Low-shrinkage stabilized concrete and method for producing the same

Abstract

The application discloses low-shrinkage stable concrete and a preparation method thereof, and belongs to the technical field of building materials. The low-shrinkage stable concrete is prepared from the following components in parts by weight: cement 200-400 parts, modified aggregate 600-1000 parts, fly ash 28-35 parts, water reducing agent 3-9 parts, composite expansive agent 90-100 parts, modified adhesive material 15-25 parts and water 160-180 parts. The composite expansive agent is a compound of a calcium source expansive agent and a magnesium source expansive agent, and the mass ratio of the calcium source expansive agent to the magnesium source expansive agent is (25-35):(65-75). The calcium source expansive agent and the magnesium source expansive agent are compounded in a specific ratio, so that the shrinkage demand of the concrete under various working conditions in the whole life cycle can be compensated.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and more specifically, to a low-shrinkage stabilized concrete and its preparation method. Background Technology

[0002] Concrete, a widely used material in construction, directly impacts the safety and service life of structures due to its performance. During the hydration and hardening process of concrete, shrinkage occurs due to water evaporation and changes in the volume of cement paste. When the stress generated by this shrinkage exceeds the tensile strength of the concrete, cracks form. The appearance of cracks disrupts the continuity of the concrete, reduces its strength and density, and affects the structural performance and durability.

[0003] Controlling concrete cracking and reducing shrinkage are key. A common method to reduce concrete shrinkage is to add a certain amount of expansive agent during the concrete mixing process. The expansion stress generated by the expansive agent during hydration counteracts the shrinkage strain of the concrete, thus compensating for the shrinkage. Currently, commonly used expansive agents are mainly calcium-based and magnesium-based. Calcium-based expansive agents have a fast early reaction rate and virtually no expansion in the later stages; magnesium-based expansive agents have a relatively slower hydration rate, relatively small early expansion, but continuous expansion in the presence of water molecules in the later stages, and exhibit lower activity at room temperature and higher activity at high temperatures. However, concrete shrinkage continues throughout its lifespan, and the degree of shrinkage varies under different working conditions. A single type of expansive agent cannot compensate for the shrinkage requirements of concrete under all working conditions throughout its entire life cycle. For example, calcium-based expansive agents mainly function during the early plastic shrinkage and some autogenous shrinkage stages of concrete, while their effect on other shrinkage stages such as temperature drop shrinkage and drying shrinkage is limited. Although magnesium-based expansive agents have the ability to expand continuously in the later stages, their early expansion energy is relatively small, and their expansion energy is insufficient under low-temperature conditions. Therefore, it is particularly important to develop a product that can compensate for the different degrees of shrinkage of concrete at different ages and under different working conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a low-shrinkage stable concrete and its preparation method, thereby addressing the problems in the prior art.

[0005] A low-shrinkage stabilized concrete is composed of the following components in parts by weight: 200-400 parts cement, 600-1000 parts modified aggregate, 28-35 parts fly ash, 3-9 parts water-reducing agent, 90-100 parts composite expansive agent, 15-25 parts modified adhesive, and 160-180 parts water; wherein the composite expansive agent is a mixture of calcium-based and magnesium-based expansive agents, and the mass ratio of the calcium-based to magnesium-based expansive agents is (25-35):(65-75).

[0006] Preferably, the calcium source expanding agent is a compound of calcium oxide and calcium sulfoaluminate, and the magnesium source expanding agent is a compound of magnesium oxide and magnesium chloride.

[0007] Preferably, the mass ratio of calcium oxide to calcium sulfoaluminate is 1:(1-3); and the mass ratio of magnesium oxide to magnesium chloride is 1:(2-4).

[0008] Preferably, the modified aggregate is obtained by pre-treating aggregate and then modifying it.

[0009] Preferably, the aggregate is one or more of stone, mortar, ceramic waste, waste slag and coal gangue, sea stone and sea sand, mixed with construction waste concrete.

[0010] Preferably, the pretreatment is as follows: the aggregate is pre-crushed, and the uncrushable debris is sorted out, and waste wood and plastic are removed. At the same time, a primary magnetic separation is performed to remove waste iron from the aggregate. After screening, recycled aggregate with an average particle size of 10mm to 20mm is obtained.

[0011] Preferably, the modification treatment is as follows: the recycled aggregate is soaked in a sodium silicate solution and stirred at a stirring speed of 100 r / min to 120 r / min for 3 h to 5 h, and then soaked in a glacial acetic acid solution and stirred at a stirring speed of 50 r / min to 80 r / min for 20 min to 35 min to obtain the modified aggregate.

[0012] Preferably, the modified adhesive is composed of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide, and the mass ratio of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide is (7-9):(6-8):(5-7):(4-6):(5-6):(1-2).

[0013] Preferably, the cement is at least one of silicate cement, sulfoaluminate cement, and aluminate cement; and the water-reducing agent is a polycarboxylate water-reducing agent.

[0014] The present invention also provides a method for preparing low-shrinkage stabilized concrete, the method comprising the following steps:

[0015] S1. Add cement, modified aggregate, fly ash and composite expansion agent to a mixer and mix at a speed of 50r / min~100r / min for 5min~10min to obtain dry mix;

[0016] S2. Add water, water-reducing agent, and modified adhesive to the dry mix, and continue mixing for 20 to 60 minutes to obtain concrete mixture;

[0017] S3. The concrete mixture is placed in the mold and cured until the specified age is reached to obtain low-shrinkage stable concrete.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention combines calcium-based and magnesium-based expansion agents in a specific ratio to compensate for the shrinkage requirements of concrete under various working conditions throughout its entire life cycle.

[0020] The modified aggregates and modified cementitious materials used in this invention produce a synergistic effect, enabling inorganic solid waste to be transformed into recycled building materials after its end state is changed and reused. This comprehensively promotes the porosity of concrete, increasing density and impermeability while also enhancing compressive strength and stability. The modified aggregates are selected from one or more of stone, mortar, ceramic waste, waste slag, coal gangue, marine stone, and sea sand, mixed with construction waste concrete. The solid components have a certain active effect, allowing for a suitable reduction in aggregate usage during concrete preparation, achieving high-value utilization of aggregates, thereby reducing the amount of modified cementitious materials needed and helping to reduce shrinkage. The compounded expansive agent provides more comprehensive shrinkage compensation from the plastic stage of concrete to the long-term service stage, effectively reducing porosity and micro-cracks, increasing concrete density, and thus synergistically improving impermeability. Detailed Implementation

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0022] An embodiment of the present invention provides a low-shrinkage stabilized concrete, which is composed of the following components in parts by weight: 200-400 parts cement, 600-1000 parts modified aggregate, 28-35 parts fly ash, 3-9 parts water-reducing agent, 90-100 parts composite expansive agent, 15-25 parts modified adhesive, and 160-180 parts water; the composite expansive agent is a mixture of calcium-based expansive agent and magnesium-based expansive agent, and the mass ratio of the calcium-based expansive agent to the magnesium-based expansive agent is (25-35):(65-75).

[0023] In one embodiment, the calcium source expanding agent is a compound of calcium oxide and calcium sulfoaluminate, and the magnesium source expanding agent is a compound of magnesium oxide and magnesium chloride.

[0024] In one embodiment, the mass ratio of calcium oxide to calcium sulfoaluminate is 1:(1-3); the mass ratio of magnesium oxide to magnesium chloride is 1:(2-4).

[0025] This invention utilizes a combination of calcium-based and magnesium-based expanding agents to effectively compensate for shrinkage, prevent cracking, and enhance impermeability and durability. It can compensate for the shrinkage requirements of concrete under various working conditions throughout its entire life cycle. The calcium-based expanding agent, a combination of calcium oxide and calcium sulfoaluminate, and the magnesium-based expanding agent, a combination of magnesium oxide and magnesium chloride, can improve the activity of the expanding clinker, resulting in a more uniform hydration reaction and more stable expansion performance, thereby enhancing the low-shrinkage stability of concrete.

[0026] In one embodiment, the modified aggregate is obtained by pre-treating aggregate and then modifying it.

[0027] In one embodiment, the aggregate is one or more of stone, mortar, ceramic waste, waste slag and coal gangue, sea stone and sea sand, mixed with construction waste concrete.

[0028] In one embodiment, the pretreatment is as follows: the aggregate is pre-crushed, and the uncrushable debris is sorted out, waste wood and plastic are removed, and at the same time, a primary magnetic separation is performed to remove waste iron from the aggregate. After screening, recycled aggregate with an average particle size of 10mm to 20mm is obtained.

[0029] In one embodiment, the modification process is as follows: the recycled aggregate is soaked in a sodium silicate solution and stirred at a stirring speed of 100 r / min to 120 r / min for 3 h to 5 h, and then soaked in a glacial acetic acid solution and stirred at a stirring speed of 50 r / min to 80 r / min for 20 min to 35 min to obtain the modified aggregate.

[0030] This invention modifies aggregates twice, which helps to increase the porosity of aggregates, reduce the absorption rate and crushing value, thereby increasing their load-bearing capacity in concrete structures and improving their compressive strength.

[0031] In one embodiment, the modified adhesive is composed of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide, wherein the mass ratio of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide is (7-9):(6-8):(5-7):(4-6):(5-6):(1-2).

[0032] The modified adhesive of this invention, when used in combination with modified aggregates, has a positive modifying effect on concrete, significantly increasing the compressive strength, toughness, impermeability, durability, corrosion resistance, and thermal insulation of concrete, thereby increasing the usability of low-shrinkage stable concrete, helping to reduce shrinkage rate, and greatly improving the overall performance of concrete.

[0033] In one embodiment, the cement is at least one of silicate cement, sulfoaluminate cement, and aluminate cement; the water-reducing agent is a polycarboxylate water-reducing agent.

[0034] In addition, the present invention also provides a method for preparing low-shrinkage stabilized concrete, the method comprising the following steps:

[0035] S1. Add cement, modified aggregate, fly ash and composite expansion agent to a mixer and mix at a speed of 50r / min~100r / min for 5min~10min to obtain dry mix;

[0036] S2. Add water, water-reducing agent, and modified adhesive to the dry mix, and continue mixing for 20 to 60 minutes to obtain concrete mixture;

[0037] S3. The concrete mixture is placed in the mold and cured until the specified age is reached to obtain low-shrinkage stable concrete.

[0038] The above scheme optimizes the composition and proportions of concrete, resulting in concrete with excellent strength and low shrinkage, thus having higher application value.

[0039] The implementation scheme of the present invention will be described in detail below with reference to specific embodiments. The raw materials, reagents, etc. used in the embodiments that are not described in detail are all commercially available.

[0040] Example 1:

[0041] A low-shrinkage stabilized concrete is composed of the following components in parts by weight: 200 parts of sulfoaluminate cement, 1000 parts of modified aggregate, 28 parts of fly ash, 9 parts of polycarboxylate superplasticizer, 100 parts of composite expansion agent, 15 parts of modified adhesive, and 180 parts of water.

[0042] The modified aggregate is obtained by pre-treating aggregate and then modifying it. The aggregate is a mixture of ceramic waste, waste slag, and construction waste concrete, with a weight ratio of 1:1:2. The pre-treatment involves pre-crushing the aggregate, sorting out uncrushable impurities, removing waste wood and plastic, and performing initial magnetic separation to remove waste iron. After sieving, recycled aggregate with an average particle size of 20 mm is obtained. The modification treatment involves immersing the recycled aggregate in a sodium silicate solution and stirring at 120 r / min for 3 hours, followed by immersion in a glacial acetic acid solution and stirring at 80 r / min for 20 minutes to obtain the modified aggregate.

[0043] The composite expanding agent is a calcium source expanding agent and a magnesium source expanding agent in a mass ratio of 25:75. The calcium source expanding agent is a compound of calcium oxide and calcium sulfoaluminate, with a mass ratio of 1:1. The magnesium source expanding agent is a compound of magnesium oxide and magnesium chloride, with a mass ratio of 1:4.

[0044] The modified adhesive material is composed of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide, and the mass ratio of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide is 9:6:7:4:5:2.

[0045] The preparation method of the low-shrinkage stabilized concrete in Example 1 above is as follows:

[0046] S1. Add silicate cement, modified aggregate, fly ash and composite expansive agent to a mixer and mix at 100 r / min for 5 min to obtain dry mix;

[0047] S2. Add water, polycarboxylate superplasticizer, and modified adhesive to the dry mix, and continue mixing for 60 minutes to obtain concrete mixture;

[0048] S3. The concrete mixture is placed in the mold and cured until the specified age is reached to obtain low-shrinkage stable concrete.

[0049] Example 2:

[0050] A low-shrinkage stabilized concrete is composed of the following components in parts by weight: 400 parts aluminate cement, 600 parts modified aggregate, 35 parts fly ash, 3 parts polycarboxylate superplasticizer, 90 parts composite expansion agent, 25 parts modified adhesive, and 160 parts water.

[0051] The modified aggregate is obtained by pre-treating aggregate and then modifying it. The aggregate is a mixture of coal gangue, sea stone, sea sand, and construction waste concrete, with a weight ratio of 1:1:2:4. The pre-treatment involves pre-crushing the aggregate, sorting out uncrushable impurities, removing waste wood and plastic, and performing initial magnetic separation to remove waste iron. After sieving, recycled aggregate with an average particle size of 10 mm is obtained. The modification treatment involves immersing the recycled aggregate in a sodium silicate solution and stirring at 100 r / min for 5 hours, followed by immersion in a glacial acetic acid solution and stirring at 50 r / min for 35 minutes to obtain the modified aggregate.

[0052] The composite expanding agent is a calcium source expanding agent and a magnesium source expanding agent in a mass ratio of 35:65. The calcium source expanding agent is a compound of calcium oxide and calcium sulfoaluminate, and the mass ratio of calcium oxide to calcium sulfoaluminate is 1:3. The magnesium source expanding agent is a compound of magnesium oxide and magnesium chloride, and the mass ratio of magnesium oxide to magnesium chloride is 1:2.

[0053] The modified adhesive material is composed of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide, and the mass ratio of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide is 7:8:5:6:6:1.

[0054] The preparation method of the low-shrinkage stabilized concrete in Example 2 above is as follows:

[0055] S1. Add silicate cement, modified aggregate, fly ash and composite expansion agent to a mixer and mix at 50 r / min for 10 min to obtain dry mix;

[0056] S2. Add water, polycarboxylate superplasticizer, and modified adhesive to the dry mix, and continue stirring for 20 minutes to obtain concrete mixture;

[0057] S3. The concrete mixture is placed in the mold and cured until the specified age is reached to obtain low-shrinkage stable concrete.

[0058] Example 3:

[0059] A low-shrinkage stabilized concrete is composed of the following components in parts by weight: 300 parts silicate cement, 800 parts modified aggregate, 30 parts fly ash, 7 parts polycarboxylate superplasticizer, 96 parts composite expansion agent, 20 parts modified adhesive, and 170 parts water.

[0060] The modified aggregate is obtained by pre-treating aggregate and then modifying it. The aggregate is a mixture of ceramic waste, waste slag, coal gangue, and construction waste concrete, with a weight ratio of 1:1:1:4. The pre-treatment involves pre-crushing the aggregate, sorting out uncrushable impurities, removing waste wood and plastic, and performing initial magnetic separation to remove waste iron. After sieving, recycled aggregate with an average particle size of 10 mm is obtained. The modification treatment involves immersing the recycled aggregate in a sodium silicate solution and stirring at 110 r / min for 4 hours, followed by immersion in a glacial acetic acid solution and stirring at 70 r / min for 30 minutes to obtain the modified aggregate.

[0061] The composite expanding agent is a calcium source expanding agent and a magnesium source expanding agent in a mass ratio of 30:70. The calcium source expanding agent is a compound of calcium oxide and calcium sulfoaluminate, with a mass ratio of 1:2. The magnesium source expanding agent is a compound of magnesium oxide and magnesium chloride, with a mass ratio of 1:3.

[0062] The modified adhesive material is composed of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide, and the mass ratio of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide is 8:7:6:5:5.5:1.5.

[0063] The preparation method of the low-shrinkage stabilized concrete in Example 3 above is as follows:

[0064] S1. Add silicate cement, modified aggregate, fly ash and composite expansive agent to a mixer and mix at 80 r / min for 7 min to obtain dry mix;

[0065] S2. Add water, polycarboxylate superplasticizer, and modified adhesive to the dry mix, and continue stirring for 40 minutes to obtain concrete mixture;

[0066] S3. The concrete mixture is placed in the mold and cured until the specified age is reached to obtain low-shrinkage stable concrete.

[0067] Comparative Example 1:

[0068] The difference between Comparative Example 1 and Example 3 is that the expanding agent in Comparative Example 1 is only calcium oxide expanding agent, while the rest is the same as in Example 3.

[0069] Comparative Example 2:

[0070] The difference between Comparative Example 2 and Example 3 is that the expanding agent in Comparative Example 2 is only calcium sulfoaluminate expanding agent, while the rest is the same as in Example 3.

[0071] Comparative Example 3:

[0072] The difference between Comparative Example 3 and Example 3 is that the expanding agent in Comparative Example 3 is only magnesium oxide expanding agent, while the rest is the same as in Example 3.

[0073] Comparative Example 4:

[0074] The difference between Comparative Example 4 and Example 3 is that the expanding agent in Comparative Example 4 is only magnesium chloride expanding agent, while the rest is the same as in Example 3.

[0075] Comparative Example 5:

[0076] The difference between Comparative Example 5 and Example 3 is that the expanding agent in Comparative Example 5 is a calcium oxide-magnesium oxide composite expanding agent, and the mass ratio of calcium oxide to magnesium oxide is 1:1. Everything else is the same as in Example 3.

[0077] Comparative Example 6:

[0078] The difference between Comparative Example 6 and Example 3 is that the expanding agent in Comparative Example 6 is a calcium oxide-magnesium chloride composite expanding agent, and the mass ratio of calcium oxide to magnesium chloride is 1:1. Everything else is the same as in Example 3.

[0079] Comparative Example 7:

[0080] The difference between Comparative Example 7 and Example 3 is that the composite expanding agent in Comparative Example 7 is a calcium source expanding agent and a magnesium source expanding agent with a mass ratio of 70:30.

[0081] Comparative Example 8:

[0082] Compared with Example 3, Comparative Example 8 differs in that the modified aggregate in Comparative Example 8 is replaced with conventional fine aggregate and coarse aggregate, and the mass ratio of fine aggregate to coarse aggregate is 1:1.5.

[0083] Comparative Example 9:

[0084] The difference between Comparative Example 9 and Example 3 is that no modified adhesive material was added in Comparative Example 9.

[0085] Performance testing methods

[0086] I. Principle of shrinkage resistance test: This application refers to the method described in GB / T 50082-2024 Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete to test the shrinkage rate of low-shrinkage stable concrete specimens.

[0087] Sample preparation: The sample size is 100mm×100mm×515mm prism specimen, which is divided into control group and test group. The test group corresponds to each embodiment, and the control group corresponds to each comparative example.

[0088] Curing conditions: The specimens were cured in the air with the mold on for 24 hours. After demolding, the specimens were placed in a standard curing room (temperature 20℃ ± 2℃, relative humidity ≥ 95%). After 3 days of curing, the specimens were removed and their initial length was measured using a horizontal shrinkage meter. After measurement, the specimens were transferred to a constant temperature and humidity chamber (temperature 20℃ ± 2℃, relative humidity 60% ± 5%), with a distance ≥ 30 mm between specimens. At different curing periods (including 1 day, 3 days, 5 days, 7 days, 10 days, 14 days, 28 days, 45 days, 90 days, 120 days, and 180 days) after the low-shrinkage stabilized concrete specimens were transferred to the constant temperature and humidity chamber, the shrinkage value of the low-shrinkage stabilized concrete was measured at specified time intervals. After measurement, the shrinkage rate of the low-shrinkage stabilized concrete was calculated using a formula.

[0089]

[0090] Where: ε st — Shrinkage rate of low-shrinkage stable concrete at age t (d), where t is calculated from the initial length of the measurement;

[0091] L0—Initial reading of specimen length (mm);

[0092] L t —The length reading (mm) of the specimen measured at the test age t (d);

[0093] L b — Gauge length of the specimen (mm).

[0094] Results processing: After obtaining the shrinkage rate after 180 days, the ratio of the shrinkage rate of each experimental group to the shrinkage rate of the control group was calculated, and the result was recorded as the relative shrinkage rate. The results are shown in Table 1.

[0095] Table 1 sample Relative shrinkage rate / % Example 1 53.4% Example 2 54.1% Example 3 52.1% Comparative Example 1 98.3% Comparative Example 2 98.5% Comparative Example 3 97.4% Comparative Example 4 98.1% Comparative Example 5 78.6% Comparative Example 6 75.3% Comparative Example 7 64.5% Comparative Example 8 67.9% Comparative Example 9 61.8%

[0096] As shown in Table 1, the relative shrinkage rates measured in Examples 1-3 were all lower than those in Comparative Examples 1-9, indicating that the concrete of the present invention has excellent low-shrinkage performance. A comparison of Comparative Examples 1-4 with Example 3 shows that only by combining the calcium source expansion agent made of calcium oxide and calcium sulfoaluminate with the magnesium source expansion agent made of magnesium oxide and magnesium chloride can the excellent low-shrinkage performance be achieved; using either one alone significantly increases the concrete shrinkage rate. A comparison of Comparative Examples 5-7 with Example 3 shows that only by combining the calcium source expansion agent made of calcium oxide and calcium sulfoaluminate with the magnesium source expansion agent made of magnesium oxide and magnesium chloride in a specific ratio can the excellent low-shrinkage performance be achieved; changing the ratio or omitting a component significantly increases the concrete shrinkage rate. A comparison of Comparative Examples 8-9 with Example 3 shows that the absence of modified aggregates or modified adhesives also affects the concrete shrinkage rate, indicating that the modified aggregates and modified adhesives of the present invention can reduce the concrete shrinkage rate.

[0097] II. Principle of Strength Performance Testing: This application refers to the method described in GB / T50081-2019 Standard for Test Methods of Physical and Mechanical Properties of Concrete to test the compressive strength of low-shrinkage stable concrete specimens.

[0098] Sample preparation: The sample size is 100mm×100mm×515mm prism specimen, which is divided into control group and test group. The test group corresponds to each embodiment, and the control group corresponds to each comparative example.

[0099] Curing conditions and result processing: After curing for 28 hours, the specimen was placed on a pressure testing machine and continuously loaded at a loading rate of 1 MPa / s until the specimen failed. The maximum failure load was recorded to obtain the compressive strength. The results are shown in Table 2.

[0100] Table 2 sample Compressive strength / MPa Example 1 50.6 Example 2 52.1 Example 3 53.4 Comparative Example 1 48.1 Comparative Example 2 46.9 Comparative Example 3 47.4 Comparative Example 4 49.3 Comparative Example 5 48.2 Comparative Example 6 47.6 Comparative Example 7 42.4 Comparative Example 8 26.3 Comparative Example 9 25.7

[0101] Table 2 shows that the compressive strength measured in Examples 1-3 is higher than that in Comparative Examples 1-9, indicating that the concrete of the present invention has excellent compressive strength. A comparison between Comparative Examples 1-7 and Example 3 shows that the combination of calcium-based expansive agents made from calcium oxide and calcium sulfoaluminate with magnesium-based expansive agents made from magnesium oxide and magnesium chloride has little effect on the compressive strength of the concrete. A comparison between Comparative Examples 8-9 and Example 3 shows that the absence of modified aggregates or modified adhesives significantly reduces the compressive strength of the concrete, indicating that the modified aggregates and modified adhesives of the present invention can improve the compressive strength of the concrete and enhance its stability in use.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A low shrinkage stabilized concrete, characterized by, It is composed of the following components in parts by weight: 200-400 parts cement, 600-1000 parts modified aggregate, 28-35 parts fly ash, 3-9 parts water-reducing agent, 90-100 parts composite expansive agent, 15-25 parts modified adhesive, and 160-180 parts water; the composite expansive agent is a mixture of calcium-based expansive agent and magnesium-based expansive agent, and the mass ratio of the calcium-based expansive agent to the magnesium-based expansive agent is (25-35):(65-75).

2. The low-shrinkage stabilized concrete according to claim 1, characterized in that, The calcium source expanding agent is a compound of calcium oxide and calcium sulfoaluminate, and the magnesium source expanding agent is a compound of magnesium oxide and magnesium chloride.

3. The low-shrinkage stabilized concrete according to claim 2, characterized in that, The mass ratio of calcium oxide to calcium sulfoaluminate is 1:(1-3); the mass ratio of magnesium oxide to magnesium chloride is 1:(2-4).

4. The low-shrinkage stabilized concrete according to claim 1, characterized in that, The modified aggregate is obtained by pre-treating aggregate and then modifying it.

5. The low-shrinkage stabilized concrete according to claim 4, characterized in that, The aggregate is one or more of stone, mortar, ceramic waste, waste slag and coal gangue, sea stone and sea sand, mixed with construction waste concrete.

6. The low-shrinkage stabilized concrete according to claim 5, characterized in that, The pretreatment involves: pre-crushing the aggregate, sorting out the uncrushable debris, removing waste wood and plastic, and simultaneously performing initial magnetic separation to remove waste iron from the aggregate. After screening, recycled aggregate with an average particle size of 10mm to 20mm is obtained.

7. The low-shrinkage stabilized concrete according to claim 6, characterized in that, The modification process is as follows: the recycled aggregate is soaked in a sodium silicate solution and stirred at a stirring speed of 100 r / min to 120 r / min for 3 h to 5 h, and then soaked in a glacial acetic acid solution and stirred at a stirring speed of 50 r / min to 80 r / min for 20 min to 35 min to obtain the modified aggregate.

8. The low-shrinkage stabilized concrete according to claim 1, characterized in that, The modified adhesive is composed of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide, and the mass ratio of tricalcium silicate, dicalcium silicate, dicalcium aluminate, tricalcium aluminate, tetracalcium aluminoferrite, and silicon dioxide is (7-9):(6-8):(5-7):(4-6):(5-6):(1-2).

9. The low-shrinkage stabilized concrete according to claim 1, characterized in that, The cement is at least one of silicate cement, sulfoaluminate cement, and aluminate cement; the water-reducing agent is a polycarboxylate water-reducing agent.

10. A method for preparing low-shrinkage stabilized concrete, characterized in that, The preparation method includes the following steps: S1. Add cement, modified aggregate, fly ash and composite expansion agent to a mixer and mix at a speed of 50r / min~100r / min for 5min~10min to obtain dry mix; S2. Add water, water-reducing agent, and modified adhesive to the dry mix, and continue mixing for 20 to 60 minutes to obtain concrete mixture; S3. The concrete mixture is placed in the mold and cured until the specified age is reached to obtain low-shrinkage stable concrete.

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