Increasing Alkali Concentration Research Articles

Properties and microstructure evolution of Pisha sandstone after water/alkali leaching

Alkali-activated aluminosilicate minerals for the production of geopolymer building materials provide low-carbon and low-energy advantages compared to OPC. Pisha sandstone (PS) is a mudstone/sandstone rich in silica and aluminium, but it cannot be used directly as an engineering material due to the expansion of soggy clay minerals. In this study, the PS was modified via water and alkali leaching pretreatments, and the modified PS was used to investigate the feasibility of eliminating or attenuating the swelling of montmorillonite, and the alkali activation behavior of the PS system, respectively. The stirring frequency, dosage and types of leaching agent, and leaching time were considered as the variables. The ion concentration of the leachate was characterized using an inductively coupled plasma mass spectrometer (ICP-MS). The modified and untreated PS were characterized using a range of analytical techniques, including particle size analysis, powder XRD, SEM/EDX, TGA, and its free swelling volume in water, as well as the mechanical properties of the specimens prepared as cylinders. The results show that water leaching reduces the particle size of PS, diminishes the span of its particle size distribution, and decreases the relative amount of montmorillonite in PS. Montmorillonite undergoes dissolution/ion exchange under alkali leaching. With increasing alkali concentration and leaching time, the phase changes from Ca-montmorillonite to Na-montmorillonite to glassy phase silica-aluminate. The amorphous N-A-S-H and C-A-S-H coexist in the system, N-A-S-H is the major hydration product. PS is still classified as a material with low pozzolanic activity, as the amount of geopolymer produced in the system is very low. The degree of water-absorption swelling and cracks on the specimen surface induced by the ASR gel deepened with increasing alkali concentration. The involvement of reactive Al and reactive Ca converted the ASR gels into (N,C)-A-S-H gels or C-(A)-S-H gels, which depended on the atomic ratios of these reactive ions, and significantly improved the strength and water resistance of the specimens.

Alkaline-oxidized MXene composite membrane of ultra high flux and advanced rejection performance for water purification

MXene is a metal-carbon/nitrogen compound material with a two-dimensional layered structure. As a new form of two-dimensional material, it has great potential in the field of water purification because of its properties of high permeability and hydrophilicity. In this study, a MXene composite membrane was prepared by in-situ oxidation of titanium dioxide on the MXene surface by an alkaline oxidation method. A series of characterizations of the prepared MXene composite membrane was carried out. Scanning electron microscopy showed that with an increasing degree of oxidation, the extent of agglomeration of MXene nanosheets increased, thus generating more water channels that are conducive to the transport of water molecules, and an increasing water flux. The penetration performance, interception performance, and stability of the MXene composite membrane were tested. The effect of different concentrations of KOH on the properties of the composite membrane was investigated. It was found that the flux of the composite membrane increased with alkali concentration by 4.6–28.8 times the flux without exposure to alkali. It was found that the rejection rate of the composite membrane for pollutants (dyes, humic acid, bovine serum albumin protein) decreased only slightly with increasing alkali concentration, and was ≥94% of the pure MXene membrane rejection rate in all cases. The rejection performance of the composite membrane was related to the size and charge properties of the pollutant molecules. The results of the stability tests showed that the composite membranes had a high degree of physical and flux stability in a range of aqueous solutions.

Alkali treatment of maize bran affects utilization of arabinoxylan and other non-digestible carbohydrates by the human gut microbiota in vitro in a dose-dependent manner

Alkali treatment of maize bran can break ferulate cross-linking and increase utilization of alkali-solubilized arabinoxylan (AX) by the human gut microbiome. However, it is not known how alkali treatment affects the utilization of AX and other non-digestible carbohydrates (NDC) that remain insoluble after alkali treatment, or how varying degrees of alkali treatment affect NDC fermentation. Therefore, maize bran was treated with alkali ranging from 0 to 1.25 M NaOH, neutralized, and then subjected to in vitro digestion and fermentation using human fecal microbiomes. Increasing alkali concentration progressively increased water solubility of NDC, especially AX, and increased microbial fermentation of water-soluble AX (p < 0.001) during fermentation; however, there was a decrease in fermentation of insoluble AX and NDC (p < 0.001). Across microbiomes, more acetate (p = 0.004) and propionate (p = 0.018), but less butyrate (p < 0.001), were produced as alkali treatment of maize bran increased. Higher alkali treatments increased the abundances of Bifidobacterium (q < 0.001), Bacteroides (q = 0.0015), Faecalibacterium (q < 0.001), and several genera in the Bacilli class (q < 0.001), while decreasing Bilophila (q < 0.001), Butyricicoccus (q < 0.001), and several Lachnospiraceae (q < 0.001). Soluble but not insoluble NDC utilization was improved by extracting residual free phenolic compounds from alkali-treated maize bran (p = 0.005 and p = 0.39, respectively). In conclusion, alkali makes maize bran AX more water soluble and fermentable, but it has a negative impact on insoluble AX and NDC utilization, which reduces butyrate production by the microbiome due to decreases in Butyricicoccus and some Lachnospiraceae.

Optimization of the novel jute retting process to enhance the fiber quality for textile applications

This study introduces an innovative chemical retting approach, systematically optimized via Grey relational analysis, to achieve jute fibers that exhibit desirable characteristics of softness, high tensile strength, and suitability for spinning, with a particular focus on their application in the apparel industry. In this study, the effect of alkali treatment (alkali concentration, temperature and duration of retting) on jute fiber's chemical composition and mechanical characteristics was investigated. Jute fibers were treated at three concentrations (5 %, 10 %, 15 %) of alkali, at three different temperature (30 °C, 60 °C, & 90 °C) and for three different retting duration (12 h, 24 h, & 36 h). The surface morphology and crystallinity of fibers were analyzed using optical microscopy, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The fiber linear density and mechanical characteristics were also tested. The multi-response optimization of all the factors and the responses was investigated using the Grey relational analysis. The results showed that the fiber surface morphology and crystallinity increase with an increase in alkali concentration, retting time, and temperature. Chemical retting treatment also improved the fiber linear density and tensile strength. The finest fibers which were obtained in this research had a linear density of 2.18 Tex with a tenacity of 53.02 cN/tex and elongation of 4.54 %. The spinnable jute fibers were achieved after this treatment with excellent characteristics.

The effect of alkali treatment on the mechanical properties of date seed particulates waste polypropylene filled composites

Date seeds collected as waste were reduced to 63 µm particles and treated with NaOH (aq) at 1, 3, 5, 7 and 10 %. The extent of chemical modification was assessed using FTIR analysis. The waste polypropylene (wPP)/date seed particles (DSP) composites filled with untreated and treated particles at 20 % filler loadings were fabricated using compounding and compression moulding techniques by means of two rolls mill. Tensile, flexural, impact tests and hardness (HV) were conducted and evaluated. Subsequently, a morphological study of the fractured surface of the composites was achieved using SEM. The application of alkali treatment enhanced various properties of the composites at the optimal concentration of 10 % w/v. Specifically, the tensile strength, flexural strength, elongation at break, impact strength, and hardness were improved, resulting in values of 28.86 MPa, 140 MPa, 172.5 %, 0.92 J/m², and 23.8 Hv, respectively. While tensile and flexural moduli showed a decrease with increasing alkali concentration. The SEM of the fractured surface of the treated composite revealed a better dispersion of filler particles within the matrix with no cluster seen compared to the untreated.

The mechanism of alkali-induced rice protein gel formation: Effect of alkali concentration and temperature

Rice protein (RP) is a high-quality hypoallergenic plant protein, but its extremely poor water solubility makes it difficult to be applied in liquid food systems. Therefore, in-depth exploration of its gel properties is an effective way to broaden the application scenarios of RP. In this work, it was first found that the rate and strength of gel formation by RP at 25 °C strongly depended on the increase in alkali concentration (from 0.05 M to 0.125 M), i.e., alkali concentrations above 0.075 M were sufficient to induce the formation of a stable gel by 10% (w/v) of RP in 0.5 h. Increasing the temperature during alkali-induced RP gel formation (50 °C, 80 °C) greatly increased the rate of gel formation, whereas prolonged (>30 min) heat treatment resulted in liquefaction of the gel. A more in-depth analysis revealed that the alkali was able to depolymerize glutelin within the agglomerates in its native state, thereby forming a gel network among glutelin molecules at lower alkali concentrations (CNaOH = 0.075 M) mainly through hydrophobic interactions. Whereas, higher alkali concentration (CNaOH = 0.125 M) resulted in the rapid transformation of exposed free sulfhydryl groups into disulfide bonds, thus exerting a major contribution to the gel network, followed by hydrogen bonding. Furthermore, the phenomenon of heat-induced gel liquefaction was mainly attributed to the dissociation of glutelin subunits and was accompanied by an increase in the disordered structure of proteins in the amide III region. These findings may provide a scientific basis for the development of rice protein gel foods.

Tensile Behaviors of Textile Grid–Reinforced Engineered Geopolymer Composites

This paper presents a study of the tensile behaviors of textile grid–reinforced engineered geopolymer composites (TR-EGCs) using both experimental and numerical methods. EGC is a novel ecofriendly fiber-reinforced geopolymer composite that exhibits ultrahigh ductility under tensile loading conditions. In this paper, the ambient cured EGC with local polyvinyl alcohol (PVA) fiber was designed and the mechanical behaviors of the EGC were investigated. Direct tensile tests of TR-EGC specimens were conducted and compared with those of conventional textile-reinforced mortar (TRM). It was found that the load-carrying capacity of TR-EGC with carbon fabric was 5.72 times greater than that of TRM. The influences of alkali concentrations and textile types on the tensile behaviors of TR-EGC are discussed. It was found that the increase of alkali concentration is beneficial to the tensile strength of EGC and TR-EGC. In contrast, the tensile ductility decreased gradually as the alkali concentration increased from 4 to 12 mol/L. A finite-element (FE) model is proposed to model the tensile behaviors of TR-EGC specimens, which was verified using the experimental results. Because the current calculation method significantly underestimated the composite behaviors of the EGC and the inner textile, a new calculation method is proposed. It was found that the proposed calculation method is more accurate in predicting the tensile load–carrying capacity of TR-EGC, although more experiments and numerical analyses with in-depth discussions still need to be conducted.

The correlation between Al incorporation and alkali fixation by calcium aluminosilicate hydrate: Observations from hydrated C3S blended with and without metakaolin

This study aims to investigate the correlation between Al incorporation and Na fixation by C-(A)-S-H, which was derived from hydrated C3S blended with and without 10 wt% metakaolin at 1, 2, and 3 wt% Na2O content. C-(A)-S-H compositions were calculated based on mass balance method. NMR was used to calculate the fraction of different coordinations of Si and Al in C-(A)-S-H. Results show that the incorporation of Al into C-S-H enhances the polymerization of silicate chains, it also increases the Ca/Si of the formed C-A-S-H because more Ca ions are required to stabilize the incorporated Al(VI). The increased Ca/Si subsequently decreases the alkali fixation capacity of C-A-S-H compared to that of C-S-H. Increasing alkali concentration favors the polymerization of C-A-S-H by incorporating more Al(IV) in bridging sites and shows less effect on Al(VI)/Si and Ca/Si due to the different negative charges and calcium coordination environment regarding Al(VI) and Al(IV).

籾殻灰を用いた多孔質ジオポリマー硬化体の作製とその評価

Rice husk is a byproduct of rice production. Appropriate burning the husk produces the rice husk ash containing amorphous silica as a main component. Currently, the ash is expected as a biomass resource. In the present study, the rice husk ash was used to prepare potassium silicate solution. Geopolymer materials were synthesized by a reaction between the potassium silicate solution and metakaolin. In addition, Si powder and a dispersing agent were added to the geopolymer precursor paste to prepare a porous material, and its applicability as a heat insulating material was investigated. Assuming application to heat insulating materials, the effects of alkali concentration in the potassium silicate solution on the curing rate and density were investigated, and the thermal conductivity properties were evaluated. As a result, the curing rate of the geopolymer precursor increased with increasing alkali concentration of the potassium silicate solution. As the concentration increased, in addition, the bulk density and the thermal conductivity decreased. It was found that the heat insulation performance of the porous geopolymer is controlled by adjusting the alkali concentration in the potassium silicate solution.

Characterization of microfibers released from chemically modified polyester fabrics — A step towards mitigation

Synthetic textiles are one of the significant contributors to microfiber pollution, a subclass of microplastics. The impact of microfibers on the environment is irreversible. Several attempts were made to mitigate and control the microfiber release from synthetic textiles by introducing filters and laundry aids in washing machines, whereas some came up with methods to modify the textile materials to release fewer fibers. Studies have related different textile properties with their microfiber release potential. However, moisture properties, one of the essential properties that determine comfort, are not well explored. Hence, this research attempted to mitigate the microfiber release by altering the hydrophilicity of the polyester fabrics through chemical treatment (sodium hydroxide) with the hypothesis that hydrophilicity reduces the microfiber release. Both woven and knitted polyester fabrics were treated with different concentrations of the alkali solution (0.25 M, 0.50 M, 0.75 M, 1.00 M) and evaluated for their microfiber release. Treated fabrics also showed variations in their moisture and physical properties. Woven fabrics showed reduced shedding compared to knitted fabrics due to their compact structure. The results showed that the increase in alkali concentration significantly reduced the microfiber release up to 89.6 % reduction with woven fabric (from 17.37 ± 1.55 fibers/sq.cm to 2.63 ± 0.23 fibers/sq.cm) and a reduction of 68 % was noted for knitted fabric treated with 0.75 M alkali concentration (from 24.38 ± 1.30 fibers/sq.cm to 8.74 ± 1.39 fibers/sq.cm). A higher negative correlation (r = 94 % for woven and 89 % for knitted) was noted between alkali concentration and microfiber release. The alkali treatment significantly reduced the average fiber length from 450 to 230 μm, and 63–93 % of the fibers identified were in size range of 100–500 μm. When the moisture properties of the alkali-treated fabrics are concerned, an increase in moisture properties reduces the microfiber release. Water contact angle and absorbency time positively correlated with microfiber release. However, the study did not show any significant effect of moisture regain percentage and vertical wicking on microfiber shedding. Except for abrasion resistance, the physical properties of alkali-treated fabric did not show any relationship with microfiber release. The study noted the order of factors influencing the microfiber release of polyester fabric as fabric structural parameters (Woven/Knits) > fabric hydrophilicity > fabric physical property.

Xylan extraction from hardwoods by alkaline pretreatment for xylooligosaccharide production: A detailed fractionation analysis

In the last decades, the production of value-added products from lignocellulosic biomass (LCB) has gained relevance. Xylans, which are the main hemicellulose compounds in LCB, may be extracted by alkaline pretreatment and employed for xylooligosaccharide (XOS) production. However, xylan extraction currently works as a black box due to the lack of characterization of the involved streams. Therefore, the appropriate operational conditions often remain unclear, especially in hardwoods. In this study, alkaline/thermal pretreatments at different operational conditions were evaluated for xylan extractions from Chilean Nothofagus species sawdust, determining the chemical compositions of the fractions at each step of the process. Results indicated that increasing alkali concentration (NaOH) leads to a higher xylan extraction, but also to high salt production during the acid neutralization step, decreasing xylan's purity and therefore XOS production. In this context, decreasing NaOH concentration and neutralizing it by membrane filtration, allow extracting xylans (62.5 %) of higher-purity (77 %).

Triaxial test and microstructure analysis of soil from alkali contaminated sites

The protection of site cultural relics is facing great challenges of site soil instability and contamination. Targeting at the special geological environment of Kaifeng region, the affecting laws of different concentrations of alkali on mechanical properties of site soil in this region are studied in this paper. The triaxial test is conducted to study the mechanical properties of site soil, including its failure pattern, stress-strain relationship, stress path and strength index, etc. The X-ray diffraction test and scanning electron microscope test are used to analyze the composition, particle state, and pore characteristics of the soil before and after contamination, and to evaluate the stability of the site soil. At the site combining with microstructure changes and macro mechanical properties. The results show that, from the macroscopic surface, with the increase of alkali concentration, the failure shear plane usually appears along the 45° direction. From the perspective of mechanical properties, the stress-strain relationship of the site soil is caused by the strengthening of soil deformation, and the alkali concentration increases, and the curve gradually develops from hardening type to softening type. The stress path is the line connecting the points in the sequence of the stress change process, which is different, and the corresponding soil deformation and strength characteristics will also appear very different. The stress path of soil with different alkali concentration is different. Under the same σ3 condition, the stress σ1 is different. The stress change is expressed in macroscopic terms as different forms of soil damage. Under 0 % concentration, the strength index of soil is 82.14 kPa, 21.67°, and the alkali concentration is 4–16 %, the internal friction Angle is gradually increased, and the cohesion is slightly reduced. From the micro perspective, the main components of the contaminated site soil are SiO2, Al2O3, CaO and Fe2O3. In the process of alkali-soil reaction, alkali reacts with oxides in soil to form Na2AlO2, which has a certain cementation effect. SiO2 reacts with NaOH solution to generate Na2SiO3, which has strong cohesiveness and strength. The newly generated cementing material in the soil increases, and the bonding force between particles increases. In addition, some cements fill the inner pores and improve the shear strength of soil. Under the same pressure, the stress-strain curve of soil gradually developed from hardening type to softening type with the increase of alkali concentration. In the stress-strain curve of soil, with the increase of alkali concentration, the soil reaches the strength at failure under small deformation. The increase of alkali concentration reduces the plasticity and increases the brittleness of soil. At this time, if the stress is localized, shear bands will appear and the stability of soil will decrease. The study of soil properties changes caused by different alkali pollution concentrations can provide a scientific basis for the reinforcement and protection of soil sites or ancient cultural foundations in Kaifeng area.

Synthesis and performance of mesoporous iron oxide in vacuum residue slurry-phase hydrocracking

In order to develop a high-efficiency iron oxide catalyst for the slurry-phase hydrocracking of poor heavy oil, the mesoporous iron oxide was successfully synthesized by using the waste wood powder as a template, and the influence of alkali concentration in the resulting solution on crystal phase, morphology and pore structure of the synthesized samples was investigated. The crystal phase of the synthesized iron oxide transfers from α-Fe2O3 to γ-Fe2O3, and their crystal sizes gradually decrease with an increase of alkali concentration based on the XRD and HRTEM results. Additionally, the iron oxide with mesoporous structure, larger surface area and pore volume is obtained at the higher concentration of alkali in solution confirmed by N2 adsorption-desorption analysis. The assessment result of the iron oxide catalyst employed in the slurry-phase hydrocracking of vacuum residue (VR) illustrates that the yields of gasoline and diesel distillates obtained over Fe-O-B20, Fe-O-B24 and Fe-O-B30 catalysts are higher compared with those over Fe-O-B2 and Fe-O-B14 catalysts, it can be attributed that more exposure Fe active sites derived from their larger surface area and pore volume availably improve the catalyst hydrogenation activity, which can inhibit the over-cracking reaction of intermediate products and the condensation of polycyclic aromatic hydrocarbon in VR to enhance the yields of gasoline and diesel distillates.

Xylene and n-Hexane Adsorption Performance of a Waste Methanol-to-Propylene Catalyst under Acid-Base Treatment

Spent methanol-to-propylene (MTP) catalysts have a large specific surface area and high porosity but are usually directly disposed of in landfills, and recycling is rare. In this study, spent MTP catalyst was moderately dealuminized with acids and etched with an alkali solvent to increase its specific surface area. A novel adsorbent was obtained. XRD, SEM, FT-IR, XRD, XRF, and MAS-NMR characterization shows that the adsorbent maintains a typical ZSM-5 zeolite structure, and the dealumination effect of H2C2O4 is better than that of HCl. HCl mainly removes the framework aluminum of the molecular sieve; H2C2O4 not only removes the framework aluminum but also dissolves some of the nonframework aluminum, which increases the BET-specific surface area and pore diameter. The spent catalyst maintains an irregular ellipsoidal shape. After alkali treatment, the surface of the spherical particles becomes rough. With increasing alkali concentration, the damage degree increases. After treatment with 4 mol/L H2C2O4 and 0.1 mol/L NaOH, the p-xylene and n-hexane adsorption capacities reach the maximum, with values of 141.04 mg/g and 106.87 mg/g, respectively, 20.7% and 16.2% greater than those before treatment. These findings indicate that modified spent MTP catalyst has the potential for application in the removal of VOCs from the air.

Extraction of Chitosan with Different Physicochemical Properties from Cunninghamella echinulata (Thaxter) Thaxter for Biological Applications.

The conventional production of chitosan from crustaceans has many limitations. An attempt was made to optimize chitosan production from fungi. Soil fungi were isolated, identified, and screened for high glucosamine content. Among the fungal isolates tested, Cunninghamella echinulata showed high glucosamine content. The biomass production of C. echinulata was standardized under different growth parameters. The physicochemical characterization of derived chitosan isolates was distinctive and diverged as supported by the FT-IR, molecular mass distribution, degree of deacetylation, and crystallinity. Molecular mass distribution ranged from 1 to 9 mers. The degree of deacetylation was observed to be maximum in C6 (80.88%), which increased with the increase in alkali concentration. In the chitosan isolate, C1 was non-toxic to Vero cells up to 250µg/mL. In the physicochemical and functional properties of chitosan isolate, C1 was found to be unique and diverse; further detailed investigations on this isolate might help to develop some biomaterials with improved biocompatibility.

Study of Alkali Treatment and Its Influence on Characteristics of Borassus Palm Fiber

ABSTRACT Palmyra fibers are found to be the renewable and sustainable fiber in textile applications. These fibers possess good tensile strength and found to be used as a natural reinforcement material for composites. The main objective of this work is to extract and treat the fibers with varying concentrations of NaOH (2%,3%,4%& 5%) to evaluate the mechanical properties, surface morphology, and fiber orientation. The observations in SEM images denote the removal of impurities like hemi cellulose and lignin after the alkali treatment. 4% NaOH-treated fibers results in higher tensile strength (63.43 MPa) and a further increase in alkali concentration to 5% results in a reduction of the tensile strength (62.65 MPa). For all the treated fibers, elongation at break was found to be higher than the untreated one. The orientation in the fiber structure improves after the alkali treatment up to 4% and a further increase in alkali concentration leads to a decrease in the orientation which was observed through X-ray diffraction studies.

Tensile Properties and Fracture Morphology of Acacia Caesia Bark Fibers Treated with Different Alkali Concentrations

ABSTRACT The tensile strength of fibers extracted by retting from Acacia Caesia bark was measured and their fracture morphology was examined, with the idea to propose their potential use as the reinforcement in polymer composites. Four categories of fibers were investigated, namely untreated and treated with a concentration of 5, 10 and 15% sodium hydroxide (NaOH) for 24 hours at ambient temperature. The increase of alkali concentration resulted in a gradual reduction of hemicellulose, wax, and moisture, which on the other side increased the fiber density. Single fiber tensile tests were performed according to ASTM D3822 standard. The fracture surfaces of the fibers were observed using an optical microscope and scanning electron microscope (SEM). The tensile tests revealed that the 10% NaOH treatment sample showed the highest performance, namely an average tensile strength of 16.2 (±5.63) N with an ultimate elongation of 4.6 (± 1.0)%. SEM evidenced the different possible morphologies of Acacia Caesia bark fiber fractures, including sliding and tearing, splitting and torsion of fibrils.

Effect of alkali treatment on the mechanical properties and water resistance of bamboo scraps/magnesium oxychloride composites

Alkali treatment of bamboo scraps was adopted to improve the interface compatibility between the organic-phase bamboo scraps of the composite material and the inorganic-phase magnesium oxychloride. Scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and other techniques were used to characterize bamboo scraps before and after alkali treatment. The bamboo scraps treated with alkali exhibited improved bonding properties to cementitious materials. The mechanical properties and water resistance of the composite material were evaluated. The results indicated that the mechanical strength first increased and then decreased with an increase in alkali concentration. After treatment with 3wt% NaOH solution, the composite exhibited the highest compressive strength and bending strength. The softening coefficient also reached 0.57. Alkali treatment resulted in improved bonding of bamboo scraps with magnesium oxychloride cementitious material, as confirmed by mechanical property and water resistance tests, and SEM image analysis.

Impact behaviours of engineered geopolymer composite exposed to elevated temperatures

Engineered geopolymer composite (EGC) is a novel fiber reinforced geopolymeric material with ultra-high ductility, which is more eco-friendly than engineered cementitious composite (ECC) due to the substitution of cement. This paper was intended to investigate the impact behaviours of EGC exposed to elevated temperatures. The ambient cured EGC with local PVA fibers was first designed and tested under compressive and flexural loading conditions. The comparisons between ECC and EGC were made concerning the compressive and flexural behaviours. Then, the drooping hammer tests of EGC, ECC, cement and geopolymer matrixes were conducted under different environment temperatures, i.e., 50 °C, 100 °C and 150 °C. As the temperature increased from 50 °C to 150 °C, the impact resistance of cement decreased while the impact resistance of geopolymer increased gradually. It was also found that EGC has higher maximum impact load and impact duration than ECC as the environment temperature increased, indicating that EGC may be more suitable for the impact protection of structures under high temperatures. At the environment temperature of 50 °C, the energy dissipation capacity of EGC increased with the increase of alkali concentration, while the alkali concentration was recommended to be lower than 12 mol/L when the environment temperature is above 100 °C.

Stability Dynamic Characteristic of Oil-in-Water Emulsion from Alkali-Surfactant-Polymer Flooding.

The relationship model between the droplet lifetime and interface properties is established to characterize the stability of oil droplets, and then, the influence of the alkali–surfactant–polymer (ASP) concentration on the lifetime is analyzed by theoretical calculations. The stability dynamic characteristics of oil-in-water (O/W) emulsions from ASP flooding were evaluated using the emulsion stability model (Civan model) based on two-phase separation. The effect of ASP on dynamic characteristics of the emulsion was explored by analyzing film strength qualitatively and measuring interfacial tension and ζ potential. The results showed that the Civan model was suitable to evaluate the stability of the O/W emulsion and to obtain the corresponding dynamic characteristics. The O/W emulsions became more stable with the increasing alkali concentration first at a low alkali concentration (cNaOH < 200 mg/L) and then became less stable with the increasing alkali concentration at a high alkali concentration (cNaOH > 200 mg/L). The stabilities of O/W emulsions were improved with the increasing concentrations of the surfactant and polymer. The mechanism of stabilization of the O/W emulsion by ASP is as follows. The surface-active substances formed by the reaction of alkali and acidic substances in the oil phase, together with surfactants, adsorb at the oil–water interface, reducing the interfacial tension and increasing the strength of the oil–water interface film. The polymer only increases the strength of the interface film by increasing the viscoelasticity of the oil–water interface film.