Fluidity Properties Research Articles

Effect of Water-Reducing Admixtures Having Hybrid Silicon Air-Entraining Surfactants on Some Properties of Concrete Mixtures

In order to improve the fresh properties and freeze-thaw resistance of cementitious systems, water-reducing and air-entraining admixtures are actively used in concrete mixtures. Generally, these mentioned admixtures are added to concrete mixtures as two separate admixtures. In this case, when the properties/compositions of one of the admixtures change, compatibility problems of admixtures may occur with each other or with the cement, and the fresh/hardened properties of the concrete may be adversely affected. In this study, a modified water-reducing admixture with both fluidity and air-entraining properties was produced. The utilization effect of high-range water-reducing admixtures (HRWR) having different ethylene oxide/propylene oxide (EO/PO)–based air-entraining surfactants (AES) on some properties of concrete mixtures was investigated. For this purpose, firstly, hybrid silicone AESs with a silicon content of 20%, 33%, and 38.5% were supplied. Then, HRWRs containing seven different AES were produced by using substitution and synthesis methods. In HRWRs produced by the substitution method, 3 and 5 wt. % of HRWR were substituted with EO/PO-based hybrid silicon AES. In the other method, EO/PO-based hybrid silicon air-entraining macromonomers were bonded to the HRWR at ratios of 1, 3, and 5 wt. % during its synthesis process. Replacing HRWR with hybrid silicone AESs increased admixture demand to provide the target slump value in concrete mixtures. Utilization of AESs containing 20% and 33% silicon in HRWR by the substitution method positively affected the permeability and compressive strength of concrete mixtures, while the rise of this ratio to 38.5% by using the synthesis method did not affect them significantly. The presence of surfactant with 20% silicon in 3% and 5% of the admixture and with 33% silicon in 5% of the admixture positively affected frost resistance of concrete mixtures. However, the use of surfactants with 33% silicon content in 3% of the admixture and 38.5% silicon in 1%, 3%, and 5% of the admixture showed a negative effect on the frost resistance of the mixtures.

Analysis of structural transformations occurring during thermal hardening of building reinforcing steel produced at Baku Steel Company LLC

For the production of building reinforcing steel, special charge components were used, consisting of steel waste, cast iron shavings and about 20 % of NVG pellets. Steel was smelted in a 60-ton electric arc furnace. The pouring of liquid steel was carried out on a continuous casting machine. Heat treatment was carried out immediately after the rolling operation to improve the physical and mechanical properties of the construction reinforcing steels melted in the electric arc furnace from the charge material using metal waste. It is recommended that these steels be made of low-carbon (C≤0.25 %) and low-alloy steels in order to have a sufficiently high technology and good weldability. However, in order to meet the requirements of construction standards, these steels must have high structural integrity and physical and mechanical properties. It was found that these requirements can be solved only by heat treatment immediately after the rolling operation of the armature. In this case, the effect can be obtained by reinforcing heat treatment of the fittings by hardening due to the rolling temperature. Therefore, in order to further improve the properties during thermomechanical treatment (TMT), the hardening was carried out directly (immediately) after the deformation in the roll. Immediately after the spread, the physical and mechanical properties, as well as the fluidity and strength properties of the construction low-carbon reinforcement steels met the requirements of the standard by conducting HTMT. Increased strength and technological properties of reinforcing steel are achieved after hardening by dispersion hardening at high-temperature tempering, which is carried out at a temperature of more than 580 °C

Effect of Chlorine on the Fluidity and Thermal Stability Properties of High-Titanium Slags

Effect of Chlorine on the Fluidity and Thermal Stability Properties of High-Titanium Slags

In situ 3D bioprinting with bioconcrete bioink

In-situ bioprinting is attractive for directly depositing the therapy bioink at the defective organs to repair them, especially for occupations such as soldiers, athletes, and drivers who can be injured in emergency. However, traditional bioink displays obvious limitations in its complex operation environments. Here, we design a bioconcrete bioink with electrosprayed cell-laden microgels as the aggregate and gelatin methacryloyl (GelMA) precursor solution as the cement. Promising printability is guaranteed with a wide temperature range benefiting from robust rheological properties of photocrosslinked microgel aggregate and fluidity of GelMA cement. Composite components simultaneously self-adapt to biocompatibility and different tissue mechanical microenvironment. Strong binding on tissue-hydrogel interface is achieved by hydrogen bonds and friction when the cement is photocrosslinked. This bioink owns good portability and can be easily prepared in urgent accidents. Meanwhile, microgels can be cultured to mini tissues and then mixed as bioink aggregates, indicating our bioconcrete can be functionalized faster than normal bioinks. The cranial defects repair results verify the superiority of this bioink and its potential in clinical settings required in in-situ treatment.

Novel recycling application of high volume municipal solid waste incineration bottom ash (MSWIBA) into sustainable concrete

Since municipal solid waste incineration bottom ash (MSWIBA) contains some heavy metals that are harmful to the groundwater and soil, this study proposes an effective and new approach to deal with high-volume MSWIBA. Selecting 70% MSWIBA, 10% ordinary Portland cement (OPC), 10% fly ash/ground granulated blast furnace slag (FA/GGBFS), and 1% volume of polypropylene (PP) fiber as the raw materials, this project designed and manufactured cold-bonded fiber aggregates (CBFAs) and applied them into sustainable concrete. It was found that the water absorption of CBFAs was between 12 and 14%, the bulk density was between 900 and 1100 kg/m3, and the compressive strength of single particle was greater than 1.8 MPa. And it was found that the mechanical strength and bulk density of CBFAs were positively correlated, while the mechanical strength and water absorption were negatively correlated. The leaching behaviors of CBFAs on Cu, Pb, Cd, and Cr were successfully suppressed to less than 1% of that originally from MSWIBA, which can be in line with the Chinese standards. Additionally, it is also found that the green concrete with adding GGBFS-CBFAs has higher overall fluidity and better mechanical properties than the concrete with FA-CBFAs. The mechanical properties of concrete were the best under the replacement rate of 60% of CFBAs, and the strength of green concrete added with GGBFS-CBFAs reached 96% of that of ordinary concrete. In this study, the rapid chloride ion penetration test, mercury intrusion and electron microscope tests found that the bonding effect between the CBFAs and the green concrete matrix was better, and the pore structure in the transition zone of the surrounding interface was refined. The proportion of transition pores in the pore structure was up to 59%. This shows that the concrete added with CBFAs has better resistance to chloride ion diffusion, and has some improvement on the durability. This research suggests that CBFAs including high volume MSWIBA has the potential to be successfully applied as the alternative to natural aggregates in sustainable concrete, and this can also advance waste recycling, and solidify high volume heavy metals in infrastructures.

Experiment on the Properties of Soda Residue-Activated Ground Granulated Blast Furnace Slag Mortars with Different Activators.

Soda residue (SR), a solid waste generated in the production of Na2CO3 during the ammonia soda process, with a high pH value of 12, can be used as an activator of alkali-activated ground granulated blast furnace slag (GGBFS) cementitious materials. Three groups of experiments on SR-activated GGBFS mortars were designed in this paper to assess the role of the dominant parameters on fluidity and compressive strength of mortars. The results indicate that for fluidity and mechanical properties, the optimal scheme of SR-activated GGBFS mortars is 16:84–24:76 S/G, 0.01 NaOH/b, 0.05 CaO/b, and 0.50 w/b, with fluidity and compressive strength (28 d) of the mortars being 181–195 mm and 32.3–35.4 MPa, respectively. Between 2.5–10% CaCl2 addition to CaO (5%)-SR (24%)-activated GGBFS mortar is beneficial to the improvement of the compressive strength of C2, whereas the addition of CaSO4 is harmful. The main hydration products of mortars are ettringite, Friedel’s slat, and CSH gels. The results provide a theoretical basis and data support for the utilization of SR.

Study on the preparation of cementitious grout for grout sleeve splicing of rebars based on a ternary composite material system

In this study, through orthogonal experiments, a ternary composite material system of sulfoaluminate cement, Portland cement and gypsum with optimal proportions was developed for preparing cementitous grout for rebar sleeve splicing. The main factors affecting the performances of the grout were investigated. Also, the influences of water/binder ratio, Portland cement/sulphoaluminate cement ratio and gypsum content on the properties of the grout were studied. The experimental results show that: (1) The factors affecting the fluidity and compressive strength of the cementitious grout in order that from significant to non-significant were water/binder ratio, Portland cement/sulphoaluminate cement ratio and gypsum content. (2) To obtain comprehensive properties of good compressive strength and fluidity, it seems that the optimal ratio of the Portland cement to sulphoaluminate cement is 8:2. At this ratio, 1d compressive strength and 3d compressive strength were 35.7 MPa, 61.7 MPa, respectively, and the initial fluidity was 335 mm. (3) Gypsum is the main factor affecting the vertical expansion rate of the cementitious grout among the factors studied. The compressive strength and vertical expansion rate of cementitious grout both grew as the increase of gypsum content (from 0% to 3%), but the compressive strength experienced a drop, when the gypsum content even exceeds 3%.

Synergistic effect of surfactant and chlorine salt on dispersion of nano-SiO2 and performance of cement-based grout containing a large amount of bentonite

Nano-SiO2 (NS) is widely used to improve the performance of cement-based grouts. The workability and mechanical property of grouts are greatly affected by NS dispersion. In this paper, synergistic effect of surfactants and chloride salts on NS dispersion, as well as on performance of grouts including fluidity, mechanical and microscopic properties were systemically studied. The results showed that the synergistic effect of anionic surfactant (SDS) and chloride salt can effectively improve NS dispersion because of the massive formation of micelles that can encapsulate NS and the electrostatic repulsion between micelles. And the effect of CaCl2 was more significant than NaCl. Furthermore, fluidity of fresh slurry and mechanical property of hardened grouts were also improved by the synergistic effect. The mechanical property enhancement might be attributed to the filling effect of NS due to its improved dispersion, and to the matrix compaction associated with the formation of strätlingite and Friedel's salt.

Kinetics of heavy oil non-catalytic aquathermolysis with and without stoichiometric coefficients

The aquathermolysis process is considered an efficient method to improve fluidity properties in-situ and increase the degree of oil extraction (recovery factor) from downhole hard-to-recover reserves. In this work, the effect of using stoichiometric coefficients during the kinetic modeling of the aquathermolysis process has been studied. The parameters of two kinetic models based on SARA fractions and gas production were determined. The estimation of kinetic coefficients was carried out through a series of numerical methods and statistical analysis to guarantee that the calculated values provide the lowest average absolute error with respect to experimental data. A series of aquathermolysis tests was carried out in a batch reactor in a temperature range of 250–300 °C and reaction times of 12–72 h. The results of both kinetic models are in good agreement with experimental data with an error lower than 5%.

Rheological Properties of Cement Paste Containing Ground Fly Ash Based on Particle Morphology Analysis

Separating finer particles from raw fly ash is a popular method to produce high-performance admixture of concrete. However, the supply of separated fly ash is obviously behind the demand and the residue fly ash is difficult to be disposed. Ground fly ash is another method to improve the particle size and reactivity, but the change of particle morphology during grinding may affect the rheological properties of cement paste and concrete, which limits the application of ground fly ash in concrete projects. In this study, the raw fly ash, separated fly ash, and ground fly ash of the same particle size range were studied and the particle morphology was analyzed by Image-Pro Plus process and spherical particles proportion calculation. On this basis, the fluidity and rheological properties of cement paste with different fly ash content were tested and the mechanism was discussed by packing density and zeta potential analysis. The results showed that the total amount of spherical particles in fly ash-cement paste system was reduced due to the spherical particles of ground fly ash being destroyed during the grinding process. Thus, compared with the separated fly ash of similar particle size range, the fluidity of ground fly ash was significantly decreased while the yield stress and plastic viscosity increased significantly, which indicated that the rheological properties of fly ash cement paste are closely related to the particle morphology of fly ash. The results provide theoretical basis and technology support to the application of ground fly ash.

Eco-friendly treatment for MSWI bottom ash applied to supplementary cementing: Mechanical properties and heavy metal leaching concentration evaluation

This paper reports a green method for treating municipal solid waste incineration bottom ash (MSWI-BA, MB), which is named Ce-wet grinding. The MSWI-BA can be used as a part of the cement for construction engineering after this treatment. The effects of wet grinding time on the mechanical properties and fluidity properties of municipal solid waste incineration bottom ash-ordinary portland cement (MB-OPC) were studied. Then the mechanism of heavy metals of toxic leaching concentration and chemical speciation in MSIW-BA was discussed in detail. The test results show that citric acid (CA) and ethylene diamine tetraacetic acid (EDTA) are added in wet grinding water can reduce the content of heavy metals in MSWI-BA. This method reduces the toxic leaching content of heavy metals and improves the solidification effect of cement on heavy metals. In addition, Ce-wet grinding increases the iron-manganese oxide binding state and carbonate bound state of heavy metals, which improves the stability of heavy metals. Ce-wet grinding can also reduce the particle size of MSWI-BA and enhance the mechanical properties of MB-OPC. This study provides an environment friendly idea for the MSWI-BA used as an admixture in cement, and it reduces the pressure of garbage treatment in garbage dumps.

Star-Branched Polyamides as the Matrix in Thermoplastic Composites.

The aim of this study is the preparation of star-shaped branched polyamides (sPA6) with low melt viscosity, but also with improved mechanical properties by reactive extrusion. This configuration has been obtained by grafting a tri-functional, three-armed molecule: 5-aminoisophthalic-acid, used as a linking agent (LA). The balance between the fluidity, polarity and mechanical properties of sPA6s is the reason why these materials have been investigated for the impregnation of fabrics in the manufacture of thermoplastic composites. For these impregnation processes, the low viscosity of the melt has allowed the processing parameters (temperature, pressure and time) to be reduced, and its new microstructure has allowed the mechanical properties of virgin thermoplastic resins to be maintained. A significant improvement in the ultrasonic welding processes of the composites was also found when an energy director based on these materials was applied at the interface. In this work, an exhaustive microstructural characterization of the obtained sPAs is presented and related to the final properties of the composites obtained by film stacking.

Green and Environmental Protection Recycled Concrete in Road Engineering

In response to a series of national strategic guidelines for green and sustainable development, recycled concrete is used as a recyclable resource. First, the mechanical properties, workability, and durability of recycled concrete are briefly introduced, and the benefit and necessities of research on recycled concrete are described from environmental, economic, and social perspectives. Second, the mixing method and molding process of recycled concrete are described in detail, and the influence of vibration molding and compression molding on the performance of recycled concrete is analyzed. It is found that the compressive strength first increases and then decreases with the increase of molding pressure. In addition, porosity decreases as molding pressure build-up. Therefore, it is recommended that the molding pressure of recycled concrete be generally controlled between 600 and 800 N. Then, the influence of the water-cement ratio on recycled concrete’s fluidity and mechanical properties is discussed. It is found that with the increase of the water-cement ratio, the compressive strength first increases and then decreases and the optimum water-cement ratio is proposed to be 0.2. Finally, the application status and problems of recycled concrete in road engineering are briefly described, and relevant suggestions for construction technology are put forward. Based on the fire safety and reliability requirements of concrete structures, the performance of high-performance concrete structures after fire can be restored to the initial level or even improved through the processes and measures of building structure design, repair, and reinforcement; the strength and crack healing of high-performance concrete after fire can be gradually restored by applying or soaking repair agent and water curing; the recovery of pH value of concrete after fire and the reduction of carbonation depth can be realized by using electrochemical realkalization technology; using carbon fiber to strengthen the components after fire can restore the bearing capacity, but the degree of stiffness recovery is low; and beam side steel plate reinforcement and steel bonding reinforcement can realize the recoverability of bearing capacity, stiffness, and ductility of members after fire.

Hydrophobic Chitosan Nanoparticles Loaded with Carvacrol against Pseudomonas aeruginosa Biofilms.

Pseudomonas aeruginosa infections have become more challenging to treat and eradicate due to their ability to form biofilms. This study aimed to produce hydrophobic nanoparticles by grafting 11-carbon and three-carbon alkyl chains to a chitosan polymer as a platform to carry and deliver carvacrol for improving its antibacterial and antibiofilm properties. Carvacrol–chitosan nanoparticles showed ζ potential values of 10.5–14.4 mV, a size of 140.3–166.6 nm, and an encapsulation efficiency of 25.1–68.8%. Hydrophobic nanoparticles reduced 46–53% of the biomass and viable cells (7–25%) within P. aeruginosa biofilms. Diffusion of nanoparticles through the bacterial biofilm showed a higher penetration of nanoparticles created with 11-carbon chain chitosan than those formulated with unmodified chitosan. The interaction of nanoparticles with a 50:50 w/w phospholipid mixture at the air–water interface was studied, and values suggested that viscoelasticity and fluidity properties were modified. The modified nanoparticles significantly reduced viable P. aeruginosa in biofilms (0.078–2.0 log CFU·cm−2) and swarming motility (40–60%). Furthermore, the formulated nanoparticles reduced the quorum sensing in Chromobacterium violaceum. This study revealed that modifying the chitosan polarity to synthesize more hydrophobic nanoparticles could be an effective treatment against P. aeruginosa biofilms to decrease its virulence and pathogenicity, mainly by increasing their ability to interact with the membrane phospholipids and penetrate preformed biofilms.

Influence of dipotassium hydrogen phosphate on properties of magnesium potassium phosphate cement

Magnesium potassium phosphate cement (MKPC) is usually prepared from dead burned magnesia (MgO) and potassium dihydrogen phosphate (KH2PO4, KDP). Here, MKPC was produced by mixing KDP and dipotassium hydrogen phosphate trihydrate (K2HPO4·3H2O, DKP) as phosphates. To study the influence of DKP on the hydration process and hardening, pH values, wettability between magnesia and initial solutions, hydration temperature development, initial setting time, fluidity, hydration products, and mechanical properties were measured. The results show that the decrease in the ratio of KDP to DKP leads to an increase in pH and a decrease in wettability, resulting in changes in the hydration process. In addition, setting behavior is also influenced by the ratio of KDP to DKP. When KDP/DKP＞2:1, as the ratio becomes smaller, the initial setting time gets shorter; otherwise, the opposite is true. These differences are attributable to the temperature change during the reaction, the distinction in wettability, and the different pH caused by the various ratios of KDP to DKP. Moreover, XRD analysis shows that the hydrated products are still MgKPO4·xH2O (x = 1 or 6), indicating that hydration products are basically unaffected. TGA analysis signifies that the amount of hydrated products in MKPC is responsible for the changes in the mechanical properties.

Influence of Fine Aggregate Characteristics on Fluidity and Mechanical Properties of Air Entrained Wet Shotcrete

Influence of Fine Aggregate Characteristics on Fluidity and Mechanical Properties of Air Entrained Wet Shotcrete

Optical Membrane Control with Red Light Enabled by Red-Shifted Photolipids.

Photoswitchable phospholipids, or "photolipids", that harbor an azobenzene group in their lipid tails are versatile tools to manipulate and control lipid bilayer properties with light. So far, the limited ultraviolet-A/blue spectral range in which the photoisomerization of regular azobenzene operates has been a major obstacle for biophysical or photopharmaceutical applications. Here, we report on the synthesis of nano- and micrometer-sized liposomes from tetra-ortho-chloro azobenzene-substituted phosphatidylcholine (termed red-azo-PC) that undergoes photoisomerization on irradiation with tissue-penetrating red light (≥630 nm). Photoswitching strongly affects the fluidity and mechanical properties of lipid membranes, although small-angle X-ray scattering and dynamic light scattering measurements reveal only a minor influence on the overall bilayer thickness and area expansion. By controlling the photostationary state and the photoswitching efficiency of red-azo-PC for specific wavelengths, we demonstrate that shape transitions such as budding or pearling and the division of cell-sized vesicles can be achieved. These results emphasize the applicability of red-azo-PC as a nanophotonic tool in synthetic biology and for biomedical applications.

Study on the Influence of Silica Fume (SF) on the Rheology, Fluidity, Stability, Time-Varying Characteristics, and Mechanism of Cement Paste.

In this study, the rheology, fluidity, stability, and time-varying properties of cement paste with different substitute contents of silica fume (SF) were investigated. The result showed that the effects of SF on macro-fluidity and micro-rheological properties were different under different water–cement ratios. The addition of SF increased the yield stress and plastic viscosity in the range of 2.61–18.44% and 6.66–24.66%, respectively, and reduced the flow expansion in the range of 4.15–18.91%. The effect of SF on cement paste gradually lost its regularity as the w/c ratio increased. The SF can effectively improve the stability of cement paste, and the reduction range of bleeding rate was 0.25–4.3% under different water–cement ratios. The mathematical models of rheological parameters, flow expansion, and time followed the following equations: τ(t) = τ0 + k0t, η(t) = η0eat, and L(t) = L0 − k1t, L(t) = L0 − k1t − a1t2. The SF slowly increased the rheological parameters in the initial time period and reduced the degree of fluidity attenuation, but the effect was significantly enhanced after entering the accelerated hydration period. The mechanism of the above results was that SF mainly affected the fluidity and rheology of the paste through the effect of water film thickness. The small density of SF particles resulted in a low sedimentation rate in the initial suspended paste, which effectively alleviated the internal particle agglomeration effect and enhanced stability. The SF had a dilution effect and nucleation effect during hydration acceleration, and the increase of hydration products effectively increased the plastic viscosity.

Blubber fatty acid compositions in different geographic populations of finless porpoise in Chinese waters: implications for thermal adaptation

The stratification of blubber fatty acids (FAs) is a widely used strategy in marine mammals and can be influenced by many factors, including their diet, environmental temperature, and physiological status. There are 3 distinct finless porpoise species/subspecies in Chinese coastal and inland waters in a wide range from 20°N to 40°N. The biochemical stratification of the blubbers of finless porpoises in different regions may provide valuable information for understanding their environmental adaptations. The FA compositions of 4 geographic populations of finless porpoise (FP) collected from the Bohai Gulf, East China Sea, South China Sea, and Yangtze River were therefore analyzed and compared. The blubber FA compositions of finless porpoises were dominated by ΣMUFAs, followed by ΣSFAs and ΣPUFAs, and were generally consistent with those of other cetaceans. The blubber of finless porpoises was significantly stratified with increasing levels of ΣMUFAs and decreasing levels of ΣSFAs and ΣPUFAs from the inner to the outer layers. The 3 marine populations shared more similarities in their FA compositions and stratifications compared to the freshwater porpoises, particularly regarding the PUFAs in the inner layers, which might have been mainly influenced by the diet compositions of marine and freshwater porpoises. Contrary to what was expected, in the 3 marine populations, the SFA and MUFA levels showed opposite correlations (negative and positive, respectively) with habitat temperatures, possibly indicating an adaptation mechanism in finless porpoises characterized by a trade-off between the insulation and fluidity properties of the blubber through the adjustment of the compositions and gradients of MUFAs and SFAs across the blubber depth in response to environmental temperature/latitude changes.

Analysis, Development, and Scaling-Up of Poly(lactic acid) (PLA) Biocomposites with Hazelnuts Shell Powder (HSP).

In this work, two different typologies of hazelnuts shell powders (HSPs) having different granulometric distributions were melt-compounded into poly(lactic acid) (PLA) matrix. Different HSPs concentration (from 20 up to 40 wt.%) were investigated with the aim to obtain final biocomposites with a high filler quantity, acceptable mechanical properties, and good melt fluidity in order to be processable. For the best composition, the scale-up in a semi-industrial extruder was then explored. Good results were achieved for the scaled-up composites; in fact, thanks to the extruder venting system, the residual moisture is efficiently removed, guaranteeing to the final composites improved mechanical and melt fluidity properties, when compared to the lab-scaled composites. Analytical models were also adopted to predict the trend of mechanical properties (in particular, tensile strength), also considering the effect of HSPs sizes and the role of the interfacial adhesion between the fillers and the matrix.