Soaking Duration Research Articles

Водопоглощение термически модифицированного древесного заполнителя термодревесно-цементной композиции

In this article, the technological aspects of obtaining a new effective composite material based on thermally modified wood filler and cement binders – thermal wood concrete – are considered. The influence of water content in thermally modified wood filler on the qualitative characteristics of a wood-cement composition has been studied. To solve the theoretical problems and applied issues of forecasting the technological parameters for the production of thermal wood-cement composition, the mathematical models of the effect of soaking duration and water temperature on the relative change in the mass (dampening) of the filler have been developed. At the initial stage, experimental studies have been carried out to determine the effect of pre-soaking the filler on the curing of thermal wood concrete and the quality of the resulting material. The samples have been produced via vibrocompression of a semi-dry mixture using dry and pre-soaked filler made of thermally modified wood, as well as via vibratory casting. The regularities of moisture transfer between the filler and the cement-sand mortar have been determined, and it has also been established that pre-soaking the thermally modified filler has a positive effect on the strength and quality characteristics of thermal wood concrete. On the contrary, the use of the dry filler made of thermally modified wood in this molding method has a significant negative impact on the quality of the finished material. The process of moisture absorption by the thermally modified wood filler by soaking has been studied separately. The main regularities and features of water sorption by the filler have been established at the time intervals of 30, 60, 120, 180 and 300 minutes and at the water temperatures of 3–4, 16–18 and 75–85 ℃. It has also been determined that additional water heating significantly accelerates the intensity of water sorption and the degree of dampening of thermally modified wood fillers, and the size of their particles does not play a significant role in the process. In this case, the recommended duration of soaking the thermally modified wood filler before preparing the mixture and molding the products made of thermal wood concrete via semi-dry vibrocompression is 30 minutes.

Drought tolerance testing of paddy variety Inpari 4 with PEG-6000 in the germination phase

Paddy (Oryza sativa L.) factors in the importance of life for Indonesians. The challenge that will be faced in the future is global warming which can cause drought in the agricultural sector. Paddy is very susceptible to drought during germination and early growth stages. Such drought can cause crop production to decline. This research aims to provide earlier information on drought-tolerant paddy varieties. The research carried out in the Laboratory of Ecology and Plant Production Management, Sebelas Maret University. It was applied FCRD consisting of the first factor of PEG-6000 concentration (C) which is 0% (C0), 10% (C1), 15% (C2), 20% (C3) and 25% (C4), the second factor of soaking duration (S) is 12 hours (S1), 24 hours (S2) and 36 hours (S3). The data obtained were analyzed using ANOVA and further tested with DMRT 5%. The results of research on seed viability from the application PEG-6000 which can have a drought effect show that at a temperature of 26°C produces germination of 84,30%, C3S3 gave the highest value on germination (90,50%) and growing speed (47,58%/etmal), C0 gives the highest value at lead length (29,05 cm) and C4 gives the highest value at radicle length (35,64 cm).

Investigation on shear performance and prediction model of CFRP-ECC-concrete composite interface suffered from anodic polarization and environmental degradation

This study aims to investigate shear performance and prediction model of CFRP-ECC-concrete composite interface suffered from anodic polarization and environmental degradation. The effect of ECC mixtures, cathodic current densities, polarization period, and the duration of sulfate soaking and sulfate attacking by wet and dry cycles on the interface of the composite were studied. The results showed that three failure modes of CFRP-ECC-concrete composite interface were found. Shear load-slip curves showed double broken lines characteristics, while voltage-deterioration time curves showed an approximate linear increase relationship between voltage and polarization time. The five parameters all had significant effects shear strength deterioration on the CFRP-ECC-concrete composite interface. Moreover, this study proposed an innovative prediction model to the interfacial shear strength by the measured voltage, which can provide an important basic theory for ICCP-SS technology. This work makes a contribution to the ICCP-SS technology on the shear performance and prediction model of composite interface.

Effect of Priming on Seed Germination and Seedling Growth of Cardamom (<i>Elletaria cardamomum</i> L. Maton) at Teppi, Southwestern Ethiopia

An experiment was conducted to determine the effect of seed priming on the germination and seedling growth of cardamom. The experiment consisted of two factors, namely; five priming solutions (distilled water, KNO<sub>3</sub> (0.2%), GA<sub>3</sub> (200 ppm), cow urine (10%), and tap water), and two soaking durations (6 hrs. and 9 hrs.). The factorial combination of these factors was arranged in a randomized complete block design and replicated four times. Different parameters were measured, including seed germination percentage, germination index, shoot and root length, fresh and dry weight of shoots and roots, as well as root volume. Notably, the main effect of the priming solution had a significant (P<0.05) effect on the aforesaid germination and seedling growth attributes. However, the main effect of soaking duration and their interaction with priming solutions did not exhibit a significant effect (P>0.05). Among the priming solutions, the application of cow urine at a 10% concentration exhibited a significant effect on the seed germination and subsequent growth of the cardamom seedlings. Advantageous results of seedling vigor indexes I and II were observed from cardamom seeds primed with the same solution. Accordingly, the growers and seedling producers in the study area are advised to apply a 10% cow urine priming solution before sowing cardamom seeds for enhanced germination and seedling growth.

Microscopic insights into the long-term ageing mechanism of asphalt in the hygrothermal environments

The humid, thermal, and oxidative environments cause the synergistic degradation of asphalt materials. To reveal the long-term ageing mechanism of asphalt in the hygrothermal environments, base asphalt (BA) and styrene-butadiene-styrene (SBS) modified asphalt (SMA) were selected to prepare the short-term, long-term, and hygrothermal-aged samples. Then the changes in micromorphology, molecular weight distribution, chemical compositions, and microstructures of each aged asphalt sample were characterized. The results indicate that the soaking duration is determined as 32 h for preparing the hygrothermal-aged asphalt sample. The moisture diffusion causes physical damage to asphalt, forming circular micro holes on the asphalt surface, which is the main reason to accelerate asphalt ageing. The ambient water and air can easily permeate into asphalt, further accelerating asphalt ageing. Additionally, the small and medium molecular components in the hygrothermal-aged BA are decreased, while the large molecular components become more. Meanwhile, the molecular weight distribution of SMA is relatively concentrated after hygrothermal ageing, and the SBS modifier is degraded from supermolecules to macromolecules. Further, no new chemical compositions are produced after hydrothermal ageing of BA and SMA. The hygrothermal ageing accelerates the oxidation of thioethers and unsaturated carbon bonds to convert into sulfoxide and carbonyl groups. Finally, the hygrothermal ageing destroys asphalt components, and the number of Catana phases on the BA surface is lowered. The Catana phases on the SMA surface were seriously damaged and almost disappeared in asphalt components. The surface elevations of BA and SMA are increased after hygrothermal ageing, but the surface roughness is decreased. This study provides the microscopic insight into the long-term ageing mechanism of asphalt in the hygrothermal environments.

Microscale mechanism and key factors of waterborne epoxy resin emulsified asphalt enhancing interlayer bonding performance and shear resistance of bridge deck pavement

In this research, samples of emulsified asphalt with varying concentrations of waterborne epoxy resin were prepared to augment the adhesion performance of emulsified asphalt in bonding layers. The bonding efficacy of waterborne epoxy resin emulsified asphalt (WEREA) was evaluated across different temperatures, application rates, and soaking durations. This evaluation simulated interlayer stress conditions using Binder Bond Strength (BBS) tests, 45° oblique shearing tests, and pull-out tests. To analyze the compositional evolution, polymer distribution, and microstructure of WEREA, a series of tests including Fourier Transform Infrared Spectroscopy, fluorescence microscopy, and Scanning Electron Microscopy were conducted. Findings suggest that WEREA significantly improves both bonding strength and shear strength of the bonding layer, exhibiting the least temperature sensitivity compared to unmodified and Styrene-Butadiene Rubber (SBR) modified emulsified asphalts. The optimal concentration of waterborne epoxy resin is identified as 20%, with an application rate of 0.9 kg/m². Upon curing, WEREA forms a cross-linked 'honeycomb' structure within the emulsified asphalt, facilitating the adsorption and anchoring of asphalt and leading to a transition from an asphalt continuous phase to an epoxy-asphalt biphasic structure. This study provides insights into the microscale mechanisms and critical factors underlying the enhanced interlayer bonding performance in bridge deck pavements offered by modified emulsified asphalt.

Growth Response of Mucuna bracteata with the Application of Local Micro Organisms (LMO) of Banana Weevil

This research aims to determine the effect of concentration and duration immersion giving LOM banana weevil against the gowth of Mucuna bracteata. The research was conducted in the garden of Jalan Setia Bangun Pasar III, Sei Beras Sekata, Kecamatan sunggal, Kabupaten Deli Serdang, Sumatra utara and continued in the laboratory of the Indonesian Oil Palm Research Institute (IOPRI). This research was started in April-June 2020. This study used a randomized complete block design (RCBD) factorial. The first factor was the concentration of local microorganisms (LMO) of Banana Weevil consisting of 4 levels, namely: Without treatment, 15%, 30%, 45%. The second factor. The duration of immersion consists of 4 levels, namely: No immersion time, 15 minutes, 30 minutes, 45 minutes. Observation data were analyzed usingDuncan's Multiple Range Test with a significant 5%. The results showed that the LMO concentration of banana weevil was effective in increasing the gowth of the number of leaves 39.77, tendril length 83.14 cm, shoot fresh weight 28.54 g, and shoot dry weight 6.03 g. The duration of soaking had a significant effect on the highest number of leaves at week 3 (9.63 pieces). The interaction application of banana weevil concentration and soaking time affected the number of root nodules (40.50 gains) and root dry weight (0.73) g of theplant Mucuna bracteata.

EVALUATION OF DIFFERENT PASTEURIZATION AND STERILIZATION METHODS FOR OYSTER MUSHROOM SUBSTRATES

Oyster mushrooms can be cultivated with great spatial efficiency, on nutrient-poor plant materials, without light and under diverse climatic conditions. Their production therefore has a great potential for improving food security, especially in impoverished and overpopulated areas. However, the pasteurization or sterilization of mushroom substrates uses a lot of energy and water. This study investigates the impact of different pasteurization and sterilization techniques on the growth and yield of oyster mushrooms, and evaluates their water and energy usage. The efficacy of heat-based methods, including hot water, hot air, and pressurized steam, as well as a chemical method utilizing hydrated lime (Ca(OH)2) were assessed. The results show that sterilizing mushroom substrates through autoclaving can significantly increase the dry yields, up to 50% compared to pasteurization methods. However, pasteurization methods also achieved excellent results compared to untreated substrates, with good harvests and low pest occurrence. The mushroom water content was significantly higher in pasteurization methods where the substrate is submerged in water. In terms of fresh yield, hot water pasteurization was as good as autoclaving and significantly better than the other pasteurization methods. Hot air pasteurization has, on balance, a better water and energy efficiency than autoclave sterilization (about 75 % less energy) or hot water pasteurization (about 85 % less water). When performed at an air temperature of 75° C, which was found to be sufficient for successful mushroom cultivation, as little as 1068 kJ was needed to pasteurize one kg of dry substrate (e.g. maize straw). While hydrated lime pasteurization could use as little as 270 kJ per kg of dry substrate, it is very wasteful of water, as is hot water pasteurization and could lead to nutrient leaking. The success of mushroom cultivation, especially with hot air pasteurization, could also be influenced by the duration of substrate soaking before treatment. The study provides slight evidence, although inconclusive, for a positive effect of prolonged soaking periods on yield. Lastly, the study discusses the applicability of different disinfection techniques at varying production scales and for different mushroom species, focusing on African countries, where comparably small mushroom economies are growing rapidly, but often through the use of unsustainable pasteurization technology.

Effectiveness of Different Tyroxine Hormone Dosages on The Growth Performance And Violability of Depik Fish (Rasbora tawarensis)

Depik fish is a fish which is one of the endemic species in Lake Laut Tawar, Central Aceh Regency. Typical fish of the Gayo community which is currently being developed for domestication. However, from the results of several studies, the growth of depik fish is relatively slow, so it needs to be increased. One way to accelerate the growth of depik fish is by hormonal induction, through immersion in the hormone thyroxine with different doses. The aim of this research is to evaluate the growth performance and survival of depik fish soaked in thyroxine hormone with different doses of thyroxine hormone. This research was carried out at the Lukup Badak Fish Seed Center (BBI), Central Aceh using a completely randomized design (CRD) experimental method with four treatments and three repetitions. The treatments in this research were different durations of immersion in the thyroxine hormone, namely: no dose (P0), 0.05 mg/ liter (P1), 0.1 mg/ liter (P2), and 0.15 mg/ liter (P3). Meanwhile, the duration of the thyroxine hormone soaking used is 24 hours. Rearing of fish seeds is carried out using an Aquarium measuring 30 cm long, 20 cm wide and 25 cm high according to the treatment, for 28 days with a stocking density of 20 fish/container. This study concluded that different doses of the thyroxine hormone in Depik fish fry gave the highest growth in the treatment dose of 0.15 mg/liter, while the lowest growth was in the control treatment (no dose).

Exploring how YouTube videos demonstrating preparation of dried wood ear mushrooms could pose food safety risks: a case study

PurposeIn 2020, an outbreak of Salmonella Stanley linked to imported dried wood ear mushrooms affected 55 individuals in the United States of America. These mushrooms, commonly used in Asian cuisine, require processing, like rehydration and cutting, before serving. The US Centres for Disease Control and Prevention advise food preparers to use boiling water for rehydration to inactivate vegetative bacterial pathogens. Little is known about how food handlers prepare this ethnic ingredient and which handling procedures could enable Salmonella proliferation.Design/methodology/approachThis study used content analysis to investigate handling practices for dried wood ear mushrooms as demonstrated in YouTube recipe videos and to identify food safety implications during handling of the product. A total of 125 Chinese- and English-language YouTube videos were analysed.FindingsMajor steps in handling procedures were identified, including rehydration, cutting/tearing and blanching. Around 62% of the videos failed to specify the water temperature for rehydration. Only three videos specified a water temperature of 100 °C for rehydrating the mushrooms, and 36% of the videos did not specify the soaking duration. Only one video showed handwashing, cleaning and sanitising of surfaces when handling the dried wood ear mushrooms.Practical implicationsThis study found that most YouTube videos provided vague and inconsistent descriptions of the rehydration procedure, including water temperature and soaking duration. Food preparers were advised to use boiling water for rehydration to inactivate vegetative bacterial pathogens. However, boiling water alone is insufficient to inactivate all bacterial spores. Extended periods of soaking and storage could be of concern for spore germination and bacterial growth. More validation studies need to be conducted to provide guidance on how to safely handle the mushrooms.Originality/valueThis study will make a distinctive contribution to the field of food safety by being the first to investigate the handling procedure of a unique ethnic food ingredient, dried wood ear mushrooms, which has been linked to a previous outbreak and multiple recalls in the United States of America. The valuable data collected from this study can help target food handling education as well as influence future microbial validation study design and risk assessment.

Screening on halal gelatin extraction from spotted oceanic triggerfish (Chanthidermis maculata) skin using response surface methodology

Spotted oceanic triggerfish fish is one type of fish that has the potential to be a source of halal gelatin. Almost all parts of his body can become gelatin. In the process of processing the fish, many parts are wasted such as skin. Though this skin can be used for gelatin extract. From the results of the study, gelatin yield ranged from 2.7 – 9.3% with an average value of 5.50%. This gelatin has a viscosity value ranging from 6.21 – 7.57 cP which was analyzed using the Rapid Visco Analyzer (RVA) instrument and gel strength analysis using a Texture Analyzer and found results of 80.33 – 97.67 g / cm2. Based on the probability value < 0.05 yield, viscosity, and gel strength of gelatin, it is known that there are several independent variables that have a real effect on yield, namely variables B (concentration of H2SO4), D (soaking duration), F (ratio of water/extraction skin) and G (extraction temperature). In viscosity, the influential variables are C (citric acid concentration), D (soaking duration), E (soaking water/skin ratio) and G (extraction temperature). While on gel strength, the influential variables are A (NaOH concentration) and G (extraction temperature). The influence of factors on response can be sorted sequentially, namely the order in yield is G>F>B>D>A>H>C>E, in viscosity is C>E>D>G>H>A>B>F and in gel strength is G>A>E>H>B>F>C>D. This indicates that the G factor (extraction temperature) was selected as the most important factor, and the 2nd and 3rd most important factors can be selected from A (NaOH concentration), B (H 2SO4 concentration), D (extraction duration) and E (soaking water/skin ratio), and H (extraction duration).

The Effect of seaweed (Eucheuma cottonii) extract and duration of soaking on reduction of Copper (Cu) level in Freshwater Mussel (Pilsbryoconcha exilis)

Freshwater Mussels (Pilsbryoconcha exilis) are filter-feeder animals that have eating habits by filtering food in the water, making it possible that heavy metal copper (Cu) will accumulate in the body of the mussel. One type of seaweed that can absorb heavy metals is Eucheuma cottonii because it contains iota carrageenan (65%) which is a sulfated polysaccharide containing hydroxyl groups and carboxyl groups capable of retaining and accumulating heavy metals. In addition E. cottoni as a biosorbent in the aquatic environment. This research aims to determine the effect of extract concentration and the best soaking time in reducing copper (Cu) levels. This research was conducted from April to May 2023. In this study, the concentrations used were 6%, 10%, and 14% with a period of 45 minutes, 90 minutes, and 135 minutes. The results showed that the concentration of 14% extract with a soaking time of 135 minutes showed the highest decrease in copper (Cu) levels of 1.298 mg/kg or 87.10% and the lowest decrease in copper (Cu) metal levels at a concentration of 6% with a soaking time of 45 minutes of 0.442 mg/kg or 29.68%.

Evidence from interpretable machine learning to inform spatial management of Palau's tuna fisheries

AbstractStatic and dynamic area‐based management tools hold substantial potential to balance socioeconomic benefits derived from fisheries and costs from bycatch mortality of at‐risk species. Palau longline fisheries have high bycatch of at‐risk species including the olive ridley marine turtle and silky and blue sharks. This study analyzed a two decades‐long time series of observer and electronic monitoring datasets from the Palau distant‐water and locally‐based pelagic longline fisheries. An interpretable or explainable machine learning‐based modeling approach was used to derive spatially resolved species‐specific catch rate predictions. These models were conditioned on a suite of potentially informative environmental, bathymetric, ocean‐climate metric, vessel, monitoring system, and set‐specific operational predictors. Overall, there would be limited ecological tradeoffs from focusing fishing effort within primary catch rate hotspots for target bigeye and yellowfin tunas. Mean field prediction surfaces also defined catch rate hotspots for at‐risk species of silky and blue sharks, olive ridley turtle, and pelagic stingray, which did not overlap the hotspots for target species. The predicted target species hotspots, however, overlap olive ridley and pelagic stingray warmspots. Results also identify opportunities for temporally dynamic spatial management to control catch rates of target and bycatch species. Management of fishery operational predictors of fishing depth and soak duration present additional opportunities to balance catch rates of at‐risk bycatch and target species. A transition to employing fleetwide or vessel‐based output controls that effectively constrain the fishery would alter the spatial management strategy to focus on zones with the lowest ratio of at‐risk bycatch to commercial catch. Our findings support evidence‐informed evaluation of spatial management strategies and complementary measures to meet objectives for balancing socioeconomic benefits derived from target species catch with costs to threatened species.

Peningkatan Kualitas Emping Melinjo melalui Proses Pengepresan dan Penurunan Kadar Purin di UKM Emping Jago

&lt;em&gt;&lt;em&gt;&lt;strong&gt;Quality Improvement of Emping Melinjo through Pressing Process and Reduction of Purin Level at SME Emping Jago.&lt;/strong&gt; &lt;/em&gt;Emping melinjo is one of the popular foods among Indonesians. Kartasura is one of the districts in Sukoharjo that has potential in the production of emping melinjo. This study aimed to improve the quality of emping melinjo by using a mechanical pressing machine and reducing the purin level. The method used was a literature review based on scientific journals, books, and others. The results were to substitute the pressing process using mechanical machinery and by soaking treatment to reduce the purin levels. The improvement on pressing process were performed as an innovation so the process will not depend on human workers. Then, the soaking in a 4% acetic acid solution (vinegar) varied for 0; 10; 20; and 40 minutes.The hypoxanthine and adenine levels (in micrograms per gram), according to the soaking duration, showed 46,43; 41,50; 41,05; 36,71; and 124,74; 110,90; 109,83; 108,82 respectively. &lt;em&gt;The 40 minutes soaking process could decrease the purin level by 20%.&lt;/em&gt;&lt;/em&gt;

Capacity of Mangrove Fruit Macerate (Sonneratia alba) as a Preservative Fresh Vannamei Shrimp (Litopenaeus vannamei) Meat

Mangrove fruit (Sonneratia alba) is known to contain tannins. This flavonoid has antibacterial properties. It makes this fruit macerate has potential as a preservative for shrimp meat. This study aimed for determining the ability of S. alba fruit macerate to maintain the quality of vannamei shrimp meat. The study was conducted in a laboratory by exposing fresh vannamei shrimp meat to S. alba fruit macerate. Exposure was carried out by soaking shrimp meat. The concentrations of macerate used were 25, 50, 75, and 100%. The duration of soaking was 60 and 120 minutes. Bacterial population (total plate count), presence of hydrogen sulfide gas (H2S), acidity value (pH), and score of organoleptic were used as indicators of Shrimp meat quality. The tests were conducted after 24 hours of incubating shrimp meat at room temperature. The results showed the concentration of macerate and the time of soaking affected the quality of the shrimp meat. These effects were in the form of inhibition of bacterial populations, production of H2S and maintaining organoleptic properties, while the pH values ​​of all treatments were the same. Finally, the best concentration of macerate to maintain the quality of fresh vannamei shrimp meat is 100% with 60 minutes of soaking time.

Pengaruh Lama Perendaman dengan Sari Labu Siam (Sechium edule) Terhadap Penurunan Kafein Biji Kopi Arabika (Coffea arabica) Kintamani

&#x0D; &#x0D; &#x0D; The process of decaffeination involves reducing the caffeine content in coffee and other substances containing caffeine using various methods, such as immersing them in siamese pumpkin extract. Siamese pumpkin extract contains protease enzymes that aid in the decaffeination process. This research aims to investigate the impact of soaking time with siamese pumpkin extract on decreasing the caffeine content of Kintamani arabica coffee beans and to determine the appropriate soaking duration for reducing the caffeine content of Kintamani arabica coffee. In this study, a Completely Randomized Design was employed with five levels of soaking time treatments, namely 0 hours, 12 hours, 24 hours, 36 hours, and 48 hours, which were repeated three times, resulting in 15 experimental units. The parameters observed included water content, protein content, caffeine content, and sensory evaluation, including aroma, taste, and overall acceptance. The data were analyzed using analysis of variance (ANOVA), and if there was a significant effect of the treatment, Duncan's multiple range test was applied. The duration of soaking Arabica Kintamani coffee beans with siamese pumpkin extract had a significant influence on the water content, protein content, caffeine content, and sensory attributes of the coffee. The optimal soaking time for producing decaffeinated coffee was found to be 24 hours, resulting in a caffeine content of 0.3% and a water content of 2.72%, with a protein content of 22.14%. The sensory evaluation revealed that the coffee had a light coffee aroma and a light bitter taste, which was preferred overall.&#x0D; &#x0D; &#x0D;

Efficient and long-lasting corrosion inhibition mechanism of an anionic surfactant on AZ91D Mg alloy in oxalic acid solution

The efficient and long-lasting corrosion inhibition mechanism of bis(2-ethylhexyl) sulfosuccinate sodium (AOT) on AZ91D Mg alloy in oxalic acid solution were studied by electrochemical methods, surface techniques, theoretical calculations and simulations. The findings demonstrated that AOT was an effective and long-lasting corrosion inhibitor, the corrosion inhibition rate of 6.75 mM AOT was 89.84 % and raised in corrosion inhibition effectiveness with increasing soaking duration. The adsorption of AOT followed Langmuir adsorption isotherm and belonged to physical and chemical mixed adsorption. The polar sulfonyl group of AOT gradually almost vertically adsorbed on its surface to produce a uniform, dense, and thick protective layer to inhibit its corrosion, and the hydrophobicity of the alkyl chain of AOT repelled corrosive medium.

Response Surface Methodology Approaches in Producing Amorphous Silica from Rice Straw Ash

A large amount of rice straw is produced as crop residue from rice production as an underutilization waste material. The open burning of rice straw can lead to environmental pollution by forming an abundant amount of rice straw ash (RSA) and exposing harmful gases to the atmosphere. Thus, RSA can be used as a cement replacement material due to its high amount of silica. Silica is a helpful additive to cement mix by accelerating the hydration process of cement because of its high reactivity and improving mortar performance. This study focuses amount of high silica of RSA in modified concrete through thermochemical pretreatment via response surface methodology (RSM). The factors involved in the pretreatment of RSA are 0.01M – 0.1M HCl hydrochloric acid, 1 – 3 hours soaking duration, and 60 - 80℃ soaking temperature, and a response is the percentage of reactive compound content (SiO2, Al2O3, and Fe2O3). Therefore, central composite design (CCD) in the RSM and the analysis of variance (ANOVA) have been used to evaluate the interaction between the factors and response, then simulated and further assess the accuracy of the model to achieve the accurate prediction. As a result, RSM observed that the optimum silica amount in the treated RSA (98.34%) was produced using parameters of 0.06 M HCl, 2 hours of soaking duration, and 70℃ soaking temperature in the pretreatment process. After that, it is followed by a burning process at a controlled temperature and a grinding process to produce treated RSA. The prediction given by the RSM was not the sole result but was proved through X-Ray Fluorescence (XRF) analysis. The result of XRF analysis obtained for each model with the same value of each factor (HCl concentration = 0.06 M, soaking duration = 2 hours, and soaking temperature = 70℃) is more than 97.00% and falls between the prediction index range. Thus, the model is validated since the actual experimental result is within the expected range for any involved factor. Hence, the treated RSA was considered a high-quality pozzolanic material incorporated in the mortar production.

Effect of the strength grade of parent concrete on the performance of recycled aggregate treated by cement-fly ash slurry under prolonged soaking duration

The detrimental effects of quarrying natural resources have contributed to large-scale environmental pollution. Utilizing recycled concrete aggregate (RCA) obtained from construction and demolition waste as a replacement for natural aggregates has become an effective solution for environmental sustainability. However, the inevitably diminished characteristics of the adhered mortar and the existence of an additional interfacial transition zone (ITZ) have negatively suppressed the widespread use of these materials in production lines. The present study aims to comprehensively investigate the effects of a cement-fly ash slurry with a mass ratio of 50% of the total weight of RCA on the microstructure and engineering properties of RCA derived from three different parent concretes with strength grades of 20, 30, and 60 MPa. The RCAs were soaked for 24 h, 48 h, and 72 h to evaluate the long-term effects of the pozzolanic slurry. A sequence of laboratory tests was conducted, including mercury intrusion porosimetry (MIP) test, thermal gravimetric–differential thermal analysis (TG-DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, and measurements of water absorption and crushing value. The MIP results demonstrated a significant increase in medium capillary and gel pores, and a reduction in large capillary pores in the RCA with an increase in soaking time. TG-DTA results indicated an increase in Ca(OH)2 content during the first 24 h and 48 h of treatment. However, after 72 h of treatment, the Ca(OH)2 content of the treated RCA decreased in all cases. XRD analysis revealed the appearance of a few additional ettringite peaks among the treated RCAs in all cases. SEM images demonstrated the presence of additional hydration products after treatment, which filled the pores and improved the surface texture. Furthermore, after treatment, the crushing value of all treated RCA decreased by 6.0–27.1%, whereas the water absorption decreased by 12.0–30.9% compared to the untreated RCA. Based on several experimental results, the formation of hydration products and the improvement mechanism of RCA from three different parent concretes by slurry treatment with different soaking durations were discussed. In conclusion, a prolonged impregnation time of 72 h yielded a dominant performance, effectively intensifying their inferior properties, regardless of the initial strength grade of parent concrete.

Machining of EN19 steel using cryogenically cooled electrode material in electric discharge machining

The machining of high-strength alloys like EN19 steel poses significant challenges due to their inherent hardness and susceptibility to surface defects during conventional machining processes. In this study, we explore a pragmatic approach to address these challenges by investigating the implementation of cryogenically cooled electrode materials in electric discharge machining (EDM) for EN19 steel. Specifically, cryogenic treatment is applied to copper electrodes with varying soaking durations of 12 and 24 h. The research considers input process parameters, including peak current ( IP), pulse on time ( Ton), flushing pressure, and soaking duration. Material removal rates (MRR), electrode wear rate (EWR), and surface roughness (SR) are considered as the response parameters. To optimize these input parameters, the study employs the VIKOR technique. Improving the in-depth analysis, our investigation incorporates using COMSOL Multiphysics simulation to intricately model the mechanical aspects of single-spark EDM, mainly focusing on the thermal and structural characteristics of both electrodes and the workpiece. The simulation lends strong support to the experimental findings in relation to MRR and EWR. The experimental data demonstrates notable enhancements after a 24 h cryogenic soaking period for copper electrodes. Specifically, we observed a remarkable 77.36% increase in electrical conductivity, a substantial 20% augmentation in MRR, a significant 39% reduction in EWR, and a noteworthy 9.8% decrease in SR. The meticulous synergy of experimental exploration, optimization, and simulation offers a transformative outlook toward augmenting machining efficacy and prolonging electrode longevity, particularly in the context of EDM.