Wood Fly Ash Research Articles

Quick Hardening Properties of the Cement Paste Partially Replaced by the Calcined-Milled Wood Fly Ash

Quick Hardening Properties of the Cement Paste Partially Replaced by the Calcined-Milled Wood Fly Ash

Analysis of wood fly ash as a sustainable alternative to cement replacement in concrete

Supplementary cementitious materials (SCMs) can contribute to reducing the carbon dioxide footprint of concrete. One of these SCMs is biomass fly ash (BFA), which is waste from wood production. Although different researchers have used BFA as SCM, it is fundamental to know the behaviour of concrete with local materials (including available BFAs) to reduce the environmental impact of transportation. In particular, the Biobío region produces 57% of Chilean wood, concentrated in Eucalyptus globulus and Pinus radiata production. This paper describes the behaviour of concrete mixtures with replacements of eucalyptus BFA (BFAE) or pine BFA (BFAP) at 0, 10 and 20% by weight of cement. Workability, compressive and flexural tests were performed, and the specimens were examined using scanning electron microscopy as well. The results showed that BFAE reduced the slump of fresh concrete and BFAP increased it in all cases due to their morphology. An increase in resistance at later ages was evident due to an increase in pozzolanic activity and an improvement in BFA morphology. The results indicate that BFAE and BFAP are suitable for replacing at least 10% of cement, because those mixes present similar, and even higher, compressive and flexural strengths than the control mix.

Development of Green Alkali-Activated Mortar Based on Biomass Wood Ash

Portland cement (PC) is the most commonly used binder material for producing concrete. Nonetheless, increasing concerns have been attached to its manufacture which is highly energy-intensive and generates a large quantity of greenhouse gases. Developing cement-free alkali-activated materials as eco-binders is a sustainable replacement for PC, especially the possibility to utilize industrial by-products as precursors significantly reduces the environmental burden due to waste disposal. Many investigations have been reported successfully using coal fly ash, slag, and metakaolin as precursors. However, owing to the low reactivity, studies regarding biomass wood ashes (BWA) in the field of alkali-activated materials are still limited. To produce a green cementless alkali-activated mortar material, in this study, biomass fuel by-products -biomass wood bottom ash (BWBA) at 0, 25, 50, 75, and 100% as well as biomass wood fly ash (BWFA) at 100, 75, 50, 25 and 0%- were binarily used as precursors. Sodium hydroxide (NaOH) at 10 mol/L and calcium hydroxide (Ca(OH)2)at 0 and 20% by binder mass were applied together as alkali activators. Recycled sand, substituting natural sand, was adopted as fine aggregate at an aggregate/binder ratio of 2 to reduce the consumption of non-renewable natural resources. The objective is to investigate the influence of various mix ratios of BWFA and BWBA on the produced alkali-activated mortar, and identify the effects of Ca(OH)2. Compressive and flexural strength were tested to evaluate the evolution of mechanical performance. A cradle-to-gate lifecycle assessment was conducted to analyze the environmental impacts. The results reveal that the alkali-activated mortar has less environmental impact compared to the traditional PC mortar. NaOH solution is the primary source of environmental influence and BWA only contributes to very limited impacts. When 50% BWFA and 50% BWBA are binarily used, the greatest mechanical properties are achieved. The usage of Ca(OH)2 effectively improves the mechanical strength by a maximal 350% (flexural strength) and 320% (compressive strength), but meanwhile increases environmental burdens.

Valorization of waste wood fly ash in environmentally friendly lime-based plasters with enhanced strengths for renovation purposes

Waste wood fly ash (WWFA) generated during wood chips combustion in a power plant does not have any application nowadays and is commonly disposed of or landfilled. Nevertheless, considering its composition and reactivity in the presence of calcium hydroxide, it is one of the promising materials that could be used as an active admixture for modification and partial replacement of lime in lime plasters. This solution seems to be a suitable step to both improve the properties of the traditional lime plaster and reduce carbon dioxide emissions. Therefore, this comprehensive study describes a wide range of properties of lime plaster with WWFA (up to 50 wt% lime replacement) as an active admixture. Compositions of studied plasters were firstly analyzed with the help of XRD, DSC, and SEM, and then the effect of WWFA on the physical, mechanical, hygric, and thermal properties was investigated. The obtained results showed that the application of WWFA led to lower total porosity, highly improved mechanical properties, higher thermal conductivity, and lower water transport capability, which could be attributed to its pozzolanic activity. The performed experiments fundamentally broadened the existing insufficient knowledge about the utilization of WWFA for lime-based plasters improvement. All tested lime-based plasters (with 10, 20, 30 and 50% lime replacement by WWFA) have a high potential for common use in practice, especially in the historical buildings renovation. The originality of this paper lies, among others, in using a specific type of fly ash (originating from waste wood, not coal) and in testing a wider range of characteristics and properties of designed lime-based plasters with WWFA with respect to their changes over time, which enables prediction of plasters' durability.

Mechanical Properties and Lifecycle Assessment of a Green Alkali-Activated Mortar Based on Biomass Wood Ash

Abstract Portland cement (PC) is the most commonly used binder material for producing concrete. Nonetheless, increasing concerns have been attached to its manufacture which is highly energy-intensive and generates a large quantity of greenhouse gases. Developing alkali-activated materials as eco-binders is a sustainable replacement for PC and many investigations have been reported successfully utilizing industrial wastes as precursors. However, owing to the low reactivity, studies regarding biomass wood ashes (BWA) are still limited. To produce a green cementless alkali-activated mortar material, in this study, biomass fuel by-products – biomass wood bottom ash and biomass wood fly ash – were binarily used as precursors. Sodium hydroxide NaOH at 10 mol/L and calcium hydroxide Ca(OH)2 at 20 % by binder mass were applied as alkali activators. Recycled sand, substituting natural sand, was adopted as fine aggregate with an aggregate/binder ratio of 2 to reduce the consumption of non-renewable natural resources. Compressive and flexural strength were tested to evaluate the mechanical performance. A cradle-to-gate lifecycle assessment was conducted to analyse the environmental impacts. The results reveal that the alkali-activated mortar has less environmental impact compared to the traditional PC mortar. NaOH solution is the primary source of environmental influence and BWA only contributes to very limited impacts. The usage of Ca(OH)2 effectively improves the mechanical strength and compared to NaOH, it leads to decreased energy demand, requires fewer preparation steps and is less dangerous for operation.

Accelerated carbonation of alkali-activated blended blast furnace slag and wood fly ash: Carbon capture kinetics, chemical and mechanical evolutions

The influence of fly ash/slag ratio, alkaline activator silica modulus (Ms), and curing method have been evaluated on the carbonation of biomass fly ash and blast furnace slag blends. In addition to quantifying the CO2 sequestration capacity, the influence of carbonation on the chemical and mechanical properties of materials was explored to assess their durability. Results show that higher fly ash contents lead to higher CO2 diffusion, while slag limits carbonation to the surface of specimens. A higher fly ash content induces higher carbonation at Ms= 0 (as high as 0.36 mmol/g), while the most significant adsorption at a high slag content is obtained at Ms= 1.32 (as high as 0.33 mmol/g). Carbon capture and storage values as high as the pressure decay chamber recorded 0.36 mmol/g, while TGA shows the adsorption capacity of the binder as high as 3.69 mmol/g. Mechanical strength variation is proved to be a function of Ca/Si and is evaluated accordingly.

Thermal insulation enhancement of rammed earth using wood fly ash and calcium bentonite

This study evaluates the effect of chemical additives such as cement, wood fly ash, and calcium bentonite on the mechanical and thermal insulation of rammed earth (RE) material in vernacular buildings with low carbon footprint. Compacted and cured hollow RE samples were used for measuring the decrement factor, time lag, and peak temperature as part of the material's thermal properties. The results show the greatest improvement in UCS = 9.35 MPa was obtained by adding 10 % cement and 5 % fly ash after 28 days of curing. The most extended time lag was measured at 10 % cement, 10 % fly ash and 15 % Ca-bentonite (114.28 min), 10 % cement, 5 % fly ash and 15 % Ca-bentonite (73.67 min), and 5 % cement, 5 % fly ash, and 15 % Ca-bentonite (130.35 min) in hot environment with ideal humidity, hot and humid environment, and cold climate, respectively. On the other hand, the lowest decrement factor was found after 5 % cement, 10 % fly ash, and 15 % Ca-bentonite incorporation in a hot environment with ideal humidity (0.7239), 5 % cement and 5 % fly ash incorporation in a hot and humid environment (0.7778), and 5 % cement, 5 % fly ash, and 15 % Ca-bentonite incorporation in a cold climate (0.6874). The optimum mixture varied depending on the applications, such as required strength and climatic effects.

Partially burnt wood fly ash characterization and its application in low-carbon mortar and concrete

The global shutdown of coal industries has led to a shortage of coal fly ash, a commonly used cement replacement. Wood fly ash (WFA), a byproduct abundant in Canada's timber-based construction industry, emerges as a potential alternative. This study comprehensively characterized a locally available partially-burnt WFA to assess its potential to be incorporated into mortar and concrete. The study was divided into three phases: characterization of the WFA, properties of WFA-based mortar, and concrete. Preliminary findings indicate WFA's similarity to class C fly ash. While WFA adversely impacted mechanical properties, at 15% replacement, mortar and concrete performed similarly to the reference mixtures. The compressive strength of mortar and concrete reduced by 6 and 21%, respectively, slump reduced by 6.7% and chloride resistance in fact improved by 19% at 15% WFA replacement. Considering these results, WFA-based concrete presents a viable option for low-carbon construction.

Aging resistance under short time ultraviolet (UV) radiations of polymer wood composites entirely based on wastes

The paper studies the UV exposure influence on the mechanical properties, crystalline, interface and morphology of the optimised (previously water immersed) composites with wastes of rubber, PET, HDPE, wood and inorganic filler (CaO and fly ash). The mechanical strength, photo-degradation, crystalline structure and surface morphologies changes of the composites are evaluated after their exposure under simulated UV light and compared to unexposed ones. Experimental results showed UV exposure lead to the increase of Young moduli, compressive strength and tensile for high content PET samples. Significant mechanical strength even after water immersion and UV exposure were recorded for the rubber–PET–HDPE–wood–fly ash with a compression strength of about 70 MPa and for the 40 wt% PET composites with Young moduli of about 15 MPa. Therefore short term UV treatment could be used to enhance de composite’interface strength aiming at their outdoor applications.

Wood Ash as Sustainable Alternative Raw Material for the Production of Concrete—A Review

Different ecological binders have been used to minimize the negative effects of cement production and use on the environment. Wood ash is one of these alternative binders, and there has been increasing research related to this topic recently. The wood ash utilized in the literature primarily originates from power plants and local bakeries, and predominantly wood fly ash is used. This review paper examines the use of wood ash as an ecological binder in two different applications: as a cement replacement and as an alkali-activated material. Studies have shown that while increased wood ash content in concrete and mortars can have negative effects on strength and durability, it is still a promising and developable material. Depending on the chemical composition of the wood ash, the strength and durability properties of concrete might be slightly improved by utilizing wood ash as a replacement for cement, with an optimal replacement level of 10-20%. However, there is a need for more research regarding the effects of wood ash on the durability of cement-based materials and its use in alkali-activated materials. Overall, this review provides a comprehensive overview of the properties of wood ash and its potential applications in conventional concrete and mortars, as well as in alkali-activated materials.

Effects of treated biomass wood fly ash as a partial substitute for fly ash in a geopolymer mortar system

The use of biomass for energy production is becoming increasingly common. However, one of the significant problems when using biomass is the ash produced in the incineration process. Existing studies have shown the possibility of using residual biomass ashes in cement-treated materials, but its low properties have reduced compressive and flexural strength. Accordingly, some treatment methods research has also been done to enhance the properties of biomass waste materials for incorporation into the concrete matrix. On the other hand, there is a growing interest in replacing conventional ordinary Portland cement with geopolymer composite as the binder matrix in concrete due to increasing global environmental issues like greenhouse gas emissions. Therefore, this study investigates the effect of the treatment process on the physical and mechanical performance of geopolymer mortar incorporating Biomass Wood Fly Ash (BWFA) and Fly Ash (FA) for industrial applications. BWFA was treated through calcination and ball milling techniques. Both non-treated and treated BWFA were used to replace FA at different replacement ratios: 0 %, 10 %, 30 %, and 50 % by total binder weight. Test specimens were evaluated regarding porosity, compressive strength, flexural strength, X-ray diffraction analysis, thermogravimetric analysis, and microstructure development at ages 1, 3, and 7 days. The outcomes demonstrated considerable improvements in treated mortars' physical and mechanical characteristics. The inclusion of treated BWFA enhanced compressive and flexural strength. Besides, the Control mix and treated BWFA specimens performed better porosity while non-treated BWFA specimens showed better thermogravimetric performance.

Alkaline industrial wastes – Characteristics, environmental risks, and potential for mine waste management

The large quantities of alkaline industrial wastes that are generated globally have the potential to be valorized in various applications instead of being landfilled. This study evaluated the potential reuse of green liquor dregs (GLD), wood ashes, coal ash, red mud, mussel, scallop, and oyster shells to control acid and metalliferous drainage (AMD). Low hydraulic conductivities (10−7 to 10−9 m/min) suggest that covers constructed from fine-grained GLD, red mud, coal ash and wood fly ash can limit the formation of AMD. Static and kinetic test leachates of pH 5.8 to 10.6 indicate that the tested materials can neutralize acidic drainage and immobilize metal(loid)s by precipitation. The alkalinity is proportional to the amount and reactivity of carbonate and hydroxide fractions with red mud followed by coal ash being the most alkaline over 100 weeks and wood ashes the least. The tested industrial wastes generate leachates with a low metal(loid) risk when screened against the Australian freshwater guidelines. However, oxyanions including Al, Cr, Cu, Se, and V were leached in deleterious concentrations ≤100 times more than the guidelines because of their mobility in alkaline conditions. The outcomes of this study highlighted that alkaline industrial wastes can be potentially used in the long-term remediation of AMD as part of an environmentally sustainable and cost-effective integrated mine waste management strategy.

Long-Term Behavior of Concrete Containing Wood Biomass Fly Ash

Wood biomass is widely used in the European Union as a fuel for the production of heat and electrical energy, generating a considerable amount of ash. The disposal of ash, especially its finest fraction, requires proper engineering solutions, since these particles contain heavy metals and caneasily pollute soil, groundwater, or air. In this work, wood fly ash with a high amount of pozzolanic oxides and one with a high CaO content were used in concrete as a 15% and 30% cement replacement. Incorporation of wood ash in concrete reduced the 28-day compressive strength of concrete by up to 37%, which was attributed to the low stiffness of the wood ash particles, while the 2-year compressive strength indicated very low pozzolanic reactivity. The capillary absorption of concrete increased with the increase in the ash content, but almost no influence on the gas permeability was observed. Wood fly ash with high CaO content reduced the drying shrinkage of concrete by up to 65% after 1 year. In a mix with 30% of high CaO fly ash, swelling occurred in the first days of hydration, which was attributed to the volume expansion due to the formation of portlandite and brucite, but did not lead to cracking or a decrease in long-term compressive strength.

Valorization of agrowaste digestate via addition of wood ash, acidification, and nitrification

The valorization of low pollutant bioenergy waste streams as fertilizers is key for a more circular economy. In addition to supplementing nutrients, the wood fly ash could be used as stabilizing agent of an agrowaste digestate, to minimize the pollution of the environment. A two-stage experimental design with series of mild and severe acidifications was used to assess the impact on the availability of nitrogen, carbon, and phosphorus in the 25.26 ± 2.78 g of treated digestate. The 144-hour incubations at 20 °C and 100 rpm were done in closed chambers (i.e. 250-mL Schott Duran® bottles) with a 0.11 M sulfuric acid trap of 4.43 ± 0.12 mL. The proposed model for the interpretation of the results of the closed chamber indicated that the greatest rate of formation of ammoniacal nitrogen in the sulfuric fraction occurred during the first 48 h of incubation of the untreated PVWD (zero order kinetics: 2.31 ⋅ 10 −11 mol [H 2 SO 4 ] NH 4 + N/s). During this period, the mass transfer coefficient was 1.81 ⋅ 10 − 7 m/s , after which the equilibrium was established at 58.47 ± 20.50 mg [H 2 SO 4 ] NH 4 + N/kg digestate. Up to 14.08 ± 3.52 % of the water-soluble nitrogen was converted to nitric nitrogen in the remaining 96 h of incubation of the control. The acidification kept all the nitrogen in the form of ammonium but increased 5.97 ± 0.19 times the leachability of phosphorus. The combined treatment with wood ash and hydrochloric acid prevented both the nitrification and the increase of the share of water-soluble orthophosphate in the digestate. The high share of inert carbon in the wood fly ash was found promising to restore the soil as a natural carbon sink, upon application of the treated anaerobic digestate. Routes for the activation of ash as sorbent that would require lower doses of acid need to be investigated. • The greatest volatilization of ammonia was found in the untreated control digestate. • Closed chamber model was based on kinetic constant and mass transfer coefficient. • Regarding C and P, wood ash offered the greatest impact on the anaerobic digestate. • Wood ash acidification maintained ammoniacal nitrogen and low nutrient availability. • The addition of wood ash increased the N, C and P contents of the anaerobic digestate.

Sidestream materials show potential as top-dressed soil improvers for peatland forests.

The effects of top-dressing of several industrial and farming sidestream materials on the growth of downy birch (Betula pubescens Ehrh.) and Scots pine (Pinus sylvestris L.) seedlings in natural sphagnum peat soil were evaluated. Wood fly ash, industrial filter cake waste, mine tailings sand (quartz feldspar from lithium orebody), and digestate and liquid reject of cow manure from a biogas plant were studied for their physical and chemical properties, as well as for their effects as soil ameliorants on seedling growth during one growing period in a greenhouse. Each material was top-dressed on unfertilised peat in pots in quantities that corresponded to the amounts of ash used in Finnish peatland forest fertilisation (2-6tha-1). During growing, the pH of percolate water from the growing pots was below 4, and in the treatments with filter cake even below 3. However, no clear impairment of seedling growth due to acidity was observed. In all treatments, birch and pine seedlings grew at least as well as in the unfertilised peat (control treatment). Growth was strongest in the peat top-dressed with additives originating from cow manure, in which the high N and P contents promoted growth so much that foliar N was found to be diluted with respect to a high P content in the birch seedlings. No harmful concentrations of heavy metal residues were observed from the materials used. Overall, the results suggest that all the used sidestream materials show potential as soil improvers on forested peatlands.

Evaluation of Strength Properties of Sand Stabilized with Wood Fly Ash (WFA) and Cement

The article describes the laboratory evaluation of mixtures of sand modified with wood fly ash (WFA) and additionally stabilized with different amounts of cement. Laboratory research includes determining the California Bearing Ratio (CBR), compressive and indirect tensile strengths of the mixtures, and the resistance of mixtures to freezing/thawing cycles. The aim of the research is to determine if WFA, an alternative material, can improve sand bearing capacity and contribute to strength development while reducing necessary cement amounts and satisfying the technical regulation for use in pavement base courses. The test results obtained show that WFA has a considerable stabilization effect on the sand mixture and improves its load bearing capacity. By adding a small quantity of the cement, the hydraulic reaction in the stabilized mixture is more intense and results in greater strengths and an improved resistance to freezing. The test results show that, by replacement of part of the sand with WFA (in the quantity of 30%), greater strengths can be achieved in relation to the mixture of only sand and cement. Additionally, the content of cement necessary for the stabilization of sand (usually 8–12%) is considerably reduced, which enables cost savings in the construction of pavement structures.

Environmental performance of different end-of-life alternatives of wood fly ash by a consequential perspective

The increasing demand for bioenergy has intensified the pressure to utilise forest residues. Consequently, wood ash production has increased, which has prompted the need to find environmentally friendly alternatives for its end-of-life processes. However, studies assessing the environmental impacts of wood ash valorisation have assumed a static market while disregarding the potential environmental consequences and economic causalities of producing new products from wood ash. Therefore, this study assesses the outcomes of changing the conventional end-of-life of wood fly ash from its disposal in sanitary landfills to valorisation alternatives through its incorporation in construction materials (mortar and concrete) or soil amelioration. First, a consequential life cycle assessment was applied to identify the most environmentally sustainable choices for two types of wood fly ash (namely, those derived grate furnaces and fluidised bed furnaces). The characterisation factors used in this study are those that have been suggested for conducting a Product Environmental Footprint (PEF). The results show that mortar production is the best alternative for fly ashes generated in grate furnaces. Meanwhile, concrete and mortar production are the best alternatives for fly ashes generated in fluidised bed furnaces, concrete production has a slight advantage (smaller than 1%) over mortar production. Valorisation is less beneficial for soil amelioration than the incorporation in construction materials, and the impacts are higher than those of ash landfilling in some impact categories (human toxicity, freshwater eutrophication and ecotoxicity) due to the emission of trace elements into soil. A sensitivity analysis was carried out by changing the market trend of the conventional materials displaced from stable to strongly declining. This analysis showed that market trends could affect the net environmental performance of the investigated alternatives and modify their rankings.

Evaluating the Performance of Wood Fly Ash and Polymer as an Environmentally Friendly Remediation Technique for Wildfire Impacted Forest Soils

Evaluating the Performance of Wood Fly Ash and Polymer as an Environmentally Friendly Remediation Technique for Wildfire Impacted Forest Soils

Influence of Wood Fly Ash on Concrete Properties through Filling Effect Mechanism.

This paper presents the results of an experimental study aimed at determining the influence of wood fly ash (WFA) from three Croatian power plants on the properties of concrete. First, the chemical and physical properties of WFA’s were determined. It was found that these properties are highly influenced by combustion technology, the type and parts of wood used as fuel, and the local operating conditions. Subsequently, workability, heat of hydration, stiffness development, 28-day compressive strength, apparent porosity, and capillary absorption were determined on concrete mixes prepared with WFA as cement replacement from 5–45% by weight. Cement replacement up to 15% with the finest WFA accelerated hydration, stiffness development, and increased compressive strength of concrete up to 18%, while replacement with coarser WFA’s led to a decrease in compressive strength of up to 5% and had more gradual heat liberation. The dominant effect that could explain these findings is attributed to the filler and filling effect mechanisms. At the same time replacement content of up to 45% had very little effect on capillary absorption and could give concrete with sufficiently high compressive strength to be suitable for construction purposes.

Construction Of Economical Pavement Structures With Wood Ash

Stabilized mixes that are used in pavement structures are composed of aggregate bound with hydraulic binders (cement, lime) or bitumen. The most commonly used for the construction of base layers are mixes stabilized with cement. A long-standing construction practice for pavement structures was based on the use of quality granular materials for the construction of base layers. However, when designing the pavement structure and selecting materials, economy, sustainability, and environmental impact, in addition to their mechanical properties, should also be considered. Clear requirements and guidelines for sustainable development have imposed the need to explore the possibility of using non-standard materials in construction. Wood ash, which is formed as a residue from the combustion of biomass in the production of electricity and heat, is one of the newer and, in Croatia, less researched alternative materials that can be applied in construction. The paper describes compressive strength tests of mixtures of sand from the Drava River and cyclone wood ash stabilized with various contents of cement. The obtained results showed that with wood fly ash (in a content of 30 % mass.) in the stabilization mixture of sand, values of compressive strengths can be achieved within the required limits necessary for the construction of base layers of the pavement structure stabilized by a hydraulic binder.