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.

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:

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

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.

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:

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.”

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:

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.

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.

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.