Concrete repairing agent and preparation method thereof

Abstract

The invention discloses a concrete repairing agent, which is prepared from the following raw materials in parts by weight: 110 to 130 parts of sulphoaluminate cement, 6 to 10 parts of modified pine needle fiber powder, 20 to 30 parts of calcium sulfate whiskers, 40 to 60 parts of superfine slag powder, 5 to 8 parts of additives and 45 to 55 parts of water, the modified pine needle fiber powder is obtained by modifying pine needle fiber powder with calcium nitrate-sodium silicate modified liquid and nano calcium carbonate. The sulphoaluminate cement is adopted as a main gelling component, and is combined with rigid-flexible reinforcing components based on the modified pine needle fiber powder and the calcium sulfate whiskers, so that the obtained concrete repairing agent has good early strength, bonding strength and durability, and is suitable for the fields of road emergency repair, bridge repair and the like.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a concrete repair agent and its preparation method. Background Technology

[0002] Concrete, as the most important structural material in civil engineering, is prone to cracking, spalling, and strength reduction during long-term service due to factors such as load, environmental erosion, and construction defects, seriously affecting structural safety and durability. Concrete repair agents, as key materials for quickly restoring structural function, are widely used in road emergency repairs, bridge bearing repairs, and industrial floor maintenance. Their performance directly determines repair efficiency and project lifespan. Current market demands for repair agents focus on four core aspects: rapid hardening and early strength, high bond strength, low shrinkage and high crack resistance, and good durability.

[0003] Patent CN102898107B discloses a concrete repair agent that uses special cement, nanomaterials, and highly active substances to achieve internal penetration and densification of concrete; however, the excessive proportion of fine aggregate in the formula leads to insufficient early strength, making it difficult to meet the needs of emergency repairs. Patent application CN111187041A discloses a concrete repair agent with a high proportion of organic components, which affects durability. Further exploration of concrete repair agents with high early strength, high bond strength, and good durability is of significant research and application importance. Summary of the Invention

[0004] The main objective of this invention is to provide a concrete repair agent that can achieve good early strength, bond strength and durability, and is suitable for emergency road repair, bridge repair and other fields.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A concrete repair agent, comprising the following raw materials and their respective weight proportions: 110-130 parts of sulfoaluminate cement, 6-10 parts of modified pine needle fiber powder, 20-30 parts of calcium sulfate whiskers, 40-60 parts of ultrafine slag powder, 5-8 parts of admixture, and 45-55 parts of water; wherein the modified pine needle fiber powder is obtained by modifying pine needle fiber powder with calcium nitrate-sodium silicate modifying liquid and nano-calcium carbonate.

[0006] According to the above scheme, in the preparation process of modified pine needle fiber powder, the mass ratio of pine needle fiber, calcium nitrate, sodium silicate and nano calcium carbonate is 100:5~10:8~15:0.5~1.

[0007] According to the above scheme, in the calcium nitrate-sodium silicate modified solution, the concentration of calcium nitrate is 7~18wt% and the concentration of sodium silicate is 5~20wt%.

[0008] According to the above scheme, the specific steps for modifying pine needle fibers are as follows: 1) Dry the pine needle fibers (100~105℃, 1~2h), ball mill them, and then pass them through an 80-mesh sieve to obtain pine needle fiber powder with a length of 0.1~0.5mm and a diameter of 10~30μm; 2) Add calcium nitrate and sodium silicate to water and mix well to obtain calcium nitrate-sodium silicate modified solution; 3) Add the obtained pine needle fiber powder to the calcium nitrate-sodium silicate modified solution, heat and stir, and uniformly add nano-calcium carbonate during the stirring process to obtain a modified pine needle fiber powder solution. 4) Dry the obtained modified pine needle fiber powder solution, and then heat it for shaping treatment to obtain modified pine needle fiber powder.

[0009] In the above scheme, the pine needle fiber length is 4~10mm and the density is 0.8~1.2g / cm³. 3 Between these values, the cellulose content is 35-45 wt%, and the lignin content is 20-30 wt%. In the above scheme, the heating and stirring temperature is 60~80℃, and the time is 1~2h.

[0010] In the above scheme, the drying temperature in step 4) is 50~60℃ and the time is 1~2h; the shaping treatment temperature is 80~90℃ and the time is 30~60min.

[0011] In the above scheme, the 28-day compressive strength of sulfoaluminate cement is ≥45MPa, and the specific surface area is ≥350m². 2 / kg, initial setting time ≥30min.

[0012] In the above scheme, the aspect ratio of calcium sulfate whiskers is 30~60, the diameter of a single filament is 5~10μm, and the calcium sulfate content is ≥95wt%.

[0013] In the above scheme, the specific surface area of ​​the ultrafine slag powder is greater than 620m². 2 / kg, with an activity index greater than 100% after 28 days, of which the vitreous content is greater than 90 wt%.

[0014] In the above scheme, the admixture includes cellulose ether and water-reducing agent, wherein the amount of cellulose ether is 2 to 5% of the mass of the admixture.

[0015] Furthermore, the water-reducing agent is a polycarboxylate water-reducing agent with a solid content ≥25%.

[0016] The present invention also provides a method for preparing the above-mentioned concrete repair agent, comprising the following steps: 1) Weigh the raw materials according to the proportion. The raw materials and their weight percentages include: 110-130 parts of sulfoaluminate cement, 6-10 parts of modified pine needle fiber powder, 20-30 parts of calcium sulfate whiskers, 40-60 parts of ultrafine slag powder, 5-8 parts of admixture, and 45-55 parts of water. 2) Weigh out the sulfoaluminate cement and ultrafine slag powder and dry mix them evenly (2~3 min). Then add calcium sulfate whiskers and modified pine needle fiber powder and continue to dry mix evenly (2~3 min). Add some water (accounting for 40~50% of the total water volume) and stir evenly (2~3 min). Finally, add the mixture of admixture and remaining water and stir evenly (3~5 min) to obtain concrete repair agent.

[0017] The concrete repair agent prepared according to the above scheme has an early 1-day strength that is more than 25% higher than that of the traditional scheme, a shrinkage rate that is more than 30% lower, and a bond strength that is more than 50% higher. It can achieve a balance of four core properties: rapid hardening and early strength, high bond strength, low shrinkage and crack resistance, and durability and stability. It can effectively meet the high-efficiency repair needs of scenarios such as road emergency repair, bridge repair, and industrial floor maintenance, and solve the key problems of insufficient early strength and poor durability in existing technologies.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) Calcium sulfate whiskers, as rigid inorganic fibers in the system, can improve the mechanical properties of the matrix through "skeleton support". Combined with modified pine needle fiber powder (flexible natural fiber), after being modified by calcium nitrate-sodium silicate, active groups such as hydroxyl groups are formed on the surface, which can effectively improve the compatibility with the inorganic matrix, relieve shrinkage stress, enhance overall toughness, and effectively inhibit the generation of micro cracks. This solves the problem that traditional repair agents cannot effectively balance strength and crack resistance, while avoiding the defects such as poor compatibility between ordinary organic fibers and inorganic matrices.

[0019] 2) The modified pine needle fiber powder introduces polar groups (silanol, hydroxyl, etc.) on its surface and provides anchor points for nanomolecules, which can effectively eliminate interfacial defects between it and the inorganic matrix and greatly improve its interfacial bonding ability with the cement matrix. Sulfoaluminate cement and modified pine needle fiber powder can promote each other and play a role in rapid early setting and early strength. In addition, the introduced modified pine needle fiber can effectively promote the continuous generation of CSH gel and inhibit the problems of "shrinkage" in the later strength that are easily caused by sulfoaluminate cement.

[0020] 3) The introduced ultrafine slag powder reacts with the hydration products of sulfoaluminate cement to generate CSH gel that fills the pores. Its micro-aggregate effect and the skeleton support of calcium sulfate whiskers work together to form a "nano-micro" multi-level dense structure, which can significantly improve the density of the system, block the penetration path of corrosive media, further significantly improve durability, and achieve long-term stable service. Detailed Implementation

[0021] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. These descriptions are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0022] In the following examples, the cement used is 42.5 grade sulfoaluminate cement, with a 28-day compressive strength of 51.6 MPa, an initial setting time of 38 min, and a specific surface area of ​​363 m². 2 / kg; the specific surface area of ​​ultrafine slag powder is 642kg / m² 3 The 28-day activity index was 104%, and the vitreous content was 93.2 wt%. The average length of the pine needle fibers was 6.4 mm, and the density was 0.95 g / cm³. 3 Between these values, the cellulose content was 37.8 wt% and the lignin content was 26.6 wt%.

[0023] The calcium sulfate whiskers used had an average aspect ratio of 38 and an average diameter of 6.7 μm per filament; the calcium sulfate content was 96.4 wt%.

[0024] The admixtures include cellulose ether and polycarboxylate superplasticizer, with the cellulose ether content at 2.5% of the admixture mass; the superplasticizer has a solid content of 28.6% and a water reduction rate of 30.5%. In the following examples, the specific preparation steps of the modified pine needle fiber powder are as follows: ①Pine needle fibers are placed in an oven at 105℃ and dried for 1 hour. After being pulverized by a ball mill and passed through an 80-mesh sieve, pine needle fiber powder is obtained, with an average length of about 0.3 mm and an average diameter of about 14 μm. ② A 12wt% calcium nitrate solution and an 18wt% sodium silicate solution are mixed in a volume ratio of 1.5:1 to obtain a calcium nitrate-sodium silicate modified solution; ③ Add 100g of pine needle fiber powder to 130ml of calcium nitrate-sodium silicate modified solution, and stir magnetically in a 70℃ water bath for 1h. During the stirring process, add nano calcium carbonate with a mass fraction of 0.5% relative to the pine needle fiber powder to obtain a modified pine needle fiber powder solution. ④ Place the modified pine needle fiber powder solution into a tray and dry it at 60℃ for 1 hour. Then adjust the oven temperature to 90℃ for setting treatment (45 minutes) to obtain modified pine needle fiber powder.

[0025] Example 1 A concrete repair agent and its preparation method include the following steps: (1) Weigh the raw materials according to the proportion. The raw materials and their weight percentages include: 110 parts of sulfoaluminate cement, 6 parts of modified pine needle fiber powder, 20 parts of calcium sulfate whiskers, 40 parts of ultrafine slag powder, 5 parts of admixture, and 45 parts of water. (2) Weigh out the sulfoaluminate cement and ultrafine slag powder and dry mix for 2 minutes. Then add calcium sulfate whiskers and modified pine needle fiber powder and continue to dry mix for 2 minutes. Add water accounting for 40-50% of the total water volume and mix for 2 minutes. Finally, add the mixture of admixture and remaining water and mix for 5 minutes to obtain concrete repair agent.

[0026] Example 2 Example 2 is largely the same as Example 1 in terms of formulation and preparation method, with the only difference being: The raw materials and their respective weight percentages include: 130 parts sulfoaluminate cement, 10 parts modified pine needle fiber powder, 30 parts calcium sulfate whiskers, 60 parts ultrafine slag powder, 8 parts additives, and 55 parts water.

[0027] Example 3 Example 3 is largely the same as Example 1 in terms of formulation and preparation method, with the only difference being: The raw materials and their respective weight percentages include: 120 parts of sulfoaluminate cement, 8 parts of modified pine needle fiber powder, 24 parts of calcium sulfate whiskers, 50 parts of ultrafine slag powder, 6 parts of additives, and 50 parts of water.

[0028] Comparative Example 1 Comparative Example 1 and Example 1 have roughly the same proportions and preparation methods, with the only difference being: 1) The modified solution was prepared by mixing a 25wt% calcium nitrate solution and a 10wt% sodium silicate solution at a volume ratio of 1:1. 2) The amount of nano-calcium carbonate added accounts for 2% of the mass of pine needle fiber powder; 3) After mixing the modified solution, nano-calcium carbonate, and pine needle fiber powder evenly, the resulting dispersion is dried directly at 100°C for 2 hours.

[0029] Comparative Example 2 Comparative Example 2 is roughly the same as Example 1 in terms of formulation and preparation method, except that: calcium silicate powder is directly dissolved in water to prepare a calcium silicate solution with a concentration of 10wt%, 100g of pine needle fiber powder is added to 130mL of the above calcium silicate solution, and stirred in a water bath at 70℃ for 1h. During the stirring process, 0.5g of nano calcium carbonate is added evenly.

[0030] Comparative Example 3 Comparative Example 3 is roughly the same as Example 1 in terms of formulation and preparation method, except that calcium sulfate whiskers are not added.

[0031] Comparative Example 4 Comparative Example 4 is roughly the same as Example 1 in terms of proportions and preparation methods, except that sulfoaluminate cement is replaced with an equal mass of silicate cement.

[0032] Concrete repair agents prepared according to the above methods in Examples 1-3 and Comparative Examples 1-3 were tested for 1-day and 28-day compressive strength, initial fluidity, setting time, and bond strength according to standard methods. The bond strength was referenced to GB50367 "Code for Design of Strengthening Concrete Structures". The repair agent was poured onto the surface of 100mm×100mm×100mm old concrete test blocks, and the interface was pre-roughened. After curing for 7 days, splitting tensile tests were conducted using a compression testing machine, and the splitting tensile strength (MPa) was calculated. The experimental results are shown in Table 2 below. Table 2 Performance test results of Examples 1-3 and Comparative Examples 1-3

[0033] Analysis of the data in the table shows that the concrete repair agent obtained by this invention has the advantages of rapid setting and early strength, good bonding strength, and low shrinkage.

[0034] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A concrete repair agent, characterized by, The raw materials and the weight percentage thereof include: 110-130 parts of sulphoaluminate cement, 6-10 parts of modified pine needle fiber powder, 20-30 parts of calcium sulfate whisker, 40-60 parts of superfine slag powder, 5-8 parts of additive, and 45-55 parts of water; the modified pine needle fiber powder is obtained by modifying pine needle fiber powder with calcium nitrate-sodium silicate modification liquid and nano calcium carbonate.

2. The concrete repair material of claim 1, wherein In the modified pine needle fiber powder, the mass ratio of introduced pine needle fiber, calcium nitrate, sodium silicate and nano calcium carbonate is 100:5-10:8-15:0.5-1.

3. The concrete repair material of claim 1, wherein In the calcium nitrate-sodium silicate modification liquid, the concentration of calcium nitrate is 7-18 wt%, and the concentration of sodium silicate is 5-20 wt%.

4. The concrete repair material of claim 1, wherein The specific steps for modifying the pine needle fiber are as follows: 1) The pine needle fiber is dried, crushed, sieved, and pine needle fiber powder is obtained; 2) The calcium nitrate and sodium silicate are added to water and mixed uniformly to obtain a calcium nitrate-sodium silicate modification liquid; 3) The obtained pine needle fiber powder is added to the calcium nitrate-sodium silicate modification liquid, heated and stirred, and nano calcium carbonate is uniformly added during the stirring process to obtain a modified pine needle fiber powder solution 4) The obtained modified pine needle fiber powder solution is dried, then heated and shaped to obtain modified pine needle fiber powder.

5. The concrete repair material of claim 4, wherein the cementitious material is Portland cement. The length of the pine needle fiber is 4-10 mm, the density is between 0.8-1.2 g / cm 3 and the cellulose content is 35-45 wt%, the lignin content is 20-30 wt%.

6. The concrete repair material of claim 4, wherein The heating and stirring temperature is 60-80℃, and the time is 1-2h.

7. The concrete repair material of claim 4, wherein In step 4), the drying temperature is 50-60℃, and the time is 1-2h; the shaping treatment temperature is 80-90℃, and the time is 30-60min.

8. The concrete repair material of claim 1, wherein The aspect ratio of the calcium sulfate whisker is 30-60, and the single filament diameter is 5-10μm; the calcium sulfate content is ≥95wt%.

9. The concrete repair material of claim 1, wherein, The additive includes cellulose ether and water reducing agent, wherein the cellulose ether content is 2-5% of the mass of the additive.

10. A method of preparing the concrete repair material according to any one of claims 1 to 9, characterized in that, The method includes the following steps: 1) The raw materials are weighed according to the proportion, and the weight percentage of each raw material includes: 110-130 parts of sulphoaluminate cement, 6-10 parts of modified pine needle fiber powder, 20-30 parts of calcium sulfate whisker, 40-60 parts of superfine slag powder, 5-8 parts of additive, and 45-55 parts of water; 2) The weighed sulphoaluminate cement and superfine slag powder are dry mixed uniformly, then the calcium sulfate whisker and modified pine needle fiber powder are added and continue to be dry mixed uniformly, a part of water is added and stirred uniformly, and finally the mixture of additive and remaining water is added and stirred uniformly to obtain a concrete repair agent.

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