The chapter delves into the properties of eco-cement blocks made with polymer wastes and graphene, highlighting the potential benefits of graphene incorporation in mortars. It discusses the impact of graphene on bulk density, water absorption, compressive strength, and thermal conductivity, while also addressing the challenges of dosage, dispersion, and cost. The research involves extensive testing and analysis, providing valuable data on the optimal use of graphene in cement-based materials. The chapter concludes with a call for further research to fully harness the potential of graphene in the construction industry.
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Abstract
The inclusion of polyurethane wastes as recycled and reusable materials to replace variable amounts of aggregates is interesting in the production of new construction materials due to their final properties. In this research, the effects of waste polymer replace by sand (25%) and graphene oxide on mortars (0.5, 1, 1.5, 2, 2.5 y 3% with respect to the cement) have been investigated. To maintain and even improve the final properties, graphene oxide modify aspect as thermal conductivity and electrical properties, water behavior, mechanical properties and final contribution to fire.
1 Introduction
The incorporation of graphene into mortars is still a relatively emerging field, and research is ongoing to explore its full potential and optimize its usage. The dosage, dispersion, and other factors related to graphene incorporation in mortars can affect the overall performance, and careful consideration should be given to ensure appropriate usage and compatibility with other components of the mortar mix [1]. Consultation with materials experts, testing, and adherence to relevant standards and guidelines are recommended when using graphene in mortars or any other construction materials.
Nanotechnology applied to polymer mortars such as graphene oxide make available the novelty in cement-based materials by adding an innovative vision to building materials.
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The introduction of graphene oxide into cement can provide several significant benefits as decrease the porosity and consequently increase the durability of structures reducing long-term maintenance costs, enhanced thermal and electrical conductivity with better heat distribution [2]. The addition of graphene oxide to cement can also help decrease the formation of cracks and fissures due to its ability to improve material cohesion and toughness. This results in increased structural integrity and reduced likelihood of premature failure. These are just some of the potential benefits of introducing graphene oxide into cement. However, it's important to note that the effectiveness and outcomes may vary depending on the dosage and specific application conditions [3].
The economic cost of introducing graphene into concrete can vary depending on several factors, including the amount of graphene used, the production process, and the availability of graphene in the market. In this way, it is important to consider the balance between cost and potential benefits when introducing graphene into concrete. On the other hand, as technology and graphene production methods continue to advance, it is possible that the costs associated with its use may gradually decrease.
To develop the final products in this research, the microstructure (obtained by SEM and optical microscopy), thermal and electrical conductivity, spectrophotometry and density with suitable outcomes is determinate. To complete the study, additional destructive test as compressive strength, non-combustibility test, TGA and water absorption has been also carried out.
2 Samples and Procedure
The mortars have been fabricated using CEM I type Portland, replacing a 25% of aggregates by polyurethane grinded waste. Relation of cement aggregate is 1/3. The graphene oxide has been added on mortars with 0.5, 1, 1.5, 2, 2.5 y 3% with respect to the cement weight. The amount of water is the required to achieve enough workability according EN 1015-19. The size and dimensions of samples are normalized with 160 × 40 × 40 mm3.
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3 Results and Discussion
To maintain and even improve the final properties, graphene oxide modify aspect densities, mechanical properties and water behavior.
3.1 Bulk Density
Bulk density test for mortar is a procedure used to determine the mass per unit volume of a mortar sample. It is a measure of the density or compactness of the mortar, and is an important parameter in assessing the quality and performance of mortar used in construction.
The bulk density of mortar is determined by dividing the mass of the mortar sample by its corresponding volume. The mass of the mortar sample is calculated using a scale, and the volume is determinate using a container of known volume. Results obtained for all the samples can be seen in Fig. 1.
Fig. 1.
Bulk density.
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Graphene is a two-dimensional material with a high aspect ratio (length-to-width ratio), which means it can form a network-like structure when incorporated into mortars. This can increase the packing density of the mortar, leading to higher bulk density when the amount of graphene increase in the sample. Graphene also can potentially influence the hydration of cement, which is a chemical reaction that occurs when cementitious materials react with water to form a solid matrix, indirectly affecting the bulk density of mortars.
3.2 Water Absorption
Water absorption in mortars refers to the ability of mortar to absorb and retain water. The water absorption characteristics of mortars can have important implications for their performance and durability in various applications. Several factors can affect water absorption in mortars, including the type and proportions of the constituents used in the mortar mix, curing conditions, and environmental factors such as temperature and humidity.
To calculate the water absorption of mortar, you would need to determine the weight of the dry mortar and the weight of the saturated mortar, and then use the following formula:
The results obtained for this measure are all in the range of 5.4%-6.2%, very similar for all the samples as can be seen in Fig. 2, the addition of graphene not seems decisive for this property.
Fig. 2.
Water absorption.
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3.3 Compressive Strength
Compressive strength is an important mechanical property of mortars, which refers to the maximum amount of load that a mortar specimen can support before failing in compression and is experimentally through testing EN 1015-11.
Fig. 3.
Compressive strength.
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The optimal dosage of graphene in mortars can vary depending on factors such as the type of graphene used, the mix design of the mortar, and the curing conditions. Our research has shown that an optimal dosage of graphene is achieved until a dosage of 1.0%. Exceeding this dosage, it is observed in Fig. 3 with a diminishing returns or even detrimental effects on the properties of the mortar. To avoid the tendency of graphene to agglomerate, nowadays we work adding surfactant-assisted dispersion, to ensure that graphene is evenly distributed throughout the mortar mix.
3.4 Thermal Conductivity
Graphene has an exceptionally high thermal conductivity, which refers to its ability to conduct heat. When incorporated into mortars, graphene can significantly enhance their thermal conductivity, allowing for more efficient heat transfer within the material. This can be advantageous in applications where good thermal management is important, such as in construction materials for buildings, where enhanced thermal conductivity can improve insulation properties and reduce energy consumption.
The thermal conductivity of reference mortars without graphene typically ranges from about 1.6 W/m·K. The temperature of test at isothermal conditions is also an interesting manner to determinate the final thermal conductivity testing involves measuring the ability of a material to conduct heat. The equipment used to determinate the thermal conductivity is the FOX 50 according standards ASTM C518 e ISO 8301 to ensure accurate and reliable results. (Fig. 4). By means of heat flow meter method, a temperature gradient pass from side to side the samples measuring the heat flow through it. The addition of graphene to this mortars increase the thermal conductivity with reported values ranging around 1.5 times, depending on the composition, with slight influence of graphene concentration.
Fig. 4.
Equipment FOX 50 and size of samples used.
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4 Conclusions
The successful incorporation of graphene into mortars requires careful consideration of factors such as graphene dispersion, concentration, and compatibility with other components of the mortar mix as polymer wastes. Additionally, dosage, cost and scalability of graphene production are important aspects to consider for practical applications of graphene in mortars. Further research and development are ongoing to fully understand the potential of graphene in mortars and other cement-based materials.
Acknowledgements
This work is supported by the Regional Government of Castilla y León (Junta de Castilla y León) and by the Ministry of Science and Innovation MICIN and the European Union NextGenerationEU/PRTR.
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