Chloride ion corrosion resistant concrete, preparation method thereof and concrete chloride ion diffusion constant testing method

Abstract

The invention provides chloride ion corrosion resistant concrete, a preparation method thereof and a concrete chloride ion diffusion constant testing method, and relates to the technical field of chloride ion protection. The water-based organic resin is sprayed on the surface of the coarse sand, the coarse sand is put into a gravity-free mixing machine to be mixed, then fine sand is added into the water-based organic resin-coarse sand mixed system, mixing continues, and a mixed system with the coarse sand-water-based organic resin semi-wrapped, part of the fine sand attached to the water-based organic resin layer and the rest of the fine sand is obtained; uniformly mixing a gel material, a defoaming agent, a water reducing agent, kaolin and water, adding the mixed system, continuously mixing, pouring, curing and molding, and curing to obtain the chloride ion corrosion resistant concrete with the strength meeting the design requirement. According to the invention, the fly ash is used for replacing part of cement and doped with water-based organic resin, so that the chloride ion penetration resistance of the concrete is improved together.

Description

Technical Field

[0001] This invention relates to the field of chloride ion protection technology, and in particular to a chloride ion-resistant concrete and its preparation method, as well as a method for testing the chloride ion diffusion constant of concrete. Background Technology

[0002] Marine engineering projects, such as bridges, docks, and coastal structures, all require chloride ion protection. Chloride ions can penetrate concrete and corrode steel structures, shortening the service life of these structures and posing significant safety hazards. The extensive use of de-icing agents in northern winters can also damage concrete bridges, affecting their lifespan. Therefore, all concrete structures exposed to chloride ions must take chloride ion corrosion into account.

[0003] The diffusion coefficient is crucial for predicting chloride ion corrosion in reinforced concrete. The service life of concrete is often predicted by testing its diffusion coefficient, ensuring the safe use of various buildings. Besides using the chloride ion diffusion coefficient for prediction, the lifespan of concrete buildings can also be increased by reducing the chloride ion diffusion coefficient, such as by improving the concrete's impermeability.

[0004] Based on the time required for testing, methods for studying chloride ion diffusion coefficients are mainly divided into slow methods and fast methods. Slow methods mainly include diffusion tank methods and natural immersion methods. These methods have long testing cycles, sometimes lasting months or even years, and have poor repeatability. Fast methods are mainly electrical methods, including the RCM (Rapid Chloride Migration Test), RCPT (Rapid Chloride Permeability Test), ACMT (Accelerated Chloride Migration Test), NEL (Conductivity Method, using the Nernst-Einstein equation), and Permit (Permition migration test). These methods have short testing cycles, but the applied electric field makes the experimental environment differ significantly from the actual environment, so the calculated diffusion coefficient may have a large deviation. Testing the chloride ion diffusion coefficient without external interference can more closely reflect the actual diffusion situation and has become an important research trend. Summary of the Invention

[0005] One of the objectives of this invention is to provide a chloride ion corrosion resistant concrete with good barrier and impermeability properties, which can reduce the chloride ion diffusion coefficient and meet high strength requirements. It is mainly used in environments with chloride ions to ensure the safety of building use.

[0006] The second objective of this invention is to provide a method for preparing the chloride ion-resistant concrete.

[0007] The third objective of this invention is to provide a method for testing the chloride ion diffusion constant in concrete.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] In a first aspect, the present invention provides a chloride ion corrosion resistant concrete, comprising the following raw materials in parts by weight: 150 parts of gel material, 210-250 parts of river sand, 1-12 parts of water-based organic resin, 2-4 parts of defoamer, 1-1.5 parts of water-reducing agent, 1-4.5 parts of kaolin and 70-80 parts of water.

[0010] The gelling material includes cement and fly ash, with fly ash accounting for 15-25% of the weight of the gelling material; the river sand includes coarse sand and fine sand.

[0011] Chloride ion-resistant concrete is prepared by the following method:

[0012] Aqueous organic resin is sprayed onto the surface of coarse sand and mixed in a zero-gravity mixer. Then, fine sand is added to the mixture of aqueous organic resin and coarse sand and the mixture is continued to be mixed to obtain a mixture of coarse sand and aqueous organic resin semi-encapsulation, with some fine sand adhering to the aqueous organic resin layer and the remaining fine sand.

[0013] The gel material, defoamer, water-reducing agent, kaolin and water are mixed evenly, and then the mixture is added to the above mixture system and mixed again. The mixture is then poured, cured and shaped, and after curing, the strength reaches the design requirements, resulting in concrete resistant to chloride ion corrosion.

[0014] The following is a detailed explanation:

[0015] Gel material:

[0016] The gel material includes cement and fly ash, with fly ash accounting for 15-25% of the weight of the gel material, preferably 20%. Barrier properties and strength are controlled by adjusting the amount and degree of hydration of fly ash.

[0017] Preferably, the cement is silicate cement PO42.5;

[0018] Preferably, the fly ash is low-calcium fly ash;

[0019] An example of the content of the gel material is, for instance, 150 parts by weight.

[0020] River sand:

[0021] River sand includes coarse sand (particle size 1-3mm) that has not been crushed by a crusher and fine sand (particle size less than 0.3mm) that has been ground by a crusher through a 50-mesh sieve. The weight ratio of coarse sand to fine sand is 1:1.

[0022] Examples of river sand content include 210, 215, 220, 225, 230, 235, 240, 245, and 250 parts by weight.

[0023] Water-based organic resins:

[0024] Preferably, the waterborne organic resin is selected from one or more of waterborne polyurethane (PU), waterborne polymethyl methacrylate (PMMA), waterborne silicone resin and waterborne epoxy resin.

[0025] Examples of the content of the waterborne organic resin are 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 parts by weight. Controlling the amount of waterborne organic resin forms semi-encapsulated particles, which regulates its barrier properties.

[0026] Defoamer:

[0027] Preferably, the defoamer is an organosilicone defoamer.

[0028] Examples of defoamer content include 2.25, 2.5, 2.75, 3, 3.25, 3.45, and 3.65 parts by weight.

[0029] Water-reducing agent:

[0030] Preferably, the water-reducing agent is a naphthalene-based water-reducing agent.

[0031] Examples of water-reducing agent content include, for instance, 1, 1.2, or 1.5 parts by weight.

[0032] Kaolin:

[0033] Examples of kaolin content include 1, 1.5, 2, 2.5, 3, 3.5, 4, and 4.5 parts by weight.

[0034] Examples of water content include 70, 72, 74, 75, 76, 78, and 80 parts by weight.

[0035] Preparation of chloride ion corrosion resistant concrete:

[0036] 1. First, prepare a mixed system as described above (210-250 parts river sand, 1-12 parts water-based organic resin), with coarse sand partially coated by water-based organic resin and fine sand adhering to the water-based organic resin layer:

[0037] The water-based organic resin is sprayed onto the surface of coarse sand and then subjected to prolonged gravity-free mixing. The specific operation is as follows: the water-based organic resin is sprayed onto the surface of coarse sand using a sprayer, with the spraying volume controlled at 100-150 mL / min and the air flow rate controlled at 100-400 NL / min; then it is placed in a gravity-free mixer for uniform mixing, with a voltage of 220V, a power of 2500W, a rotation speed of 36000 r / min, and a mixing time of 3-5 minutes; finally, fine sand (particle size less than 0.3 mm) that has passed through a 50-mesh sieve is added to the organic resin-coarse sand mixture and mixing continues.

[0038] Aqueous organic resin is uniformly mixed with coarse sand (particle size 1-3mm), and then fine sand (passed through a 50-mesh sieve) is added to the coarse sand-aqueous organic resin mixture. Since the proportion of sand is much greater than that of water-based organic resin, and after a long period of uniform mixing under gravity, the water-based organic resin cannot completely coat all the sand particles, forming a mixture system in which coarse sand and water-based organic resin partially coat the sand particles, and fine sand adheres to the water-based organic resin layer.

[0039] 2. Mix the gel material, defoamer, water-reducing agent, kaolin and water evenly, then add the above-mentioned coarse sand-water-based organic resin semi-encapsulation, fine sand adhering to the water-based organic resin layer and continue mixing. Pour and cure to form a mold, and after curing for 28 days, the strength reaches the design requirements.

[0040] The water-based organic resin used has certain chemical resistance properties. Using semi-coated modified coarse sand as aggregate in concrete preparation imparts these properties. This is because the amino and ester groups in the water-based organic resin can generate ionic forces with chloride ions, adsorbing them and thus inhibiting their diffusion in the concrete. Furthermore, the semi-coated particles reduce the voids between coarse and fine sand, decreasing the formation of pores and microcracks during cement hydration, thereby reducing the permeability of water and other corrosive substances in the concrete and improving its service life. The addition of the water-based organic resin also improves the fluidity and plasticity of the concrete slurry, making it easier to construct and pour.

[0041] Secondly, the present invention provides a method for preparing chloride ion-resistant concrete, comprising the following steps:

[0042] Aqueous organic resin is sprayed onto the surface of coarse sand and mixed in a zero-gravity mixer. Then, fine sand is added to the mixture of aqueous organic resin and coarse sand and the mixture is continued to be mixed to obtain a mixture of coarse sand and aqueous organic resin semi-encapsulation, with some fine sand adhering to the aqueous organic resin layer and the remaining fine sand.

[0043] The gel material, the aforementioned mixture system, defoamer, water-reducing agent, kaolin, and water are mixed evenly, poured and cured to form a solid shape. After curing, the strength reaches the design requirements, resulting in concrete resistant to chloride ion corrosion.

[0044] The description of the second aspect is the same as that of the first aspect, and will not be repeated here.

[0045] Thirdly, the present invention also provides a method for testing the chloride ion diffusion constant in concrete, such as... Figure 1 As shown, it includes the following steps:

[0046] A groove is cut into the concrete block to be tested, conductive adhesive is applied to the back of the concrete block, and the conductive adhesive is cut with the cut corresponding to the groove.

[0047] When a resistance testing device is connected to both ends of the conductive adhesive, the entire circuit is in an open circuit state after the connection is made.

[0048] A 0.5 mol / L NaCl solution was dripped into the groove, and timing was started. The NaCl solution penetrated into the concrete block until the salt solution diffused into the micro-cracks. In the initial stage of timing, since the NaCl solution did not diffuse through the concrete to the conductive adhesive cut, the entire circuit was in an open circuit state. As time went on, the NaCl solution permeated through the concrete, connecting the circuit. The resistance decreased as the amount of NaCl solution at the conductive adhesive cut increased until the resistance reached a constant value (approximately 0.5-3.0 MΩ). Timing was then stopped, and the time t for chloride ions to diffuse through the concrete of thickness x was recorded.

[0049] According to the relation Calculate the diffusion constant of chloride ions in the concrete block to be tested, where D1 is the diffusion constant, x is the thickness from the bottom of the groove to the back of the concrete block (mm), and t is the time (s) for chloride ions to diffuse through the concrete of thickness x.

[0050] The specific method is as follows: First, use a drilling machine to drill a round hole in the concrete block to be tested, and grind a groove in the middle of the hole (drilling the hole is to reduce the number of times NaCl solution is added to the round hole and to avoid rapid evaporation of the NaCl solution due to insufficient solution). Then, apply conductive adhesive to the back of the concrete block at the position corresponding to the round hole. Use a scribe to cut the conductive adhesive at the position corresponding to the groove (Note: the narrower the cut, the better; a wider cut will increase the error). See the actual picture below. Figure 2As shown. Using alligator clips, connect the conductive adhesive to the testing instrument (e.g., a UT804 multimeter). Set the UT804 to the resistance setting. At this point, since the entire circuit is open, the UT804 will not display a reading. While the instrument begins recording the resistance change, add a 0.5 mol / L NaCl solution to the round hole in the concrete. As the testing time increases, the instrument will display a reading. Stop counting when the reading drops to 0.5-3.0 MΩ and hardly changes anymore. Record the time taken for the connection to be turned on as t, and the thickness of the concrete groove from its bottom as x. Using the formula derived above, the diffusion constant D1 of chloride ions in the composite concrete can be calculated.

[0051] Theoretical basis of the test

[0052] The diffusion of salt solution in concrete can be described by Fick's second law (see Equation 1). The solution to its error function is shown in Equation 2.

[0053]

[0054] Equation 1 can be transformed into:

[0055]

[0056] In the above formula, all quantities on the left side are known. Let this value be η, then the diffusion depth is...

[0057]

[0058] make but

[0059]

[0060] Based on equation (4), the diffusion situation can be analyzed and the lifetime can be predicted simply by obtaining the thickness of the sample and the transmission time. The complex diffusion coefficient calculation method is simplified to the calculation of the diffusion constant D1.

[0061] The method for testing the chloride ion diffusion coefficient of concrete according to this invention has a short testing time and does not require an external electric field, which greatly reduces the error in the test.

[0062] Beneficial effects

[0063] 1. This invention improves the chloride ion penetration resistance of concrete by replacing part of the cement with fly ash and adding water-based organic resin. The coarse sand, partially coated with water-based organic resin, imparts certain chemical resistance to the concrete, inhibits the diffusion of chloride ions within the concrete, and reduces the voids between the coarse and fine sand, thus reducing the formation of pores and microcracks during the cement hydration process.

[0064] 2. By innovating the impregnation method, the accuracy of predicting the chloride ion diffusion constant is greatly improved, while also significantly saving the time required for the impregnation process, facilitating on-site testing and engineering evaluation. For different applications, the service life of concrete projects can be designed by controlling the chloride ion diffusion constant.

[0065] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments. Attached Figure Description

[0066] Figure 1 A schematic diagram of a method for testing the chloride ion diffusion constant in concrete is shown.

[0067] Figure 2 The method for testing the chloride ion diffusion constant in concrete is shown in the sample preparation diagram.

[0068] Figure 3 The graph shows the relationship between the thickness of composite concrete with different fly ash content and the square root of time.

[0069] Figure 4 The graph shows the relationship between the thickness of composite concrete with different PU doping levels and the square root of time. Detailed Implementation

[0070] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0071] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0072] Raw materials and equipment:

[0073] The cement is ordinary Portland cement (PO42.5), sourced from Conch Cement Co., Ltd.

[0074] The aggregates include ordinary river sand (coarse sand with a particle size of about 1-3 mm that has not been crushed by a crusher) and fine sand (ground by a crusher and passed through a 50-mesh sieve), with a sand ratio of 1:1.

[0075] The fly ash comes from Huaneng Shang'an Power Plant in Shijiazhuang City, Hebei Province. It is low-calcium fly ash (Grade F) with a particle size of about 15μm.

[0076] The naphthalene-based water-reducing agent, model FND-C, is from Wanshan Chemical.

[0077] The silicone defoamer, model PX-122, is from Punio Industrial.

[0078] The kaolin comes from Henan Hengyuan New Materials Co., Ltd.

[0079] Waterborne polyurethane (PU) is from Foshan Chuangdawei Polyurethane Products Co., Ltd.

[0080] Evaluation method:

[0081] Compressive strength: GB / T50081 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" was adopted.

[0082] Chloride ion diffusion constant: determined according to the method described above.

[0083] Experimental Example 1: Effect of Fly Ash Replacing Part of Cement on Concrete Strength and Impermeability

[0084] Prepare concrete A to F according to the raw material formulas in Table 1 below:

[0085] Table 1. Mix proportions of composite concrete with fly ash replacing a portion of cement.

[0086]

[0087] Preparation method:

[0088] Concrete slurry with fly ash replacing part of the cement was prepared according to the above formula. The slurry was poured into a triangular mold (40mm×40mm×40mm), cured at room temperature for 1 day, demolded, and cured at room temperature for 28 days. The resulting sample was then cut into concrete blocks of different thicknesses.

[0089] Grind the bottom of the concrete block smooth. Drill a round hole on the front of the concrete block using a drilling machine. Grind a groove inside the round hole. Measure the thickness between the bottom of the groove and the bottom of the concrete (control the thickness between 0.6mm and 2.5mm). Then measure the chloride ion diffusion constant of the concrete according to the method described above. The test time is positively correlated with the thickness from the groove to the bottom of the concrete. The thicker the thickness, the longer the test time.

[0090] The compressive strength test results of composite concrete with different fly ash content are shown in Table 2 (compressive strength was tested with a 40mm×40mm×40mm sample).

[0091] Table 2

[0092]

[0093] The chloride ion diffusion constant test results of composite concrete with different fly ash doping amounts are shown in Table 3. Figure 3This is a linear fit graph showing the permeation of 0.5 mol / L NaCl solution through composite concrete of different fly ash replacement amounts and thicknesses. It illustrates the relationship between thickness and the square root of the NaCl solution permeation time. The slope of each data set can be used to determine the diffusion constant; a larger slope corresponds to a smaller diffusion constant in the composite concrete, indicating better NaCl permeation resistance. + Penetration and corrosion resistance.

[0094] Table 3

[0095]

[0096] Experimental studies have shown that when fly ash replaces 20% of the cement content, it exhibits the best resistance to chloride ion penetration and compressive strength. Furthermore, the chloride ion penetration resistance of concrete initially increases and then decreases with increasing fly ash replacement. When no fly ash is incorporated into the concrete, the cement reacts directly with water to form CSH gel. In the initial stage of the hydration reaction, many very small crystals are formed. As these crystals grow and connect, they gradually fill the voids in the cement mortar. However, due to the presence of moisture during the reaction, the crystals disperse to some extent and continuously recombine, leaving pores during gel formation. These pores connect with each other during hydration, forming microchannels in the concrete. When the fly ash replacement rate is 10%, the aluminosilicates in the fly ash react with the calcium compounds in the cement to form CASH gel. CASH gel is more stable and has a filling effect on pores, but at this point, there are still many pores in the concrete. When the fly ash replacement rate reaches 20%, a small amount of fly ash microspheres will appear in the structure. This is because while the fly ash content reacting with the cement reaches saturation, the excess fly ash retains its original microsphere morphology throughout the system, filling the pores in the structure. When the fly ash replacement rate reaches 20%, the composite concrete structure is the densest with the fewest pores. When the fly ash replacement rate is 30%, 40%, and 50%, fly ash aggregation will occur in the concrete structure. This is because the excessive fly ash content and the certain chemical properties and adsorption properties of the fly ash microspheres cause them to adsorb each other in the concrete and form aggregates. Agglomeration of fly ash microspheres increases the porosity of concrete, thereby reducing its density and mechanical strength. Furthermore, agglomerated fly ash particles can create weak points in concrete, thus reducing its overall strength.

[0097] Experimental Example 2: Effect of Different PU Admixtures on Concrete Strength and Impermeability

[0098] Concrete A1 to F1 should be prepared according to the raw material formulas in Table 4 below:

[0099] Table 4. Mix proportions of composite concrete doped with waterborne polyurethane

[0100]

[0101] Preparation method:

[0102] According to the above formula, water-based organic resin is sprayed onto the surface of coarse sand using a sprayer at a spray rate of 120 mL / min and an air flow rate of 250 NL / min. Then, it is placed in a zero-gravity mixer for uniform mixing at 220V, 2500W, and 36000 rpm for 3 minutes. Finally, fine sand (particle size less than 0.3 mm) that has passed through a 50-mesh sieve is added to the organic resin-coarse sand mixture, forming a semi-encapsulated system of coarse sand and water-based organic resin, with the fine sand adhering to the water-based organic resin layer. PO42.5 is mixed with the above mixture, and water is added for uniform stirring. During this process, kaolin, a water-reducing agent, and a defoamer are added. The resulting slurry is poured into a triangular mold (40 mm × 40 mm × 40 mm), cured at room temperature for 1 day, demolded, and cured at room temperature for 28 days. The resulting sample is then cut into concrete blocks of different thicknesses.

[0103] Grind the bottom of the concrete block smooth. Drill a round hole on the front of the concrete block using a drilling machine. Grind a groove inside the round hole. Measure the thickness between the bottom of the groove and the bottom of the concrete (control the thickness between 0.6mm and 2.5mm). Then measure the chloride ion diffusion constant of the concrete according to the method described above. The test time is positively correlated with the thickness from the groove to the bottom of the concrete. The thicker the thickness, the longer the test time.

[0104] The compressive strength test results of composite concrete with different PU doping amounts are shown in Table 5.

[0105] Table 5

[0106]

[0107] The test results of chloride ion diffusion constant of composite concrete with different PU doping amounts are shown in Table 6. The relationship between thickness and the square root of time is shown in the figure. Figure 4 As shown.

[0108] Table 6

[0109]

[0110] Studies have shown that when the doping content of water-based organic resin reaches 5%, the prepared concrete exhibits the best resistance to chloride ion penetration and compressive strength. Notably, similar to concrete using fly ash instead of cement, the resistance to chloride ion penetration of the concrete initially increases and then decreases with increasing water-based organic resin doping content, and its resistance to chloride ion penetration is superior to that of concrete using fly ash instead of cement. Firstly, water-based organic resin can penetrate into the pores of concrete through penetration, wetting, and filling. Water-based organic resin exists in a flocculent structure in concrete, mainly distributed in the pores and cracks. This distribution significantly improves the density of the concrete. Compared to fly ash, water-based organic resin has a higher gap-filling efficiency. Furthermore, water-based organic resin can also bond cracks in concrete, imparting a certain degree of flexibility to the concrete, enhancing its crack resistance, and reducing cracks caused by temperature changes and shrinkage. Furthermore, the water-based organic resin used possesses certain chemical resistance properties. Using semi-encapsulated and modified coarse sand as aggregate in concrete preparation imparts these properties. This is because the amino and ester groups present in the water-based organic resin can generate ionic forces with chloride ions, adsorbing them and thus inhibiting their diffusion within the concrete. However, with increasing PU content, it negatively impacts the overall concrete structure in two ways: First, the molecular structure of water-based PU is incompatible with the aggregates in the concrete, leading to delamination and detachment between the aggregates and the PU, resulting in reduced overall concrete strength. Second, the increased PU content also increases the fluidity of the concrete slurry, further reducing the concrete's density and compressive strength.

[0111] In summary, both methods (partial cement replacement with fly ash and water-based organic resin) can improve the chloride ion penetration resistance of concrete and enhance its compressive and flexural strength to some extent, but their mechanisms differ. Method 1 primarily utilizes the CASH gel generated by the reaction of aluminosilicates in fly ash with calcium compounds in cement to fill the pores in the concrete, thereby increasing its density. Method 2, on the other hand, uses water-based organic resin to fill the pores in the concrete. The main difference between the two is whether new substances are generated. Concrete prepared by partially replacing cement with fly ash has higher compressive strength than concrete mixed with water-based organic resin, but its chloride ion penetration resistance is lower. Furthermore, the latter also has higher flexural strength than the former.

[0112] Example 1: Preparation of composite concrete with 20% cement content and fly ash substitution

[0113] Weigh out 30g of fly ash, 120g of PO42.5, and 112.5g each of coarse and fine sand. Mix the raw materials evenly, add 75g of water and stir. During the stirring process, add 4.5g of kaolin, 2.25g of naphthalene-based water-reducing agent and 1.5g of organosilicon defoamer. Pour the prepared slurry into a 40mm×40mm×40mm triangular mold, cure at room temperature for 1 day, demold, and then cure at room temperature for 28 days.

[0114] The specimen was subjected to a compressive strength test using an automatic constant stress testing machine, and its compressive strength was measured to be 55.6 MPa.

[0115] The impermeability of composite concrete was tested using the aforementioned electrochemical method. Five samples of different thicknesses were prepared. The diffusion constant of the solution in the composite concrete was obtained by linearly fitting the square root of the time required for the solution to permeate through the samples of different thicknesses to the sample thickness, which was 1.35 × 10⁻⁶. -9 m 2 / s.

[0116] Example 2: Preparation of composite concrete with water-based organic resin modified aggregate

[0117] A water-based organic resin with a sand content of 5% (relative to coarse sand) was sprayed onto the surface of the coarse sand. The coarse sand-water-based organic resin mixture was then mixed without gravity. 112.5g of fine sand was then added to the mixture (the specific process is as described in Experiment 2 above). The aggregate mixture was then mixed evenly with 150g of PO42.5, and 75g of water was added and stirred. During this process, 4.5g of kaolin, 2.25g of naphthalene-based water-reducing agent, and 1.5g of silicone defoamer were added. The prepared slurry was poured into a 40mm×40mm×40mm triangular mold, cured at room temperature for 1 day, demolded, and then cured at room temperature for 28 days.

[0118] The compressive strength of the specimen was measured to be 47.5 MPa using an automatic constant stress testing machine.

[0119] The impermeability of composite concrete was tested using the aforementioned electrochemical method. Five samples of different thicknesses were prepared. The diffusion constant of the solution in the composite concrete was obtained by linearly fitting the square root of the time required for the solution to permeate through the samples of different thicknesses to the sample thickness, which was 2.55 × 10⁻⁶. -10 m 2 / s.

[0120] Example 3: Preparation of composite concrete using water-based organic resin modified coarse sand as aggregate and fly ash replacement of 20%.

[0121] A water-based organic resin with a sand content of 5% (relative to coarse sand) was sprayed onto the surface of the coarse sand. The coarse sand-water-based organic resin mixture was then mixed under zero gravity. 112.5g of fine sand was then added to the mixture (the specific process is as described in Experiment 2 above). The mixed aggregate was then mixed evenly with 120g of PO42.5 and 30g of fly ash. 75g of water was added and stirred. During the stirring process, 4.5g of kaolin, 2.25g of naphthalene-based water-reducing agent, and 1.5g of organosilicon defoamer were added. The prepared slurry was poured into a 40mm×40mm×40mm triangular mold, cured at room temperature for 1 day, demolded, and then cured at room temperature for 28 days.

[0122] The compressive strength of the specimen was measured to be 50.7 MPa using an automatic constant stress testing machine.

[0123] The impermeability of composite concrete was tested using the aforementioned electrochemical method. Five samples of different thicknesses were prepared. The diffusion constant of the solution in the composite concrete was obtained by linearly fitting the square root of the time required for the solution to permeate through the samples of different thicknesses to the sample thickness, which was 1.53 × 10⁻⁶. -11 m 2 / s.

[0124] It is evident that the concrete obtained by using water-based organic resin semi-encapsulated modified coarse sand as aggregate, along with fly ash, exhibits excellent compressive strength and impermeability. In contrast, direct mixing modification and full encapsulation modification cannot achieve good results. This is because direct mixing of water-based resin will adhere to the cement, hindering the cement reaction and resulting in samples lacking strength. Furthermore, the amount of water-based resin used for full encapsulation is very large, and excessive water-based resin during the mixing process will also inhibit the cement reaction.

[0125] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. A type of concrete resistant to chloride ion corrosion, characterized in that, The raw materials include the following parts by weight: 150 parts gel material, 210-250 parts river sand, 1-12 parts water-based organic resin, 2-4 parts defoamer, 1-1.5 parts water-reducing agent, 1-4.5 parts kaolin, and 70-80 parts water. The gelling material includes cement and fly ash, with fly ash accounting for 15-25% of the weight of the gelling material; the river sand includes coarse sand and fine sand. Chloride ion-resistant concrete is prepared by the following method: Aqueous organic resin is sprayed onto the surface of coarse sand and mixed in a zero-gravity mixer. Then, fine sand is added to the mixture of aqueous organic resin and coarse sand and the mixture is continued to be mixed to obtain a mixture of coarse sand and aqueous organic resin semi-encapsulation, with some fine sand adhering to the aqueous organic resin layer and the remaining fine sand. The gel material, defoamer, water-reducing agent, kaolin and water are mixed evenly, and then the mixture is added to the mixture and mixed again. The mixture is then poured, cured and shaped, and after curing, the strength reaches the design requirements, resulting in concrete resistant to chloride ion corrosion.

2. The chloride-resistant concrete according to claim 1, characterized in that, The cement is silicate cement PO42.5; The fly ash is low-calcium fly ash.

3. The chloride-resistant concrete according to claim 1, characterized in that, The weight ratio of coarse sand to fine sand is 1:

1.

4. The chloride-resistant concrete according to claim 1, characterized in that, The waterborne organic resin is selected from one or more of waterborne polyurethane, waterborne polymethyl methacrylate, waterborne silicone resin and waterborne epoxy resin.

5. The chloride-resistant concrete according to claim 1, characterized in that, The defoamer is an organosilicone defoamer; The water-reducing agent is a naphthalene-based water-reducing agent.

6. The chloride-resistant concrete according to claim 1, characterized in that, Chloride ion-resistant concrete is prepared by the following method: Water-based organic resin is sprayed onto the surface of coarse sand using a sprayer, with the spraying rate controlled at 100-150 mL / min and the air flow rate controlled at 100-400 NL / min. Then, it is placed in a zero-gravity mixer for uniform mixing at 220V, 2500W, and 36000r / min for 3-5 minutes. Finally, fine sand that has passed through a 50-mesh sieve is added to the organic resin-coarse sand mixture and mixing continues. The gel material, defoamer, water-reducing agent, kaolin and water are mixed evenly, and then the mixture is added to the mixture and mixed again. The mixture is poured and cured, and after 28 days of curing, the strength reaches the design requirements, resulting in concrete resistant to chloride ion corrosion.

7. A method for preparing chloride-resistant concrete according to any one of claims 1-6, characterized in that, Includes the following steps: Aqueous organic resin is sprayed onto the surface of coarse sand and mixed in a zero-gravity mixer. Then, fine sand is added to the mixture of aqueous organic resin and coarse sand and the mixture is continued to be mixed to obtain a mixture of coarse sand and aqueous organic resin semi-encapsulation, with some fine sand adhering to the aqueous organic resin layer and the remaining fine sand. The gel material, the aforementioned mixture system, defoamer, water-reducing agent, kaolin, and water are mixed evenly, poured and cured to form a solid shape. After curing, the strength reaches the design requirements, resulting in concrete resistant to chloride ion corrosion.

8. The preparation method according to claim 7, characterized in that, Includes the following steps: Water-based organic resin is sprayed onto the surface of coarse sand using a sprayer, with the spraying rate controlled at 100-150 mL / min and the air flow rate controlled at 100-400 NL / min. Then, it is placed in a zero-gravity mixer for uniform mixing at 220V, 2500W, and 36000r / min for 3-5 minutes. Finally, fine sand that has passed through a 50-mesh sieve is added to the organic resin-coarse sand mixture and mixing continues. The gel material, defoamer, water-reducing agent, kaolin and water are mixed evenly, and then the mixture is added to the mixture and mixed again. The mixture is poured and cured, and after 28 days of curing, the strength reaches the design requirements, resulting in concrete resistant to chloride ion corrosion.

9. A method for testing the chloride ion diffusion constant in concrete, characterized in that, Includes the following steps: A groove is cut into the concrete block to be tested, conductive adhesive is applied to the back of the concrete block, and the conductive adhesive is cut with the cut corresponding to the groove. When a resistance testing device is connected to both ends of the conductive adhesive, the entire circuit is in an open circuit state after the connection is made. A 0.5 mol / L NaCl solution was dripped into the groove, and the timing was started. The NaCl solution penetrated into the concrete block until the salt solution diffused into the micro-cracks. At the beginning of the timing, since the NaCl solution did not diffuse through the concrete to the conductive adhesive cut, the entire circuit was in an open circuit state. As time went on, the NaCl solution penetrated through the concrete, connecting the circuit. The resistance decreased as the amount of NaCl solution at the conductive adhesive cut increased until the resistance reached a constant value. The timing was then stopped, and the time t for chloride ions to diffuse through the concrete of thickness x was recorded. According to the relation Calculate the diffusion constant of chloride ions in the concrete block to be tested, where D1 is the diffusion constant, x is the thickness from the bottom of the groove to the back of the concrete block (mm), and t is the time (s) for chloride ions to diffuse through the concrete of thickness x.

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