Method for enhancing surface mineralization hardening of large precast components

Abstract

The present invention belongs to the technical field of precast component production, and discloses a method for enhancing the surface mineralization and hardening of large precast components, which includes the following steps: Step 1, process a number of micropores on the steel formwork for pouring large precast components. The micropores are uniformly arranged on the steel formwork, and use the processed steel formwork for assembling the mold; Step 2, after the steel bars are tied, fix them in the mold, set the poured concrete together with the mold on the vibrating table and vibrate it by the vibrating table, and spray carbon dioxide gas into the surface layer of the concrete. Step 3, after vibration compaction, perform standard curing or steam curing with the mold on the large precast component. Step 4, spray a surface strengthening agent liquid on the surface of the large precast component, and then carry out a mineralization reaction in an autoclave. Step 5, immerse the large precast component after autoclaving in saturated lime water for curing to a certain age. The present invention is beneficial to improving the carbonization uniformity of the surface layer of concrete and increasing the formation efficiency of the carbonized layer.

Description

Technical Field

[0001] The present invention belongs to the technical field of precast component production, and particularly relates to a method for enhancing surface mineralization hardening of large precast components. Background Art

[0002] Large precast components mostly adopt reinforced concrete structures. Concrete itself is alkaline, which can form a passivation layer on the surface of steel bars to avoid steel bar corrosion. During the production process, in order to accelerate the hardening of concrete, increase its strength, and fix carbon dioxide, mineralization technology is generally used to mineralize the concrete to a certain extent. The mineralization process will cause the alkalinity of the concrete to decrease, increasing the risk of steel bar corrosion to a certain extent. Therefore, it is necessary to enhance the surface of the concrete component during the mineralization process and improve the density of the mineralized layer, so as to slow down the intrusion of harmful ions during the service process of the component and ensure the durability of reinforced concrete.

[0003] Currently, in the prior art, most methods involve filling the space where the component is located with carbon dioxide during the curing process to allow the surface of the concrete to come into contact with carbon dioxide for mineralization reaction. Some techniques drill holes in the mold surface, then spray carbonated water or calcium bicarbonate solution on the permeable formwork cloth, cover the mold surface with the permeable formwork cloth, and let the surface of the component react with the liquid on the permeable formwork cloth to achieve mineralization, while carbon dioxide is filled on the outside to supplement carbon dioxide for the solution on the permeable formwork cloth. However, all the above prior art methods only allow carbon dioxide to contact the surface of the component and gradually penetrate into the outside of the component for reaction to form a mineralized layer. Therefore, the diffusion rate of carbon dioxide in the concrete is relatively slow, and under static conditions, a carbonate film layer will form on the surface of the component, further hindering the penetration of carbon dioxide. Therefore, the prior art not only has a low mineralization efficiency but also is difficult to form a relatively thick mineralized layer, generally 0.5 - 6 mm. If large components have higher requirements for impermeability, frost resistance, and corrosion resistance, the prior art is difficult to quickly form a relatively thick and dense mineralized layer, and the carbon fixation efficiency is also very low. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for enhancing surface mineralization hardening of large precast components, which is used to solve the technical problem that in the prior art, due to the slow diffusion of carbon dioxide in concrete, it is difficult to achieve a high mineralization efficiency, especially difficult to quickly form a dense mineralized layer with a certain depth on the surface of the concrete.

[0005] The method for enhancing surface mineralization hardening of the large precast component includes the following steps.

[0006] Step 1: Process a number of micro-holes on the steel formwork for casting large precast components. The micro-holes are evenly arranged on the steel formwork, and use the processed steel formwork for formwork assembly; on the other side, set a storage container for high-purity compressed carbon dioxide gas, set a pipeline system to parallelly connect the outlet of the storage container with a number of gas nozzles, and the gas nozzles are respectively installed into the micro-holes so as to be able to spray gas inside the formwork.

[0007] Step 2: After the steel bars are tied up, fix them in the mold, and make the distance between the steel bars and the steel formwork not less than the required concrete cover thickness. Then pour the stirred concrete into the mold, and set the poured concrete together with the mold on the vibrating table to be vibrated and compacted by the vibrating table. During the compaction process, spray high-purity carbon dioxide gas into the interior of the concrete surface layer through the gas nozzles via the micro-holes.

[0008] Step 3: After compaction, perform standard curing or curing with formwork steam curing on the large precast component.

[0009] Step 4: After the curing is completed, remove the mold of the large precast component, spray the surface strengthening agent liquid on the surface of the large precast component, and then transfer the large precast component into an autoclave for autoclave curing, and introduce mineralization gas into the autoclave for mineralization reaction.

[0010] Step 5: Immerse the large precast component after autoclaving into saturated lime water or clear water for curing to a certain age.

[0011] Preferably, in Step 1, the diameter of the micro-holes is 0.01 - 5 mm, the distance between the micro-holes is 50 - 200 mm, a gas flow controller is provided on the pipeline system to control the flow of each gas nozzle, and the output compressed carbon dioxide pressure after being controlled is 0 - 1 MPa.

[0012] Preferably, in Step 2, the distance between the steel bars and the formwork is 10 - 100 mm, and the injection depth of the carbon dioxide gas is 2 - 90 mm.

[0013] Preferably, in Step 2, the injection depth of the carbon dioxide gas is controlled by a gas flow controller, and mineralization is carried out by means of intermittently injecting carbon dioxide gas.

[0014] Preferably, in Step 4, the tail gas containing carbon dioxide discharged from the cement plant is used as the mineralization gas; and in this step, the surface strengthening liquid is sprayed multiple times in the autoclave to enhance the mineralization degree of the surface of the precast component.

[0015] Preferably, the surface enhancer includes a surface hardener, silicone and a mineralizer. The surface enhancer is sprayed as follows: first spray the silicone once, then spray the mineralizer several times, and finally spray the surface hardener once. The spraying amount of each component is calculated by mass fraction, which is 0.5 to 15 parts of the surface hardener, 0.05 to 10 parts of the silicone, and 99.45 to 75 parts of the mineralizer.

[0016] Preferably, the organic silicon includes at least one of dimethyl silicone oil, polydimethylsiloxane and polyether-siloxane copolymer.

[0017] Preferably, the surface hardener includes at least one of magnesium fluorosilicate, aluminum fluorosilicate, and lithium silicate.

[0018] Preferably, the mineralizer includes at least one of a saturated calcium hydroxide solution, a saturated magnesium hydroxide solution, a steel slag leachate, and a magnesium chloride solution.

[0019] The present invention has the following advantages: 1. In the process of compaction, pure carbon dioxide is sprayed into the surface concrete through micropores. After the surface concrete reacts with carbon dioxide, hardening can be accelerated and strength can be improved, thereby achieving the effect of accelerating demoulding, improving demoulding quality, and shortening the production cycle. This solution can control the single injection amount of carbon dioxide by intermittent injection. The injected pure carbon dioxide is completely absorbed after reaction and will not cause a large number of pores in the concrete. Carbonization after hardening of concrete will cause the volume of solid minerals in the microstructure of concrete to shrink, thereby affecting the density and strength of the concrete, while this will not happen with carbonization of freshly mixed concrete.

[0020] 2. Carbon dioxide is sprayed into the concrete during compaction. The carbon dioxide bubbles are evenly dispersed within a certain range during the violent vibration, which is beneficial to improve the carbonization uniformity of the surface concrete and improve the efficiency of carbonization layer formation.

[0021] 3. This solution uses a gas flow controller to control the depth of carbon dioxide spraying into the concrete surface. Carbon dioxide only reacts with the freshly mixed concrete on the surface, and does not affect the alkalinity around the internal steel bars. Moreover, the surface concrete after carbonization is more compact, composed of stable, non-reactive calcium carbonate and silicon dioxide, which reduces the erosion of other ions such as sulfate ions and chloride ions, thereby improving the durability of reinforced concrete.

[0022] 4. The autoclave uses cement kiln tail gas and waste heat to reduce the energy consumption of steam curing. Repeated spraying of surface enhancement liquid further absorbs carbon dioxide and generates mineral components, thereby filling the holes and cracks on the surface, continuously enhancing the density of the specimen surface and improving the durability of the prefabricated components. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is a schematic diagram of Step 2 in the method for surface mineralization hardening and strengthening of large precast components of the present invention.

[0024] Figure 2 This is a schematic diagram of the mold in the method for surface mineralization hardening and strengthening of large precast components of the present invention.

[0025] Reference numerals in the accompanying drawings include: 1, mold; 11, steel formwork; 12, gas spray head; 2, pipeline system; 3, gas flow controller; 4, storage container. Detailed implementation manners

[0026] The following is a more detailed description of the specific implementation manners of the present invention by referring to the accompanying drawings and describing the embodiments, so as to help those skilled in the art have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0027] As Figure 1 、 Figure 2 shown, the present invention provides a method for surface mineralization hardening and strengthening of large precast components, including the following steps.

[0028] Step 1: Process a number of micropores on the steel formwork 11 for casting large precast components. The micropores are evenly arranged on the steel formwork 11, and use the processed steel formwork 11 to form a mold; on the other side, set up a storage container 4 for high-purity compressed carbon dioxide gas, and set up a pipeline system 2 to parallelly connect the outlet of the storage container 4 with a number of gas spray heads 12. The gas spray heads 12 are respectively installed into the micropores so as to spray gas into the inner side of the formwork.

[0029] In this step, the diameter of the micropores is 0.01 - 5 mm, the distance between the micropores is 50 - 200 mm. The pipeline system 2 is provided with a gas flow controller 3 to control the flow rate of each gas spray head 12, and the pressure of the compressed carbon dioxide output after being controlled is 0 - 1 MPa.

[0030] Step 2: After tying the steel bars, fix them in the mold 1, and make the distance between the steel bars and the steel formwork 11 not less than the required concrete cover thickness. Then pour the mixed cement concrete into the mold 1, and set the poured concrete together with the mold 1 on a vibrating table to be vibrated solid by the vibrating table. During the vibration process, high-purity carbon dioxide gas is sprayed into the inner layer of the concrete surface through the gas spray heads 12 via the micropores.

[0031] The dense mineralized concrete layer can prevent harmful ions in the environment from entering the interior of the concrete, and a sufficient thickness of alkaline concrete can prevent the failure of the protective effect of the steel bars. Therefore, the concrete cover thickness is equal to the sum of the mineralized layer thickness and the sufficient thickness of alkaline concrete around the steel bars. A sufficient cover thickness can ensure the good corrosion resistance of the steel bars under actual service conditions. In this embodiment, according to the requirements of large precast components, the distance between the steel bars and the formwork is 10 - 100 mm, and the injection depth of carbon dioxide gas is 2 - 90 mm. The injection depth of carbon dioxide gas is controlled by the gas flow controller 3, and the mineralization is carried out by intermittently injecting carbon dioxide gas.

[0032] Step 3: After vibration compaction, perform standard curing or curing with steam in the formwork on the large precast component.

[0033] Step 4: After the curing is completed, remove the mold 1 of the large precast component, spray the surface strengthening agent liquid on the surface of the large precast component, and then transfer the large precast component to an autoclave for autoclave curing. Mineralization gas is introduced into the autoclave for mineralization reaction.

[0034] In this embodiment, the tail gas containing carbon dioxide discharged from the cement plant is used as the mineralization gas; and in this step, the surface strengthening liquid is sprayed multiple times in the autoclave to enhance the mineralization degree of the surface of the precast component.

[0035] The surface strengthening agent includes a surface hardening agent, silicone, and a mineralizing agent. The spraying method of the surface strengthening agent is: first spray silicone once, then spray the mineralizing agent in multiple times, and finally spray the surface hardening agent once. The spraying amount of each component is calculated by mass fraction, with 0.5 - 15 parts of the surface hardening agent, 0.05 - 10 parts of silicone, and 99.45 - 75 parts of the mineralizing agent. Among them, the silicone includes at least one of dimethyl silicone oil, polydimethylsiloxane, and polyether-silicone copolymer. The surface hardening agent includes at least one of magnesium fluorosilicate, aluminum fluorosilicate, and lithium silicate. The mineralizing agent includes at least one of saturated calcium hydroxide solution, saturated magnesium hydroxide solution, steel slag leaching solution, and magnesium chloride solution.

[0036] Step 5: Immerse the large precast component after autoclave curing into saturated lime water or clear water for curing to a certain age.

[0037] The present invention has been described exemplarily above in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantive improvements are made by adopting the inventive concept and technical solution of the present invention, or the inventive concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. Method for enhancing surface mineralization hardening of large precast components, characterized in that: It includes the following steps: Step 1: Process a number of micropores on the steel formwork (11) for casting large precast components. The micropores are evenly distributed on the steel formwork (11), and use the processed steel formwork (11) to assemble the formwork; on the other side, set a storage container (4) for high-purity compressed carbon dioxide gas, and set a pipeline system (2) to parallelly connect the outlet of the storage container (4) with a number of gas nozzles (12). The gas nozzles (12) are installed in the micropores one by one so as to spray gas inside the formwork; Step 2: After tying the steel bars, fix them in the mold (1), and make the distance between the steel bars and the steel formwork (11) not less than the required concrete cover thickness. Then pour the stirred concrete into the mold (1), and set the poured concrete together with the mold (1) on a vibrating table to be vibrated and compacted by the vibrating table. During the compaction process, high-purity carbon dioxide gas is sprayed into the interior of the concrete surface layer through the micropores by the gas nozzles (12); Step 3: After compaction, carry out standard curing or curing with steam in the mold for the large precast component; Step 4: After the curing is completed, remove the mold (1) of the large precast component, spray a surface strengthening agent liquid on the surface of the large precast component, and then transfer the large precast component into an autoclave for autoclave curing, and introduce a mineralization gas into the autoclave for mineralization reaction; Step 5: Immerse the large precast component after autoclaving into saturated lime water or clear water for curing to a certain age.

2. The method for enhancing the surface mineralization and hardening of large precast components according to claim 1, wherein: In Step 1, the diameter of the micropores is 0.01 - 5 mm, the distance between the micropores is 50 - 200 mm. A gas flow controller (3) is provided on the pipeline system (2) to control the flow rate of each gas nozzle (12), and the output compressed carbon dioxide pressure after being controlled is 0 - 1 MPa.

3. The method for enhancing surface mineralization hardening of large precast components according to claim 1, characterized in that: In Step 2, the distance between the steel bars and the formwork is 10 - 100 mm, and the injection depth of the carbon dioxide gas is 2 - 90 mm.

4. The method for enhancing surface mineralization hardening of large precast components according to claim 1, characterized in that: In Step 2, the injection depth of the carbon dioxide gas is controlled by the gas flow controller (3), and the mineralization is carried out by intermittently injecting the carbon dioxide gas.

5. The method for enhancing the surface mineralization and hardening of large precast components according to claim 1, characterized in that: In Step 4, the tail gas containing carbon dioxide discharged from a cement plant is used as the mineralization gas; and in this step, the surface strengthening liquid is sprayed multiple times in the autoclave to enhance the mineralization degree of the surface of the precast component.

6. The method for surface mineralization hardening and strengthening of large precast components according to claim 1, characterized in that: The surface strengthening agent includes a surface hardening agent, silicone, and a mineralizing agent. The spraying method of the surface strengthening agent is: first spray silicone once, then spray the mineralizing agent in multiple times, and finally spray the surface hardening agent once. The spraying amount of each component is calculated by mass fraction, 0.5 - 15 parts of the surface hardening agent, 0.05 - 10 parts of silicone, and 99.45 - 75 parts of the mineralizing agent.

7. The method for enhancing surface mineralization hardening of large precast components according to claim 6, characterized in that: The silicone includes at least one of dimethyl silicone oil, polydimethylsiloxane, and polyether-siloxane copolymer.

8. The method for enhancing the surface mineralization hardening of large precast components according to claim 6, characterized in that: The surface hardening agent includes at least one of magnesium fluorosilicate, aluminum fluorosilicate, and lithium silicate.

9. The method for enhancing mineralization hardening on the surface of large precast components according to claim 6, characterized in that: The mineralizing agent includes at least one of saturated calcium hydroxide solution, saturated magnesium hydroxide solution, steel slag leaching solution, and magnesium chloride solution.

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