Category: Graphene Oxide

Graphene Oxide, the nanomaterial that will reduce the impact of corrosion

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Graphene Oxide

the nanomaterial that will reduce the impact of corrosion

What is corrosion?

The term corrosion refers to the destruction of a material because of its chemical or electrochemical interactions with the surrounding medium. The importance of its prevention and/or control is due to the fact that, being a natural phenomenon, once started it is practically impossible to stop. Therefore, an uncontrolled evolution will invariably compromise the integrity and useful life of the materials, generating the industry involved direct and indirect expenses due to loss of product, stoppage of activities due to maintenance until the replacement of machinery or structures.

“Economic losses caused by corrosion exceed 3.4% of global GDP”

Microbiologically influenced corrosion

Microbiologically influenced corrosion (MIC) can be defined as the electrochemical process in which microorganisms such as algae, fungi and bacteria initiate, facilitate, or accelerate a corrosion reaction, generally located in the form of cracks. or pitting on both metal and concrete surfaces. Although corrosion involves various variables, it is estimated that MIC participates in 20 to 40% of all corrosion failures, particularly in hydraulic and oil infrastructure, with costs close to 2 billion dollars annually.

Why do you start the MIC?

The presence of humidity in any environment is the ideal habitat for the growth of numerous communities of microorganisms that, combined with optimal conditions of temperature, pH, nutrient flow, etc., promotes their adhesion and growth on surfaces, forming a biofilm that is not removed, it grows into a hardened, obstructive biomass within which sulfate-reducing bacteria, acid-producing bacteria, iron-reducing bacteria, and gel-forming bacteria promote corrosion or MIC through destructive electrochemical reactions of the surfaces.

How do you combat it?

There are three most common methods to try to combat MIC, the first is mechanical cleaning of surfaces to remove biofilms, ideally in incipient stages, however, it is not always possible to access all exposed areas, making their efficiency difficult. The second is the use of biocidal agents that, in addition to being expensive, most may not be friendly to human health and the environment. Finally, and perhaps the most suitable method is the placement of external barriers in the form of coatings or polymeric films to prevent direct contact of the metal or concrete structures with the aggressive medium.

Corrosion control in concrete

The options available to protect concrete against corrosion from its fresh state are the additions of pozzolanic materials, fly ash, blast furnace slag, sulfate-free aggregates, polymer fibers, use of sulfate-resistant cement or modified with nanoparticles such as nanotubes and carbon nanofibers, silica nanoparticles, alumina or titanium dioxide. For protection in the hardened state, it is common to apply physical barriers such as anti-corrosion coatings or polymeric films and, for the protection of metal structures, in addition to anti-corrosion coatings, you can use galvanized, tinned structures or the placement of magnesium sacrificial anodes. However, it is considered that, due to the natural porosity of concrete, there are no totally efficient methods that attack the problem of corrosion towards the interior of structures.

Corrosion in concrete can occur due to carbonation, ingress of chlorides and sulfates or due to microbiological attack. When the concrete has reinforcing steel and is attacked by corrosion, oxide can grow 2 to 4 times the volume of the original steel, causing loss of adhesion of concrete and put the resistance of the material at risk. Furthermore, the porosity of the concrete, in addition to allowing the passage of moisture for the entry of aggressive ions, also offers millions of ideal niches for the retention of microorganisms and for the subsequent formation of MIC-initiating biofilms, not only because they favor their anchoring, but because they make their removal difficult and promote the advancement of corrosion.

“It is expected that by 2032 the corrosion inhibitors market will amount to 12.5 billion, and in 2022 this figure will be around 8.3 billion.”

Graphene and graphene oxide are multifunctional carbon nanomaterials with extraordinary properties that, when incorporated as a nanofiller in other compounds such as coatings, plastics or cement, have the ability to molecularly organize their structure in such a way that they improve their resistance to chemical, physical and microbiological attacks. Among their particularities is that they are inert nanostructures, that is, they are stable, they do not react with other materials and they do not suffer oxidation or corrosion. They are extremely thin and light, but at the same time, very resistant and flexible. They are impermeable even to gases and have highly efficient antimicrobial mechanisms.

Below is a summary of some of the most notable research on the use of graphene as an alternative against microbiologically influenced corrosion (MIC):

2015- The Department of Materials Science and Engineering at Rensselaer Polytechnic Institute, New York, USA, modified polyurethane coatings with graphene identifying 10 times greater protection against MIC compared to unmodified polyurethane coatings.

2017- The Nanobiomaterials laboratory of the Federico Santa María Technical University, Valparaíso, Chile, evaluated the direct effect of graphene placed on nickel substrates and its interaction with bacteria that cause corrosion. The results showed an impermeable barrier generated by graphene that blocked the interaction between bacteria and the metal, but without a bactericidal effect.

2021- The Department of Civil and Environmental Engineering, South Dakota School of Mines and Technology, USA, reported that multiple layers of graphene restricted MIC attack on copper and nickel surfaces 10 times more.

2021– The School of Engineering at the University of Glasgow, Scotland, examined the deterioration of graphene oxide (GO)-modified cement pastes exposed to acidic environments. The results demonstrated that the presence of GO reduces the loss of mass in the concrete due to these attacks, recognizing it as a potential additive to modify the microstructure and useful life of concrete in the face of aggressive environments such as those present in chemical product warehouses to systems. of wastewater.

Energeia Fusion (Graphenemex®), the leading Mexican company in Latin America in the production of graphene materials, after a long journey of research, in 2018 launched the Graphenergy Line on the market, which includes a series of anticorrosive and antimicrobial coatings with graphene nanotechnology and the first additive for concrete with graphene oxide in the world, whose individual or combined use promises great benefits against corrosion.

Graphenergy Construction is a water-based additive with graphene oxide designed to improve the quality of cement structures in terms of mechanical resistance and durability. The added value that graphene oxide offers to concrete in the fight against MIC from the outside to the inside is the result of a series of events that begin by favoring the hydration of the cement, acting as water reservoirs and as a platform for the growth of crystals. of C-S-H and to dissipate the heat of hydration; improves the interfacial transition zones between the cement paste and the aggregates, helping to reduce the size and volume of the pores, this in turn favors an increase in mechanical resistance, reduces permeability, increases its resistivity, that is, reduces the transfer of electrical charges into the interior of the concrete, delaying the onset of corrosion and, finally, modifying the electrostatic charges and the wettability of the surfaces, making the formation of biofilms that cause MIC difficult.

Graphenergy coatings formulated with graphene oxide offer great resistance against corrosion in coastal and non-coastal areas, as well as excellent antimicrobial protection without biocidal mechanisms, since their effect consists of preventing the adhesion of microorganisms to surfaces. In addition, its impermeability, resistance to abrasion and resistance against the intense effects of the elements increase its useful life and, therefore, substantially reduce the maintenance costs of both metal and concrete structures.

Drafting:  EF/DH

References

  1. The Many Faces of Graphene as Protection Barrier. Performance under Microbial Corrosion and Ni Allergy Conditions. Materials 2017, 10, 1406;
  2. Effect of graphene oxide on the deterioration of cement pastes exposed to citric and sulfuric acids. Cement and Concrete Composites, 2021, 124, 104252;
  3. Superiority of Graphene over Polymer Coatings for Prevention of Microbially Induced Corrosion. Scientific Reports, 2015, 5:13858;
  4. Atomic Layers of Graphene for Microbial Corrosion PreventionACS Nano 2021, 15, 1, 447;
  5. Microbiologically induced corrosion of concrete in sewer structures: A review of the mechanisms and phenomena. Construction and Building Materials. 2020, 239, 117813;
  6. Microbiologically Induced Corrosion of Concrete and Protective Coatings in Gravity Sewers. Chinese Journal of Chemical Engineering, 2012, 20(3) 433;
  7. In situ Linkage of Fungal and Bacterial Proliferation to Microbiologically Influenced Corrosion in B20 Biodiesel Storage Tanks. Front. Microbiol. 2020, 11;
  8. Chapter 1 – Failure of the metallic structures due to microbiologically induced corrosion and the techniques for protection. Handbook of Materials Failure Analysis. With Case Studies from the Construction Industries. 2018, 1;
  9. Maleic anhydride-functionalized graphene nanofillers render epoxy coatings highly resistant to corrosion and microbial attack. Carbon, 2020, 159, 586;
  10. Gerhardus Koch, Cost of corrosion, In Woodhead Publishing Series in Energy, Trends in Oil and Gas Corrosion Research and Technologies, Woodhead Publishing, 2017;
  11. https://www.futuremarketinsights.com/reports/corrosion-inhibitors-market.
  12. http://www.imcyc.com/revistacyt/oct11/artingenieria.html

Innovation in the construction industry

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Innovation in the construction industry:

graphene oxide as an adjuvant to improve the resistance and durability of pavement

Concrete, due to its production efficiency, abundant sources of raw material, workability, and versatility, is a widely used material in the construction industry; among its numerous applications are rigid pavements for highways, airports, industrial floors and bridges, however, and despite its excellent resistance to compression, concrete presents limitations such as low tensile and flexural resistance that, together with factors such as overloads or environmental conditions, it usually develops failures such as cracking, perforations, detachment or erosion that will invariably require repair. Therefore, improving its quality, in addition to increasing its useful life and reducing risks, also allows maintenance work to be reduced or spaced out and, consequently, avoids the stoppage of operations or road closures, in turn representing significant economic savings.

In addition to quality and economy, another of the objectives of the construction industry is to reduce the carbon footprint, taking as a reference that the main concrete binder is cement and that, for each ton of cement manufactured, 1 ton of carbon is released. CO2 into the atmosphere. That is why there is a constant search for technologies and/or materials that improve or equalize the performance of concrete, in principle using a lower cement content through the use of cement substitutes such as mineral microparticles, an industrial waste product for example: fly ash, blast furnace slag or silica fume; reinforcements with steel, synthetic or glass fibers; resins and recycled materials such as tire rubber, polypropylene, PET or recycled concrete itself, as well as a wide variety of lignosulfonate, naphthalene sulfonate, melamine or polycarboxylate-based additives to provide plasticizing, water-reducing, setting accelerator or retardant functions, among other.

A valuable tool to add value in the triad: quality, economy and the environment, is nanotechnology, based on the premise that cement is mostly made up of C-S-H nanocrystals, responsible for the cohesive properties, hardening and, in definitively, of its mechanical resistance. This means that manipulating and modifying the structure of the cement from its nano level brings benefits at the macro level, that is, in the concrete as a finished product.

Throughout the last ten years of research and application of nanotechnology in construction, Graphene Oxide (GO) appeared on the scene, a carbon nanoparticle derived from graphite with excellent mechanical, thermal and barrier properties; Its good dispersion in water and great affinity for cement nanoparticles have shown interesting attributes to accelerate cement hydration, increase the production of C-S-H nanocrystals and reduce cement pores, which together represent important benefits in strength, durability and variety of infrastructure applications. Likewise, it has been shown that the manufacture of polymeric fibers for concrete modified with GO contributes to significantly improve its resistance to tension, impact, and abrasion, delays its deterioration due to corrosion or UV radiation and makes it more thermally stable, reduces cracking, among other benefits.

Derived from the great potential of this nanomaterial for the construction industry, in 2022 Sustainability magazine used the Web of Science (WoS) database to carry out an analysis of the research generated in the period 2010-2022 regarding the use of carbon dioxide. graphene in cement compounds. In this study, a total of 608 publications related to mechanical resistance, durability, thermal conductivity, among others, were identified, but only less than 10 journals made reference to the comprehensive benefits that GO offers to rigid pavements, either individually or as a three-dimensional reinforcement through the use of polymeric fibers, which represents a little explored application, but with large areas of opportunity.

Tomado de: Sustainability 2022, 14, 11282.

Energeia – Graphenemex®, the leading Mexican company in Latin America in research and production of graphene materials for the development of applications at an industrial level, through its Graphenergy Construction® product line in 2018, placed an additive on the market for the first time for concrete with graphene oxide that contributes to improve the microstructure of cement-based conglomerates from their initial stages. Subsequently, in 2020 and thanks to its extensive experience in handling nanocomposites, it developed a new generation of polymeric macrofibers with graphene nanofilling. The benefits that GO offers at the nano and micrometric level have been evaluated in the laboratory and in the field on concrete macro designs, obtaining excellent results in terms of workability, density, impermeability, heat dissipation, setting, appearance and with balanced mechanical contributions of resistance to compression, tension, flexibility and abrasion that together complement the economic, environmental and quality needs of rigid pavements, among many other cement-based structures. Its use is very simple and does not require additional equipment or processes to those regularly used in construction, in addition to allowing adjustments in its handling, dosage and use in conjunction with other additives to improve its performance.

Drafting: EF/DHS

References

  1. Houxuan Li, et al., Recent progress of cement-based materials modified by graphene and its derivatives. Materials 2023, 16, 3783. 2. I. Fonseka, et al., Producing sustainable rigid pavements with the addition of graphene oxide. 2023; 3. Byoung Hooi Cho., Concrete composites reinforced with graphene oxide nanoflake (GONF) and steel fiber for application in rigid pavement. Case Stud. Constr. Mater. 2022; 17: e01346; 4. Kiran K. Khot, Experimental study on rigid pavement by using nano concrete. Int Res J Eng Techno, 2021; 08: 07,4865; 5. Jayasooriya, D. et al., Application of graphene-based nanomaterials as a reinforcement to concrete pavements. Sustainability 2022, 14, 11282; 6. Sen Du, et al., Effect of admixing graphene oxide on abrasión resistance of ordinary portland cement concrete. AIP Advances. 2019; 9: 105110; 7. D. Mohottia, et al., Abrasion and Strength of high percentage Graphene Oxide (GO) Incorporated Concrete. J. Struct. Eng. 2022; 21: 1; 8. Fayyad, T., Abdalqader, A., & Sonebi, M. An insight into graphene as an additive for the use in concrete. In Civil Engineering Research Association of Ireland Conference 2022 (CERAI 2022): Proceedings (CERAI Proceedings).

Overcoming Construction Challenges

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Overcoming Construction Challenges:

Graphene Oxide Additives Minimize Thermal Cracking

In concrete, the binding agents are mainly a combination of pozzolanic materials and cement that, during the hydration process, releases heat accompanied by volumetric changes. This phenomenon in the presence of elements with low thermal dissipation prevents heat from diffusing efficiently, resulting in a temperature gradient between the outer surface and the inner core. That is, the temperature on the surface of the mixture usually cools faster, but inside it, the temperature rises gradually. This non-uniformity in heat distribution can generate large tensile stresses responsible for the well-known thermal cracking of concrete.

Current strategies to reduce such thermal stresses include placement of cooling pipes, use of low-heat Portland cement, phase change materials, polymeric fibers, or surface insulation. However, little attention is paid to improving the spread of heat in the cement itself. In this sense, and since cement is a nanostructured material due to the content of C-S-H nanoparticles, it is not uncommon for the nanoscale to be one of the most innovative trends in modern civil engineering, since it has been proven that most of the affectations of concrete, as thermal cracking, originate from different chemical and mechanical factors of the cement structure, the main concrete binder.

Graphene oxide (GO) is an oxidized version of Graphene, the nanomaterial that over the past decade has been the focus of numerous industries, including the construction industry. Both nanostructures are a single sheet of densely organized carbon atoms that provide numerous mechanical, thermal, and electrical properties, among others.

GO, unlike Graphene, contains a large number of oxygenated groups of the epoxide (C-O-C), hydroxyl (-OH) and carboxyl (-COOH) type that make it, on the one hand, a material that is easily dispersible in water and, on the other , give it the ability to interact with the C-S-H nanoparticles of the cement to transfer its properties and improve its performance and durability from the micro and nano scale.

Thermal conductivity

The thermal conductivity of GO depending on the degree of oxidation can reach 670 W/ (m K), while the conductivity of copper and aluminum is approximately 384 and 180 W/ (m K), respectively. This means that GO can conduct heat more efficiently than metals. However, transferring this property to other materials is not an easy task, for which it is important to overcome three main challenges:

i) Have extensive scientific knowledge of graphene materials, if possible, from their synthesis or production,

ii) Control the quality of the mix design and,

iii) Have a comprehensive vision, both technical and scientific, for the proper use and distribution of GO nanoparticles with cement to achieve the objectives set.

Graphenergy Construcción® is a water-based multipurpose additive with a specialized formula based on graphene oxide that favors the cement hydration process, not only acting as a promoter for the formation of a network of C-S-H crystals responsible for the densification and resistance of concrete, but also improves the thermal conductivity during its hydration and setting.

During the hydration of the cement, an exothermic reaction occurs, that is, heat is released, which is also accompanied by volume changes. When this heat is not dissipated efficiently, large tensile stresses can be generated, that are responsible for the well-known thermal cracking of concrete.

The crystalline network of the GO structure allows it to dissipate heat with great efficiency and even withstand intense electrical currents without heating up.

In the case of fresh concrete mixes, Graphenergy Construcción® promotes a more homogeneous heat distribution, minimizing the temperature gradient and volumetric changes, thus reducing the probability of thermal cracking.

In the case of hardened concrete, and even though it is an insulating material, when it is exposed to temperatures close to 400°C, its mechanical resistance is significantly compromised. The use of Graphenergy Construcción® reduces this risk, since it has been proven that its application generates a temperature difference 70% lower than the parameter required by the test between the exposed surface and the surface not exposed to fire.

Therefore, the contribution of the GO nanonetwork present in Graphenergy Construcción® helps to homogeneously distribute the hydration and setting temperature, reduces the risk of thermal cracking, increases the resistance of concrete at high temperatures and, finally, offers an excellent option sustainable for energy savings, particularly for those buildings whose geographical location requires the use of air conditioning equipment, achieving temperature reductions of up to 3 °C inside the buildings.

Drafting: EF/DHS

References

  1. Tanvir S., et al. Nano reinforced cement paste composite with functionalized graphene and pristine graphene nanoplatelets. Compos. B. Eng. 2020; 197: 15, 108063,
  2. Dong Lu., et al. Nano-engineering the interfacial transition zone in cement composites with graphene oxide. Constr. Build. Mater. 2022; 356: 129284,
  3. Peng Zhang., et al. A review on properties of cement-based composites doped with Graphene. J. Build. Eng. 2023: 70, 106367,
  4. WANG Qin et al., Research progress on the effect of graphene oxide on the properties of cement-based composites. New Carbon Mater. 2021; 36: 4,
  5. Junjie Chen, Effect of oxidation degree on the thermal properties of graphene oxide. j mater rest technol. 2020; 9:13740,
  6. Karthik Chintalapudi. The effects of Graphene Oxide addition on hydration process, crystal shapes, and microstructural transformation of Ordinary Portland Cement. J. Build. Eng. 2020; 32, 101551,
  7. Guojian Jing et al., Introducing reduced graphene oxide to enhance the thermal properties of cement composites. Cem Concr Compos. 2020; 109, 103559,
  8. Jinwoo An et al., Edge-oxidized graphene oxide (EOGO) in cement composites: Cement hydration and microstructure. Compos. B. Eng. 2019; 173, 106795

Improving protection and agricultural productivity

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Improving protection and agricultural productivity

thanks to plastic films with graphene oxide

The applications of plastic materials are very diverse, for use in agriculture, the formulation and development of plastic films for greenhouse covers, macrotunnels and microtunnels and for soil padding stands out. Among the most used plastic materials are Linear High Density Polyethylene (HDPE), Ethylvinylacetate (EVA), in the case of covers for structures, and Linear Low Density Polyethylene (LLDPE) as the main polymer for the manufacture of films for floor mulch.

Plastic films with the capacity to convert and transmit solar energy are materials of great interest for photothermal applications in agriculture. In this sense, the development of mulch films with good mechanical properties and photothermal conversion properties suitable for the agricultural field is still an urgent demand.

In recent years, graphene has attracted considerable attention due to its unique sheet structure, its extraordinary photothermal properties, and its mechanical properties.

To improve the solar conversion efficiency of plastic films, carbon-based nanomaterials such as: graphene (GnP), graphene oxide (GO) and reduced graphene oxide (RGO) can be incorporated, because they have excellent light absorption capacity with a wide spectral range (from ultraviolet to near infrared), and can convert light energy into heat energy (photothermal property).

Recent developments in the formulation of films, look for the blocking of UV radiation, the fluorescence effect, ultra-thermal films and more impermeable films. Other key properties desired in plastic films are mechanical resistance (greater durability), optical properties and anti-drip effect.

Recent studies have reported the values of water vapor permeability (WVP) in plastic films composed of graphene at different concentrations (0, 2, 4, 6 and 8% by weight). Where it was found that the water vapor permeability in the films continuously decreases (improves the barrier property) as the concentration of graphene in the films increases. This evaluation was carried out at different relative humidity (RH) percentages, where good performance in the barrier property could be observed at different humidity percentages (32%, 55% and 76%), see Fig. 1. When the graphene content increases up to 8% by weight, the WVP of the composite films decreases from 3.9 x10-10, 5.5 x10-10, and 7.6 x10-10g/m h Pa to 0.6 x10-10, 0.8 x10- 10, and 1.2 x10-10g/m·h·Pa at 32%, 55% and 76% relative humidity, respectively. This decrease in permeability is associated with the fact that graphene forms barriers at the molecular level in plastic films, giving rise to more tortuous paths for the diffusion of water vapor molecules or oxygen molecules, limiting their transportation through the plastic film. This reduction can also largely prevent evaporation and loss of water, a very valuable resource in these times of scarcity.

In Fig. 2, the stress curves of the graphene composite films are shown. It was found that the tensile strength of the films with graphene (2-8% by weight) increased up to 22.6 MPa compared to the virgin or control film (18.3 MPa). While the Young’s Modulus continuously increased from 95.7 to 171.2 MPa with the graphene content from 0 to 8% by weight, these results show an improvement in mechanical strength.

From the point of view of the horticulturist, the most relevant mechanical properties are: resistance to traction, tearing and impact. Tensile strength assesses the film’s ability to withstand tensile stresses and is very important when mounting the film to the padding.

Regarding advances in polymeric compounds with graphene and derivatives in solar energy conversion applications. Fig. 3 illustrates the photothermal conversion efficiency of the films on the soil surface. The photothermal conversion efficiency of graphene composite films was observed to gradually increase with graphene content.

The films composed at concentrations of 2,4,6 and 8% by weight of graphene, showed a higher photothermal conversion efficiency (10.1, 19, 26 and 40.3%) than the control film (6.7%) for a temperature of 27° C, indicating that graphene composite films can effectively adsorb light and can convert light energy into heat input that can rapidly increase soil temperature.

Interestingly, all graphene composite films showed better photothermal conversion performance to increase soil temperature compared to the control group. These results indicate that the composite films have good mechanical properties and adequate photothermal conversion properties that can potentially be used in mulch films to improve soil temperature and maintain soil moisture, which is beneficial for plant growth and production. agricultural crops.

Currently Energeia – Graphenemex®, a leading Mexican company in Latin America in research and production of graphene materials for the development of applications at an industrial level, through its Graphenergy Masterbatch line, has developed and sells a wide range of masterbatches with graphene (graphene concentrate), with polymers widely used in agriculture and/or horticulture, such as LLDPE, LDPE, and HDPE. Our Masterbatches are granulated materials that act as multifunctional reinforcements for the production of more resistant plastic films with lower permeability and with a high degree of photothermal conversion.

References

  1. Melt processing and properties of linear low density polyethylene-graphene nanoplatelet composites. P. Khanam, M.A. AlMaadeed, M. Ouederni, E. HarkinJones, B. Mayoral, A. Hamilton, D. Sun. 2016, Vacuum , Vol. 130, págs. 63-71.
  2. Sun, Q., Geng, Z., Dong, J., Peng, P., Zhang, Q., Xiao, Y., & She, D. (2020). Graphene nanoplatelets/Eucommia rubber composite film with high photothermal conversion performance for soil mulching. Journal of the Taiwan Institute of Chemical Engineers.
  3. Effect of functionalized graphene on the physical properties of linear low density polyethylene nanocomposites. T. Kuila, S. Bose, A. K. Mishra, P. Khanra, N. H. Kim, J. H. Lee. 2012, Polymer Testing, Vol. 31, págs. 31-38.

The impact of graphene on the setting and strength of concrete

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The impact of graphene

on the setting and strength of concrete

Setting accelerating additives for cement-based structures are usually used when it is necessary to reach the desired resistance in less time, either to maintain continuous production or when the product needs to be put into operation immediately. However, the large number of variables that interfere in this process makes it difficult to accurately anticipate the acceleration that can be obtained with each new additive; without forgetting the importance of controlling the exothermic reaction or heat release that occurs during the setting or curing of the cement to avoid the appearance of thermal cracks in the final product.

To understand part of the reactions that occur during the setting of cement, it is important to know a little about its composition, for example: around 75% is made up of tricalcium silicate and dicalcium silicate which, when reacting with water, form calcium hydroxide and silicate. hydrated calcium (C-S-H), the latter being a nanometric component and, at the same time, the most important element, since the setting, hardening, resistance and dimensional stability of the cement depend on it.

Previous articles have discussed the interesting interaction of C-S-H nanoparticles with graphene oxide (GO) nanoparticles, another nanometric structure composed of carbon atoms and oxygen groups that has captured the attention of the construction industry thanks to its benefits during the hydration of cement and the direct impact it has to improve its mechanical resistance and durability, but also its interesting role as a setting accelerator, mainly for lightened polymeric concretes.

“GO acts as a catalytic agent during the cement hydration reaction”

The presence of oxygenated groups on the surface of GO allows it to absorb water and cement molecules to stabilize, on one hand, the atoms in the C-S-H by providing oxygen sites for the silicate chains and on the other, to act as a reservoir of water and transport channels to improve the hydration of cement.

In addition, the excellent compatibility of GO with different types of resins made it the perfect candidate for reinforcing polymer-type concrete that, although it does not contain a significant phase of hydrated cement, Portland cement is often used as a filling material and, thus giving the GO a larger array to transfer its properties to.

Graphenergy Construcción® is a water-based multipurpose additive with a specialized formula based on Graphene Oxide that contributes to improve the microstructure of any cement-based product, offering the following benefits during the setting process:

Setting: Acceleration of setting time up to 30%.

Drying: Helps uniform drying with fewer marks or moisture spots.

Increased resistance during demoulding of precast products: Greater integrity of the structures, better definition of angles and a significant reduction of product fracture.

Resistance to thermal changes: the good thermal conductivity of its formulation promotes a more homogeneous heat distribution during the hydration of the cement and, therefore, contributes to reducing the appearance of thermal cracks and reduces product fractures in cold climates.

Good integration with other additives or components of concrete mixes. It favors the workability of the mixtures.

Drafting: EF/DHS

Sources

  1. Ultrahigh Performance Nanoengineered Graphene- Concrete Composites for Multifunctional Applications. Adv. Funct. Mater. 2018; 28: 1705183;
  2. The role of graphene/graphene oxide in cement hydration. Nanotechnology Reviews. 2021;10(1):768;
  3. Experimental study of the effects of graphene nanoplatelets on microstructure and compressive properties of concrete under chloride ion corrosion. Construction and Building Materials, 2022; 360, 129564;
  4. Effect Of On Graphene Oxide the Concrete Resistance to Chloride Ion Permeability. IOP Conf. Ser. 2018: Mater. Sci. Eng. 394 032020;
  5. Effects of graphene oxide on early-age hydration and electrical resistivity of Portland cement paste. Constr Build Mater. 2017; 136, 506;
  6. Recent progress on graphene oxide for next-generation concrete: Characterizations, applications and challenges. “J. Build. Eng. 2023; 69, 106192;
  7. Graphene nanoplatelet reinforced concrete for self-sensing structures – A lifecycle assessment perspective. J. Clean. Prod. 2019; 240, 118202;
  8. Graphene opens pathways to a carbon -neutral cement industry. Science Bulletin. 2021; 67;
  9. Reinforcing Effects of Graphene Oxide on Portland Cement Paste. J. Mater. Civ. Eng. 2014; A4014010-1;
  10. A review on the properties, reinforcing effects, and commercialization of nanomaterials for cement-based materials. Nanotechnology Reviews, 2020; 9: 303–322, 10;
  11. Chloride permeability of reinforced concrete located in a submerged marine environment. Construction Engineering Magazine. 2007; 22: 1, 15;
  12. Penetrability of concrete to water and aggressive ions as a determining factor of its durability. Construction Materials, 1973; 23: 150;
  13. Electrical resistivity as a control parameter of concrete and its durability. ALCONPAT Magazine, 2011; 1 (2), 90,
  14. Portland cement blended with nanoparticles. Dyna, 2007; 74:152, 277;
  15. Improvement in concrete resistance against water and chloride ingress by adding graphene nanoplatelet. Cem concres, 2016; 83:114;
  16. Catalytic behavior of graphene oxide for cement hydration process. Journal of Physics and Chemistry of Solids, 2016; 89: 128.
  17. Review on Graphene oxide composites. Int. J nanomater nanostructures. 2016; 24.

The ingredient that will transform the plastics industry

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The ingredient that will transform the plastics industry:

Discover the benefits of Graphenemex graphene masterbatches as a nucleation agent

The plastics industry constantly demands new reinforcements or additives that allow the improvement of plastic materials, both for commercial and engineering use. In recent years, the use of graphene and its derivatives (graphene oxide, GO) has been promoted as new reinforcements for different polymer matrices.

Graphene is a nanomaterial (nanometric particle) that has extraordinary electrical, optical, thermal properties and high mechanical resistance. The properties of graphene are attributed to its structure in the form of two-dimensional (2D) sheets, formed by carbon atoms linked in a hexagonal manner and a thickness of one carbon atom.

The incorporation of graphene materials in polymers allows the development of polymeric compounds with greater mechanical resistance, greater impact resistance, resistance to UV radiation and greater thermal stability, among other properties. This allows obtaining better materials, with great potential and a wide range of applications for different sectors (automotive, aerospace, electronics or packaging).

In general when we talk about traditional polymeric compounds, they are materials that contain a quantity (~40%) of reinforcement in the polymeric matrix. In contrast, polymeric compounds with graphene (nanocomposites), graphene improves the properties of the polymer with the use of low concentrations (<2% weight), as reinforcement. Various investigations have shown that polymers functionalized with graphene materials provide improvements in mechanical, thermal, and electrical properties. For example in:

  • Polypropylene / Graphene compounds, showed an increase in flexural modulus (30%) and an increase in impact resistance (40%) compared to other commercial composites.
  • Polyethylene / Graphene compound, improves tensile strength (17%), flexural strength and rupture strength (66%).
  • Polystyrene/graphene compounds, showed an increase in electrical conductivity at room temperature from 0.1 to 1 S/m.

In addition to what was mentioned above, it is important to indicate that graphene materials function as nucleation agents in semicrystalline polymers. One of the most important characteristics of semicrystalline polymers is the degree of crystallinity. Many properties are influenced by the degree of crystallinity of the polymers.

While crystallinity in metals and ceramics implies the arrangement or arrangement of atoms and ions, in polymers it implies the arrangement of molecules and, therefore, the complexity is greater. Polymer crystallinity can be thought of as the packing of molecular chains to produce an ordered atomic arrangement. Because polymer molecules are large and complex, they are often partially crystalline (semi-crystalline) with scattered crystalline regions within an amorphous material. In the amorphous region, disordered chains appear, a very common condition due to twists, folds and folds of the chains that prevent the ordering of each segment of each chain.

In general, few polymers have a sufficient structure to crystallize and even in these cases, it is never possible to achieve 100% crystalline structure and the degree of crystallization (Xc) must be determined, that is, the fraction of the polymer that presents a crystalline structure in relation to the total polymer, the rest will be amorphous.

The general tendency of the addition of nucleating agents in polymeric matrices is the acceleration or retardation of crystallization, changes in the size of the spherulites, changes in the morphology and in some cases changes in the crystal structure. If we focus on the effect of graphene materials on the crystallinity of polymers, we can summarize that; Graphene materials make it possible to control the size of spherulites (crystal growth) in polymeric compounds, which leads to controlling the crystalline zones, which are responsible for mechanical resistance, and the amorphous zones (associated with flexibility and elasticity). of the material). In addition to improving interfacial adhesion in polymer matrices with polar groups, such as nylon 6,6. On the other hand, another advantage of graphene materials as a nucleating agent in polymeric compounds is that the crystallization temperature (Tc) increases as the amount of graphene increases because the crystallization of the melt is promoted, that is, Less energy is needed to cool the molten polymer, saving time and energy.

A. Intramolecular bonding in Nylon 6,6/GO Nanocomposites. B. DSC thermograms. Cooling: (a) PA66, (b) PA66/01RGO, (c) PA66/05RGO, (d) PA66/10RGO, (e) PA66/01GO, (f) PA66/05GO, (g) PA66/10GO. Taken from Materials 2013,6.2

Currently Energeia – Graphenemex®, a leading Mexican company in Latin America in research and production of graphene materials for the development of applications at an industrial level, through its Graphenergy Masterbatch line, has developed and sells a wide range of masterbatches with graphene, based on various polymers, such as PP, HDPE, LDPE, PET and PA6. Our Masterbatches are granular materials that act as multifunctional reinforcements and effective nucleating agents.

References

  1. Gong, L., Yin, B., Li, L., & Yang, M. (2015). Nylon-6/Graphene composites modified through polymeric modification of graphene. Composites Part B: Engineering, 73, 49–56.
  2. Fabiola Navarro-Pardo, Gonzalo Martínez-Barrera, Ana Laura Martínez-Hernández, Víctor M. Castaño. Effects on the Thermo-Mechanical and Crystallinity Properties of Nylon 6,6 Electrospun Fibres Reinforced with One Dimensional (1D) and Two Dimensional (2D) Carbon. Materials 2013, 6.
  3. Zhang, F.; Peng, X.; Yan, W.; Peng, Z.; Shen, Y. Nonisothermal crystallization kinetics of in-situ nylon 6/graphene composites by differential scanning calorimetry. J. Polym. Sci. Part B. Polym. Phys. 2011, 49, 1381–1388.
  4. Yun, Y.S.; Bae, Y.H.; Kim, D.H.; Lee, J.Y.; Chin, I.J.; Jin, HJ. Reinforcing effects of adding alkylated graphene oxide to polypropylene. Carbon 2011, 49, 3553–3559.
  5. Cheng, S.; Chen, X.; Hsuan, Y.G.; Li, C.Y. Reduced graphene oxide induced polyethylene crystallization in solution and composites. Macromolecules 2012, 45, 993–1000.

Protecting concrete

Posted on | by Energeia Graphenemex

Protecting concrete:

additives and coatings for greater durability in construction

“The compressive strength test is usually the most used parameter as an indicator of concrete quality; however, its value does not determine its durability by itself, that is, in addition to mechanical resistance, permeability and chemical resistance also influence its useful life”

The permeability of concrete is understood as the passage of water and aggressive ions through the capillaries between the aggregates and the cement paste; this is a complex phenomenon and depends above all on the atomic structure of the penetrating ions. One of the most harmful substances for concrete are chloride ions, these can be present from the beginning in the fresh mix, that is, dissolved in the aggregates, additives or in the water, or permeate from the outside, this being the case that exposes the greatest risk of corrosion. Although in general it can be said that the durability of concrete against atmospheric agents depends fundamentally on its permeability to water, while the durability with respect to aggressive salts, both for concrete and for reinforcement, depends on its resistance to the entry of chlorides. by different ways.

“The penetrability of the chlorides is manifested mainly by the diffusion of the ions in the concrete, rather than by the penetration of the entire solution into the samples. That is, the penetration of chlorides does not depend solely on the permeability of the water”

To protect concrete against corrosion, there are two main types of products: on the one hand, there are additives for fresh concrete mixes whose function is to act on the metal surface, canceling the anodic or cathodic reaction or both, and on the other, there are coatings. for the protection of hardened concrete. However, whatever the product used, anticorrosion protection is usually temporary, especially when the structures are subject to movements, loads or temperatures that could affect the performance of the protection or barrier placed.

In the previous article entitled Towards sustainable construction, we discussed the importance of the key nanometric component in the resistance of cement, known as hydrated calcium silicates (C-S-H) or tobermorite gel, and it’s interesting interaction with graphene oxide (GO) nanoparticles, a nanometric structure derived from graphite and of recent interest for the development of more resistant, durable and environmentally friendly structures.

GO is formed by nanometric sheets of carbon atoms linked in a hexagonal pattern and by a series of oxygenated groups anchored to its surface that facilitates its dispersion in water and combining with other materials, for example, with the nanoparticles present in cement (C-S-H).

In this regard, international studies show that the shape and surface chemistry of GO allow it to act as a platform to accelerate the hydration of cement and promote the creation of large amounts of C-S-H particles, from the formation of a new GO/ bond. C-S-H. This strong interaction gives rise to a denser network of interlocking cement crystals which, in addition to favoring the mechanical properties of the structures, also acts as a barrier against the infiltration of water through the capillary pores, but with an effect that last longer than currently available additives. This property is extremely important for the durability of concrete and for the prevention of alkali-silica reaction (ASR), an expansion reaction that occurs in the presence of moisture between alkaline cement paste and reactive amorphous silica causing cracks.

Electrical resistivity and corrosion rate Another important test for concrete is electrical resistivity and is defined as the resistance of a material to the passage of electrical charges; its measurement in concrete is a common test to identify the presence of moisture, as well as to predict the initiation period of corrosion in reinforced concrete based on the inverse relationship between electrical resistivity and ion diffusivity. That is, the higher the resistivity, the less movement of electrical charges caused by a lower porosity. The participation of graphene oxide nanoparticles in this property has also been evaluated in different studies that confirm that the GO/C-S-H interaction produces a more compact or less porous concrete that, in addition to reducing water and ion permeability, also limits the movement of electrical charges providing greater anticorrosive protection of metallic concrete structures.

Energeia Fusion (Graphenemex®), the leading Mexican company in Latin America in the research and production of graphene materials, for more than 10 years has been given the task of materializing the benefits of graphene on a scientific basis to turn it into real applications. Thus, after a long journey of research and with results comparable to those reported by various international studies regarding the use of graphene oxide in different products, including concrete, in 2018 it managed to launch Graphenergy Construcción®, the first additive on the market. for concrete with graphene oxide in the world; a multifunctional water-based additive that contributes to improve different properties of cement-based structures with a single application, such as:

  1. Remodeling of the microstructure of the cement paste with better interfacial bond GO/C-S-H,
  2. Better compactness of the cement,
  3. Less movement of electric charges,
  4. Decrease in the crack extension process,
  5. Significant reductions in the rate of calcium hydroxide handling,
  6. Greater mechanical resistance by improving its microstructure,
  7. Greater durability of the structures due to improvements in impermeability, resistance to chloride penetration and reduction of penetration depth.

It is important to remember that these effects may vary since, in addition to the type of graphene or graphene oxide used, the final properties of cement-based structures also depend on factors such as the water-cement ratio, degree of compaction of the mixture; the characteristics of cement, aggregates, additives, among others, but with proper management and monitoring of graphene additives, the results can be very interesting.

Drafting: EF/DHS

Sources

  1. Ultrahigh Performance Nanoengineered Graphene- Concrete Composites for Multifunctional Applications. Adv. Funct. Mater. 2018; 28: 1705183;
  2. The role of graphene/graphene oxide in cement hydration. Nanotechnology Reviews. 2021;10(1): 768;
  3. Experimental study of the effects of graphene nanoplatelets on microstructure and compressive properties of concrete under chloride ion corrosión. Construction and Building Materials, 2022; 360, 129564;
  4. Effect Of On Graphene Oxide the Concrete Resistance to Chloride Ion Permeability. IOP Conf. Ser. 2018: Mater. Sci. Eng. 394 032020;
  5. Effects of graphene oxide on early-age hydration and electrical resistivity of Portland cement paste. Constr Build Mater. 2017; 136, 506;
  6. Recent progress on graphene oxide for next-generation concrete: Characterizations, applications and challenges. “J. Build. Eng. 2023; 69, 106192;
  7. Graphene nanoplatelet reinforced concrete for self-sensing structures – A lifecycle assessment perspective. J. Clean. Prod. 2019; 240, 118202;
  8. Graphene opens pathways to a carbon-neutral cement industry. Science Bulletin. 2021; 67;
  9. Reinforcing Effects of Graphene Oxide on Portland Cement Paste. J. Mater. Civ. Eng. 2014; A4014010-1;
  10. A review on the properties, reinforcing effects, and commercialization of nanomaterials for cement-based materials. Nanotechnology Reviews 2020; 9: 303–322, 10;
  11. Permeabilidad a los cloruros del hormigón armado situado en ambiente marino sumergido. Revista Ingeniería de Construcción. 2007; 22: 1, 15;
  12. Penetrabilidad del hormigón al agua y a los iones agresivos como factor determinante de su durabilidad. Materiales de Construcción, 1973; 23: 150;
  13. La resistividad eléctrica como parámetro de control del hormigón y de su durabilidad. Revista ALCONPAT, 2011; 1(2),90;
  14. Portland cement blended with nanoparticles. Dyna, 2007; 74:152, 277;
  15. Improvement in concrete resistance against water and chloride ingress by adding graphene nanoplatelet. Cem concr res, 2016; 83: 114

Towards a sustainable construction

Posted on | by Energeia Graphenemex

Towards a sustainable construction:

how graphene oxide increases the resistance of concrete and favors the reduction of CO2 emissions

The investigation of new technologies for the cement and concrete industry is not only limited to improving its durability, but also to seeking strategies to control its influence on climate change, taking as a background that this industry is the third largest source of emissions of carbon dioxide (CO2) and that the global challenge for 2030 is to reduce these emissions by at least 16%.

Nanotechnology

Nanotechnology for the cement industry is not a new concept, in fact, cement is considered a nanostructured material because 50 to 60% of its composition consists of nanoparticles of approximately 10 nm known as hydrated calcium silicates (C-S-H). or tobermorite gel. This important nanometric component is the foundation for the development of new formulations applying other nanoparticles such as Nano Silica (n. SiO2), Nano Titanium Oxide (n. TiO2), Nano Ferric Oxide (n. Fe2O3), Nano Aluminum Oxide or alumina (n. Al2O3), Clay Nanoparticles and Carbon Nanoparticles, such as carbon nanotubes, graphene nanoparticles or graphene oxide.

“C-S-H fills the empty spaces in the cement, improves the density, cohesion, impermeability and resistance of the cement”

Graphene oxide (GO) is a carbon nanoparticle obtained from the oxidation and exfoliation of graphite. Its well-known mechanical and impermeability properties, combined with a nucleating and densifying effect on the microstructure of cement, captured the attention of scientists and industries when they discovered that the use of low concentrations of this nanomaterial allows the development of more resistant, durable, and friendly structures with the environment.

“GO promotes the formation of C-S-H to improve and accelerate cement hydration through a new chemical bond”

How does GO interact with cement?

Although it is perfectly documented that C-S-H is responsible for 60 to 80% of the strength of cement, recent research has shown that GO further favors these results and that it is not exclusive to improve mechanical strength, but also contributes with other properties such as impermeability, anticorrosiveness and/or thermal insulation. The benefits that GO brings to cement itself or to cement-based materials are attributed to the interaction between the carboxyl groups (COOH) of GO with the C-S-H of the cement to form strong GO/C-S-H chemical bonds. This occurs in the following way, when the cement comes into contact with water, it dissolves and releases large amounts of ions; On the other hand, GO, by presenting a large surface area and good capacity to increase the mobility of Ca2+ ions in the cement paste, GO allows them to be adsorbed on it. In other words, GO acts as a platform to enhance the nucleation or promotion effect to form a large number of C-S-H particles (fig. 1), a phenomenon that ultimately facilitates the hydration process at an early age and which in turn leads to the formation of denser, more resistant and less permeable microstructures.

“Hydration is the process by which cement reacts chemically in the presence of water, develops binding properties and becomes a bonding agent.”

Fig. 1. Schematic representation of the interaction of the cement paste in the presence of graphene and graphene oxide.
Taken from: Nanotechnology Reviews (2021), vol. 10, no. 1,768

Mechanical resistance vs. lower CO2 emissions

The compressive strength test is the most common measure to control the quality of concrete and, therefore, it is also the most widely used technique to evaluate the effect of GO on these structures. According to tests carried out in the laboratory, the presence of GO in the concrete can exceed 50% of the expected resistance, while field evaluations report improvement fluctuations in the range of 5% to 50%. This variation is due to the fact that, in addition to the type of GO and dosage studied, like any concrete structure, the resistance also depends on factors such as the water-cement ratio, the degree of compaction of the mix; the characteristics of the cement, aggregates and additives; the age of the concrete; the temperature and hygrometry of the curing environment. However, these values are attractive enough to be used not only in the design of more resistant structures, but also with lower cement content to contribute to the reduction of CO2 emissions. In fact, in 2019 a study carried out by researchers from the University of Cambridge revealed that, if the addition of graphene nanoparticles managed to reduce just 5% of the cement in the concrete mix, its effect on global warming would be reduced by one 21%”.

Due to the foregoing and, from the 21st Conference of the Parties to the United Nations Framework Convention on Climate Change (COP 21) held in 2015, which concluded with the adoption of the Decision and the Paris Agreement that, from 2020 promotes low-carbon development to keep the global temperature rise below 2°C, companies from countries such as England, Spain, the United States, Vietnam and Mexico have accelerated their efforts to promote the benefits of graphene nanotechnology in favor of the environment.

Energeia Fusion, the leading Mexican company in Latin America in the production of graphene materials and the development of applications, in 2018 launched Graphenergy Construcción®, the first additive for concrete with graphene oxide in the world; a multifunctional water-based additive that contributes to improving different properties of cement-based structures with a single application. Likewise, in the short term it hopes to have a graphene-reinforced cement available and contribute to achieving environmental commitments.

Sources

  1. Ultrahigh Performance Nanoengineered Graphene- Concrete Composites for Multifunctional Applications. Adv. Funct. Mater. 2018, 28, 1705183;
  2. The role of graphene/graphene oxide in cement hydration. Nanotechnology Reviews. 2021;10(1): 768;
  3. Experimental study Construction and Building Materials, 2022, 360, 129564;
  4. Effect Of On Graphene Oxide the Concrete Resistance to Chloride Ion Permeability. IOP Conf. Ser. 2018: Mater. Sci. Eng. 394 032020;
  5. Effects of graphene oxide on early-age hydration and electrical resistivity of Portland cement paste. Constr Build Mater. 2017, 136, 506;
  6. Recent progress on graphene oxide for next-generation concrete: Characterizations, applications and challenges. “J. Build. Eng. 2023, 69, 106192;
  7. Graphene nanoplatelet reinforced concrete for self-sensing structures – A lifecycle assessment perspective. J. Clean. Prod. 2019, 240, 118202;
  8. Graphene opens pathways to a carbon-neutral cement industry. 2021, Science Bulletin 67;
  9. Reinforcing Effects of Graphene Oxide on Portland Cement Paste. J. Mater. Civ. Eng. 2014. A4014010-1;
  10. A review on the properties, reinforcing effects, and commercialization of nanomaterials for cement-based materials. Nanotechnology Reviews 2020; 9: 303–322, 10;
  11. Permeabilidad a los cloruros del hormigón armado situado en ambiente marino sumergido. Revista Ingeniería de Construcción. 2007, 22, 1, 15;
  12. Penetrabilidad del hormigón al agua y a los iones agresivos como factor determinante de su durabilidad. Materiales de Construcción, 1973, 23, 150;
  13. La resistividad eléctrica como parámetro de control del hormigón y de su durabilidad. Revista ALCONPAT, 2011, 1(2),90;
  14. Portland cement blended with nanoparticles. Dyna, 2007, 74, 152, 277

The graphene additive for concrete

Posted on | by Energeia Graphenemex

The graphene additive for concrete:

a revolutionary thermal insulator in construction

In recent years, the construction industry is looking formward to improve the properties of mortar and concrete, to increase their durability, especially in structures exposed to aggressive or extreme environments. Among the properties that are sought to improve, is the resistance to compression, the resistance to compression tension, as well as to reduce cracking. With the increase in the volume of concrete in civil engineering projects, more attention has been paid to the thermal cracks that occur. Experimentation has shown that during the hydration process of the mortar and/or concrete, heat is generated due to the exothermic reactions that occur. Poor heat dissipation causes a gradient between the interior of the mass and its surface, which generates internal stresses and can lead to cracking or thermal cracking in the concrete.

Nowadays, graphene oxide (GO), a graphene precursor material, has attracted a lot of attention because it is an insulating material, with low thermal property and has extraordinary mechanical properties. GO has a large surface area (2600 m2/g) and the presence of oxygenated groups gives it unique properties that make it easily dispersed in water, making it an ideal nanomaterial for the development of concrete additives.

Although the mechanical properties of cement-based compounds and structures are important in building infrastructure, the thermal insulation property is very important to reduce energy consumption for air conditioning and heating in buildings. Therefore, GO is a good candidate due to its low thermal conductivity properties. Thermal conductivity is defined as the ability of a material to transfer heat. It is the phenomenon by which heat spreads from high-temperature areas (warmer) to colder areas within the material. In the case of GO, the presence of holes and functional groups on the GO surface cause local stress or instability, resulting in a reduction in thermal conductivity of up to 2 to 3 orders of magnitude (<100 W/m-K). In the GO, the propagation of heat flux occurs in the vacant regions (voids) and in the oxygenated functional groups of the GO surface (Figure 1). When a heat flux attempts to traverse the GO through some defect or vacancy, the heat flux not only propagates out of plane, but also disturbs the heat flux around the basal plane gap.

Figure 1. Schematic image of graphene oxide (GO) sheet with vacancy or defect defects
and randomly distributed oxygenated functional groups.

Recent investigations have reported the improvement of the thermal insulation properties of cement-based composite materials by adding different concentrations of GO, as well as the effect of GO on increasing compressive strength and greater impermeability to chloride ions. and water in concrete. The incorporation of GO decreased microcracking, the porosity of the material (decreases the volume of pores) and improved compaction. GO sheets become a barrier to crack propagation, which improves mechanical properties. The compressive strength of the specimens of the compounds with GO concentrations of 0.05% by weight increased by up to 18.7% and 13.7% at a curing age of 7 and 28 days, respectively. In the case of the evaluations of the thermal properties of the compounds, the thermal conductivity was 0.578 W/m K for the specimen without GO (control) and 0.490 W/m K for the compound with 0.1 % by weight of GO, while that the thermal diffusivity values oscillate between 0.38× 10-6 and 0.33× 10-6 m2/s (Figure 2). Thermal conductivity decreases with increasing GO content due to low conductivity or excellent insulating effect of GO sheets and good interactions between mortar and GO sheets. Generally, material with thermal conductivity values of less than 0.250 W/m K is known as a thermal insulator. Therefore, the thermal insulation of the mortar is improved in the compounds with the incorporation of GO.

Figure 2. a) Comparative graphs of the compressive strength of the compounds at different concentrations of GO at the curing age of 3, 7, 21, 28 and 77 days. b) Thermal conductivity and diffusivity of the compounds, at the curing age of 7 days.

Energeia -Graphenemex® developed and sells an admixture for concrete with graphene oxide (Graphenergy Construction). A nanotechnological additive that improves mechanical resistance, impermeability and provides an antimicrobial effect to any cement-based material. The additive can also manage to reduce the final number of pores in the set product, which translates into a more compact product and greater impermeability to the passage of water, improving the protection against corrosion of steel cores in concrete.

The thermal insulation property of the additive can achieve a reduction in the temperature of concrete-based structures, infrastructure, or buildings to a more comfortable temperature inside (up to 3 °C), reducing energy consumption for air conditioning and/or or heating in buildings.

References

  1. Janjaroen, Khammahong. The Mechanical and Thermal Properties of Cement CAST Mortar/Graphene Oxide Composites MaterialsInt J Concr Struct Mater (2022).
  2. Yi Yang, Jing Cao y col.Thermal Conductivity of Defective Graphene Oxide: A Molecular Dynamic Study. Molecules 2019, 24, 1103.
  3. Guojian Jing, Zhengmao Ye y col. Introducing reduced graphene oxide to enhance the thermal properties of cement composites. Cement and Concrete Composites 109 (2020) 103559.