With the increasing utilization of underground space, engineering muck has become a potential urban risk. This study employed a waste-to-waste strategy to promote its low-carbon recycling by using rice husk ash (RHA) as a stabilizer, with a focus on elucidating the stabilization mechanisms through multi-scale analysis. The results showed that RHA synergized with cement, enhancing unconfined compressive strength and water stability, while reducing the specific surface area and swelling potential of the engineering muck. The optimal RHA dosage was found to be between 4 % and 6 %, with cement content ranging from 3 % to 9 %. The multi-scale analysis demonstrated that the stabilization mechanisms of RHA-cement stabilized soil were governed by two main factors: structural enhancement and surface modification, both of which were driven by the promotion of novel hydration products through the incorporation of RHA. Specifically, the needle-like and columnar minerals effectively filled soil pores, forming a dense, robust skeletal structure that enhanced the mechanical properties of the stabilized soil. Meanwhile, the honeycomb-like C-S-H gel adhered to soil particle surfaces, repairing cracks and reinforcing interparticle bonding, thus improving the overall structural integrity. AFM analysis further revealed that the honeycomb-like C-S-H gel consisted of rod-like nanoparticles that were regularly arranged on the soil surface. This feature increased surface roughness, reduced fractal dimensions, and created a multi-scale structure of micro-papillae and nano-hairs with a lotus leaf effect, significantly enhancing the hydrophobic properties of the soil.

This study investigates the effect of 3-aminopropyltriethoxysilane (APTES) concentration on the surface modification of rice husk (RH) for developing polybutylene adipate-co-terephthalate (PBAT) composites with varying filler loadings (30-50 wt%). Silane-treated RH was incorporated into PBAT via melt blending to enhance mechanical and thermal properties. The novelty lies in systematically correlating APTES concentration with RH loading, offering insights into their synergistic impact on composite microstructure and overall performance. Our approach provides a comprehensive understanding of how controlled silane treatment improved interfacial adhesion, mechanical strength, thermal stability, and maintained biodegradability. Characterization was performed using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), tensile testing, thermogravimetric analysis (TGA), water absorption, and soil burial tests. SEM revealed a more homogeneous morphology with fewer voids. The 70PBAT/30Silane RH-2% composite achieved the best mechanical performance, outperforming 4% and 6% silane-treated composites, with tensile strength improvements of 7% and 10%, and Young's modulus increases of 12% and 4%, respectively. Tensile properties indicated that for a filler loading of 30 wt%, a 2% silane concentration is sufficient, while a maximum of 6% is required for 40 wt%, and a minimum of 4% is necessary for 50 wt% filler loading. TGA showed enhanced thermal stability with higher filler content, while soil burial tests confirmed 90% mass loss after 6 months, indicating excellent biodegradability. These results highlight the potential of silane-treated PBAT/RH composites for sustainable molded products such as trays.

This research compares the stabilization efficiency of kaolinite and montmorillonite clayey soils using two industrial and agricultural by-products, namely fly ash (FA) and rice husk ash (RHA), activated by sodium hydroxide (NaOH). To this end, various proportions of FA and RHA (i.e., 0%, 5%, 10%, 15%, and 20%), along with NaOH solutions at 2 M and 4 M concentrations, are utilized to treat both low-and high-plasticity clayey soils. The resulting geopolymers are then subjected to a wide range of mechanical and micro-structural tests, including standard compaction, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), swelling potential, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Results show that incorporating both FA and RHA into kaolinite and montmorillonite clays up to their respective optimal contents significantly enhances all their mechanical properties. However, FA-based geopolymers exhibit superior mechanical properties compared to RHA-based ones under similar additive contents and curing conditions. Accordingly, the optimal FA content is found to be 15%, while for the RHA-based geopolymers, the peak UCS is observed at 15% and 10% RHA for kaolinite and 10% and 5% RHA for montmorillonite when treated with 2 M and 4 M NaOH solutions, respectively. The results also suggest that FA is more effective than RHA in controlling the swelling potential of both kaolinite and montmorillonite soils. Microstructural analyses further corroborate the findings of macro-scale experiments by showcasing the comparative occurrence of geopolymerization, as well as the formation of cementitious gels, and synthesis of new chemical products.

This study investigated the conversion of cellulose from rice husk (RH) and straw (RS), two types of agricultural waste, into Carboxymethyl cellulose (CMC). Cellulose was extracted using KOH and NaOH, hydrolyzed, and bleached to increase purity and fineness. The cellulose synthesis yielded a higher net CMC content for RH-CMC (84.8%) than for RS-CMC (57.7%). Due to smaller particle sizes, RH-CMC exhibited lower NaCl content (0.77%) and higher purity. FT-IR analysis confirmed similar functional groups to commercial CMC, while XRD analysis presented a more amorphous structure and a higher degree of carboxymethylation. A biodegradable film preparation of starch-based CMC using citric acid as a crosslinking agent shows food packaging properties. The biodegradable film demonstrated good swelling, water solubility, and moisture content, with desirable mechanical properties, maximum load (6.54 N), tensile strength (670.52 kN/m2), elongation at break (13.3%), and elastic modulus (2679 kN/m2), indicating durability and flexibility. The RH-CMC film showed better chemical and mechanical properties and complete biodegradability in soil within ten days. Applying the biodegradable film for tomato preservation showed that wrapping with the film reduced weight loss more efficiently than dip coating. The additional highlight of the work was a consumer survey in Thailand that revealed low awareness but significant interest in switching to alternative uses, indicating commercial potential for eco-friendly packaging choices and market opportunities for sustainable materials.

This study addresses the challenges of adobe in Peru, a material widely used in rural areas but with limitations in mechanical strength and durability, particularly in seismic and humid regions. To bridge this gap, a combination of sugarcane bagasse fiber (SBF) and rice husk (RH) was added at percentages of 0.5%, 1%, and 1.5% (by dry soil weight), and the experimental adobe walls were reinforced with galvanized metal mesh. At 28 days, mechanical properties were evaluated through cube compression, prism compression, and diagonal wall compression tests, while durability was assessed at 56 days using wetting-drying wear and suction tests. The findings showed that adding 1% SBF + 0.5% RH to the adobe mixture increased compressive strength by up to 30.8%, and reinforcing this mixture with metal mesh further enhanced the strength by 26.4% at 28 days. Additionally, a 37.12% improvement in wetting-drying wear resistance and a 26% reduction in suction were observed at 56 days. This sustainable solution meets local regulatory standards and is particularly beneficial for seismic and humid regions, offering a practical alternative for safer and more resilient adobe housing in vulnerable areas of Peru and beyond, adaptable to on-site conditions. The results demonstrate a strong synergy between these agricultural byproducts and the galvanized metal mesh in enhancing adobe performance.

This study presents a novel approach to address the current issue of plastic waste in the biosphere, which poses ecological hazards and threatens living beings. Herein, a set of biodegradable composites has been developed through the melt blending of polybutylene adipate-co-terephthalate (PBAT) and rice husk (RH), aiming to discover effective surface modification techniques for enhancing mechanical properties while maintaining biodegradability above 90%. This research studied the diverse surface treatment methodologies applied to raw RH, including alkaline, acetylation, and silane treatments. The novelty of this study lies in its focus on evaluating how these treatments distinctly influence the mechanical properties and biodegradability of RH. Additionally, it seeks to understand the underlying mechanisms driving these performance changes. To further improve the compatibility between hydrophobic PBAT and hydrophilic RH, a compatibilizer such as maleic anhydride (MAH) was added. A range of analytical techniques, including scanning electron microscopy (SEM), tensile testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), contact angle measurement, and soil burial test, was employed to investigate the biodegradability of the composites. The results indicate that the PBAT/Silane RH/MAH composite exhibited exceptional mechanical properties, with a tensile strength of 22.49 MPa, a strain at break of 41.83%, and Young's modulus of 187.60 MPa. Furthermore, the composites developed exhibited 90% mass loss during a six-month soil burial test, confirming their remarkable biodegradability. The findings present an innovative and practical solution for utilizing RH waste in a wide range of applications, particularly in the production of molded products such as straws.

This study examines the use of low-value rice husk ash as a stabilizer to optimize the mechanical performance and strength of compressed earth blocks made with local soil from the Cauquenes Province, Chile. The use of locally sourced earth construction materials in Chile is limited by their lower compressive strength compared to conventional fired bricks, along with the demanding seismic conditions of the region. To address these limitations, this study details the methodology for collecting, preparing, and mixing raw materials to manufacture compressed earth blocks, compacted under 10 MPa using a novel cylindrical polylactic acid mold designed for miniaturized samples. Fourteen different samples representing nine mixtures of rice husk ash and soil were evaluated using an optimized experimental design. The resulting mechanical properties, including fracture analysis correlated with performance, were assessed through statistical analysis to determine the significance of the optimum mix and the observed trends in strength, modulus of elasticity, yield strength, and associated plastic work. The maximum compressive strength achieved was 3.3 MPa. Notably, the optimum mix of rice husk ash-stabilized compressed earth blocks exhibited a 60% increase in strength compared to pure soil compressed earth blocks, demonstrating the potential of rice husk ash as a cement substitute.

Black cotton soil's notable swelling and shrinkage contribute to structural damage. This study examines the impact of nano rice husk ash (nRHA) variants on this soil: One synthesized in 60 h and another through 7 h combined dry-wet milling method. The primary objective is to assess the effects of nRHA treatment on the soil's index properties, engineering characteristics and swelling behavior. Laboratory tests including free swell index, Atterberg's limits, swelling potential, swelling pressure, unconfined compressive strength and consolidation tests were conducted on black cotton soil samples treated with both nRHA variants. Results indicated that the 7-h nRHA treatment led to lower plasticity and reduced swelling compared to the 60-h variant. Specifically, the 7-h treated soil showed decreased swelling pressure, compression index and rate of primary swelling, along with increased pre-consolidation pressure and unconfined compressive strength. The free swell index also decreased by 21% with the 7-h nRHA treatment. The superior performance of the 7-h milled nRHA is likely due to its higher calcium and reactive silica content, enhancing its stabilizing effect. This research highlights the 7-h nRHA as a more effective stabilizer for black cotton soil, offering a promising solution to mitigate its problematic volumetric behavior.

Two common waste by-products in Thailand, rice husk ash (RHA) and coir fiber (CF), were used alongside lime (L) to stabilize laterite soil and create a sustainable subbase material for pavements. The mechanical properties of the laterite soil mixed with RHA, lime, and CF were evaluated through compaction characteristics, unconfined compressive strength (UCS), California bearing ratio (CBR), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analyses. The dry soil mass was replaced with 10% and 20% RHA, and CF was added at 0.5%, 1%, and 1.5%. Additionally, based on the initial consumption of lime (ICL) test, 8% lime was incorporated into the mixture. The samples were cured for 7 days (short-term) and 56 days (long-term) before undergoing various tests. In terms of compaction, results showed that increasing the content of RHA, CF, and lime led to a decrease in maximum dry unit weight and an increase in optimum moisture content. The 10RHA8L and 20RHA8L mix designs demonstrated the highest UCS and CBR values after 56 and 7 days of curing, respectively. EDX analysis revealed the formation of calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H) gels on the particle surfaces, leading to a denser and more cohesive structure. Based on these findings, the mixture containing 20% RHA and 8% lime exhibited the most favorable properties for use as a subbase material in road and embankment construction.

Highway, road, and airfield construction on weak soils is costly endeavor. Re-use of agricultural waste is widely employed as a stabilizing agent to improve engineering properties of these soils. In this study, rice husk ash (RHA), a by-product of incineration of husk from rice production, was used as a potential stabilizer. The water absorption and retention rate of the stabilizer, denoted as W-ab, is determined by measuring the amount of water that is absorbed and retained by the stabilizer in relation to its initial dry mass. The study involved treatingAo clay, imitating a dredged soil with highwater content, at various addition ratios (ARHA). Diverse curing periods were applied to assess the liquid limits (w(L)), plastic limits (w(P)), and cone index (q(c)) of the treated clays. Compaction characteristics were also determined for several ARHA and different curing periods. The test results show an increase in both w(L) and w(P) with decrease in plastic index (I-p) with increase in ARHA, but no remarkable change in w(L) and w(P) associated with curing. Compaction characteristics show a decline in rho(dmax) and increase in wopt with increase in ARHA, but no notable changes in rho(dmax) and wopt with cured samples. Increase in q(c) with ARHA, but no noteworthy change in q(c) with curing was discerned through cone index test. The trends for curing observed in the above test results were consistent with that observed for W-ab. The results were then modified based on the W-ab of stabilizer. The measured water content (w) and liquidity index (IL) were modified to account for absorbed water (w*), which gave a better correlation with q(c) than w. The compaction characteristics were also modified based on Wab, ARHA and the results suggest that treated clays were able to achieve modified dry density (rho(dmax)*) at the same values of modified water content (w(opt)*).