Shrinkage Values Research Articles

Drying Time, Energy and Exergy Efficiency Prediction of Corn (Zea mays L.) at a Convective-Infrared-Rotary Dryer: Approach by an Artificial Neural Network

Energy consumption in the drying industry has made drying an energy-intensive operation. In this study, the drying time, quality properties (color, shrinkage, water activity and rehydration ratio), specific energy consumption (S.E.C), thermal, energy and exergy efficiency of corn drying using a hybrid dryer convective-infrared-rotary (CV-IR-D) were analyzed. In addition, the energy parameters and exergy efficiency of corn were predicted using the artificial neural network (ANN) technique. The experiments were conducted at three rotary rotation speeds of 4, 8 and 12 rpm, drying temperatures of 45, 55 and 65 °C, and infrared power of 0.25, 0.5 and 0.75 kW. By increasing drying temperature, infrared power and rotary rotation speed, the drying time, S.E.C and water activity decreased while the Deff, energy, thermal and exergy efficiency increased. In addition, the highest values of rehydration ratio and redness (a*) and the lowest values of shrinkage, brightness (L*), yellowness (b*) and color changes (ΔE) were obtained at an infrared power of 0.5 kW, air temperature of 55 °C and rotation speed of 8 rpm. The range of changes in S.E.C, energy, thermal and exergy efficiency during the corn drying process was 5.05–28.15 MJ/kg, 3.26–29.29%, 5.5–32.33% and 21.22–55.35%. The prediction results using ANNs showed that the R for the drying time, S.E.C, thermal, energy and exergy data were 0.9938, 0.9906, 0.9965, 0.9874 and 0.9893, respectively, indicating a successful prediction.

Durable Structural Recycled Concrete for Different Exposure Environments

In this work, the influence of limited percentages of coarse (CRCA) and fine (FRCA) recycled concrete aggregates (Type A recycled aggregates) on the durability properties of structural concrete was analyzed. Concretes were designed using 50% and 60% CRCA with simultaneous additions of 0%, 10%, and 20% FRCA and different types of cement (CEM II/AL 42.5 R, CEM II/AS 42.5 N/SRC, and CEM III/B 42.5 N-LH/SR). Recycled aggregate concrete (RAC) and natural aggregate concrete (NAC) mixtures were produced with similar compressive strength using effective water–cement ratios of 0.47 and 0.5. The drying shrinkage values and durability properties were determined, and they included the chloride permeability, chloride penetration depth, and accelerated and natural carbonation rates. The findings revealed that RAC produced using CEM III/B, which included the mixture produced with 60% coarse RCA and 20% fine RCA, achieved low chloride ion penetrability (up to 850 Coulombs) and exhibited the lowest chloride diffusion coefficient, approximately 7×10−13. Additionally, the RAC-C60-F20 concretes made with CEM II/AS proved suitable for the XC3 and XC4 exposure environments, guaranteeing a lifespan of 50 and 100 years based on the natural carbonation rate. In addition, the RAC-C60-F20 concrete made with CEM II/AL cement exhibited an adequate natural carbonation rate for XC4 environments, which was between 1.6 and 2.4 units higher than the accelerated carbonation rate. This work validates the use of RAC in XC environments (corrosion induced by carbonation) and XS1 environments (corrosion caused by chlorides from seawater).

Effect of Active MgO on Compensated Drying Shrinkage and Mechanical Properties of Alkali-Activated Fly Ash–Slag Materials

The influences of MgO activity and its content on the mechanical properties, drying shrinkage compensation, pore structure, and microstructure of alkali-activated fly ash–slag materials were investigated. Active MgO effectively compensated for the alkali-activated materials’ (AAMs’) drying shrinkage. The drying shrinkage increased rapidly with the increase in curing age and stabilized after 28 d. Within a certain range, the material’s drying shrinkage was inversely proportional to the content of active MgO. The higher the activity of MgO, the lower the drying shrinkage of the AAMs under the same MgO content. The drying shrinkage values of the test groups with 9% R-MgO, M-MgO, and S-MgO at 90 d were 2444 με, 2306 με, and 2156 με, respectively. In the early stage of hydration, the addition of S-MgO reduced the compressive strength. As the content of M-MgO increased, the compressive strength first increased and then decreased, reaching a maximum of 72.28 MPa at an M-MgO content of 9%. The experimental group with 9% M-MgO exhibited higher compressive and flexural strengths than those with 9% S-MgO and R-MgO, demonstrating better mechanical properties. The results of this study provide an important theoretical basis and data support for the optimal application of MgO in AAMs. MgO expansion agents have great application potential in low-carbon buildings and durable materials. Further research on their adaptability in complex environments will promote their development for engineering and provide innovative support for green buildings.

Analyzing the variations in the composition and properties in zirconia alumina composite ceramics

The effect of unstabilized zirconium dioxide on the processes of formation of composite ceramics from industrial corundum powders heat-treated at temperatures of 1430 and 1580?C, changes in its microstructure and physical and mechanical properties have been investigated. It was shown that due to the rigid corundum matrix, unstabilized ZrO2 is preserved mainly in the tetragonal phase. When ceramics are sintered during heat and self-diffusion, zirconium particles are located along the grain boundary of the corundum matrix and fill the pore space. The sintering effect of amorphous SiO2 also contributes to the increased density of ceramics. A two-stage sintering mode provides a finer-grained microstructure of ceramics. It was shown that due to the presence of a larger number of ZrO2 grains capable of t-m-transformation at the Al2O3 boundaries, the resistance of composite ceramics to mechanical and thermal loads increases. Ceramics obtained at 1580?C and containing 6.0 wt. % t-ZrO2 possesses the maximum hardness of 17 GPa. Dilatometric characteristics and the values of the relative shrinkage of composite samples are given.

Effect of Silica Fume on the Performances of Self-compacting Repair Mortar

Background Concrete is a widely utilized material in construction worldwide. However, concrete performance could be damaged under aggressive environments, therefore, many concrete structures may require repair and frequent maintenance. Objective The aim of this study is to develop reinforced Self-Consolidating Repair Mortars (SCRMs) incorporating silica fume and polypropylene fibers. Methods This research aimed to study the effect of silica fume as an alternative supplementary cementitious material (SCM) on the performance of fiber reinforced self-consolidating repair mortars (SCRMs). For this purpose, five SCRMs mixes incorporating 0%, 5%, 10%, 15%, and 20% of silica fume as partial cement replacement were prepared. Testing included slump flow, flow time, and unit weight, air-dry unit weight, compressive and flexural strengths, dynamic modulus of elasticity and water absorption. Results The results indicated that the substitution of cement by 15% of silica fume improves the flexural strength and slightly reduce the compressive strength of the fiber-reinforced repair mortar. The lowest values of total shrinkage, water capillary absorption, and sorptivity were observed for repair mortars containing 10% silica fume. In addition, bonding results between repair mortars containing silica fume and old concrete substrate investigated by the bond flexural strength test showed good interlocking, justifying the effectiveness of these produced mortars. Conclusion The results reveal that structural repair mortars containing 10 and 15% silica fume conform with the performance requirements of class R4 materials (European Standard EN 1504-3) and could be used in repair applications.

Calcium aluminate cement based high early strength engineered cementitious composites with recycled artificial flaws

Engineered Cementitious Composites (ECC) is an ideal repair material due to its high durability and ductility. However, providing ECC with high early strength is challenging since strength and ductility, which are key to crack-free repair, are also interdependent. Thus, it is necessary to use artificial flaws in order to keep the ductility at reasonable levels while increasing the strength. This study uses calcium aluminate cement, a non-portland cement, as the primary binder to attain the early strength in the production of high early strength ECC for the first time. Besides, expanded glass and crumb rubber, both made by recycling waste materials, were included as artificial flaws to enhance ductility. The performance of designed high early strength ECC was assessed through mechanical, abrasion, shrinkage and non-destructive tests and compared with high early strength portland cement based ECC. It is revealed that a minimum compressive strength of 28.9 MPa and flexural strength of 7.1 MPa could be attained even at the age of as early as 6 hours after casting. Nevertheless, deformation capacities were significantly improved after 24 hours following the casting by the use of both artificial flaws. In addition, acceptable drying shrinkage and abrasion resistance values were obtained.

Development and Evaluation of <i>Amaranthus spinous</i> Methanolic Extract Ointment for <i>In Vivo</i> Wound Healing Properties in Wistar Rats

Background: Traditional herbal medicines are minimally processed, plant-derived substances used in local treatments, such as tinctures, teas, poultices, and powders. The herb Amaranthus spinosus that is full of polyphenols, crude fiber, proteins, and saccharides is very effective for many diseases. Aim: Traditional medicinal herb of A. spinosus having wound healing potential with well-known medicinal value. The study involves the formulation of an ointment prepared with the methanolic extract of this plant and its phytochemical analysis for the identification of bioactive compounds. Methods: Its efficacy will be evaluated by the in vivo studies on controlled wounds in animal models and comparison of results with standard treatments. It will also assess the safety of the ointment for topical use and the general effectiveness of the ointment in wound healing. The rationale, therefore, remains that if it is able to establish a scientific validation for the traditional use of A. spinosus in the management or healing of wounds, then one more avenue of an effective treatment option will be opened. Result: By using ANOVA method wound shrinkage values for the control group ranged from 10.82±0.68 to 68.69±2.60 by the 16th day. In the case of Test-I, where the concentration used was 5%, the increase has been from an initial value of 11.24±1.23 to 76.12±1.93 on the 16th day. Test-II, where the concentration used was 10%, the increase has been from 14.14±0.98 initially to 93.99±0.68 on the 16th day. Treatment of the standard group with Soframycin was initiated at 15.26±1.25 and was completely closed with the values of 100±0.75 on day 16. Conclusion: In vivo model studies revealed that the methanolic extract of A. spinosus showed a very strong acceleration of wound healing without causing irritation or toxicity on the skin.

Application of Olivine Powder as a Filler for Silicone Pressure-Sensitive Adhesives

In this work, new self-adhesive materials were obtained based on cross-linked silicone self-adhesives obtained by modifying the composition with the addition of a silicon filler, olivine. Silicone pressure-sensitive resin DOWSIL 7358 was used as a basis and modified with various amounts of olivine. New materials (self-adhesive tape samples) were characterized in terms of peel adhesion, tack, cohesion at room and elevated temperatures, SAFT test (shear adhesion failure temperature), pot life (storage stability), and shrinkage (dimensional stability). During the tests, an increase in thermal resistance (>225 °C) and a drastic reduction in shrinkage values (below 0.5%) were noted for all modified samples tested. All tests were performed in compliance with international standards, e.g., FINAT FTM 1, FINAT FTM 8, FINAT FTM 9, FINAT FTM 14, and GTF 6001. This allows us to conclude that the new material has significant application potential due to the good performance results. The results of adhesion and tack were in ranges accepted in the PSA industry, cohesion was kept at an unchanged level (above 72 h), and a great increase in the thermal resistance was observed (from 147 °C for pure resin to high above 225 °C for even the smallest additions of the olivine powder. Moreover, the shrinkage of prepared adhesive films was reduced significantly. In the available literature, there are no references to the modification of adhesives using powdered silicon minerals of natural origin, which is a novelty due to their higher bulk density compared to commercial powdered silicon fillers.

Physicochemical characterisation and industrial application of new kaolin deposit in Sela Dingay Area, Central Ethiopia

Sela Dingay kaolin deposit is a primary deposit formed mainly through the weathering of rhyolitic ignimbrite. Integrated analyses of geological, mineralogical, geochemical and physical properties were conducted to characterise the industrial applications of Sela Dingay kaolin. X-ray diffraction (XRD) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) were used to characterise the raw kaolin samples. The results show that Sela Dingay kaolin is mainly composed of kaolinite (66–93%) and quartz (9–34%). The higher chemical index of alteration (CIA = 94.2%) and chemical index of weathering (CIW = 96.8%) values suggest that Sela Dingay kaolin was formed by intense chemical weathering under oxidising conditions. Sela Dingay kaolinite deposit consists of high percentage of clay/silt-sized particles, a low shrinkage value (1.1–3.4%), medium-high plastic limit (25–35%), with specific gravity and pH values ranging between 2.47 and 2.56 g/cm3 and 6.3 and 7.2, respectively. The overall results show that Sela Dingay kaolin is medium to high grade and it can be used for various industrial applications with appropriate beneficiation processes to remove higher amounts of Fe2O3 and quartz. Therefore, the newly discovered kaolin deposit (estimated at 5,136,166 tonnes) in the Sela Dingay area is a potential target for future kaolin exploitation.

Potential Utilisation of Solar-Assisted Kiln Dryer in Bamboo Drying

Bamboo is increasingly used as an alternative material for producing renewable and environmentally friendly products. Bamboo should be dried before use to increase its stability and improve its resistance against biodeterioration agents. The most common drying method for bamboo is through air-drying. Alternatively, artificial drying, such as solar drying, can produce optimum drying results regarding the drying rate and quality of bamboo throughput. This study investigated the potential utilisation of solar drying methods for processing local bamboo. The drying characteristics and physical and mechanical properties of solar-dried Gigantochloa levis bamboo culms’ bottom, middle, and top sections were determined. The drying time of G. levis culm has been reduced to about 40 days compared to the conventional air drying of 70 days using the solar-assisted kiln dryer. Solar-dried culms have a lower final moisture content of 20% than air-dried ones. The average circumference and diameter shrinkage values of solar-dried G. levis culms from green to approximately 12% moisture content were 3.22% and 4.29%, respectively, and the wall thickness shrinkage was 8.12%. The mean values of modulus of rupture and modulus of elasticity of solar-dried G. levis culm were 63.75 and 12567.99 N mm-2, respectively, while its mean values of compression and shear parallel to fibre were 45.87 and 10.01 N mm-2, respectively. The quality of solar-dried G. levis culms produced in this study showed the viability of using a solar-assisted kiln-dryer as a potential alternative processing method for drying local bamboo species in Malaysia.

Synthesis and Characterization of an Alkali-Activated Binder from Blast Furnace Slag and Marble Waste.

This study reports an alkali-activated binder including blast furnace slag (BFS) together with marble waste (MW). Cement is an industrial product that emits a significant amount of CO2 during its production and incurs high energy costs. MW is generated during the extraction, cutting, and processing of marble in production facilities, where dust mixes with water to form a settling sludge. This sludge is an environmentally harmful waste that must be disposed of in accordance with legal regulations. In this study, a substantial amount of MW, a by-product with considerable environmental and economic impacts worldwide, was utilized in the production of a binder through the alkaline activation of BFS. In doing this, different experimental parameters were tested to obtain the best binder samples according to workability and mechanical properties. Then, some experiments such as drying shrinkage determination, strength testing, and microstructure analyses were fulfilled through samples with the best values. The findings supported the improvement of the rapid-setting property of BFS by means of the addition of MW. MW reduced the time-dependent drying shrinkage values of BFS by 55%, especially in slag alkaline activation systems with a low or moderate alkali activator content. The substitution of MW (≤50%) in BFS increased flexural and compressive strengths (4.5 and 61.7 MPa), while a reference sample contained BFS only. Although the use of MW did not create a new phase, it contributed to a C-S-H bonding structure during the alkali activation of BFS in a microstructure analysis.

Optimizing Injection Molding for Propellers with Soft Computing, Fuzzy Evaluation, and Taguchi Method

This research explores multi-objective optimization in injection molding with a focus on identifying the optimal configuration for the moldability index in aviation propeller manufacturing. The study employs the Taguchi method and fuzzy analytic hierarchy process (FAHP) combined with the Technique for the Order Performance by Similarity to the Ideal Solution (TOPSIS) to systematically evaluate diverse objectives. The investigation specifically addresses two prevalent defects—shrinkage rate and sink mark—that impact the final quality of injection-molded components. Polypropylene is chosen as the injection material, and critical process parameters encompass melt temperature, mold temperature, filling time, cooling time, and pressure holding time. The Taguchi L25 orthogonal array is selected, considering the number of levels and parameters, and Finite Element Analysis (FEA) is applied to enhance precision in results. To validate both simulation outcomes and the proposed optimization methodology, Artificial Neural Network (ANN) analysis is conducted for the chosen component. The Fuzzy-TOPSIS method, in conjunction with ANN, is employed to ascertain the optimal levels of the selected parameters. The margin of error between the chosen optimization methods is found to be less than one percent, underscoring their suitability for injection molding optimization. The efficacy of the selected optimization method has been corroborated in prior research. Ultimately, employing the fuzzy-TOPSIS optimization method yields a minimum shrinkage value of 16.34% and a sink mark value of 0.0516 mm. Similarly, utilizing the ANN optimization method results in minimum values of 16.42% for shrinkage and 0.0519 mm for the sink mark. Doi: 10.28991/ESJ-2024-08-05-025 Full Text: PDF

Chemical shrinkage characteristics and prediction model of desulfurization electrolytic manganese residue-cement composite slurries

To reveal the chemical shrinkage (CS) characteristics of desulphurized electrolytic manganese residue (D-EMR) cement composite slurries, the CS was measured for slurries with different water-cement ratios (0.3 and 0.4) and varying D-EMR content (0 wt%, 5 wt%, 10 %, 15 wt%, 20 wt%, 25 wt%, and 30 wt%) using the expansion method. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and backscattered electron (BSE) image analysis were used to investigate the hydration products and pore porosity at different stages. In addition, the correlation between CS and hydration products was simulated using GEMS thermodynamics. The results indicate that as the water-cement ratio increases, the CS of D-EMR cement composite slurries increases significantly. At a water-cement ratio of 0.4, the CS decreases with increasing D-EMR replacement levels before 1829 h of hydration, but this trend reverses after 1829 h. At 8 days, the CS values for replacement levels of 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, and 30 wt% were 97.2 %, 94.9 %, 87.3 %, 84.4 %, 81.5 %, and 78.6 % of those of the pure cement pastes, respectively. The corresponding limiting chemical shrinkage values were 0.0712 mL/g, 0.0725 mL/g, 0.0742 mL/g, 0.0756 mL/g, 0.0769 mL/g, and 0.0780 mL/g. Finally, the prediction of long-term CS of D-EMR cement composite slurries is well described by both hyperbolic function prediction and thermodynamic simulations. These findings provide valuable theoretical support for the use of D-EMR as a supplementary cementitious material in construction.

Effect of PVA fibers grafted with MWCNTs on the shrinkage behaviors of engineered geopolymer composite (EGC)

Geopolymer have been considered as a promising alternative for the development of high-ductility and eco-friendly engineered materials. In this study, modified PVA fibers grafted with MWCNTs(PM) are used as additives to investigate their impact on the drying shrinkage, autogenous shrinkage and chemical shrinkage of Engineered Geopolymer Composites(EGC). Additionally, various micro-structure techniques, including X-ray Diffraction(XRD) and Scanning Electron Microscopy(SEM), are employed to examine the morphology and chemical composition of EGC. The experimental findings indicates that PVA fibers and MWCNTs both help to mitigate the drying shrinkage and autogenous shrinkage of the EGC. When the PVA fiber content is 2.0 % and the MWCNT content is 1.0 ‰, the 90-day drying shrinkage and autogenous shrinkage values of the EGC are minimized, reducing by 31.67 % and 34.16 %, respectively, in comparison to the control group. However, the incorporation of MWCNTs increases the chemical shrinkage of the geopolymer matrix, with the chemical shrinkage value reaching its maximum when the MWCNT content is 1.0 ‰. Micro-structural analysis reveals that the inclusion of PM leads to an improvement in the quantity of reaction products without affecting their type. Furthermore, the incorporation of PM refines the overall pore structure, restricts the crack development and enhances the interfacial bonding effect of EGC. Notably, a correction prediction model for drying shrinkage strain and autogenous shrinkage strain, incorporating the influence coefficients of PVA fibers and MWCNTs, is constructed under constant humidity and temperature conditions. This significantly improves the prediction accuracy of drying shrinkage and autogenous shrinkage of EGC.

Production and Characterization of Porous Anorthite Ceramics Using Sugar Process Solid Waste, Chamotte and Coal Powder Additives

Press filter cake is a solid waste produced during sugar production process and includes carbonates and organic components. In this study, coal powder in different percentages (from 10 wt.% to 50 wt.%) was mixed with 35 wt.% press filter cake and 65 wt.% chamotte composition to produce porous anorthite ceramic products with different apparent porosity percentages. The anorthite phase was observed as the dominant crystalline phase in all fired samples. The firing shrinkage values sharply increased after adding higher than 40 wt.% coal powder to composition. In addition, apparent porosity values were changed from 49% to 70%. Compressive strength values reduced from 18 MPa to 1.73 MPa while percentages of ground coal were increasing. Microstructural analysis also showed that the porosity values of the sintered samples showed important changes depending on the amount of coal additive. The thermal conductivity values showed a reduction from 0.113 W/mK to 0.064 W/mK while increasing the percentage of ground coal. Micro-computed tomography (Micro CT) analysis was performed for 40wt. % coal powder added composition and the total porosity value was found as 60.2%.

Research on humidity field and freezing resistance of green recycled ceramic internal cured concrete at early age

In cold and drought environment, concrete shrinkage cracking caused by water loss is serious, and thus the freezing resistance of concrete is deteriorated. The waste ceramic particles were used as internal curing materials to prepare concrete, based on this background. Then, the influence of internal curing with ceramic particles on humidity field and temperature of concrete is analyzed by using temperature and humidity sensor. Based on the change mechanism of the internal humidity of concrete, the relationship between the curvature radius of liquid surface and the relative humidity is revealed. Taking water loss and water loss rate as the index, the water transfer law of concrete surface under ceramic particle internal curing was defined. Through the drying shrinkage test, the mechanism of improving the drying shrinkage of concrete by internal curing in ceramic particles was mastered. Finally, the effects of ceramic internal curing on cement hydration, interfacial transition zone (ITZ) and freezing resistance of concrete were studied. The results show that the relative humidity, water loss and water loss rate of concrete increase with the increase of ceramic particle content, and the dry shrinkage value decreases with the increase of ceramic particle content. Compared with ordinary concrete, when the ceramic particle content is 10 %, 15 %, 20 %, 25 % and 30 %, and the test period is 10 days, the internal relative humidity of concrete increases by 0.52 %, 0.67 %, 1.55 %, 2.55 % and 3.05 %, respectively. The drying shrinkage values decreased by 3.42 %, 7.69 %, 10.26 %, 15.17 % and 30.13 %, respectively. When the test period was 1032 h, the water loss increased by 1.08 %, 5.15 %, 7.90 %, 12.69 % and 14.49 %, respectively. Furthermore, when the ceramic particle content is 20 %, the initial normalized heat flow of concrete increases by 2.74 mW/g, and the normalized heat flow minimum increases by 0.324 mW/g. The minimum ITZ microhardness increased by 2.64 MPa, the ITZ width decreased by 5 μm, and the maximum crack width at the contact between ITZ and aggregate decreased by 0.89 μm. At the same time, when the ceramic particle content is less than 20 %, the effect of internal curing on the freezing resistance of concrete increases with an increase in ceramic particle content.

Stretch and recovery properties of combined and combination twill based woven fabrics

Woven fabrics are being used in different forms, ranging from wearable clothing to household activities. Comfort and wearer ease are directly related to the stretch properties, and stretch will be beneficial with recovery performance at a given stress. This study is planned to work on the mechanical and stretch and recovery properties of combined and combination twill woven fabrics. The fabric samples were produced by using 59 tex (10/1 Ne) hemp yarn in both warp and weft directions, and thread density was kept constant in six woven fabric samples. Three different weaves, that is, combination twill weave (2/1 + 1/2 and 3/1 + 2/1), combined twill weave (2/1 + 1/2 and 3/1 + 2/1), and basic twill weaves (2/1 and 3/1) were selected for woven fabric preparation. Dimensional stability and shrinkage, tensile strength, puncture resistance, and stretch and recovery properties of developed woven samples were investigated. It was concluded that the stretch and recovery properties depend on the float and interlacement of yarns in the woven fabric. The combination twill weave structures have excellent stretch and recovery properties because they have the highest float in all samples. Combined twill weave structures have the highest tensile strength and puncture resistance properties. On the other hand, the highest shrinkage values are observed for basic twill weave structures.

Comparative study: High performance polymers of polyphenylene sulfide and polyethylenimine using Taguchi-Topsis optimization approaches

The role of high-performance thermoplastic products is increasing in the present days because of its excellent physical and mechanical properties and also capable of withstanding critical loads and temperatures. In this study, an attempt was made to improve the mechanical and physical properties of two polymers PPS (Polyphenylene Sulfide) and PEI (Polyethylenimine) by addition of glass fiber as a reinforcement fiber. The glass fiber (GF) content considered as 40 wt% for both the polymers. Injection molding method was used for fabrication of PPS and PEI samples. After fabrication, mechanical tests such as tensile, impact and dimensional shrinkage (%) of samples were calculated. Taguchi and Topsis analysis techniques were applied for evaluation of major influencing parameters and determining the best experiment to be performed on the machine. After conducting the test, PPS polymer exhibited better mechanical strength values and lower shrinkage (%) compared to PEI. The best input parameters kept on the machine were observed to be gate way type, temperature and pressure. The conditions of gate way type 2, temperature 320°C, and a pressure of 100 bar are obtained as the best input parameters to be fixed on the machine for achieving higher values of mechanical strength and lower dimensional shrinkage for both PPS and PEI polymers. Out of these two polymers, PPS exhibited better mechanical and physical properties combining with GF. This polymer can extend its usage as a high-performance polymer for various industrial applications.

Novel insights on the setting process, hardened properties, and durability of sustainable ultra-high-performance seawater sea sand concrete

Using seawater and sea sand to prepare concrete could effectively alleviate the shortage of freshwater and river sand resources and promote the sustainable development of concrete. However, the current research on the setting process, hardened properties, and sustainability of ultra-high-performance seawater sea sand concrete (UHPSSC) remain considerably limited. In this paper, the UHPSSC was designed to mitigate the autogenous shrinkage and enhance the sustainability, and the effect of seawater, untreated and desalinated sea sand on the setting process, mechanical properties, durability, and sustainability was explored by various tests. Results show that the abundant ions (e.g., Cl- and SO42-) in seawater and untreated sea sand promote the dissolution and nucleation of cement, accelerating the hydration process, and seawater provides a high pH hydration environment, which enhances the pozzolanic reaction activity of silica fume and fly ash. This leads to the enhanced flexural and compressive strengths at early age, reduced flowability, and increased autogenous shrinkage. Although the seawater and untreated sea sand considerably alleviate the natural raw materials consumption, the mechanical performance at 28 d and durability are reduced, thereby decreasing the sustainability index by 7.8 %. The desalination treatment of sea sand decelerates the hydration process of UHPSSC with untreated sea sand due to the lower ion content in desalinated sea sand. The application of desalinated sea sand mitigates the adverse impact of untreated sea sand on the workability, mechanical properties, and durability. However, this desalination process requires more energy and freshwater consumption, thereby decreasing sustainability index. The fly ash incorporation could improve the workability of UHPSSC, and decrease the autogenous shrinkage value by 17.9 %. Moreover, it mitigates the environmental effect without compromising the mechanical properties and durability, leading to an impressive 42.8 % improvement in sustainability. Durability assessment reveals that the prepared UHPSSC specimen maintains outstanding mechanical properties even after 360 d of exposure to severe marine environment, indicating its excellent durability. This paper provides novel insights for achieving a cleaner and more sustainable concrete production.

Shrinkage evolution and mechanism of self-curing concrete cooperatively cured with superabsorbent polymers and waterborne epoxy coatings

Shrinkage-induced cracking is a common phenomenon in concrete structures. To reduce concrete shrinkage, herein, a novel curing approach involving the concurrent application of internal superabsorbent polymers (SAPs) and external waterborne epoxy coatings (WECs) was adopted. Subsequently, the combined effects of the SAPs and WECs on the internal temperature, water retention behavior, relative humidity, and shrinkage performance of concrete were investigated. Furthermore, their underlying shrinkage-mitigation mechanisms were clarified and verified through mercury intrusion porosimetry tests. Results revealed that increasing the WEC application rates and number of spraying turns increased the relative humidities and reduced the shrinkage strains of the concrete specimens. The combined use of SAPs and WECs led to considerable reductions in the specimens’ humidity drop, water loss, and shrinkage values. The water losses of the concrete specimens exerted more considerable impacts on their relative humidity and shrinkage compared to their cumulative temperatures. Furthermore, the combination effects of the SAPs and WECs reduced the median pore diameters and increased the fractal dimensions of gel pores, thus triggered a reduce in capillary tension, and further mitigated the development of shrinkage strains. Overall, this study underscores the critical roles of evaporation, temperature, relative humidity, and pore-structure parameters on the shrinkage behavior of concrete. Additionally, it highlights the effectiveness of the combined application of SAP-based internal curing and WEC-based external curing, offering a feasible approach and technical support for reducing shrinkage in concrete structures.