High mechanical performance concrete

Abstract

The present invention relates to high mechanical performance concrete incorporating pig hair bristles or fibres as secondary reinforcement fibres to increase its fire resistance in order to prevent or reduce the possibility of spalling or concrete explosion due to fire.

Description

[0001] High mechanical performance concrete

[0002] DESCRIPTIVE MEMORANDUM

[0003] FIELD OF INVENTION

[0004] The present invention is developed in the field of construction materials, specifically it refers to a high mechanical performance concrete that incorporates pig bristles or hair fibers as secondary reinforcing fibers to increase its fire resistance to avoid or reduce the possibility of the spalling phenomenon or explosion of concrete due to fire.

[0005] BACKGROUND OF THE INVENTION

[0006] Concrete is an artificial construction material composed of aggregates and binders, consisting of a mixture of cement, water, sand, and gravel, commonly including additives to improve some of its properties. Depending on its type, it can be applied to various structures, such as buildings, bridges, tunnels, roads and highways, floating structures, marine structures, foundations, pipes and conduits, among others.

[0007] When concrete is exposed to fire or subjected to high temperatures, such as in a fire, it undergoes a deterioration process known as spalling. After a period of exposure, this manifests as the detachment, usually explosive, of a portion of the concrete, generally its surface. These detachments can expose the interior regions of the concrete, reducing its mechanical properties (and those of the embedded steel, in the case of reinforced concrete) and affecting its structural integrity. Due to their explosive nature, these detachments can occur at speeds that can cause damage or injury to people in the vicinity.

[0008] Spalling occurs due to the rapid evaporation of water from the pores or capillary network of concrete, which forms during the setting or transition from a plastic to a hardened state of this composite material, due to high temperatures. The internal pressure within the concrete's capillary network increases with rising temperatures, producing microfractures in the higher-temperature areas. This results in the detachment of pieces or fragments from the concrete surface. Once detachment occurs, deterioration continues, with spalling occurring in the exposed area and generating new microfractures and breaks as long as the heat source persists.

[0009] In the state of the art, the use of modifying elements, such as steel bars and reinforcing meshes, or additives in the concrete mix, such as polymeric, metallic, glass and natural fibers, to improve the specific properties of the concrete is known.

[0010] In particular, regarding fire resistance, the prior art has described concretes with improved fire resistance or anti-spalling properties. In this respect, we can mention US patent 10,071,934 B1, which discloses an anti-spalling concrete composition with a fire resistance of at least 4 hours, a compressive strength of at least 120 MPa at room temperature, and a compressive strength of at least 20 MPa at 700°C. This composition includes steel fiber additives in an amount between 0.1% and 0.4% by volume of the concrete; polypropylene fibers with a melting point of 200°C or less in an amount between 0.05% and 0.3% by volume of the concrete; and carbon nanoparticles in an amount between 0.1% and 0.3% by volume of the concrete.

[0011] Another document that can be cited corresponds to application WO 2022 / 132054 A1 which describes a composition for fire-resistant concrete that can maintain the properties of conventional lightweight concrete, with high strength for structural use, which allows preventing the occurrence of explosive spalling during exposure to fire, comprising between 28% to 42% by weight of a binder, between 3% to 7% by weight of cenospheres, between 35% to 50% by weight of sand, between 8% to 13% by weight of lightweight coarse aggregate, between 0.05% to 0.5% by weight of a first fiber and between 1% to 4% by weight of a second fiber, where the first fiber can be polypropylene fiber, nylon fiber, rubberized fiber or any mixture thereof, and the second fiber can be steel fiber, glass fiber, carbon fiber, polyethylene fiber or any mixture thereof.

[0012] None of the solutions described in these documents provide a concrete or a concrete composition with high mechanical performance that incorporates pig bristles or hair fibers as secondary reinforcing fibers to increase its fire resistance to prevent or reduce the possibility of spalling or concrete explosion due to fire.

[0013] Despite the above, the incorporation of pig bristles or hair fibers into concrete has been investigated in the state of the art.

[0014] In this regard, Araya-Letelier et al. 2017

[0001] investigates the use of recycled fibers from the food industry, specifically pig hair, as reinforcement of cement-based materials, adding between 0 and 2% of pig hair by weight of cement in the mixtures, obtaining an increase of up to five times in impact resistance compared to a simple mortar.

[0015] Another document that can be cited is Dosque et al. 2023 [2] where the incorporation of animal fibers, such as pig hair, in a concrete matrix whose mixture includes said animal fibers in an amount of 8 kg / m³ is investigated. 3 Pig hair fibers incorporated into concrete are reported to be effective in preventing early cracking and plastic shrinkage, where, in addition, no relevant differences are observed in flexural strength and electrical resistivity.

[0016] In light of the above, prior art documents do not disclose the incorporation of pig hair fibers into concrete or a high mechanical performance concrete composition as secondary reinforcing fibers to increase its fire resistance to prevent or reduce the possibility of spalling or concrete explosion due to fire.

[0017] DESCRIPTION OF THE INVENTION The invention relates to a concrete or concrete composition incorporating pig bristles or hair fibers as secondary reinforcing fibers that increase fire resistance by preventing or reducing the phenomenon of spalling or explosion of concrete due to fire when said concrete is exposed to fire or subjected to high temperatures. Concrete with improved fire resistance will be relevant in applications in structures that must operate at high temperatures, such as foundries, or where there is a risk of fire or exposure to fire, such as buildings, roads, or tunnels. Therefore, the use of pig hair fibers to improve fire resistance is geared towards high-performance concretes, for example, with a characteristic compressive strength of 35 MPa or higher, and which require protection from explosive damage due to fire or spalling.

[0018] Another objective of the invention is the reuse of industrial pig hair waste, generated by the production of pork meat, to reduce the environmental impact of the food industry through a valorization of the waste.

[0019] It was discovered, through experimental tests, that pig hair fibers, incorporated into concrete, when they decompose due to an increase in temperature, generate a network of interconnected micropores that allows the release of tensions and water vapor, preventing an explosive leak of vapor, which reduces microfractures in the capillary network of the concrete, decreasing the damage caused to the concrete due to the spalling phenomenon.

[0020] The concrete mix comprises cement, water, industrial sand and gravel with a maximum nominal size of 4.75 mm, pig hair fiber, and at least one additive, preferably a water-reducing admixture with a retarding effect for concrete. The pig hair fibers are incorporated into the mix in an amount between 1.5 and 4.5 kg / m³. 3 .

[0021] Although the choice of the fiber origin can be any source of pig hair; in a particular embodiment of the invention said bristles or pig hair fibers are preferably chosen from pig hair

[0022] Pig hair fibers can be obtained from industrial pig meat waste or remnants which are subjected to a cleaning and selection process that allows obtaining clean pig bristles for use as secondary fibers in concrete.

[0023] A key feature of the present invention is that the pig hair fibers, and especially those derived from pig hair, are free of any type of organic residue, such as skin, blood, fat, and dust. Furthermore, these pig hair fibers must have a maximum fiber length of between 20 and 25 mm, which is achieved through appropriate sieving.

[0024] BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are included to provide a further understanding of the invention and form part of this description, where it can be seen that:

[0026] Figure 1 shows the results of a thermogravimetric analysis (TGA) to characterize the mass loss as a function of temperature of pig bristles (PH) alongside polypropylene (PP) microfibers, the latter being the gold standard of the industry.

[0027] Figure 2a shows the experimental results of an Abrams cone test for different concrete mixtures, following the ASTM C143 / C143 M standard [3].

[0028] Figure 2b shows the experimental results of a flow table test for different concrete mixtures, following the UNE-EN 12350-1 standard [4].

[0029] Figure 3a shows the results of a hardened state compressive strength test for different concrete mixtures, not exposed to fire, on cylindrical specimens 10 cm in diameter x 20 cm high, following the ASTM C39 / C39M standard [5].

[0030] Figure 3b shows the results of a hardened state modulus of elasticity test for different concrete mixtures, not exposed to fire, on cylindrical specimens 10 cm in diameter x 20 cm high, following the ASTM C469 / C469M standard [6].

[0031] Figure 4a shows the experimental setup of a fire resistance test for concrete, obtained using the torch method [7].

[0032] Figure 4b shows the data collection to generate a uniform heat distribution on the exposed face of the concrete mix.

[0033] Figure 5a shows cubic concrete specimens (exposed to fire) for a control mix (without fibers). Figure 5b shows cubic concrete specimens (exposed to fire) for a mix with pig hair fiber.

[0034] Figure 6 shows a PICZA 3D laser scanner.

[0035] Figure 7a shows a photograph of a concrete mix exhibiting spalling.

[0036] Figure 7b shows the three-dimensional model of a concrete mixture exhibiting spalling.

[0037] Figure 7c shows a depth map for a concrete mix exhibiting spalling. Figure 8a shows the scanning and post-processing results for determining the spalling volume for different concrete mixes.

[0038] Figure 8b shows the scanning and post-processing results for determining the depth of damage for different concrete mixes.

[0039] Figure 9a shows the results of a compression test for a control concrete mix (without fibers) without exposure to fire and with exposure to fire.

[0040] Figure 9b shows the results of a compression test for a concrete mixture with polypropylene fibers without exposure to fire and with exposure to fire.

[0041] Figure 9c shows the results of a compression test for a concrete mixture containing pig hair fibers, both with and without fire exposure. Figure 10 shows a compilation of the results of a compression test for various concrete mixtures: control, polypropylene fibers, and pig hair fibers, both with and without fire exposure.

[0042] DETAILED DESCRIPTION OF THE INVENTION

[0043] The invention relates to concrete or a concrete composition incorporating pig bristles or hair fibers as secondary reinforcing fibers that increase the fire resistance of the concrete, preventing or reducing the phenomenon of spalling or explosion of concrete due to fire when the concrete is exposed to fire or subjected to high temperatures. High-performance concrete with improved fire resistance will be relevant in applications in structures that must operate at high temperatures, such as foundries, or where there is a risk of fire or exposure to fire, such as buildings, roads, or tunnels.

[0044] It was discovered, through experimental tests, that pig hair fibers, incorporated into concrete, when they decompose due to an increase in temperature, generate a network of connected microporosity, which allows the release of tensions and water vapor, preventing an explosive leak of vapor, which reduces microfractures in the capillary network of the concrete, decreasing the damage caused to the concrete due to the spalling phenomenon.

[0045] The concrete mix comprises cement, water, industrial sand (incorporating oversized gravel), pig hair fiber, and at least one additive, preferably a water-reducing admixture with a retarding effect for concrete. In one embodiment, the concrete mix comprises 280 to 520 kg / m³ 3 of high-strength cement, for high early strength or sprayed concrete; 180 to 300 kg / m 3 of water; 1300 to 1800 kg / m 3 of industrial sand; 70 to 500 kg / m 3of industrial gravel, 1.1 to 3 kg / m 3 of a water-reducing admixture with retarding effect for concrete; and between 1.5 and 4.5 kg / m 3 of pig hair fibers. The concrete mix may also include 4 to 8.4 kg / m³ 3 of a high-performance polymer-based superplasticizing additive with a hardening acceleration effect for concrete.

[0046] In one modality, the recommended values ​​for the concrete mix correspond to: 400 kg / m 3 of high-strength cement, for high early strength or sprayed concrete; 220 kg / m 3 of water; 1591 kg / m 3 of industrial sand; 84 kg / m 3 of industrial gravel, 1.6 kg / m 3 of a water-reducing admixture with retarding effect for concrete; and between 3 kg / m 3 of pig hair fibers. In addition, the concrete mix may comprise 6 kg / m³ 3of the superplasticizing additive. This preferred concrete mix enhances the fire resistance of the concrete, preventing or reducing the phenomenon of spalling or concrete explosion due to fire, for high mechanical performance concretes.

[0047] In a preferred embodiment, pig hair fibers are obtained from pigs and peccaries, animals of the suborder Suina, including, but not limited to, pigs, swine, peccaries, wild boars, babirusas, and other close relatives. An even more preferred embodiment is that the pig hair fibers come from pigs. Pig hair fibers, particularly those selected from pig hair, are obtained from industrial pork waste or byproducts, which are subjected to a cleaning and selection process to obtain clean pig bristles for use as secondary fibers in concrete. This cleaning and selection process essentially consists of washing the pork waste or byproducts, which include the pig hair fibers, with water, followed by rinsing, drying, and sieving the fibers.

[0048] In a preferred modality, after sieving, pig hair fibers with a maximum fiber length size between 20 and 25 mm are obtained.

[0049] EXAMPLES OF EXPERIMENTAL RESULTS

[0050] Obtaining suitable pig hair fibers:

[0051] A cleaning and selection process was carried out on the pig hair fibers comprising the steps of: (i) adding boiling water and 1% by weight of neutral soap to a container and stirring; (ii) adding the pig meat waste or remnants, including the pig hair fibers, to the container; (iii) rubbing the pig hair fibers to remove the skin for at least 20 minutes; (iv) leaving to stand for 24 hours; (v) rinsing the pig hair fibers to remove organic residues, such as blood, fat, skin, and dust, to obtain clean pig hair fibers; (vi) drying the pig hair fibers for 24 hours at a temperature of at least 60°C in a drying oven; and (vii) sieving the dried pig hair fibers to obtain fibers of a desired size range to be used as secondary reinforcing fibers in concrete. For this last sieving step, a No. 4 sieve and a No. 40 sieve are used.

[0052] Characterization of mass loss:

[0053] A characterization of mass loss as a function of temperature was performed using thermogravimetric analysis (TGA) for pig hair fibers (PH) and polypropylene (PP) fibers, the gold standard in the industry. Figure 1 shows the results of the analysis, which reveals that the mass loss of pig hair fibers is faster than that of polypropylene fibers (for example, PH fibers have a 56% greater mass loss compared to PP fibers at a temperature of 400°C). eC), which is positive since its degradation occurs at a lower temperature, so when exposed to fire or high temperatures, connected microporosity is generated that forms the network that allows internal pressures of the concrete to be released in a shorter exposure time, which reduces the formation of microfractures in the concrete that cause detachment on its surface, so pig hair fibers decrease fire damage compared to polypropylene fibers.

[0054] Use in concrete types:

[0055] The use of fibers to improve fire resistance is geared towards high-performance concretes, for example, those with a characteristic compressive strength of 35 MPa or higher, that require protection against explosive damage from fire or spalling. These concretes are commonly used in tunnels, industrial floors, bridges, etc. However, providing concrete with enhanced fire resistance will also be relevant in applications involving structures that must operate at high temperatures, such as foundries, or where there is a risk of fire or exposure to fire, such as buildings, roads, or tunnels.

[0056] Laboratory tests:

[0057] When studying the fire resistance of concrete mixtures incorporating pig hair fibers, it was found that the dosage that presented the best results in the laboratory tests is that detailed in Table 1, which comprises an amount between 1.5 and 4.5 kg / m3 of pig hair fibers, being 2.5 kg / m 3 the optimal amount for the concrete mix.

[0058] Table 1: Shotcrete mix design. Preferred ranges in brackets and recommended value in parentheses.

[0059] In order to compare the resulting concrete mixes, experimental tests were conducted on three concrete mixes: (1) a control mix without fibers, (2) a mix with polypropylene (PP) fibers, and (3) a mix with pig hair (PH) fibers. The evaluated mixes have the composition shown in Table 1, replacing the pig hair fibers with polypropylene fibers and omitting fibers in the control mix, with water used to compensate for the absorption of the pig hair fibers.

[0060] Fresh state tests:

[0061] Figures 2a and 2b show the results of tests in the fresh (plastic) state related to workability.

[0062] Figure 2a shows the results of an Abrams cone slump test performed according to ASTM C 143 [3]. The control mix exhibited the greatest workability compared to the fiber-reinforced concretes, a common behavior when comparing non-fiber-reinforced and fiber-reinforced concrete. The decrease in slump is due to the increased friction generated by the fibers because of their geometry and morphology. This effect results in higher concrete viscosity, which reduces fluidity and makes handling more difficult during placement and compaction. The PP and PH concretes showed a 59% and 16% decrease in slump, respectively, compared to the control concrete.Concrete with PP (standard industrial fiber) exhibits the greatest loss of workability, which would necessitate the use of more water or plasticizing or superplasticizing admixtures to increase fluidity and achieve a consistency similar to the control mix. However, this would lead to a decrease in mechanical properties and / or higher costs. On the other hand, the slump reduction of the concrete with PH was significantly less, meaning that the need for additional water or admixtures would be much lower, and their negative impact in the hardened state would be reduced. This indicates superior performance of the concrete with PH compared to the concrete with PP in this test.

[0063] Figure 2b shows the diameters obtained in a flow table test of the different concrete mixes, performed according to the specifications of standard UNE-EN 12350-1 [4]. This test provides a clear view of the fluidity and spread of the concrete. The control mix showed the greatest fluidity, a behavior evidenced in the slump test, followed by the mix with PH fiber, while the mix with PP showed the least fluidity. According to the results, it can be seen that the least loss of workability is achieved with the PH fiber, which is a significant positive finding considering the potential challenges associated with handling the mix during its application in reinforced concrete elements.

[0064] Tests in the hardened state:

[0065] Figures 3a and 3b show the results of hardened compressive strength and modulus of elasticity tests of concrete mixtures on cylindrical specimens 10 cm in diameter x 20 cm high, following the ASTM C39 / C39M [5] and ASTM C469 / C469M [6] test standards, respectively. The results in Figures 3a and 3b show mean values ​​in squares, standard deviations (one below and one above the mean) in error bars, and the coefficient of variation (COV) for each concrete type in parentheses (this presentation of results is repeated in Figures 8a to 10). Four specimens per mixture type were used for each compressive strength test, while three specimens per mixture type were used for the modulus of elasticity tests.

[0066] Figure 3a shows the compressive strength obtained for the concrete mixes after 28 days of curing, the standard period accepted for evaluating mechanical properties. The control mix exhibited the highest average compressive strength compared to the fiber-reinforced concretes, where the average decrease in this mechanical property was 15% and 3% for the PP and PH concretes, respectively. It is noteworthy that the loss in the PH concrete was minimal, demonstrating that the use of this fiber does not generate a significant negative effect on this mechanical property, resulting in superior performance compared to the PP concrete. Figure 3b shows a very similar behavior to that observed in compressive strength, with the highest modulus of elasticity in the control concrete, followed by the PH concrete, and finally, the PP concrete.This behavior is due to the fiber's lower stiffness compared to the matrix (cement paste) and aggregates, resulting in nonlinear behavior, as the fibers can deform more than the other materials that make up the concrete. Additionally, the interface between the fiber and the matrix can act as a weak zone, depending on the matrix's quality, thus reducing this mechanical property to a greater or lesser degree. These mechanical tests indicate that the PH fiber exhibits the least negative impact on these properties, even showing no significant reduction in compressive strength or modulus. This result, uncommon in fiber-reinforced concretes, highlights the viability of using pig bristle fibers.

[0067] Fire resistance:

[0068] The fire resistance of the different concretes was re-evaluated 28 days after the mixtures were made and carried out using the methodology proposed by Mugume and Horiguchi [7], called the torch method, who evaluated this property by directly exposing the concrete (cubic specimens of 15 cm x 15 cm x 15 cm) to a gas-fed torch with controlled temperature and exposure time, comparing and validating the results of this method against the standard method indicated by ISO 834 [8].

[0069] For the tests carried out on the concrete mixtures, an improved method was used, where a sacrificial cubic specimen (1) is placed until the flame stabilizes at a certain temperature (800 ±50°C), using an industrial torch (2) at 12 cm from the sacrificial cubic specimen (1), which is monitored by thermocouples (3), laser thermometer and thermographic camera (4), as shown in figure 4a. Once the temperature is stabilized, with the help of a rail, the sacrificial cubic specimen (1) is moved and a cubic specimen of the concrete mixture to be evaluated is placed in its place (5).Once positioned, it is exposed for four minutes, with the aim of generating a uniform distribution of heat on the exposed face of the cubic specimen of the concrete mixture to be evaluated (5), as shown in figure 4b, using four specimens exposed to fire, which were compared with four equivalent specimens not exposed to fire, for each type of concrete mixture.

[0070] Once exposed to fire, each of the concrete mix samples was evaluated: i) Qualitatively for the determination of geometric damage parameters by means of photographic survey of the damage: Figure 5a shows representative damage of the control concrete, while Figure 5b shows representative damage of the concrete with PH, which are much smaller than those of the control concrete.In particular, the positive effect of pig hair fibers on the fire resistance of concrete can be qualitatively appreciated, as there is significantly less damage to the concrete surface, resulting in less mass loss, less detached volume, and less damage depth. This implies greater residual strength of the concrete with pig hair fibers and greater protection of the reinforcement in the case of reinforced concrete. If the steel reinforcement inside the concrete is subjected to high temperatures, this material would show significant reductions in both its strength and stiffness, significantly affecting the structural performance of the reinforced concrete.

[0071] i) Quantitatively, for the determination of geometric damage by quantifying mass loss and scanning to determine damaged area, detached volume, and spalling depth. For this evaluation, the concrete mixtures exposed to fire were scanned using a PICZA 3D laser scanner (Figure 6) (Figure 7a). The images obtained with the laser scanner during the scanning process (Figure 7b) were post-processed in the Autodesk Fusion 360TM [9] and Matlab™

[0010] programs to obtain quantitative estimates of geometric damage parameters, such as areas, detached volumes, and depth (Figure 7c).These computer-aided estimates were compared with measurements using analog instruments (e.g., calipers for concrete spalling depth) and other standard laboratory procedures (e.g., determining spalling volume using the soil density determination procedure, adapting the NCh 1516

[0011] standard for concrete spalling volume). It is important to note that both the computer-aided and standard laboratory procedures yielded equivalent results, with a difference of less than 10% between the two types of measurements. Finally, the data obtained from scanning and post-processing in Autodesk Fusion 360TM [9] and Matlab™

[0010] were statistically evaluated.Figures 8a and 8b show the concrete spalling volume and concrete spalling depth results, respectively. In particular, Figure 8a corresponds to the spalling volume generated on the faces exposed to fire, with an average volume of 62 cm³. 3For the control mixes, these values ​​were approximately zero for the mixes with PP and PH fibers. Similarly, Figure 8b shows that the average spalling depth in the control mixes was 10 mm, but with a wide dispersion, with some values ​​exceeding 15 mm, which is close to the reinforcement in concretes with 20 mm cover. This depth was approximately zero on average for the mixes with PP and PH fibers. This demonstrates the effectiveness of both fiber types in controlling spalling damage. iii) Quantitatively, for the determination of mechanical damage: once the measurements to determine the geometric damage were carried out, the four cubic specimens exposed to fire for each mix type were tested in compression, and their results were compared with four cubic specimens not subjected to fire, for each concrete mix type.The compressive strength tests on cubic specimens were performed following the previous version of NCh 170

[0012] , which specifies the performance of compression tests on cubic specimens. Figures 9a, 9b, and 9c show the compressive strength results for each concrete mix without and with fire exposure, that is, a comparison with its residual strength due to the action of fire.In particular, Figure 9a shows that the control concrete without fire exposure achieved an average compressive strength of 58.8 MPa, with a small variability (VOC of 3.6%), while the same control concrete exposed to fire had an average compressive strength of 48.4 MPa, with a greater dispersion (VOC of 6.2%), and thus, the fire exposure (short period of only 4 minutes) generated a significant reduction of 18% in the average compressive strength between the control concrete without fire and with fire.Figure 9b shows that PP fiber concrete without fire exposure achieved an average compressive strength of 50.3 MPa, with a small variability (VOC of 3.7%), while the same PP concrete exposed to fire had an average compressive strength of 49.4 MPa, with a greater dispersion (VOC of 4.5%), and therefore, fire exposure (short period of only 4 minutes) generated a small reduction of only 1.9% in the average compressive strength between PP concrete without fire and with fire.Finally, Figure 9c shows that the PH fiber-reinforced concrete without fire exposure achieved an average compressive strength of 57.1 MPa, with minimal variability (VOC of 1.8%), while the same PH fiber-reinforced concrete exposed to fire had an average compressive strength of 56.5 MPa, with greater dispersion (VOC of 4.9%). Therefore, the fire exposure (a short period of only 4 minutes) resulted in a very small reduction of only 1.1% in the average compressive strength between the PH fiber-reinforced concrete without fire and the concrete with fire. This confirms the excellent performance of PH fibers in terms of residual strength, complemented by their excellent workability and the very low strength reduction compared to the control concrete not subjected to fire. These results further confirm the excellent overall performance of PH fibers for use as an anti-spalling agent.This summary can be seen in detail in Figure 10, which shows the results for the three types of concrete mixtures (control, with PP and with PH), both without exposure to fire and with exposure to fire.

[0072] REFERENCES

[0073]

[0001] Araya-Letelier, G., Antico, FC, Carrasco, M., Rojas, P., & García-Herrera, CM (2017). Effectiveness of new natural fibers on damage-mechanical performance of mortar. Construction and Building Materials, 152, 672-682.

[0074] [2] Dosque. S., Tulliani, J.M., Chiaia, B., & Antico, F.C. (2023). The Role of Animal Fibers on the Pore Structure of One-Year-Age Concrete. In: Amziane, S., Merta, I., Page, J. (eds) Bio-Based Building Materials. ICBBM 2023. RILEM Bookseries, vol 45. Springer

[0075] [3] ASTM (2020). ASTM C143 / C143M: Standard Test Method for Slump of Hydraulic-Cement Concrete.

[0076] [4] UNE (2020). UNE-EN 12350-1 : Ensayos de hormigón fresco. Parte 1 : Toma de muestras y aparatos comunes.

[0077] [5] ASTM (2023). ASTM C39 / C39M: Standard Test Method for Compressive

[0078] Strength of Cylindrical Concrete Specimens. [6] ASTM (2022). ASTM C469 / C469M: Standard Test Method for Static Modulus of Elasticity and Poisson's Ratio of Concrete in Compression.

[0079] [7] Mugume, R. B., & Horiguchi, T. (2014). Prediction of spalling in fibre-reinforced high strength concrete at elevated temperatures. Materials and structures, 47, 591 - 604.

[0080] [8] ISO (2014). ISO 834: Fire resistance tests. Elements of building construction.

[0081] [9] Autodesk (2023). Autodesk Fusion-Release 2023.

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[0010] MathWorks (2018). MATLAB-Release 2018a.

[0083]

[0011] INN (2010). NCh 1516: Soil mechanics-Determination of density in the ground-Sand cone method.

[0084]

[0012] INN (1985). NCh 170: Concrete-General requirements.

Claims

CLAIMS 1. A high mechanical performance concrete mixture, with a characteristic compressive strength of 35 MPa or higher, which increases fire resistance, preventing or reducing the phenomenon of spalling or explosion of concrete due to fire, when said concrete is exposed to fire or subjected to high temperatures, CHARACTERIZED in that it comprises 280 to 520 kg / m 3 of high-strength cement for high early strength or sprayed concrete; 180 to 300 kg / m 3 of water; 1300 to 1800 kg / m 3 of industrial sand; 70 to 500 kg / m 3 of industrial gravel; 1.1 to 3 kg / m 3 of a water-reducing admixture with retarding effect for concrete; and between 1.5 and 4.5 kg / m 3 made from pig hair fibers.

2. The concrete mixture according to claim 1, CHARACTERIZED in that it comprises 400 kg / m 3of high-strength cement for high early strength or sprayed concrete; 220 kg / m 3 of water; 1591 kg / m 3 of industrial sand; 84 kg / m 3 of industrial gravel; 1.6 kg / m 3 of a water-reducing admixture with retarding effect for concrete; and between 3 kg / m 3 made from pig hair fibers.

3. The concrete mixture according to claims 1 or 2, CHARACTERIZED in that it further comprises 4 to 9.4 kg / m 3 of a high-performance polymer-based superplasticizing additive with a hardening acceleration effect for concrete.

4. The concrete mixture according to claim 3, CHARACTERIZED in that it comprises 6 kg / m 3 of the superplasticizer additive.

5. A pig hair fiber useful for manufacturing a concrete mixture according to any of claims 1 to 4, CHARACTERIZED in that the pig hair fiber is free of any type of organic residue.

6. The pig hair fiber according to claim 5, CHARACTERIZED in that said pig hair fiber has a maximum fiber length size between 20 and 25 mm.

7. The pig hair fiber according to claims 1 to 6, CHARACTERIZED in that said pig hair fiber corresponds to pig hair fibers.

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