Mixed Ash Research Articles

Utilization of Portland Cement and Fly Ash for Treatment of Mercury Polluted Soil through Stabilization/Solidification

Abstract Traditional gold mining contributes significantly to soil mercury pollution. Stabilization/Solidification (S/S) Technology offers a remediation solution for soils contaminated with heavy metals. Besides the low cost of the technology, the S/S technology can be carried out in situ and ex-situ with material pozzolanic properties, such as Portland cement and fly ash, effectively bind these metals. This study aims to identify the proportion of mercury-contaminated soil mixed with a combination of Portland cement and fly ash. Artificial soil samples with a mercury content of 150 mg/kg were used, and test specimens were formed into 5 cm cubes. In the first phase, different ratios of Portland cement to fly ash were tested: 100:0, 90:10, 80:20, 70:30, 60:40, and 50:50. The second phase focused on the optimal mix ratio based on compressive strength tests for combinations of Portland cement and fly ash with mercury-contaminated soil, with the same ratios as in the first phase. Subsequent compressive strength and specimens were tested using the Toxicity Characteristic Leaching Procedure (TCLP). The first phase identified the optimal 50:50 ratio of Portland cement to fly ash, achieving a compressive strength of 5559 tons/m2. In the second phase, the same 80:20 ratio for the mix of Portland cement, fly ash, and mercury-contaminated soil yielded a compressive strength of 2902 tons/m2 and a TCLP result of 0.0062 mg/L. All samples met the criteria set by the United States Environmental Protection Agency (US EPA), with variations ranging from 17 MPa for residential concrete to 28 MPa and the TCLP-B quality standard. According to Regulation by Government No. 22 of 2021, the permissible concentration is 0.05 mg/L. The study concludes that increasing the proportion of soil and fly ash Included in the mixture reduces the quality of S/S products.

A Study on Development in Engineering Properties of Dense Grade Bituminous Mixes with Coal Ash by Using Natural Fiber

Coal-based thermal power plants in India produce significant waste, primarily fly ash and bottom ash, which poses environmental and health risks when disposed of in large quantities. This research explores the effective use of these waste products in bituminous paving mixes, substituting natural aggregates to conserve resources. Dense-graded bituminous macadam (DBM) specimens were prepared using natural coarse aggregates, bottom ash as fine aggregate, and fly ash as filler, with sisal fiber as a reinforcing additive. Varying percentages (0–1%) and lengths (5–20 mm) of SS1 emulsion- coated sisal fiber were tested to optimize the mix’s engineering properties. VG30 bitumen, chosen for its superior Marshall characteristics, resulted in an optimum binder content of 5.57%, fiber content of 0.5%, and fiber length of 10 mm, achieving a Marshall stability of 15 kN. Additional performance tests, including moisture susceptibility, indirect tensile strength (ITS), creep, and tensile strength ratio assessments, confirmed that the coal ash and sisal fiber mix significantly enhances pavement durability. This approach offers an eco-friendly and economical solution for bituminous pavement construction, addressing coal ash disposal challenges and conserving natural aggregates. Keywords: Bottom ash, Fly ash, Sisal fiber, Emulsion, Indirect tensile strength, Static creep test, Tensile strength ratio.

Application of Phytoremediation to Hydraulic Binders Alkaline Inclusion in Forest Roads Pavement Construction

The use of hydraulic binder materials for the improvement of pavement subgrade has many implications for the surrounding ecosystem due to the possible leakage of alkaline compounds. The objective of this study is to evaluate the capacity of plants to remedy the subgrade affected by alkaline inclusion. To reduce the impact and return the subgrade to its original state, a phytoremediation process is studied. The impact of two materials commonly used for the subgrade improvement is analysed – fluid ash (slag) and lime+cement mixture. Three different mixes of plants – Mix A, Mix B and the native natural vegetation Mix N – are proposed. Totally 99 samples were collected and 990 specimens were chemically and geotechnically analysed and statistically evaluated. The success of phytoremediation process for both Mix A and Mix B can be observed. It is considerably higher for the undersurface alkaline inclusion than for the surface one. Mix B appears to be the best for fluid ash binder and Mix A for lime+cement mixture binder. It is worth noting that the native natural vegetation in Mix N also contributes to the phytoremediation process and that the appropriate plant selection – e.g. Mix A and Mix B – can accelerate this process.

Study on the effect of cinder ash as an auxiliary additive mineral in hydrated lime treatment for expansive sub-grade soil in road construction

Expansive soils pose significant challenges to road construction globally due to their tendency to expand and contract with changes in moisture content, leading to pavement failure. In the construction industry, finding an economical and cost-effective alternative to conventional road construction materials is crucial. The use of a natural cinder ash and hydrated lime mixture as reinforcement has proven to be effective in addressing this issue. Cinder ash, a readily available waste material in countries like Ethiopia, is adaptable and water-resistant, making it an ideal choice for reinforcing expansive soil. This article investigates the strength performance of a cinder ash and hydrated lime mixture as a reinforcement material for expansive soil. The study involves mixing 0%, 20%, 25%, 30%, and 35% of cinder ash with soil stabilized with 2–5% hydrated lime. Expansive soil samples are prepared according to the ASSHTO & ASTM method and tested for compressive strength, California bearing ratio, bulk density, and water absorption. The findings reveal a 448.62%, and 374% increase in compressive strength and California Bearing Ratio respectively for the specimen containing 5% hydrated lime and 35% cinder ash, cured for 28 days. The water absorption is minimized at 15.23% for the 5% hydrated lime and 35% cinder ash mixture; while the maximum density of the soil is observed at 1.774 kg/m3 for the optimal combination of 5% hydrated lime and 35% cinder ash mix. The study suggests that using 5% hydrated lime and 35% cinder ash content for the stabilization of expansive soil significantly enhances the strength characteristics of compressed stabilized soil.

Incorporation of Nanoalumina in Potassium Feldspar-based Phosphoric Acid Activated Geopolymer Composites: A Sustainable Approach

This study investigates the potential of potassium feldspar-phosphate-based geopolymer concrete as a sustainable replacement to traditional concrete, addressing the environmental concerns associated with CO2 emissions during cement production. While geopolymer concrete offers a promising path towards sustainability, its performance often falls short of Portland cement concrete. This study investigates the use of nanoalumina in improving the performance of geopolymer concrete. A ternary mix was formulated with potassium feldspar powder, metakaolin and rice husk ash, incorporating varying percentages of nanoalumina geopolymer concrete mixes. The mechanical characteristics of the resulting geopolymer composites were assessed through compressive and split tensile strength tests. The findings revealed that a 4% nanoalumina dosage (GC-N4) yielded the most significant improvement in strength and durability. The GC-N4 mix performed superior in all metrics, demonstrating the highest compressive (41.82 MPa) and split tensile (3.7 Mpa) strengths. Reduction in water absorption and durability aspects were also optimum in GC-N4. These results highlight the potential of incorporating nanoalumina into a ternary mix of potassium feldspar powder, metakaolin and rice husk ash to significantly enhance the overall performance of geopolymer concrete, promoting its wider adoption as a sustainable construction material.

Life-Cycle Assessment and Environmental Costs of Cement-Based Materials Manufactured with Mixed Recycled Aggregate and Biomass Ash.

The development of new building elements, such as concrete and mortar with sustainable materials, which produce a lower carbon footprint, is an achievable milestone in the short term. The need to reduce the environmental impact of the production of cement-based materials is of vital importance. This work focuses on the evaluation of the life-cycle assessment, production costs, mechanical performance, and durability of three mortars and three concrete mixtures in which mixed recycled aggregates (MRAs) and biomass bottom ash from olive waste (oBBA) were included to replace cement and aggregates. Powdered MRA and oBBA were also applied as complementary cementitious materials with a reduced environmental footprint. Chemical and physical tests were performed on the materials, and mechanical performance properties, life-cycle assessment, and life-cycle cost analysis were applied to demonstrate the technical and environmental benefits of using these materials in mortar and concrete mixtures. This research showed that the application of MRA and oBBA produced a small reduction in mechanical strength but a significant benefit in terms of life-cycle population and environmental costs. The results demonstrated that finding long-term mechanical strength decreases between 2.7% and 14% for mortar mixes and between 1.7% and 10.4% for concrete mixes. Although there were small reductions in mechanical performance, the savings in environmental and monetary terms make the feasibility of manufacturing these cement-based materials feasible and interesting for both society and the business world. CO2 emissions are reduced by 25% for mortar mixes and 12% for concrete mixes with recycled materials, and it is possible to reduce the cost per cubic meter of mortar production by 20%, and the savings in the cost of production of a cubic meter of concrete is 13.8%.

Wood ash-based binders for lightweight building materials: Evaluating the influence of hydraulic lime and cement on the setting and mechanical properties of wood ash pastes

The shift from fossil fuels to bioenergy has led to increased wood ash output. Since a large proportion of this waste ends up in landfills, recycling wood ash in construction materials is one of sustainable approaches of managing this by-product. However, the amount of biomass ashes currently recycled in building materials is still limited. This study therefore explored the feasibility of valorising four different types of wood ashes in large quantities in the production of lightweight building materials. Thirty pastes with different levels (80, 90, 95 and 100 wt%) of wood ash and (0, 5, 10 and 20 wt%) of natural hydraulic lime (NHL) or ordinary Portland cement (PC) were developed. Partial replacement of wood ash (WA) by NHL or PC accelerated the setting and improved the mechanical properties of blended pastes. The initial and final setting times decreased with increasing NHL or PC content in the mixes. The strength of the pastes increased with increasing NHL or PC levels and curing time. However, wood bottom ash (WBA) mixes were controversial because their mechanical properties gradually weakened over time. For WA-NHL blends, the 28-day flexural and compressive strength ranged from 0.02 to 1.12 MPa and from 0.05 to 2.59 MPa, respectively. On the other hand, for WA-PC pastes, the flexural and compressive strengths at 28 days varied from 0.07 to 2.72 MPa and from 0.13 to 5.49 MPa, simultaneously. These results prove that wood ash can be used effectively as a main component of binding matrices for lightweight building materials.

One-part geopolymer based on micronized sediments and fly ash mix: Mechanical, microstructural and leaching assessment

This study aims to investigate the leaching behavior of one-part geopolymer based on micronized sediments and fly ash. Four mixtures optimized in terms of mechanical performance and contain 0, 15, 30 and 50 % of sediments were studied. Mixtures characterization indicated that adding sediments increases compressive strength from 19 MPa to 29 MPa and increases mesoporosity (less than 50 nm) from 1.6 % to 3.5 %, with C-A-S-H and N-A-S-H gels coexistence. Given the use of dredged sediments in mixtures, it was important to study their environmental impact. The batch leaching test (0–4 mm) was carried out to study the environmental impact of mixtures at the end of their life cycle. Next, the potential for the release of chemical elements during the life cycle of the mixtures was studied through leaching tests on monolithic samples. The findings show that geopolymerization is effective for the chemical and physical immobilization of several contaminants contained in aluminosilicate sources. The geopolymer binders synthesized proved effective for the chemical immobilization of large metallic and metalloid trace elements (MMTEs) and anions (sulfate, chloride and fluoride). However, immobilization of oxy-anions MMTEs such as arsenic occurs by physical rather than chemical trapping, due to the low porosity of geopolymers. The concentration of arsenic (As) and selenium (Se) were below the non-hazardous wastes (NHW) threshold for all aluminosilicate sources but after activation the results show that these elements are mobilized due to elevated pH. This shows an effect of alkalinity on element mobilization/immobilization. It was demonstrated that carbonation could be a solution for immobilizing arsenic at the end of the mixtures' life cycle, as it reduced its concentration for all mixtures (between 20 and 51 % depending on the mixtures). In addition to these findings, the pH assessment (less than 12.5) showed that these binders can be considered as non-hazardous materials and can be assimilated to an ordinary non-corrosive binder.

Co-melting mechanisms for municipal solid waste incineration fly ash with fine slag from coal gasification and coal gangue

Vitrification is a promising treatment for municipal solid waste incineration fly ash (MSWI-FA); however, high energy consumption due to the high MSWI-FA fusion temperature limits the development and application of this technique. In this study, fine slag ash (FSA) derived from coal gasification and coal gangue ash (CGA) were mixed with MSWI-FA to reduce the ash fusion temperature. The transformation of minerals in ash during thermal treatment was examined via X-ray diffraction and thermodynamic equilibrium calculations. The ash flow behaviour was observed using a thermal platform microscope, and the silicate structure was quantified using Raman spectra. The co-melting mechanisms for the mixed ash were systematically investigated. Results indicate that the flow temperature (FT) of the mixed ash exhibited an initial decrease and subsequent increase as a function of the addition ratio of FSA or CGA. Lowest ash FT of 1215 °C and 1223 °C were recorded for addition of 50% FSA and 50% CGA, respectively; further, these temperatures were lowered by > 285 °C and >277 °C respectively, relative to FT of the MSWI-FA. The transformation of minerals and silicate structure during mixed ash heating was responsible for the variation in the ash fusion temperature. CaO in MSWI-FA tended to react with mullite, quartz and haematite in FSA and CGA, forming minerals such as anorthite, gehlenite, and andradite with relatively low melting points. The addition of FSA or CGA caused changes in the silicate network structure of the mixed ash. In particular, 50% FSA incorporation caused the transformation of Q4 and Q3 to Q2, whereas 50% CGA introduction resulted in the conversion of Q4 and Q2 into Q3 and Q1 + Q0, respectively. The silicate network depolymerised, causing reduction in the ash fusion temperature and increasing the melting rate.

Potential of ammonium adsorption of coal fly ash-based porous geopolymer granules

Abstract Porous geopolymer materials have been recently used in environmental remediation applications as adsorbents. This study is to investigate the NH4 + adsorption capacity of geopolymer activated from coal fly ash mixing with NaOH, Na2SiO3, and H2O2. The H2O2 with various ratios (0%, 4.5%, and 8.5%) were added into the fly ash pastes as blowing agents. The NH4 + adsorption capacity of these materials was examined concerning the effects of NaOH concentration, H2O2 contents, adsorbent particle sizes, dosages, and NH4 + concentration by batch adsorption test. The results show that adding 4.5% (G45) and 8.5% (G85) of H2O2 developed porous structures in geopolymer granules and their NH4 + adsorption capacity depends on their particle sizes and pore structures. In particular, geopolymer granules with 8.5% H2O2 exhibited higher NH4 + adsorption capacity than lower content of H2O2 in case of particle size of 3.0-8.0 mm. However, pulverized geopolymer still demonstrated the greatest NH4 + adsorption capacity. In addition, both granules G45 and G85 demonstrated a well-fit (R2 = 0.97-0.99) with Langmuir and Freundlich isotherms. The maximum NH4 + adsorption capacity of G85 was 19.86 mg/g, which indicated the NH4 + adsorption potential of porous geopolymer granules generated from waste materials such as coal fly ash.

Application of Bottom Ash with Hydrated Lime in Pavement SubgradeConstruction

Introduction: A structurally strong subgrade is always desirable in pavement construction so as to provide a resilient and durable foundation for the subsequent pavement layers for adequate performance under the given traffic load/volume and environmental conditions. Emphasizing the increased awareness for effective waste recycling and demand for a sustainable construction approach, re-utilizing industrial wastes in pavement subgrade construction can be a viable option. The potential re-utilization of bottom ash (BA), an incombustible by-product generated in huge quantities from coal combustion in thermal power plants, in replacing natural soil in the subgrade construction of pavements will not only limit the extent of disturbance to ecological balance through over-utilization of natural soil but also open an avenue for the reuse of bottom ash. Method: In this study, an effort was made to study the possible use of different percentage replacement of BA (0 to 60% with an increment of 15%) with natural soil with and without hydrated lime (5% by weight of soil-bottom ash mix) for applications in road subgrade. Laboratory investigations were conducted for basic soil characteristics, compaction properties, and strength evaluation through California bearing ratio (CBR) and unconfined compressive strength (UCS) tests. Result: The addition of 5% lime to the soil-bottom ash mixes decreased the plasticity index significantly. The highest MDD and the lowest OMC were found in soil with 45% bottom ash. The CBR results of control soil increased from 6.3% to 137.7% for soil-bottom ash mix containing 45% bottom ash and 5% hydrated lime, and the same combination showed a 104% increase in UCS. Conclusion: The observed results indicated that the coupled behavior of the bottom ash and hydrated lime treatment has effectively increased the soil's compaction and mechanical strength and its suitability for use in road subgrade construction.

Performance of cementitious systems containing calcined clay in a chloride-rich environment: a review by TC-282 CCL

In this review by TC- 282 CCL, a comprehensive examination of various facets of chloride ingress in calcined clay-based concrete in aggressive chloride-rich environments is presented due to its significance in making reinforced concrete structures susceptible to chloride-induced corrosion damages. The review presents a summary of available literature focusing on materials characteristics influencing the chloride resistance of calcined clay-based concrete, such as different clay purity, kaolinite content and other clay minerals, underscoring the significance of pore refinement, pore solution composition, and chloride binding mechanisms. Further, the studies dealing with the performance at the concrete scale, with a particular emphasis on transport properties, curing methods, and mix design, are highlighted. Benchmarking calcined clay mixes with fly ash or slag-based concrete mixes that are widely used in aggressive chloride conditions instead of OPC is recommended. Such comparison could extend the usage of calcined clay as a performance-enhancing mineral admixture in the form of calcined clay or LC2 (limestone-calcined clay). The chloride diffusion coefficient in calcined clay concrete is reported to be significantly lower (about 5–10 times in most literature available so far) compared to OPC, and even lower compared to fly ash and slag-based concrete at early curing ages reported across recent literature made with different types of cements and concrete mixes. Limited studies dealing with reinforcement corrosion point out that calcined clay delays corrosion initiation and reduces corrosion rates despite the reduction in critical chloride threshold. Most of these results on corrosion performance are mainly from laboratory studies and warrant field evaluation in future. Finally, two case studies demonstrating the application of calcined clay-based concrete in real-world marine exposure conditions are discussed to showcase the promising potential of employing low-purity calcined clay-based concrete for reducing carbon footprint and improving durability performance in chloride exposure.

Effect of High Calcium and High Iron Coal on Ash Fusion Characteristics of Petroleum Coke during Cogasification.

Entrained flow gasification provides a more efficient utilization method for high-sulfur petroleum coke. The operation temperature of the entrained flow gasifier must be above the ash fusion temperature (AFT) of petroleum coke due to the liquid slag discharge. In this work, petroleum coke was blended with high-calcium coal and high-iron coal, respectively, under a reducing atmosphere, and the variations in AFTs were recorded by an ash fusion temperature analyzer. The influence of mineral transformations on the ash fusion characteristics of blended ash was analyzed by X-ray diffraction and FactSage. The results showed that both high calcium coal and high iron coal could efficiently reduce the AFTs of petroleum coke. When the ratio of high calcium coal and high iron coal reached 60 wt %, the corresponding flow temperature (FT) of mixed ash decreased to 1225 and 1312 °C, respectively. With the content of high calcium coal increasing, coulsonite (FeV2O4), vanadium trioxide (V2O3) and nickel (Ni) with high-melting points tended to decrease, causing the decrease of AFT for mixed ash. As high iron coal was added, Ni and V2O3 continuously kept decreasing. In particular, the percentage of FeV2O4 first increased and thereafter decreased with high iron coal above 40 wt %.

Durability analysis of metakaolin recycled concrete under sulphate dry and wet cycle

This study aims to enhance the durability, cost-effectiveness, and sustainability of recycled fine aggregate concrete (RFAC) subjected to the combined effects of wet-dry cycles and sulfate erosion. Dry–wet cycle tests were conducted in RFAC with different admixtures of biotite metakaolin (MK) and 15% fly ash (FA) mix (M) under 5% sulfate erosion environment. The effect of 0%, 30%, 60% and 90% recycled fine aggregate (RFA) replacement of natural fine aggregate on mass loss, cubic compressive strength, relative dynamic modulus test of RFAC, damage modeling and prediction of damage life of concrete were investigated. The results showed that the concrete cubic compressive strength and relative dynamic modulus were optimal for recycled concrete at 15% MK biotite dosing and 60% RFA substitution, and its maximum service life was accurately predicted to be about 578 cycles under 5% sulfate dry–wet cycling using Weibull function model. This study is pioneering in addressing the durability of RFAC under sulfate attack combined with wet-dry cycling, employing a novel approach of incorporating MK and FA into RFAC. The findings highlight the practical application potential for using MK and FA in RFAC to produce durable and sustainable construction materials, particularly in sulfate-exposed environments. This research addresses a critical challenge in the construction industry, providing valuable insights for developing more durable and eco-friendly construction materials and contributing to long-term sustainability goals.

Support vector machine-based prediction of unconfined compressive strength of Multi-Walled Carbon nanotube doped soil-fly ash mixes

Support vector machine-based prediction of unconfined compressive strength of Multi-Walled Carbon nanotube doped soil-fly ash mixes

Understanding adhesion induced by calcium compounds at 900 °C using model particles

In waste and biomass combustion plants, ash adheres to the inside of the combustors and surfaces of air heaters, etc., accumulating over time and causing operational problems due to the deposited ash layer. Here, we evaluated the adhesion properties of calcium-rich ash using synthetic ash. Specifically, we investigated the role of Ca-Al in ashes. The adhesion of Ca-Al synthetic ash and mixed ash of Ca-Al and SiO2, which is included in ash and utilized as a bed material in fluidized-bed combustion systems, was investigated. Adhesion was found to increase when three conditions were met: Ca/Al molar ratio >1, SiO2 coexistence, and 900 °C. The increase in tensile strength of the powder bed corresponded to shrinkages in volume, specific surface area, and total pore volume, suggesting solid phase sintering as the cause of increased adhesion. Adding alumina nanoparticles to the highly adherent sample successfully suppressed the adhesion increase.

The effect of physical properties of pond ash as a partial replacement of sand in the mortar mix

The major focus of the present study is the use of pond ash to replace fine river sand in the production of plaster. In this study, the physical, mechanical, and microstructure characteristics of mortar are investigated for different replacement levels of sand with pond ash. The results show that the dry density of pond ash mixes is reduced by increasing the replacement level, which is due to the higher water absorption and pond ash’s porousness. It is worth mentioning that at a replacement rate of 20%, compressive and flexural strengths are higher than those of control specimens. On the other hand, drying shrinkage is 31% lower than the control, but the achieved strength is more than the required strength as per the Indian code. Scanning electron microscopy with energy dispersive x-ray spectroscopy shows that a rise in silicon content (12%) for samples having a 20% replacement of pond ash has a high C–S–H gel density, thus exhibiting higher compressive and flexural strengths. X-ray diffraction results show that the lower strength of 40% pond ash replacement is due to the presence of sodium sulfate. Hence, the results indicate that fine pond ash can be partially replaced with fine river sand for internal plaster and to produce mortar and blocks.

Enhancing M30 Grade Concrete: A Comparative Study of Hooked vs. Crimped Steel Fibers in Fly Ash Mixes

The realm of concrete offers vast opportunities for inventive applications, design, and construction methodologies, given its adaptability and cost-effectiveness. Its versatility in meeting diverse requirements has established it as a highly competitive building material. To address escalating structural demands and harsh environmental factors, new cementitious materials and concrete composites are continually being developed, followed by the need for enhanced durability and performance, as well as pressure to utilize industrial waste materials. The research explores the impact of incorporating fly ash and steel fiber into M30-grade concrete, alongside cement, coarse, and fine aggregate, through experimental methods, with the primary aim of determining optimal ingredient proportions for achieving desired strength. The study evaluates compressive strength variations with fly ash ranging from [10%] to [30%] while hooked and crimped steel fibers [ranging from 0% to 1.5%] in concrete, alongside cement, fine and coarse aggregate. Environmental considerations and the imperative to utilize industrial waste have significantly contributed to advancements in concrete technology and sustainability. Through meticulous analysis of results, meaningful inferences are made in relation to the strength attributes of fly ash fiber-reinforced concrete. Two sets of experiments were conducted, one altering fly ash content while maintaining fixed steel fiber content, and the other varying steel fiber content while keeping other parameters constant. The study aims to provide practical insights for engineers seeking cost-effective and sustainable building construction methods, adhering to specified norms (IS Code: 456-2000).

Wildfire Ashes from the Wildland-Urban Interface Alter Vibrio vulnificus Growth and Gene Expression.

Climate change-induced stressors are contributing to the emergence of infectious diseases, including those caused by marine bacterial pathogens such as Vibrio spp. These stressors alter Vibrio temporal and geographical distribution, resulting in increased spread, exposure, and infection rates, thus facilitating greater Vibrio-human interactions. Concurrently, wildfires are increasing in size, severity, frequency, and spread in the built environment due to climate change, resulting in the emission of contaminants of emerging concern. This study aimed to understand the potential effects of urban interface wildfire ashes on Vibrio vulnificus (V. vulnificus) growth and gene expression using transcriptomic approaches. V. vulnificus was exposed to structural and vegetation ashes and analyzed to identify differentially expressed genes using the HTSeq-DESeq2 strategy. Exposure to wildfire ash altered V. vulnificus growth and gene expression, depending on the trace metal composition of the ash. The high Fe content of the vegetation ash enhanced bacterial growth, while the high Cu, As, and Cr content of the structural ash suppressed growth. Additionally, the overall pattern of upregulated genes and pathways suggests increased virulence potential due to the selection of metal- and antibiotic-resistant strains. Therefore, mixed fire ashes transported and deposited into coastal zones may lead to the selection of environmental reservoirs of Vibrio strains with enhanced antibiotic resistance profiles, increasing public health risk.

Increasing Unconfined Compressive Strength of Soft Clay Stabilized with Coir Fiber and Bagasse Ash Mix

Increasing coir fiber and bagasse ash waste can cause environmental degradation. Utilization of this waste in construction work is still rarely done. Coir fiber is a natural material with the highest coefficient of friction and tensile strength. Bagasse ash has a high silica content and is suitable for use as pozzolan. Soil stabilization with a combination of both is expected to improve the geotechnical properties of soft soil. This research aims to analyze the unconfined compressive strength (UCS) and secant modulus of soft clay stabilized with coir fiber-bagasse ash mix. Coir fiber as much as 0.75% and ash with varying contents: 0%, 2%, 4%, 6%, 8%, and 10% of the total weight of the mixture. The specimens were cured for 28 days. UCS tests were conducted according to ASTM D2166-16 with the axial stress and strain relationship curve results to determine the UCS and secant modulus. The results showed that the UCS value and secant modulus value increased along with increasing bagasse ash content. The maximum value was achieved at 8% ash variation with a UCS value of 472.45 kPa (an increase of 382% from a soil-coir fiber mix) and a secant modulus value of 21.94 MPa (an increase of 571% from a mixture of soil and coir fiber). The research results show that this mixed soil is classified as hard soil, which can withstand high loads. It is hoped that the results of this research can become a reference for stabilizing soft soil in the field.