Search Results (26)

In the context of the growing need to reduce greenhouse gas emissions and to develop sustainable solutions for the construction industry, foamed geopolymers represent a promising alternative to traditional binders and insulation materials. This study investigates the thermal properties of novel low-emission, insulating geopolymer binders made from fly ash with diatomite, chalcedonite, and wood wool aiming to assess their potential for use in thermal insulation systems in energy-efficient buildings. The stability of the foamed geopolymer structure is also assessed. Measurements of thermal conductivity, specific heat, microstructure, density, and compressive strength are presented. The findings indicate that the selected geopolymer formulations exhibit low thermal conductivity, high heat capacity and low density, making them competitive with conventional insulation materials—mainly load-bearing ones such as aerated concrete and wood wool insulation boards. Additionally, incorporating waste-derived materials reduces the production carbon footprint. The best results are represented by the composite incorporating all three additives (diatomite, chalcedonite, and wood wool), which achieved the lowest thermal conductivity (0.10154 W/m·K), relatively low density (415 kg/m³), and high specific heat (1.529 kJ/kg·K). Full article

Aggregates such as sand and gravel are the most mined resources on Earth and are the largest component in concrete. They are essential for construction but are becoming increasingly scarce. At the same time, large amounts of biomass ashes are produced in wood-fired power plants, offering potential as a partial substitute for decreasing sand resources. Due to the combustion technology of circulating fluidized bed boilers, their bottom ash offers high potential as a viable alternative to natural sand. This review examines previous research to assess the feasibility of replacing sand in concrete with bottom ash. Specific cementitious products are identified, where the substitution could realistically be performed in the concrete industry. Benefits and issues with partial substitution of bottom ash from wood combustion are discussed, and gaps in the research regarding sand replacements with bottom ash, notably the durability of the resulting concrete, are shown. Bottom ash has positive properties relevant for use in mortar and concrete, both regarding physical and chemical properties. Although limited research exists in the field, several researchers have demonstrated promising results when substituting sand for bottom ash in mortars. For lower substitution levels, little effect on the fresh and hardened properties is found. Full article

This study evaluates the carbon footprint of three bio-concrete families—wood (WBC), bamboo (BBC), and rice husk (RHBC)—and their application in wall components (as blocks and as boards). A cradle-to-grave, carbon-focused Life Cycle Assessment (LCA) was used to compare these bio-concretes to conventional masonry and industrialized light-framing solutions. Each bio-concrete family incorporated biomass volumetric fractions of 40%, 45%, and 50%, using a ternary cementitious matrix of cement, rice husk ash, and fly ash (0.45:0.25:0.30). Sensitivity analyses examined the impacts of transport distances and the parameters affecting biogenic carbon storage, such as carbon retention periods in the built environment. The carbon footprint results demonstrated a significantly low or negative balance of emissions: WBC ranged from −109 to 31 kgCO₂-eq./m³, BBC from −113 to 28 kgCO₂-eq./m³, and RHBC from 57 to 165 kgCO₂-eq./m³. The findings emphasized the importance of ensuring bio-concrete durability to maximize biogenic carbon storage and highlighted the environmental advantages of bio-concrete wall systems compared to conventional solutions. For instance, BBC boards replacing fiber cement boards in light-framing systems achieved a 62 kgCO₂-eq./m² reduction, primarily due to the production (A1–A3) and replacement (B4) stages. This research outlines the emission profiles of innovative materials with the potential to mitigate global warming through circular construction, offering a sustainable portfolio for designers, builders, and AECO professionals seeking non-conventional solutions aligned with circular economy principles. Full article

This research addresses a notable gap in understanding the synergistic effects of high carbon wood bottom ash (BA) and silica fly ash (FA) on cement hydration and concrete durability by using them as a supplementary material to reduce the amount of cement in concrete and CO₂ emissions during cement production. This study analyses the synergistic effect of FA and BA on cement hydration through X-ray diffraction (XRD), thermal analysis (TG, DTG), scanning electron microscopy (SEM), density, ultrasonic pulse velocity (UPV), compressive strength, and temperature monitoring tests. In addition, it evaluates concrete properties, including compressive strength, UPV, density, water absorption kinetics, porosity parameters, predicted resistance to freezing and thawing cycles, and results of freeze–thawing resistance. The concrete raw materials were supplemented with varying percentages of BA and FA, replacing both cement and fine aggregate at levels of 0%, 2.5%, 5%, 10% and 15%. The results indicate that a 15% substitution of BA and FA delays cement hydration by approximately 5 h and results in only a 6% reduction in compressive strength, with the hardened cement paste showing a strength similar to a 15% replacement with FA. Concrete mixtures with 2.5% BA and 2.5% FA maintained the same maximum hydration temperature and duration as the reference mix. Furthermore, the combined use of both ashes provided adequate resistance to freeze–thaw cycles, with only a 4.7% reduction in compressive strength after 150 cycles. Other properties, such as density, UPV and water absorption, exhibited minimal changes with partial cement replacement by both ashes. This study highlights the potential benefits of using BA and FA together, offering a sustainable alternative that maintains concrete performance while using waste materials. Full article

The production of biomass fly ash has been increasing every year in Europe, reaching 5.5 million tons in 2020. Fly ash produced by burning biomass is not yet accepted in the standards as a substitute material for cement in mortar and concrete. In a first approach, the substitution limit of biomass ash is determined by comparing the mechanical strengths (among others, compressive strength), fresh state properties and hardened properties of mortars produced with fly ash with those of mortars produced with coal fly ash (EN 450-1 and ASTM C618). Masonry and rendering mortars have been designed with different substitution rates of fly ashes from wood combustion in thermal power plants. Although there is an overall decrease in performance, mortars made with biomass ash retain properties that make them suitable for use in masonry (loss of 13% compressive strength for masonry mortars with 10% substitution rate after 90 days) or rendering (loss of 20% compressive strength for rendering mortars with 10% substitution rate after 90 days). Water absorption and porosity (24.1 and 23.7% for masonry and rendering mortars, respectively) are, however, not significantly modified, which potentially contributes to good durability properties. Full article

The disposal of high volumes of organic waste is a global issue. Using organic waste instead of sand as an aggregate material for concrete could reduce the strain on waste treatment processes and on the extraction of finite resources. At the same time, it could be a climate change mitigation strategy, by storing the biogenic carbon contained in the organic waste. This project investigated the viability of replacing 10% of fine aggregate in concrete with various organic waste materials, namely rice husk ash, wood ash, corncob granules, and wheat straw. The fresh concrete’s properties were studied using the slump test, and the hardened concrete’s mechanical properties were measured using the compressive strength and flexural strength tests. In this study, 14 days of curing were considered for the mechanical tests, although the 28-day mechanical strength is more generally accepted. The mechanical performances along with a life cycle assessment (LCA) comparison between the concrete with organic waste and traditional concrete were conducted. The results suggested that rice husk ash and wood ash are the most-suitable organic waste products for use as aggregate replacers considering the mechanical properties. The concrete samples incorporating wheat straw and corncob granules exhibited relatively low strength; unless advanced treatment methods are applied to enhance the concrete’s performance, the utilization of these organic wastes in concrete may be limited. The environmental impact assessment of traditional concrete shows that the main contributor to almost every impact category is the production of Portland cement. Sand production contributes only marginally to the overall impact of the concrete. In terms of life-cycle greenhouse gas (GHG) emissions, traditional concrete exhibits the lowest GWP impact per cubic meter when mechanical properties are included in the functional unit used for the comparison. Nevertheless, concrete samples with wood ash and rice husk ash partially offset their lower compressive strength with higher carbon sequestration, showing a similar GWP impact to traditional concrete. This makes them promising alternatives, especially for cases where limited compressive strengths are needed. Further investigations to improve their mechanical properties and optimize their performance are warranted. Full article

Wood waste bottom ash (WWBA) is a waste generated in power plants during the burning of forest residues to produce energy and heat. In 2019, approximately 19,800 tons of WWBA was generated only in Lithuania. WWBA is rarely recycled or reused and is mostly landfilled, which is both costly for the industry and unsustainable. This study presents a sustainable solution to replace a part of cement with WWBA at 3%, 6%, 9%, and 12% by weight. Problems are also associated with the use of this material, as WWBA could have a relatively large surface area and a high water demand. For the evaluation of the possibilities of WWBA use for cementitious materials, the calorimetry test for the cement paste as well as X-ray diffraction (XRD), thermography (TG, DTG), and porosity (MIP) for hardened cement paste with the results of physical and mechanical properties, and the freeze–thaw resistance of the concrete was measured and compared. It was found that WWBA with a large quantity of CO₂ could be used as a microfiller with weak pozzolanic properties in the manufacture of cementitious materials. As a result, concrete containing 6% WWBA used to substitute cement has higher density, compressive strength at 28 days, and ultrasonic pulse velocity values. In terms of durability, it was verified that concrete modified with 3%, 6%, 9%, and 12% WWBA had a freeze–thaw resistance level of F150. The results show that the use of WWBA to replace cement is a valuable sustainable option for the production of conventional concrete and has a positive effect on durability. Full article

Bio-based materials, such as wood bio-concrete (WBC), hold promise in reducing energy consumption and carbon footprint of the construction industry. However, the durability of these materials is not well understood and can be negatively affected by the high water absorption capacity of wood bio-aggregates. In the field of cement composites, for example, silane–siloxane-based water repellent has been used to protect such materials from natural environmental attack. Nevertheless, there is still a limited understanding of various aspects related to this type of treatment, including its performance when applied to the bio-concrete substrate. This research aimed to investigate the influence of silane–siloxane on the rheology and hydration of cementitious paste through isothermal calorimetry and thermogravimetric analysis. Additionally, the impact of silane–siloxane on the physical and mechanical properties of WBCs was examined by conducting tests at fresh state (flow table and entrained air content) and hardened state (compressive strength and capillary water absorption). The composites were produced with a volumetric fraction of 45% of wood shavings while the cement matrix consisted of a combination of cement, rice husk ash, and fly ash. Silane–siloxane was applied in three ways: as coating, incorporated as an admixture, and in a combination of both methods. The results indicated that by incorporating silane in the cementitious pastethe viscosity increased by 40% and the hydration was delayed by approximately 6 h when compared to the reference. In addition, silane improved the compressive strength of WBCs by 24% when incorporated into the mixture, expressively reduced the water sorptivity of WBCs (93%), and was more effective if used as coating. Full article

The intensive construction of all categories of roads and the very demanding maintenance of the pavement structures of existing roads due to ever-increasing traffic loads confronts us with a lack of resources and also an increase in cost for the constituent materials of asphalt mixtures. On the other hand, there is another problem: large amounts of waste material in the form of bio-ash, which is obtained by burning waste wood biomass in the production of thermal energy and/or electricity. In order to solve the environmental problem of bio-ash disposal, research was conducted on the use of waste bio-ash as a constituent material in asphalt pavements. As part of this study, the effect of asphalt concrete mix, with bio-ash as a filler, on the release of harmful substances into the environment was investigated. The possibility of using wood bio-ash (BA) as a filler in asphalt mixtures was then determined through physical and mechanical property tests. The properties of the asphalt sample’s sensitivity to the action of water (indirect tensile strength ratio—ITSR) and resistance to rutting were tested for asphalt concrete type AC 11 surf with 50% bio-ash in the filler. It was established that asphalt concrete does not release harmful substances into the environment and that the 50% share of bio-ash in the filler results in asphalt that has good resistance to water sensitivity and even greater resistance to rutting. Full article

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. Full article

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 can
easily 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. Full article

The partial replacement of cement in concrete with other building materials has come to light because of research on industrial waste and sustainable building practices. Concrete is made more affordable by using such components, and it also helps to ease disposal worries. Ash made by burning wood and other wood products is one example of such a substance. Many researchers focused on the utilization of wooden ash (WA) as a construction material. However, information is scattered, and no one can easily judge the impact of WA on concrete properties which restrict its use. Therefore, a details review is required which collect the past and current progress on WA as a construction material. relevant information. This review aims to collect all the relevant information including the general back of WA, physical and chemical aspects of WA, the impact of WA on concrete fresh properties, strength properties, and durability aspects in addition to microstructure analysis. The results indicate the WA decreased the slump and increased the setting time. Strength and durability properties improved with the substitution of WA due to pozzolanic reaction and micro-filling effects. However, the optimum dose is important. Different research recommends different optimum doses depending on source mix design etc. However, the majority of researcher suggests a 10% optimum substitution of WA. The review also concludes that, although WA has the potential to be used as a concrete ingredient but less researchers focused on WA as compared to other waste materials such as fly ash and silica fume etc. Full article

A main global challenge is finding an alternative material for cement, which is a major source of pollution to the environment because it emits greenhouse gases. Investigators play a significant role in global waste disposal by developing appropriate methods for its effective utilization. Geopolymers are one of the best options for reusing all industrial wastes containing aluminosilicate and the best alternative materials for concrete applications. Waste wood ash (WWA) is used with other waste materials in geopolymer production and is found in pulp and paper, wood-burning industrial facilities, and wood-fired plants. On the other hand, the WWA manufacturing industry necessitates the acquisition of large tracts of land in rural areas, while some industries use incinerators to burn wood waste, which contributes to air pollution, a significant environmental problem. This review paper offers a comprehensive review of the current utilization of WWA with the partial replacement with other mineral materials, such as fly ash, as a base for geopolymer concrete and mortar production. A review of the usage of waste wood ash in the construction sector is offered, and development tendencies are assessed about mechanical, durability, and microstructural characteristics. The impacts of waste wood ash as a pozzolanic base for eco-concreting usages are summarized. According to the findings, incorporating WWA into concrete is useful to sustainable progress and waste reduction as the WWA mostly behaves as a filler in filling action and moderate amounts of WWA offer a fairly higher compressive strength to concrete. A detail study on the source of WWA on concrete mineralogy and properties must be performed to fill the potential research gap. Full article

Concrete, the most consumed man-made material worldwide, has shaped the environment and the modern world. Even though concrete is a major contributor to the carbon footprint, it is indispensable for building the sustainable world of tomorrow. Researchers have been exploring ways to reduce the carbon footprint and to implement strategical waste management plans in which wastes are repurposed. Pollution has been a challenge for almost all countries, especially with the increase in the release of greenhouse gases in the atmosphere and the emissions resulting from wastes in unmanaged landfills. Additionally, the areas available for landfills have become scarce. Daily all around the world, generated are wastes such as wood ash, waste glass, used tires, construction debris, and demolition wastes. These wastes usually accumulate in landfills for years, as they are mostly nondecomposable. This research explores a solution to this twofold problem in which concrete components are replaced by wastes and by-products, which in return reduces the need for raw materials that have a significant carbon footprint and repurposes wastes as part of a circular economy. In this research, wood ash is used as a partial replacement of cement and sand, fine crushed glass and crumb rubber as partial replacements of sand, and crushed glass and recycled concrete aggregates as partial replacements of gravel. The optimum eco-friendly structural concrete mix was determined to be the combined mix consisting of 5% wood ash as a partial replacement of cement; 20% wood ash, 20% fine crushed glass, and 2% crumb rubber as partial replacements of sand; and 5% crushed glass and 50% recycled concrete aggregates as partial replacements of coarse aggregates. By mass, the recycled waste materials constituted 32% of the mix, translating into 34% of its volume. Additionally, identified were mixes that may be used for structural applications. Full article

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. Full article