Volume Swelling Research Articles

Isothermal reduction kinetics and microstructure evolution of various vanadium titanomagnetite pellets in direct reduction

Vanadium titanomagnetite (VTM) pellets is an important charge for utilizing VTM through the rotary kiln-electric furnace process, and its reduction characteristic is essential to industrial production. This paper investigated the reduction behaviors and mechanism of three types of fired VTM pellets, i.e. PA, PB and PC with 13.02%, 11.70% and 5.25% TiO2, respectively. Under the optimal conditions, which were reduced at 1423 K for 150, 120 and 100 min, respectively, they obtained more than 90% reduction degree. During reduction, PA exhibited excellent resistance to volume swelling and great morphology, while PB and PC displayed abnormal swelling and structural damage. Kinetic and microstructure studies indicated that the reduction of PA, which consisted of titanohematite and pseudobrookite, was controlled by the random nucleation and subsequent growth of metallic iron, whereas that of PB and PC, which mainly contained titanohematite, was controlled by intrinsic chemical reactions. Iron- and titanium-bearing oxides were reduced to metallic iron via two routes: titanohematite → titanomagnetite → wustite → metallic iron and pseudobrookite → metallic iron. These various compositions and grain sizes of iron- and titanium-bearing oxides led to different generation rates and morphologies of metallic iron, directly affecting the reduction characteristics and macroscopic performance of VTM pellets.

Fabrication of novel biocomposite made of chemically treated sludge fibers and various molecular weight polypropylene

The effect of the chemical treatment of paper mill sludge fibers and polypropylene molecular weight were studied relative to the physical, mechanical, and morphological properties of a novel cellulosic biocomposite. Paper mill sludge fibers were treated with acetic anhydride, and succinic anhydride was mixed with maleic anhydride polypropylene (MAPP) and coupling agent (0 and 3%). The ratio of fibers and polymer materials was considered 30 to 70, which was manufactured by the hot-pressing method at 180 °C. Water absorption, volume swelling, and contact angle were examined on each specimen according to ASTM standards, while Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) explored the efficiency of chemical modification of fibers and the morphology of biocomposites, respectively. The results showed that chemical treatment of fibers reduced the water absorption and volumetric swelling. Both tensile and flexural strength were increased with chemical treatment using the coupling agent. Comparison of fibers treated with succinic acid and acetic acid showed that the succinic acid enhanced the mechanical properties better than the acetic acid treatment. Finally, FTIR analysis showed that the hydroxyl groups decreased, and SEM images indicated the interface between fibers and polypropylene improved via chemical treatment of sludge fibers.

Critical stress evaluation of rigid pavement due to the presence of water in expansive soil subgrade

The use of various types of rigid pavement is widespread because of its superiority in resisting heavy load vehicles. However, traffic loading complexity and subgrade response cause uncertainty during the design process. The presence of water in expansive soil issue swelling affected the flexural behavior of a rigid pavement slab. Rigid pavement relies heavily on the support and stability of the subgrade. Plain concrete is very weak in resisting tensile stresses so that the failure of rigid pavement slab structures often occurs in the expansive subgrade zone. Therefore, this study aims to numerically analyze the relationship between variations in the thickness of rigid pavement slabs on the flexural behavior parameters, such as critical and tensile stresses that affected water in expansive soil. The concrete’s performance limit was determined, using its material’s constitutive equation curve, and the data were analyzed using the finite element method. The results showed that the presence of water in expansive soil caused a change in soil volume (swelling), a reduction in soil bearing capacity (shrinking), and consequently, a rigid pavement cracked due to water variations in the subgrade. Generally, increasing the thickness of rigid pavement is a common method for mitigating the detrimental effects of expansive soil swelling. It is possible to provide reinforcement in other forms, which provide an opportunity to improve the performance of the concrete slab as a rigid pavement. For example, stabilization of expansive soil with materials capable of reducing its expansive power can be done but it requires large resources to realize it. Another method is to provide reinforcement to the rigid pavement slab structure, so that the rigid pavement slab is able to withstand traffic loads and also the expansion and shrinkage behavior of the expansive soil

Monitoring of alpha-decay radiation damage in a 241Am-doped glass-ceramic material

The evolution under alpha-decay radiation of a 241Am doped aluminoborosilicate glass-ceramic was investigated in hot cells DHA-ATALANTE facility in CEA. The cumulative La2O3 - Am2O3 solubility limit was voluntarily exceeded, leading to the formation of apatite-like silicate crystals. The crystals, with a hexagonal-shaped morphology, that is characteristic of apatite crystals, have a composition and a cell parameter close to those expected for an apatite phase of stoichiometric composition Ca2(La,Am)8(SiO4)6O2. Structural and microstructural evolutions under alpha self-irradiation were followed for 8 years by regularly analyzing the crystals and the residual glassy matrix. The evolution of the X-Ray Diffraction (XRD) patterns is the result of a progressive radiation-induced amorphization in apatite crystals. The fully amorphous state is reached at an alpha-decay dose of around 3 × 1018 α/g. Raman analyses suggest a modification of the connectivity of the SiO4 tetrahedra of apatite crystals, with a transition from isolated SiO4 units in the crystalline state to connected SiO4 units in the metamict state. The crystalline-to-amorphous transformation is accompanied by an increase in macroscopic volume (swelling), highlighted by RAMAN imaging. This macroscopic dimensional change is also associated to a decohesion of the crystals from the glassy matrix, observed by Scanning Electron Microscopy (SEM). However, optical and SEM images of the glass-ceramic surface do not reveal any significant cracks in the residual glass under alpha self-irradiation, thus showing a quite good stability of this glass-ceramic material.

Effects of neutron irradiation on densities and elastic properties of aggregate-forming minerals in concrete

The aggregate-forming minerals in concrete undergo volume swelling and microstructure change under neutron irradiation, leading to degradation of physical and mechanical properties of the aggregates and concrete. A comprehensive investigation of volume change and elastic property variation of major aggregate-forming minerals is still lacking, so molecular dynamics simulations have been employed in this paper to improve the understanding of the degradation mechanisms. The results demonstrated that the densities of the selected aggregate-forming minerals of similar atomic structure and chemical composition vary in a similar trend with deposited energy due to the similar amorphization mechanism. The elastic tensors of all silicate minerals are almost isotropic after saturated irradiation, while those of irradiated carbonate minerals remain anisotropic. Moreover, the elastic modulus ratio versus density ratio of irradiated minerals is roughly following the density–modulus scaling relationship. These findings could further provide basis for predicting the volume and elastic properties of irradiated concrete aggregates in nuclear facilities.

Synergistic effect of tung oil and heat treatment on surface characteristics and dimensional stability of wood

Wood is a sustainable biomass material with undesirable intrinsic properties of hygroscopicity and dimensional instability, which restrict its broader application. Tung oil, as a natural plant oil, has shown some promise for improving wood properties. Here, a synergistic method combined with tung oil impregnation and heat treatment was used to modify wood. The results showed that both heat treatment and tung oil impregnation were helpful in decreasing the moisture absorption, water uptake, and volume swelling coefficient of wood. Moreover, the impregnated tung oil occupied the water passages and significantly reduced the porosity and permeability of wood, providing a better hydrophobic surface and thus preventing water absorption and further improving dimensional stability. Therefore, joint modification of wood by tung oil and heat treatment provides an effective and eco-friendly method that has great prospects for the future.

A comparative study of irradiation response in amorphous TaTiWVCr refractory high entropy alloy with the counterpart of tungsten films

In this work, tungsten-containing TaTiWVCr refractory high entropy alloy (RHEA) and tungsten (W) films with amorphous structures were irradiated by a 60 keV helium (He) ion beam platform, the fluences were ranging from 1 × 1016 cm−2 to 2 × 1017 cm−2. Results showed that the crystallization phenomenon in RHEA initially happened at fluence of 5 × 1016 cm−2. Meanwhile, the obvious crystallization in W films was induced at the highest fluence of 2 × 1017 cm−2. This indicated that the crystallization and the grain growth in TaTiWVCr RHEA amorphous films were more easily occurred than that of W films when exposed to the same He + environment. The prominent electronic stopping power and He + energy deposition induced electron excitation played vital role in producing inelastic thermal-spikes via electron-phonon coupling, which was contributed to the crystallization kinetic energy and the overall grain growth in irradiated regions. The phase structure of RHEA film kept stable up to the highest fluence of 2 × 1017 cm−2, even though the alloy elements demonstrated local short-range segregation due to the diffusion-driven crystallization and the formation of highly-pressurized bubbles in the irradiated RHEA. In contrast to the W, smaller-sized bubbles and less dislocations were mainly distributed in the irradiated region of RHEA due to its naturally special high entropy effect and high lattice distortion. Besides, the results of irradiation-induced superficial morphology and volume swelling revealed that the RHEA exhibited more excellent swelling resistance than that of W. This study will potentially provided a useful indicator of RHEA with self-healing stability to resist irradiation and promote the development of state-of-the-art plasma-facing materials for the future nuclear fusion.

Numerical analysis of matrix swelling and its effect on microstructure of digital coal and its associated permeability during CO2-ECBM process based on X-ray CT data

Matrix swelling effect will cause the change of microstructure of coal reservoir and its permeability, which is the key factor affecting the engineering effect of CO2-ECBM technology. The Sihe and Yuwu collieries are taken as research objects. Firstly, visualization reconstruction of coal reservoir is realized. Secondly, the evolution of the pore/fracture structures under different swelling contents is discussed. Then, the influence of matrix phase with different swelling contents on permeability is discussed. Finally, the mechanism of swelling effect during the CO2-ECBM process is further discussed. The results show that the intra-matrix pores and matrix-edge fractures are the focus of this study, and the contacting area between matrix and pore/fracture is the core area of matrix swelling. The number of matrix particles decreases with the increase of size, and the distribution of which is isolated with small size and interconnected with large size. The swelling effect of matrix particles with larger size has a great influence on the pore/fracture structures. The number of connected pores/fractures is limited and only interconnected in a certain direction. With the increase of matrix swelling content, the number, porosity, width, fractal dimension, surface area and volume of pores/fractures decrease, and their negative contribution to absolute permeability increases from 0.368% to 0.633% and 0.868%–1.404%, respectively. With the increase of swelling content, the number of intra-matrix pores gradually decreases and the pore radius becomes shorter during the CO2-ECBM process. The matrix continuously expands to the connected fractures, and the width of connected fractures gradually shorten. Under the influence of matrix swelling, the bending degree of fluid flow increases gradually, so the resistance of fluid migration increases and the permeability gradually decreases. This study shows that the matrix swelling effect is the key factor affecting CBM recovery, and the application of this effect in CO2-ECBM process can be discussed.

External bioelectric control of tissue hydrostatic pressure and ion pumping.

Direct-Current (DC) currents exist throughout the body and regulate cellular responses spanning directed cell migration (electrotaxis) to transcriptional regulation. New approaches using electrical cues to control biological systems are, therefore, quite exciting, and we have previously demonstrated electrically programmable collective migration in epithelia. Here, we demonstrate those same cues reprogramming 3D growth in lumenized tissues such as hollow kidney spheroids and intestinal organoids. We found that electrical stimulation induces a rapid, powerful, and reversible swelling in these tissues, and we discuss how external electrical stimulation can control the inflation of lumenized structures and cellular mechanisms mediating the response. We first studied hollow kidney spheroids within a hydrogel integrated into our SCHEEPDOG electrobioreactor. This allowed 3D, timelapse imaging during electrical stimulation. Hollow spheroids inflated nearly 3X by volume relative to control spheroids within 4 hrs of stimulation. The rate and magnitude of inflation increased with increasing electric field strength, and overly strong field gradients induced ‘popping’. We hypothesized that the dense actomyosin network at the apical surface of the structures provided a physical limit to the inflation response, and showed that inhibiting actomyosin contractility prevented popping and increased the maximum swelling volume. We used ion channel inhibitors to determine that the majority of the response can be attributed to the CFTR ion channel (apical chloride channel) and NKCC (basal sodium/potassium channel). Our computational model relating direct-current fields, electrochemistry, and hydrostatic pressure capture many of these effects, as well as predicting asymmetric ion distributions around spheroids. Interestingly, 3D cross-sections of inflated tissues reveal asymmetric cell shapes on the anode/cathode cysts of the spheroids. We have recently confirmed that mouse intestinal organoids also inflate upon field stimulation in a CFTR-mediated fashion, and are exploring other lumenized tissues to assess the generality of this phenomenon.

Oriented tuning yolk-shell structure for well-confinement and constructing durability of silicon/carbon composite

Silicon-based materials have been recognized as one of the most promising anode materials for next-generation lithium-ion batteries (LIBs) due to its high theoretical specific capacity (4200 mA h g−1), appropriate lithiation potential and abundance in earth. However, the fulsome volume swell and intrinsically low conductivity result in the sluggish kinetics and the limited cycle life, which severely hinders its commercial application. Herein, a composite of Si@hollow nitrogen-doped carbon (Si@HNC) with typical yolk-shell structure is designed and fabricated via a facile strategy coupled super-molecular self-assembly with carbonization. Benefiting from the buffering effect of yolk-shell nanostructure on the volumetric variation, and the excellent conductivity of the porous nitrogen-doped carbon shell, Si@HNC anode material exhibits high structural stability, fast charge and ion transfer. As a result, the Si@HNC sample with the Si content of 54.4 wt% delivers a reversible capacity of 865 mA h g−1 with the retention of ∼98 % at 1.0 A g−1 after 300 cycles. More surprisingly, a stable capacity of 1013 mA h g−1/3.24 mAh cm−2 is also retained at 0.5 A g−1 after 400 cycles even under the high areal loading of 3.2 mg cm−2.

The vibrational properties of native and thermally modified wood in dependence on its moisture content

The vibrational properties of spruce (Picea abies Karst.) and European beech (Fagus sylvatica L.) were investigated in this study in dependence on the relative humidity (RH). The RH was measured at 20 °C ranging from oven-dried to 85%. For the evaluation of the vibrational properties the dynamic modulus of elasticity E’ and the damping coefficient tan δ were measured at 7 climate steps. The same samples used for the vibrational tests were afterwards mildly thermally modified at 180 °C and measured at the same climate steps. Both wood species were compared and evaluated considering the property changes (E’, tan δ, sorption isotherms and volume swelling) due to the thermal modification. The chosen modification resulted in a marginal change in the vibrational properties of spruce, whereas the properties of beech were clearly changed. The vibrational properties of beech could be improved in the usual RH range (35–85%) due to this thermal modification. For spruce, it was concluded that a mild modification, conducted in this study, is not suitable for improving the vibrational properties. Further conclusions concerning the underlying causes as well as the use in musical instruments were drawn.

Evaluation of immiscible CO2 injection in high water production reservoir in the Pannonian basin

Carbon dioxide (CO2) flooding is one of the most important and most used enhanced oil recovery (EOR) method because it does not only increase oil recovery efficiency but also is used as an underground CO2 storage. It is considered a very complex method as it involves knowing the fluid phase behavior with different CO2 concentrations. It should be noted that oil swelling (volume increase) with the dissolution of carbon dioxide has a significant effect on increase of oil recovery. When this occurs, a significant decrease in the viscosity of the oil is observed. In this study, a reservoir 3D simulation modeling approach was applied to evaluate immiscible and miscible CO2 flooding in a high WC reservoir. To reduce simulation time, the PVT composition was grouped into 5 fluid components. The 3-parameter, Peng-Robinson Equation of State (EOS) was used to match PVT experimental data by using the Schlumberger's ECLIPSE PVTi software. One-dimensional slim-tube model was defined using ECLIPSE 300 software to determine the minimum miscibility pressure (MMP) for injection of CO2. Beside this approach, an analytical MMP estimation was carried out using several correlations. Schlumberger Petrel software was used to set up a 3D simulation model of a static and dynamic model. Various scenarios of immiscible and CO2 injection have been simulated using ECLIPSE 300 software and these results have been compared.

Physicochemical Characteristics of Instant Boiled Rice: Study of Sodium Citrate Concentration and Soaking Time

Cooked rice (nasi liwet) is a typical rice dish of Java Island which is cooked using spices so that it has a unique taste and aroma. Making nasi liwet takes a long time, so this dish is only served at certain times. Therefore, a fast rice processing technique is needed but still has a distinctive taste and aroma. The purpose of this study is to analyze the physicochemical analysis of instant liwet rice based on the concentration and soaking time of sodium citrate. The physicochemical analysis tested were rehydration time, volume expansion, bulk density, texture, yield, ash content, and water content. The study was conducted by soaking sodium citrate (0, 2, 5, and 8% w/v) and soaking time (2, 4, and 6 hours) on rice. The results showed that the fastest rehydration time for instant nasi liwet was 4.55 minutes. The range of observation parameters such as expansion volume is 66.26-91.24%; bulk density is 0.413-0.581 g/ml; the texture is 431-1496 g/mm; yield is 89.64-92.26%; ash content is 4.11-4.45% and water content is 5.83-7.03%wb. Variations in sodium citrate concentration and immersion time increased the swelling volume and ash content, while water content, bulk density, texture, and yield tended to decrease. The best treatment based on the multiple attribute Zeleny method was immersion of 5% sodium citrate for 4 hours of immersion. Keywords: Immersion Time, Instant Rice, Nasi Liwet, Physicochemical, Sodium Citrate

Molecular Structure and Dynamics in Wet Gecko β-Keratin.

Molecular dynamics simulations are performed to investigate the molecular picture of water sorption in gecko keratin and the influence of relative humidity (RH) on the local structure and dynamics in water-swollen keratin. At low RHs, water sorption occurs through hydrogen bonding of water with the hydrophilic groups of keratin. At high RHs (>80%), additional water molecules connect to the first "layer" of amide-connected water molecules (multimolecular sorption) through hydrogen bonds, giving rise to a sigmoidal shape of the sorption isotherm. This causes the formation of large chain-like clusters surrounding the hydrophilic groups of keratin, which upon a further increase of the RH form a percolating water network. An examination of the dynamics of water molecules sorbed in keratin demonstrates that there are two states, bound and free, for water. The dynamics of water in these states depends on the RH. At low RHs, large-scale translational motions of tightly bound water molecules to keratin are needed to remake the entire hydration shell of the keratin. At high RHs (>80%), the water molecules more quickly exchange between the two states. The center-of-mass mean-square displacement of water molecules indicates a hopping motion of water molecules in the keratin solvation shell. The hopping mechanism is more pronounced at RHs < 80%. At higher RHs, water translation through water clusters (water network) dominates. We have observed two regimes for the dependence of dynamical properties on the RH: a regime of gradual increase of the dynamics over 10% < RH < 80% and a regime of drastic dynamic acceleration at RH > 80%. The latter regime begins exactly where the water uptake and the volume swelling also increase much more and where a drastic change in the elastic properties of gecko keratin has been observed. A nearly linear relation between the relaxation times for all dynamical processes and the water content of gecko keratin is observed.

The Effect of Adding Bambara Groundnut (Vigna subterranea) on the Physical Quality, Nutritional Composition and Consumer Acceptability of a Provitamin A-Biofortified Maize Complementary Instant Porridge

Undernutrition is prevalent in developing regions, particularly sub-Saharan Africa (SSA), especially among children under five. Biofortification of staple crops and using indigenous and traditional crops could be an affordable and sustainable strategy together with other existing strategies to reduce undernutrition. This study aimed to determine the effect of adding bambara groundnut (BGN) on the physical quality, nutritional composition and consumer acceptability of a provitamin A-biofortified maize (PVABM) complementary instant porridge. The PVABM flour was substituted with flour of either red or brown BGN variety at 0, 10, 20 and 30% (w/w) levels. The composite flours were used to make an instantized complementary porridge. The physical quality (texture, color, water absorption capacity (WAC), solubility index (SI) and swelling volume (SV)) of the grains and the composite complementary instant porridges were assessed. Nutritional analysis was conducted using standard AOAC methods. A 55-member consumer panel evaluated the acceptability of the porridge samples using a nine-point hedonic scale. The firmness, WAC, SI and SV decreased with increasing concentration of flour of either of the BGN varieties. The decrease in SV would positively affect the porridge quality as nutrient density and viscosity decreased. The protein, fat, fiber and total mineral (ash) content of the porridges increased with an increase in either BGN variety. There was no significant difference (p &gt; 0.05) in the overall acceptability of the BGN–PVABM composite porridge samples and the porridge without BGN (control). The improved nutritional composition and positive consumer acceptability of BGN–PVABM are encouraging as consumption could contribute to the alleviation of nutrient deficiencies, including protein-energy malnutrition and mineral deficiencies, especially in SSA.

Fabrication of a Cation Exchange Membrane with Largely Reduced Anion Permeability for Advanced Aqueous K-ion Battery in an Alkaline-Neutral Electrolyte Decoupling System.

Herein, an efficient method to prepare sulfonated polyether ether ketone (SPEEK) based cation exchange membranes (CEMs) is developed, where polyethersulfone (PES) is used as an additive. The optimized membrane of 30wt.%PES/SPEEK-M exhibits a rather low anion permeability and a high ionic conductivity of 9.52mScm-1 together with low volume swelling in water. Meanwhile, tensile strength of the membrane is as high as 31.4MPa with a tensile strain of 162%. As separators for aqueous K-ion batteries (AKIBs) with decoupled gel electrolytes (Zn anode in alkaline and Prussian blue (FeHCF) cathode in neutral). Discharge voltage of the AKIB can reach 2.3V. Meanwhile, Zn dendrites can be effectively suppressed in the gel anolyte. Specific capacities of the FeHCF cathode are 116.7mAhg-1 at 0.3Ag-1 (close to its theoretical value), and 95.0mAhg-1 at 1.0Ag-1 , indicating good rate performance. Capacity retention of the cathode is as high as 91.2% after 1000 cycles' cycling owing to the well remained neutral environment of the catholyte. There is almost no pH change for the catholyte after cycling, indicating good anion-blocking or cation-selecting ability of the 30wt.%PES/SPEEK-M, much better than other membranes.

Do patients treated with Invisalign have less swelling after orthognathic surgery than those with fixed orthodontic appliances?

Patients treated with perioperative Invisalign for orthognathic surgery may experience less postoperative swelling than those with fixed appliances because of a lack of mucosal irritation from bonded brackets and wires. The aims of this study were to (1) compare facial swelling after orthognathic surgery in subjects with Invisalign to those with fixed appliances using 3-dimensional (3D) subtraction imaging and (2) determine if the type of operation influences differences in swelling. This is a retrospective case-control study. To be included in the case group (Invisalign), patients had to have had: (1) LeFort I and/or bilateral sagittal split osteotomies, with or without genioplasty, (2) perioperative orthodontic treatment using Invisalign, and (3) 3D photographs at postoperative timepoints 1 week (T1), 3-4 weeks (T2), and 5-7 weeks. A sex and operation-matched control group with fixed appliances (standard) was also included. The primary outcome variable was the volume of facial swelling, measured by subtraction imposition of the T1 and T2 3D images using reference images (5-7 weeks). Twenty-two subjects (36% female; mean age 20.7 ± 3.15 years) were included: Invisalign (n= 11) and standard (n= 11). For each group, 7 subjects had 1 operation (LeFort I or bilateral sagittal split osteotomies), and 4 had bimaxillary surgery ± genioplasty. At T1, the Invisalign group had significantly less swelling than the standard group (17.52 ± 10.79 cm3 vs 37.53 ± 14.62 cm3; P<0.001). By T2, the differences were no longer significant (6.62 ± 5.19 cm3 for Invisalign; 5.85 ± 4.39 cm3 for standard, P= 0.728). Subjects with Invisalign had significantly less facial swelling in the first postoperative week than those with fixed appliances.

Study of Changes in Crystallinity and Functional Properties of Modified Sago Starch (Metroxylon sp.) Using Physical and Chemical Treatment.

Sago starch has weaknesses such as low thermal stability and high syneresis. Modifications were made to improve the characteristics of native sago starch. In this study, sago starch was modified by autoclave-heating treatment (AHT), osmotic-pressure treatment (OPT), octenyl-succinic anhydride modification (OSA), and citric acid cross-linking (CA). This study aimed to examine the changes in chemical composition, crystallinity, and functional properties of the native sago starch after physical and chemical modifications. The results show that physical modification caused greater granule damage than chemical modification. All modification treatments did not alter the type of crystallinity but decreased the relative crystallinity of native starch. New functional groups were formed in chemically modified starches at a wavelength of 1700-1725 cm-1. The degree of order (DO) and degree of double helix (DD) of the modified starches were also not significantly different from the native sample, except for AHT and OPT, respectively. Physical modification decreased the swelling volume, while chemical modification increased its value and is inversely proportional to solubility. AHT and OPT starches have the best freeze-thaw stability among others, indicating that both starches have the potential to be applied in frozen food.

Predicting compressive strength of cement-based materials containing water-absorbent polymers considering the internal-curing region

The water-absorbent polymer will bring large holes and the internal-curing region for cement-based materials. These two effects will bring negative and positive effects on the compressive strength of the cement-based material, respectively. In this paper, a calculation model of the compressive strength of cement-based materials with water-absorbent polymers was proposed considering the influence of the large holes and internal-curing on the compressive strength. A method for determining the internal-curing width of water-absorbent polymers based on backscattering image analysis was established. Based on the internal-curing width, the compressive strength was predicted and compared with the results of experiments. In addition, the influences of the internal-curing width, size, dosage, mass swelling rate, and volume swelling rate of water-absorbent polymers on the compressive strength were analyzed. The results show that the internal-curing width of the water-absorbent polymers with a mass swelling ratio of 4.22 g/g is about 13 µm. Based on the internal-curing width obtained by characterization, the compressive strength obtained by model is 7 % greater than that obtained by experiments. Besides, the influence range of the internal-curing width, size, and mass swelling ratio of the water-absorbent polymers on the compressive strength is between 80 Mpa and 90 Mpa. The influence range of the dosage and the volume swelling rate of the water-absorbent polymers on the compressive strength is between 20 Mpa and 90 Mpa. The compressive strength is mainly related to the dosage and the volume swelling rate of water-absorbent polymers. The larger the dosage and volume swelling rate are, the smaller the compressive strength is.

Study on volume swell and mechanical properties of fuel system elastomers with Fischer–Tropsch fuel for diesel engines

The compatibility of elastomers used in engine fuel system with Fischer–Tropsch (FT) fuel is essential, but there is very limited research available on it. In this work, the compatibility between four types of commonly used elastomers in fuel system and FT fuel was experimentally investigated. The assessed elastomers including nitrile butadiene rubber (NBR), ethylene propylene diene-monomer rubber (EPDM), fluoroelastomer (FKM), and chlorinated polyethylene (CPE) were exposed to FT fuel which derived from natural gas for 21 days. The properties of the elastomers such as mass, volume, hardness, tensile strength, elongation at break, and tear strength were measured before and after immersion, at the same time the change rates of these properties were calculated. The results demonstrated that all properties of EPDM deteriorated significantly after soak, and its compatibility with FT fuel was the worst, making it unsuitable for FT engines. NBR, FKM, and CPE all showed low rates of property change, with FKM exhibiting the greatest compatibility performance with FT fuel. Additionally, the O-rings made of FKM were submerged in FT fuel and diesel for 7 days, 14 days, and 21 days, respectively. It was found that the mass and volume variations of FKM O-rings in FT fuel were negligible and comparable with those of diesel fuel.