Concrete shrinkage and deformation compensation material, preparation method and application

Abstract

The application provides a concrete shrinkage and deformation compensation material, a preparation method and application; the concrete shrinkage and deformation compensation material comprises the following components in percentage by mass: low-heat micro-expansion cement clinker 10-35%, magnesium oxide 15-40%, semi-hydrated gypsum 20-35%, anhydrous gypsum 5-15%, tuff powder 10-30%, nano silicon dioxide 4-15%, modified calcium lignosulfonate 0.1-0.5% and basalt fiber 1-4%; the modified calcium lignosulfonate is prepared from sulfite pulping waste liquid through concentration and drying, and the reducing sugar content is 6-14%; the concrete shrinkage and deformation compensation material can realize temperature shrinkage compensation in the whole period when applied to subway mass concrete, has excellent crack resistance and anti-seepage performance, and has significant engineering application value.

Description

Technical Field

[0001] This invention relates to the field of concrete materials technology, specifically to a concrete shrinkage deformation compensation material, its preparation method, and its application. Background Technology

[0002] Concrete is the most widely used building material in construction engineering. Due to its large volume and poor thermal conductivity, the heat of hydration generated by cement hydration is difficult to dissipate quickly, creating a temperature difference (temperature gradient) between the inside and outside. During the temperature drop and shrinkage process, tensile stress is easily generated inside the concrete. When the tensile stress exceeds the tensile strength of the concrete or the shrinkage deformation exceeds the ultimate tensile value of the concrete, cracks will appear. In particular, large-volume concrete is more prone to penetrating cracks when subjected to strong constraints during the temperature drop, which is even more harmful. For subway large-volume concrete, due to its high design strength grade (≥C45) and large cement content (>300kg / m³), 3 The subway typically uses P·O42.5 ordinary Portland cement with high heat of hydration, whose internal temperature can reach over 70℃ (heat rise of cement hydration + placement temperature). Combined with dense reinforcement and the strong constraint formed by the foundation, the large shrinkage deformation during temperature drop makes it more prone to cracking, leading to water seepage and even structural safety issues, seriously affecting the normal operation of the subway. Currently, in large-volume concrete projects, the application of expansion agents and other anti-cracking auxiliary materials is affected by various factors, resulting in difficulties in controlling the expansion performance and effectiveness, and the crack resistance effect needs improvement. In particular, achieving full-time shrinkage compensation throughout the temperature drop process is still under continuous improvement; failure to achieve effective shrinkage compensation at any stage can lead to concrete cracking.

[0003] Therefore, by rationally formulating materials with components that have expansion, crack resistance, and shrinkage reduction properties, it is of great significance to develop a material suitable for compensating for temperature shrinkage of large-volume concrete in subways throughout the entire time period. This is of great significance for improving the microstructure of subway and similar large-volume concrete, enhancing crack resistance and seepage prevention capabilities, achieving full-time compensation for temperature drop shrinkage deformation, and avoiding concrete cracking. Summary of the Invention

[0004] This invention proposes a concrete shrinkage deformation compensation material, its preparation method, and its application, which solves the defects of existing expansion agents and other anti-cracking auxiliary materials, such as difficulty in controlling the expansion performance and effect, poor crack resistance, and short duration of action.

[0005] The technical solution of this invention is implemented as follows:

[0006] The first aspect of this invention is to provide a concrete shrinkage deformation compensation material, comprising, by mass percentage: 10-35% low-heat micro-expansion cement clinker, 15-40% magnesium oxide, 20-35% hemihydrate gypsum, 5-15% anhydrous gypsum, 10-30% tuff powder, 4-15% nano-silica, 0.1-0.5% modified calcium lignosulfonate, and 1-4% basalt fiber; wherein the modified calcium lignosulfonate is obtained by concentrating and drying sulfite pulping waste liquid, and has a reducing sugar content of 6-14%.

[0007] Furthermore, the low-heat micro-expansion cement clinker contains ≥40% dicalcium silicate and ≤8% tricalcium aluminate.

[0008] Furthermore, the magnesium oxide is lightly calcined magnesium oxide with a specific surface area ≥ 400 m². 2 / kg; and / or, the specific surface area of ​​the tuff powder is ≥400m². 2 / kg.

[0009] Furthermore, the particle size of the nano-silica ranges from 1 to 100 nm.

[0010] Furthermore, the density of the basalt fiber is 1.80 g / cm³. 3 .

[0011] Furthermore, by mass ratio, the calcium lignin sulfonate component also includes 60-80% calcium lignin sulfonate, 5-15% hemicellulose, and 5-15% inorganic salts.

[0012] The second aspect of this invention is to provide a method for preparing the above-mentioned concrete shrinkage deformation compensation material, comprising the following steps: mixing and grinding low-heat micro-expansion cement clinker, magnesium oxide, hemihydrate gypsum, anhydrous gypsum, tuff powder, nano-silica and calcium lignosulfonate in proportion to obtain a powdered material; then adding basalt fiber and the obtained powdered material in proportion to a mixer and stirring to disperse the basalt fiber evenly to obtain the concrete shrinkage deformation compensation material.

[0013] Furthermore, in the above preparation method, the specific surface area of ​​the powdered material obtained after mixing and milling is ≥400m². 2 / kg.

[0014] A third aspect of this invention is to propose the application of the above-described concrete shrinkage deformation compensation material in temperature shrinkage compensation of large-volume concrete in subways.

[0015] A fourth aspect of the present invention is to provide a large-volume concrete for subways, comprising a gel material; said gel material comprising the concrete shrinkage deformation compensation material described in the first aspect.

[0016] Furthermore, the mass ratio of the concrete shrinkage deformation compensation material in the gel material is 8-12%; the amount of concrete shrinkage deformation compensation material added is adapted to different types of large-volume concrete.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. The concrete shrinkage deformation compensation material provided by this invention uses low-heat micro-expansion cement clinker, gypsum, and magnesium oxide as expansion components, nano-silica and tuff powder as components to improve pore structure, increase density and improve crack resistance, basalt fiber as crack-resistant and toughening component, and modified calcium lignosulfonate as grinding aid, water-reducing, shrinkage-reducing and temperature-lowering peak component. It can be used in the preparation of large-volume concrete for subways to overcome the crack resistance and seepage prevention performance required due to temperature shrinkage.

[0019] 2. The concrete shrinkage deformation compensation material provided by this invention can achieve full-time temperature shrinkage compensation when applied to large-volume concrete in subways. It has excellent crack resistance and seepage prevention performance and has significant engineering application value. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] In the first embodiment, a concrete shrinkage deformation compensation material is provided, comprising the following components by mass percentage: 10-35% low-heat micro-expansion cement clinker, 15-40% magnesium oxide, 20-35% hemihydrate gypsum, 5-15% anhydrous gypsum, 10-30% tuff powder, 4-15% nano-silica, 0.1-0.5% modified calcium lignosulfonate, and 1-4% basalt fiber; wherein the modified calcium lignosulfonate is obtained by concentrating and drying sulfite pulping waste liquid, and has a reducing sugar content of 6-14%.

[0022] In the above embodiments, the concrete shrinkage deformation compensation material uses gypsum and low-heat micro-expansion cement clinker as early expansion components and magnesium oxide as a later expansion component, and is rationally formulated to effectively compensate for the shrinkage deformation of large-volume subway concrete during the temperature drop process throughout the entire time period. The addition of nano-silica improves the interface structure, pore structure, and density of the concrete, enhancing its crack resistance and impermeability. The addition of modified calcium lignosulfonate reduces early shrinkage deformation, improves the workability of the concrete mix, lowers the initial hydration heat peak, and enhances the grinding effect. The addition of tuff powder improves the pore structure and density of the concrete, and regulates the structure and expansion characteristics of hydration products. The addition of basalt fiber enhances the tensile deformation capacity of the concrete, prevents the occurrence of micro-cracks, and improves the crack resistance and impermeability of the concrete. Ultimately, this achieves the goal of compensating for the shrinkage deformation of large-volume subway concrete during the temperature drop throughout the entire time period and preventing cracks in large-volume subway concrete.

[0023] In a preferred embodiment, the magnesium oxide is light-calcined magnesium oxide, which is produced by calcining and grinding periclase at a high temperature of 1000-1200℃, and has a specific surface area ≥400m². 2 / kg.

[0024] In a preferred embodiment, the low-heat micro-expansion cement clinker contains ≥40% dicalcium silicate and ≤8% tricalcium aluminate.

[0025] In a preferred embodiment, the tuff powder is produced by grinding tuff with pozzolanic aluminosilicate properties, and its specific surface area is ≥400 m². 2 / kg. The nano-silica is a white powder or granular material with a particle size ranging from 1 to 100 nm.

[0026] In a preferred embodiment, the modified calcium lignosulfonate is a light yellow powder, produced by concentrating and drying sulfurous pulping waste liquid. Its components include calcium lignosulfonate, reducing sugars, hemicellulose, and inorganic salts, with a mass ratio of 60-80% : 6-14% : 5-15% : 5-15%. The modification method involves appropriately reducing the sugar content to control excessive retardation. The purpose of using modified calcium lignosulfonate, besides ensuring the required fluidity for compensating for temperature shrinkage in large-volume subway concrete, is to reduce plastic deformation, lower the initial hydration heat peak, and improve the grinding effect.

[0027] In a preferred embodiment, the basalt fiber is a fiber material made from basalt ore as raw material, melted at a high temperature of 1450-1500℃ and then drawn through a platinum-rhodium alloy stencil. It is primarily composed of silicon dioxide and aluminum oxide, with a density of approximately 1.80 g / cm³. 3 about.

[0028] In the second embodiment, a method for preparing the above-mentioned concrete shrinkage deformation compensation material is provided. First, low-heat micro-expansion cement clinker, magnesium oxide, hemihydrate gypsum, anhydrous gypsum, tuff powder, nano-silica and calcium lignosulfonate are mixed and ground evenly in proportion to obtain a powdered material. Then, basalt fiber and the obtained powdered material are added to a mixer in proportion and stirred to disperse the basalt fiber evenly to obtain the concrete shrinkage deformation compensation material.

[0029] In the above preparation examples, the specific surface area of ​​the powdered material obtained after mixing and grinding was ≥400 m². 2 / kg.

[0030] In another embodiment, a large-volume subway concrete is provided, comprising a gel material and admixtures, wherein the gel material includes the concrete shrinkage deformation compensation material described in the first embodiment. The compensation material can achieve full-time temperature shrinkage compensation and exhibits excellent crack resistance and impermeability. Preferably, the compensation material accounts for 8-12% of the mass of the cementitious material.

[0031] The following are preferred implementation examples. As a preferred option of this solution, unless otherwise specified, all materials used are commercially available standard building materials, and the methods or approaches used in material preparation and construction are basic techniques mastered by those skilled in the art.

[0032] Example 1

[0033] A concrete shrinkage deformation compensation material is provided, comprising the following components by mass: 13 parts low-heat micro-expansion cement clinker, 32 parts magnesium oxide, 24 parts hemihydrate gypsum, 8 parts anhydrous gypsum, 12 parts tuff powder, 9 parts nano-SiO2, 1.8 parts basalt fiber, and 0.2 parts modified calcium lignosulfonate, totaling 100 parts; wherein, in the modified calcium lignosulfonate, the mass fractions of calcium lignosulfonate, reducing sugar, hemicellulose, and inorganic salt are 80%, 10%, 5%, and 5%, respectively.

[0034] Example 2

[0035] A concrete shrinkage deformation compensation material is provided, with the following component mass ratio: 30 parts low-heat micro-expansion cement clinker, 20 parts magnesium oxide, 20 parts hemihydrate gypsum, 5 parts anhydrous gypsum, 17 parts tuff powder, 5 parts nano-SiO2, 2.5 parts basalt fiber, and 0.5 parts modified calcium lignosulfonate, totaling 100 parts; wherein, in the modified calcium lignosulfonate, the mass fractions of calcium lignosulfonate, reducing sugar, hemicellulose, and inorganic salts are 70%, 14%, 7%, and 9%, respectively.

[0036] Example 3

[0037] A concrete shrinkage deformation compensation material is provided, with the following component mass ratio: 20 parts low-heat micro-expansion cement clinker, 15 parts magnesium oxide, 30 parts hemihydrate gypsum, 12 parts anhydrous gypsum, 15 parts tuff powder, 6 parts nano-SiO2, 1.7 parts basalt fiber, and 0.3 parts modified calcium lignosulfonate, totaling 100 parts; wherein, in the modified calcium lignosulfonate, the mass fractions of calcium lignosulfonate, reducing sugar, hemicellulose, and inorganic salt are 66%, 4%, 15%, and 15%, respectively.

[0038] Comparative Example 1 (Increased reducing sugar content in modified calcium lignosulfonate)

[0039] A concrete shrinkage deformation compensation material is provided, with the following component mass ratio: 30 parts low-heat micro-expansion cement clinker, 20 parts magnesium oxide, 20 parts hemihydrate gypsum, 5 parts anhydrous gypsum, 17 parts tuff powder, 5 parts nano-SiO2, 2.5 parts basalt fiber, and 0.5 parts modified calcium lignosulfonate, totaling 100 parts; wherein, in the modified calcium lignosulfonate, the mass fractions of calcium lignosulfonate, reducing sugar, hemicellulose, and inorganic salt are 70%, 18%, 7%, and 5%, respectively.

[0040] Comparative Example 2 (reduced reducing sugar content in modified calcium lignosulfonate)

[0041] A concrete shrinkage deformation compensation material is provided, with the following component mass ratio: 13 parts low-heat micro-expansion cement clinker, 32 parts magnesium oxide, 24 parts hemihydrate gypsum, 8 parts anhydrous gypsum, 12 parts tuff powder, 9 parts nano-SiO2, 1.8 parts basalt fiber, and 0.2 parts modified calcium lignosulfonate, totaling 100 parts; wherein, in the modified calcium lignosulfonate, the mass fractions of calcium lignosulfonate, reducing sugar, hemicellulose, and inorganic salts are 80%, 2%, 5%, and 13%, respectively.

[0042] Comparative Example 3 (without modified calcium lignosulfonate)

[0043] A concrete shrinkage deformation compensation material is provided, with the following component mass ratio: 13 parts low-heat micro-expansion cement clinker, 32 parts magnesium oxide, 24 parts hemihydrate gypsum, 8 parts anhydrous gypsum, 12 parts tuff powder, 9 parts nano-SiO2, 1.8 parts basalt fiber, 0.2 parts fly ash, totaling 100 parts.

[0044] Comparative Example 4 (excluding basalt fiber)

[0045] A concrete shrinkage deformation compensation material is provided, with the following component mass ratio: 13 parts low-heat micro-expansion cement clinker, 32 parts magnesium oxide, 24 parts hemihydrate gypsum, 8 parts anhydrous gypsum, 12 parts tuff powder, 9 parts nano-SiO2, 1.8 parts fly ash, and 0.2 parts modified calcium lignosulfonate, totaling 100 parts; wherein, in the modified calcium lignosulfonate, the mass fractions of calcium lignosulfonate, reducing sugar, hemicellulose, and inorganic salts are 80%, 10%, 5%, and 5%, respectively.

[0046] Comparative Example 5 (excluding tuff powder, nano-SiO2)

[0047] A concrete shrinkage deformation compensation material is provided, with the following component mass ratio: 13 parts low-heat micro-expansion cement clinker, 32 parts magnesium oxide, 24 parts hemihydrate gypsum, 8 parts anhydrous gypsum, 21 parts fly ash, 1.8 parts basalt fiber, and 0.2 parts modified calcium lignosulfonate, totaling 100 parts; wherein, in the modified calcium lignosulfonate, the mass fractions of calcium lignosulfonate, reducing sugar, hemicellulose, and inorganic salts are 80%, 10%, 5%, and 5%, respectively.

[0048] Comparative Example 6 (excluding plaster)

[0049] A concrete shrinkage deformation compensation material is provided, with the following component mass ratio: 13 parts low-heat micro-expansion cement clinker, 32 parts magnesium oxide, 32 parts fly ash, 12 parts tuff powder, 9 parts nano-SiO2, 1.8 parts basalt fiber, and 0.2 parts modified calcium lignosulfonate, totaling 100 parts; wherein, in the modified calcium lignosulfonate, the mass fractions of calcium lignosulfonate, reducing sugar, hemicellulose, and inorganic salts are 80%, 10%, 5%, and 5%, respectively.

[0050] Comparative Example 7 (Does not contain magnesium oxide)

[0051] A concrete shrinkage deformation compensation material is provided, with the following component mass ratio: 30 parts low-heat micro-expansion cement clinker, 20 parts fly ash, 20 parts hemihydrate gypsum, 5 parts anhydrous gypsum, 17 parts tuff powder, 5 parts nano-SiO2, 2.5 parts basalt fiber, and 0.5 parts modified calcium lignosulfonate, totaling 100 parts; wherein, in the modified calcium lignosulfonate, the mass fractions of calcium lignosulfonate, reducing sugar, hemicellulose, and inorganic salts are 70%, 14%, 7%, and 9%, respectively.

[0052] Experimental Example 1

[0053] An analysis of the effectiveness of using C45 mass concrete for the foundation slab of a subway project in a southern city as a material for all-time temperature shrinkage compensation in subway mass concrete is conducted. (C45 mass concrete, 1m³) 3The proportions of each material in the concrete mix are as follows: water 144kg, cement 307kg, fly ash 125kg, crushed stone 1032kg, natural sand 700kg, high-performance retarder and water-reducing agent 8.64kg, and compensating material 48.0kg.

[0054] Preparation steps of C45 large-volume concrete for subway foundation slab:

[0055] 1) Weigh the cement, fly ash, and comparison components according to the proportions of the blank group and the comparison group, and pour them into the concrete mixer. Dry mix for 30-60 seconds until the color is uniform.

[0056] 2) Add crushed stone and natural sand to the concrete mixer according to the proportion and dry mix for 30-60 seconds until evenly mixed;

[0057] 3) Finally, add water and high-performance retarder to the concrete mixer according to the proportion and continue mixing for 90-120 seconds to obtain the concrete mixture.

[0058] The performance tests of large-volume concrete for subways were conducted in accordance with the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081-2019) and the "Test Procedures for Hydraulic Concrete" (SL352-2020). The concrete performance tests included the slump, compressive strength, tensile strength, tensile modulus of elasticity, and ultimate tensile strength of the concrete mixture, as shown in Table 1. The thermal temperature rise test performance was shown in Table 2. The autogenous volume deformation test was shown in Table 3. The water absorption kinetics method was used to determine the concrete pore structure parameters, and the test results are shown in Table 4.

[0059] Table 1:

[0060]

[0061] Table 2:

[0062]

[0063] Table 3:

[0064]

[0065]

[0066] Table 4 (Pore Structure)

[0067]

[0068] Analysis and Conclusion:

[0069] It is easy to see from Tables 1-4 that the dosage of each component of the concrete shrinkage deformation compensation material obtained in Examples 1-3 varies within a certain range and has a certain impact on some properties of concrete, but the impact is not significant and all meet the performance requirements of large-volume concrete for subways. The specific proportion and dosage of each component are determined by factors such as concrete performance requirements and the amount of cementitious materials used.

[0070] As can be seen from Table 1, compared to Example 2, the increase in reducing sugar content in the calcium lignosulfonate added in Comparative Example 1 mainly reduces the early strength (3-day compressive strength) of concrete and affects the construction process. This indicates that the increased sugar content has a retarding effect on the setting of the concrete mixture, thus significantly affecting the early strength of the concrete. Furthermore, Table 3 shows that the increase in reducing sugar content in the calcium lignosulfonate added in Comparative Example 1 also affects early autogenous volume deformation, which is detrimental to early crack prevention. In Table 1, the decrease in reducing sugar content in the calcium lignosulfonate added in Comparative Example 2 reduces its retarding effect and improves the early strength of the concrete to a certain extent. However, Table 2 shows that the initial adiabatic temperature rise in Comparative Example 2 increases, which is detrimental to early crack prevention. Comparative Example 3, without modified calcium lignosulfonate, loses its water-reducing effect. Because the compensating material contains fibers and nano-SiO2 materials with high water requirements, the fluidity of the concrete mixture is greatly reduced, failing to meet the construction requirements of concrete. Simultaneously, Table 2 shows an increased initial adiabatic temperature rise, which is detrimental to early crack prevention. It is evident that the addition of modified calcium lignosulfonate can improve the water reduction effect, but the overall impact needs to be considered when adding it, and it only meets the requirements within an appropriate range.

[0071] In Comparative Example 4, without basalt fiber, the tensile strength and ultimate tensile value of the concrete were reduced to varying degrees (Table 1), affecting the crack resistance and impermeability of the concrete.

[0072] In Comparative Example 5, which did not contain tuff powder or nano-SiO2, the tensile strength and ultimate tensile value of the concrete were reduced to varying degrees (Table 1), and the pore structure deteriorated (Table 4), affecting the concrete's impermeability and crack resistance.

[0073] Furthermore, it is evident from Table 3 that in Comparative Example 6, without gypsum, the primary effect is on the early autogenous volume deformation of the concrete, failing to effectively compensate for early shrinkage deformation. In Comparative Example 7, without magnesium oxide, the primary effect is on the later autogenous volume deformation of the concrete, failing to effectively compensate for later shrinkage deformation. In other words, the combined effect of gypsum and magnesium oxide demonstrates compensation throughout the entire timeframe.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A concrete shrinkage deformation compensation material, characterized in that, The components by mass percentage include: 10-35% low-heat micro-expansion cement clinker, 15-40% magnesium oxide, 20-35% hemihydrate gypsum, 5-15% anhydrous gypsum, 10-30% tuff powder, 4-15% nano-silica, 0.1-0.5% modified calcium lignosulfonate, and 1-4% basalt fiber; the modified calcium lignosulfonate is obtained by concentrating and drying sulfite pulping waste liquid, and has a reducing sugar content of 6-14%.

2. The concrete shrinkage deformation compensation material as described in claim 1, characterized in that, The low-heat micro-expansion cement clinker contains ≥40% dicalcium silicate and ≤8% tricalcium aluminate.

3. The concrete shrinkage deformation compensation material as described in claim 1, characterized in that, The magnesium oxide is lightly calcined magnesium oxide with a specific surface area ≥400 m². 2 / kg; and / or, the specific surface area of ​​the tuff powder is ≥400m². 2 / kg.

4. The concrete shrinkage deformation compensation material as described in claim 1, characterized in that, The particle size of the nano-silica ranges from 1 to 100 nm.

5. The concrete shrinkage deformation compensation material as described in claim 1, characterized in that, The density of the basalt fiber is 1.80 g / cm³. 3 .

6. The concrete shrinkage deformation compensation material as described in claim 1, characterized in that, The modified calcium lignosulfonate component comprises, by mass ratio, 60-80% calcium lignosulfonate, 5-15% hemicellulose, and 5-15% inorganic salts.

7. The method for preparing the concrete shrinkage deformation compensation material according to claim 1, characterized in that, The process includes the following steps: mixing and grinding low-heat micro-expansion cement clinker, magnesium oxide, hemihydrate gypsum, anhydrous gypsum, tuff powder, nano-silica and calcium lignosulfonate in proportion to obtain a powdered material; then adding basalt fiber and the obtained powdered material into a mixer in proportion and stirring to disperse the basalt fiber evenly to obtain a concrete shrinkage deformation compensation material.

8. The application of the concrete shrinkage deformation compensation material according to any one of claims 1 to 6 in temperature shrinkage compensation of large-volume concrete in subways.

9. A type of large-volume concrete for subways, comprising a gel material, characterized in that, The gel material includes the concrete shrinkage deformation compensation material according to any one of claims 1 to 6.

10. The large-volume concrete for subway construction according to claim 9, characterized in that, In the gel material, the mass ratio of concrete shrinkage deformation compensation material is 8-12%.

Images