Category: Graphene Oxide

Innovation with Graphene

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Innovation with Graphene:

Towards a More Sustainable and Efficient Cement Industry

Part 1

Carbon dioxide (CO2) is a colorless, odorless, and non-toxic gas naturally present in the atmosphere. Under normal conditions, it should remain balanced to retain the heat necessary for human survival without becoming a greenhouse gas. However, overpopulation, industrialization, and environmental exploitation have disrupted this balance, making CO2 levels increasingly difficult to control. Consequently, these levels rise, concentrate, absorb radiation, and prevent heat from escaping, contributing to global warming.

According to statistics, cement production and the fossil fuel industry (coal, oil, and natural gas) are responsible for releasing about 90% of CO2 and probably 70% of greenhouse gases. Other industries, such as agriculture, fashion, and transportation, also contribute.

“Sustainability of our civilization depends on whether we can provide energy, food, and chemicals to the growing population without compromising the long-term health of our planet.” Doria-Serrano, 2009.

Concerning cement, the main component of concrete, reports mention that it alone accounts for between 7% and 8% of global CO2 emissions. For reference, producing one ton of clinker, the main component of cement, releases approximately ~0.86 tons of CO2, of which around 60% comes from the transformation of limestone into calcium oxide or lime at an average temperature of 1450 °C, a process also known as clinker burning. The remaining 40% is attributed to the combustion of fossil fuel (coal) necessary for the calcination of limestone and clinker formation.

“In 2021, carbon emissions from cement production reached nearly 2,900 million tons of carbon dioxide, while in 2002, 1,400 million tons were recorded.” The Global Carbon Project.

Therefore, to achieve the net-zero emissions target by 2050 required by the Paris Agreement, the cement industry has been forced to take measures to reduce its impact by using alternative fuels (biomass, tires, urban solid waste); improving energy efficiency by reducing the clinkerization temperature through fluxes and mineralizers (such as CaF2, BaO, SnO2, P2O5, Na2O, NiO, ZnO, etc.) or by renewing kilns; modifying cement chemistry with supplementary materials to reduce clinker consumption or capture CO2; and, recently, using graphene to improve the quality of cement and concrete.

“By 2050, global concrete consumption is expected to increase by 12% to 23% from 25 billion per year.”

According to the National Cement Chamber (CANACEM), most projects registered in Latin America are working on replacing fossil fuels with alternative fuels; Mexico is the only country registering higher production of blended cements to reduce clinker content.

Graphene is a nanomaterial consisting of atomic carbon sheets separated from graphite, with mechanical, electrical, thermal, and barrier properties superior to other carbon-based materials, allowing it to venture into countless applications and industries, including construction. According to estimates by Graphene Flagship, the use of graphene in construction is expected to reduce CO2 emissions by 30%.

“The production of 1 kg of graphene produces 0.17 kg of CO2, compared to 0.86 kg of CO2 for Portland cement, reinforcing the nanomaterial’s environmental advantages.”

Since the isolation of graphene in 2004 and the subsequent Nobel Prize in Physics 2010 awarded to its discoverers, an international race began to study, understand, and obtain the nanomaterial in sufficient quantities for large-scale applications at an affordable cost. In the construction sector, it was not until 2018 that research and investments manifested their first results in various parts of the world, such as:

2018: Graphenemex® launched Nanocreto®, the world’s first graphene oxide concrete additive (Mexico).

2019: Graphenenano developed Smart additives, graphene additives for concrete (Spain).

2019: GrapheneCA presented its OG concrete admix product line for the concrete industry (USA).

2021: Scientists at the University of Manchester developed the Concretene concrete additive (UK).

2022: Energeia Fusion-Graphenemex® launched the Graphenergy construction line, an improved version of Nanocreto® (Mexico).

2022: Versarien presented Cementene™, the world’s first 3D-printed construction with a graphene-reinforced mix (UK).

Basquiroto de Souza and collaborators, in their article “Graphene opens pathways to a carbon-neutral cement industry” published in 2022 in Science Bulletin, summarized the opportunities that graphene has for the sustainability of construction materials:

Reduction of Portland cement thanks to significant improvements in compressive strength and elastic modulus of concrete.

Increase the use of by-products or recycled materials in concrete to reduce greenhouse gas emissions by up to 7%, as well as a 2% reduction in energy consumption during the manufacture of graphene oxide reinforced mortar.

Reduction in construction costs due to improved strength or greater incorporation of by-products or waste materials. A cost analysis concluded that while the use of graphene oxide may slightly increase concrete costs, the economy index (compressive strength/cost per m3) of the mixes can increase by up to 40%.

Reduction in maintenance costs. By improving the quality of concrete structures, reductions in CO2 emissions are inferred through a reduction in the amount of construction materials and energy associated with maintenance.

Energy-efficient buildings: graphene’s thermal properties can also be applied to buildings to achieve energy savings by reducing the use of cooling/heating systems.

For Energeia-Graphenemex®, the leading company in Latin America in designing applications with graphene materials, it is a pride to be part of the graphene timeline for sustainable construction.

Authored by: EF/DHS

References

  1. Ige, O.E.; Olanrewaju, O.A.; Duffy, K.J.; Collins, O.C. Environmental Impact Analysis of Portland Cement (CEM1) Using the Midpoint Method. Energies 2022, 15, 2708.
  2. International Energy Agency, World Business Council for Sustainable Development. Technology roadmap – low-carbon transition in the cement industry. April 2018
  3. Felipe Basquiroto de Souza, Xupei Yao, Wenchao Gao, Wenhui Duan, Graphene opens pathways to a carbon-neutral cement industry, Science Bulletin, 2022, 67, 1, 2022, 5
  4. Papanikolaou I, Arena N, Al-Tabbaa A. Graphene nanoplatelet reinforced concrete for self-sensing structures– a lifecycle assessment perspective. Journal of Cleaner Production, 2019, 240: 118202
  5. Devi S, Khan R. Effect of graphene oxide on mechanical and durability performance of concrete. Journal of Building Engineering, 2020, 27: 101007
  6. Doria- Serrano. Química verde: un nuevo enfoque para el cuidado del medio ambiente. Educación química. 2009. UNAM.
  7. https://theplanetapp.com/que-son-las-emisiones-de-co2/
  8. https://graphene-flagship.eu/materials/news/materials-of-the-future-graphene-and-concrete/#:~:text=Graphene%2Denhanced%20concrete%20is%202.5,CO2%20emissions%20by%2030%25.
  9. https://www.versarien.com/files/5716/3050/8952/White_Paper_-_Graphene_for_the_construction_sector_-_final_version.pdf

Innovation in Non-Stick Coatings

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Innovation in Non-Stick Coatings:

Integration of Graphene Materials for Enhanced Properties and Performance

Currently, non-stick coatings refer to coatings that, to some extent, prevent the adhesion of substances, whether solid or liquid, to the surface they are applied on. The non-stick capability of these coatings is based on their very low surface tension, also known as surface energy, represented by “γ”.

For coatings to be considered non-stick, they must have a surface energy, γ, less than 26 mJ/m² and water contact angles greater than 90°. A surface where the drop forms a contact angle greater than 90° is a hydrophobic surface. This condition implies low wettability, adhesiveness, and surface energy (see Fig. 1). In contrast, if the surface is hydrophilic, a contact angle less than 90° will be observed, and the wettability, adhesiveness, and surface energy will be high.

Fig. 1 Scheme representing the contact angles of a hydrophobic and hydrophilic surface.

Industrially, there are multiple non-stick coatings based on fluoropolymers. The uses and applications of fluoropolymers in coatings cover a wide range of products. The non-stick effect and easy demolding allow their use in various industries, such as textile, chemical, automotive, and food industries, for the production of utensils, molds, tools, and equipment that need to be isolated from chemicals or food.

Most non-stick coatings have high thermal resistance; however, they do not have great abrasion resistance. The use of fluoropolymers in kitchen utensils raises concerns about the potential health risks, as harmful substances might be released during use.

In recent years, Energeia – Graphenemex®, a Mexican company leading in graphene material production, has implemented the use of these carbon-based nanomaterials. Graphene materials, such as graphene oxide and graphene, enhance properties in coatings, for example, anticorrosive, antibacterial, greater abrasion resistance, and high UV resistance.

During these property evaluations, it was observed that graphene materials can also be used as new additives for developing non-stick coatings. Incorporating graphene materials into epoxy-type coatings improved substrate adhesion; however, the finish of these coatings was smoother and shinier. When exposed to a corrosive environment, the coating showed hydrophobic behavior, keeping its surface cleaner compared to the control coating (without graphene material), which gradually lost its shine and showed wettability and contaminant deposition on the coating surface (see Fig. 2).

Fig. 2 Non-stick effects of coatings with graphene material.

Furthermore, the non-stick effect of an ecological coating with and without graphene material was evaluated. This coating is made of lime, nopal mucilage, and mineral pigments. It is well known that lime and carbonate-based materials absorb moisture easily, so the effect of graphene material in lime-based paint was studied. The results showed that the paint had an antimicrobial effect, greater UV resistance, and higher impermeability (non-stick effect).

In Fig. 3, the response of a lime-based coating with and without graphene material, when wetted by water, is shown. The coatings with graphene materials (Graphene and graphene oxide (GO)) at different concentrations showed very little deformation in the drop as its internal energy was higher than the surface energy, displaying hydrophobic behavior (water repellency). In the case of the control coating (without graphene material), it was observed to have very little non-stick capacity, absorbing water more easily due to high surface energy. The drop spread on the surface immediately when the water drop fell on the surface, showing highly hydrophilic behavior. These results showed that graphene materials modified the nature of the coating, i.e., they modified the surface energy of the coatings at the surface level.

Fig. 3 Wetting behavior of a lime-based coating, with and without graphene materials.

Currently, Energeia – Graphenemex®, a leading Mexican company in Latin America in the research and production of graphene materials for industrial application development, offers various types of graphene materials for use in developing and producing anticorrosive, antibacterial, and enhanced non-stick coatings.

References

  1. Tong, Yao &Song, Mo. (2013). Graphene based materials and their composites as coatings.
  2. Zhen, Z. & Zhu, H. Graphene: Fabrication, Characterizations, Properties and Applications. Graphene (Academic Press, 2018).
  3. Sachin Sharma Ashok Kumar, Shahid Bashir, K. Ramesh, S. Ramesh, Progress in Organic Coatings, 154, (2021)

Graphene Oxide Versatile Applications

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Graphene Oxide Versatile Applications:

From Sensing Technologies to Environmental Solutions

Graphene and its derivatives such as graphene oxide (GO) and reduced graphene oxide (rGO) are two-dimensional, sheet-like carbon nanomaterials with a wide range of opportunities for numerous applications due to their thinness, transparency, conductivity, flexibility, chemical stability, impermeability, and mechanical strength. In the case of GO and rGO, in addition to their large surface area with hydrophilic and hydrophobic regions inherent to graphene, they allow the adsorption of organic aromatic molecules, ions, and polymers through π-π stacking, hydrogen bonding, and electrostatic interactions. These properties make them suitable materials for constructing sensors or biocatalytic and photocatalytic platforms. According to various reports, the surface-to-volume ratio of graphene materials enhances the surface charge of the desired molecules, while their excellent electrical conductivity, especially at room temperature, favors electron transfer to the surface of electrodes for analysis or photocatalysis.

On the other hand, graphene sheets are not perfectly flat; they exhibit undulations formed as a result of the bonding between their carbon atoms or thermal fluctuations, which can ultimately induce magnetic fields and alter their electronic properties for designing sensors, biosensors, or electronic devices in general. Thus, through more than ten years of research and exploration of their remarkable multifunctionality, the study of graphene has transcended to the development of highly sensitive devices for monitoring, for example, the presence of harmful gases, medically relevant molecules, or proteins, and even water decontamination.

Detection Systems

Metamaterials are a type of compound with the ability to produce useful electromagnetic responses for designing sensors or non-destructive detection devices. Generally, these sensors consist of an insulating material and a conductive material, sensitive to the refractive index of the analyte’s upper layer. In the presence of graphene, it has been observed that this interaction (sensor-analyte) is enhanced by changes in resonance intensity, leading to amplitude changes that further favor detection sensitivity.

In a study conducted in 2023 by the School of Electronic and Information Engineering at Zhejiang University of Science and Technology, Hangzhou, China, a sensor was designed comprising a polyimide (PI) film as an insulating layer, an aluminum structure as a conductive layer, and a monolayer of graphene as the detection interface. Simulation results indicated that graphene could modulate the entire electric field and produce an amplitude change that significantly increases detection limits.

In another study conducted at the Laboratory of Nanostructured Materials of the Institute of Physics at UASLP, functionalized graphene oxide with gold nanoparticles was used as a SERS (Surface Enhanced Raman spectroscopy) biodetection platform, an important technique for biological detection due to its high sensitivity, low sample requirements, relatively low cost, and real-time detection. Crystal violet was used as the standard molecule and flavin adenine dinucleotide as the experimental coenzyme for its participation in numerous redox processes of metabolic reactions and biological electron transport. The results showed that graphene oxide hybrids with gold nanoparticles substantially enhance SERS signals compared to individual nanoparticles. Additionally, the results are consistent with other research on identifying significant improvements for molecule stabilization and fluorescence reduction during measurements, which is often a major drawback of such techniques, supporting its potential as a diagnostic or monitoring tool.

Toxic Gas Removal

Advances in nanoengineering allow graphene and GO sheets to be manipulated for the detection and separation of certain gases. According to the results of a study conducted by the Department of Energy Engineering at Hanyang University, Seoul, Korea, selective diffusion can be achieved by controlling the gas flow channels and pores through different stacking methods, demonstrating that GO’s functional groups provide a unique adsorption behavior towards CO2.

CO2 Conversion

The photocatalytic properties of GO can also be harnessed for converting CO2 into hydrocarbons such as methanol for solar energy capture and CO2 reduction. In 2018, at the Advanced Technology Laboratory for Materials Synthesis and Processing, Wuhan University of Technology, China, silver chromate (Ag2CrO4) nanoparticles were used as a photosensitizer and GO as a co-catalyst for the photocatalytic reduction of CO2 into methanol and methane. The study concluded that this synergy between nanoparticles could enhance conversion activity up to 2.3 times under solar irradiation due to better light absorption, increased CO2 adsorption, and improved charge separation efficiency.

Water Decontamination

Water technologies have various areas of opportunity, particularly in improving filtration or membrane systems. In this regard, it has been found that using hybrid graphene nanostructures, for example, with ruthenium or magnetite, can allow the removal of microorganisms and organic matter present in water. However, research continues to advance to perfect graphene-based methodologies for the removal and reduction of metal ions such as zinc, copper, lead, cadmium, cobalt, among others.

At Energeia-Graphenemex®, we recognize and admire the advancements that research centers have achieved in various areas of knowledge, starting from basic science to applied science results. We firmly believe that in the short or medium term, these technologies will materialize into real products that are useful to society and the environment.

Redaction: EF/ DHS   

References

  1. A. Fasolino, J.H. Los, M.I. Katsnelson, Intrinsic ripples in graphene, Nat. Mater. 6 (2007) 858;
  2. W. Bao, F. Miao, Z. Chen, H. Zhang, W. Jang, C. Dames, C.N. Lau, Controlled ripple texturing of suspended graphene and ultrathin graphite membranes, Nat. Nanotechnol. 4 (2009) 562; 3. G. Yildiz, M. Bolton-Warberg and F. Awaja. Graphene and graphene oxide for bio-sensing: General properties and the effects of graphene ripples. Acta Biomaterialia 131 (2021) 62;
  3. Lang, T.; Xiao, M.; Cen,W. Graphene-Based Metamaterial Sensor for Pesticide Trace Detection. Biosensors 2023, 13, 560;
  4. D. Hernández- Sánchez, E. G. Villabona Leal, I. Saucedo-Orozco, V. Bracamonte, E. Pérez, C. Bittencourt and M. Quintana, Phys. Chem. Chem. Phys., 2017;
  5. Kim, H.W.; Yoon, H.W.; Yoon, S.-M.; Yoo, B.M.; Ahn, B.K.; Cho, Y.H.; Shin, H.J.; Yang, H.; Paik, U.; Kwon, S. Selective gas transport through few-layered graphene and graphene oxide membranes. Science 2013, 342, 91;
  6. Kim, D.; Kim, D.W.; Lim, H.-K.; Jeon, J.; Kim, H.; Jung, H.-T.; Lee, H. Intercalation of gas molecules in graphene oxide interlayer: The role of water. J. Phys. Chem. C 2014, 118, 11142;
  7. Xu, D.; Cheng, B.; Wang, W.; Jiang, C.; Yu, J. Ag2CrO4/g-C3N4/graphene oxide ternary nanocomposite Z-scheme photocatalyst with enhanced CO2 reduction activity. Appl. Catal. B Environ. 2018, 231, 368;
  8. Jiˇríˇcková, A.; Jankovský, O.; Sofer, Z.; Sedmidubský, D. Synthesis and Applications of Graphene Oxide. Materials 2022, 15, 920;
  9. M. Quintana, E. Vazquez & M. Prato, “Organic Functionalization of Graphene in Dispersions”, Acc. Chem. Res., vol. 46, n.o 1, pp. 138-148, 2013. DOI: 10.1021/ar300138e;
  10. Roberto Urcuyo1,2,3, Diego González-Flores1,3, Karla Cordero-Solano, Rev. Colomb. Quim., vol. 50, no. 1, pp. 51-85, 2021;
  11. B. Xue, M. Qin, J. Wu et al., “Electroresponsive Supramolecular Graphene Oxide Hydrogels for Active Bacteria Adsorption and Removal”, ACS Appl. Mater. Interfaces, 8, 24, 15120;
  12. C. Wang, C. Feng, Y. Gao, X. Ma, Q. Wu & Z. Wang, “Preparation of a graphene-based magnetic nanocomposite for the removal of an organic dye from aqueous solution”, Chem. Eng. J.,173, 1, 92.

Advancing Asphalt Durability

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Advancing Asphalt Durability:

Harnessing Graphene’s Potential for Sustainable Roads

Most of the the world’s road infrastructure is composed of pavement made from a complex system of asphalt, aggregates, and binders that interact at an interface to maintain its strength and structural stability. According to the Asphalt Institute, 87 million tons of asphalt are produced worldwide annually, with around 85% used in the paving industry, which, while offering great load capacity and durability, inevitably suffers damage from constant exposure to radiation, temperature, humidity, and traffic.

The deterioration of asphalt not only impacts a basic transportation infrastructure crucial for socio-economic development but also involves environmental impacts in terms of resource depletion and high CO2 emissions caused by roadworks. These factors add to the reasons for the constant search for modification technologies that increase durability and improve mechanical properties of pavements using fibers, rubber; additives such as thermoplastic elastomers, plastic and synthetic resins, iron powder, hydrated lime, or glass waste. However, in some cases, the application of these products can present practical problems such as special preparation conditions, low storage stability, difficulty in mixing during construction, and complexity in compatibilizing these components with the asphalt system.

Fortunately, carbon nanostructures such as graphene and graphene oxide (GO) reappear on the scene as proposed solutions to these issues with interesting contributions to asphalt regarding stiffness, anti-aging, deformation, and penetration resistance; reduction in rutting, improved consistency, heat transfer capacity; skid resistance, and even a reduction in the effort required for compaction during preparation.

Additionally, among the advantages of graphene is its ability to be mixed with other asphalt modifying technologies such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), polyethylene terephthalate (PET), polystyrene (PS), granulated rubber, blast furnace slag, epoxy resins, and especially with styrene-butadiene-styrene (SBS), which is one of the most accepted polymers in the asphalt industry, and with which graphene oxide (GO), thanks to its oxygen content, promotes the absorption of aromatics and saturates from SBS with a significant improvement in temperature response, adhesion, and binder stiffness.

Some identified methods that promise to simplify the incorporation of graphene into asphalt mixes are:

  1. Direct addition method: graphene is added to the previously melted asphalt binder.
  2. Indirect addition method: graphene and asphalt binder are simultaneously dissolved in a medium solution to later form a uniform solution.
  3. Auxiliary addition method: graphene is chemically modified with functional groups or added together with other modifying agents to later melt into the asphalt binder.

Although there are few companies that have explored graphene as an asphalt improving additive so far, the extensive research conducted over the past decade is helping to lay the groundwork for understanding and projecting the potential of this technology for the benefit of the paving industry. Even in February 2024, the Infrastructure journal published the results of the ECOPAVE project funded by the European Union, which consisted of a 5-year field test conducted over 1 km of heavy traffic in southern Rome, Italy. For the study, four sections of asphalt pavement with and without additions of graphene-modified polymers were installed. After the 5-year evaluation period, researchers reaffirmed the potential of asphalt modified with graphene polymer as an innovative and feasible technology for high-traffic road paving, as it demonstrated higher stiffness values at different temperatures, better fatigue behavior, and greater deformation resistance, promising an extended lifespan with a significant reduction in maintenance costs.

At Energeia-Graphenemex®, as leaders in graphene application development, we firmly believe that, although there is still work to be done, we are very close to enjoying the economic and environmental benefits that this wonderful technology can bring not only to our streets and roads but also to society.

Draft: EF/DHS

References

  1. Mechanism and Performance of Graphene Modified Asphalt: An Experimental Approach Combined with Molecular Dynamic Simulations. Case Studies in Construction Materials. 2023, 18, e01749;
  2. Properties and Characterization Techniques of Graphene Modified Asphalt Binders. Nanomaterials 2023, 13, 955;
  3. Analysis on the road performance of graphene composite rubber asphalt and its mixture. Case Studies in Construction Materials. 2022, 17, e01664;
  4. A complete study on an asphalt concrete modified with Graphene and recycled hard-plastics: A case study. Case Studies in Construction Materials. 2022, 17, e01437;
  5. Effect of Graphene Oxide on Aging Properties of polyurethane-SBS Modified Asphalt and Asphalt Mixture. Polymers 2022, 14, 3496;
  6. Mechanical Characteristics of Graphene Nanoplatelets-Modified Asphalt Mixes: A Comparison with Polymer- and Not-Modified Asphalt Mixes. Materials 2021, 14, 2434;
  7. Impact of Graphene Oxide on Zero Shear Viscosity, Fatigue Life and Low-Temperature Properties of Asphalt Binder. Materials 2021, 14, 3073;
  8. Experimental Investigation into the Structural and Functional Performance of Graphene Nano-Platelet (GNP)-Doped Asphalt. Appl. Sci. 2019, 9, 686;
  9. Modified Asphalt with Graphene-Enhanced Polymeric Compound: A Case Study. Infrastructures 2024, 9, 39.

Glass and Carbon Fiber Composites Enhancement

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Glass and Carbon Fiber Composites Enhancement:

Improving Properties with Graphene Nanoparticles

Glass and carbon fibers, thanks to their excellent properties, are widely used in industries such as aerospace, maritime, automotive, sports, construction, and even in the manufacturing of fundamental components for renewable energies such as wind power. However, despite their excellent performance, they often exhibit a phenomenon known as “interlaminar delamination” due to weak fiber/resin interfacial interaction, which can compromise the product’s lifespan and safety due to their significant role in stress transfer between both elements. As this interaction is key to the long-term success of composite structures, various improvement alternatives have been explored, such as Z-pinning, stitching, and braiding; increasing the surface area and reactivity of fibers through surface modifications such as plasma treatment, thermal modification, or chemical functionalization, which are complex, costly processes that are not always efficient and tend to reduce the laminate’s in-plane performance.

“As an additional strategy of relatively recent emergence, the incorporation of nanoparticles into fiber composite materials was proposed to favor interaction with the embedding matrix.”

Graphene, the nanomaterial known as the cornerstone of the carbon family and which since its isolation has been described as “the material of the future” or “the miracle material,” is an attractive candidate as a nanoreinforcement for countless polymeric compounds due to its unique graphitized flat structure, which leads to better mechanical, thermal, and other properties that, unlike other nanoparticles such as carbon nanotubes (CNTs), do not significantly increase resin viscosity and therefore allow higher concentrations to be incorporated, favoring the aforementioned fiber/matrix interaction.

Research on the effects of graphene for the design of hybrid materials based on fibers (glass/carbon) embedded in a commonly epoxy-based polymeric matrix has highlighted greater compound stiffness, improvements in fracture resistance, better lubrication, and even improved electrical conductivity. This is because its large surface area allows effective load transmission from the soft polymer matrix to the relatively stiffer graphene sheets, which is an essential requirement for improving mechanical performance, confirmed by increased interlaminar shear strength of the material, greater tensile and impact strength. Additionally, during the manipulation and cutting of hybrid fiber structures, the presence of graphene contributes to generating less heat during milling, leading to lower cutting temperatures and smoother surface roughness; likewise, another benefit is that graphene produces a greater hardening effect and better bending resistance of the material exposed to different temperatures ranging from 40 °C to 200 °C.

At Energeia-Graphenemex, the leading company in Latin America in the production of graphene materials and in the development of applications, we are convinced that graphene’s extraordinary capabilities as a nanoreinforcement for countless three-dimensional matrices will continue to encourage researchers and industrial colleagues to explore its benefits for the manufacture of stronger and lighter structural components for aircraft such as fuselage and wings; automotive parts and aerodynamic bodywork; wind turbines, sports equipment, construction materials, among others.

Draft: EF/DH

References:

  1. Effect of dispersion of alumina nanoparticles and graphene nanoplatelets on microstructural and mechanical characteristics of hybrid carbon/glass fibers reinforced polymer composite. Journal of material research and technology. 2021, 14, 2624;
  2. Experimental investigation on the properties of glass fiber-reinforced polymer composites containing Graphene. AIP Conf. Proc. 2022, 2405, 050009;
  3. Reinforcement effect of graphene oxide in glass fibre/epoxy composites at in-situ elevated temperature environments: An emphasis on graphene oxide content. Composites part A: Applied science and manufacturing. 2017, 95, 40;
  4. Preparation and Mechanical Properties of Graphene/Carbon Fiber-Reinforced Hierarchical Polymer Composites. J. compos sci. 2019, 3, 30;
  5. Improving fiber/matrix interfacial strength through graphene and graphene-oxide nano platelets. IOP Conf. Ser.: Mater. Sci. Eng. 2016, 139, 012004;
  6. Effect of Graphene on Machinability of Glass Fiber Reinforced Polymer (GFRP). J. Manuf. Mater. Process. 2019, 3, 78;
  7. Size effect of graphene nanoplatelets on the morphology and mechanical behavior of glass fiber/epoxy composites. J Mater Sci. 2016, 51, 3337.

Tapping into Graphene’s Potential:

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Tapping into Graphene’s Potential:

Enhancing Coatings with Nanotechnology for Weather Resistance

Coatings are designed for decorative purposes and to protect surfaces, especially against corrosion and moisture. In a coating system (multilayer), the top or finishing layer plays a crucial role as it must provide a good appearance and protect the inner layers and the substrate against environmental factors such as sunlight, humidity, corrosion, chemical resistance, soiling, etc., throughout its lifespan.

Today, Polyurethane (PU) is considered one of the coatings with the best physical-chemical characteristics for finishing coating applications and for its weather resistance. However, its weather resistance decreases with exposure to ultraviolet light over long periods.

Sunlight is one of the main causes of damage to coatings. Damage ranges from loss of physical properties, powdering (chalking), cracking, peeling, discoloration, and color change, because of chemical photodegradation, migration, evaporation, and interaction of other components with the coating.

In recent years, various nanostructured materials such as titanium, zinc oxide, cerium, and iron oxide have been implemented to improve the weather resistance of polymeric coatings. The mechanism is based on their projection effect (both absorption and dispersion) of incident rays in the UV region. These materials can stabilize coatings against exterior exposure, possess photocatalytic activity that can destroy the organic binder material present in coatings, leading to modifying the surface of these nanostructured materials to eliminate or inhibit their photocatalytic activity, requiring more processes, time, and money.

Recently, graphene has attracted much attention as a new additive and material for producing coatings to enhance anticorrosive, antimicrobial, and weather-resistant properties, due to its special electronic structure that provides unique electrical, mechanical, and chemical properties. Graphene is a nanomaterial formed by one or more layers of carbon (formed by carbon atoms bonded hexagonally with a thickness of one carbon atom). This structure enables graphene-based materials to absorb photons in the UV region. This UV absorption capacity, as well as the absence of photocatalytic activity of graphene materials, allows introducing these materials as new additives for the photo-stabilization of polymeric coatings, i.e., with greater resistance to UV radiation

Currently, Energeia – Graphenemex®, is in constant development of nanotechnological coatings with better properties. Studies have been conducted on the influence of graphene oxide on the weathering behavior of PU coatings. To evaluate the performance of graphene oxide, a PU coating with graphene oxide (PU/GO) was compared with a PU coating containing a commercial organic UV absorber (PU/control).

Color change in a coating during exposure to weathering (sunlight) is the most important and rapid parameter to visually evaluate coating degradation. To evaluate, color change, samples coated with Polyurethane with and without graphene material were introduced into an accelerated weathering chamber (based on ASTM G154). According to the standard, a QUV weathering chamber model QUV/se was used to accelerate weathering conditions. Coated samples were cyclically exposed to UVA radiation (energy 0.89 W/m2) for 8 hours, followed by moisture condensation for 4 hours at 50 °C. The color of the coatings was evaluated before exposure to compare their initial color, and subsequently evaluated at different exposure times, this evaluation was performed until reaching an exposure time of 1200 hours.

The main component of color typically considered in weathering behavior is the total color change or Delta E (ΔE). Fig. 1 shows the ΔE, as the most comprehensive criterion of color changes, which is the sum of changes in all color components.

As can be seen, most of the color variations throughout the exposure time belong to the PU/control coating. The sample containing graphene oxide (PU/GO) at 251 hours of exposure time shows a lower color change compared to PU/control. With the increase in exposure time in the weathering chamber, color variations can be observed, but the sample with graphene oxide continues to show lower color changes, indicating that the incorporation of GO in Polyurethane provides more resistance and maintains its stability for longer exposure times to weathering.

Fig 1. Total color change (ΔE) versus exposure time for Polyurethane coatings with graphene oxide (PU/GO) and without graphene oxide (PU/control) during accelerated weathering test.

From a physical point of view, graphene oxide (GO) has higher transmittance in the visible region compared to graphene, which is more favorable for its use as a UV protector in finishing coatings. On the other hand, thanks to the high surface area of graphene materials, they can also provide excellent barrier effect properties and thus develop anticorrosive coatings with greater weather resistance.

Energeia – Graphenemex®, through its Graphenergy line, offers a wide range of nanotechnological coatings with graphene. These coatings offer high anticorrosive and antimicrobial protection. In addition to providing high wear resistance, UV resistance, impermeability, and extraordinary adhesion, with the aim of improving the life of any surface or installation and reducing maintenance costs.

References

  1. G. Wang, X. Shen, B. Wang, J. Yao, J. Park, Synthesis and characterisation of hydrophilic and organophilic graphene nanosheets, Carbon N. Y. 47 (no. 5) (2009) 1359–1364.
  2. B. Ramezanzadeh, M. Mohseni, H. Yari, S. Sabbaghian, A study of thermal-mechanical properties of an automotive coating exposed to natural and simulated bird droppings, J. Therm. Anal. Calorim. 102 (no. 1) (2010).
  3. N. Rajagopalan, A.S. Khanna, Effect of Methyltrimethoxy Silane Modification on Yellowing of Epoxy Coating on UV (B) Exposure vol. 2014, (2014).
  4. M. Hasani, M. Mahdavian, H. Yari⁎, B. Ramezanzadeh. Versatile protection of exterior coatings by the aid of graphene oxide nanosheets; comparison with conventional UV absorbers. 2017.
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  6. Weathering performance of the polyurethane nanocomposite coatings containing silane treated TiO2 nanoparticles, Appl. Surf. Sci. 257 (no. 9) (2011) 4196–4203.
  7. N.S. Allen, M. Edge, A. Ortega, C.M. Liauw, J. Stratton, R.B. McIntyre, Behaviour of nanoparticle (ultrafine) titanium dioxide pigments and stabilisers on the photooxidative stability of water based acrylic and isocyanate based acrylic coatings, Polym. Degrad. Stab. 78 (no. 3) (2002) 467–478.
  8. Effect of Silane Modified Nano ZnO on UV Degradation of Polyurethane Coatings. vol. 79, (2015), pp. 68–74.
  9. M. Rashvand, Z. Ranjbar, S. Rastegar, Nano zinc oxide as a UV-stabilizer for aromatic polyurethane coatings, Prog. Org. Coatings 71 (4) (Aug. 2011) 362–368.

Defying the flames

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Defying the flames:

The triumph of graphene oxide in the creation of fire-fighting coatings

The inclusion of Graphene Oxide (GO) in coatings demonstrates effectiveness in inhibiting flammability, providing a fire-resistant barrier. Benefits include anti-corrosion protection, antimicrobial properties and increased adhesion to substrates. This advance highlights Energeia-Graphenemex’s innovation in the production of fireproof coatings, positioning itself as a leader in the research and application of high-quality graphene materials.

Coatings are used in various sectors, at an industrial level the use of coatings are focused on protection against corrosion, while at a commercial level they are used for infrastructure maintenance and for decorative purposes. Today, the coatings industry continues to constantly research the development of improved coatings, with antimicrobial, non-stick properties, and greater resistance to chemical attack and weathering. However, at a commercial level there are few developments focused on fireproof coatings (flame retardant) for fire protection in infrastructure.

Traditional fireproof coatings are cementitious coatings, based on Portland cement, magnesium oxychloride cement, vermiculite, gypsum and other minerals. In addition, they contain fibrous fillers, binders, supplements and additives that control density and rheology, these materials are generally mixed with water on site and applied by spraying some construction or can be applied to a flammable substrate by using a roller, in thicknesses of half an inch or more. However, due to their weight, thickness and poor aesthetics, they limit architectural design.

In coatings and paint industry, there is a wide variety of coatings based on different types of resins (polymers) and additives. Due to their nature, most of these coatings are flammable and combustible materials. That is, they are materials that can catch fire when exposed to fire, suffering degradation and the release of heat to subsequently initiate the spread of the flame, releasing smoke and toxic gases, being a danger to the safety of human life and property. On the other hand, polymer-based fireproof coatings use conventional additives based on halogens (bromine and chlorine), as well as phosphorus, melamine and inorganic compounds, to improve the fire resistance of the coatings, however, these materials are toxic to humans and the environment.

In recent years, Energeia-Graphenemex has focused on the production of graphene materials. Graphene is the most revolutionary nanotechnological additive for the coatings and paints industry, as it allows the development of coatings with extraordinary anti-corrosion protection, coatings with antimicrobial properties, coatings with better adhesion to substrates and greater resistance to UV radiation. In this sense, graphene oxide (GO) has been shown to be a new additive that helps inhibit or reduce the flammability of coatings, to produce effective fireproof coatings.

Its efficiency is associated with the fact that GO has a strong barrier effect, high thermal stability and great surface absorption capacity that are favorable for effectively reducing heat and mass transfer.

The incorporation of GO in coatings can improve flame resistance, by inhibiting the two key terms: heat and fuel. That is, it can function as a flame retardant in the following ways:

• GO possesses a unique two-dimensional layer structure and can promote the formation of a dense continuous layer of carbon during the combustion process (see Fig. 1). Carbon can act as a physical barrier to prevent heat transfer from the heat source and delay the escape of products (pyrolysis) from the coating.

• Because GO has a large surface area, it can effectively adsorb flammable volatile organic compounds or hinder their release and diffusion during combustion.

• The presence of oxygenated groups in the GO structure means that, during the combustion of the coating, the oxygen-containing groups in GO can undergo decomposition and dehydration at low temperature, thus absorbing heat and cooling the polymeric substrate during combustion. Meanwhile, gases generated by dehydration can dilute the oxygen concentration around the ignition periphery, decreasing the risk of fire spread.

In summary, the incorporation of GO in coatings can provide fire protection, because they can release water and provide thermal insulation effects.

Graphene-based flame-retardant coatings are designed to retard ignition and burn rate, and must provide a fire-resistant barrier.

Energeia – Graphenemex®, Mexican company, leader in Latin America in research and production of graphene materials for the development of industrial applications. It has extensive experience in the large-scale production of graphene oxide (GO) and has high-quality graphene materials for sale for use in different industries.

Fig.1 Flame retardancy test of coatings (Method based on UL-94 classification), where;
a) coating without GO and b) Coating with GO.

References

  1. Sachin Sharma Ashok Kumar, Shahid Bashir, K. Ramesh, S. Ramesh, Progress in Organic Coatings, 154, (2021)
  2. Weil, Edward. D. Fire-Protective and Flame-Retardant Coatings – A State-of-the-Art Review. Journal of Fire Sciences, 29(3), 259–296.
  3. Lipiäinen, H., Chen, Q., Larismaa, J., & Hannula, S. P. (2016). The Effect of Fire Retardants on the Fire Resistance of Unsaturated Polyester Resin Coating. Key Engineering Materials, 674, 277–282.
  4. Md Julker Nine, Dusan Losic. Mahmood Aliofkhazraei, Nasar Ali, Mircea Chipara, Nadhira Bensaada Laidani, Jeff Th.M. De Hosson, Handbook of Modern Coating Technologies, Elsevier, 2021, Pages 453-492.

Reinforced Concrete

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Reinforced Concrete:

Why Choose Fibers with Graphene Oxide?

Fiber reinforced concrete is an improved version of conventional concrete characterized by better performance against cracking, deformation, fatigue and impact. It is widely used for the manufacture of industrial and commercial floors, tunnels, slopes, tanks, shotcrete, prefabricated and in some cases as a replacement for the electrowelded mesh of floors, but not as a substitute for the reinforcing steel of structural columns, load-bearing walls. or suspended beams. Unlike concrete reinforced with steel structures, fibers represent a discontinuous and homogeneous three-dimensional reinforcement within the concrete mixture that allows it to have the same characteristics at each point of the structure.

Of the extensive classification of fibers in terms of materials, lengths, thicknesses and geometries, the main competition is between steel fibers and polypropylene fibers, because both materials increase the toughness of concrete and allow it to continue absorbing loads before collapse. The difference is that steel fibers control cracking during the setting of the concrete and after hardening, they have great tensile strength and do not deform, but rather absorb energy and transform it into an internal stress; characteristics that make them very useful for use in concrete exposed to high loads. Polypropylene fibers contribute to the control of cracks due to plastic contraction, external loads, temperature, or drying contraction and, although its tensile strength is lower than steel, its deformation capacity allows it to absorb large loads without failing. They are less expensive, easier to handle and are generally indicated for lower load concretes.

Although the mechanical properties of steel fibers are superior to those of polypropylene and subject to the characteristics of the project and the applicable regulations, there are other technical differences that are worth considering when selecting:

Durability- The steel fibers within the concrete usually remain stable and isolated from the external environment, however, when this insulation is broken either by capillarity, microcracking or by a change in the pH of the concrete, the fibers become susceptible to corrosion, whose oxidation in the future will be responsible for the loss of adhesion with the concrete. The advantage of polypropylene fibers is that they are suitable for placement in humid and marine environments thanks to their chemical stability, resistance to corrosion and degradation.

Volumetric weight- The amount of polypropylene fibers per kilogram of weight is greater than those contained in one kilogram of steel fibers. This means that, to have a similar distribution, approximately between 5 and 8 kg of metallic fibers should be dosed for each kilogram of polypropylene fibers and, although the volumetric weight can be considered irrelevant for performance, the cost and handling of the product can be two interesting variables.

Adhesion – The adhesion or interfacial bond between the fiber and the concrete is essential for the long-term success of the structure and is quantified as the force necessary for the fiber to be torn from the concrete matrix or undergo rupture. In steel fibers, their adhesion depends mainly on their morphology and length; however, polypropylene fibers, in addition to facilitating the manufacture of different configurations, can also be chemically modified to improve their adhesion.

Distribution- Depending on the quantity dosed, steel fibers can form “hedgehogs” or leave spikes on surfaces, posing risks during handling and after placement. A disadvantage of polypropylene fibers is their hydrophobicity or incompatibility with water, this means that when the mechanical mixing of the fibers is carried out within the concrete composed of water, cement and aggregates, they can agglomerate and cause clumps, especially at dosages. elevated; Consequently, poor distribution, aggregation or formation of air spaces within the concrete will have a negative impact on its adhesion and, therefore, its performance.

Fire resistance – In the event of a fire, concrete can exhibit explosive detachment or “spalling” behavior, which consists of the violent expulsion of fragments due to the increase in pressure exerted by the release of water vapor until detachment occurs when the pressure exceeds the tensile strength of the concrete. Polypropylene microfibers melt at temperatures between 160 and 170° C, therefore creating interconnected channels that increase the permeability of the concrete and help release moisture and internal pressure.

The Mexican company Energeia-Graphenemex®, through its Graphenergy Construction division, takes advantage of the benefits of graphene nanotechnology to improve the characteristics of conventional polypropylene fibers; Its specialized formula allows obtaining individual filaments with greater mechanical and thermal resistance, better distribution and greater adhesion within the concrete compared to common fibers.

How does graphene oxide improve the performance of polymer fibers?

Graphene oxide is one of the most interesting materials to improve the characteristics of many polymers. It consists of sheets of graphene or pure carbon stabilized with oxygenated groups that make it a multifaceted structure, compatible with water, like cement crystals and easily combinable with other compounds to design materials with new or improved properties, for example:

Distribution within the concrete mix
One of the advantages of graphene oxide designed for the manufacture of polypropylene fibers is its surface chemistry consisting mainly of oxygenated groups (OH- and COOH-) that help maintain the affinity of the fibers with the aqueous elements of the graphene paste. cement acting in a similar way to plasticizing additives, this is because graphene oxide reduces the surface energy of the fibers, facilitating their distribution within the mixture and avoiding aggregates.

Adherence
Another benefit of graphene oxide present in polypropylene fibers is the electrostatic repulsion that it generates between the cement particles; This phenomenon prevents cement agglomeration and increases the degree of fiber-cement interaction by altering the hydration products and increasing their degree of polymerization. In hardened concrete, this effect increases the coefficient of friction so that when a crack displaces a fiber, more load will be required to displace it within the concrete.

Mechanical strength
Graphene oxide increases the tensile and breaking strength of polymers, this is because its elastic modulus (230 GPa) is slightly higher than that of steel and its alloys (190-214 GPa), but comparable to of Zirconia (160-241 GPa) and Cobalt alloys (200-248 GPa), therefore, fibers with graphene oxide have a lower risk of fracture and are more durable than common fibers

Degradation resistance
Polymeric fibers with graphene oxide have a longer useful life because it is a material that differs from many others that deteriorate because of UV radiation, graphene oxide maintains its structural integrity and mechanical properties, in addition, it is chemically inert. and more resistant to corrosive media.

Thermal stability
Graphene oxide increases the thermal stability of polypropylene by forming interconnected bridges or pathways throughout the polymer matrix, improving heat transport.

Drafting: EF/DH

Sources

  1. Fabrication of graphene oxide/fiber reinforced polymer cement mortar with remarkable repair and bonding properties.             J. Mater. Res. Technol. 2023; 24: 9413;
  2. The incorporation of graphene to enhance mechanical properties of polypropylene self-reinforced polymer composites J. Wang et al. / Materials and Design 195 (2020) 109073;
  3. Simultaneous enhancement on thermal and mechanical properties of polypropylene composites filled with graphite platelets and graphene sheets. Composites Part A 112 (2018);
  4. Experimental study on the properties improvement of hybrid Graphene oxide fiber-reinforced composite concrete. Diamond & Related Materials 124 (2022) 108883.
  5. Upcycling waste mask PP microfibers in portland cement paste: Surface treatment by graphene oxide. Materials Letters 318 (2022) 132238;
  6. An Experimental Study on the Effect of Nanomaterials and Fibers on the Mechanical Properties of Polymer Composites. Buildings 2022, 12,
  7. State-of-the-Art Review of Capabilities and Limitations of Polymer and Glass Fibers Used for Fiber-Reinforced Concrete. Materials 2021, 14, 409;
  8. Mecanismos de desprendimiento explosivo del hormigón bajo fuego y el efecto de las fibras de polipropileno. Estado del conocimiento. Asociación argentina de tecnología del hormigón. Revista Hormigón 62 (2022-2023) 25

Polymeric Graphene Oxide Fibers

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Polymeric Graphene Oxide Fibers:

an effective solution to prevent cracking in Concrete

Globally, concrete is the most used construction material. Concrete is applied in different infrastructures, including buildings, bridges, dams and tunnels, due to its high compressive strength. However, concrete has some limitations and problems, such as low tensile strength and cracking. Cracks or fissures can appear during the production of concrete and at subsequent stages. They begin as nanoscale cracks, later they join together forming micro and macro cracks. This behavior is closely associated with the hydration process that cement undergoes, where it releases heat and increases the temperature of the concrete. In large structures, heat cannot be released easily, causing expansion stresses, and thermal contraction, leading to cracking.

Because concrete is constantly exposed to impact, fatigue and other types of loads, cracks or fissures, and irreparable failures can occur, it is why it is common to reinforce it with polymer fibers to improve the physical-mechanical characteristics of concrete.

Incorporating fibers into concrete has proven to be effective in delaying or preventing crack propagation. At a commercial level, there is a wide range of polymeric fibers as three-dimensional secondary reinforcement of concrete and mortar, with different lengths and sizes (macrofibers and microfibers). These polymer fibers are made from materials such as polypropylene (PP), high-density polyethylene (HDPE), PVA and polyester.

However, there are some disadvantages or limitations of commercial polymer fibers, the hydrophobic nature of polymer fibers, or/and its elastic modulus is insufficient, so the incorporation of polymer fibers in concrete only slightly improves the resistance to the tension. Furthermore, the little improvement in tensile strength is mainly attributed to insufficient bond strength at the interface between the fiber and matrix, i.e., low compatibility (no adequate anchorage) of the fiber with the concrete. So the fibers easily detach from the concrete, increasing the risk of cracking and failure in the concrete. (See Figure 1)

Figure 1. Differences between commercial polymer fibers (a) and metallic fibers (b) in concrete.

Currently Energeia Fusión- Graphenemex, under its Graphenergy Construction line, developed polymeric macrofibers with graphene oxide (GO). Graphene oxide is a nanomaterial, which due to its unique physical and chemical characteristics, such as its large surface area (736.6 m2/g), extraordinary mechanical properties (25 GPa), thermal properties and its unique structure with multiple oxygen-containing groups on its surface, makes GO an ideal material for modifying the surface of polymer fibers. These characteristics allow improving the interface or compatibility of the fibers with cementitious materials and/or concrete.

The oxygenated groups of GO act as anchoring sites for the formation of cement hydration products, improving the interface between the fibers and the cementitious matrix (See Figure 2). Consequently, a stronger interface leads to an improvement in the tensile strength of the concrete.

Figure 2. Scanning Electron Microcopy (SEM) analysis of fibers torn from concrete. PVA fiber (a and b).
PVA/GO fiber (e and f). Taken from [Ref. 2]

When a concrete structure is subjected to loading, tension and compression stresses begin to build up. Over time, small cracks appear in places where the stress reaches a critical point. In this sense, the Graphenergy reinforcing fibers remain solidly anchored in the concrete matrix and absorb the tensile stress at any point and direction.

If there is a small crack the fibers are held firmly within the concrete, as the tension increases the fiber slowly elongates (deforms) until it reaches its maximum strength. With a 38% improvement in tensile strength and 29% more elongation than commercial reinforcement, concrete structures reinforced with Graphenergy fibers can withstand high bending stress over a long period. These nanotechnology fibers delay the appearance of the first crack and slow down the spread of cracks in the concrete.

The main difference between Graphenergy reinforcing fibers and other commercial fibers is that fibers with graphene become part of the concrete matrix and give rise to a composite material. Graphenergy reinforcing fibers form a reinforcing network throughout the structure, reducing or inhibiting the appearance of cracks (effective crack control), and improve the ductility of concrete. Additionally, Graphenergy reinforcing fibers improve concrete quality, providing greater shrinkage resistance, fire resistance and greater impermeability in concrete.

References

  1. Filho, A., Parveen, S., Rana, S., Vanderlei, R., & Fangueiro, R. (2020). Mechanical and micro-structural investigation of multi-scale cementitious composites developed using sisal fibres and microcrystalline cellulose. Industrial Crops and Products, 158, 112912.
  2. Yao, X., Shamsaei, E., Chen, S., Zhang, Q. H., de Souza, F. B., Sagoe-Crentsil, K., & Duan, W. (2019). Graphene oxide-coated Poly(vinyl alcohol) fibers for enhanced fiber-reinforced cementitious composites. Composites Part B: Engineering, 107010.
  3. Lingbo Yu, Shuai Bai, Xinchun Guan, Effect of multi-scale reinforcement on fracture property of ultra-high performance concrete, Construction and Building Materials, Volume 397, 2023, 132383, ISSN 0950-0618.
  4. Chen Lin, Terje Kanstad, Stefan Jacobsen, Guomin Ji, Bonding property between fiber and cementitious matrix: A critical review, Construction and Building Materials, Volume 378, 2023, 131169, ISSN 0950-0618.
  5. Bolat, H., Şimşek, O., Çullu, M., Durmuş, G., & Can, Ö. (2014). The effects of macro synthetic fiber reinforcement use on physical and mechanical properties of concrete. Composites Part B: Engineering, 61, 191–198.