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Senthilan, Pingkalai R., and Charlotte Helfrich-Förster. "Rhodopsin 7–The unusual Rhodopsin inDrosophila." PeerJ 4 (September 6, 2016): e2427. http://dx.doi.org/10.7717/peerj.2427.
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Rhodopsins are the major photopigments in the fruit flyDrosophila melanogaster. Drosophilaexpress six well-characterized Rhodopsins (Rh1–Rh6) with distinct absorption maxima and expression pattern. In 2000, when theDrosophilagenome was published, a novelRhodopsingene was discovered:Rhodopsin 7(Rh7).Rh7is highly conserved among theDrosophilagenus and is also found in other arthropods. Phylogenetic trees based on protein sequences suggest that the sevenDrosophilaRhodopsins cluster in three different groups. While Rh1, Rh2 and Rh6 form a “vertebrate-melanopsin-type”–cluster, and Rh3, Rh4 and Rh5 form an “insect-type”-Rhodopsin cluster, Rh7 seem to form its own cluster. Although Rh7 has nearly all important features of a functional Rhodopsin, it differs from other Rhodopsins in its genomic and structural properties, suggesting it might have an overall different role than other known Rhodopsins.
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Nguyen, Duong. "EFFECT OF DIFFERENT TYPES OF RICE HUSK ASH ON SOME GEOTECHNICAL PROPERTIES OF CEMENT-ADMIXED SOIL." Iraqi Geological Journal 53, no. 2C (September 30, 2020): 1–12. http://dx.doi.org/10.46717/igj.53.2c.1rs-2020-09-01.
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Rice husk ash (RHA) is an agricultural residue and has shown great potential for soil stabilization. However, the research on the utilization of RHA for soft soil improvement using cement deep mixing method is still limited and the efficiency of using different RHA types for soil improvement needs to be clarified. In this study, the effect of different RHA types on Atterberg limits, unconfined compressive strength (UCS), and elastic modulus (E50) of soil-cement mixtures will be investigated. Two types of RHA which obtained from open fire burning (RHA1) and burning in a furnace under controlled conditions of temperature and duration of burning (RHA2), were used for this study. The RHA contents from 0 to 15% and 10% cement of the dry weight of the soil were used to treat the soft soil. The research results show that the types of RHA insignificantly affect the change in Atterberg limits of cement-admixed soil. Regarding the soil strength, the RHA2 shows a higher efficiency in the enhancement of treated soil strength at 28 days of curing than the RHA1. The addition of 12% RHA2 to the cement-admixed soil can increase the UCS and E50 values of treated soil by more than 50%.
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CECCONELLO, V., B. R. C.SARTORI, M. P. .KULAKOWSKI, C. S. KAZMIERCZAK, and M. MANCIO. "Shrinkage and porosity in concretes produced with recycled concrete aggregate and rice husk ash." Revista IBRACON de Estruturas e Materiais 12, no. 3 (June 2019): 694–704. http://dx.doi.org/10.1590/s1983-41952019000300013.
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Abstract The admixture of recycled concrete aggregates (RCA) in new concretes is an interesting alternative in the efforts to mitigate environmental impacts. RCA may increase porosity and change properties of concretes. Rice husk ash (RHA) is employed as supplementary cementitious material may improve concrete properties. The present study investigated the shrinkage of concrete prepared with RCA and RHA, proposing a mathematical model to explain the phenomenon. Concretes were produced with 25% and 50% of coarse recycled aggregate as replacement of natural aggregate, 0%, 10%, and 20% of RHA as replacement of cement, and a water-to-binder ratio of 0.64. Water absorption and capillary and total porosities were analyzed on day 28. Shrinkage tests were conducted on days 1, 4, 7, 14, 28, 63, 91, and 112. The results point to a significant interaction between RHA and RCA.
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Chakraborty, Satarupa, and Nirbhay Thakur. "Strength assessment of concrete using rice husk ash, recycled concrete aggregate and polyvinyl alcohol fiber." IOP Conference Series: Earth and Environmental Science 889, no. 1 (November 1, 2021): 012020. http://dx.doi.org/10.1088/1755-1315/889/1/012020.
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Abstract : This research work present the finest proper mix by adding and replacing with some other admixture materials having same properties as standard concrete materials. The substances that are used in this Rice husk ash (RHA) Recycled concrete aggregates (RCA) and polyvinyl alcohol fiber (PVA). Coarse aggregates was replaced with RCA at 50% and 0-20% RHA in scheming concrete mixes. For this, 5 to 20% (such as 5%, 10%, 15% and 20%) of RHA has been used as a fractional replacement of cement. PVA fiber has been added to this mix at fixed percentage of 0.50% by weight of concrete. 6 mm geometric length of PVA fiber which were aspect with ratio of 428 were used in this research work. In the present research work I did non-destructive and destructive tests after 7 days and 28 days. The values of tests were 10% for RHA and 50% of RCA with fiber fulfills which was PVA which were designed as for the requirement of construction industry. The results show that by adding more amount of RHA and RCA the concrete strength starts decreasing. Tests performed over concrete: Rebound Hammer Test, Flexural Strength Test, Water Absorption Test, Compressive Strength Test, Split Tensile Strength Test, and Ultrasonic Pulse Velocity Test.
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Christova, Nelly, Boryana Tuleva, Rashel Cohen, Galya Ivanova, Georgy Stoev, Margarita Stoilova-Disheva, and Ivanka Stoineva. "Chemical Characterization and Physical and Biological Activities of Rhamnolipids Produced by Pseudomonas aeruginosa BN10." Zeitschrift für Naturforschung C 66, no. 7-8 (August 1, 2011): 394–402. http://dx.doi.org/10.1515/znc-2011-7-811.
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Pseudomonas aeruginosa BN10 isolated from hydrocarbon-polluted soil was found to produce rhamnolipids when cultivated on 2% glycerol, glucose, n-hexadecane, and n-alkanes. The rhamnolipids were partially purified on silica gel columns and their chemical structures elucidated by combination of one- and two-dimensional 1H and 13C NMR techniques and ESI-MS analysis. Eight structural rhamnolipid homologues were identified: Rha-C10- C8, Rha-C10-C10, Rha-C10-C12:1, Rha-C10-C12, Rha2-C10-C8, Rha2-C10-C10, Rha2-C10-C12:1, and Rha2-C10-C12. The chemical composition of the rhamnolipid mixtures produced on different carbon sources did not vary with the type of carbon source used. The rhamnolipid mixture produced by Pseudomonas aeruginosa BN10 on glycerol reduced the surface tension of pure water from 72 to 29 mN m-1 at a critical micellar concentration of 40 mg l-1, and the interfacial tension was 0.9 mN m-1. The new surfactant product formed stable emulsions with hydrocarbons and showed high antimicrobial activity against Gram-positive bacteria. The present study shows that the new strain Pseudomonas aeruginosa BN10 demonstrates enhanced production of the di-rhamnolipid Rha2-C10-C10 on all carbon sources used. Due to its excellent surface and good antimicrobial activities the rhamnolipid homologue mixture from Pseudomonas aeruginosa BN10 can be exploited for use in bioremediation, petroleum and pharmaceutical industries.
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Sambo, Paolo, Franco Sannazzaro, and Michael R. Evans. "Physical Properties of Ground Fresh Rice Hulls and Sphagnum Peat Used for Greenhouse Root Substrates." HortTechnology 18, no. 3 (January 2008): 384–88. http://dx.doi.org/10.21273/horttech.18.3.384.
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Ground fresh rice (Oryza sativa) hull materials were produced by grinding whole fresh rice hulls and passing the resulting product through a 1-, 2-, 4- or 6-mm-diameter screen to produce a total of four ground rice products (RH1, RH2, RH4, and RH6, respectively). The physical properties and water release characteristics of sphagnum peatmoss (peat) and the four ground rice hull products were evaluated. All of the ground rice hull products had a higher bulk density (Bd) than peat, and as the grind size of the rice hull particle decreased, Bd increased. Peat had a higher total pore space (TPS) than all of the ground rice hull products except for RH6. As grind size decreased, the TPS decreased. Peat had a lower air-filled pore space (AFP) than all of the ground rice hull products and as the grind size of the rice hull products decreased, AFP decreased. Peat had a higher water holding capacity (WHC) than all of the ground rice hull products. Grind sizes RH4 and RH6 had similar WHC, whereas RH1 and RH2 had a higher WHC than RH4 and RH6. Peat, RH4, and RH6 had similar available water content (AVW), whereas RH2 had higher AVW than these materials and RH1 had the highest AVW. However, peat had the lowest AVW and easily available water (EAW) as a percentage of the WHC. The ground rice hull products RH1 and RH2 had the highest AVW and EAW of the components tested. Peat had the highest water content at container capacity. As pressure was increased from 1 to 5 kPa, peat released water more slowly than any of the ground rice hull products. The RH1 and RH2 ground hull products released water at a significantly higher rate than peat, but RH4 and RH6 released the most water over these pressures. For all rice hull products, most water was released between 1 and 2 kPa pressure. The rice hull products RH1 and RH2 had physical properties that were within recommended ranges and were most similar to those of peat.
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Hulke, Brent S., and Thomas J. Gulya. "Registration of the Oilseed Restorer Sunflower Germplasms RHA 472, RHA 473, RHA 474, and RHA 475, Possessing Resistance to Sclerotinia Head Rot." Journal of Plant Registrations 9, no. 2 (April 10, 2015): 232–38. http://dx.doi.org/10.3198/jpr2014.12.0084crg.
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Dewi, Sri Jayanti, Putra Jaya Ramadhansyah, Abdul Hassan Norhidayah, A. Aziz Md. Maniruzzaman, Mohd Rosli Hainin, and Mohd Haziman Wan Ibrahim. "Effect of Rice Husk Ash Fineness on the Properties of Concrete." Applied Mechanics and Materials 554 (June 2014): 203–7. http://dx.doi.org/10.4028/www.scientific.net/amm.554.203.
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In the present research, the effect of rice husk ash fineness on the properties of concrete was studied. Eight different fineness grades of rice husk ash were examined. A rice husk ash dosage of 15% by weight of binder was used throughout the experiments. The water-to-binder ratio was 0.49 to produce concrete having target strength of 40MPa at 28 d. Workability, compressive strength and gas permeability tests were carried out to identify the properties of concrete. The results revealed that increasing the fineness of RHA by mechanical grinding was found to improve the workability of RHA blended cement concrete. In addition, the use of RHA3 with mean particle size of 9.52μm produces the concrete with good strength. Finally, significant improvement was observed in mixtures incorporating RHA in terms of permeability coefficient.
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Thumrongvut, Jaksada, Sittichai Seangatith, Chayakrit Phetchuay, and Cherdsak Suksiripattanapong. "Comparative Experimental Study of Sustainable Reinforced Portland Cement Concrete and Geopolymer Concrete Beams Using Rice Husk Ash." Sustainability 14, no. 16 (August 10, 2022): 9856. http://dx.doi.org/10.3390/su14169856.
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The ordinary Portland cement (PC) manufacturing process emits toxic carbon dioxide into the environment. Minimizing cement consumption in the construction industry is a major scholarly priority. This paper studies the comparison of reinforced Portland cement concrete and geopolymer concrete beams, in which rice husk ash (RHA) is used as a partial replacement for cement. The study aims to determine the optimum mix proportion of Portland cement concrete with RHA (PC-RHA) and geopolymer concrete with RHA (GC-RHA) for compressive strength that meets the requirements for normal strength concrete of 18, 25, and 32 MPa and compares to ones of the control PC without RHA. Then, the load behaviors and the failure modes of the reinforced PCC beam and reinforced GC beam using RHA as partially PC (PC-RHA beam and GC-RHA beam) were investigated. The obtained experimental load capabilities were also compared to ones predicted by the equation for designing reinforced concrete beams developed by ACI Committee 318. According to the test results, the compressive strength of the PC-RHA and GC-RHA decreased when there was a higher proportion of RHA replacement in the concrete. In terms of the structural behavior, all the PCC, PC-RHA, and GC-RHA beam curves are bilinear up to the first crack load and before the yield load, then become nonlinear after the yield load of the beam specimens. The maximum crack width of the GC-RHA beam was less than that of the PC-RHA beam. Furthermore, the GC-RHA beam was more ductile than the PC-RHA beam. Finally, the ACI equation provides reliable predictions with a margin of error of 4 to 7%. This concludes that the experimental load capabilities of the PC-RHA beam and GC-RHA beam were consistent with the ACI design equation.
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Hartigan, Elaine, Peter FitzGerald, and Mary Kelly. "RHA Banquet Exhibition, RHA Gallagher Gallery, Dublin, October - November 1997." Circa, no. 82 (1997): 61. http://dx.doi.org/10.2307/25563225.
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Zahemen, Tuleun Lawrence, Jimoh Alao, and Wasiu John. "Performance of Rice Husk Ash - Calcium Carbide Waste in Concrete." Advanced Materials Research 1155 (August 2019): 41–53. http://dx.doi.org/10.4028/www.scientific.net/amr.1155.41.
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This paper examines and present the findings of the physical and mechanical properties of concrete containing rice husk ash (RHA), and the blend of rice husk ash with calcium carbide waste (RHA-CCW). Concrete cubes, cylindrical and beam specimens containing different percentages of RHA and RHA-CCW by weight of cement (5, 10, 15 and 20 %) were cast. Compressive strength test was carried out after the specimens were cured in water for 7, 14, 28 and 56 days. Test for tensile and flexural strength was carried out after 28 days curing. Initial and final setting time test was carried out on mortar specimens with the same percentage of RHA and RHA-CCW. Bogues model was used to determine the elemental and compound composition of cement when blended with the RHA and RHA-CCW. From the results obtained, the compressive strength of RHA-CCW concrete increases as cement is partially replaced with RHA-CCW content, with the maximum strength attained at 5 % replacement. RHA concrete attains it maximum strength at 10 % replacement. The maximum compressive strength results obtained for both RHA and RHA-CCW concrete were higher than the strength of plain concrete (0 % replacement) by 1.1 % and 14.7 % respectively. Interestingly, results obtained for the tensile strength also shows a similar pattern of strength development with that of compressive strength. The flexural strength properties of concrete was improved upon when RHA-CCW was used in concrete compared to RHA. The results of setting time test for RHA mortar showed a decrease in setting time, while the reverse was the case for RHA-CCW mortar. In conclusion, provided adequate curing is maintained, the used of RHA-CCW gives a better performance in concrete than RHA. However, they both perform better in concrete than the plain, and can be used as additives in concrete production.
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Zeng, Zong Qiang, Hong Chao Liu, He Ping Yu, and Zheng Peng. "Structure and Thermal Properties of RHA/NR Composite." Advanced Materials Research 482-484 (February 2012): 1275–80. http://dx.doi.org/10.4028/www.scientific.net/amr.482-484.1275.
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The rice husk ash/natural rubber (RHA/NR) composites were prepared by latex blending process using the RHA modified with silane coupling agent. The structure and morphology of modified RHA were studied. The dispersing performance of modified RHA in the composites was evaluated from the structure and thermal properties. The results indicate that silane coupling agent KH-570 can react with the carboxyl of the RHA surface, leading to a significant decrease in carboxyl absorption intensity and the obvious improvement in the dispersion of RHA particles in rubber matrix. As the modified RHA having grafted onto NR molecular chains can increase the interface force between RHA and rubber matrix, the thermal stability of RHA/NR composites thus can be improved. The RHA/NR composite of highest thermal stability can be prepared with RHA load of 5% shows the best.
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Godwin Adie Akeke. "Effects of source location on the pozolannic properties of Rice Husk Ash (Rha) and strength properties of concrete." GSC Advanced Engineering and Technology 2, no. 1 (December 30, 2021): 011–20. http://dx.doi.org/10.30574/gscaet.2021.2.1.0042.
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This paper presents the effects of variability in the chemical and elemental composition of Rice Husk Ash (RHA) sourced from four (4) different locations on Tensile Properties of Concrete. RHA is an agricultural waste gotten from rice mills after removal of rice paddy for food and burnt in open air or under controlled processes. RHA is found to be pozzolanic and can be used to partially replace cement to enhance the strength and quality of concrete. The different sources where RHA was gotten are; Ogoja, Abakaliki, Adani and Adikpo in Nigeria. It is discovered that the pozolanic properties of RHA varies based on their source location. Samples from Ogoja where found to have the highest pozzolanic properties followed by Abakaliki, Adani, and Adikpo, their silica content was found to be 84.55, 76.3, 70.12, 70.11, respectively. RHA was used to replace cement in concrete at 5, 10,15,20,25 and 30%. The compressive strength was determined and the values are as follows; And the compressive strength values at 28 days was found to be in the range of 37-42N/mm2 at 5%RHA, 35-39.5N/mm2 at 10%RHA, 30-34.5N/mm2 at 15%RHA, 27-29N/mm2 at 20%RHA, 22-25.6N/mm2 at 25% RHA and 21-24N/mm2 at 30% RHA compared to the controlled sample with a strength value of 42.64N/mm2. Cylindrical columns concrete of size 100mm diameter by 200mm long were moulded and stored in water for 28 days before testing for tensile splitting strength. The values determined from the split tensile test are as follows; 2.1-3.1N/mm2 at 5%RHA, 2.1-2.5N/mm2 at 10% RHA, 1.8-2.10 N/mm2 at 15% RHA, 1.2-1.7 N/mm2 at 20%RHA, 1.1-1.3 N/mm2 at 25% RHA and 0.62-0.9 N/mm2 at 30% RHA while the results of the controlled sample is 3.1 N/mm2.From the results above it can be deduced that source location influences the chemical properties of RHA strength characteristics of the Concrete with RHA as partial replacement.
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Coelho, Marco A., André Rosa, Nádia Rodrigues, Álvaro Fonseca, and Paula Gonçalves. "Identification of Mating Type Genes in the Bipolar Basidiomycetous Yeast Rhodosporidium toruloides: First Insight into the MAT Locus Structure of the Sporidiobolales." Eukaryotic Cell 7, no. 6 (April 11, 2008): 1053–61. http://dx.doi.org/10.1128/ec.00025-08.
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ABSTRACT Rhodosporidium toruloides is a heterothallic, bipolar, red yeast that belongs to the Sporidiobolales, an order within a major lineage of basidiomycetes, the Pucciniomycotina. In contrast to other basidiomycetes, considerably less is known about the nature of the mating type (MAT) loci that control sexual reproduction in this lineage. Three genes (RHA1, RHA2, and RHA3) encoding precursors of the MAT A1 pheromone (rhodotorucine A) were previously identified and formed the basis for a genome walking approach that led to the identification of additional MAT genes in complementary mating strains of R. toruloides. Two mating type-specific alleles encoding a p21-activated kinase (PAK; Ste20 homolog) were found between the RHA2 and RHA3 genes, and identification in MAT A2 strains of a gene encoding a presumptive pheromone precursor enabled prediction of the structure of rhodotorucine a. In addition, a putative pheromone receptor gene (STE3 homolog) was identified upstream of RHA1. Analyses of genomic data from two closely related species, Sporobolomyces roseus and Sporidiobolus salmonicolor, identified syntenic regions that contain homologs of all the above-mentioned genes. Notably, six novel pheromone precursor genes were uncovered, which encoded, similarly to the RHA genes, multiple tandem copies of the peptide moiety. This suggests that this structure, which is unique among fungal lipopeptide pheromones, seems to be prevalent in red yeasts. Species comparisons provided evidence for a large, multigenic MAT locus structure in the Sporidiobolales, but no putative homeodomain transcription factor genes (which are present in all basidiomycetous MAT loci characterized thus far) could be found in any of the three species in the vicinity of the MAT genes identified.
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islam, Kazi, and Zahid Hossain. "Use of Rice Husk Ash (RHA) as a Supplementary Cementitious Material in Producing Normal Concrete." MATEC Web of Conferences 271 (2019): 07007. http://dx.doi.org/10.1051/matecconf/201927107007.
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With the continuous increase of scarcity of the natural construction material sources and environmental awareness, utilization of wastes/by-products in the construction industry has become an attractive field of study. Several industrial by-products produced from different manufacturing processes have been considered for various usages in the construction field. This paper briefly describes the potential use of Rice Husk Ash (RHA) as Supplementary Cementitious Materials (SCM). Here, three different grades of RHA (600-RHA, 150-RHA, and 44-RHA) in two different percentages (10 % and 20 %) of replacement of Type I Ordinary Portland Cement (OPC) were investigated. Laboratory tests on the fresh concrete mix as well as the mechanical properties of the hardened concrete were performed. It was observed that coarser RHA-modified concrete (600-RHA and 150-RHA) showed reduced strength properties while finer RHA (44-RHA) exhibited improved concrete properties. Moreover, the incorporation of RHA in concrete was found to be effective in mitigating alkaline expansion.
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Lee, Y. S., F. H. Wee, K. Y. You, Z. Liyana, C. Y. Lee, Mas Elyna Azol, M. H. Ramli, et al. "Study of single layer microwave absorber based on rice husk Ash/CNTs composites." Indonesian Journal of Electrical Engineering and Computer Science 14, no. 2 (May 1, 2019): 929. http://dx.doi.org/10.11591/ijeecs.v14.i2.pp929-936.
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<span>This paper presents the study of microwave absorption single layer microwave absorber based on rice husk ash (RHA) with additional carbon nanotubes (CNTs) filler loading into the composites. The relative permittivity of RHA and CNTs composites (RHA/CNTs) were measured by using Agilent high temperature probe and 85070E software. The CST-MWS software is used to design and evaluate the microwave absorption of RHA and RHA/CNTs with metal backed plate. The microwave absorption of simulated and measured results is compared. The RHA microwave absorber only absorbed maximum, -8 dB at 10.8 GHz of the incident electromagnetic radiation and the RHA/CNTs absorbed less than -15 dB with wider bandwidth over 10.8 GHz to 12.8 GHz compare with RHA composites single layer microwave absorber. The results indicated that the RHA/CNTs composites have enhanced the microwave absorption of RHA composites.</span>
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Munawar, Mehmood, Ammad H. Khan, Zia U. Rehman, Abdur Rahim, Mubashir Aziz, Sultan Almuaythir, Bothaina S. I. A. El Kheir, and Farhan Haider. "Micro to Nanolevel Stabilization of Expansive Clay Using Agro-Wastes." Advances in Civil Engineering 2023 (April 19, 2023): 1–15. http://dx.doi.org/10.1155/2023/2753641.
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The circular economy encourages the production and consumption of sustainable embankment geomaterials and their blends utilizing recycled waste materials in roads, railway tracks, airfields, and underground structures. Geomaterials comprising high-plastic soft expansive clay pose excessive settlement during cyclic traffic/railway/airfield loading resulting in uneven geometry of overlying layers. This paper demonstrates multiobjective optimized improvement of expansive clay (C) geotechnical characteristics by cost-effective agro-wastes additives at microlevel (by 3% to 12% rice husk ash, i.e., RHA), nanolevel (by 0.6% to 1.5% rice husk derived green nano-SiO2, i.e., NS), and synergistic micro to nanolevel (NS-RHA). The swell potential, resilient modulus (MR), initial elastic modulus (Es), unconfined compressive strength (UCT), and California bearing ratio (CBR) of C and its blends were determined. The chemical characterization of C and its blends were conducted through Fourier transform infrared spectroscopy (FTIR) and optical microscopic tests. The outcome of this study depicted that the cost ratio for the optimized composite, i.e., (1.2% NS-9% RHA)/(9% RHA) is 1.22 whereas stiffness ratio MR (NS-RHA)/MR(RHA) and Es (NS-RHA)/Es(RHA) and strength ratio UCT(NS-RHA)/UCT(RHA) and CBR(NS-RHA)/CBR(RHA) were found to be 2.0, 1.64, 2.17, and 2.82, respectively. FTIR revealed the chemical compatibility between C, RHA, & NS from durability perspective. Cost-stiffness results of this study can be applied by geotechnical experts to economize the green stabilization of C by use of agro-waste for sustainable development.
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Berktas, Ilayda, Ojas Chaudhari, Ali Nejad Ghafar, Yusuf Menceloglu, and Burcu Saner Okan. "Silanization of SiO2 Decorated Carbon Nanosheets from Rice Husk Ash and Its Effect on Workability and Hydration of Cement Grouts." Nanomaterials 11, no. 3 (March 8, 2021): 655. http://dx.doi.org/10.3390/nano11030655.
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Rice husk ash (RHA) having a porous sructure and a high amount of amorphous silica nanoparticles (4 nm) decorated on the surface of carbon nanosheets is a suitable and cheap candidate for the use of a grout additive. In this study, neat RHA and functionalized RHA (f-RHA) with three different loadings were successfully incorporated into the cement-bentonite based grouts by adjusting the water to cement ratio. The workability of the developed grouts having RHA-based additives was analyzed in terms of bleeding, density, flow spread, and Marsh cone time. Additionally, the thermal and prolongation of hydration performances of the cementitious grout were enriched by successful attachment of amino-silane functional groups on the RHA surface. The heat of hydration performances of RHA and functionalized RHA introduced cementitious grout composite were assessed by isothermal calorimetry tests, and especially the kinetics of hydration was increased by the addition of RHA. The presence of amino silane groups in f-RHA intensified the heat adsorption by reacting with cement constituents, and thus resulted in the retardation and reduction in the heat flow. Therefore, using an amino-silane coupling agent increased the induction period and hindered the heat of hydration compared to the reference grout. On the other hand, the incorporation of RHA and f-RHA into the cement matrix did not affect the thermal conductivity of the grouts.
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Zeng, Zong Qiang, He Ping Yu, Hong Chao Liu, Shuang Quan Liao, and Zheng Peng. "Fabrication of Rice Husk Ash/Natural Rubber Composite." Advanced Materials Research 393-395 (November 2011): 92–96. http://dx.doi.org/10.4028/www.scientific.net/amr.393-395.92.
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The preparation of rubber-based composite from agricultural by-product is the main trend to upgrade the performance of rubber and reduce the cost. In this work, the rice husk ash/natural rubber (RHA/NR) composites were prepared by latex mixing process using the RHA modified with rare earth coupling agent. The mechanical properties, dynamic mechanical properties, thermal stability and morphology of RHA/NR composites were analyzed by universal testing machine, dynamic mechanical analyzer, thermo gravimetric analyzer and scanning electron microscope. The results indicate that previous modification of RHA with rare earth coupling agent can improve the dispersion of RHA in NR matrix significantly and increase the interaction between RHA particles and NR matrix and thus upgrade the mechanical properties and anti-oxidative behaviors of RHA/NR composite. The RHA/NR composite of highest mechanical properties and anti-oxidative behaviors can be obtained with a RHA loading of 4 per hundred rubber.
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Hadipramana, Josef, Abdul Aziz Abdul Samad, Ahmad Zaidi Ahmad Mujahid, Noridah Mohammad, and Fetra Venny Riza. "Effect of Uncontrolled Burning Rice Husk Ash in Foamed Concrete." Advanced Materials Research 626 (December 2012): 769–75. http://dx.doi.org/10.4028/www.scientific.net/amr.626.769.
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Recently, foamed concrete has become a popular construction material that can be used in wide range of constructions application. Whilst the Rice Husk Ash (RHA) as agro-waste is contain high amount of silicon dioxide. RHA is produced in significant amount every year from agriculture countries. RHA has potential as a material to produce foamed concrete. In this research RHA has been used as a replacement for fine aggregate which used in construction as ordinary concrete material. In this study, foamed concrete with target density 1400, 1600 and 1800 kg/m3 has been produced. The compressive strength of foamed concrete with RHA has been tested. Concrete with Ratio 1:3 of RHA/Sand has higher compressive strength than ratios 3:1 and 2:2 of RHA/sand for every density. XRD and XRF test has been used to determinate chemical composition and crystalline structure of RHA. The result showed that RHA is an amorphous material which amorphous is important thing to pozzolanic process when hydration of cement paste. SEM and EDS test has been conducted to determine microstructure and chemical composition on microstructure of RHA foamed concrete. Amorphous RHA incorporating cement paste produces pozzolanic reaction. It is reduces the porosity and width of interfacial zone in such a way the density is increase.
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Tian, Erbu, Y. Frank Chen, Yizhou Zhuang, and Wuhua Zeng. "Effects of rice husk ash on itself activity and concrete behavior at different preparation temperatures." Materials Testing 63, no. 11 (November 1, 2021): 1070–76. http://dx.doi.org/10.1515/mt-2021-0046.
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Abstract This paper aims to investigate the effects of rice husk ash (RHA) on itself activity and its concrete performance at different preparation temperatures for which three temperatures of 650 °C, 800 °C, and 900 °C were considered. To find a reasonable particle size, the effect of the particle size of the RHA on the workability of concrete at various grinding times was studied. A series of experiments were carried out to study the characteristics of the RHA, including X-ray fluorescence, XRD, ESEM, and an activity test. The carbonation resistance and frost resistance of concrete incorporating RHA were also investigated, where 10 and 30 wt.-% of cement was considered. The results show that the surface area of the RHA first increases and then decreases with grinding time. When the RHA is ground for 30 min, its surface area is largest and the workability of its mixture is also best. The burning temperature has little effect on the amount of SiO2. Although the structure and activity of SiO2 in RHA change at different burning temperatures, the performance of concrete incorporating RHA is higher than that of control concrete without RHA. With the same content of RHA, both carbonization resistance and frost resistance decrease with an increasing burning temperature of RHA. At the same burning temperature, both carbonization resistance and frost resistance increase with an increasing amount of RHA. Among all types of mixtures, the mixture incorporating 30 % RHA burned at 650 °C (i. e., RHA650) yields the best performance.
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Lawrence, Paul, and Elizabeth Rieder. "Identification of RNA Helicase A as a New Host Factor in the Replication Cycle of Foot-and-Mouth Disease Virus." Journal of Virology 83, no. 21 (August 26, 2009): 11356–66. http://dx.doi.org/10.1128/jvi.02677-08.
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ABSTRACT Foot-and-mouth disease virus (FMDV), as with other RNA viruses, recruits various host cell factors to assist in the translation and replication of the virus genome. In this study, we investigated the role of RNA helicase A (RHA) in the life cycle of FMDV. Immunofluorescent microscopy (IFM) showed a change in the subcellular distribution of RHA from the nucleus to the cytoplasm in FMDV-infected cells as infection progressed. Unlike nuclear RHA, the RHA detected in the cytoplasm reacted with an antibody that recognizes only the nonmethylated form of RHA. In contrast to alterations in the subcellular distribution of nuclear factors observed during infection with the related cardioviruses, cytoplasmic accumulation of RHA did not require the activity of the FMDV leader protein. Using IFM, we have found cytoplasmic RHA in proximity to the viral 2C and 3A proteins, which promotes the assembly of the replication complexes, as well as cellular poly(A) binding protein (PABP). Coimmunoprecipitation assays confirmed that these proteins are complexed with RHA. We have also identified a novel interaction between RHA and the S fragment in the FMDV 5′ nontranslated region. Moreover, a reduction in the expression of RHA, using RHA-specific small interfering RNA constructs, inhibited FMDV replication. These results indicate that RHA plays an essential role in the replication of FMDV and potentially other picornaviruses through ribonucleoprotein complex formation at the 5′ end of the genome and by interactions with 2C, 3A, and PABP.
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Liu, Chun, Cong-Ying Jiang, Deng-Deng Wang, and Deng Chen. "Microstructure of High Volume Rice Husk Ash Concrete." Science of Advanced Materials 14, no. 5 (May 1, 2022): 920–26. http://dx.doi.org/10.1166/sam.2022.4240.
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Rice hush ash (RHA) is a promising supplementary cementitious material (SCM) and the application of concrete containing high volume SCMs is one of effective strategies to relieve the carbon emission from building industry. The effect of RHA contents up to 60% to replace cement on the microstructure evolution of concrete has been experimentally investigated through the compressive strength, nanoindentation and scanning electron microscope methods. The results indicate that the utilization of RHA reduces the early compressive strengths of concrete, but less than 40% RHA increases the later compressive strengths, the high volume RHA concrete showing the great development potentials of strengths. The utilization of less than 40% RHA improves the internal structures because of the active effect of RHA and the filling effect of unhydrated RHA. The utilization of RHA increases the proportions of high density calcium silicate hydrate (HD C–S–H) and ultra-high density C–S–H (UHD C–S–H) due to the fact that C–S–H produced by RHA is mainly composed of HD C–S–H and UHD C–S–H, and also improves the interfacial transition zone.
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Hossain, MB, KM Shaad, MS Rahman, and P. Bhowmik. "Influence of Rice Husk Ash on the Properties of Concrete." Journal of Environmental Science and Natural Resources 9, no. 1 (November 8, 2016): 29–33. http://dx.doi.org/10.3329/jesnr.v9i1.30287.
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This research was carried out to investigate various physical properties of Rice Husk Ash (RHA) and, some physical and mechanical properties of concrete incorporating RHA in different proportions. The concrete specimens were tested at 7, 21 and 28 days after curing. Test results revealed that the specific gravity of RHA was found lower than that of sand. The density of concrete containing RHA was recorded between 80-110 lb.ft-3, which is lower than conventional concrete. Water absorption was found increasing with the increase of RHA content in concrete specimens. There were significant variations in compressive strength values of concrete containing 5%, 10% and 20% volume of RHA. The compressive strength of 5% RHA specimen was 150-200% higher than that of other specimens. Hence, upto 5% replacement of RHA could be recommended for making normal lightweight concrete. The splitting tensile strength was about 9-10% of compressive strength. It was concluded that upto 5% RHA can be used effectively in making normal lightweight concrete. The higher percentage of RHA could be used in making non-structural concrete where the strength of concrete is not concerned.J. Environ. Sci. & Natural Resources, 9(1): 29-33 2016
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Bangwar, D. K., A. Saand, M. A. Keerio, M. A. Soomro, and N. Bhatti. "Development of an Amorphous Silica from Rice Husk Waste." Engineering, Technology & Applied Science Research 7, no. 6 (December 18, 2017): 2184–88. http://dx.doi.org/10.48084/etasr.1534.
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This article presents a study on the development of amorphous silica from Rice Husk (RH) waste. For ascertaining the optimum proportion of temperature and burning duration required for the development of an amorphous silica from RH waste, different Rice Husk Ash (RHA) samples, i.e. RHA (500oC-1.5hr), RHA (500oC-2hr), RHA (600oC-1.5hr), RHA (600oC-2hr), RHA (700oC-1.5hr), RHA (700oC-2hr), RHA (800oC-1.5hr), RHA (800oC-2) and RHA (900oC-1hr) were extracted by burning the husk at different temperatures and durations. Energy Dispersive Spectrometry (EDS) analysis was carried out for ascertaining the existence of main and insignificant elements in the RHAs samples and it was noticed that the extracting of silicon dioxide (SiO2) was exclusively dependent on the temperature and burning duration. After EDS, X-ray Diffraction (XRD) analysis was used to find out the crystalline and non-crystalline nature of obtained silica at different temperatures and burning durations. Through EDS and XRD, it has been found that that the extracted Rice Husk Ash at the temperature of 800oC for 2hr is rich in amorphous SiO2 content, i.e. 91.74% which meets the requirements of ASTM 618-03 for a pozzolanic material.
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Ahmad Mujahid, Ahmad Zaidi, Josef Hadipramana, Abdul Aziz Abdul Samad, Noridah Mohamad, and Fetra Venny Riza. "Potential of RHA in Foamed Concrete Subjected to Dynamic Impact Loading." Key Engineering Materials 594-595 (December 2013): 395–400. http://dx.doi.org/10.4028/www.scientific.net/kem.594-595.395.
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In relation to the conventional concrete then foamed concrete (FC) is weaker. Therefore FC was added by Rice Husk Ash (RHA) to alter the strength without eliminating its characteristic as aerated concrete. Actually function of RHA is substitute the sand partly. The strength of concrete affects to prevent the dynamic impact loading. However FC as aerated concrete can absorb energy impact by its porosity. Both of characteristics were presented in this investigation. SEM and EDS detected that pozzolanic reaction was done when FC was processing hydration of cement in admixture. The presence of RHA increased the strength of concrete owing to cement hydration process and pozzolanic reactivity of RHA. The result of impact loading on slab FC target displayed that FC with RHA was more shallow than without RHA. Beside of that local damage showed that FC with RHA denser and is not impression of fragments than FC without RHA.
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Boontawee, Kantapong, Withit Pansuk, Luangvaranunt Tachai, and Katsuyoshi Kondoh. "Effect of Rice Husk Ash Silica as Cement Replacement for Making Construction Mortar." Key Engineering Materials 775 (August 2018): 624–29. http://dx.doi.org/10.4028/www.scientific.net/kem.775.624.
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Rice husk ash (RHA) is used as a replacement to cement to produce mortar. The effect of 5, 10, and 15wt% addition to the density and compressive strength of mortar is investigated. It was found that with the increasing addition of RHA causes the decrease of compressive strength and density of mortars. Compressive strength of mortar drops with addition of RHA, from a value of 42 MPa of no RHA addition, to 24 MPa of 15wt% RHA addition. Reduction in compression strength may be due to the decrease in density, which arises from porous RHA. This is more dominant in mortar made from addition of RHA without prior acid treated. Carbon residue and impurity in RHA further reduce the compressive strength of mortar. In addition, this research validate the use of a more environmentally friendly citric acid for partially removal of oxide impurities prior to burning the rice husk.
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Yu, Cheng Cheng, De Ling Wang, Kang Yang, and Shu Lei Li. "Character and Development Analysis of Foam Concrete Cooperating Rice Husk Ash." Advanced Materials Research 941-944 (June 2014): 901–4. http://dx.doi.org/10.4028/www.scientific.net/amr.941-944.901.
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The effect of rice husk ash (RHA) on foam concrete was studied. Firstly, performance and application of foam concrete was introduced in this paper. Secondly the character of RHA was described. RHA contains about 90% amorphous silica, which has high pozzolanic activity. Partial replacement of cement by RHA can enhance the strength of foam concrete in later age and improve durability, homogeneity and corrosion resistance. It also improves the pore structure of foam concrete, thermal insulation and sound absorption performance. Finally, development of foam concrete mixed with RHA was analyzed from following aspects: selecting and processing materials such as foaming agents, RHA and cement; optimizing production process of foam concrete. And since RHA is the major agricultural by-products of rice, it can reduce cost and environmental impact by replacing cement in foam concrete. As an environment friendly material, foam concrete cooperating RHA has great potential in construction field.
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Riza, F. V., J. Hadipramana, I. A. Rahman, and A. Faisal. "Particle Size and Microstructure Characterization of Uncontrolled Burning Rice Husk Ash (RHA) as Pozzolanic Material." Materials Science Forum 1029 (May 2021): 97–103. http://dx.doi.org/10.4028/www.scientific.net/msf.1029.97.
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RHA has been the subject of investigation for its pozzolanic activity that heavily linked to the controlled temperature burning process in order to achieve amorphous form of silica. This paper present the characterization of RHA that was taken directly from the boiler of rice mill with uncontrolled burning temperature. Particle size analysis revealed grinding process of RHA could significantly curb the diameter size and increased specific surface area. Microstructure analysis suggest that RHA is very porous and EDX test showed the chemical content of RHA. The prospect of using uncontrolled burnt RHA as part of construction material is feasible.
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Kamau, John, Ash Ahmed, Fraser Hyndman, Paul Hirst, and Joseph Kangwa. "Influence of Rice Husk Ash Density on the Workability and Strength of Structural Concrete." European Journal of Engineering Research and Science 2, no. 3 (March 30, 2017): 36. http://dx.doi.org/10.24018/ejers.2017.2.3.292.
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Supplementary cementitious materials (SCMs) have been known to improve the properties of fresh and hardened concrete, and at the same time enhance the sustainability of concrete. Rice husk Ash (RHA), is one such material, but has neither been widely studied nor applied in practice. This work investigated the effect of the density of RHA on the workability and compressive strength of fresh and hardened RHA-replaced concrete respectively. Cement was replaced with RHA in concrete by weight (RHA-W) and by volume (RHA-V) at steps of 0%, 5%, 7.5%, 10%, 15%, 20%, 25% and 30%. The 0% replacement was used as the reference point from which performances were measured. Results showed that unlike the characteristic of other established pozzolans, RHA significantly reduced the workability of wet concrete and the rate of compressive strength gain over curing time due to a high water demand that is caused by the increased volume of replaced concrete, which results from its low density. Workability reduced with increased replacement for both RHA-W and RHA-V. Replacements of above 15% were not possible for the RHA-W due to the high water demand. However, replacements of up to 30% were achieved for the RHA-V. RHA-W specimens achieved lower compressive strengths and were observed to gain strength at a lower rate over the 28 to 91-days period of curing compared to RHA-V specimens. This behavior was attributed to the shortage of water that is necessary for the hydration of cement and subsequent pozzolanic reaction, which is the basis of the contribution that is made to the strength and performance of concrete by SCMs. However, the compressive strengths achieved were above the study’s target concrete strength of class C32/40 at 91 days, which is among those classes that are listed as being durable and suitable for structural applications. A conclusion that RHA should supplement cements by volumetric replacement rather than simple substitution by weight was drawn.
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Kamau, John, Ash Ahmed, Fraser Hyndman, Paul Hirst, and Joseph Kangwa. "Influence of Rice Husk Ash Density on the Workability and Strength of Structural Concrete." European Journal of Engineering and Technology Research 2, no. 3 (March 30, 2017): 36–43. http://dx.doi.org/10.24018/ejeng.2017.2.3.292.
Full textAbstract:
Supplementary cementitious materials (SCMs) have been known to improve the properties of fresh and hardened concrete, and at the same time enhance the sustainability of concrete. Rice husk Ash (RHA), is one such material, but has neither been widely studied nor applied in practice. This work investigated the effect of the density of RHA on the workability and compressive strength of fresh and hardened RHA-replaced concrete respectively. Cement was replaced with RHA in concrete by weight (RHA-W) and by volume (RHA-V) at steps of 0%, 5%, 7.5%, 10%, 15%, 20%, 25% and 30%. The 0% replacement was used as the reference point from which performances were measured. Results showed that unlike the characteristic of other established pozzolans, RHA significantly reduced the workability of wet concrete and the rate of compressive strength gain over curing time due to a high water demand that is caused by the increased volume of replaced concrete, which results from its low density. Workability reduced with increased replacement for both RHA-W and RHA-V. Replacements of above 15% were not possible for the RHA-W due to the high water demand. However, replacements of up to 30% were achieved for the RHA-V. RHA-W specimens achieved lower compressive strengths and were observed to gain strength at a lower rate over the 28 to 91-days period of curing compared to RHA-V specimens. This behavior was attributed to the shortage of water that is necessary for the hydration of cement and subsequent pozzolanic reaction, which is the basis of the contribution that is made to the strength and performance of concrete by SCMs. However, the compressive strengths achieved were above the study’s target concrete strength of class C32/40 at 91 days, which is among those classes that are listed as being durable and suitable for structural applications. A conclusion that RHA should supplement cements by volumetric replacement rather than simple substitution by weight was drawn.
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Bui, Le Anh Tuan, Chun Tsun Chen, Chao Lung Hwang, and Mintar Fransiscus. "Application of Residual Rice Husk Ash from Vietnam as a Supplementary Cementitious Material in Concrete." Advanced Materials Research 347-353 (October 2011): 2829–33. http://dx.doi.org/10.4028/www.scientific.net/amr.347-353.2829.
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The residual RHA from Vietnam is used to test the likely application in cement and concrete. The characteristics, quality and influence of RHA on the quality of concrete are investigated in this investigation. The workability, strength and durability of concrete added with ground RHA satisfy with the relevant standards and requirements. It indicates that the ground RHA in this study can be used as a good supplementary cementious material. Therefore, it is possible to obtain RHA concrete with comparable properties than those of the control specimen (without RHA) with a lower consumption of cement, thus reducing the CO2 emissions during the production of cement and the environmental and disposal problem of the ash can also be diminished. Moreover, while the results will be able to substantiate the viability of application of RHA in concrete industry under the prevailing conditions in Vietnam, they are also expected to be especially useful for future studies on RHA in a specific condition in this country.
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Borges, Paulo H. R., Vitor A. Nunes, Tulio H. Panzera, Giorgio Schileo, and Antonio Feteira. "The Influence of Rice Husk Ash Addition on the Properties of Metakaolin-Based Geopolymers." Open Construction and Building Technology Journal 10, no. 1 (June 28, 2016): 406–17. http://dx.doi.org/10.2174/1874836801610010406.
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This paper investigates the replacement of metakaolin (MK) with rice husk ash (RHA) in the production of alkali-activated binders or geopolymers. The influence of the RHA addition on compressive and flexural strength, as well as water absorption and apparent porosity were determined, in terms of the percentage of RHA in the mixture and molar ratios of the mixes. Fourier Transform Infrared (FTIR) spectroscopy and Energy Dispersive spectroscopy (EDS) were carried out to assess the changes in the microstructure of the geopolymer matrices with the RHA addition. Results have shown that RHA may be a supplementary precursor for geopolymers. The composition of the geopolymer matrices containing 0-40% RHA is very similar, which indicates that the additional Si provided by RHA is not incorporated to the geopolymer matrix. In addition, geopolymers with RHA content higher than 40% present a plastic behavior, characterized by extremely low strength and high deformation, which can be attributed to the formation of silica gel in formulations containing variable Si/Al ratio.
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Wongwitthayakool, Panjaporn, Tanittha Sintunon, Wichaya Tanagetanasombat, Pongkarn Soonthornchai, and Ahmed A. Abbas. "Flexural Strength and Dynamic Mechanical Behavior of Rice Husk Ash Silica Filled Acrylic Resin Denture Base Material." Key Engineering Materials 824 (October 2019): 94–99. http://dx.doi.org/10.4028/www.scientific.net/kem.824.94.
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Silica extracted from rice husk ash (RHA-Si) by pretreatment with hydrochloric acid followed by calcination at 700°C, was prepared. It was investigated with regard to its chemical composition and structure using X-Ray Fluorescence spectroscopy (XRF) and X-Ray Diffractometry (XRD). RHA-Si (0, 0.25, 0.5 and 1% w/w) was incorporated into poly(methyl methacrylate) (PMMA) or acrylic resin powder. Microhardness, flexural strength and dynamic mechanical properties of RHA-Si filled PMMA were then determined. The chemical composition analysis showed that RHA-Si contains a large amount of silica with an amorphous structure. The microhardness of acrylic resin filled with RHA-Si does not change significantly with increasing RHA-Si loading. Flexural strength of filled acrylic resin increases with increasing RHA-Si loadings up to 0.25% w/w. It then decreases with increasing RHA-Si loadings. Dynamic mechanical behavior illustrates that polymer-filler interactions play an important role in reinforcement.
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Corbaz, J., B. Barimani, and F. Vauclair. "Early aseptic loosening of a press-fit radial head prosthesis – A case series of 6 patients." Journal of International Medical Research 51, no. 4 (April 2023): 030006052211358. http://dx.doi.org/10.1177/03000605221135881.
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Objective Radial head arthroplasty (RHA) is the principal treatment option for comminuted radial head (RH) fractures. Here, we present six cases of failed RHA using a modular monopolar press-fit RHA that was subsequently withdrawn from the market because it was associated with a high incidence of loosening. Methods We retrospectively collected data from six patients who had received Radial Head Prothesis SystemTM at our centre between July 2015 and June 2016. The average follow-up was 40 months. Results Aseptic loosening of the stem affected five (83%) of the six RHA. Four of these were symptomatic and RHA removal was performed. For these patients, the pain subsided and their elbow range of motion (ROM) improved. Conclusion While the ideal design for an RHA is still debatable, RHA is an efficient treatment option that restores elbow stability and function after a comminuted RH fracture. Importantly, removal of the prosthesis is an effective remedy following RHA associated elbow pain and decreased ROM.
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Endale, Solomon Asrat, Woubishet Zewdu Taffese, Duy-Hai Vo, and Mitiku Damtie Yehualaw. "Rice Husk Ash in Concrete." Sustainability 15, no. 1 (December 22, 2022): 137. http://dx.doi.org/10.3390/su15010137.
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This study conducted an extensive literature review on rice husk ash (RHA), with a focus on its particle properties and their effects on the fresh, mechanical, and durability properties of concrete when used as a partial cement replacement. The pozzolanic property of RHA is determined by its amorphous silica content, specific surface area, and particle fineness, which can be improved by using controlled combustion and grinding for use in concrete. RHA particle microstructures are typically irregular in shape, with porous structures on the surface, non-uniform in dispersion, and discrete throughout. Because RHA has a finer particle size than cement, the RHA blended cement concrete performs well in terms of fresh properties (workability, consistency, and setting time). Due to the involvement of amorphous silica reactions, the mechanical properties (compressive, tensile, and flexural strength) of RHA-containing concrete increase with increasing RHA content up to a certain optimum level. Furthermore, the use of RHA improved the durability properties of concrete (water absorption, chloride resistance, corrosion resistance, and sulphate resistance). RHA has the potential to replace cement by up to 10% to 20% without compromising the concrete performance due to its high pozzolanic properties. The use of RHA as a partial cement replacement in concrete can thus provide additional environmental benefits, such as resource conservation and agricultural waste management, while also contributing to a circular economy in the construction industry.
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Raheem, Akeem Ayinde, and Mutiu A. Kareem. "Chemical Composition and Physical Characteristics of Rice Husk Ash Blended Cement." International Journal of Engineering Research in Africa 32 (September 2017): 25–35. http://dx.doi.org/10.4028/www.scientific.net/jera.32.25.
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Applications of agricultural by-product as substitute for non-renewable material in cement production are desirable in stimulating socio-economic development. In this study, Rice Husk Ash (RHA) blended cement was produced by replacing 5%, 7%, 11.25%, 15%, 20.25% and 25% by weight of Ordinary Portland Cement (OPC) clinker with RHA. The cement without RHA serves as the control. The chemical compositions of RHA, OPC-clinker and the blended cements were determined using X-ray fluorescence analyzer. The physical characteristics of RHA blended cements that were considered are fineness, soundness, consistency, initial and final setting times and compressive strength at 2, 7, 28, 56 and 90 curing ages. The results showed that RHA is a suitable material for use as a pozzolan as it satisfied the minimum requirement by having the sum of SiO2, Al2O3 and Fe2O3 of more than 70%. Incorporation of RHA led to an increase in the composition of SiO2 and reduction in that of CaO. An increase in RHA content showed a decrease in compressive strength at early ages and slightly increase at a later age (90 days). The blended cement produced with lower levels of RHA replacement conforms to standard specifications specified in BS EN 197-1:2000, NIS 439:2000 and ASTM C 150-02. The minimum Strength Activated Index (SAI) of 75% at the age of 28 days of curing as specified by ASTM C 618 was satisfied by RHA replacement of up to 15%. It was concluded that blended cement with the maximum of 15% RHA content is suitable for use for structural purposes.
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Ehwailat, Khaled Ibrahim Azarroug, Mohd Ashraf Mohamad Ismail, and Ali Muftah Abdussalam Ezreig. "Novel Approach for Suppression of Ettringite Formation in Sulfate-Bearing Soil Using Blends of Nano-Magnesium Oxide, Ground Granulated Blast-Furnace Slag and Rice Husk Ash." Applied Sciences 11, no. 14 (July 19, 2021): 6618. http://dx.doi.org/10.3390/app11146618.
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The treatment of sulfate-bearing soil with calcium-based stabilizers such as cement or lime often results in ettringite formation, consequently leading to swelling and strength deterioration. Ettringite formation has negative environmental and economic effects on various civil engineering structures. This study was conducted to investigate the use of different materials (nano–magnesium oxide (M), ground granulated blast-furnace slag (GGBS), and rice husk ash (RHA)) for gypseous soil stabilization to prevent ettringite formation. Various tests were performed, including flexural strength, unconfined compression strength, linear expansion, and microstructure analysis (SEM/EDX), on lime (L)-, (M)-, (M-RHA)-, (M-GGBS)-, and (M-GGBS-RHA)-stabilized gypseous soil samples to determine their properties. The results indicated that the swelling rates of the soil samples mixed with 20% M-RHA, M-GGBS, and M-GGBS-RHA binders were much lower (less than 0.01% of volume change) than those of the soil samples mixed with 10% and 20% lime-stabilized binders after a curing period of 90 days. Meanwhile, the strengths of the soil samples mixed with 20% of M-RHA, M-GGBS, and M-GGBS-RHA soil specimens after soaking of 90 days were obviously higher (with a range from 2.7–12.8 MPa) than those of the soil samples mixed with 20% of lime-stabilized binder. The SEM and EDX results showed no ettringite formation in the M-RHA-, M-GGBS-, and M-GGBS-RHA-stabilized soils. Overall, the test results proved the potential of M-RHA, M-GGBS, and M-GGBS-RHA as effective soil stabilizers.
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Walker, C. D., R. W. Rivest, M. J. Meaney, and M. L. Aubert. "Differential activation of the pituitary-adrenocortical axis after stress in the rat: use of two genetically selected lines (Roman low- and high-avoidance rats) as a model." Journal of Endocrinology 123, no. 3 (December 1989): 477–85. http://dx.doi.org/10.1677/joe.0.1230477.
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ABSTRACT We have examined the activation of the pituitary-adrenal axis in two lines of rats, the Roman high (RHA)- and low (RLA)-avoidance rats known to be emotionally different. These rats are selected for rapid acquisition of a conditioned avoidance response (RHA) compared with failure to acquire this response (RLA). In this study the endocrine response (ACTH, corticosterone, aldosterone) of RLA and RHA rats to two types of stress was examined: exposure to openfield stress for 10 min (Op) or exposure to ether vapours for 3 min (E). Basal plasma ACTH concentrations were lower in RLA than in RHA rats (RLA: 110·8 ± 24·5 ng/l; RHA: 252·7 ± 60·8 ng/l, P<0·05) but the absolute values of ACTH reached after both types of stress were comparable between RLA and RHA rats. Plasma corticosterone and aldosterone under resting conditions were not different between RLA and RHA rats. Plasma corticosterone was higher in RLA following openfield stress (P<0·05) while no differences between RLA and RHA were observed after ether stress (RHA: basal = 66±14·nmol/l, Op =384± 55, E= 606± 75; RLA: basal=121±52, Op = 612 ±92, E= 698 ± 89). Stressinduced increases in plasma aldosterone were higher in the RLA line after both types of stress (RHA: basal = 175±36 pmol/l, Op = 546±53, E= 563± 47; RLA: basal = 272 ± 64, Op =1246 ± 91, E= 863 ± 72). Pituitary responsiveness to exogenous corticotrophinreleasing factor (CRF) in vivo and in vitro differed in the two lines: administration of ovine CRF (10 μg/kg body weight, i.p.) resulted in significant increases in ACTH secretion but the response was significantly lower in RHA rats (RHA: 511·1 ±41·5 ng/l; RLA: 831·4 ± 70·3 ng/l, P<0·01). Dispersed pituitary cells from the RHA line exhibited a smaller response to CRF (10 nmol/l) treatment in vitro compared with cells derived from the RLA rats (RHA: 750 ± 83% of control; RLA: 1374 ±79, P<0·01) suggesting differences in pituitary sensitivity to CRF between the two lines. Additional differences at the pituitary level were observed since the type II glucocorticoid receptor population in RHA rats was higher than in RLA rats (RHA: 246±13 fmol [3H]RU28362 bound/mg protein; RLA: 173±18, P<0·01). Similarly, hippocampal type I glucocorticoid receptor population was increased in RHA rats (RHA: 172·2 ± 8·3 fmol [3H]aldosterone bound/mg protein; RLA: 116·7±7·3, P< 0·01). It is concluded that first, differences in pituitary activity between RLA and RHA rats are distinct from changes observed at the adrenal level, secondly, increased stress-induced ACTH output in the RLA line is associated with enhanced pituitary sensitivity to CRF and possibly with diminished corticosterone inhibitory feedback action on CRF and ACTH secretion, and thirdly, the possible involvement of differences in the pattern of CRF secretion between RLA and RHA rats on resting pituitary ACTH secretion cannot be excluded. Journal of Endocrinology (1989) 123, 477–485
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S. P. YAP, U. J. ALENGARAM, M. Z. JUMAAT, and K. Y. FOONG. "Waste Materials in Malaysia for Development of Sustainable Concrete: A Review." Electronic Journal of Structural Engineering 13, no. 2 (June 1, 2013): 60–64. http://dx.doi.org/10.56748/ejse.131742.
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This paper discusses on the availability of waste materials in Malaysia and their potential use as building materials in the local construction industry. The waste materials discussed include fly ash (FA), oil palm kernel shell (OPKS), rice husk ash (RHA), palm oil fuel ash (POFA), quarry dust (QD), recycled ceramic, and recycled coarse aggregate (RCA). The past research on the use of these materials shows that structural grade concrete can be produced. . Similarly, the use of FA, RHA and POFA as partial replacement of cement or additional cementitious materials can be used to produce low to medium strength concrete as well as high strength concrete (HSC). In addition, lightweight OPKS enables it in the production of lightweight concrete (LWC). Recent research on the use of FA, RHA and palm oil clinker (POC) to produce geopolymer concrete is also producing results. In general, the utilization of these waste materials in concrete leads to sustainable concrete and reduces environmental impact from the manufacture of concrete using conventional materials such as crushed granite and cement
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Zeng, Zong Qiang, Hong Chao Liu, and He Ping Yu. "Reinforcement of NR with ENR Modified RHA." Advanced Materials Research 581-582 (October 2012): 663–67. http://dx.doi.org/10.4028/www.scientific.net/amr.581-582.663.
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The rice husk ash (RHA) was first modified with epoxidized natural rubber latex (ENRL) and then blended with natural rubber latex (NRL) to prepare NR/RHA composite. The morphological structure, thermal stability and dynamic properties were studied with multiple instruments. FTIR and TGA analysis showed that ENR was grafted onto the surface of RHA. The composite prepared with modified RHA showed better dispersity and reinforcement compared to the composite with unmodified RHA, and the glass-transition temperature tended to be higher.
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Njagi, John Alex Muthuri, Barrack Omondi Okoya, and Muthomi Munyua. "Investigation into the Effect of Rice Husk Ash in Partial Replacement of Cement in Concrete." East African Journal of Engineering 5, no. 1 (October 16, 2022): 181–94. http://dx.doi.org/10.37284/eaje.5.1.894.
Full textAbstract:
The purpose of this study was to investigate the properties of Rice Husk Ash (RHA) as a partial cement replacement material in concrete production based on analysis of its contribution to strength in comparison with Ordinary Portland Cement (OPC). The analysis was focused on: the chemical properties of RHA, workability, density, compressive strength, and tensile strength of concrete. The RHA was obtained from Mwea, Kirinyaga County, Kenya and burned in a kiln to produce white ash which was tested. Chemical analysis to determine the pozzolanic properties of RHA was done using the Gravimetric method, Flame Photometry and Atomic Absorption Spectroscopy while particle size distribution of RHA was carried out using sieve analysis and hydrometer analysis. Concrete mixes with different ratios of OPC to RHA binder were cast into cuboid and cylindrical samples. The binder was made by replacing OPC with RHA at intervals of 10% by mass to a maximum of 50% replacement. A binder, sand, and ballast ratio of 1:1.5:3 were maintained with a constant water-cement ratio of 0.6. The cast samples were subjected to water curing on the third day at room temperature. Workability tests were performed on fresh concrete while compressive strength tests and tensile strength tests were performed on hardened concrete in all the mixes. The results were compared with OPC concrete. Results indicated that Kenyan RHA has high silica, alumina, and iron oxide content of about 92%. The workability slightly improves with 10% partial replacement of OPC with RHA but decreases with further addition of RHA. It was also deduced that the optimal binder mix was 10% partial replacement of OPC with RHA however the compressive strength was lower than the OPC concrete by 2.3%. The tensile strength of concrete increased with the addition of RHA up to an optimum of 10%.
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Mot, Sreyhor, Sophary Khin, Vibol Peuo, Panha Pok, and Pao Srean. "Rice Husk Ash Incorporation in Container Substrates Effect on Romaine Lettuce Plant Growth." AGRITROPICA : Journal of Agricultural Sciences 4, no. 1 (May 31, 2021): 30–37. http://dx.doi.org/10.31186/j.agritropica.4.1.30-37.
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Primary substrate components include peat moss, vermiculite, perlite, bark, and compost are commonly-used substrate in horticultural crop production.These substrate components are high cost due to the extreme cost of transportation, fuel for extraction, and processing. Local rice husk ash (RHA) as an alternative substrate component was used to evaluatethe growth of Romaine Lettuce plants in response to the application of different incorporations of RHA in container substrates. The test was conducted with a completely randomized design of four RHA treatment, rates at 0%, 10%, 30%, and 50% (by vol.), with 10 replicates. The results showed that plant stem elongation increased with decreased incorporations of RHA application. Although the fresh weight of plants(shoot or root)and number of leaves increased with the RHA application, no significant difference for the plant biomass produced (dry weight of root and shoot) betweenthe 30% and 50% RHA treatments. The RHA can be used as a local and low cost substrate component; and the incorporation of 30% (by vol.) RHA in container substrates is a certain amount for lettuce plant growth.
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Li, Jin, Peiyuan Chen, Haibing Cai, Ying Xu, and Chunchao Li. "Preliminary Study on the Utilization of RHA as a Performance Enhancer for Rubber Mortar." Materials 14, no. 12 (June 10, 2021): 3216. http://dx.doi.org/10.3390/ma14123216.
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In this study, rice husk ash (RHA) was explored as a strength enhancer for mortars containing waste rubber. The effects of RHA on the flow, mechanical strength, chloride resistance, and capillary absorption of rubber mortar were investigated by substituting up to 20% cement with RHA. The experimental results showed that the incorporation of rubber into mortar could be safely achieved by adding RHA as a cement substitute by up to 20% without compromising the compressive strength of mortar. Moreover, the RHA also exerted positive effects on the enhancement of the chloride resistance as well as the capillary absorption of rubber mortars, for which 15% RHA was found to be the optimal dosage.
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Avudaiappan, Siva, Supriya Prakatanoju, Mugahed Amran, Radhamanohar Aepuru, Erick I. Saavedra Flores, Raj Das, Rishi Gupta, Roman Fediuk, and Nikolai Vatin. "Experimental Investigation and Image Processing to Predict the Properties of Concrete with the Addition of Nano Silica and Rice Husk Ash." Crystals 11, no. 10 (October 12, 2021): 1230. http://dx.doi.org/10.3390/cryst11101230.
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The use of the combination of ultrafine rice husk ash (RHA) and nano silica (NS) enhances the compactness of hardened concrete, but there is still a lack of studies that address the effects of NS and RHA on the workability, mechanical properties and pore microstructure of concrete. This study mainly aims to investigate the influence of the pore size distribution in multiphysics concrete model modified by NS and RHA and to determine the workability and mechanical properties of concrete with NS and RHA. In this work, NS and RHA were used as 0, 5, 10, 15 and 20% replacements of ordinary Portland cement (OPC) in concrete grade M20. Concrete mixed with NS and RHA showed improved performance for up to 10% addition of NS and RHA. Further addition of NS and RHA showed a decrease in performance at 7, 14 and 28 days. The decrease in concrete porosity was also found to be up to 10% when adding NS and RHA to cement. Image processing was performed on the cement-based materials to describe the microstructure of the targeted material without damage. The results from the experimental and tomography images were utilized to investigate the concrete microstructure and predict its inner properties.
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Hadipramana, Josef, Abdul Aziz Abdul Samad, Ahmad Zaidi Ahmad Mujahid, Noridah Mohamad, and Fetra Venny Riza. "Contribution of RHA Granules as Filler to Improve the Impact Resistance of Foamed Concrete." Key Engineering Materials 594-595 (December 2013): 93–97. http://dx.doi.org/10.4028/www.scientific.net/kem.594-595.93.
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Foamed concrete as aerated concrete widely used in range of constructions application, no exception to structure shield. As structure shield is important to resist on impact loading. Whilst, Rice Husk Ash (RHA) as agro-waste potentials as filler for foamed concrete. RHA that is produced by uncontrolled burning under 700oC during ± 6 hours obtain the granules contain the carbon and porous. The granules of RHA may fill the porous in matrix foamed concrete without remove the characteristic the foamed concrete its self-as aerated concrete. This investigation RHA has been used as a replacement for fine aggregate. Target density 1800 kg/m3of foamed concrete both of with and without RHA have been produced to compare their strength and characteristic of impact resistance. SEM and EDS test has been conducted to determine microstructure and chemical composition of foamed concrete with RHA. The results showed that granules of RHA filled the porous and bonded with the denser part into matrix. The presence of granules of RHA has been changing the role of the air cell of porous in foamed concrete when it was subjected to impact loading. Also the granules of RHA give the foamed concrete denser without losing its characteristic of porous entirely.
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Jongpradist, Pornkasem, Watee Homtragoon, Raksiri Sukkarak, Warat Kongkitkul, and Pitthaya Jamsawang. "Efficiency of Rice Husk Ash as Cementitious Material in High-Strength Cement-Admixed Clay." Advances in Civil Engineering 2018 (June 21, 2018): 1–11. http://dx.doi.org/10.1155/2018/8346319.
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The potential and efficiency of using rice husk ash (RHA) to add up or partially replace Portland cement in deep cement mixing technique are examined. A series of unconfined compression tests on cement-RHA-stabilized clay are conducted to investigate the influence of RHA on the mixture properties. Special attention is paid to its efficiency for increasing the strength by partial cement replacement to obtain high-strength soil cement, and it is compared with fly ash. Test results indicate that up to 35% of RHA could be advantageously added up to enhance the strength if the cement content in the mixture is larger than 10%. The RHA enhances the strength of cement-admixed clay by larger than 100% at 28 days. For curing time of 14 and 28 days, the RHA exhibits higher efficiency on Portland cement replacement when the cement and overall cementitious contents are not less than 20 and 35%, respectively. The optimum condition for high-strength mixture is achieved when RHA is added to the 20% cement content mixture. When compared with fly ash of similar grain size, the efficiency of RHA is higher when the content to be added is greater than 15%. This indicates the suitability of RHA for use in high-strength soil-cement.
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Tian, Bo, Xiangguo Li, Yang Lv, Jinsheng Xu, Weinan Ma, Chenhao He, Yang Chen, et al. "Effect of Rice Husk Ash on the Properties of Alkali-Activated Slag Pastes: Shrinkage, Hydration and Mechanical Property." Materials 16, no. 8 (April 17, 2023): 3148. http://dx.doi.org/10.3390/ma16083148.
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In this paper, rice husk ash (RHA) with different average pore diameters and specific surface areas was used to replace 10% slag in the preparation of alkali-activated slag (AAS) pastes. The effect of RHA addition on the shrinkage, hydration, and strength of AAS pastes was studied. The results show that RHA with a porous structure will pre-absorb part of the mixing water during paste preparation, resulting in a decrease in the fluidity of AAS pastes by 5–20 mm. RHA has a significant inhibitory effect on the shrinkage of AAS pastes. The autogenous shrinkage of AAS pastes decreases by 18–55% at 7 days, and the drying shrinkage decreases by 7–18% at 28 days. This shrinkage reduction effect weakens with the decrease in RHA particle size. RHA has no obvious effect on the type of hydration products of AAS pastes, whereas RHA after proper grinding treatment can significantly improve the hydration degree. Therefore, more hydration products are generated and fills the internal pores of the pastes, which significantly improves the mechanical properties of the AAS pastes. The 28 day compressive strength of sample R10M30 (the content of RHA is 10%, RHA milling time is 30 min) is 13 MPa higher than that of blank sample.
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Awad, Abbas Y., Mohammed N. Ibrahim, and Mohamed K. Hussein. "Effects of Rice Husk Ash–Magnesium Oxide Addition on Wear Behavior of Aluminum Alloy Matrix Hybrid Composites." Tikrit Journal of Engineering Sciences 25, no. 4 (December 15, 2018): 15–22. http://dx.doi.org/10.25130/tjes.25.4.04.
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A336.0 aluminum alloy used to fabricate hybrid composites using rice husk ash (RHA) and MgO particles as reinforcement. The influence of the particles on the wear behavior of A336.0 aluminum alloy as a matrix that reinforced with MgO and RHA was investigated. Firstly, the rice husk burned at 700°C and then heat treated at 1100°C for 2 hrs. The ash characterized by X-ray florescence and X-ray diffraction. Less than 53 and 125 micron are the particle sizes of MgO and RHA respectively. The hybrid composites manufactured using stir casting method in two steps. A336.0 aluminum alloy reinforced with 4:0, 3:1, 2:2, 1:3 and 0:4 of RHA: MgO with 10 wt% total reinforcement phase. Optical microscope and X-ray diffraction were used to characterize the prepared hybrid composites. Dry sliding wear, hardness, apparent density, percentage of porosity and coefficient of friction were examined. Results indicated that porosity, apparent density and hardness enhanced with increasing MgO, while increasing wt% of RHA decreased the apparent density. Results indicated that with inceasing the applied load the wear rate of the composites was enhanced. Coefficient of friction varies inversely with applied load and wt% of RHA. Hardness increased with increasing RHA while the friction coefficient and the wear rate decreased. The minimum wear rates were at 10% RHA and Al-alloy-(RHA-MgO) [3:1] composites, while the minimum friction coefficients were at 10% RHA composites.
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Su, Tingting, Juan Wei, Jinmei Zhao, Yumei Jiang, Yang Bi, and Galitsyn George. "Comparative Assessment of Functional Components and Antioxidant Activities between Hippophae rhamnoides ssp. sinensis and H. tibetana Berries in Qinghai–Tibet Plateau." Foods 12, no. 2 (January 11, 2023): 341. http://dx.doi.org/10.3390/foods12020341.
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The Qinghai–Tibet Plateau is the main production area of Hippophae rhamnoides ssp. sinensis (Rha) and H. tibetana (Tib), but studies on the types and contents of soluble sugars, organic acids, free phenolics, bound phenolics, vitamin C (VC), tocopherol (VE) and carotenoids of the two sea buckthorn berries from this region have not been reported. In this paper, we found that the soluble sugars in Rha and Tib were mainly glucose and fructose; Rha exhibited a higher content of total sugar and fructose compared to Tib. The organic acids were mainly quinic acid and malic acid; Rha exhibited a higher content of total acids and quinic acid, but lower tartaric acid and citric acid compared to Tib. Rha also possessed a higher total (free and bound) phenolic as well as total (free and bound) flavonoid content than those in Tib; twelve phenolic compounds were analyzed, among which flavonols were dominant. Catechin, isorhamnetin and quercetin were the main phenolic substances. VC and VE (γ-tocopherol (γ-VE) and δ-tocopherol (δ-VE)) were higher in Rha than Tib. The total carotenoid, lutein, β-carotene and lycopene content of Tib was remarkably higher than that in Rha. Moreover, both Rha and Tib showed good in vitro and cellular antioxidant activities, and Rha had a stronger antioxidant activity. Taken together, Rha had a higher antioxidant activity, which may be due to its higher content of phenolics, flavonoids, VC and VE.