Carbon-reducing ultra-fast concrete composition containing biochar and concrete road repair method using the same

Abstract

The present invention relates to a carbon-reducing ultra-rapid hardening concrete composition containing biochar and a method for repairing concrete roads using the same. More specifically, the carbon-reducing ultra-rapid hardening concrete composition comprises ultra-rapid hardening cement, activated silica, liquid latex, sand, steel slag powder, biochar, and purified water. The ultra-fast hardening concrete composition composed of the above components exhibits rapid early strength and high freeze-thaw resistance, which suppresses deterioration and cracking, and not only has excellent compressive strength and flexural strength, but also exhibits a carbon reduction effect.

Description

Technology Field

[0001] The present invention relates to a carbon-reducing ultra-fast hardening concrete composition containing biochar and a method for repairing concrete roads using the same. More specifically, the invention relates to a carbon-reducing ultra-fast hardening concrete composition containing biochar that exhibits rapid initial strength, high freeze-thaw resistance to suppress deterioration and cracking, excellent compressive strength and flexural strength, as well as a carbon reduction effect, and a method for repairing concrete roads using the same. Background Technology

[0003] Concrete is one of the most widely used construction and civil engineering materials worldwide, and is essential for structures such as roads, bridges, ports, and buildings.

[0004] However, the cement manufacturing process, particularly the high-temperature calcination of limestone and clay, emits a significant amount of carbon dioxide, and as a result, the cement industry is identified as one of the major causes of global greenhouse gas emissions.

[0005] Therefore, technologies to reduce carbon emissions generated during the production of cement and concrete are recognized as a very important task from environmental and social perspectives.

[0006] Meanwhile, infrastructure structures such as roads and bridges require rapid maintenance and the prompt reopening of repaired structures in the event of damage caused by accidents or aging. To meet these requirements, ultra-rapid hardening concrete, which enables rapid short-term strength development, is primarily used. However, while conventional ultra-rapid hardening concrete is advantageous for securing short-term strength, it fails to provide sufficient performance in terms of long-term durability, crack resistance, freeze-thaw resistance, and environmental sustainability. Furthermore, when using only existing additives or auxiliary materials, there was a problem in that it was difficult to simultaneously satisfy ultra-rapid hardening performance, durability, and carbon reduction effects.

[0007] Therefore, there is an urgent need to develop a concrete composition capable of simultaneously improving ultra-rapid setting performance and structural durability while reducing carbon emissions, as well as a concrete road repair method using the same. Prior art literature

[0009] Korean Registered Publication No. 10-1140561 (April 20, 2012) Korean Registered Publication No. 10-1409447 (June 12, 2014) The problem to be solved

[0010] The objective of the present invention is to provide a carbon-reducing ultra-fast hardening concrete composition containing biochar that exhibits rapid initial strength, high freeze-thaw resistance to suppress deterioration and cracking, excellent compressive strength and flexural strength, as well as a carbon reduction effect, and a method for repairing concrete roads using the same. means of solving the problem

[0012] The objective of the present invention can be achieved by providing a carbon-reducing ultra-rapid hardening concrete composition comprising biochar, which includes ultra-rapid hardening cement, activated silica, liquid latex, sand, steel slag powder, wood-based biochar, and purified water.

[0013] According to a preferred feature of the present invention, the carbon-reducing ultra-rapid hardening concrete composition containing the biochar may comprise 10 to 20 weight% of ultra-rapid hardening cement, 0.5 to 1 weight% of active silica, 1 to 5 weight% of liquid latex, 20 to 30 weight% of sand, 30 to 40 weight% of steel slag powder, 1 to 5 weight% of wood-based biochar, and the remainder being purified water.

[0014] According to a more preferred feature of the present invention, the steelmaking slag powder may be manufactured by storing it in a storage yard for 3 to 10 months and then grinding it to a particle size of 0.1 to 5 millimeters.

[0015] According to a more preferred feature of the present invention, the wood-based biochar has a carbon content of 70 to 90 mass%, a pyrolysis temperature of 500 to 700°C, and a specific surface area of ​​100 to 400 m² 2 It could be / g.

[0016] According to a more preferred feature of the present invention, the carbon-reducing ultra-fast hardening concrete composition containing the biochar may further include 0.1 to 1 weight percent of an alumina-based additive.

[0017] According to a more preferred feature of the present invention, the alumina-based additive may comprise one or more selected from the group consisting of aluminum hydroxide, tricalcium aluminate, high-alumina fly ash, and bauxite.

[0019] In addition, the objective of the present invention can also be achieved by providing a concrete road repair method using a carbon-reducing ultra-fast hardening concrete composition containing biochar, which includes the process of laying the carbon-reducing ultra-fast hardening concrete composition containing biochar on a cross-section of a road that has been paved, leveled, and dried. Effects of the invention

[0021] The carbon-reducing ultra-rapid hardening concrete composition containing biochar according to the present invention and the concrete road repair method using the same exhibit rapid initial strength, high freeze-thaw resistance which suppresses deterioration and cracking, excellent compressive strength and flexural strength, as well as carbon reduction effects, and provide an excellent effect of providing an ultra-rapid hardening concrete composition and a concrete road repair method using the same. Brief explanation of the drawing

[0023] Figure 1 is a photograph showing the appearance of wood-based biochar included in a carbon-reducing ultra-fast hardening concrete composition containing biochar according to the present invention. Specific details for implementing the invention

[0024] Hereinafter, preferred embodiments of the present invention and the physical properties of each component are described in detail. This description is intended to be sufficient for a person skilled in the art to easily practice the invention, and does not imply that the technical scope and concept of the present invention are limited thereby.

[0026] The carbon-reducing ultra-rapid hardening concrete composition containing biochar according to the present invention comprises ultra-rapid hardening cement, activated silica, liquid latex, sand, steel slag powder, wood-based biochar, and purified water, and preferably comprises 10 to 20 weight% of ultra-rapid hardening cement, 0.5 to 1 weight% of activated silica, 1 to 5 weight% of liquid latex, 20 to 30 weight% of sand, 30 to 40 weight% of steel slag powder, 1 to 5 weight% of wood-based biochar, and the remainder being purified water.

[0028] The above ultra-rapid hardening cement is included in an amount of 10 to 20 weight percent and plays a major role in rapidly developing the initial strength of concrete, and by securing sufficient strength of the structure immediately after construction, it enables rapid maintenance and opening of infrastructure structures such as roads and bridges.

[0029] Furthermore, the aforementioned ultra-rapid hardening cement exhibits a rapid hydration reaction rate and excellent exothermic properties, which suppress crack formation through interaction with liquid latex, activated silica, and biochar; contribute to the improvement of initial and short-term compressive strength; and demonstrate the effect of improving long-term durability and stability by controlling the formation of micropores within the concrete.

[0030] If the content of the above ultra-rapid hardening cement is less than 10 weight%, the hydration reaction does not occur sufficiently, resulting in a delayed development of initial strength and making it difficult to open roads and bridges quickly during repairs, and the crack suppression effect and long-term durability of the concrete may also be reduced. If the content of the above ultra-rapid hardening cement exceeds 20 weight%, excessive heat generation and rapid shrinkage occur, increasing the risk of cracking in the concrete, and the interaction with biochar and other admixtures becomes unbalanced, which may impair the development of long-term strength and the effect of improving durability, so it is undesirable.

[0032] In addition, the above-mentioned active silica is included in an amount of 0.5 to 1 weight% and is silica that has been finely ground to exhibit high reactivity; unlike ordinary silica, it exhibits the characteristic of being able to react actively chemically and physically within cement or concrete, having a specific gravity of 2.5 to 2.7 and a fineness of 3100 to 3900 cm⁻¹ 2 It is preferable to use one with a loss on ignition of 2 to 6% and a weight of 1 / g.

[0033] Active silica exhibiting the above properties performs a pozzolanic reaction with calcium hydroxide generated during the cement hydration process to form additional calcium silicate hydrate (CSH), thereby improving the compressive strength and long-term strength of concrete. Furthermore, it fills micropores to enhance watertightness and suppress crack formation, while also acting in conjunction with ultra-rapid hardening cement to promote the development of early strength.

[0034] If the content of the active silica is less than 0.5 weight%, the pozzolanic reaction with calcium hydroxide does not occur sufficiently during the cement hydration process, which reduces the effect of improving the long-term compressive strength and durability of the concrete, and the effect of filling micropores is insufficient, which may limit the suppression of crack formation and improvement of watertightness. If the content of the active silica exceeds 1 weight%, the workability of the concrete mixture is reduced due to excessive pozzolanic reaction and the addition of fine particles, the risk of cracking increases due to rapid shrinkage, and an imbalance in heat generation and the initial hardening process during the cement hydration process may be caused, which is undesirable because it may hinder the development of early strength of ultra-rapid hardening concrete.

[0036] In addition, the above liquid latex is preferably used in an amount of 1 to 5 weight percent and has a solid content of 40 to 50 percent. When mixed with cement, it is uniformly dispersed within the concrete to form a fine latex film, thereby filling the micropores of the concrete, mitigating shrinkage caused by moisture evaporation, and suppressing the occurrence of cracks.

[0037] Furthermore, the liquid latex improves the flexibility of the concrete surface and interior, thereby enhancing resistance to impact and external forces. It also increases watertightness and improves durability, and interacts with other admixtures such as ultra-rapid hardening cement and activated silica to simultaneously improve early strength development and long-term structural stability.

[0038] If the content of the liquid latex is less than 1 weight%, a uniform latex film is not sufficiently formed inside the concrete, which reduces the effect of filling micropores, lowers the effect of suppressing shrinkage and cracking caused by moisture evaporation, and may also limit the effect of improving impact resistance and watertightness. If the content of the liquid latex exceeds 5 weight%, the workability of the concrete mixture is reduced, and the interaction with the cement hydration process is uneven, which may delay the development of early strength or increase the possibility of cracking, and the long-term strength and durability of the concrete structure may be compromised due to excessive flexibility, so it is undesirable.

[0040] In addition, the above sand is preferably included in an amount of 20 to 30 weight percent and has a particle size of 0.1 to 2.0 mm, and acts as a major aggregate that forms the framework of concrete together with cement, activated silica, liquid latex and steel slag powder, etc.

[0041] In addition, the sand secures volume within the concrete and improves compressive strength and structural stability by filling micropores when mixed with cement paste; when equipped with an appropriate particle distribution, it maintains the workability of the concrete mixture and improves constructability; and it plays a role in providing overall volumetric stability during the rapid hardening process of ultra-rapid hardening concrete, suppressing crack formation, and ensuring long-term durability.

[0042] If the sand content is less than 20 weight%, the internal framework of the concrete is not sufficiently formed, which lowers compressive strength and structural stability, and the micro-pore filling effect is insufficient, which increases the possibility of cracking and may reduce workability and constructability. If the sand content exceeds 30 weight%, the fluidity of the concrete mixture is reduced, which lowers workability, and the bonding strength with cement and other admixtures is weakened, which may hinder the development of early and long-term strength, and cracking may occur during the rapid hardening process characteristic of ultra-rapid hardening concrete, so this is not desirable.

[0044] In addition, the above steel slag powder is included in an amount of 30 to 40 weight percent and is preferably used after being stored in a stockpile for 3 to 10 months and then crushed to a particle size of 0.1 to 5 millimeters. It acts as a major aggregate in concrete, and at the same time, some reactive components are activated during the cement hydration process to improve long-term strength, and it plays a role in improving compressive strength, durability, and crack resistance by providing volumetric stability to the concrete mixture and filling micropores.

[0045] In addition, the steel slag powder interacts with ultra-rapid hardening cement, activated silica, and liquid latex while maintaining the workability of concrete, exhibiting the effect of simultaneously improving early strength development and long-term structural stability.

[0046] In addition, steel slag is a byproduct generated during the steelmaking process and contains some free lime (CaO) and magnesia (MgO) that can cause expansion within concrete over the long term by reacting with moisture and carbonates and sulfates in the air in its initial state. As in the present invention, by stacking steel slag in a storage yard for 3 to 10 months to undergo a natural weathering and maturation process, the free lime and magnesia inside react with moisture in the air and stabilize, thereby reducing long-term expansion and ensuring volumetric stability of the concrete structure.

[0047] In addition, when sufficiently matured steel slag is subsequently ground to a particle size of 0.1 to 5 millimeters, the particle surface area increases, allowing it to be uniformly mixed with cement and other admixtures within concrete, and by filling micropores and providing volumetric stability as an aggregate, it exhibits an effect that contributes to improving compressive strength and durability.

[0048] Furthermore, steel slag powder produced through these maturation and grinding processes interacts with ultra-rapid hardening cement, activated silica, and liquid latex to simultaneously improve early strength development and long-term structural stability.

[0049] If the content of the steel slag powder is less than 30 weight%, the pozzolanic reaction is insufficient, which reduces long-term strength and durability, and the amount of cement used increases relatively, which reduces the carbon dioxide reduction effect and may increase the initial heat of hydration. If the content of the steel slag powder exceeds 40 weight%, the initial strength is delayed due to the slow hydration of the steel slag, microcracks may occur due to reaction imbalance, and the viscosity of the concrete mixture increases excessively, which reduces workability and may cause expansion problems in the long term, so it is not desirable.

[0051] In addition, the wood-based biochar comprises 1 to 5 weight%, has a carbon content of 70 to 90 mass%, a pyrolysis temperature of 500 to 700°C, and a specific surface area of ​​100 to 400 m² 2 It is desirable to use a material with a value of 1 / g. Wood-based biochar exhibiting the above properties fills micropores within the concrete mixture to reduce porosity and improve watertightness. It also improves strength development and durability by controlling internal moisture and cement hydration byproducts through physical and chemical adsorption. Furthermore, due to its high-carbon biochar characteristics, it partially replaces cement usage to reduce carbon dioxide emissions, while simultaneously contributing to long-term crack suppression and improved thermal stability.

[0052] If the content of the wood-based biochar is less than 1 weight%, the micropore filling and adsorption functions are insufficient, which limits the effect of improving the watertightness and long-term strength of the concrete and may reduce the carbon dioxide reduction effect. If the content of the wood-based biochar exceeds 5 weight%, the viscosity of the concrete mixture increases excessively, which lowers workability, and the hydration reaction proceeds unevenly, which lowers the initial strength of the concrete and may cause microcracks or shrinkage and expansion problems in the long term, so it is undesirable.

[0054] In addition, the carbon-reducing ultra-rapid hardening concrete composition containing biochar according to the present invention may further include 0.1 to 1 weight percent of an alumina-based additive. When the alumina-based additive is further included as described above, it promotes the initial bonding rate in the cement hydration reaction to improve ultra-rapid hardening strength, forms a dense microstructure to improve watertightness and durability, and improves resistance to external attacks such as sulfates, while simultaneously suppressing expansion or cracking of the concrete surface.

[0055] At this time, it is preferable that the alumina-based additive comprises one or more selected from the group consisting of aluminum hydroxide, tricalcium aluminate, high-alumina fly ash, and bauxite.

[0056] The above aluminum hydroxide (Al(OH)3) releases aluminum ions during the cement hydration process to accelerate the initial bonding rate, densifies the microstructure to improve watertightness and durability, and plays a role in mitigating heat generation through an endothermic action during hydration and suppressing expansion or crack formation.

[0057] In addition, the tricalcium aluminate (C3A) has rapid hydration characteristics, which promotes the development of early strength, and reacts with sulfates to form stable ettringite, thereby controlling expansion cracks and improving the chemical resistance and early strength stability of concrete.

[0058] In addition, the above-mentioned high alumina fly ash (HAFA) has pozzolanic properties, which contribute to improving long-term strength and reducing porosity, increasing chemical resistance, and controlling heat generation during the hydration process to stabilize the initial heat of hydration.

[0059] In addition, the bauxite mentioned above is rich in aluminum oxide, which promotes the hydration reaction and forms a dense microstructure within the concrete, thereby improving watertightness and durability, and enhancing resistance to external chemicals such as sulfate attack.

[0060] If the content of the above alumina-based additive is less than 0.1 weight%, the effects of promoting the initial bonding speed and densifying the microstructure are not sufficiently exhibited, which limits the improvement of ultra-fast hardening strength and durability, and may result in insufficient effects of suppressing expansion and cracking. If the content of the above alumina-based additive exceeds 1 weight%, the hydration reaction proceeds unevenly due to the excessive supply of alumina, which hinders the development of initial and long-term strength, and the viscosity of the mixture increases excessively, leading to reduced workability. In some cases, the formation of excessive ettringite may cause microcracks or expansion problems in the long term, which is undesirable.

[0062] A carbon-reducing ultra-fast hardening concrete composition containing biochar made of the above components can be used to repair concrete roads by laying it on the cross-section of a road that has been paved, leveled, and dried. At this time, the depth of the pavement cutting is preferably 30 to 50 mm (adjustable according to the depth of damage), the allowable range of surface irregularity after leveling is preferably ±2 millimeters, and the surface moisture after drying is preferably maintained at 3% or less.

[0063] In addition, it is preferable that the laying thickness be approximately 50 millimeters, and the laying speed be 5 to 10 m2 It is desirable to indicate / min (standard for pump or ready-mix concrete application).

[0065] Hereinafter, a method for manufacturing a carbon-reducing ultra-rapid hardening concrete composition containing biochar according to the present invention and the physical properties of the carbon-reducing ultra-rapid hardening concrete composition manufactured by said method will be explained with reference to examples.

[0067] <Preparation Example 1> Preparation of steelmaking slag powder

[0068] Steel slag powder was produced by storing steel slag in a storage yard at room temperature for 6 months, then feeding it into a crushing device and crushing it to a particle size of 2.5 millimeters.

[0070] <Preparation Example 2> Preparation of an alumina-based additive

[0071] An alumina-based additive was prepared by mixing 100 parts by weight of aluminum hydroxide, 50 parts by weight of tricalcium aluminate, 50 parts by weight of high-alumina fly ash, and 10 parts by weight of bauxite.

[0073] <Example 1>

[0074] 15 wt% ultra-rapid hardening cement, 0.75 wt% activated silica, 3 wt% liquid latex, 25 wt% sand, 35 wt% steel slag powder prepared through Preparation Example 1 above, and wood-based biochar (carbon content of 70 to 90 mass%, pyrolysis temperature of 500 to 700℃, and specific surface area of ​​100 to 400 m² 2 A carbon-reducing ultra-fast hardening concrete composition containing biochar was prepared by adding 2.5% by weight (g) to a mixer and stirring at a speed of 200 rpm for 10 minutes, then adding the remaining amount of purified water and stirring at a speed of 200 rpm for 10 minutes.

[0076] <Example 2>

[0077] A carbon-reducing ultra-rapid hardening concrete composition containing biochar was prepared by proceeding in the same manner as in Example 1 above, but including 15 wt% ultra-rapid hardening cement, 0.5 wt% active silica, 1 wt% liquid latex, 25 wt% sand, 30 wt% steel slag powder prepared through Preparation Example 1 above, 1 wt% wood-based biochar, and the remainder being purified water.

[0079] <Example 3>

[0080] A carbon-reducing ultra-rapid hardening concrete composition containing biochar was prepared by proceeding in the same manner as in Example 1 above, but including 15 wt% ultra-rapid hardening cement, 1 wt% activated silica, 5 wt% liquid latex, 25 wt% sand, 40 wt% steel slag powder, 5 wt% wood-based biochar, and the remainder being purified water.

[0082] <Example 4>

[0083] A carbon-reducing ultra-fast hardening concrete composition containing biochar was prepared by proceeding in the same manner as in Example 1 above, but further including 0.5 weight% of the alumina-based additive prepared through Preparation Example 2 above.

[0085] <Example 5>

[0086] A carbon-reducing ultra-fast hardening concrete composition containing biochar was prepared by proceeding in the same manner as in Example 2 above, but further including 0.5 weight% of the alumina-based additive prepared through Preparation Example 2 above.

[0088] <Example 6>

[0089] A carbon-reducing ultra-fast hardening concrete composition containing biochar was prepared by proceeding in the same manner as in Example 3 above, but further including 0.5 weight% of the alumina-based additive prepared through Preparation Example 2 above.

[0091] <Comparative Example 1>

[0092] The process was carried out in the same manner as in Example 1 above, but general steel slag was mixed and a wood-based biochar was not mixed to produce an ultra-fast hardening concrete composition.

[0094] <Comparative Example 2>

[0095] The process was carried out in the same manner as in Example 1 above, but general steel slag was mixed to produce a carbon-reducing ultra-fast hardening concrete composition containing biochar.

[0097] <Experimental Example 1> Measurement of Physical Properties of Ultra-Rapid Hardening Concrete Composition

[0098] The compressive strength, flexural strength, permeability test, freeze-thaw resistance, and adhesion strength of the ultra-rapid hardening concrete compositions prepared through Examples 1 to 6 and Comparative Examples 1 to 2 were measured and are shown in Table 1 below.

[0099] {However, compressive strength was measured using the test methods of KS F 2405, flexural strength using KS F 2408, permeability test using KS F 4916, freeze-thaw resistance using KS F 2456, and bond strength using KS F 4716.}

[0100]

[0101]

[0103] <Experimental Example 2> Measurement of Carbon Reduction Effect of Ultra-Rapid Hardening Concrete Composition

[0104] The carbon reduction rate of the ultra-rapid hardening concrete compositions prepared through Examples 1 to 6 and Comparative Example 1 above was measured and is shown in Table 2 below.

[0105] [However, the carbon reduction rate was calculated using the ASTM C1910 test method and the following formula.

[0106] Carbon Reduction Rate (%) = {(CO2 emissions of standard concrete - CO2 emissions of concrete including biochar) / CO2 emissions of standard concrete} × 100]

[0107] Table 2

[0108]

[0109] As shown in Table 2 above, it can be seen that the carbon-reducing ultra-rapid hardening concrete composition containing biochar prepared through Examples 1 to 6 of the present invention has a superior carbon reduction effect compared to the ultra-rapid hardening concrete composition prepared through Comparative Example 1.

[0111] Accordingly, the carbon-reducing ultra-rapid hardening concrete composition containing biochar according to the present invention and the concrete road repair method using the same provide an ultra-rapid hardening concrete composition and a concrete road repair method using the same that exhibits rapid initial strength, suppresses deterioration and cracking due to high freeze-thaw resistance, has excellent compressive strength and flexural strength, and also exhibits a carbon reduction effect.

Claims

Claim 1 A carbon-reducing ultra-rapid hardening concrete composition containing biochar, comprising 10 to 20 weight% of ultra-rapid hardening cement, 0.5 to 1 weight% of activated silica, 1 to 5 weight% of liquid latex, 20 to 30 weight% of sand, 30 to 40 weight% of steel slag powder, 1 to 5 weight% of wood-based biochar, and the remainder being purified water, wherein the steel slag powder is crushed to a particle size of 0.1 to 5 millimeters after being stockpiled in a storage yard for 3 to 10 months. Claim 2 Delete Claim 3 delete Claim 4 In claim 1, the wood-based biochar has a carbon content of 70 to 90 mass%, a pyrolysis temperature of 500 to 700°C, and a specific surface area of ​​100 to 400 m² 2 Carbon-reducing ultra-fast setting concrete composition containing biochar, which is / g. Claim 5 A carbon-reducing ultra-rapid hardening concrete composition containing biochar according to claim 1, wherein the carbon-reducing ultra-rapid hardening concrete composition containing biochar further comprises 0.1 to 1 weight% of an alumina-based additive. Claim 6 A carbon-reducing ultra-fast setting concrete composition containing biochar, wherein the alumina-based additive of claim 5 comprises one or more selected from the group consisting of aluminum hydroxide, tricalcium aluminate, high-alumina fly ash, and bauxite. Claim 7 A method for repairing a concrete road using a carbon-reducing ultra-fast hardening concrete composition containing biochar, comprising the process of laying the carbon-reducing ultra-fast hardening concrete composition containing biochar according to any one of claims 1 and 4 to 6 on a cross-section of a road that has been paved, leveled, and dried.

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