A method for improving the performance of a concrete member using a freeze enhancement unit and a concrete member produced thereby

Abstract

The application discloses a method for improving the performance of a concrete member by using a frozen reinforcing unit and a prepared concrete member, and belongs to the technical field of civil engineering. The method is as follows: (1) a frozen reinforcing unit is prepared by using a rapid freezing technology; (2) a stress concentration area of the concrete member is wrapped with at least one frozen reinforcing unit in a frozen state through pouring, and then the frozen reinforcing unit after melting is combined with the concrete member through a hydration reaction through curing. The application fully utilizes the technical advantages that the reinforcing unit has strong crack control ability, and solves the problem of poor interface performance between the embedded reinforcing unit and the post-cast concrete by using the method of freezing and then melting. The reinforcing unit after freezing can be arranged at an ideal position through stress analysis of the member, thereby achieving the technical effect of point targeting improvement, and the mechanical performance of the ordinary concrete member is improved, the plastic damage is reduced, and the bending / shear resistance of the concrete member is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of civil engineering, and particularly relates to a method for improving the performance of a concrete member by using a freezing enhancement unit and a concrete member prepared by the method. BACKGROUND

[0002] Ordinary concrete itself has the characteristics of low tensile strength, poor shear resistance and insufficient toughness, is easily cracked under the combined action of external environment and load, and has the brittle problem that the crack is difficult to control after cracking. Fiber reinforced concrete is a ductile concrete material, and the ultimate strain thereof is increased by several tens of times compared with ordinary concrete. One of the effective ways to improve the cracking of concrete members is to combine fiber concrete and ordinary concrete.

[0003] Fiber reinforced concrete is mainly applied to improve the structural mechanical properties, and the fiber reinforced concrete parts and key structural elements and the fiber concrete reinforcement layer can improve the mechanical properties of concrete. The fiber reinforced structural member shows good failure mode and structural response. By modifying a few crack modes to multiple crack modes, the brittle failure mode of traditional concrete can be prevented. The fiber bridging effect can effectively resist the formation and expansion of cracks, thereby improving the ductility, energy absorption and damage tolerance.

[0004] The existing combination of fiber concrete and ordinary concrete adopts the common combination strengthening method of in-situ pouring, prefabrication or spraying of fiber concrete reinforcement layer, and the bonding properties between the fiber concrete reinforcement layer and the ordinary concrete interface are the key factors for controlling the strengthening efficiency. However, the current enhancement process adopts layered pouring, and there are problems such as complex interface treatment method, bonding performance easily affected by construction, and bonding force to be further improved. The enhancement method of adding fiber reinforced composite materials in concrete needs to remove part of the concrete for slotting enhancement, which causes damage to the whole concrete and makes the failure mode more complex. Therefore, it is of great significance to develop a technology for improving the mechanical properties of concrete, having good interface bonding with concrete and reducing the complexity of construction to improve the performance of concrete members. SUMMARY

[0005] In view of the above problems in the prior art, the application provides a method for improving the performance of a concrete member by using a freezing enhancement unit and a concrete member prepared by the method, so as to improve the crack resistance of the concrete member, reduce the plastic damage of the concrete, improve the toughness of the concrete, and further improve the mechanical properties of the concrete.

[0006] To achieve the above object, the technical scheme adopted by the application to solve the technical problems is:

[0007] The application aims to provide a method for improving the performance of a concrete member, comprising the following steps:

[0008] (1) using the rapid freezing technology to prepare the frozen reinforcing unit;

[0009] (2) by pouring to make the stress concentration area of the concrete member wrap at least one frozen reinforcing unit in the frozen state, and then curing to make the melted frozen reinforcing unit and the concrete member combine through the hydration reaction.

[0010] Further, the process of preparing the frozen reinforcing unit is as follows:

[0011] Before the initial setting of the reinforcing unit, the reinforcing unit is frozen into shape within 60 minutes, and the core temperature is reduced to -40~-10℃.

[0012] Further, the reinforcing unit is Engineered fiber reinforced cementitious composite (ECC).

[0013] Further, the engineering fiber reinforced cement-based composite material is polyvinyl alcohol fiber reinforced concrete or steel fiber reinforced concrete.

[0014] Further, the rapid freezing technology uses liquid nitrogen freezing, dry ice freezing or quick freezing cabinet freezing.

[0015] Further, the frozen reinforcing units are in close contact or have gaps between them.

[0016] Further, the stress concentration area is the tension area or the shear area of the concrete member.

[0017] Further, the distance between the frozen reinforcing units in the shear area should not be greater than 1 / 2 of the height of the concrete.

[0018] Further, the specific process of curing in step (2) is: after pouring, normal curing is performed to make the frozen reinforcing unit naturally melt into a slurry and combine with the concrete member through hydration.

[0019] Further, in step (2), the concrete performance of the frozen reinforcing unit used during pouring is higher than the material performance of the concrete to be improved.

[0020] Another object of the present application is to provide a concrete member prepared by the above method.

[0021] The beneficial effects of the present application are:

[0022] 1. Traditional fiber-reinforced concrete (FRP) component mechanical performance technologies often suffer from insufficient interfacial bonding between fiber reinforcement units and concrete during the process of replacing part of the concrete. This interfacial problem prevents the fiber-reinforced concrete from fully realizing its performance, especially in stress concentration areas, where separation of the fiber reinforcement layer from the concrete can easily occur, failing to achieve the expected reinforcement effect. This invention utilizes rapid freezing technology to prepare frozen fiber reinforcement units, allowing them to bond with the concrete as frozen blocks during the concrete pouring process. When the frozen fiber reinforcement units thaw into a slurry, they can better bond and hydrate with the concrete, forming a strong and tough integrated composite material. This effectively solves the interfacial problem between the fiber-reinforced concrete layer and concrete in traditional technologies. This method not only enhances interfacial bonding but also ensures the stability of the bond, avoiding the material delamination or interfacial gaps that lead to a decline in the mechanical properties of the concrete component in traditional solutions.

[0023] 2. Traditional concrete members are prone to crack propagation in stress concentration areas, leading to a sharp decline in the mechanical properties of the members, especially in flexural and shear strength. To improve these properties, fiber-reinforcing materials (such as steel fibers or polymer fibers) are usually added to the concrete. While these conventional fiber-reinforcing materials can enhance the properties of concrete, their effect on stress concentration areas is not targeted effectively, and the construction is complex and costly to incorporate them across the entire cross-section. This invention significantly improves the performance of concrete members by embedding frozen fiber-reinforcing units into the stress concentration areas of the concrete and then allowing the fiber-reinforcing units to hydrate and react with the concrete through a freeze-to-revive process. The high toughness and crack control capabilities of the added fiber-reinforcing materials effectively inhibit crack propagation in concrete under tensile stress, enhancing the crack resistance, tensile strength, flexural strength, and shear strength of the concrete. Especially in stress concentration areas of concrete members, the embedding of fiber-reinforcing materials can directly improve the strength and ductility of this area, thereby improving the overall crack resistance and mechanical properties of the concrete member.

[0024] 3、Fiber reinforced concrete technology usually uses external wrapping or layered construction to embed fiber reinforced materials into the outside or surface of concrete. When the fiber reinforced material is wrapped outside the concrete, due to the construction factors between the two or the change of environmental temperature, it is easy to cause the gap between the external wrapping material and the concrete, thereby affecting the stability of the whole structure. When the fiber reinforced external wrapping or layered construction method is prone to microcracks, it is easy to be affected by external ultraviolet rays, atmosphere, temperature alternation and other environmental effects, as well as rain erosion medium and other corrosion aging effects, which will cause the aging failure of the fiber, and ultimately affect the mechanical properties of the concrete. Unlike the external fiber reinforced concrete technology, the present application uses the method of built-in fiber reinforced unit, directly embeds the fiber reinforced unit in the stress concentration area of the concrete, and integrates the fiber reinforced unit with the concrete as a whole through the method of freezing and reviving. Since the fiber reinforced unit is built-in the concrete member, it avoids the direct influence of the external environment on the fiber reinforced unit itself, thereby effectively preventing the crack propagation caused by the external fiber reinforcement and the concrete layering problem. In addition, the built-in method can ensure that the fiber reinforcement and the concrete form an integral structure, not only improving the overall mechanical properties of the concrete member, but also avoiding the structural defects in the traditional external wrapping method. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The bending strength detection result diagram of the concrete beam with the built-in frozen reinforced unit prepared for Examples 1-3;

[0026] Figure 2 The bending strength detection result diagram of the concrete beam after the treatment of Example 1 and Comparative Examples 1-4;

[0027] Figure 3 The shear bearing capacity detection result diagram of the concrete beam with the built-in frozen reinforced unit prepared for Examples 4-6;

[0028] Figure 4 The shear bearing capacity detection result diagram of the concrete beam after the treatment of Example 4 and Comparative Examples 5-8;

[0029] Figure 5 The structure schematic diagram of the built-in frozen reinforced unit in the tension area of the concrete beam;

[0030] Figure 6 The structure schematic diagram of the built-in frozen reinforced unit in the shear area of the concrete beam;

[0031] Figure 7 The process flow chart of the present application. DETAILED DESCRIPTION

[0032] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected. Example

[0033] A method for improving the performance of concrete members using cryogenic fiber reinforcement units, the specific process of which is as follows:

[0034] Fiber-reinforced concrete raw materials contain 691 kg / m³ of cement. 3 364 kg / m³ of water 3 565 kg / m³ of fly ash 3 Quartz sand 452kg / m 3 Polycarboxylate superplasticizer 18kg / m 3 The polyvinyl alcohol fiber (PVA) content is 2%, and the water-to-binder ratio is 0.29.

[0035] The prepared fiber-reinforced concrete is poured into a mold and rapidly frozen with liquid nitrogen before initial setting to form a freeze-reinforced unit. The freezing temperature is set to -40℃, and the center temperature of the fiber-reinforced concrete unit reaches -40℃ within 60 minutes to obtain the freeze-reinforced unit.

[0036] Two longitudinal steel bars with a diameter of 16mm are placed at the bottom of the beam mold, and two longitudinal steel bars with a diameter of 8mm are placed at the top of the beam mold. The steel bars are HRB400 grade, the stirrups are HRB335 grade steel bars with a diameter of 8mm, the spacing is 80mm, and the bent-up steel bars are HRB335 grade steel bars with a diameter of 8mm.

[0037] One cryogenic reinforcement unit is placed at the center of the bottom of the tension zone of the beam mold, 45 mm from the side of the concrete beam. The other two cryogenic reinforcement units are placed 60 mm from the bottom of the beam, spaced 110 mm apart. After placing them at the corresponding positions in the tension zone, concrete slurry is quickly poured to fill the beam mold, so that the concrete encapsulates the cryogenic reinforcement units.

[0038] After pouring, use an immersion vibrator to continuously vibrate until the concrete is uniform. After standard curing for 24 hours, demold. During this period, the frozen reinforcement unit naturally melts into a paste and undergoes a hydration reaction to form strength.

[0039] After demolding, the concrete components were cured under standard conditions for 28 days, and tests were conducted to measure the mechanical properties of the components. Example

[0040] A method for improving the performance of concrete members using cryogenic fiber reinforcement units, the specific process of which is as follows:

[0041] Fiber-reinforced concrete raw materials contain 691 kg / m³ of cement. 3 364 kg / m³ of water 3 565 kg / m³ of fly ash 3 Quartz sand 452kg / m 3 Polycarboxylate superplasticizer 18kg / m 3 The polyvinyl alcohol fiber (PVA) content is 2%, and the water-to-binder ratio is 0.29.

[0042] The prepared fiber-reinforced concrete is poured into a mold and rapidly frozen with dry ice before initial setting to form a freeze-reinforced unit. The freezing temperature is set to -20℃, and the center temperature of the fiber-reinforced concrete unit reaches -20℃ within 60 minutes to obtain the freeze-reinforced unit.

[0043] Two longitudinal steel bars with a diameter of 16mm are placed at the bottom of the beam mold, and two longitudinal steel bars with a diameter of 8mm are placed at the top of the beam mold. The steel bars are HRB400 grade, the stirrups are HRB335 grade steel bars with a diameter of 8mm, the spacing is 80mm, and the bent-up steel bars are HRB335 grade steel bars with a diameter of 8mm.

[0044] One cryogenic reinforcement unit is placed at the center of the bottom of the tension zone of the beam mold, 45 mm from the side of the concrete beam. The other two cryogenic reinforcement units are placed 60 mm from the bottom of the beam, spaced 110 mm apart. After placing them at the corresponding positions in the tension zone, concrete slurry is quickly poured to fill the beam mold, so that the concrete encapsulates the cryogenic reinforcement units.

[0045] After pouring, use an immersion vibrator to continuously vibrate until the concrete is uniform. After standard curing for 24 hours, demold. During this period, the frozen reinforcement unit naturally melts into a paste and undergoes a hydration reaction to form strength.

[0046] After demolding, the concrete components were cured under standard conditions for 28 days, and tests were conducted to measure the mechanical properties of the components. Example

[0047] A method for improving the performance of concrete members using cryogenic fiber reinforcement units, the specific process of which is as follows:

[0048] Fiber-reinforced concrete raw materials contain 801 kg / m³ of cement. 3 143 kg / m³ of water 3 100kg / m³ of fly ash 3 Quartz sand 452kg / m 3 Silica fume 100kg / m 3 Polycarboxylate superplasticizer 35kg / m 3 The steel fiber content is 2%, and the water-cement ratio is 0.14.

[0049] The prepared fiber-reinforced concrete is poured into a mold and frozen in a quick-freezing cabinet before initial setting to form a frozen reinforcement unit. The freezing temperature is set to -10℃, and the center temperature of the fiber-reinforced concrete frozen reinforcement unit reaches -10℃ within 60 minutes to obtain the frozen reinforcement unit.

[0050] Two longitudinal steel bars with a diameter of 16mm are placed at the bottom of the beam mold, and two longitudinal steel bars with a diameter of 8mm are placed at the top of the beam mold. The steel bars are HRB400 grade, the stirrups are HRB335 grade steel bars with a diameter of 8mm, the spacing is 80mm, and the bent-up steel bars are HRB335 grade steel bars with a diameter of 8mm.

[0051] One cryogenic reinforcement unit is placed at the center of the bottom of the tension zone of the beam mold, 45 mm from the side of the concrete beam. The other two cryogenic reinforcement units are placed 60 mm from the bottom of the beam, spaced 110 mm apart. After placing them at the corresponding positions in the tension zone, concrete slurry is quickly poured to fill the beam mold, so that the concrete encapsulates the cryogenic reinforcement units.

[0052] After pouring, use an immersion vibrator to continuously vibrate until the concrete is uniform. After standard curing for 24 hours, demold. During this period, the frozen reinforcement unit naturally melts into a paste and undergoes a hydration reaction to form strength.

[0053] After demolding, the concrete components were cured under standard conditions for 28 days, and tests were conducted to measure the mechanical properties of the components. Example

[0054] A method for improving the performance of concrete members using cryogenic fiber reinforcement units, the specific process of which is as follows:

[0055] Fiber-reinforced concrete raw materials contain 691 kg / m³ of cement. 3 364 kg / m³ of water 3 565 kg / m³ of fly ash 3 Quartz sand 452kg / m 3 Polycarboxylate superplasticizer 18kg / m 3 The polyvinyl alcohol fiber (PVA) content is 2%, and the water-to-binder ratio is 0.29.

[0056] The prepared fiber-reinforced concrete slurry is poured into a mold and rapidly frozen with liquid nitrogen before initial setting to form a frozen reinforcement unit. The freezing temperature is set to -40℃, and the center temperature of the fiber-reinforced concrete frozen reinforcement unit reaches -40℃ within 60 minutes to obtain the frozen reinforcement unit.

[0057] Two longitudinal steel bars with a diameter of 16mm are placed at the bottom of the beam mold, and two longitudinal steel bars with a diameter of 8mm are placed at the top of the beam mold. The steel bars are HRB400 grade, the stirrups are HRB335 grade steel bars with a diameter of 8mm, the spacing is 80mm, and the bent-up steel bars are HRB335 grade steel bars with a diameter of 8mm.

[0058] Twelve freeze-strengthened units were symmetrically arranged at a 45° angle on both sides of the shear zone of the beam mold. The spacing between the freeze-strengthened units in each side of the shear zone was 60 mm. After being arranged in the corresponding positions in the shear zone of the beam mold, concrete slurry was quickly poured to fill the beam mold, so that the concrete would wrap around the fiber-reinforced concrete freeze-strengthened units.

[0059] After pouring, use an immersion vibrator to continuously vibrate until the concrete is uniform. After standard curing for 24 hours, demold. During this period, the frozen reinforcement unit naturally melts into a paste and undergoes a hydration reaction to form strength.

[0060] After demolding, the concrete components were cured under standard conditions for 28 days, and tests were conducted to measure the mechanical properties of the components. Example

[0061] A method for improving the performance of concrete members using cryogenic fiber reinforcement units, the specific process of which is as follows:

[0062] Fiber-reinforced concrete raw materials contain 691 kg / m³ of cement. 3 364 kg / m³ of water 3 565 kg / m³ of fly ash 3 Quartz sand 452kg / m 3 Polycarboxylate superplasticizer 18kg / m 3 The polyvinyl alcohol fiber (PVA) content is 2%, and the water-to-binder ratio is 0.29.

[0063] The prepared fiber-reinforced concrete is poured into a mold and rapidly frozen with dry ice before initial setting to form a freeze-reinforced unit. The freezing temperature is set to -30℃, and the center temperature of the fiber-reinforced concrete unit reaches -30℃ within 60 minutes to obtain the freeze-reinforced unit.

[0064] Two longitudinal steel bars with a diameter of 16mm are placed at the bottom of the beam mold, and two longitudinal steel bars with a diameter of 8mm are placed at the top of the beam mold. The steel bars are HRB400 grade, the stirrups are HRB335 grade steel bars with a diameter of 8mm, the spacing is 80mm, and the bent-up steel bars are HRB335 grade steel bars with a diameter of 8mm.

[0065] Twelve freeze-strengthened units were symmetrically arranged at a 45° angle on both sides of the shear zone of the beam, with a spacing of 60 mm between the freeze-strengthened units on each side of the shear zone. After being placed at the corresponding positions in the shear zone of the beam mold, concrete slurry was quickly poured to fill the beam mold, so that the concrete encapsulated the fiber-reinforced concrete freeze-strengthened units.

[0066] After pouring, use an immersion vibrator to continuously vibrate until the concrete is uniform. After standard curing for 24 hours, demold. During this period, the frozen reinforcement unit naturally melts into a paste and undergoes a hydration reaction to form strength.

[0067] After demolding, the concrete components were cured under standard conditions for 28 days, and tests were conducted to measure the mechanical properties of the components. Example

[0068] A method for improving the performance of concrete members using cryogenic fiber reinforcement units, the specific process of which is as follows:

[0069] Fiber-reinforced concrete raw materials contain 801 kg / m³ of cement. 3 143 kg / m³ of water 3 100kg / m³ of fly ash 3 Quartz sand 452kg / m 3 Silica fume 100kg / m 3 Polycarboxylate superplasticizer 35kg / m 3 The steel fiber content is 2%, and the water-cement ratio is 0.14.

[0070] The prepared fiber-reinforced concrete is poured into a mold and frozen in a quick-freezing cabinet before initial setting to form a frozen reinforcement unit. The freezing temperature is set to -10℃, and the center temperature of the fiber-reinforced concrete frozen reinforcement unit reaches -10℃ within 60 minutes to obtain the frozen reinforcement unit.

[0071] Two longitudinal steel bars with a diameter of 16mm are placed at the bottom of the beam mold, and two longitudinal steel bars with a diameter of 8mm are placed at the top of the beam mold. The steel bars are HRB400 grade, the stirrups are HRB335 grade steel bars with a diameter of 8mm, the spacing is 80mm, and the bent-up steel bars are HRB335 grade steel bars with a diameter of 8mm.

[0072] Twelve freeze-strengthened units were symmetrically arranged at a 45° angle on both sides of the shear zone of the beam, with a spacing of 60 mm between the freeze-strengthened units on each side of the shear zone. After being placed at the corresponding positions in the shear zone of the beam mold, concrete slurry was quickly poured to fill the beam mold, so that the concrete encapsulated the fiber-reinforced concrete freeze-strengthened units.

[0073] After pouring, use an immersion vibrator to continuously vibrate until the concrete is uniform. After standard curing for 24 hours, demold. During this period, the frozen reinforcement unit naturally melts into a paste and undergoes a hydration reaction to form strength.

[0074] After demolding, the concrete components were cured under standard conditions for 28 days, and tests were conducted to measure the mechanical properties of the components.

[0075] Compared with Example 1, in this method, the fiber-reinforced concrete slurry is slow-frozen in a freezer at -40°C for 24 hours before initial setting, while the rest is the same as in Example 1.

[0076] Compared with Example 1, in this method, the fiber-reinforced concrete slurry is rapidly frozen with liquid nitrogen before initial setting. The freezing temperature is set to -100℃ and the freezing time is 180 minutes, so that the center temperature of the fiber-reinforced concrete freezing reinforcement unit reaches -100℃. All other aspects are the same as in Example 1.

[0077] Compared with Example 1, in this method, the fiber-reinforced concrete slurry is placed in a standard curing room at 20±2℃ and 95% relative humidity for 7 days to cure and form non-freezing reinforced units. The rest is the same as in Example 1.

[0078] Compared to Example 1, this method uses 2% polyethylene fiber (PE) in the treatment process, while the rest remains the same as in Example 1.

[0079] Compared with Example 4, in this method, the fiber-reinforced concrete slurry is slow-frozen in a freezer at -40°C for 24 hours before initial setting, while the rest is the same as in Example 4.

[0080] Compared with Example 4, in this method, the fiber-reinforced concrete slurry is rapidly frozen with liquid nitrogen before initial setting. The freezing temperature is set to -100℃ and the freezing time is 180 minutes, so that the center temperature of the fiber-reinforced concrete freezing reinforcement unit reaches -100℃. All other aspects are the same as in Example 4.

[0081] Compared with Example 4, in this method, the fiber-reinforced concrete slurry is placed in a standard curing room at 20±2℃ and 95% relative humidity for 7 days to cure and form non-freezing reinforced units. The rest is the same as in Example 4.

[0082] Compared to Example 4, this method uses 2% polyethylene fiber (PE) in the treatment process, while the rest remains the same as in Example 4.

[0083] 1. The effect of fiber-reinforced concrete reinforcing units embedded in concrete as described in Examples 1-3 on the flexural strength of concrete was investigated, with ordinary concrete beams cured according to standard conditions used as a control. The results are shown in [Figure 1]. Figure 1 .

[0084] like Figure 1As shown, after rapid freezing of fiber-reinforced concrete slurry to form reinforcing units, which are directly embedded in the flexural stress concentration zone of the beam, the frozen units melt into slurry and react with the concrete hydration to form an overall strength effect, significantly improving the overall flexural performance of the concrete beam. The reinforcing units can generate numerous microcracks in the tension zone, which are uniformly distributed throughout the material, thus preventing localized failure and effectively distributing the load borne by the concrete. The multi-crack mechanism of the reinforcing units not only delays crack propagation, allowing the structure to withstand greater external loads without brittle fracture, but also improves the overall toughness of the concrete beam. The high toughness of the reinforcing units ensures uniform stress distribution in the tension zone, avoiding localized failure caused by stress concentration in ordinary concrete beams. Furthermore, the fibers can bridge cracks when they occur, preventing further crack propagation; the bridging effect significantly improves the tensile strength and toughness of the material. Moreover, the incorporation of mineral admixtures and polymers improves the density of the cement slurry and the bond strength between the cement and fibers, enhancing the material's mechanical properties and crack control capabilities. This further enhances the flexural strength of concrete, reduces plastic failure, and the strength will further increase with curing time.

[0085] 2. The effect of fiber-reinforced concrete reinforcing units embedded in concrete as described in Examples 4-6 on the shear capacity of concrete was investigated, with ordinary concrete beams cured according to standard conditions used as a control. The results are shown in […]. Figure 2 .

[0086] like Figure 2 As shown, after the liquid nitrogen-frozen fiber-reinforced concrete slurry forming reinforcement units are directly embedded in the shear stress concentration zone of the beam, the frozen units melt into slurry and react with the concrete hydration to form an overall strength effect, significantly improving the shear bearing capacity of the concrete beam. Ordinary concrete beams are prone to shear failure under shear force due to the formation of diagonal cracks in the shear zone, typically a single main crack that propagates diagonally along the shear zone. Fiber-reinforced units, however, generate multiple uniformly distributed microcracks in the shear zone through their unique microcrack formation mechanism. These microcracks effectively disperse shear force, preventing the propagation of localized cracks and resulting in better crack control under shear. The fibers connect the materials on both sides of the crack through bridging, effectively preventing further crack propagation. This crack bridging effect effectively improves the beam's shear strength and ductility, enabling it to withstand greater shear force and avoiding shear failure due to crack propagation.

[0087] 3. The flexural strength of the concrete specimens in the technical solutions described in Example 1 and Comparative Examples 1-4 was tested, and the shear capacity of the concrete specimens in the technical solutions described in Example 4 and Comparative Examples 5-8 was tested, with ordinary concrete beams cured according to standard as a control. The results are as follows: Figure 3 , 4 As shown.

[0088] like Figure 3 , 4 As shown, compared to the technical solutions described in Comparative Examples 1-8, the technical solutions described in Examples 1 and 4 of this application enable concrete specimens to exhibit better flexural / shear bearing capacity and toughness. The reason for this is:

[0089] Compared to the technical solution of this application, Comparative Examples 1 and 5 employ a slow-freezing method to form fiber-reinforced concrete slurry into blocks. During this process, the temperature drops more slowly during freezing, allowing sufficient time for moisture to migrate and aggregate, forming larger ice crystals. These large ice crystals cause greater damage to the internal structure of the fiber-reinforced concrete matrix, generating large microcracks and fissures. Furthermore, the slow freezing process leads to incomplete hydration of the fiber-reinforced concrete, resulting in insufficient and uneven distribution of hydration products. The thawed cement particles exhibit amorphous or loose hydration products, leading to insufficient toughness in the fiber-reinforced concrete.

[0090] Compared to the technical solution of this application, Comparative Examples 2 and 6, which use a freezing temperature of -100℃ and a freezing time of 180 minutes to form frozen blocks with fiber-reinforced concrete, exhibit a different approach. When the freezing temperature drops to -100℃, the water in the cementitious material slurry freezes rapidly, generating a large number of ice crystals. The formation of ice crystals is governed by ice nucleation and growth mechanisms, with ice crystals growing more rapidly and larger at extremely low temperatures. The formation of ice crystals occupies a certain space in the slurry, and after thawing, these areas form voids, reducing the material's density and strength. Extending the freezing time to 180 minutes causes microcracks to form on the fiber surface due to ice crystal compression, reducing the interfacial bonding force between the fiber and the matrix. Furthermore, the irregular microstructure formed by cement hydration products at excessively low temperatures further weakens the interfacial bonding performance. Both excessively low freezing temperatures and excessively long freezing times can lead to localized rapid thawing during the freezing process, resulting in excessively rapid hydration reactions in some areas. Other parts may not fully react due to slow thawing and structural damage caused by ice crystals, leading to uneven performance. CSH gels formed at extremely low temperatures exhibit irregular morphology and lack coherence, making it difficult to provide good strength and toughness.

[0091] Compared to the technical solution of this application, Comparative Examples 3 and 7 use fiber-reinforced concrete embedded in the concrete after 7 days of standard curing. The surface of the 7-day-cured fiber-reinforced concrete has already undergone a hydration reaction, generating a certain amount of hydration product CSH, while the freshly poured C30 concrete is still in the rapid hydration stage. The uneven hydration reaction at the interface leads to stress concentration, which easily triggers the generation and propagation of interfacial microcracks. Secondly, the reduced surface active components of the fiber-reinforced concrete make it difficult to form new chemical bonding products between the two types of concrete poured at different times, resulting in insufficient interfacial chemical stability. This leads to insufficient physical bonding and chemical stability at the interface between the fiber-reinforced concrete unit and the freshly poured C30 concrete, with significant hydration differences affecting the adhesion between the concretes. The two types of concrete cannot bond well, easily leading to interfacial cracks that affect the overall mechanical properties.

[0092] Compared to the technical solution of this application, Comparative Examples 4 and 8 use polyethylene fibers (PE) to prepare fiber-reinforced concrete paste. Under the extremely low temperature environment of liquid nitrogen, the molecular chain movement in the polyethylene fibers is almost completely frozen, significantly reducing the material's flexibility and exhibiting more brittle behavior. This further induces the propagation of microcracks or defects within the fibers, thereby reducing tensile strength and fracture strength. Furthermore, liquid nitrogen freezing rapidly alters the crystallinity of the PE fibers, causing the amorphous regions to become more brittle, thus affecting the fiber's ductility and energy absorption capacity. The excessive temperature difference introduces internal residual stress, which also affects the fatigue resistance and long-term load-bearing capacity of the PE fibers, leading to insufficient toughness in the fiber-reinforced concrete and a decline in the overall mechanical properties of the concrete.

[0093] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for improving the performance of concrete components using cryogenic reinforcement units, characterized in that, Includes the following steps: (1) The freezing enhancement unit was prepared using rapid freezing technology; the preparation process of the freezing enhancement unit was as follows: Within 60 minutes, the reinforcing unit is frozen and molded, and its core temperature is reduced to -40~-10℃; the reinforcing unit is an engineering fiber reinforced cement-based composite material. (2) By pouring, at least one frozen reinforcement unit in a frozen state is wrapped around the stress concentration area of ​​the concrete component, and then the frozen reinforcement unit after melting is bonded to the concrete component through hydration reaction by curing.

2. The method according to claim 1, characterized in that, Rapid freezing technology uses liquid nitrogen freezing, dry ice freezing, or blast freezers.

3. The method according to claim 1, characterized in that, The freezing enhancement units are either fitted together or have gaps between them.

4. The method according to claim 1, characterized in that, The specific process of curing in step (2) is as follows: After the pouring is completed, normal curing is carried out to allow the freeze-strengthening unit to melt into a slurry and combine with the concrete component through hydration.

5. The method according to claim 1, characterized in that, In step (2), the concrete properties of the freeze-strengthened unit used during pouring are higher than the material properties of the concrete to be enhanced.

6. A concrete component, characterized in that, It is prepared by the method described in any one of claims 1 to 5.

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