A method for chloride ion curing of concrete

Abstract

A method for curing chloride ions in concrete, comprising: preparing a barium salt slow-release material; mixing 0.2-1% by mass of the barium salt slow-release material with a concrete mixture; and steam curing. The method provided by the invention can effectively improve the curing ability of the concrete body for chloride ions and prolong the service life of the concrete.

Description

Technical Field

[0001] The invention relates to a chloride ion curing method, in particular to a chloride ion curing method for concrete. Background Art

[0002] With the continuous advancement of coastal and marine infrastructure construction, the extensive use of seawater, sea sand and coral aggregates has effectively alleviated regional material restrictions. However, the large amount of chloride ions contained in the marine environment and marine materials will cause corrosion to steel bars, further affecting the durability of reinforced concrete structures.

[0003] The inventors have found through long-term and extensive research that the formation of stable chloride ion hydration products such as Friedel's salt (3CaO·A12O3·CaCl2·10H2O) in concrete can improve the curing ability of the concrete body to chloride ions and reduce the harm of chloride ions to steel bars without significantly increasing the cost of concrete. Friedel's salt is the transformation of AFm phase in the presence of chloride ions. AFm phase is generally generated by AFt under the condition of lack of sulfate. In order to improve the curing ability of the concrete body to chloride ions, it is necessary to ensure the generation of AFt in the early stage and the generation of AFm phase in the later stage. Therefore, in order to improve the effect of curing chloride ions, it is very important to adjust the concentration of sulfate in the later stage to increase the content of AFm phase. Summary of the invention

[0004] In order to make up for the deficiencies of the prior art, the present invention discloses a method for chloride ion curing of steam-cured concrete based on AFt phase transformation, which is achieved by adopting the following technical solutions:

[0005] A chloride ion curing method for concrete comprises:

[0006] 1) preparing barium salt sustained-release material;

[0007] 2) mixing 0.2-1% by mass of the barium salt slow-release material with the concrete mixture;

[0008] 3) Steaming and curing.

[0009] Further, the step 1) comprises:

[0010] a) preparing a barium salt solution with a mass concentration of 5-8%;

[0011] b) adding a porous material to the obtained barium salt solution, stirring for 10 minutes and filtering;

[0012] c) spraying the porous material obtained in step b);

[0013] d) Dry at 50°C and then cool.

[0014] Furthermore, the spraying gas pressure is 0.5 MPa; the spraying flow rate is 80-90 L / h, and the spraying material includes: nano silica sol.

[0015] Furthermore, the barium salt comprises barium nitrate; and the porous material comprises expanded vermiculite. Furthermore, in the step 3), steam curing is performed at 60-70° C. for 8 hours. Compared with the closest prior art, the technical solution provided by the present invention has the following excellent effects:

[0016] 1) The technical solution provided by the present invention can effectively improve the curing ability of concrete for chloride ions. When the temperature-controlled barium salt slow-release material is added in an amount of 0.2-1% in concrete and the concrete steam curing temperature is 60-70°C, the chloride ion curing rate at 1d can reach 45%; the chloride ion curing rate at 28d can reach 62%, which effectively reduces the risk of chloride ion steel bar corrosion and prolongs the service life of concrete.

[0017] 2) The technical solution provided by the present invention encapsulates barium nitrate to prevent barium nitrate from reacting with gypsum in cement too early, thereby affecting the setting time of concrete and the generation of AFt; the late dissolution of barium salt is achieved by adjusting the temperature, and the sulfate in AFt is regulated while ensuring the generation of AFt, thereby promoting the transformation of AFt to AFm phase.

[0018] 3) The expanded vermiculite used in the present invention has a porous structure, and its water absorption and re-entry performance can form internal curing, which is beneficial to the development of the later performance of concrete; the nano-silica sol used will react with the hydration product of cement to generate secondary hydration products, thereby improving the strength of concrete and reducing porosity. DETAILED DESCRIPTION

[0019] In order to better understand the present invention, the contents of the present invention are further described below.

[0020] The present invention realizes the conversion of AFt by effectively utilizing the temperature of steam-cured concrete, improves the curing ability of concrete for chloride ions, and prolongs the service life of concrete. When the dosage of barium salt slow-release material is 0.2-1.0%, when the steam-curing temperature of concrete is 60-70°C, the chloride ion curing rate at 1d age reaches 45%; the chloride ion curing rate at 28d age reaches 62%. The present invention prevents barium nitrate from reacting with gypsum in cement too early through early encapsulation of barium nitrate, thereby affecting the setting time of concrete and the generation of AFt; through the influence of temperature, the late dissolution of barium salt is realized, and the shell rupture temperature of barium salt slow-release material is less than 60-70°C; under the condition of ensuring the generation of AFt, the sulfate in AFt is timely regulated to promote the transformation of AFt to AFm phase; the expanded vermiculite used is a porous structure, and the water absorption and return performance of the porous structure can form internal curing, which is beneficial to the development of the later performance of concrete; the nano-silica sol used will react with the hydration product of cement to generate secondary hydration products, improve the strength of concrete, and reduce porosity.

[0021] Example 1

[0022] The concrete raw material provided in this embodiment includes the following components by mass percentage:

[0023] cement water Sand Stone Sodium chloride Barium salt sustained release material 16.6 8 31 44 0.2 0.2

[0024] Preparation of barium salt sustained-release material:

[0025] 1) preparing a barium salt solution with a mass concentration of 5%;

[0026] 2) adding a porous material to the barium salt solution so that the barium salt is adsorbed into the porous material;

[0027] 3) placing the porous material adsorbing the barium salt into a fluidized bed, and using a dual-fluid nozzle to spray the nano-silica sol onto the porous material, so that the nano-silica sol forms a uniform thin film on the surface of the porous material;

[0028] 4) Blow hot air at 50°C to dry the surface and cool to room temperature for later use.

[0029] Mix 16.6% cement, 8% water, 31% sand, 44% gravel, 0.2% sodium chloride and 0.2% barium salt slow-release material evenly and form them. Steam cure them at a steam curing temperature of 60-70℃ for 8 hours.

[0030] Example 2

[0031] The concrete raw material provided in this embodiment includes the following components by mass percentage:

[0032] cement water Sand Stone Sodium chloride Barium salt sustained release material 16.4 8 31 44 0.2 0.4

[0033] Preparation of barium salt sustained-release material:

[0034] 1) preparing a barium salt solution with a mass concentration of 5%;

[0035] 2) adding a porous material to the barium salt solution so that the barium salt is adsorbed into the porous material;

[0036] 3) placing the porous material adsorbing the barium salt into a fluidized bed, and using a dual-fluid nozzle to spray the nano-silica sol onto the porous material, so that the nano-silica sol forms a uniform thin film on the surface of the porous material;

[0037] 4) Blow hot air at 50°C to dry the surface and cool to room temperature for later use.

[0038] 16.4% cement, 8% water, 31% sand, 44% gravel, 0.2% sodium chloride and 0.4% barium salt slow-release material are mixed evenly and molded, and steam-cured at a steam-curing temperature of 60-70°C for 8 hours.

[0039] Example 3

[0040] The concrete raw material provided in this embodiment includes the following components by mass percentage:

[0041] cement water Sand Stone Sodium chloride Barium salt sustained release material 16.2 8 31 44 0.2 0.6

[0042] Preparation of barium salt sustained-release material:

[0043] 1) preparing a barium salt solution with a mass concentration of 8%;

[0044] 2) adding a porous material to the barium salt solution so that the barium salt is adsorbed into the porous material;

[0045] 3) placing the porous material adsorbing the barium salt into a fluidized bed, and using a dual-fluid nozzle to spray the nano-silica sol onto the porous material, so that the nano-silica sol forms a uniform thin film on the surface of the porous material;

[0046] 4) Blow hot air at 50°C to dry the surface and cool to room temperature for later use.

[0047] Mix 16.2% cement, 8% water, 31% sand, 44% gravel, 0.2% sodium chloride and 0.6% barium salt slow-release material evenly and form it into a shape. Steam cure it at a steam curing temperature of 60-70℃ for 8 hours.

[0048] Example 4

[0049] The concrete raw material provided in this embodiment includes the following components by mass percentage:

[0050] cement water Sand Stone Sodium chloride Barium salt sustained release material 16 8 31 44 0.2 0.8

[0051] Preparation of barium salt sustained-release material:

[0052] 1) preparing a barium salt solution with a mass concentration of 6%;

[0053] 2) adding a porous material to the barium salt solution so that the barium salt is adsorbed into the porous material;

[0054] 3) placing the porous material adsorbing the barium salt into a fluidized bed, and using a dual-fluid nozzle to spray the nano-silica sol onto the porous material, so that the nano-silica sol forms a uniform thin film on the surface of the porous material;

[0055] 4) Blow hot air at 50°C to dry the surface and cool to room temperature for later use.

[0056] Mix 16% cement, 8% water, 31% sand, 44% gravel, 0.2% sodium chloride and 0.8% barium salt slow-release material evenly and form it into a shape. Steam cure it at a steam curing temperature of 60-70℃ for 8 hours.

[0057] Example 5

[0058] The concrete raw material provided in this embodiment includes the following components by mass percentage:

[0059] cement water Sand Stone Sodium chloride Barium salt sustained release material 15.8 8 31 44 0.2 1.0

[0060] Preparation of barium salt sustained-release material:

[0061] 1) preparing a barium salt solution with a mass concentration of 8%;

[0062] 2) adding a porous material to the barium salt solution so that the barium salt is adsorbed into the porous material;

[0063] 3) placing the porous material adsorbing the barium salt into a fluidized bed, and using a dual-fluid nozzle to spray the nano-silica sol onto the porous material, so that the nano-silica sol forms a uniform thin film on the surface of the porous material;

[0064] 4) Blow hot air at 50°C to dry the surface and cool to room temperature for later use.

[0065] Mix 15.8% cement, 8% water, 31% sand, 44% gravel, 0.2% sodium chloride and 1% barium salt slow-release material evenly and form it into a shape. Steam cure it at a steam curing temperature of 60-70℃ for 8 hours.

[0066] The effects of different dosages of barium salt slow-release materials on concrete in the examples are shown in the following table:

[0067]

[0068] When the barium salt slow-release material dosage is 1%, the concrete strength is the highest, the curing rate is the highest, and the total pore volume is the smallest. The concrete strength refers to the standard GB / T 50107-2010, the chloride ion curing rate refers to the standard JGJ / T 322-2013, and the detection method of water-soluble chloride ion content in hardened concrete, the 28d chloride ion curing rate can reach more than 60%.

[0069] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A method for chloride ion curing of concrete, characterized in that: The method comprises: 1) preparing barium salt sustained-release material; 2) mixing 0.2-1% by mass of the barium salt slow-release material with the concrete mixture; 3) Steaming and curing; The step 1) comprises: a) preparing a barium salt solution with a mass concentration of 5-8%; b) adding a porous material to the obtained barium salt solution, stirring for 10 minutes and filtering; c) spraying the porous material obtained in step b); d) drying at 50°C and then cooling; The spraying gas pressure is 0.5 MPa; the spraying flow rate is 80-90 L / h, and the spraying material includes: nano silica sol.

2. The method for chloride ion curing of concrete according to claim 1, characterized in that: The barium salt includes barium nitrate; and the porous material includes expanded vermiculite.

3. The chloride ion curing method for concrete according to claim 1, characterized in that: In the step 3), steam curing is performed at 60-70° C. for 8 hours.

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