A high-strength cement-based composition, grout, and method of making and use thereof

Abstract

The application relates to a high-strength cement-based composition, a grouting material and a preparation method and application thereof, the high-strength cement-based composition comprising a cementitious binder, a water reducing agent, a defoaming agent, a composite expansion agent and graded aggregate; the cementitious binder comprises, in parts by weight, 30-35 parts of Portland cement, 2-6 parts of silica fume, 5-10 parts of nano-silica modified ultra-fine mineral powder and 2-6 parts of fly ash cenospheres; the graded aggregate is 47-52 parts; the mass ratio of the defoaming agent to the cementitious binder is 0.6-0.8%; the composite expansion agent comprises a plastic expansion agent, a calcium oxide-sulphoaluminate expansion agent and a magnesium oxide expansion agent; the sum of the mass of the plastic expansion agent and the calcium oxide-sulphoaluminate expansion agent accounts for 0.3-0.6% of the mass of the cementitious binder, and the mass of the magnesium oxide expansion agent accounts for 4-8% of the mass of the cementitious binder. The grouting material has the beneficial effects that the compressive strength and the interfacial bonding effect are considered, and the requirements of rapid construction and mechanical properties of modular buildings can be met.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a high-strength cement-based composition, grouting material, its preparation method and application. Background Technology

[0002] Cement-based grouting materials are widely used in equipment foundation fixing, concrete structure modification and reinforcement, emergency engineering repairs, and prestressed duct grouting. In recent years, they have been mainly used in modular buildings for filling joints and reinforcing structural connections. Modular buildings place higher demands on the structural integrity and construction efficiency of joints: on the one hand, the 1-day strength (≥35MPa) of A85 grade grouting materials is still insufficient to meet the early load-bearing capacity requirements of rapid assembly; on the other hand, its 28-day strength limit (85MPa) may not be sufficient to support the long-term safety of high-load or critical stress joints.

[0003] In the prior art, see patent application CN118324479A, which discloses an ultra-high strength offshore wind power grout containing solid waste-based cementitious materials and its preparation method. Although this grout improves the compressive strength of the grout to a certain extent, the steel slag-based reinforcing agent it uses has potential stability risks. Furthermore, although the high density and high elastic modulus of garnet sand are suitable for large-volume foundations of offshore wind power, they are not suitable for thin-walled joints in modular building casting, which can easily lead to stress concentration and cracking at the joints. In addition, the shrinkage rate of the grout is large between 28 days and 1 day, and the interfacial bonding effect is poor, making it impossible to balance compressive strength and interfacial bonding effect.

[0004] Current modular building grouting materials primarily evaluate their micro-expansion performance through 3-hour and 24-hour vertical expansion rates. However, this approach suffers from insufficient volume stability, which can lead to later shrinkage, cracking, or interface debonding, thereby weakening the integrity and durability of modular building joints. Therefore, existing grouting materials also exhibit technical problems such as insufficient expansion performance of the micro-expansion system and low early strength of the cementitious system. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a high-strength cement-based composition, grouting material, preparation method and application thereof, which solves the technical problems of insufficient strength and insufficient volume stability of existing cement-based grouting materials in modular buildings, leading to cracking or interface debonding.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0009] In a first aspect, embodiments of the present invention provide a high-strength cement-based composition, comprising a cementitious base material, a water-reducing agent, a defoamer, a composite expansion agent, and graded aggregates;

[0010] The cementitious base material includes, by weight: 30-35 parts silicate cement, 2-6 parts silica fume, 5-10 parts nano-silica modified ultrafine mineral powder, and 2-6 parts fly ash microspheres.

[0011] By weight, the graded aggregate is 47-52 parts;

[0012] The mass ratio of water-reducing agent to cementitious base material is 0.5-1.0%, and the mass ratio of defoamer to cementitious base material is 0.6-0.8%.

[0013] The composite expanding agent includes plastic expanding agent, calcium oxide-sulfoaluminate expanding agent and magnesium oxide expanding agent; among which, the sum of the mass of plastic expanding agent and calcium oxide-sulfoaluminate expanding agent accounts for 0.3-0.6% of the mass of cementitious base material, and magnesium oxide expanding agent accounts for 4-8% of the mass of cementitious base material.

[0014] In a preferred embodiment of the present invention, the high-strength cement-based composition includes a defoamer comprising a polyether defoamer and a polysiloxane defoamer, wherein the mass ratio of the polyether defoamer to the polysiloxane defoamer is 1:0.7-1.

[0015] As a preferred embodiment of the present invention, the high-strength cement-based composition...

[0016] The mass ratio of plastic expander to calcium oxide-sulfoaluminate expander is 1:10-15.

[0017] In a preferred embodiment of the present invention, the water-reducing agent in the high-strength cement-based composition has a water reduction rate of 15-20%.

[0018] Magnesium oxide expansive agents include medium-speed and slow-speed types, with a mass ratio of 1:2 to 1:4. Medium-speed magnesium oxide exhibits higher reactivity than slow-speed magnesium oxide. For details on medium-speed and slow-speed types, please refer to standard CBMF 19-2017 (Magnesium Oxide Expansive Agents for Concrete).

[0019] In a preferred embodiment of the present invention, the reaction time of the high-strength cement-based composition for medium-speed magnesium oxide is 100-200 s;

[0020] The reaction time for slow-type magnesium oxide is 200-300 seconds.

[0021] As a preferred embodiment of the present invention, the high-strength cement-based composition comprises graded aggregates including No. 1 quartz sand, No. 2 quartz sand, No. 3 quartz sand and No. 4 quartz sand, with a mass ratio of No. 1 quartz sand: No. 2 quartz sand: No. 3 quartz sand and No. 4 quartz sand of 25-30: 2-5: 15-20: 3-6.

[0022] Among them, in No. 1 quartz sand, particles with a diameter < 0.73mm accounted for 10%, particles with a diameter < 1.27mm accounted for 50%, and particles with a diameter < 2.14mm accounted for 90%.

[0023] In No. 2 quartz sand, particles with a diameter < 0.45 mm account for 10%, particles with a diameter < 0.74 mm account for 50%, and particles with a diameter < 1.10 mm account for 90%.

[0024] In No. 3 quartz sand, particles with a diameter < 0.18 mm account for 10%, particles with a diameter < 0.33 mm account for 50%, and particles with a diameter < 0.51 mm account for 90%.

[0025] In No. 4 quartz sand, particles with a diameter < 0.11 mm account for 10%, particles with a diameter < 0.17 mm account for 50%, and particles with a diameter < 0.26 mm account for 90%.

[0026] Secondly, embodiments of the present invention provide a high-strength cement-based grouting material, which is prepared by mixing the high-strength cement-based composition with water, wherein water accounts for 9-10% of the mass of the high-strength cement-based composition.

[0027] Thirdly, embodiments of the present invention provide a method for preparing a high-strength cement-based grouting material, comprising the following steps:

[0028] S1. Mix the water-reducing agent, defoamer and composite expansion agent with 5-10%wt of silicate cement to prepare the first premix.

[0029] S2. Mix the first premix with the graded aggregate and the remaining cementitious base material to obtain the second premix;

[0030] S3. Add the second premix to water, mix well, let stand to defoam, and prepare high-strength cement-based grout.

[0031] In a preferred embodiment of the present invention, in the preparation method described, the mixing time in both S1 and S2 is 5-8 min.

[0032] In S3, the mixing time is 3-5 minutes, and the mixture is allowed to stand for 1-2 minutes to defoam.

[0033] Fourthly, the embodiments of the present invention provide the application of the high-strength cement-based composition, or the high-strength cement-based grout, or the high-strength cement-based grout prepared by the preparation method in the casting of modular buildings, equipment foundation fixing, and concrete reinforcement.

[0034] (III) Beneficial Effects

[0035] The beneficial effects of this invention are as follows: This invention provides a high-strength cement-based composition, grouting material, its preparation method, and its application. The high-strength cement-based composition, by employing graded aggregates, silica fume, nano-silica-modified ultrafine mineral powder, and fly ash microspheres, forms a composite filling of graded aggregates and ultrafine powders, achieving close packing and improving the density of concrete materials. This provides a foundation for high strength and reduced shrinkage. Cement, silica fume, nano-silica-modified ultrafine mineral powder, and fly ash microspheres form a multi-component cementitious system. During the hydration stage, silica fume rapidly reacts with Ca(OH)₂ to generate CSH, refining pores and significantly improving early strength. Nano-silica-modified ultrafine mineral powder can be uniformly dispersed within the system and continues to hydrate in the later stages, compensating for strength growth. Fly ash microspheres initially improve the workability of the grout and participate in the reaction in the middle and later stages. Silica fume, nano-silica-modified ultrafine mineral powder, and fly ash microspheres form a multi-scale, multi-stage hydration network with cement, resulting in more uniform and dense hydration products, improving strength, crack resistance, and durability.

[0036] In addition, water-reducing agents can disperse cement and ultrafine powder particles, release encapsulated water, and maintain self-leveling properties even with extremely low water content (such as a water-to-material ratio of 9-10%). The low water-to-cement ratio is beneficial for improving early strength and reducing shrinkage.

[0037] Defoamers suppress air bubbles, further improving density and appearance quality. Expansive agents achieve full-cycle volume stability of concrete materials, making them suitable for modular construction and ensuring that the grouting layer remains tightly bonded to reinforcing bars, steel plates, and the concrete matrix.

[0038] The composite expansion agents are used in combination. The plastic expansion agent expands by generating gas before initial setting, compensating for plastic settlement shrinkage and ensuring that the vertical expansion rate meets the standard (e.g., ≥0.02%) within 24 hours. The calcium oxide-sulfoaluminate expansion agent generates ettringite / Ca(OH)2 1-28 days after hardening, compensating for autogenous shrinkage and drying shrinkage. The magnesium oxide expansion agent delays expansion, making the drying shrinkage rate close to zero or even causing micro-expansion after 90 days. The three expansion agents complement each other, covering the entire life cycle from the plastic stage to long-term service. It prevents early cracking (such as debonding of joints), has a low total shrinkage rate, and ensures that the grouting layer is always tightly bonded to the reinforcing steel, steel plate, and concrete matrix, which is beneficial to improving the integrity and durability of joints and structural reinforcement in modular buildings.

[0039] Compared to existing technologies, this grout can meet the requirements for micro-expansion in the early stage (24h) and has good long-term volume stability, which is beneficial to improving the integrity and durability of the joints and structural reinforcement of modular buildings. The compressive strength of this invention reaches 105-115MPa at 28 days, ≥52MPa at 1 day, and the drying shrinkage rate is close to zero or even slightly expanded at 90 days (while the existing A85 grade grout has an upper limit of 85MPa at 28 days, ≥35MPa at 1 day, and a high long-term shrinkage rate). It has high early strength and compressive strength grades. This grout takes into account both compressive strength and interfacial bonding effect, and can meet the requirements of rapid construction and mechanical performance of modular buildings.

[0040] When plastic expansion agent and calcium oxide-sulfoaluminate expansion agent are used in combination at a mass ratio of 1:10-15, the early vertical expansion rate and total shrinkage rate of the grout can reach the optimal balance.

[0041] The defoamer is a combination of polyether defoamer and polysiloxane defoamer, with a mass ratio of 1:0.7-1, which can effectively defoam and improve the density of the material.

[0042] Magnesium oxide expansive agents include medium-speed and slow-speed magnesium oxide, with a mass ratio of 1:2 to 1:4. Medium-speed magnesium oxide exhibits higher reactivity than slow-speed magnesium oxide. Medium-speed magnesium oxide is fired at 850℃-950℃, with a reaction time of 100-200 seconds; slow-speed magnesium oxide is fired at 950℃-1050℃, with a reaction time of 200-300 seconds. Medium-speed magnesium oxide begins to react significantly from day 7 to 28 after pouring, compensating for early autogenous shrinkage and initial drying shrinkage of concrete, preventing early microcracks. Slow-speed magnesium oxide acts from day 28 to 180 after pouring, responsible for long-term volume stability, compensating for drying shrinkage, temperature shrinkage, and creep during long-term service, ensuring that modular building joints maintain a slightly expanded state and do not debond even after several years. Detailed Implementation

[0043] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below through specific embodiments.

[0044] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0045] Example 1

[0046] This embodiment provides a method for preparing a high-strength cement-based grouting material, including the following steps:

[0047] (1) Preparation of high-strength cement-based composition:

[0048] Prepare 51 parts of graded quartz sand by weight fraction (1#: 2#: 3#: 4# = 27: 3: 16: 5).

[0049] Next, prepare the cementitious base material, according to the following weight fractions: 35 parts silicate cement, 3 parts silica fume, 9 parts nano-silica modified ultrafine mineral powder, and 2 parts fly ash microspheres.

[0050] Prepare a water-reducing agent at 0.6% of the aforementioned cementitious base material mass; BASF's polycarboxylate water-reducing agent has a water reduction rate of 15%.

[0051] Prepare defoamer at 0.7% of the aforementioned cementitious base material mass, with the mass ratio of polyether defoamer to polysiloxane defoamer being 1:0.75; among which, the polyether defoamer is selected from the BASF brand, and the polysiloxane defoamer is selected from the German Mingling brand.

[0052] Prepare plastic expansion agent and calcium oxide-sulfoaluminate expansion agent at 0.33% of the mass of the aforementioned cementitious base material, with a mass ratio of plastic expansion agent to calcium oxide-sulfoaluminate expansion agent of 1:10; among them, the plastic expansion agent is HEA-GY3 expansion agent from Puxin Building Materials, and the calcium oxide-sulfoaluminate expansion agent is HP-CSA expansion agent from DENKA.

[0053] Prepare magnesium oxide expansion agent at 4% of the aforementioned cementitious base material mass, wherein the mass ratio of fast-acting magnesium oxide to slow-acting magnesium oxide is 1:2;

[0054] The main function of plastic expansion agents is to cause the grout, which is still in a plastic state after mixing, to expand. The mechanism is that the plastic expansion agent reacts under alkaline conditions to generate nitrogen gas, which causes the grout volume to expand. Calcium oxide-sulfoaluminate expansion agents mainly play a role after the grout has initially set, compensating for the autogenous shrinkage and drying shrinkage of the grout. Among magnesium oxide expansion agents, the medium-speed magnesium oxide and slow-speed magnesium oxide play an expansion role sequentially after the calcium oxide-sulfoaluminate expansion agent.

[0055] Among them, the nano-silica modified ultrafine mineral powder is grade S140 as specified in GB / T 18046-2017 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete", with a specific surface area ≥500m². 2 / kg, 7d activity index ≥100%, 28d activity index ≥140%.

[0056] Specifically, the preparation process of nano-silica modified ultrafine mineral powder is as follows:

[0057] Raw material preparation: ① Ultrafine mineral powder (S95 grade or higher), dried to constant weight at 105℃ before use to remove adsorbed water and ensure exposure of surface active sites. ② Nano-SiO2, purity ≥ 99.5%, average particle size 10-20nm, specific surface area ≥ 200m². 2 / g. Nano-silica accounts for 5% of the mass of ultrafine mineral powder. ③ Powdered polycarboxylic acid superdispersant (dry powder, such as TegoDispers series), the amount of dispersant is 0.05%-0.1% of the mass of mineral powder, to prevent excessive agglomeration of nanoparticles during ball milling and to assist chemical bonding.

[0058] Preparation steps: Place the dried ultrafine mineral powder, nano-SiO2 powder, and grinding aid (dispersant) into a dry container and stir at a low speed of 200-300 rpm for 10-15 minutes to allow the nano-SiO2 to initially adhere to the surface of the mineral powder particles, thus obtaining a premixed powder. This avoids the nano-powder from flying or having excessively high local concentrations when directly fed into the mill. Load the premixed powder into the grinding jar of a planetary ball mill, add zirconia grinding beads, and maintain a planetary speed of 300-400 rpm and a rotation speed of 600-800 rpm. The ball-to-powder mass ratio is 10:1-15:1. Grind for 45-90 minutes, strictly controlling the temperature inside the jar to not exceed 60℃ during this period. After grinding, remove the powder and sieve it using a high-frequency vibrating screen (45μm aperture). Place the prepared nano-silica modified ultrafine mineral powder into a sealed bag or moisture-proof container and let it stand for 12-24 hours for later use.

[0059] Under the impact and shearing action of high-energy ball milling, nano-SiO2 not only adheres to the surface of mineral powder, but some nanoparticles also embed themselves in the microcracks and pores on the surface of the mineral powder. This mechanically interlocked structure is more robust than simple surface adsorption and is less likely to detach during subsequent water addition and stirring. By employing a completely dry mechanochemical process, the microscopic impact of the grinding balls is used to forcibly break open the nano-agglomerates, achieving monodisperse or low-agglomeration loading of nano-SiO2 on the surface of mineral powder.

[0060] In addition, the specific graded quartz sand is shown in Table 1:

[0061] Table 1

[0062]

[0063] (2) The water-reducing agent, defoamer and composite expansion agent in the composition prepared in (1) are premixed with a portion of silicate cement (10% of the total weight of silicate cement) using a small mixer for 5 minutes to obtain the first premix, so as to ensure that the water-reducing agent, defoamer and expansion agent can be evenly dispersed in the subsequent mixing.

[0064] (3) The graded quartz sand and the remaining cementitious base material are put into a large mixer and mixed with the first premix in (2) for 5 minutes to ensure uniform mixing and to obtain the second premix. The second premix is ​​bagged and packaged to obtain high-strength cement-based grouting dry mix.

[0065] (4) Weigh and add water to the mixing container according to the mass ratio of dry mix to water of 10%, then add dry mix, stir with a mixer for 5 minutes, and let stand for 2 minutes to defoam after stirring evenly. The mixing process is then completed to obtain high-strength cement-based grout.

[0066] It should be noted that, if the production batch is 0.5 tons, the weighing of quartz sand, silicate cement, silica fume, nano-silica modified ultrafine mineral powder and fly ash microspheres in the high-strength cement-based composition is accurate to 0.01 kg, and the weighing of high-efficiency water-reducing agent, defoamer and composite expansion agent is accurate to 1 gram.

[0067] The cement-based grout prepared in this embodiment is applied to the casting of modular buildings.

[0068] Meanwhile, in accordance with the national standard GB / T 50448-2015 and the building materials industry standard JC / T 986-2018, the truncated cone flowability, flowability after 30 minutes, vertical expansion rate after 3 hours, compressive strength at 1 day, 3 days, and 28 days, and total shrinkage rate from 1 day (excluding the 24-hour expansion rate), 28 days, and 56 days were tested on the high-strength cement-based grout in Example 1. The test results are detailed in Table 2.

[0069] Example 2

[0070] This embodiment provides a method for preparing a high-strength cement-based grout, which differs from Embodiment 1 in that:

[0071] (1) Preparation of high-strength cement-based composition:

[0072] Prepare 51 parts of graded quartz sand by weight fraction (1#: 2#: 3#: 4# = 25: 5: 20: 6).

[0073] Next, prepare the cementitious base material, according to the following weight fractions: 30 parts silicate cement, 6 parts silica fume, 5 parts nano-silica modified ultrafine mineral powder, and 6 parts fly ash microspheres.

[0074] Prepare a water-reducing agent at 1.0% of the aforementioned cementitious base material mass; BASF's polycarboxylate water-reducing agent has a water reduction rate of 15%.

[0075] Prepare defoamer at 0.6% of the aforementioned cementitious base material mass, with the mass ratio of polyether defoamer to polysiloxane defoamer in the defoamer being 1:1;

[0076] Prepare plastic expansion agent and calcium oxide-sulfoaluminate expansion agent at 0.6% of the aforementioned cementitious base material mass, with the mass ratio of plastic expansion agent to calcium oxide-sulfoaluminate expansion agent being 1:15;

[0077] Prepare magnesium oxide expansion agent according to 8% of the mass of the aforementioned cementitious base material, wherein the mass ratio of fast-acting magnesium oxide to slow-acting magnesium oxide is 1:4; (2) Premix the water-reducing agent, defoamer and composite expansion agent in the composition prepared in (1) with a portion of silicate cement (10% of the total weight of silicate cement) using a small mixer for 8 minutes to obtain the first premixed material, so as to ensure that the water-reducing agent, defoamer and expansion agent can be evenly dispersed in the subsequent mixing;

[0078] (4) Weigh and add water to the mixing container according to the mass ratio of dry mix to water of 10%, then add dry mix, stir with a mixer for 3 minutes, and let stand for 1 minute after stirring evenly to defoam. The mixing process is then completed to obtain high-strength cement-based grout.

[0079] The remaining steps are the same.

[0080] The cement-based grout prepared in this embodiment is applied to the casting of modular buildings.

[0081] Meanwhile, in accordance with the national standard GB / T 50448-2015 and the building materials industry standard JC / T 986-2018, the flowability of the high-strength cement-based grout in Example 2 was tested, including the truncated cone flowability, flowability after 30 minutes, vertical expansion rate after 3 hours, compressive strength at 1 day, 3 days, and 28 days, and total shrinkage rate starting from 1 day (excluding the 24-hour expansion rate), 28 days, and 56 days. The test results are detailed in Table 2.

[0082] Example 3

[0083] This embodiment provides a method for preparing a high-strength cement-based grout, which differs from Embodiment 2 in that:

[0084] (1) Preparation of high-strength cement-based composition:

[0085] Prepare 47 portions of graded quartz sand by weight fraction (1#: 2#: 3#: 4# = 25: 5: 20: 6).

[0086] Prepare 33 parts silicate cement, 2 parts silica fume, 10 parts nano-silica modified ultrafine mineral powder, and 4 parts fly ash microspheres by weight fraction.

[0087] Prepare a water-reducing agent at 0.8% of the aforementioned cementitious base material mass; BASF's polycarboxylate water-reducing agent has a water reduction rate of 15%.

[0088] Prepare defoamer at 0.6% of the aforementioned cementitious base material mass, with the mass ratio of polyether defoamer to polysiloxane defoamer in the defoamer being 1:0.8;

[0089] Prepare plastic expansion agent and calcium oxide-sulfoaluminate expansion agent at 0.8% of the aforementioned cementitious base material mass, with a mass ratio of plastic expansion agent to calcium oxide-sulfoaluminate expansion agent of 1:12.

[0090] Prepare magnesium oxide expanding agent at 6% of the aforementioned cementitious base material mass, wherein the mass ratio of fast-acting magnesium oxide to slow-acting magnesium oxide is 1:3; the remaining steps are the same.

[0091] The cement-based grout prepared in this embodiment is applied to the casting of modular buildings.

[0092] Meanwhile, in accordance with the national standard GB / T 50448-2015 and the building materials industry standard JC / T 986-2018, the flowability of the high-strength cement-based grout in Example 3 was tested, including the truncated cone flowability, flowability after 30 minutes, vertical expansion rate after 3 hours, compressive strength at 1 day, 3 days, and 28 days, and total shrinkage rate starting from 1 day (excluding the 24-hour expansion rate), 28 days, and 56 days. The test results are detailed in Table 2.

[0093] Table 2

[0094]

[0095] Comparative Example 1

[0096] This comparative example provides a method for preparing a cement-based grout. The difference between this comparative example and Example 1 is that:

[0097] In step (1), no magnesium oxide expanding agent was added.

[0098] The remaining steps and conditions are the same as in Example 1.

[0099] The cement-based grout prepared in this comparative example was applied to the casting of modular buildings.

[0100] Meanwhile, in accordance with the national standard GB / T 50448-2015 and the building materials industry standard JC / T 986-2018, the flowability of the cement-based grout in Comparative Example 1 was tested, including the truncated cone flowability, flowability after 30 minutes, vertical expansion rate after 3 hours, compressive strength at 1 day, 3 days, and 28 days, and total shrinkage rate starting from 1 day (excluding the 24-hour expansion rate), 28 days, and 56 days. The test results are detailed in Table 3.

[0101] Comparative Example 2

[0102] This comparative example provides a method for preparing a cement-based grout. The difference between this comparative example and Example 1 is that:

[0103] In step (1), the mass ratio of medium-speed magnesium oxide to slow-speed magnesium oxide is 1:1. The remaining steps and conditions are the same as in Example 1.

[0104] The cement-based grout prepared in this comparative example was applied to the casting of modular buildings.

[0105] Meanwhile, in accordance with the national standard GB / T 50448-2015 and the building materials industry standard JC / T 986-2018, the flowability of the cement-based grout in Comparative Example 2 was tested, including the truncated cone flowability, flowability after 30 minutes, vertical expansion rate after 3 hours, compressive strength at 1 day, 3 days, and 28 days, and total shrinkage rate starting from 1 day (excluding the 24-hour expansion rate), 28 days, and 56 days. The test results are detailed in Table 3.

[0106] Comparative Example 3

[0107] This comparative example provides a method for preparing a cement-based grout. The difference between this comparative example and Example 1 is that:

[0108] In step (1), the nano-silica modified ultrafine mineral powder is replaced with ultrafine mineral powder. The remaining steps and conditions are the same as in Example 1.

[0109] Meanwhile, in accordance with the national standard GB / T 50448-2015 and the building materials industry standard JC / T 986-2018, the flowability of the cement-based grout in Comparative Example 3 was tested, including the truncated cone flowability, flowability after 30 minutes, vertical expansion rate after 3 hours, compressive strength at 1 day, 3 days, and 28 days, and total shrinkage rate starting from 1 day (excluding the 24-hour expansion rate), 28 days, and 56 days. The test results are detailed in Table 3.

[0110] Comparative Example 4

[0111] This comparative example provides a method for preparing a cement-based grout. The difference between this comparative example and Example 1 is that:

[0112] In step (1), the mass ratio of polyether defoamer to polysiloxane defoamer in the defoamer is 1:1.35. The remaining steps and conditions are the same as in Example 1.

[0113] The cement-based grouting materials prepared in Comparative Examples 1-4 were applied to the casting of modular buildings.

[0114] Meanwhile, in accordance with the national standard GB / T 50448-2015 and the building materials industry standard JC / T 986-2018, the flowability of the cement-based grouting materials in Comparative Examples 1-4 was tested, including the truncated cone flowability, flowability after 30 minutes, vertical expansion rate after 3 hours, compressive strength at 1 day, 3 days, and 28 days, and total shrinkage rate starting from 1 day (excluding the 24-hour expansion rate), 28 days, and 56 days. The test results are detailed in Table 3.

[0115] Table 3

[0116]

[0117] The comparative analysis of the above comparative examples and embodiments shows that:

[0118] Example 3, as the preferred embodiment, exhibits excellent strength at 1 day and optimal compressive strength at 28 days. Simultaneously, the vertical expansion rates at 3 hours and 24 hours meet requirements, and the shrinkage rate after 28 days is the lowest, even showing slight expansion, which is beneficial for improving interfacial bonding strength. The fluidity of the grout meets the casting requirements for modular buildings.

[0119] The high-strength cement-based grouts prepared in Examples 1 to 3 meet the early load-bearing capacity requirements of rapid assembly in modular buildings. Furthermore, their 28-day strength limit is sufficient to support the long-term safety of high-load or critical stress nodes. Simultaneously, their low long-term shrinkage rate prevents cracking or interface debonding, thereby enhancing the integrity and durability of modular building nodes.

[0120] Comparing Comparative Example 1 with Example 1, it can be seen that removing magnesium oxide expansion agent from the composite expansion agent will cause a significant increase in the shrinkage rate of the grout in the later stage (28 days, 56 days, 90 days), which will cause cracking or interface debonding.

[0121] Comparing Comparative Example 2 with Example 1, it can be seen that when the mass ratio of medium-speed magnesium oxide to slow-speed magnesium oxide in the magnesium oxide expanding agent is too large, i.e., when the dosage of medium-speed magnesium oxide is large, it will cause a significant increase in the shrinkage rate of the grout in the later stage. Therefore, the mass ratio of medium-speed magnesium oxide to slow-speed magnesium oxide should be between 1:2 and 1:4 to ensure a low shrinkage rate of the grout in the later stage.

[0122] Comparing Comparative Example 3 with Example 1, it can be seen that nano-silica modified ultrafine mineral powder can improve compressive strength.

[0123] Comparing Comparative Example 4 with Example 1, it can be seen that when the mass ratio of polyether defoamer to polysiloxane defoamer in the defoamer is too low, both the flowability and compressive strength are reduced.

[0124] In defoaming agents, polyether defoamers and polysiloxane defoamers are used in combination at a mass ratio of 1:0.7-1, which can meet both the requirements for slurry fluidity and compressive strength.

[0125] The high-strength cement-based grouting material of this invention uses three expansion agents in combination to ensure that the vertical expansion rate meets the standard requirements in the early stage (24 hours) and effectively compensates for the volume shrinkage of the grouting material in the later stage. At the same time, by increasing the density of the internal material packing of the grouting material through graded aggregates and defoamers, shrinkage can also be reduced to a certain extent, thus achieving long-term volume stability of the grouting material and ensuring the integrity and durability of modular building joints and structural reinforcement.

[0126] Furthermore, the blending of different cementitious materials in the high-strength cement-based grout allows cement and auxiliary cementitious materials to mutually promote hydration, thereby improving early strength and compressive strength. Simultaneously, nano-silica-modified ultrafine mineral powder and other components in the cementitious materials also contribute to dense filling, further refining the voids and increasing the material's density. This high-strength cement-based grout is suitable for casting modular buildings.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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 still 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; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-strength cement-based composition, characterized in that, This includes cementitious base materials, water-reducing agents, defoamers, composite expansion agents, and graded aggregates; The cementitious base material includes, by weight: 30-35 parts silicate cement, 2-6 parts silica fume, 5-10 parts nano-silica modified ultrafine mineral powder, and 2-6 parts fly ash microspheres. By weight, the graded aggregate is 47-52 parts; The mass ratio of water-reducing agent to cementitious base material is 0.5-1.0%, and the mass ratio of defoamer to cementitious base material is 0.6-0.8%. The composite expanding agent includes plastic expanding agent, calcium oxide-sulfoaluminate expanding agent and magnesium oxide expanding agent; among which, the sum of the mass of plastic expanding agent and calcium oxide-sulfoaluminate expanding agent accounts for 0.3-0.6% of the mass of cementitious base material, and magnesium oxide expanding agent accounts for 4-8% of the mass of cementitious base material.

2. The high-strength cement-based composition as described in claim 1, characterized in that, Defoamers include polyether defoamers and polysiloxane defoamers, wherein the mass ratio of polyether defoamers to polysiloxane defoamers is 1:0.7-1.

3. The high-strength cement-based composition as described in claim 2, characterized in that, The mass ratio of plastic expander to calcium oxide-sulfoaluminate expander is 1:10-15.

4. The high-strength cement-based composition according to any one of claims 1 to 3, characterized in that, The water reduction rate of water-reducing agents is 15-20%; Magnesium oxide expanding agents include medium-speed magnesium oxide and slow-speed magnesium oxide, with a mass ratio of medium-speed magnesium oxide to slow-speed magnesium oxide of 1:2-1:

4. Among them, the reactivity of medium-speed magnesium oxide is higher than that of slow-speed magnesium oxide.

5. The high-strength cement-based composition as described in claim 4, characterized in that, The reaction time for medium-speed magnesium oxide is 100-200 seconds; The reaction time for slow-type magnesium oxide is 200-300 seconds.

6. The high-strength cement-based composition according to any one of claims 1 to 3, characterized in that, The graded aggregate includes No. 1 quartz sand, No. 2 quartz sand, No. 3 quartz sand and No. 4 quartz sand, and the mass ratio of No. 1 quartz sand, No. 2 quartz sand, No. 3 quartz sand and No. 4 quartz sand is 25-30: 2-5: 15-20: 3-6; Among them, in No. 1 quartz sand, particles with a diameter < 0.73mm accounted for 10%, particles with a diameter < 1.27mm accounted for 50%, and particles with a diameter < 2.14mm accounted for 90%. In No. 2 quartz sand, particles with a diameter < 0.45 mm account for 10%, particles with a diameter < 0.74 mm account for 50%, and particles with a diameter < 1.10 mm account for 90%. In No. 3 quartz sand, particles with a diameter < 0.18 mm account for 10%, particles with a diameter < 0.33 mm account for 50%, and particles with a diameter < 0.51 mm account for 90%. In No. 4 quartz sand, particles with a diameter < 0.11 mm account for 10%, particles with a diameter < 0.17 mm account for 50%, and particles with a diameter < 0.26 mm account for 90%.

7. A high-strength cement-based grouting material, characterized in that, The high-strength cement-based composition according to any one of claims 1 to 6 is prepared by mixing with water, wherein water accounts for 9-10% of the mass of the high-strength cement-based composition.

8. A method for preparing the high-strength cement-based grouting material according to claim 7, characterized in that, Includes the following steps: S1. Mix the water-reducing agent, defoamer and composite expansion agent with 5-10%wt of silicate cement to prepare the first premix. S2. Mix the first premix with the graded aggregate and the remaining cementitious base material to obtain the second premix; S3. Add the second premix to water, mix well, let stand to defoam, and prepare high-strength cement-based grout.

9. The preparation method according to claim 8, characterized in that, In S1 and S2, the mixing time is 5-8 min; In S3, the mixing time is 3-5 minutes, and the mixture is allowed to stand for 1-2 minutes to defoam.

10. The high-strength cement-based composition according to any one of claims 1 to 6, or the high-strength cement-based grout according to claim 7, or the application of the high-strength cement-based grout prepared by the preparation method according to any one of claims 8 to 9 in the casting of modular buildings, equipment foundation fixing, and concrete reinforcement.

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