A preparation method and application method of a high-efficiency chloride ion curing agent for sea sand mortar

Abstract

A preparation method and application method of a high-efficiency chloride curing agent for sea sand mortar, the technical points of which are as follows: the chloride curing agent is a CaFeAl-LDO / nano-silica sol composite material; obtained by co-precipitation of a metal cation solution, an alkaline solution and a modified nano-silica sol solution. In the chloride curing agent provided by the present invention, CaFeAl-LDO can effectively solidify the chloride ions in the sea sand based on its own "structural memory function", and at the same time, through the composite between the modified nano-silica sol and the calcined CaFeAl-LDO, the layer-by-layer superposition phenomenon of CaFeAl-LDHs is avoided, and the chloride ion curing amount of the CaFeAl-LDO / nano-silica sol composite material can be significantly improved in the cement matrix, and the mechanical properties of the mortar can be significantly enhanced.

Description

Technical Field

[0001] The invention relates to the field of civil engineering, and in particular to a preparation method and an application method of a high-efficiency chloride ion curing agent for sea sand mortar. Background Art

[0002] Due to the rampant exploitation of river sand, the ecological environment has also been greatly damaged. In the face of the growing demand for engineering construction and building materials, there is an urgent need to find alternative resources to replace river sand. In recent years, mountain sand, machine-made sand and mixed sand have begun to be used to replace river sand, but these sands are quite different from river sand in shape, gradation and fine powder, and the effect of using them alone is poor.

[0003] Compared with river sand, sea sand has the advantages of low mud content, uniform gradation, abundant reserves, good sorting and suitability for large-scale industrial mining. The sea sand reserves reach 1.65 trillion tons. However, the high chloride ion content in sea sand will accelerate the corrosion of steel bars in concrete, thereby weakening the adhesion between steel bars and the matrix, affecting the long-term service of concrete. Therefore, it is particularly important to adopt new methods to solidify chloride ions in cement-based materials.

[0004] At present, the natural stacking method, mechanical method and freshwater flushing method are mainly used to desalinate chloride ions in sea sand. Among them, the natural stacking method is to pile up sea sand to a certain thickness, which generally takes several months or years, but this method requires a large site and the salt precipitation effect is not obvious, and it cannot meet emergency needs. The principle of the freshwater flushing method and the mechanical method is to treat the chloride ions in sea sand with freshwater through a variety of water treatment processes to reduce the chloride ion content, but the cost is high and wastes freshwater resources.

[0005] Patent CN201911182963.7 discloses "a chloride ion curing agent for sea sand, its preparation method and application", whose components are a mixture of CaFe-LDHs and CaFeAl-LDHs strong alkaline anion exchange resins and polyvinyl pyrrolidone. Although the curing agent has a good chloride ion curing effect, the chloride ion curing agent has a complex component and is an inorganic-organic composite. Although it has a good chloride ion curing effect in mortar, the two LDHs (layered double metal hydroxides) have a layer-by-layer superposition phenomenon, resulting in its chlorine-fixing effect far from the theoretical calculated value, and the addition of organic components has a limited improvement in the mechanical properties of the mortar. Summary of the invention

[0006] The purpose of the present invention is to provide a high-efficiency chloride ion curing agent that can be used for sea sand mortar and an application method thereof. The composite chloride ion curing agent can significantly increase the chloride ion curing amount in the cement matrix and can significantly enhance the mechanical properties of the mortar.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions:

[0008] The present invention provides a method for preparing a high-efficiency chloride ion curing agent for sea sand mortar, wherein the chloride ion curing agent is a CaFeAl-LDO / nano silica sol composite material; the chloride ion curing agent is obtained by coprecipitation of a metal cation solution, an alkaline solution and a modified nano silica sol solution. The previously synthesized CaFeAl-LDHs still has layers superimposed on each other, which limits its ability to cure chloride ions. - The curing ability and dispersibility are poor, far from the theoretical limit curing value and the strength improvement is limited. The CaFeAl-LDO used in the present invention can effectively cure chloride ions based on its own high temperature resistance and "structural memory function". At the same time, through the composite between the modified nano-silica sol and the calcined CaFeAl-LDO, the layer-by-layer superposition phenomenon of CaFeAl-LDHs is avoided, thereby further improving the chloride ion curing effect.

[0009] Nano-SiO in modified nano-silica sol 2 The nanoparticles are a kind of colloidal solution that spreads stably and evenly in water. They are transparent liquids. The large amount of active silanol and other organic functional groups (-Si-OH or -Si-R) on their surface can react with calcium hydroxide in alkaline solution to form negative ion groups. The electrostatic repulsion between the negative ion groups ensures the stability of the nano-SiO 2 The particles exist stably in solutions and cement-based materials, and can significantly improve the chloride ion curing capacity, strength and density of cement-based materials.

[0010] Furthermore, the preparation method of the modified nano-silica sol is as follows:

[0011] Weigh 10mL of silica sol and 1mL of Z6040 silane coupling agent, dissolve them in a beaker containing 9mL of deionized water, stir them evenly with a magnetic stirrer, and place them in a condensation reflux device at a temperature of 60°C for 120h. Then place them in a vacuum freeze drying box to evaporate the water to 50%, and make them into a colloidal solution, i.e., modified nano-silica sol, with a solid solution content of about 30%.

[0012] In addition, SiO in silica sol 2 It reacts with calcium hydroxide in concrete to form CSH gel, which improves the physical adsorption capacity of chloride ions. At the same time, the highly dispersed nano-silica sol is attached to LDHs during synthesis, which can make up for the original LDHs layer superposition and limit its Cl - The synergistic coupling effect of the composite system can further improve its chloride ion curing amount, matrix strength and density.

[0013] Furthermore, the preparation method of the chloride ion curing agent provided by the present invention specifically includes the following operation steps: dissolving soluble calcium source, soluble iron source and soluble aluminum source in water to prepare solution A; dissolving inorganic base in water to prepare solution B; weighing a certain amount of modified nano-silica sol, marked as solution C; dropping solution A, solution B and solution C into a container simultaneously and stirring continuously; after all dropping is completed, stirring evenly to facilitate grain nucleation; after stirring evenly, heating to facilitate grain growth to form flaky LDHs with a thin layer structure; after the reaction is completed, filtering, drying and calcining to obtain CaFeAl-LDO / nano-silica sol composite material.

[0014] Furthermore, the specific preparation method of the chloride ion curing agent provided by the present invention is as follows:

[0015] S1. Dissolve soluble calcium source, soluble aluminum source and soluble iron source in water to prepare solution A;

[0016] S2. Dissolve inorganic base in water containing water to prepare solution B;

[0017] S3. Weigh modified nano-silica sol and mark it as solution C;

[0018] S4. Drop solution A, solution B and solution C into a four-necked flask, and drop and stir evenly under magnetic stirring;

[0019] S5. Then heat and react, cool and take out, and centrifuge and wash for multiple times until weakly alkaline, and then freeze-dry in a vacuum freeze dryer;

[0020] S5. Grind the obtained product into powder to prepare CaFeAl-NO 3 LDHs and modified nano-silica sol composite system;

[0021] S6. Then use CaFeAl-NO 3 LDHs and modified nano-silica sol composite system as a precursor, and calcine it to obtain CaFeAl-LDO / nano-silica sol.

[0022] In the present invention, co-calcining the CaFeAl-NO 3 LDHs and modified nano-silica sol composite system can increase their specific surface areas, and each component has high dispersibility and chloride ion curing effect during restoration, which can increase the chloride ion curing amount and mechanical properties in the matrix.

[0023] Furthermore, the molar ratio of soluble calcium source, soluble iron source, soluble aluminum source, inorganic base and nano-silica sol is: (18-26):(2-4):(5-10):(38-54):(2-12).

[0024] Furthermore, the anions of the soluble calcium source, the soluble iron source and the soluble aluminum source are any one of nitrate, nitrite, bromide or formate ions.

[0025] Furthermore, the dripping speeds of solution A, solution B and solution C are (10-30) drops / min: (10-30) drops / min: (4-12) drops / min, and the last three solutions are titrated at the same time. Ensuring that the three solutions are titrated at the same time can make the synthesized CaFeAl-NO 3 The composite system of LDHs and modified nano-silica sol has a better crystal form, and the nano-silica sol can be well attached to LDHs.

[0026] Furthermore, the inorganic base is any one of sodium hydroxide, potassium hydroxide or lithium hydroxide.

[0027] Furthermore, the stirring time is 2 to 6 hours.

[0028] Furthermore, the heating temperature is 100-110° C., and the reaction time is 24-48 hours.

[0029] Furthermore, the calcination temperature is 600-750° C., and the calcination time is 2-6 hours.

[0030] The second object of the present invention is to provide a method for using the CaFeAl-LDO / nano-silica sol composite material as a chloride ion curing agent, which has the same technical effect.

[0031] The above technical objectives of the present invention are achieved by the following technical solutions:

[0032] The application method of the chloride ion curing agent provided by the invention is to mix the CaFeAl-LDO / nano silica sol composite material into cement, and the mixing amount is 1-5% of the cement mass.

[0033] In the present invention, the chloride ion curing agent dosage of the sea sand mortar can reach 1-5% of the cement mass, and it has a good curing effect on chloride ions in the sea sand mortar, and the restored 2D micro-nano thin sheets CaFeAl LDHs can also compact the matrix of cement-based materials; at the same time, SiO in the modified nano-silica sol is used to 2 It can undergo secondary hydration reaction with calcium hydroxide in cement-based materials to form CSH gel, thereby improving the density and strength of cement concrete and thus improving the ability to inhibit chloride ion transmission and diffusion.

[0034] Furthermore, based on the good dispersibility characteristics reflected by the large number of active silanols and other organic functional groups on the surface of the modified nano-silica sol, it can not only improve the dispersibility of cement-based materials and the chloride ion composite system and enhance the density, but also attach the highly dispersible nano-silica sol to LDHs, making up for the original LDHs layer superposition and limiting its chloride ion curing behavior, which can maximize the limit chloride ion curing amount of LDHs.

[0035] In addition, modified nano-silica sol can regulate the number of LDHs layers and mitigate CO in the environment. 2 Therefore, CaFeAl-LDO and modified nano-silica sol have a synergistic mechanism, which can solidify, block, inhibit or delay Cl from the concrete body. - It can resist the corrosion of steel bars and solve the problem that traditional cement concrete cannot fully balance the rust resistance, strength and density of solid chlorine.

[0036] In summary, the present invention has the following beneficial effects:

[0037] 1. The chloride ion curing agent provided by the present invention can be added in large quantities to sea sand mortar, and its addition amount can reach 5% of the mass of cement. The free chloride ion content in the 28d sea sand mortar sample is reduced to 0.008%, which is 86% lower than that of the blank sample, showing a good chloride ion curing effect. The preparation and use methods are simple, and it is easy to promote and use.

[0038] 2. The CaFeAl-LDO in the composite chloride ion curing agent provided by the present invention can solidify a large amount of chloride ions after restoration, and the SiO in the modified nano-silica sol 2 It can undergo secondary hydration reaction with calcium hydroxide in cement-based materials to form CSH gel, further increasing the amount of chloride ion curing.

[0039] 3. Based on the good dispersibility characteristics of the modified nano-silica sol, which contains a large number of active silanols and other organic functional groups on the surface, the present invention can attach highly dispersible nano-silica sol to LDHs, make up for the original LDHs layer-by-layer superposition, and limit its chloride ion curing behavior, which can maximize the limit of chloride ion curing of LDHs; in addition, nano-silica sol can slow down the CO in the environment. 2 Therefore, CaFeAl-LDO and nano-silica sol have a synergistic mechanism, which can solidify, block, inhibit or delay Cl - Corrosion of steel bars.

[0040] 4. After restoration, the CaFeAl-LDO in the composite chloride ion curing agent provided by the present invention can block the transmission channel of chloride ions, increase the curvature of the capillary pores, and thus improve the strength; in addition, based on the high dispersibility characteristics of nano-silica sol, it is easy to evenly disperse CaFeAl-LDO and cement particles in the slurry, thereby improving its mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic diagram of the structure of unmodified LDHs;

[0042] Figure 2 It is a schematic diagram of the structure of the CaFeAl-LDO / nano-silica sol obtained in this specific implementation manner.

[0043] Reference numerals

[0044] 1. Interlayer anions; 2. Silica sol. DETAILED DESCRIPTION

[0045] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, a preparation method and application method of a high-efficiency chloride ion curing agent for sea sand mortar proposed by the present invention, its specific implementation method, characteristics and effects are described in detail as follows.

[0046] The sources of materials used in this specific implementation are as follows:

[0047] Nano-silica sol: Hebei Jiashi Hongwei Technology Co., Ltd.;

[0048] Cement: Shandong Qiyin Cement Co., Ltd., 42.5 high sulfate-resistant silicate cement, with a specific surface area of ​​>350m 2 / kg.

[0049] This specific embodiment provides a method for preparing a high-efficiency chloride ion curing agent for sea sand mortar, wherein the chloride ion curing agent is a CaFeAl-LDO / nano-silica sol composite material, and the mass ratio of CaFeAl-LDO to nano-silica sol is (45-65): (2-12);

[0050] It is obtained by co-precipitation of metal cation solution, alkaline solution and modified nano-silica sol solution.

[0051] LDHs is a nanosheet material with a layered structure. The hydrogen bonds between the layer cations and the interlayer anions are relatively weak. It can exchange ions with other anions through strong electrostatic interactions and follow the ion exchange order. Therefore, specific LDHs with weak electrostatic interactions between layers can effectively solidify chloride ions.

[0052] In addition, LDHs also have a "structural memory function", so that the skeleton structure retained after calcination can still effectively solidify chloride ions when placed in an anion solution, and the solidification amount is much higher than that of uncalcined LDHs. However, the LDHs synthesized in the past have layer-by-layer superposition phenomenon, such as Figure 1 As shown, the interlayer anion 1 can only partially exchange ions with other anions with strong polarity, the exchange rate is low, and it is easy to agglomerate after calcination.

[0053] In this specific embodiment, after being compounded with the modified nano-silica sol, part of the silicon dioxide in the silica sol 2 can be attached between the layered LDHs nanosheets, and the specific surface area of ​​the LDHs can be increased. Figure 2 As shown, it is conducive to ion exchange with other ions and has a strong ability to adsorb anions on the surface, which can achieve the theoretical calculated value.

[0054] In this specific embodiment, the preparation method of the modified nano-silica sol is as follows:

[0055] Weigh 10 mL of silica sol and 1 mL of Z6040 silane coupling agent, dissolve them in a beaker containing 9 mL of deionized water, stir them evenly with a magnetic stirrer, and place them in a condensation reflux device at a temperature of 60°C for 120 hours of condensation reflux. Then place them in a vacuum freeze drying box to evaporate to 50% of the water and make them into a colloidal solution, which is the modified nano-silica sol.

[0056] The preparation method provided in this specific embodiment specifically includes the following steps:

[0057] Dissolve a soluble calcium source, a soluble iron source and a soluble aluminum source in water to prepare a solution A; dissolve an inorganic base in water to prepare a solution B;

[0058] Weigh a certain amount of modified nano-silica sol, marked as solution C; add solution A, solution B and solution C into the container dropwise at the same time and stir continuously; after all the additions are completed, stir evenly;

[0059] After being stirred evenly, heating is performed to facilitate the growth of grains and form lamellar LDHs with a thin layer structure;

[0060] After the reaction is completed, the mixture is filtered, dried and calcined to obtain a CaFeAl-LDO / nano-silica sol composite material.

[0061] Among them, the dropping speed of solution A, solution B and solution C is (10-30) drops / min: (10-30) drops / min: (4-12) drops / min; the stirring time is 2-6 hours; the heating temperature is 100-110°C, and the reaction time is 24-48 hours; the calcination temperature is 600-750°C, and the calcination time is 2-6 hours.

[0062] When the LDHs-silica sol composite system is calcined at 600-750°C, since CaFeAl-LDHs has higher high temperature resistance, the CaFeAl-LDO calcined at this temperature can still maintain its own skeleton structure, and can solidify a large amount of chloride ions based on its own "structural memory function"; and the nano-silica sol will not decompose at this temperature and has high dispersibility in cement-based materials, so the calcined CaFeAl-LDO / nano-silica sol composite material has high chloride ion curing effect and mechanical properties.

[0063] Among them, the molar ratio of soluble calcium source, soluble iron source, soluble aluminum source, inorganic base and modified nano-silica sol is: (18-26): (2-4): (5-10): (38-54): (2-12); the anions of the soluble calcium source, soluble iron source and soluble aluminum source are any one of nitrate, nitrite, bromide or formate ions; the inorganic base is any one of sodium hydroxide, potassium hydroxide or lithium hydroxide.

[0064] This specific embodiment provides an application method of a high-efficiency chloride ion curing agent for sea sand mortar, specifically, the CaFeAl-LDO / nano silica sol composite material is mixed into cement, and the mixing amount is 1-5% of the mass of the cement.

[0065] Example 1: A method for preparing a high-efficiency chloride ion curing agent for sea sand mortar

[0066] The preparation method of the composite material of CaFeAl-LDO and nano-silica sol comprises the following steps:

[0067] S1. Dissolve 100 mmol of calcium nitrate tetrahydrate, 40 mmol of aluminum nitrate nonahydrate, and 10 mmol of ferric nitrate nonahydrate in a beaker containing 100 mL of deionized water to prepare solution A.

[0068] S2. Dissolve 260 mmol of sodium hydroxide in a beaker containing 100 mL of deionized water to prepare solution B;

[0069] S3, weigh 8 mL of modified nano-silica sol and mark it as solution C;

[0070] S4, add solution A, solution B and solution C dropwise into a four-necked flask (the dropping speed of solution A and solution B is 20 drops / min, and the dropping speed of solution C is 10 drops / min), stir for 6 hours after the dropping is completed, and then place in an autoclave at 110°C for reaction for 24 hours, take out after cooling, centrifuge and wash several times until it is weakly alkaline, and then freeze-dry in a vacuum freeze dryer for 48 hours;

[0071] S5. Grind the obtained product into powder to prepare CaFeAl-NO 3LDHs and modified nano-silica sol composite system;

[0072] S6, and then CaFeAl-NO 3 The LDHs and modified nano-silica sol composite system were used as precursors, which were calcined at 700°C in a muffle furnace for 4 hours to obtain a CaFeAl-LDO / nano-silica sol composite material.

[0073] The preparation method of the modified nano-silica sol is as follows:

[0074] Weigh 10 mL of silica sol and 1 mL of Z6040 silane coupling agent, dissolve them in a beaker containing 9 mL of deionized water, stir them evenly with a magnetic stirrer, and place them in a condensation reflux device at a temperature of 60°C for 120 hours of condensation reflux. Then place them in a vacuum freeze drying box to evaporate to 50% of the water and make them into a colloidal solution, which is the modified nano-silica sol.

[0075] Example 2: A method for preparing a high-efficiency chloride ion curing agent for sea sand mortar

[0076] The preparation method of the CaFeAl-LDO / nano silica sol composite material comprises the following steps:

[0077] S1. Dissolve 130 mmol of calcium nitrate tetrahydrate, 50 mmol of aluminum nitrate nonahydrate, and 15 mmol of ferric nitrate nonahydrate in a beaker containing 100 mL of deionized water to prepare solution A.

[0078] S2. Dissolve 270 mmol of sodium hydroxide in a beaker containing 100 mL of deionized water to prepare solution B;

[0079] S3, weigh 2 mL of modified nano-silica sol and mark it as solution C;

[0080] S4, add A, B and C solutions dropwise into a four-necked flask (the dropping speed of A solution and B solution is 30 drops / min, and the dropping speed of C solution is 9 drops / min), stir for 2 hours after the dropwise addition is completed, place in an autoclave at 105°C for reaction for 36 hours, take out after cooling, centrifuge and wash several times until it is weakly alkaline, and then freeze-dry in a vacuum freeze dryer for 36 hours;

[0081] S5. Grind the obtained product into powder to prepare CaFeAl-NO 3 LDHs and modified nano-silica sol composite system;

[0082] S6, and then CaFeAl-NO 3 The LDHs and modified nano-silica sol composite system were used as precursors, which were calcined at 650°C in a muffle furnace for 6 hours to obtain a CaFeAl-LDO / nano-silica sol composite material.

[0083] Wherein, the preparation method of the modified nano-silica sol is the same as that in Example 1.

[0084] Example 3: Preparation method of a high-efficiency chloride ion curing agent for sea sand mortar

[0085] The preparation method of the CaFeAl-LDO / nano silica sol composite material comprises the following steps:

[0086] S1. Dissolve 120 mmol of calcium nitrate tetrahydrate, 45 mmol of aluminum nitrate nonahydrate, and 15 mmol of ferric nitrate nonahydrate in a beaker containing 100 mL of deionized water to prepare solution A.

[0087] S2. Dissolve 245 mmol of sodium hydroxide in a beaker containing 100 mL of deionized water to prepare solution B;

[0088] S3, weigh 12 mL of modified nano-silica sol and mark it as solution C;

[0089] S4, add A, B and C solutions dropwise into a four-necked flask (the dropping speed of A and B solutions is 10 drops / min, and the dropping speed of C solution is 4 drops / min), stir for 4 hours after the addition is complete, place in an autoclave at 100°C for reaction for 48 hours, take out after cooling, centrifuge and wash several times until it is weakly alkaline, and then freeze-dry in a vacuum freeze dryer for 72 hours;

[0090] S5. Grind the obtained product into powder to prepare CaFeAl-NO 3 LDHs and modified nano-silica sol composite system;

[0091] S6, and then CaFeAl-NO 3 The LDHs and modified nano-silica sol composite system were used as precursors, which were calcined at 600°C in a muffle furnace for 2 hours to obtain a CaFeAl-LDO / nano-silica sol composite material.

[0092] Wherein, the preparation method of the modified nano-silica sol is the same as that in Example 1.

[0093] Example 4: Preparation method of a high-efficiency chloride ion curing agent for sea sand mortar

[0094] The preparation method of the CaFeAl-LDO / nano silica sol composite material comprises the following steps:

[0095] S1. Dissolve 90 mmol of calcium nitrate tetrahydrate, 25 mmol of aluminum nitrate nonahydrate, and 20 mmol of ferric nitrate nonahydrate in a beaker containing 100 mL of deionized water to prepare solution A;

[0096] S2. Dissolve 190 mmol of sodium hydroxide in a beaker containing 100 mL of deionized water to prepare solution B;

[0097] S3, weigh 6 mL of modified nano-silica sol and mark it as solution C;

[0098] S4, add A, B and C solutions dropwise into a four-necked flask (the dropping speed of A and B solutions is 20 drops / min, and the dropping speed of C solution is 12 drops / min), stir for 3 hours after the addition is completed, place in an autoclave at 110°C for reaction for 36 hours, take out after cooling, centrifuge and wash several times until it is weakly alkaline, and then freeze-dry in a vacuum freeze dryer for 72 hours;

[0099] S5. Grind the obtained product into powder to prepare CaFeAl-NO 3 LDHs and nano-silica sol composite system; then CaFeAl-NO 3 The composite system of LDHs and modified nano-silica sol is the precursor;

[0100] S6. The mixture was calcined in a muffle furnace at 750° C. for 2 h to obtain a CaFeAl-LDO / nano-silica sol composite material.

[0101] Wherein, the preparation method of the modified nano-silica sol is the same as that in Example 1.

[0102] Performance Testing

[0103] In this specific implementation, according to the standard SL 352-2006 "Testing Procedures for Hydraulic Concrete", the free chloride ion content in the mortar test block is determined by potentiometric titration, wherein the concentration of the silver nitrate solution is 0.01 mol / L. The model is ZDCL-2 automatic chloride ion potentiometric titrator, from Shanghai Yidian Scientific Instrument Co., Ltd. The cement mortar sample is prepared according to the preparation method specified in GB / T 17671-1999 "Test Method for Strength of Cement Mortar".

[0104] 1. Prepare cement with a chloride ion curing agent content of 1.0%: mix high sulfate-resistant silicate cement, sea sand and water in a mass ratio of 1:3:0.5, and add the CaFeAl-LDO / nano-silica sol composite material prepared in Examples 1 to 4 in an amount of 1.0% of the cement mass; and use the same mass of CaFeAl-LDO and modified nano-silica sol to replace the CaFeAl-LDO / nano-silica sol composite material respectively; the sea sand is taken from untreated dredged sea sand around the Yellow Sea, and the chloride ion content in the sea sand is 0.3wt.%.

[0105] 2. Prepare cement with a chloride ion curing agent content of 5.0%: mix high sulfate-resistant silicate cement, sea sand and water in a mass ratio of 1:3:0.5, and add the CaFeAl-LDO / nano-silica sol composite material prepared in Examples 1 to 4 in an amount of 5.0% of the cement mass; and use equal masses of CaFeAl-LDO and modified nano-silica sol to replace the CaFeAl-LDO / nano-silica sol composite material respectively; the sea sand is taken from untreated dredged sea sand around the Yellow Sea, and the chloride ion content in the sea sand is 0.3wt.%.

[0106] 3. After mixing the above mortar evenly, pour it into a 40×40×160mm molding mold and demould it after 24 hours. After reaching the age of 28 days, the water-soluble chloride ion content and compressive strength of the mortar sample are measured by a measuring instrument. The test results are shown in Tables 1 and 2.

[0107] Table 1 Chloride ion content in mortar (%)

[0108] Experimental group (-XX% indicates the amount of curing agent added) Chloride ion content in 28d mortar / % Example 1 - 1.0% 0.025 Example 1 - 5.0% 0.008 Example 2 - 1.0% 0.030 Example 2 - 5.0% 0.015 Example 3 - 1.0% 0.031 Example 3 - 5.0% 0.017 Example 4 - 1.0% 0.028 Example 4 - 5.0% 0.012 CaFeAl-LDO-1.0% 0.033 CaFeAl-LDO-5.0% 0.018 Modified Nano-Silica Sol-1.0% 0.041 Modified Nano-Silica Sol-5.0% 0.023 Blank group (no chloride ion curing agent added) 0.056

[0109] It can be concluded from Table 1 that for the 28d sea sand mortar sample, as the amount of curing agent continues to increase, the water-soluble chloride ion content in the mortar tends to gradually decrease, especially the chloride ion curing agent provided in Example 1. When the amount of chloride ion curing agent is 5.0%, the water-soluble chloride ion content of the 28d sample decreases to 0.008%, which is 86% lower than that of the blank sample, showing a good chloride ion curing effect.

[0110] At the same time, the chloride ion curing agents provided in Examples 1 to 4 with a composite doping property all showed a better chloride ion curing amount than the single-component CaFeAl-LDO or single-component nano-silica sol and the blank group. This is because the calcined CaFeAl-LDO component in the composite system can effectively cure chloride ions based on the "structural memory function", and the nano-silica sol has good dispersibility, which can improve the density of the matrix and reduce the CO in the air. 2 Intrusion further improves the effective curing rate of chloride ions, and after the nano-silica sol is in-situ compounded with the calcined CaFeAl-LDO, the "structural memory function" of CaFeAl-LDO is improved by isolating the interlayers of the calcined CaFeAl-LDO, forming a synergistic mechanism and further improving the curing efficiency of chloride ions.

[0111] Table 2 Compressive strength of mortar (MPa)

[0112] Experimental group (-XX% indicates the amount of curing agent added) 28d mortar compressive strength / Mpa Example 1 - 1.0% 54.3 Example 1 - 5.0% 63.9 Example 2 - 1.0% 51.5 Example 2 - 5.0% 59.7 Example 3 - 1.0% 49.8 Example 3 - 5.0% 56.9 Example 4 - 1.0% 52.7 Example 4 - 5.0% 58.2 CaFeAl-LDO-1.0% 52.1 CaFeAl-LDO-5.0% 56.9 Modified Nano-Silica Sol-1.0% 54.4 Modified Nano-Silica Sol-5.0% 60.7 Blank group (no chloride ion curing agent added) 45.8

[0113] It can be concluded from Table 2 that when the dosage of the chloride ion curing agent increases from 1.0% to 5.0%, the compressive strength of the mortar generally shows an increasing trend; comparing the composite chloride ion curing agents of these different processes, when the dosage of the chloride ion curing agent provided in Example 1 is 5.0%, the compressive strength of the mortar is significantly improved, and the compressive strength of the 28d sample reaches 63.9MPa, which is 17.7% and 39.5% higher than that of the chloride ion curing agent provided in Example 1 with a dosage of 1.0% and the blank group, respectively; this shows that the chloride ion curing agent provided by the present invention can not only effectively cure chloride ions, but also significantly improve the compressive strength.

[0114] On the one hand, micro-nanoscale CaFeAl-LDO can compact the pore structure of the matrix, and the restored 2D thin-layer CaFeAl-LDHs can block the transmission channel of chloride ions, increase the curvature of the capillary pores, and thus improve the strength; on the other hand, the modified nano-silica sol has high dispersibility, which facilitates the uniform dispersion of CaFeAl-LDO and cement particles in the slurry. At the same time, the nano-silica sol can also react with the hydroxide of the cement slurry to generate CSH gel, which significantly improves its mechanical properties.

[0115] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been presented as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-efficiency chloride ion curing agent for sea sand mortar, It is characterized in that The chloride ion curing agent is a CaFeAl-LDO / nano-silica sol composite material, wherein the mass ratio of CaFeAl-LDO to nano-silica sol is (45-65): (2-12); The chloride ion curing agent is obtained by co-precipitation of a metal cation solution, an alkaline solution and a modified nano-silica sol solution; The preparation method specifically comprises the following steps: Dissolve a soluble calcium source, a soluble iron source and a soluble aluminum source in water to prepare a solution A; dissolve an inorganic base in water to prepare a solution B; Weigh a certain amount of modified nano-silica sol, marked as solution C; add solution A, solution B and solution C into the container dropwise at the same time and stir continuously; after all the additions are completed, continue to stir evenly; After being stirred evenly, it is heated to make its grains grow, forming lamellar LDHs with a thin layer structure; After the reaction is completed, filtering, drying and calcining are performed to obtain the CaFeAl-LDO / nano-silica sol composite material; The modified nano-silica sol is obtained by modifying the nano-silica sol with a silane coupling agent; The calcination temperature is 600-750° C., and the calcination time is 2-6 hours.

2. A method for preparing a high-efficiency chloride ion curing agent for sea sand mortar according to claim 1, It is characterized in that The molar ratio of the soluble calcium source, the soluble iron source, the soluble aluminum source, the inorganic base and the modified nano-silica sol is: (18-26): (2-4): (5-10): (38-54): (2-12).

3. A method for preparing a high-efficiency chloride ion curing agent for sea sand mortar according to claim 1, It is characterized in that The anions of the soluble calcium source, the soluble iron source and the soluble aluminum source are any one of nitrate, nitrite, bromide or formate.

4. A method for preparing a high-efficiency chloride ion curing agent for sea sand mortar according to claim 1, It is characterized in that The dropping speed of the A solution is (10-30) drops / min, the dropping speed of the B solution is (10-30) drops / min, and the dropping speed of the C solution is (4-12) drops / min.

5. A method for preparing a high-efficiency chloride ion curing agent for sea sand mortar according to claim 1, It is characterized in that The inorganic base is any one of sodium hydroxide, potassium hydroxide or lithium hydroxide.

6. A method for preparing a high-efficiency chloride ion curing agent for sea sand mortar according to claim 1, It is characterized in that The heating temperature is 100-110° C., and the reaction time is 24-48 hours.

7. A method for applying the chloride ion curing agent prepared by any one of the preparation methods of claims 1 to 6, It is characterized in that The CaFeAl-LDO / nano silica sol composite material is mixed into cement, and the mixing amount is 1-5% of the cement mass.

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