Rice Husk Ash Content Research Articles

Experimental determination of the mechanical and hydrolytic properties of chitosan/rice husk ash composite membranes

Chitosan-based membranes are promising alternatives to synthetic membranes in a number of specialized use cases, including water purification and electrochemical devices. In application, excessive swelling when hydrated can lead to poor mechanical integrity, necessitating modifications to the polymer to counter this effect. Embedding inorganic fillers within an organic polymer matrix is one method of combining excellent mechanical stability with good performance. This study investigated the effect of rice husk ash (RHA) on the mechanical and hydrolytic properties of chitosan-based composite membranes. We incorporated varying amounts of RHA into a chitosan solution and prepared thin film membranes via solution casting. We performed structural, chemical, and mechanical characterizations on the ash and membranes, observing 82.84 % water uptake in the 1.5 wt% (wt%) RHA-doped membrane and 13.93 MPa tensile strength in the 2.0 wt% loaded composite. As the RHA content increased, the swelling ratio of the composites with RHA loadings greater than 1.0 wt% decreased, indicating an enhancement in mechanical strength. The observed results demonstrate that combining improved mechanical strength with increased water absorption and reduced swelling can lead to optimal membrane characteristics.

Combine the use of rice husk ash and quarry waste for sustainable masonry blocks: mechanical characteristics, durability and eco-benefits

The construction industry faces a growing demand for eco-friendly practices. This study explores the viability of incorporating quarry waste and rice husk ash (RHA) as partial replacements for cement and river sand in masonry block production. The research investigates the combined effect of these waste materials on the critical characteristics of cement blocks, including physical properties, mechanical behaviour, and resistance to environmental degradation. A cost-benefit analysis also considers economic, environmental, and societal factors. Replacing river sand with quarry waste in the mortar mix resulted in higher density and improved impact resistance. Also, it exhibited lower water absorption and early-age strength than the river sand. Partial cement replacement with RHA yielded positive results at lower incorporation levels. Up to 20% RHA content enhanced compressive and flexural strength while reducing embodied energy and CO₂ emissions. However, higher RHA replacements negatively affected these properties. The optimal balance between cost-effectiveness, environmental benefits, and structural performance was achieved with a combination of 20% RHA and complete quarry waste replacement. This approach offers a sustainable and potentially cost-saving alternative for conventional masonry block production. This research demonstrates the potential of utilizing waste materials in construction while promoting eco-friendly practices and responsible waste management in the industry.

Study on improving the performance of engineered cement-based composites by modifying binder system and polyethylene fiber/matrix interface

In this study, cement, rice husk ash (RHA), silica fume, mineral powder and fly ash were used as multi-component cementing materials, and the polyethylene (PE) fiber was modified by cellulose nanocrystal (CNC) to develop an Engineered Cementitious Composites (ECC) with high ductility and strength. The hydration heat and X-ray diffractometer (XRD) results indicate that RHA delays the early hydration of cement, its pozzolanic effect refines the internal porosity of hydration matrix and improves the compactness of ECC samples. Moreover, RHA increases the interfacial properties between fiber and cement matrix, reduces the first cracking strength and significantly improves the tensile strain rate of ECC. With the increasing content of RHA, its reinforcement effect becomes more obviously. The strain rate of ECC samples that uses RHA to replace 40 % of cement can reach 6.81 %. However, once the content of RHA is too high, the quality of cement involved in hydration will be significantly weakened, which reduces the amount of hydration products and has a negative impact on the compressive strength. By CNC coating, the active groups can be coated to the fiber surface to improve the fiber’s wettability. Which has promoted the growth of hydration products on the fiber surface, enhancing the fiber/matrix interface properties, and improved the ductility of ECC. CNC coating can also make up for the loss of compressive strength caused by RHA. The molecular dynamics simulation results show that unmodified PE fiber hardly to form a stable bond with C-S-H. However, CNC can adsorb with C-S-H through hydrogen and Ca-O bonding, and can also interaction with PE fiber by hydrogen bonding. Herein, CNC acts as an intermediate to connect PE and C-S-H, increase the interface stability of fiber/cement matrix, improve the interface bonding, and thus enhance the ductility of ECC. Developing multi-binder system and reinforced fiber/interface can significantly reduce the amount of cement used in ECC, and understanding the enhancement mechanism is beneficial to guide the optimal design of ECC.

Study on the interaction between limestone filler and rice husk ash on the rheological properties of cement composite pastes

As an active supplementary cementitious material, rice husk ash (RHA) can improve several properties of cement paste. However, it has a significant negative impact on the flowability of cement pastes. This study aims to improve the rheological properties of cement-RHA paste by adding an additional admixture: limestone filler (LF). The rheological curve was measured using a rheometer, and the effects of LF and RHA on the rheological properties (dynamic and static yield stresses, consistency, and structural build-up) were investigated. The calculation and analysis of water film thickness (WFT) and the interaction forces between the particles in the paste were conducted to reveal the intrinsic mechanism. The results show that LF can effectively eliminate the adverse effect of RHA on rheological properties. When the RHA content is 10 %, the addition of 5 %, 10 %, and 20 % LF reduces the yield stress by 43.86 %, 69.64 %, and 87.11 %, respectively, and decreases the consistency by 28.17 %, 40.85 %, and 73.24 %, respectively. The high porosity of RHA leads to significant water absorption, which affects the WFT between paste particles much more than LF. The WFT decreases with RHA, resulting in a higher yield stress. The higher specific surface area (SSA) of RHA reduces the spacing between paste particles, and the enhanced interactions between particles significantly increase the initial yield stress (20 min). The addition of LF reduces the inter-particle forces and the structural build-up, lowering the yield stress, which results in a good complementary effect between LF and RHA on the rheological properties. This study can provide guidance for the design of mix proportions considering the workability of the cement-LF-RHA composite system.

A sustainable approach to enhance biodegradability of recycled LDPE with starch biofillers derived from potato peels and rice husk ash*

ABSTRACT This study investigates the potential of using starch derived from potato peels and rice husks as biofiller for the production of biodegradable plastics. Starch was extracted from potato peels and modified using phthalic anhydride, formamide and potassium acetate to ensure its homogeneous dispersion into the low-density polyethylene (LDPE) matrix. The modified potato peel starch and rice husk ash were characterised using various techniques such as SEM, TEM, FTIR, XRD and were blended with recycled LDPE to enhance its biodegradability for making it an applicable environmental friendly packaging material. The quantity of the biofiller was varied from 4 to 12 g while rice husk ash content was kept constant (0.6 g). The addition of the biofiller reduced the tensile strength, tear strength and transparency of the film with an increase in haze %, weight loss both in garden soil and vegetable waste environment indicating the enhancement in biodegradability of the produced blend. Considering the applicability constrain biodegradable blend containing 20% starch was considered as the best one having tensile strength of approximately 10.42 MPa, tear strength 69.4 N, weight loss percentage of 13.29% in garden soil and 11.34% in vegetable waste when studied for a period of 360 days. Modification of starch has however increased both the mechanical (tensile strength – 12.628 MPa, tear strength – 80.47 N) and biodegradability (weight loss percentage of 15.19% in garden soil and 14.45% in vegetable waste) of the films when studied under the same conditions for the sample containing 30% starch in the matrix.

An Assessment of the Impact of Locally Recycled Cementitious Replacement Materials on the Strength of the Ultra-High-Performance Concrete

Withstanding extreme events is increasingly a significant challenge for the construction industry. Where civil infrastructures remain using traditional concrete, which has low tensile strength, poor durability, and weak crack resistance, in this regard, ultra-high-performance concrete (UHPC), with its outstanding mechanical properties and high strength, offers the prospect of wide application. This advanced technology allows for the fabrication of thin and light-dimensional structures to accelerate construction while increasing corrosion resistance to minimize maintenance intervention and extend the service life of the infrastructures. Despite this, UHPC is less eco-friendly due to consuming more cement than the usual material, which requires replacement materials, such as silica fume (SF) and rice husk ash (RHA), which are readily available from other local material production. This study proposes an experimental approach to assess the influence of SF and RHA content on the properties of UHPC. Different SF and RHA compositions will be adjusted to analyze their effects on slump flow, compressive strength, flexural strength, tensile strength, and the stress–strain relationship in UHPC tension testing. Based on the results, the most effective ratio is RHA replacing 50% of the SF in the UHPC mixture. Specialized tensile experiments reveal enhanced tensile strength with judicious RHA incorporation at 5-day and 28-day stages, particularly in initial crack and damage conditions. Stress–strain curves for 5% to 15% RHA samples show increased ductility, indicating that optimal RHA-SF ratios enhance UHPC cracking characteristics. Based on the results, a discussion on the appropriate proportions for utilizing most local materials will be derived, especially for regions of Vietnam. It is evaluated as a feasible and promising solution to reduce greenhouse gas emissions threatening global climate change.

Mechanical properties of rice husk ash and glass powder concrete: Experimental and mesoscopic studies

Using glass powder and rice husk ash as supplementary cementitious materials (SCM) can effectively reduce cement usage, protect the environment, and promote waste recycling. In this study, ordinary concrete, glass powder concrete, and glass powder rice husk ash concrete were studied through a series of experiments, including tests for slump and water absorption, uniaxial compression, variable angle shear, cyclic compression, and numerical simulation. The following results were identified. Glass powder increases the slump of concrete and reduces its water absorption, whereas the opposite is the case with the addition of rice husk ash. The uniaxial compressive strength of glass powder concrete is higher than that of ordinary concrete at 28 days of curing. Glass powder concrete has the maximum bearing capacity, in terms of the shear test. The minimum damage index is shown under cyclic compression. When the rice husk ash content is 15 %, the combination with glass powder has the strongest pozzolanic effect, while the replacement rates of 30 % and 45 % are not suitable for pozzolanic materials. The dissipation energy conversion rate of the sample containing rice husk ash is always greater than the elastic strain energy conversion rate. In addition, the samples containing rice husk ash showed ductile failure and reduced cracks during compression. This study can provide new insights into the combination of glass powder and rice husk ash as SCM.

Enhancement effect of calcium carbide residue and rice husk ash on soft soil: Small-strain property and micro mechanism

The resource utilization of calcium carbide residue (CCR) and rice husk ash (RHA) is helpful to save resources and alleviate environmental pollution. In this research, CCR and RHA were used to modify soft clay, and the resonant column test was conducted to explore its small-strain dynamic characteristics. The micro-mechanism of CCR-RHA modified soft clay (CRSC) was investigated by using scanning electron microscopy, X-ray diffraction and mercury intrusion tests. The findings demonstrated that the dynamic shear modulus of the CRSC increased with the increase of RHA content and confining pressure, but decreased with the increase of shear strain. In contrast, the damping ratio presents the opposite change law. The Hardin-Drnevich (H-D) model was used to fit the dynamic shear modulus/maximum dynamic shear modulus (G/Gmax)-shear strain γ and the damping ratio D-shear strain γ. As confining pressure increased, Gmax increased but Dmax dropped in CRSC specimens with the same RHA content. The changes of the fitted G/Gmax-γ curve could be divided into progressively decrease stage and rapid decrease stage, while the changes of the fitted D-γ curve could be separated into linear stage and slow stage, with the same turning point γ = 10−4. Microscopic tests revealed that the incorporation of CCR and RHA helped to promote the hydration reaction, and the generated hydration products such as calcium silicate hydrate were able to enhance the integrity and compactness of the CRSC. The results of this research putfward solid foundation for the application of CCR-RHA in the modification of soft soil.

Optimizing mechanical performance and flow characteristics of alkaline fly ash/rice husk ash composite backfill: Insights from multi-factor analysis and engineering optimization

In order to effectively dispose of agricultural waste rice husk ash and improve the mechanical properties of backfill, the properties of fly ash/rice husk ash composite backfill material were studied in the laboratory. The effects of fly ash, rice husk ash, straw fiber and NaOH content on the properties of composite backfilling materials were studied, and the ratio parameters of composite backfilling materials were optimized based on engineering examples. Our findings reveal that fly ash content significantly impacts slump, with its addition enhancing the flow performance of composite backfilling materials. Conversely, straw fiber, rice husk ash, and NaOH content were found to have non-significant effects on slump. We observed that with the increase of fly ash content from 5 % to 20 %, the compressive strength of the backfill firstly increases and then decreases, and the optimal content range is about 10 %. Moreover, increased rice husk ash and NaOH content effectively enhance the UCS. However, higher fly ash and straw fiber content were found to impede the strengthening effect of NaOH on UCS. Nevertheless, higher NaOH content was observed to augment the strengthening effect of rice husk ash content. Furthermore, when the content of fly ash and rice husk ash is 5∼10 % and 3–12 % respectively, rice husk ash and fly ash effectively reduce the size range of internal void structures, enhancing the microstructure density and mechanical properties of the composite backfilling material. Based on engineering example, we determined the optimal ratio parameters of the composite backfilling material to be: 20 % fly ash content, 9 % rice husk ash content, 0.4 % straw fiber content, and 2.5 % NaOH content. This study is helpful to promote the application of waste rice husk ash and straw fiber in mine filling, and provides theoretical guidance for the parameter design of backfilling materials.

Effect of rice husk ash and coconut coir fiber on cement mortar: Enhancing sustainability and efficiency in buildings

This research investigated energy efficiency, insulation properties together with strength properties and cost-effectiveness, focusing on developing a sustainable mortar. Cement: sand of 1: 2.25 (by weight) mortar with varying rice husk ash (RHA) and coconut coir (CC) fiber contents were prepared. Physical, microstructure, strength, durability, and thermal performances were experimentally examined. Life cycle assessment and cost analysis were numerically examined. Adding CC fiber reduced the longer final setting time found with the RHA-based mortar. With 20 % RHA and 0.5 % CC fiber, weight was reduced by 9.2 % (compared to the conventional mortar), promising a lightweight mortar. Flexural strength was increased by 8.6 % with 0.5 % CC fiber addition, this was further increased to 13.6 % with 10 % RHA in the mixture. 20 % RHA and 0.5 % CC fiber mortar exhibits a temperature difference of 8.7°C, whereas the conventional mortar exhibits a temperature difference of 2.5°C, indicating a reduced thermal conductivity of the RHA-CC fiber mortar. This mortar reduced the CO2 emission, energy consumption, and manufacturing cost by 17.7 %, 13.6 % and 7.0 %, respectively, indicating the sustainability. A cost-effective and energy-efficient lightweight mortar with enhanced thermal insulation and flexural strength was achieved by reinforcing the conventional mortar with 20 % RHA and 0.5 % CC fiber for the applications of dwellings.

A Comprehensive Analysis of the Influence of Rice Husk Ash Content on Concrete Strength

A Comprehensive Analysis of the Influence of Rice Husk Ash Content on Concrete Strength

Research on the effect of different content of rice husk ash on the microstructure of concrete

Mercury injection porosimetry test is used to study the microstructure of rice husk ash cement paste with different content. The influence of rice husk ash on the microstructure of cement paste is analyzed through porosity, pore size distribution, the most probable pore size, pore size gradation and critical pore size analysis. The results show that with the increase of rice husk ash content, the porosity of cement paste decreases, and the pore size distribution and the most probable pore size decrease, which indicates that the addition of rice husk ash can improve the pore structure of concrete and improve the durability of concrete. With the increase of rice husk ash content, the number of harmful holes of cement paste decreases, the number of harmless holes increases, and the critical pore diameter decreases, which indicates that the addition of rice husk ash can improve the strength and impermeability of concrete.

The Utilisation of Rice Husk Ash Leachates for The Synthesis of Eco-Friendly Geopolymers

Geopolymers are inorganic polymers projected as feasible alternatives to Portland cement due to their lower CO2 emissions and high mechanical properties. In recent times, however, their impact on other environmental indices such as abiotic depletion, freshwater toxicity, marine ecotoxicity, terrestrial ecotoxicity, acidification, and human toxicity has become questionable, thus the need to investigate alternative eco-friendly precursors and activators. This work aims to manufacture an eco-efficient geopolymer by utilising biomass ash leachate as an alternative to the conventional alkali silicate solution. The leachate was obtained by soaking the rice husk ash (RHA) in a 10 M concentration of NaOH solution and filtering to obtain a clear solution. The effects of the calcination temperature of the kaolin and the RHA content in the alkaline solution were investigated, and a factorial design of experiments was developed considering three levels of calcination temperature (700°C, 800°C, and 900°C) and five levels of RHA content (0 g, 5 g, 10 g, 15 g, and 20 g). Physical and mechanical tests were performed on the synthesised geopolymer pastes, and chemical analysis was performed using X-ray diffraction and X-ray spectroscopy. The impacts of replacing the synthetic alkali silicates with rice husk ash-based activators were compared. The results showed that the calcination temperature of the kaolin and the content of the RHA both contributed significantly to the flexural and compressive strength at the 0.01 level of significance. A compressive strength of 10.4 MPa was obtained for the MK915 binders, which showed a 100% increase from samples without RHA content. This research proves that utilising RHA-based activators in metakaolin-based geopolymers can be feasible for less critical applications where a very high compressive strength will not be required.Keywords: alkaline activators, biomass, geopolymers, leachates, rice husk ash

Investigation of machine learning models in predicting compressive strength for ultra-high-performance geopolymer concrete: A comparative study

Ultra-high-performance geopolymer concrete (UHPGC) is a new category of traditional UHPC developed to meet the desire for ultra-high-strength and green building materials. In the current study, random forest (RF), support vector regression (SVR), and extreme gradient boosting (XGB) are used to forecast the compressive strength (CS) of UHPGC. Firstly, the findings of the 113 CS tests available in the previous studies were extracted. Twelve feature variables, including GGBS, silica fume, fly ash, and rice husk ash contents as precursors, the Na2SiO3, NaOH, KOH, and extra water content, polypropylene fiber, steel fiber, liquid-to-binder (L/B) ratio, and curing temperature, were investigated. After analyzing the extracted data, it was found that there were more mixtures of steel fiber-based UHPGCs and synthetic fibers compared to mixtures without fibers. This may reduce the accuracy and comprehensiveness of the predictive models used. To address this issue, several experiments were designed, performed, and tested. Overall, the dataset of 128 CS results was used to develop the machine learning (ML) models. The findings validate the effectiveness of the RF, SVR, and XGB models in accurately predicting the strength of the UHPGC, as constructed by their excellent predictive accuracy (R2 > 0.84). The XGB model performance is superior to the RF and SVR models. The feature importance analysis determined that the steel fiber content and L/B ratio were the top two elements that might profoundly impact the CS. Additionally, NaOH and silica fume also have a positive correlation with CS. Conversely, the extra water and percentage of GGBS exhibit a low correlation with the CS. Through the application of ML models, this study not only ascertains the significance of algorithms including RF, SVR, and XGB in precisely forecasting the CS of UHPGC, but also reveals essential understandings regarding the importance of steel fiber content, L/B ratio, and various other pivotal variables, consequently facilitating the development of refined formulations and improved functionalities in eco-friendly construction materials.

Effects of silica fume and rice husk ash contents on engineering properties and high-temperature resistance of slag-based prepacked geopolymers

Geopolymer slurries can be favored to achieve a sustainable approach in prepacked aggregate concretes. This study presented here investigated experimentally the effect of silica fume (SF) and rice husk ash (RHA) on the high-temperature resistance of slag-based sustainable prepacked geopolymers. In the production of prepacked aggregate geopolymers (PAGs), ground granulated blast furnace slag (GGBFS) was utilized as the main aluminosilicate-rich precursor material, and SF and RHA were replaced with GGBFS in various contents including 7.5 % and 15 %. The physical, mechanical, and microstructural properties of specimens cured at 35 °C and 70 °C for 8 h were determined comparatively. Residual compressive strength and mass loss of mixtures exposed to elevated temperatures (150 °C, 300 °C, and 600 °C) were determined to observe high-temperature effects. The results revealed that the properties of PAGs were affected considerably by curing temperature and precursor type. The maximum oven-dry density of 2244 kg/m3 with RHA content of 7.5 % was obtained at 70 °C curing temperature. Specimens produced with RHA tended to absorb more water under both heat curing conditions and the highest water absorption of 10.2 % with RHA content of 7.5 % was obtained at 35 °C curing temperature. The compressive strength of PAGs varied between 13.7 and 28.10 MPa, and flexural strengths varied between 1.48 and 2.74 MPa. Increasing curing temperature improved the strength properties of PAGs, and in general, the 8-h compressive and flexural strength values of SF samples were relatively higher. The application of elevated temperature to the PAG mixtures caused a significant reduction in both compressive strength and mass loss. Among the specimens cured at 35 °C, the specimens with RHA showed relatively better high-temperature performance in terms of compressive strength, while the specimens with SF cured at 70 °C showed better performance. PAG specimens produced with RHA showed the best high-temperature performance against mass loss. According to the results obtained in the given study, these recycled wastes could be used to improve the physico-mechanical properties and high-temperature performance of slag-based PAGs.

Microstructure, mechanical, and wear properties evaluation of Al-Cu based composite using RHA as reinforcement

ABSTRACT This study utilised a two-step stir-cast technique to fabricate Aluminium-based composites reinforced with 5% wt Copper (Cu) and varying weight percentages (1–4% wt) of Rice husk ash (RHA). Our work investigated the role of RHA reinforcement on the microstructure, mechanical properties, and wear characteristics of AlCuRHA composite. Characterisation of the composites and fracture surfaces was performed utilising SEM. The hardness and tensile properties were evaluated. Wear was conducted on the composites in dry and wet conditions using H2SO4 as the medium. The microstructure revealed the homogeneous distribution of the RHA within the AlCu matrix. The hardness of reinforced AlCu is enhanced from 54.24 Hv to 122.74 Hv with an increment of RHA reinforcement from 0 to 4%. The Ultimate tensile (UTS) and specific strengths were noted to increase with increased RHA content from 1 to 4% wt. The ductility levels were reduced with the increase in RHA content. The RHA-reinforced AlCu composite exhibits mixed ductile and brittle fracture modes. The composites with RHA exhibited greater wear resistance. Compared to the dry condition, the composites exhibited improved wear resistance in the acidic environment. The composite with 4 wt% RHA exhibited the lowest wear rates regardless of the environment.

Compressive strength of waste-derived cementitious composites using machine learning

Abstract Marble cement (MC) is a new binding material for concrete, and the strength assessment of the resulting materials is the subject of this investigation. MC was tested in combination with rice husk ash (RHA) and fly ash (FA) to uncover its full potential. Machine learning (ML) algorithms can help with the formulation of better MC-based concrete. ML models that could predict the compressive strength (CS) of MC-based concrete that contained FA and RHA were built. Gene expression programming (GEP) and multi-expression programming (MEP) were used to build these models. Additionally, models were evaluated by calculating R 2 values, carrying out statistical tests, creating Taylor’s diagram, and comparing theoretical and experimental readings. When comparing the MEP and GEP models, MEP yielded a slightly better-fitted model and better prediction performance (R 2 = 0.96, mean absolute error = 0.646, root mean square error = 0.900, and Nash–Sutcliffe efficiency = 0.960). According to the sensitivity analysis, the prediction of CS was most affected by curing age and MC content, then by FA and RHA contents. Incorporating waste materials such as marble powder, RHA, and FA into building materials can help reduce environmental impacts and encourage sustainable development.

Response Surface Optimization of Rice and Guinea Corn Husk Ash Blended Concrete

Concrete, a fundamental construction material, consists of aggregates, water, cement, and additives. Unfortunately, the large-scale production of cement is a major contributor to carbon dioxide (CO2) emissions, primarily from the manufacturing process and the consumption of fossil fuels. This not only incurs environmental costs associated with global warming but also depletes vital limestone deposits. To mitigate these issues, this study aims to explore the optimal utilization of Guinea Corn Husk Ash (GCHA) and Rice Husk Ash (RHA) in concrete. This research investigated the chemical properties of GCHA and RHA, and their impact on the compressive and split-tensile strengths of concrete when integrated in various proportions. The study reveals that both GCHA and RHA meet the minimum oxide content requirement of 70% set by ASTM C618, with silicon dioxide (SiO2) as the predominant oxide. Increasing the content of RHA and GCHA from 5% to 10% improves the concrete's compressive and split-tensile strengths after curing for 56 days. Optimization results indicate that the ideal mix consists of 10% GCHA, 8.5% RHA, and 82.5% cement, yielding a compressive and split tensile strength of 31.34 N/mm² and 3.07 N/mm² respectively. This study thus offers a promising solution for sustainable concrete production by reducing the environmental footprint of cement while enhancing material properties and promoting an eco-friendlier approach to construction. Keywords: Concrete, Guinea Corn Husk Ash, Rice Husk Ash, Compressive Strength, Split-Tensile Strength

Analysis of Pore Structure of Rice Husk Ash Concrete Under Freeze-Thaw Cycling

A microscopic experimental study was conducted on the rice husk ash cement paste under freeze-thaw cycles using mercury intrusion porosimetry. The study mainly focused on the influence of rice husk ash on the pore structure of the cement paste through analyses of porosity, pore size distribution, most probable pore size, pore size gradation, and critical pore size under freeze-thaw cycles. The results showed that with an increase in the rice husk ash content under the same freeze-thaw cycles, the porosity of the cement paste decreased, and both the pore size distribution and the most probable pore size decreased. This indicates that the addition of rice husk ash improves the pore structure of the concrete and enhances its frost resistance. Furthermore, as the rice husk ash content increased, the number of harmful and deleterious pores in the cement paste decreased, and the critical pore size decreased, demonstrating the improved durability performance of the concrete with the addition of rice husk ash.

Enhancing the physical properties of cemented ultrafine tailings backfill (CUTB) with fiber and rice husk ash: Performance, mechanisms, and optimization

A series of experiments was conducted to study the performance and mechanisms of Cemented Ultrafine Tailings Backfill (CUTB). Firstly, the optimum fiber type was selected by single factor multilevel test. Secondly, the effects of cement content, rice husk ash content, fiber content and fiber length on backfill properties were analyzed by orthogonal test and microstructure test, and the influence mechanism of fiber and rice husk ash content was revealed. Finally, fuzzy mathematics theory is used to optimize the ratio parameters. The results show, compared to glass and basalt fiber, polypropylene fiber yields the most substantial enhancement in backfill strength. The increase of cement content, polypropylene fiber content and length can reduce slump, but the change of rice husk ash content has no obvious effect. Increased cement or fiber content effectively restrained the formation of primary fractures in CUTB, thus enhancing its integrity. Adding an optimal dosage range of 0–4 % of rice husk ash boosted the early compressive strength, albeiting at the expense of later compressive strength. Fiber addition with the optimum content range between 0.1 and 0.4 % enhanced the strengthening effect of cement content on compressive strength. Fiber primarily enhances the macroscopic strength of backfill through the dispersion and co-loading of forces, whereas rice husk ash enhances strength by optimizing void structure distribution. The optimal ratio parameters of a cement content of 310 kg/m³, rice husk ash content of 8.0 %, fiber content of 0.4 %, and fiber length of 9 mm were proposed finally.