofibrate particles possessing surface-active additives, such as d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), sucrose mono palmitate (Sucroester 15), and polyoxyethylene 52 stearate (Myrj 52), to improve the pharmacokinetic and pharmacodynamic properties of fenofibrate. For comparison, the same formulation was prepared using a spray-drying (SD) process, and then both methods were compared. The SA-SD process resulted in a significantly smaller mean particle size (approximately 2 μm) compared to that of unprocessed fenofibrate (approximately 20 μm) and SD-processed particles (approximately 40 μm). There was no significant difference in the effect on the particle size reduction among the selected surface-active additives. The microcomposite particles prepared with surface-active additives using SA-SD exhibited remarkable enhancement in their dissolution rate due to the synergistic effect of comparably moderate wettability improvement and significant particle size reduction. In contrast, the SD samples with the surface-active additives exhibited a decrease in dissolution rate compared to that of the unprocessed fenofibrate due to the absence of particle size reduction, although wettability was greatly improved. The results of zeta potential and XPS analyses indicated that the surface-active additive coverage on the surface layer of the SD-processed particles with a better wettability was higher than that of the SA-SD-processed composite particles. Additionally, after rapid depletion of hydrophilic additives that were excessively distributed on the surfaces of SD-processed particles, the creation of a surface layer rich in poorly water-soluble fenofibrate resulted in a decrease in the dissolution rate. In contrast, the surface-active molecules were dispersed homogeneously throughout the particle matrix in the SA-SD-processed microparticles. Furthermore, improved pharmacokinetic and pharmacodynamic characteristics were observed for the SA-SD-processed fenofibrate microparticles compared to those for the SD-processed fenofibrate particles. Therefore, the SA-SD process incorporating surface-active additives can efficiently micronize poorly water-soluble drugs and optimize their physicochemical and biopharmaceutical characteristics.

Amphiphilic Polyphosphonate Copolymers as New Additives for PDMS-Based Antifouling Coatings.

Poly(ethyl ethylene phosphonate)-based methacrylic copolymers containing polysiloxane methacrylate (SiMA) co-units are proposed as surface-active additives as alternative solutions to the more investigated polyzwitterionic and polyethylene glycol counterparts for the fabrication of novel PDMS-based coatings for marine antifouling applications. In particular, the same hydrophobic SiMA macromonomer was copolymerized with a methacrylate carrying a poly(ethyl ethylene phosphonate) (PEtEPMA), a phosphorylcholine (MPC), and a poly(ethylene glycol) (PEGMA) side chain to obtain non-water soluble copolymers with similar mole content of the different hydrophilic units. The hydrolysis of poly(ethyl ethylene phosphonate)-based polymers was also studied in conditions similar to those of the marine environment to investigate their potential as erodible films. Copolymers of the three classes were blended into a condensation cure PDMS matrix in two different loadings (10 and 20 wt%) to prepare the top-coat of three-layer films to be subjected to wettability analysis and bioassays with marine model organisms. Water contact angle measurements showed that all of the films underwent surface reconstruction upon prolonged immersion in water, becoming much more hydrophilic. Interestingly, the extent of surface modification appeared to be affected by the type of hydrophilic units, showing a tendency to increase according to the order PEGMA < MPC < PEtEPMA. Biological tests showed that Ficopomatus enigmaticus release was maximized on the most hydrophilic film containing 10 wt% of the PEtEP-based copolymer. Moreover, coatings with a 10 wt% loading of the copolymer performed better than those containing 20 wt% for the removal of both Ficopomatus and Navicula, independent from the copolymer nature.

Statistical analysis of the distribution of impurities during copper electrorefining

Electrolytic copper refining makes it possible to obtain high purity metal, so the analysis of the main ways of impurity transition into electrolysis products is an actual problem. If it is solved, the process can be controlled when changing the composition of raw materials and, as a result, the content of impurities in the anodes. This paper uses the comprehensive analysis and synchronization of a large array of data on impurities concentrations in various process media (anodes, electrolyte, slime, and cathode metal) obtained on the series of commercial cells to identify the directions of impurity flows and relationship between their content in these media. It is shown that the transition of impurities from one process medium (source) to another (receiver) is implemented according to four main patterns: linear increase, no visible dependence, the presence of a limit concentration in the receiver and the presence of a threshold concentration in the source. The paper provides the results obtained in the statistical analysis of the distribution of six impurities (bismuth, arsenic, lead, sulfur, nickel and silver) belonging to different groups in four main pairs of the impurity source – receiver: anode – solution, anode – slime, slime – cathode, solution – cathode. The coefficients of linear regression equations are determined and their significance is estimated for all dependencies of the impurity concentration in the source on the content in the receiver. The coefficients obtained make it possible to explain the impurity transition paths observed in the commercial cells and predict the quality of cathode copper and the composition of slimes when the anode composition changes. The calculations showed that impurities are accumulated in cathodes due to the occlusion of slime particles and incomplete solution removal from the surface of commercial cathodes rather than due to electrochemical reactions. The copper electrorefining technology should be improved and developed so as to find surface-active additives that would prevent the adsorption of suspended slime particles on the cathode surface, as well as better wash them from the electrolyte.

Wear of hydrogenated DLC in MoDTC-containing oils

This paper describes a study of the effect on MoDTC-promoted a-C:H DLC wear of adding various surface-active additives used in engine lubricants, including ZDDP, an ashless EP additive, Ca detergents, dispersants, an OFM and a PAMA, to an MoDTC solution. Tribofilms formed on wear tracks on steel were analysed using SLIM, TEM, STEM-EDX, Raman spectroscopy and XPS. Relevant mechanisms by which these additives reduce the impact of MoDTC on DLC wear have also been suggested. DLC wear in PAO+Mo can be reduced by the presence of other surface-active additives in three ways. Firstly, asperity contact between DLC and steel can be mitigated by forming thick antiwear tribofilms. Secondly, other additives can increase the ratio of MoS2:MoO3, reducing the amount of wear-enhancing MoO3 in the tribofilm. Thirdly, the amount of MoDTC tribofilm including MoO3 can be reduced by the competitive adsorption of other surface-active additives. This study has practical implications for ways in which DLC surfaces can be protected by lubricant formulation.

Perfluoropolyether-based oleophobic additives: Influence of molecular weight distribution on wettability of polyethylene terephthalate films

Fluorinated oligomeric polyester (FOP) with significantly different molecular weight distributions were synthesized for use as surface-active additives to alter the wettability of polyester films. Specifically, FOPs had different weight average molecular weight (MW) of 5.4 and 10 kDA. The addition of FOPs in polyethylene terephthalate (PET) in different concentrations results in reducing the surface energy of PET/FOPs films. The PET/FOP film surfaces enriched with FOPs exhibited high water and oil repellency. It is found that not only concentration of FOPs in blends but also their MW influences wettability of PET/FOP film surfaces. The highest values of water and oil repellency were obtained when we used either low concentrations of low MW fluorinated polyesters that migrated to the surface easily, thus higher surface coverage were obtained, or high concentrations of higher MWpolyesters in the blends.

Dilatational rheology of water-in-diesel fuel interfaces: effect of surfactant concentration and bulk-to-interface exchange.

Micrometer-sized water droplets dispersed in diesel fuel are stabilized by the fuel's surface-active additives, such as mono-olein and poly(isobutylene)succinimide (PIBSI), making the droplets challenging for coalescing filters to separate. Dynamic material properties found from interfacial rheology are known to influence the behavior of microscale droplets in coalescing filters. In this work, we study the interfacial dilatational properties of water-in-fuel interfaces laden with mono-olein and PIBSI, with a fuel phase of clay-treated ultra-low sulphur diesel (CT ULSD). First, the dynamic interfacial tension (IFT) is measured using pendant drop tensiometry, and a curvature-dependent form of the Ward and Tordai diffusion equation is applied for extracting the diffusivity of the surfactants. Additionally, Langmuir kinetics are applied to the dynamic IFT results to obtain the maximum surface concentration (Γ∞) and ratio of adsorption to desorption rate constants (κ). We then use a capillary pressure microtensiometer to measure the interfacial dilatational modulus, and further extract the characteristic frequency of surfactant exchange (ω0) by fitting a model assuming diffusive exchange between the interface and bulk. In this measurement, 50-100 μm diameter water droplets are pinned at the tip of a glass capillary in contact with the surfactant-containing fuel phase, and small amplitude capillary pressure oscillations over a range of frequencies from 0.45-20 rad s-1 are applied to the interface, inducing changes in interfacial tension and area to yield the dilatational modulus, E*(ω). Over the range of concentrations studied, the dilatational modulus of CT ULSD with either mono-olein or PIBSI increases with a decrease in bulk concentration and plateaus at the lowest concentrations of mono-olein. Characteristic frequency (ω0) values extracted from the fit are compared with those calculated using equilibrium surfactant parameters (κ and Γ∞) derived from pendant drop tensiometry, and good agreement is found between these values. Importantly, the results imply that diffusive exchange models based on the equilibrium relationships between surfactant concentration and interfacial tension can be used to infer the dynamic dilatational behavior of complex surfactant systems, such as the water-in-diesel fuel interfaces in this study.

Kinds of concrete shrinkages, their importance and prevention methods

The basis for the geopolymers production was drawn up by prof. Kühl, well known to present day from the introduction of the modulus of clinker lime saturation: This Kühl’s formula was lined on the assumption that the best clinker should be composed of C3S, C3A and C2F and the mass ratio of CaO in respect to other components is equal adequately: 2.8, 1.65 and 0.70. The analyses of the equilibrium condition in the four components system led Kühl to the so-called lime criterion, equal to the permissible maximal lime content in clinker, in the conditions far from the equilibrium: One of the unfavourable properties of concrete is shrinkage which is linked with the volume changes of cement paste. We distinguish the following kinds of shrinkage: – “chemical” shrinkage called also the contraction or Le Chatelier shrinkage, – plastic shrinkage, – autogenic shrinkage or spontaneous, sometimes called auto drying, – drying shrinkage. There are several methods to eliminate concrete shrinkage. The ettringite crystallization is one of the inorganic compounds methods and is based on Klein’s complex addition to cement. This complex is causing the rapid ettringite formation and the shrinkage is diminished. There are also organic admixtures which action is the reduction of the water surface tension. There are surface-active additions that are reducing this tension, in capillaries. The organic admixtures which are diminishing the shrinkage are based on neopentyl glycol or similar chemical compounds. In the study, the shrinkage-reducing admixture BASF Master Life SRA 815 alone and with CaO addition were examined. It was shown that CaO addition is giving very low diminishing of cement shrinkage, contrary to the fluid admixture Master Life SRA 815 which has a high diminishing influence on cement shrinkage. However, the simultaneous addition of CaO is increasing the diminishing influence of this fluid admixture. The addition of Klein’s complex does not influence of shrinkage but its simultaneous addition with Master Life SRA 815 gives higher shrinkage diminishing.

Direct prediction of foamability of aqueous surfactant solutions using property values

Foams are the dispersion of gas/vapor bubbles stabilized by surface-active additives dissolved in a liquid medium. Foamability refers to the amount of foam generated and is an important parameter which dictates the choice of additives and their concentrations in various industrial processes and applications such as enhanced oil recovery, food, cosmetics, and heat transfer, among others. Typical foamability characterization strategies are qualitative in nature (foam height or volume) and can only be used for comparisons within the limits of experimental parameters originally tested for. Here we use the Bartsch method to characterize aqueous foaming solutions of commonly used surfactants (SDS and CTAB). We first define a non-dimensional parameter ‘foamability index’, as the ratio of the volume of foam generated to the volume of aqueous solution used. We next apply Buckingham’s Pi theorem to derive a dimensionless parameter ‘foamability number’, which essentially is a compilation of solution properties which dictate foamability. We show that the foamability measurements in the present work collapse on a unified curve of ‘foamability index’ versus the ‘foamability number’. Importantly, the foamability data from literature for other surfactants such as DTAB, SDBS, and Triton X-100 also fall on the same master curve. The foamability number is next shown to explain some puzzling foamability trends in literature which could otherwise not be explained using concentration as the only parameter. The power of this prediction tool is further illustrated by the accurate prediction of literature results for pool boiling critical heat flux with foaming solutions without any experimental inputs.

Performance comparison of warm mix asphalt for plateau area

The warm mix asphalt (WMA) technology is commonly applied for highway pavements in high-altitude plateau regions in China, where extreme weather conditions are common. The study is to evaluate the performance of WMA with different additives in the areas. The tests show that all the additives could reduce the viscosity of asphalt binder to reduce the mixing and compacting temperature of asphalt mixture. The solid additives could also decrease the penetration and ductility value, and increase the softening point and the PG high temperature of asphalt binder; therefore, are suitable for improving the high-temperature performance of WMA in the high-temperature regions. However, the surface-active liquid additives are suitable in the plateau areas in low-temperature conditions. The lab data for the Ya-Kang highway pavement to Tibet Plateau show it is suitable to control the mixing temperature at about 20°C lower than the normal hot mix asphalt during the construction period.

Experimental Investigations of Concrete on Slag Portland Cement as a Coating Material for Agricultural Aerodromes

The results of concrete testing on sulphate-resistant slag Portland cement for rigid coating of agricultural roads and aerodromes are presented in the paper. The results of experimental investigations of samples in the form of cubes on compressive strength and samples in the form of prisms on bending strength under different hardening conditions and at different water-cement ratios are presented. Selection of hardening conditions of concrete on sulphate-resistant slag Portland cement was made based on achievement of quality indicators no worse than in concrete on Portland cement. The expediency of introducing into the concrete organic surface-active additives - lignosulfonates in order to achieve the required strength is grounded. It is proved experimentally that the proposed concrete has sufficient frost resistance.