Next Article in Journal
Mechanism of Unfrozen Water Content Evolution during Melting of Cryogenic Frozen Coal Body Based on 2D NMR
Previous Article in Journal
Aerostat-Based Observation of Space Objects in the Stratosphere
 
 
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Ecological Wood Protection System against Fire, Fungi and Insect Damage Using Humic Acids and Fly Ash

1
Chair of Rural Building and Water Management, Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, 51006 Tartu, Estonia
2
Chair of Physical Chemistry, Institute of Chemistry, University of Tartu, 50411 Tartu, Estonia
3
Chair of Colloid and Environmental Chemistry, Institute of Chemistry, University of Tartu, 50411 Tartu, Estonia
4
Chair of Soil Science, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, 51006 Tartu, Estonia
*
Author to whom correspondence should be addressed.
Appl. Sci. 2024, 14(12), 5179; https://doi.org/10.3390/app14125179
Submission received: 9 April 2024 / Revised: 23 May 2024 / Accepted: 12 June 2024 / Published: 14 June 2024
(This article belongs to the Topic Advances in Sustainable Materials and Products)

Abstract

:
Traditional wood protection methods involving fire retardants and preservative paints have limitations, requiring periodic renewal during a building’s lifecycle and generating hazardous waste post-use. This study aims to achieve a multifaceted solution, simultaneously enhancing wood’s resistance to fire, fungi, and insects using natural and/or recycled mineral waste components containing lime that react with pozzolanic additives. Additionally, organic humates provide protection against pests (fungi and insects). Following the crystallization processes within the wood’s structure, it exhibits increased resistance to fire, as demonstrated by tests involving seven species. The study also describes wood tolerance tests against termites (Reticulitermes flavipes) that yielded promising results, indicating that the treated wood is an unsuitable habitat for these pests. An additional advantage for the timber industry is that the crystallized composite filling the wood’s pores minimizes wood stitching and reduces internal stresses during the drying process. This property enhances the utility of timber in frame structures and carpentry joints, which are less susceptible to moisture-induced movements. The timber impregnated by our method can also be repurposed or disposed of as non-hazardous waste. This research thus offers an eco-friendly and effective approach to wood protection.

1. Introduction

Timber, a material with a rich history in construction dating back to early human societies, offers a multitude of advantages including its widespread availability, affordability, aesthetic appeal, ease of processing, low thermal conductivity, robust mechanical properties, acoustic insulation, durability, and reduced life-cycle greenhouse gas emissions when compared to counterparts such as concrete, steel, and glass [1]. To align with the objectives outlined in the Paris Agreement aimed at limiting global warming to below 2 °C by 2100, the construction industry must transition to carbon-neutral or carbon-negative practices by 2030 [2,3]. Timber exhibits a low net carbon emission (NCE), expressed in kilograms of carbon per ton (kg C/t), approximately one-fifth that of glass and one-nineth that of concrete [4]. The drive to minimize the environmental footprint of the construction sector has reignited interest in timber-based architecture. Given the longevity of buildings, integrating timber construction can establish a significant carbon sink, counterbalancing carbon emissions from construction activities with sequestration potential upon demolition [1]. Timber construction offers inherent energy efficiency, sustainability, and reduced greenhouse gas emissions, and supports sustainable forestry practices. Moreover, timber serves as a means of carbon sequestration, with wood products containing approximately 2.5 billion tons of carbon [4]. However, timber architecture presents notable challenges, particularly regarding fire safety. Throughout history, there have been instances of extensive fires resulting in the destruction of predominantly wooden cities. In addition to adhering to the International Building Code [5] and relevant national regulations, enhancing the fire resistance of construction materials is imperative. Thus, mitigating the fire hazard associated with wooden structures emerges as a primary obstacle to expanding timber’s utilization in construction [6]. During fires, timber structures experience diminished load-bearing capacity compared with non-combustible materials such as steel, accompanied by decohesion attributable to carbonization and the thermal breakdown of biopolymers including cellulose, hemicellulose, and lignin. The strength of timber begins to deteriorate at temperatures of approximately 65 °C, with lignin and hemicellulose undergoing decomposition within the range of 150 °C to 250 °C and cellulose experiencing thermal degradation above 300 °C [6].
Primary wood-feeding pests, including large wood-boring beetles (Coleoptera) and termites (Blattodea), cause significant damage. They tunnel, fragment wood, and facilitate fungal and bacterial growth through nitrogen fertilization and enzymatic digestion, often mediated by symbiotic partners. Termites, eusocial detritivorous insects, consume dead plant matter, wood, and cellulose, with some engaging in fungiculture. Classified as earth-dwelling, wood-dwelling, or arboreal, invasive species such as Reticulitermes flavipes (now found in Ontario, Canada; parts of Western, Southern, and Central Europe; as well as the Macaronesian archipelago) pose significant threats to buildings, with a global economic damage estimate of approximately USD 32 billion in 2010 [7,8].
There are different ways to harden and make wooden material more stable against pathogens, pests, and fire [9,10]. Most of the methods involved in making wood additionally fire-resistant do not use green methods, but rather toxic chemicals [9,10]. Some modern methods even use materials such as silicon carbide or graphene oxide, which have excellent efficiency, but high price [11]. Common wood preservatives, including creosote, PCP, CCA, CCB, copper, and boron compounds, are effective against biological damage but may not be suitable for finished products due to leaching or exudation issues. They are highly toxic, necessitating hazardous waste treatment for end-of-life disposal. Alternatives like azoles and quaternary ammonium salts are costly. Additionally, biocides used in wood impregnation can exacerbate harmful gas release during fires, potentially increasing fire accident lethality [12,13,14].
Flame retardants enhance fire resistance in timber and other flammable materials through several mechanisms. Fusible salts form a protective coating, restricting oxygen access; noncombustible gas release dilutes flammable gases; endothermic reactions or phase changes dissipate flames through cooling; while certain flame retardants are engineered to conduct heat away rapidly [15]. Quenching reactive free radicals inhibits flame propagation in the gas phase, halting chain reactions and preventing further combustion. Strong acids, bases, and halogen-based compounds contribute to fire retardancy, with the latter acting as gas-phase free radical scavengers [16,17]. Fireproofing through impregnation can be enhanced with ceramic coatings [18] or fire-resistant paints.
Fire-resistant paints are commonly used due to their simplicity and affordability, even post-construction. However, they offer inferior fire protection compared to impregnation methods. These paints may crack when wooden details warp, shrink, or expand due to humidity changes and can be damaged by solar UV radiation. Consequently, international building regulations since 2018 prohibit sole reliance on fire-resistant paints, mandating additional fire safety measures for full compliance. Although not yet enforced in the European Union, these regulations are active in 51 countries globally [5,19,20].
Among green methods, treatments on Picea abies involve thermal–hydromechanical (THM) densification, where low-molecular-weight resin is infused into the timber structure [21]. The relatively green THM treatment method employs water, heat, and mechanical means to enhance timber density. When combined with phenol impregnation, it leads to increased density, hardness, abrasion resistance, and certain strength properties. Set recovery, indicative of compression deformation recovery, is regarded as a crucial parameter for compressed wood [22]. Tests on Picea abies demonstrated higher set recovery values, while decreased values and increased mechanical strength were observed for poplar wood [21]. Additionally, these treatments enhanced fire resistance [23]. Previous studies have examined termite resistance to oil-heat treatment in Scots pine sapwood (Pinus sylvestris L.) and Norway spruce (Picea abies L.). Oil-heat-treated wood effectively combats damages inflicted by Formosan termites residing in subterranean environments.
Combinations of thermo-hydro techniques with vacuum treatment (at 100 mm Hg) for wood densification have proven effective in providing stability against Monochamus spp. [24]. Successful wood treatment has involved injecting phenol-based aqueous resins into timber using a vacuum system, resulting in reduced set recovery and subsequent densification of the treated wood, thereby enhancing most dimensional stability values [25].
Silica fume boosts the structural strength of wood–cement materials, displaying high pozzolanic activity [26]. Silica aerogels improve wood properties, enhancing thermal stability and fire resistance; supplementation with a silica mineralized layer further enhances these qualities [24,27]. Pine wood achieves significant fire resistance through treatment with guanylurea phosphate, effectively embedded within the wooden structure [28]. Phosphate treatment enhances tensile and flexural strengths of poplar wood, forming composite materials, and modified wheat starch treatment enhances the flame retardancy of wood fibers [29,30].
Waterglass, a soluble silicate salt with silicic acid-containing anions ((SiO4)4−, (Si2O7)6−, (Si3O9)6− (Si42)8−, (Si6O18)12−, etc.), can replace silica fume for impregnating lumber, plywood, particle board, wafer board, paper, fabric, and similar cellulosic materials as an intumescent fireproofing agent [31,32]. When exposed to heat (between 100 °C and 200 °C) and/or a polymerization-inducing agent, such as an organic or inorganic acid, waterglass undergoes polycondensation, releasing water molecules and chemically solidifying the impregnating agent. To modify lumber’s properties, a C1–8 alcohol, ketone, ether, or combination thereof can be added, enhancing lipophilicity, reducing hardness, and improving flexibility, with these compounds effectively acting as superplasticizers. These modifiers react at hydroxyl (silanol) groups, forming lipophilic-Si-OR and -Si-R sites. Moreover, the silanol groups of the polymerized silica matrix can cross-link with functional groups on the surfaces of fibrous organic materials, creating chemical bonds between cellulose fibers and the solidified silica skeleton [32,33].
An alternative to impregnation for fireproofing is coating, which can be used alone or in conjunction with impregnation. Applied to the surface of wood or other combustible materials, it serves as decoration, protects against pests and fungi, and in case of fire, delays flame spread, allowing for safer evacuation [34]. These coatings encompass fire-retardant paints and ceramic coatings [19,35].
These eco-friendly methods provide alternatives to conventional chemical treatments, lessening environmental impact while boosting wood’s fire resistance and other properties. Despite its limitations, wood remains a sustainable and eco-friendly building material, as it is renewable and replantable.
In our preceding investigation [36], it was observed that the deposition of cement crystals within peat fibers exhibited a highly effective inhibition of material ignition. Even under prolonged exposure to heat from a blowtorch, material degradation occurred without ignition. Building upon this observation, the current study focuses on the cultivation of analogous microcrystals within wood grooves utilizing oil shale ash possessing a high lime content, supplemented with pozzolanic additives (silica fume). To enhance wood durability against organic pests such as fungi, bacteria, and insects, a solution of peat humates was introduced during the impregnation process, a method previously demonstrated to be effective in safeguarding peat-derived materials. This approach yields an environmentally friendly universal wood protection system devoid of conventional highly toxic substances.
As we innovate to enhance wood’s fire safety and durability, its significance in the construction sector is poised to grow. The primary challenge lies in devising an environmentally friendly, non-toxic, and safe wood treatment approach. Previous methods have fallen short in providing comprehensive protection against various damaging factors. We propose that combining impregnation with humic solutions alongside the cultivation of cementitious microcrystals within wood fibers, as developed by our team, may offer a promising solution to address these objectives.

2. Materials and Methods

2.1. Experimental Setup

The aim of the study was to explore the possibility of protecting wood from fire and biological damage (caused by insects and fungi) using the crystallization of cementitious materials in wood veins. Presumably, such microcrystals decrease the heat transfer into the deeper layers of wood materials, and, in addition, an endothermic reaction takes place with the release of CO2, which cools the fire front and blocks the access of atmospheric oxygen. As the cementitious phases do not provide sufficient protection from rot fungi and wood-damaging insects, we added humates extracted from the peat into the impregnation solution.
The experimental setup was as follows:
(1)
Test specimens were cut from various species of wood.
(2)
The test specimens were dried at 105 °C for 48 h.
(3)
Humate solutions were prepared. Humates were extracted from black peat using ammonia solution, and a highly concentrated humate solution (exceeding 3%) was obtained.
(4)
Colloidal oil shale ash, colloidal silica, and humate were mixed, and the test specimens were placed into a mixer using special holders. The system was vacuumed to remove air veins in the wood. The air was slowly reintroduced into the system while the impregnation solution was kept moving by a mechanical mixer.
(5)
Test specimens were rinsed with water and dried.
(6)
Cuts of the test specimens were made, and SEM studies were performed to determine the quality of impregnation and the chemical composition of the crystals formed.
(7)
Another part of each test specimen was placed into a termite colony.
(8)
The third fraction of each test specimen was used in the fire-resistance tests using a cone calorimeter.
Upon completing the experimental cycle, we noted varying levels of impregnation and crystallization among different wood samples, and, in some instances, even across different sides of the same sample. This discrepancy stemmed from inadequate liquid flow in the commercial equipment utilized. To ensure uniform impregnation across all wood samples, equipment guaranteeing consistent, continuous liquid flow around the samples is essential. However, the current grant did not allocate sufficient financial resources for this purpose.

2.2. Preparation of the Specimens

  • Wood Specimens: Two different sizes of wood specimens, measuring 30 mm × 30 mm × 10 mm and 50 mm × 50 mm × 10 mm, were cut from various wood species, including Scots pine (Pinus sylvestris), Norway spruce (Picea abies), silver birch (Betula pendula), black alder (Alnus glutinosa), aspen (Populus tremula), ash (Fraxinus excelsior), and oak (Quercus robur). The specimens were subsequently dried (Figure 1) and marked.

2.3. Preparation of Humate Solution and Impregnation Solution, and Vacuum Impregnation Procedure

  • Humate solution preparation: A humate solution was prepared by mixing well-decomposed dark peat with warm water (36–40 °C) and 25% liquid ammonia (5 vol % mixture).
  • Impregnation solutions: Five impregnation solutions were created using the humate base solution:
    • Humate base solution (500 mL) with 50 g of ground oil shale ash and 20 g of silica fume.
    • Humate base solution (500 mL) with 50 g of oil shale ash.
    • Humate base solution (500 mL) with 20 g of silica fume.
    • Humate base solution (500 mL).
    • Distilled water (500 mL) with 50 g of oil shale ash and 20 g of silica fume.
  • Vacuum impregnation: Specimens were impregnated within a vacuum tank (see Figure 2). The vacuum was set to −1.0 bar for 1 h to remove air from the wood. Subsequently, the specimens were immersed in the impregnation solution, allowing it to penetrate the wood’s veins for 24 h. Afterward, the specimens were rinsed with water and dried at 105 °C for 24 h.

2.4. SEM Studies

Slices with a thickness of 5 mm were Q11 cut with an LKB ULTROTOME® V (LKB Bromma/GE HealthCare; Chicago, IL, USA) ultramicrotome and attached to aluminum stubs with double-sided adhesive tape. Then, the samples were coated with Au/Pd by ion sputtering to enhance the electrical conductivity.
Investigation of the surface morphology of the samples was carried out with a ZEISS EVO MA15 (Carl Zeiss AG; Oberkochen, Germany) scanning electron microscope at 10 kV. The elemental composition of the cementitious precipitates was studied with an EVOMA15 scanning electron microscope (SEM) equipped with an Inca energy-dispersive X-ray spectrometer (EDS; Thermo Fisher Scientific, Waltham, MA, USA) with anX-Max 50 mm2 detector (Oxford Instruments; Abingdon, UK) with an acceleration voltage of 15 keV.

2.5. Tests with Termites

Termite (Reticulitermes flavipes) populations with 200 workers were ordered from Carolina Biological Supply. The vivarium was established with substrate made of peat, sand, and compost. The vivarium was regularly moistened. The treated blocks were kept in water for 24 h and replaced into the vivarium. The timber for vacuum-treated blocks was Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L.). The colony was active for 1.5 months.
Since the number of colonies of termites was limited, we only had the opportunity to test each wood species once. Therefore, the termite tests were only indicative. In future studies, we intend to repeat the termite tests with a relevant number of replicas and using different species of wood-damaging insects.

2.6. Fire Tests

The fire behavior of the treated samples was measured using a cone calorimeter according to the international standard ISO 5660-1:2015/Amd 1:2019 [37]. Cone calorimetry is one of the most effective fire behavior tests for different materials. The sample (100 mm × 100 mm × 4 mm) is placed on the sample holder to evaluate the evolution of mass loss during the experiment. A conical electrical heater uniformly irradiates the sample from the top. The combustion is triggered by an electric spark. The combustion gases are captured from the exhaust tube with a centrifugal fan (Figure 3). The gas flow, O2, CO, and CO2 concentrations and smoke density are registered during the test process [38].
The gas flow and O2/CO2 concentration measurements are used to calculate the heat release per unit of time and surface area: heat release rate (HRR) is expressed in kW/m2. The change in the HRR over time, in particular its peak/maximum, determines the fire properties of the material. All the measurements were made according to the standard ISO 5660-1:2015/Amd 1:2019 [37].
The following parameters were measured:
  • Total heat release;
  • Total oxygen consumed;
  • Mass loss;
  • Average specific mass loss rate;
  • Total smoke release;
  • Total smoke production (6.0 m²);
  • Mean peak time;
  • Heat release rate;
  • Effective heat of combustion;
  • Mass loss rate;
  • Specific extinction area;
  • Carbon monoxide yield;
  • Carbon dioxide yield.

3. Results and Discussion

3.1. SEM Studies

The SEM study of the wood specimen showed that the impregnating agents penetrated into the wood at different depths from 0.5 to 5 mm. When normally treated, the samples showed excellent precipitation of the concrete material onto the walls of the wood tracheids (Figure 4).
The chemical composition of the precipitate was analyzed, and a high amount of the cementitious material (Ca, Mg)O·xSiO2·yH2O was detected. The spectrum is depicted in Figure 5. The lines of gold and palladium descend from the conductive coating.
In some cases, the precipitation had begun, but the thickness of the concrete layer was insufficient (see Figure 6).

3.2. Fire-Resistance Tests

The fire resistance of the samples was assessed using cone calorimetry, a widely recognized method for evaluating fire behavior. It is essential to note that there is no consensus within the scientific community for interpreting cone calorimeter measurements [39]. Various parameters, such as mass loss, heat release rate (HRR), effective heat of combustion, combustion efficiency, and gas flows, are considered and discussed.
The fire behavior in different stages can be characterized using the following properties [39]:
(1)
Ignition
  • Ignitability;
  • Flammability;
(2)
Developing fire
  • Flame spread;
  • Heat release;
  • HRR;
(3)
Fully developed fire
  • Heat penetration;
  • Fire penetration/fire resistance;
  • Heat release/fire load.
Building fire regulations and test methods vary across countries, even within the European Union [40]. There is no direct correlation between cone calorimeter test results and EU regulations. Nonetheless, the HRR, specifically the difference in the HRR curves between treated and untreated materials [41], is particularly relevant for characterizing the fire-retardant properties of a specific treatment.
It is important to note that due to variations in the impregnation process (non-uniform liquid flow leading to unequal immersion of surfaces), samples with effective impregnation, identifiable by their intense brown coloration, exhibited superior results in fire-resistance tests. In contrast, parameters of less-treated specimens resembled those of untreated ones.
In Figure 7, the heat release rates of untreated (a) and treated (b) black alder wood samples are presented.
A significant decline in the graph of treated wood is evident. This indicates that after the initial ignition of the sample surface, the heat release substantially diminished. This effect can be attributed to two key factors:
  • Capping effect: The concrete cork applied to the wood tracheids acts as a barrier, impeding heat flow into the material.
  • Endothermic release of carbon dioxide: The decomposition of the concrete material leads to the endothermic release of carbon dioxide, which, in turn, cools the fire front and obstructs the access of atmospheric oxygen.
Similar results were obtained in a previous study, where precipitation of CaCO3 was studied in the veins of poplar wood pretreated with NaOH and then subjected to sequential impregnation with sodium alginate, CaCl2, and (NH4)2CO3 solutions. The treated wood showed significantly lower HRRs in comparison with untreated wood as well as improvements in other fire-resistance characteristics. The authors also attributed these results to the formation of an adiabatic char layer on the surface of the wood, slowing down the heat transfer through the charcoal layer [42].
The graphs of different samples exhibit noticeable differences based on the depth of penetration by the treating agent. A significant proportion of the specimens displayed minimal effects, highlighting the influence of treatment depth on fire-resistance outcomes.

3.3. Tests with Termites

Repeated experiments with termites showed that although termites damaged the surface of both impregnated and untreated wood, the damage was significantly greater in untreated wood. Furthermore, feeding on impregnated wood caused extinction of all termite colonies within 1.5 months. The termite colonies feeding on untreated specimens were fully viable during the entire test period. According to the literature, humic substances act as natural pesticides and repellents for wood-damaging insects [43]. Humic substances are known for their fungicidal and bactericidal effects [44]. Salts of humic acids with Ca and Mg are insoluble in water [36] and precipitate in wood veins, acting as sustainable natural wood preservatives and making them more resistant to insect attack. Moreover, the build-up of crystalline (Ca, Mg)O·xSiO2·yH2O phases in the wood veins (see Section 2.4) additionally inhibits the leaching out of humic substances and provides a physical barrier to wood-eating insects to reach organic wood fibers as well as a barrier to wood-degrading fungi and bacteria. Additionally, alkaline pore water may contribute to the antifungal, antibacterial, and insect-repelling effects of impregnation. The pH of the fresh impregnation solution exceeded 13, but after crystallization had completed, the pH value had decreased to approximately 9.

3.4. Impacts on Mechanical Properties and Moisture Resistance

One of the key advantages of employing wood treated with our developed method in the construction sector is the ability of impregnated wood to minimize pore filling with crystallized composites, thereby reducing wood stitching and mitigating internal stresses during the drying process. This attribute proves invaluable in applications involving frame constructions with carpentry joints, as they are no longer susceptible to distortions caused by fluctuations in moisture levels. However, further studies are necessary to confirm these expectations.
In our tests, impeccably dry impregnated wood (Pinus) displayed significantly less warping, averaging just 1.66% of thickness, in contrast to absolutely dry untreated wood, which exhibited standard warping levels, averaging 3.15% of thickness. Additionally, treated wood demonstrated reduced moisture expansion and shrinkage during drying. It is our belief that impregnation, leading to the crystallization of composites within the wood veins, contributes to the preservation of the wood’s original geometric shape and enhances its flexural strength. A study by Zhang et al. showed that CaCO3 precipitation in poplar wood veins resulted in a 38% increase in flexural strength and a 53% increase in compressive strength compared to the control, as well as in higher wood density [42].
Furthermore, this process is expected to decrease the occurrence of paint cracks, including fireproofing coatings, and results in a harder wood surface, thereby improving abrasion resistance.
It is worth noting that the impregnation is long-lasting and does not hinder subsequent wood processing activities, such as cutting, sawing, sanding, or finishing. This flexibility allows the technology to be applied across a wide range of applications, including building materials, wooden structures, and covering materials. However, one limitation is that this process cannot be applied to completed structures at construction sites. Nevertheless, it can be seamlessly integrated into various mechanized and automated manufacturing processes.
Importantly, our method employs only nonhazardous components for impregnation. As a result, in the end-of-life products, impregnated timber can be repurposed for other uses or managed as nonhazardous waste. This aligns with sustainability goals and offers an environmentally responsible approach to wood treatment and disposal.

4. Conclusions

Our research demonstrates the successful development of an efficient wood protection system that relies on lime-containing waste materials, such as oil shale ash and wood ash, in combination with pozzolanic additives, specifically silica fume derived from metallurgical processes, and a solution of peat humates. Importantly, our method achieves wood protection without the use of hazardous ingredients. The timber treated using this approach not only exhibits outstanding fire-retardant properties but also stands out for its sustainability, as it does not generate any hazardous waste and is entirely recyclable.
While the outcomes of our study have been highly promising, it is essential to acknowledge that the setup of the vacuum treatment presented challenges, leading to uneven processing depths within the specimens. To attain more consistent and reliable results, it is imperative to design a treatment apparatus with a constant flow of the agents, ensuring uniform impregnation.
We consider our experimental results as proof of concept, which we believe can attract interest from a broader spectrum of scientists. Despite the limitations posed by the treatment apparatus, the results we have obtained are truly remarkable. They are on par with or even superior to those achieved using synthetic wood preservatives. This underscores the potential of our approach in providing effective and environmentally friendly wood protection, furthering the sustainable goals of the construction and forestry industries.

Author Contributions

Conceptualization and methodology was carried out by J.L.; experimental and investigation by T.T.; chemical analyses and data curation by J.L. and M.S.; writing—original draft preparation by J.L. and E.R.; writing—review and editing by M.S. and E.R.; supervision by T.T.; project administration by M.S.; funding acquisition by T.T. All authors have read and agreed to the published version of the manuscript.

Funding

The study was funded by the Estonian Environmental Investment Centre, KIK 16806.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Acknowledgments

The authors thank Urve Kallavus from Tallinn Technical University for her assistance with the SEM microscopy.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analysis, or interpretation of the data; in the writing of the manuscript; or in the decision to publish the results.

References

  1. Kalt, G. Carbon dynamics and GHG implications of increasing wood construction: Long-term scenarios for residential buildings in Austria. Carbon Manag. 2018, 9, 265–275. [Google Scholar] [CrossRef] [PubMed]
  2. Carrington, D. World Close to ‘Irreversible’ Climate Breakdown, Warn Major Studies. The Guardian. 27 October 2022. Available online: https://www.theguardian.com/environment/2022/oct/27/world-close-to-irreversible-climate-breakdown-warn-major-studies (accessed on 19 December 2022).
  3. Blanchet, P.; Breton, C. Wood productions and renewable materials: The future is now. Forests 2020, 11, 657. [Google Scholar] [CrossRef]
  4. Falk, B. Wood as a sustainable building material. For. Prod. J. 2009, 59, 6–12. [Google Scholar]
  5. International Code Council. International Building Code; International Code Council, Inc., 2018; Available online: https://codes.iccsafe.org/content/IBC2018P6 (accessed on 5 February 2020).
  6. Przystupa, K.; Pieniak, D.; Samociuk, W.; Walczak, A.; Bartnik, G.; Kamocka-Bronisz, R.; Sutuła, M. Mechanical Properties and Strength Reliability of Impregnated Wood after High Temperature Conditions. Materials 2020, 13, 5521. [Google Scholar] [CrossRef] [PubMed]
  7. Ulyshen, M.D. Wood decomposition as influenced by invertebrates. Biol. Rev. 2016, 91, 70–85. [Google Scholar] [CrossRef] [PubMed]
  8. Hernández-Teixidor, D.; Suárez, D.; García, J.; Mora, D. First report of the invasive Reticulitermes flavipes (Kollar, 1837) (Blattodea, Rhinotermitidae) in the Canary Islands. J. Appl. Entomol. 2019, 143, 478–482. [Google Scholar] [CrossRef]
  9. Chu, D.; Mu, J.; Avramidis, S.; Rahimi, S.; Liu, S.; Lai, Z. Functionalized surface layer on poplarwood fabricated by fire retardant and thermal densification. Part 2: DynamicWettability and bonding strength. Forests 2019, 10, 982. [Google Scholar] [CrossRef]
  10. Gan, W.; Chen, C.; Wang, Z.; Song, J.; Kuang, Y.; He, S.; Mi, R.; Sunderland, P.B.; Hu, L. Dense, Self-Formed Char Layer Enables a Fire-Retardant Wood Structural Material. Adv. Funct. Mater. 2019, 29, 1807444. [Google Scholar] [CrossRef]
  11. Novel, D.; Ghio, S.; Gaiardo, A.; Picciotto, A.; Guidi, V.; Speranza, G.; Boscardin, M.; Bellutti, P.; Pugno, N.M. Strengthening of wood-like materials via densification and nanoparticle intercalation. Nanomaterials 2020, 10, 478. [Google Scholar] [CrossRef]
  12. Coudert, L.; Blais, J.F.; Mercier, G.; Cooper, P.; Janin, A. Remediation processes for wood treated with organic and/or inorganic preservatives. In Handbook of Recycled Concrete and Demolition Waste; 2013; pp. 526–554. Available online: https://www.sciencedirect.com/science/article/abs/pii/B978085709682150021X?via%3Dihub (accessed on 5 February 2020).
  13. Dias, K.B.; Barreiros, R.M.; Dias, K.B.; Barreiros, R.M. Preservative Treatments on Wood and Their Effects on Metal Fasteners. In Engineered Wood Products for Construction; Intech Open: London, UK, 2021. [Google Scholar] [CrossRef]
  14. Rabajczyk, A.; Zielecka, M.; Malozieć, D. Hazards Resulting from the Burning Wood Impregnated with Selected Chemical Compounds. Appl. Sci. 2020, 10, 6093. [Google Scholar] [CrossRef]
  15. Park, B.-K. Fireproofint Treatment Method Using Water Glass. WO2004062815A1, 16 January 2003. Available online: https://patents.google.com/patent/WO2004062815A1/en (accessed on 5 February 2020).
  16. Prabhakar, M.N.; Shah, A.U.R.; Song, J.-I. A Review on the Flammability and Flame Retardant Properties of Natural Fibers and Polymer Matrix Based Composites. Compos. Res. 2015, 28, 29–39. [Google Scholar] [CrossRef]
  17. Popescu, C.M.; Pfriem, A. Treatments and modification to improve the reaction to fire of wood and wood based products—An overview. Fire Mater. 2020, 44, 100–111. [Google Scholar] [CrossRef]
  18. Harada, T.; Nakashima, Y.; Anazawa, Y. The effect of ceramic coating of fire-retardant wood on combustibility and weatherability. J. Wood Sci. 2007, 53, 249–254. [Google Scholar] [CrossRef]
  19. Goldsmith, F.P. Fire Retardant Coatings: An Evaluation of Fire Retardant Coatings as a Means of Protecting Wood Panels. 2011. Available online: https://open.library.ubc.ca/collections/52966/items/1.0103122 (accessed on 5 February 2020).
  20. Luo, J. Ignition Properties of Panels Coated with Finishing Fire-Retardant Paints under External Radiation. Procedia Eng. 2016, 135, 123–127. [Google Scholar] [CrossRef]
  21. Schwarzkopf, M. Densified wood impregnated with phenol resin for reduced set-recovery. Wood Mater. Sci. Eng. 2021, 16, 35–41. [Google Scholar] [CrossRef]
  22. Navi, P.; Heger, F. Combined densification and thermo-hydro-mechanical processing of wood. MRS Bull. 2004, 29, 332–336. [Google Scholar] [CrossRef]
  23. Gilka-Bötzow, A.; Heiduschke, A.; Haller, P. The velocity of combustion in relation to the density of wood. Eur. J. Wood Wood Prod. 2011, 69, 159–162. [Google Scholar] [CrossRef]
  24. Chen, H.; Zhang, Y.; Zhong, T.; Wu, Z.; Zhan, X.; Ye, J. Thermal insulation and hydrophobization of wood impregnated with silica aerogel powder. J. Wood Sci. 2020, 66, 81. [Google Scholar] [CrossRef]
  25. Gabrielli, C.P.; Kamke, F.A. Phenol-formaldehyde impregnation of densified wood for improved dimensional stability. Wood Sci. Technol. 2010, 44, 95–104. [Google Scholar] [CrossRef]
  26. de Lima, A.J.M.; Iwakiri, S.; Satyanarayana, K.G.; Lomelí-Ramírez, M.G. Studies on the durability of wood-cement particleboards produced with residues of pinus spp., silica fume, and rice husk ash. BioResources 2020, 15, 3064–3086. [Google Scholar] [CrossRef]
  27. Yang, T.; Xia, M.; Chen, S.; Mu, M.; Yuan, G. Enhancing the thermal stability of silica-mineralized wood via layer-by-layer self-assembly. J. Therm. Anal. Calorim. 2021, 145, 309–318. [Google Scholar] [CrossRef]
  28. Lin, C.F.; Karlsson, O.; Mantanis, G.I.; Sandberg, D. Fire performance and leach resistance of pine wood impregnated with guanyl-urea phosphate/boric acid and a melamine-formaldehyde resin. Eur. J. Wood Wood Prod. 2020, 78, 107–111. [Google Scholar] [CrossRef]
  29. Caiping, L. Effect of phosphate treatment on interfacial properties of poplar fiber/high-density polyethylene composites. Compos. Adv. Mater. 2021, 30, 263498332110246. [Google Scholar] [CrossRef]
  30. Gebke, S.; Thümmler, K.; Sonnier, R.; Tech, S.; Wagenführ, A.; Fischer, S. Flame retardancy of wood fiber materials using phosphorus-modified wheat starch. Molecules 2020, 25, 335. [Google Scholar] [CrossRef] [PubMed]
  31. Slimak, K.M.; Slimak, R.A. Process of Using Sodium Silicate to Create Fire Retardant Products. US6303234B1, 14 March 1997. Available online: https://patents.google.com/patent/US6303234B1/en (accessed on 5 February 2020).
  32. Medina, L.; Schledjewski, R. Water Glass As Hydrophobic Additive for Natural Fi- Ber Reinforced Composites. J. Nanostruct. Polym. Nanocompos. 2009, 5, 107–114. [Google Scholar]
  33. Medina, L.; Schledjewski, R.; Schlarb, A.K. Process related mechanical properties of press molded natural fiber reinforced polymers. Compos. Sci. Technol. 2009, 69, 1404–1411. [Google Scholar] [CrossRef]
  34. Luo, X.; Gong, H.; He, Z.; Zhang, P.; He, L. Recent advances in applications of power ultrasound for petroleum industry. Ultrason. Sonochem. 2021, 70, 105337. [Google Scholar] [CrossRef] [PubMed]
  35. Özcan, C.; Esen, R.; Likos, E.; Kurt, Ş.; Yapici, F. The Effects of Fire Retardants Paint on Combustion Properties of Fir Wood. J. For. Fac. Kastamonu Univ. 2012, 12, 124–126. [Google Scholar]
  36. Liiv, J.; Teppand, T.; Rikmann, E.; Tenno, T. Novel ecosustainable peat and oil shale ash-based 3D-printable composite material. Sustain. Mater. Technol. 2018, 17, e00067. [Google Scholar] [CrossRef]
  37. ISO 5660-1:2015/Amd 1:2019 Reaction-to-Fire Tests—Heat Release, Smoke Production and Mass Loss Rate—Part 1: Heat Release Rate (Cone Calorimeter Method) and Smoke Production Rate (Dynamic Measurement). Amendment 1. Edition 3, 2019. Available online: https://www.iso.org/standard/75739.html (accessed on 5 February 2020).
  38. Dewaghe, C.; Lew, C.Y.; Claes, M.; Belgium, S.A.; Dubois, P. Fire-retardant applications of polymer-carbon nanotubes composites: Improved barrier effect and synergism. In Polymer–Carbon Nanotube Composites; Woodhead Publishing: Sawston, UK, 2011; pp. 718–745. [Google Scholar] [CrossRef]
  39. Schartel, B.; Hull, T.R. Development of fire-retarded materials—Interpretation of cone calorimeter data. Fire Mater. 2007, 31, 327–354. [Google Scholar] [CrossRef]
  40. Blomqvist, P.; McNamee, M.S.; Thureson, P. Compilation of International Building Regulations (Fire) Relevant for EPS/XPS: SP Technical Note 2010:10, Revised 2011-11-30. Fire Technology. 2011. Available online: https://www.researchgate.net/publication/324038076_Compilation_of_International_Building_Regulations_Fire_Relevant_for_EPSXPS (accessed on 6 September 2021).
  41. White, R.H.; Dietenberger, M.A. Cone Calorimeter Evaluation of Wood Products. Recent Adv. Flame Retard. Polym. Mater. 2004, 331–343. Available online: https://www.fs.usda.gov/treesearch/pubs/8450 (accessed on 6 September 2021).
  42. Zhang, M.; Li, H.; Wang, C.; Wang, Z.; Liu, D.; Yang, T.; Deng, Z.; Yuan, G. Performance Enhancement of the Poplar Wood Composites Biomimetic Mineralized by CaCO3. ACS Omega 2022, 7, 29465–29474. [Google Scholar] [CrossRef]
  43. May, A.K.A.; Shamsuddin, R.; Hau, L.J.; Aqsha, A.; Mansor, N.; Mustapa, N.I.; Narasimha, M. Investigation of pesticidal ability of humic acid derived from palm oil Empty Fruit Bunch (EFB) vermicompost. Int. J. Recycl. Org. Waste Agric. 2020, 9, 237–247. [Google Scholar] [CrossRef]
  44. Savy, D.; Di Meo, V.; Verrillo, M.; Cangemi, S.; Cozzolino, V.; Piccolo, A. Novel Nanomaterials Made of Humic Substances from Green Composts and Chitosan Exerting Antibacterial Activity. ACS Sustain. Chem. Eng. 2023, 11, 9674–9683. [Google Scholar] [CrossRef]
Figure 1. Drying the wood samples.
Figure 1. Drying the wood samples.
Applsci 14 05179 g001
Figure 2. Equipment for vacuum treatment of wood samples. Bottom left: test specimen placed in holders in the vacuum chamber. Bottom right: test specimens immersed in the impregnation suspension; air is bubbling out of the wood veins.
Figure 2. Equipment for vacuum treatment of wood samples. Bottom left: test specimen placed in holders in the vacuum chamber. Bottom right: test specimens immersed in the impregnation suspension; air is bubbling out of the wood veins.
Applsci 14 05179 g002
Figure 3. Working principle of the cone calorimeter.
Figure 3. Working principle of the cone calorimeter.
Applsci 14 05179 g003
Figure 4. Empty wood veins (a) and veins with successful concrete precipitation (b).
Figure 4. Empty wood veins (a) and veins with successful concrete precipitation (b).
Applsci 14 05179 g004
Figure 5. Elemental composition of the precipitate.
Figure 5. Elemental composition of the precipitate.
Applsci 14 05179 g005
Figure 6. Wood veins with weak precipitation of concrete.
Figure 6. Wood veins with weak precipitation of concrete.
Applsci 14 05179 g006
Figure 7. Heat release rates of untreated (a) and treated (b) black alder wood.
Figure 7. Heat release rates of untreated (a) and treated (b) black alder wood.
Applsci 14 05179 g007
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Liiv, J.; Rikmann, E.; Shanskiy, M.; Teppand, T. Ecological Wood Protection System against Fire, Fungi and Insect Damage Using Humic Acids and Fly Ash. Appl. Sci. 2024, 14, 5179. https://doi.org/10.3390/app14125179

AMA Style

Liiv J, Rikmann E, Shanskiy M, Teppand T. Ecological Wood Protection System against Fire, Fungi and Insect Damage Using Humic Acids and Fly Ash. Applied Sciences. 2024; 14(12):5179. https://doi.org/10.3390/app14125179

Chicago/Turabian Style

Liiv, Jüri, Ergo Rikmann, Merrit Shanskiy, and Tõnis Teppand. 2024. "Ecological Wood Protection System against Fire, Fungi and Insect Damage Using Humic Acids and Fly Ash" Applied Sciences 14, no. 12: 5179. https://doi.org/10.3390/app14125179

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop