Low-shrinkage, high-crack-resistance and low-carbon concrete based on low-carbon cementing material and preparation method of low-shrinkage, high-crack-resistance and low-carbon concrete

Abstract

The invention discloses low-shrinkage, high-crack-resistance and low-carbon concrete based on a low-carbon cementing material and a preparation method of the low-shrinkage, high-crack-resistance and low-carbon concrete, and the low-shrinkage, high-crack-resistance and low-carbon concrete based on the low-carbon cementing material is prepared from the following raw materials: the low-carbon cementing material, sand, gravel, water and an additive. The low-carbon cementing material is obtained by compounding cement, a low-carbon admixture and a shrinkage-reducing anti-cracking material; the low-carbon admixture is obtained by compounding a carbon sequestration phase and an aluminum-rich phase; the shrinkage-reducing anti-cracking material is a high-performance calcium sulphoaluminate expanding agent or a calcium oxide-magnesium oxide composite expanding agent. According to the low-shrinkage, high-crack-resistance and low-carbon concrete, on the premise that workability and strength performance are guaranteed, the 28d drying shrinkage rate is reduced by 30% or above, the slab cracking area is smaller than 250 mm < 2 > / m < 2 >, the crack resistance reaches the L-IV level or above, the cement consumption of concrete per cubic meter is reduced by 20%-40%, the carbon emission of the concrete in the production process is effectively reduced, and the production cost is reduced. And the crack resistance of the concrete structure is greatly improved.

Description

Technical Field

[0001] This invention relates to a type of concrete, and more particularly to a low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials. Background Technology

[0002] In recent years, with the continuous advancement of railway infrastructure construction, a large number of mega- and large-scale hub passenger stations, represented by Shanghai East Station and Nanjing North Station, have been planned and constructed. Concrete structures are developing towards ultra-large, ultra-long, and ultra-high strength. As the size of passenger station concrete structures or components increases, the heat exchange rate between the concrete interior and exterior decreases, leading to greater internal and external temperature differences and temperature stress, thus increasing the risk of cracking in the structural concrete. At the same time, influenced by environmental policies and the uneven distribution of local material resources, the workability of manufactured sand concrete cannot reach the performance of traditional river sand concrete. Furthermore, manufactured sand concrete has a high amount of cementitious materials and a high cement content, resulting in poor crack resistance. The combined effects of internal and external temperature differences and the shrinkage deformation of the concrete itself make concrete structures prone to cracking, leakage, and other engineering defects.

[0003] Concrete cracking has been a major technical problem in the engineering field for many years. In most cases, concrete cracking is caused by factors such as excessive temperature differences between the inside and outside of the concrete structure, excessive autogenous shrinkage and drying shrinkage, and rapid water loss. Common methods to solve concrete cracking include adding fibers, superabsorbent resins, expansion agents, and hydration temperature rise inhibitors. Among these:

[0004] Chinese patent CN 118164738 A, "A Crack-Resistant Concrete Containing Modified Polypropylene Fibers", proposes using modified polypropylene fibers to overcome the problems of poor dispersibility and easy agglomeration of conventional polypropylene fibers in concrete, weak interfacial adhesion, and easy pull-out under stress.

[0005] Chinese patent CN 119019127 A, "A Crack-Resistant Concrete and Its Preparation Method," proposes the combined use of emulsifiers, superabsorbent resin particles, and expansive agents to improve the crack resistance of concrete. The emulsifier forms a dense, stable monomolecular film on the concrete surface, reducing the evaporation rate of moisture and lowering the risk of plastic cracking. The superabsorbent resin utilizes its water absorption and release properties to increase the capillary saturation and relative humidity of the concrete system, reducing capillary negative pressure and slowing down the rate of moisture loss within the concrete, thereby reducing or even eliminating autogenous shrinkage. The expansive agent controls the drying shrinkage of the concrete.

[0006] Chinese patent CN 119707372 A, "A Low-Shrinkage, High-Crack-Resistant Concrete and Its Application", proposes a crack-resistant agent with a cellulose-grafted hyperbranched polycarboxylic acid and diacetone glucose polyacrylate structure. Through the dual effects of high water absorption and slow release, it reduces the self-shrinkage of concrete caused by low water-cement ratio and pore self-drying.

[0007] However, all of the aforementioned patents suffer from varying degrees of drawbacks: insufficient fiber content results in insignificant improvement in crack resistance, while increased fiber content negatively impacts the retention of mixture properties and mechanical properties over time. The water absorption rate of superabsorbent resins is greatly affected by particle size; a slow absorption rate can lead to excessively rapid slump loss in concrete, particle floating after saturation, and excessively large pore diameters after water release. Calcium oxide-based expansive agents exhibit excessively rapid expansion, often releasing their expansion capacity while the concrete is still in the plastic stage, failing to compensate for shrinkage in the hardened concrete. Retarded polycarboxylate superplasticizers, due to their slower action, can easily cause problems such as delayed bleeding and water reabsorption, affecting on-site construction. Furthermore, all of the aforementioned crack-resistant measures increase concrete production costs to some extent. Moreover, none of these technical measures consider low-carbon concrete, and the production processes of functional additives such as fibers, superabsorbent resins, and calcium oxide expansive agents generate significant amounts of carbon dioxide, further increasing carbon emissions from concrete preparation.

[0008] The application prospects of low-carbon concrete are very promising. Considering that the carbon emissions of cementitious materials usually account for more than 70% of the carbon emissions of concrete, the most effective technical approach to achieving low-carbon concrete is to use low-carbon cementitious materials. The specific measures are to reduce the proportion of cement in cementitious materials and increase the amount of industrial by-products such as mineral admixtures.

[0009] Chinese patent CN 117776628 A, "A Low-Carbon Concrete and Its Preparation Method", proposes to prepare low-carbon concrete using cement, recycled glass powder, nano-calcium carbonate, silica fume, activated limestone powder, and modified rice husk ash. This technical solution only considers carbon emissions and does not take into account the crack resistance and shrinkage deformation of concrete. At the same time, the cost of nano-calcium silicate and silica fume is relatively high, and the storage and measurement of as many as 5 to 6 kinds of cementitious materials in the concrete production process also bring many challenges.

[0010] Chinese patent CN 117024074 A, "A Low-Carbon Concrete and Its Preparation Method," proposes using composite admixtures to improve the early-stage doping efficiency of fly ash and enhance the early-stage strength of fly ash concrete. This technical solution has certain regional limitations. As is well known, fly ash is an industrial byproduct of thermal power generation, widely distributed in Shanxi, Inner Mongolia, Gansu, and Ningxia in my country, but scarce in Sichuan, Tibet, Xinjiang, and Yunnan. Therefore, the application of this technical solution is limited. Furthermore, alkali metal ions such as sodium and potassium in the composite admixtures can easily cause the alkali content of concrete to exceed the standard, posing a risk of alkali-aggregate reaction.

[0011] Chinese patent CN 116535168 A, "A Low-Carbon Concrete and Its Preparation Method," proposes using modified optical fiber particles, silica fume, fly ash, and slag powder to prepare low-carbon concrete. The core technology lies in modifying the optical fiber particles through calcination at 800℃~1000℃, overcoming the current problem of low utilization rates of quartz optical fiber waste and silicon crystal waste. However, this technical solution adds 100~120 parts of silica fume without considering the crack resistance and volumetric deformation properties of the prepared concrete, and also fails to address issues such as whether the radioactive content of the optical fiber waste and silicon crystal waste meets standards.

[0012] In summary, existing technologies have not yet achieved a synergistic balance between low carbon emissions and high crack resistance in concrete, and no specific classifications or regulations regarding the carbon emissions of low-carbon cementitious materials and low-carbon concrete have been found. Therefore, there is an urgent need to propose a method for developing low-shrinkage, high-crack-resistance, low-carbon concrete based on low-carbon cementitious materials and its preparation. Summary of the Invention

[0013] The purpose of this invention is to reduce carbon emissions during concrete production while significantly improving the volume stability and crack resistance of concrete, providing a low-shrinkage, high-crack-resistance, low-carbon concrete based on low-carbon cementitious materials. The prepared low-carbon concrete, while ensuring workability and compressive strength, has advantages such as lower shrinkage, better crack resistance, and lower carbon emissions. It is suitable for C30-C50 strength grade concrete, and its technical and economic advantages are particularly significant in areas lacking high-quality fly ash resources.

[0014] Another objective of this invention is to provide a method for preparing low-shrinkage, high-crack-resistance, low-carbon concrete based on low-carbon cementitious materials. The concrete produced by this method has the characteristics of good homogeneity and excellent durability, and can effectively reduce the heat of hydration of cementitious materials and the adiabatic temperature rise of concrete.

[0015] In order to achieve the purpose of this invention, the inventors conducted extensive experiments and research and tireless exploration, and finally obtained the following technical solution:

[0016] A low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials, characterized by comprising the following raw materials in parts by weight:

[0017] 320-450 parts of low-carbon cementitious material;

[0018] 650-800 parts of sand;

[0019] 900-1000 parts of crushed stone;

[0020] 120-160 parts water;

[0021] 3-5 parts of admixture;

[0022] The low-carbon cementitious material is a compound of cement, low-carbon admixture and shrinkage-reducing and crack-resistant material, wherein cement accounts for 120-180 parts, low-carbon admixture accounts for 180-320 parts, and shrinkage-reducing and crack-resistant material accounts for 20-40 parts.

[0023] The low-carbon admixture is obtained by compounding a solid carbon phase and an aluminum-rich phase;

[0024] The shrinkage-reducing and crack-resistant material is a high-performance calcium sulfoaluminate expanding agent or a calcium oxide-magnesium oxide composite expanding agent.

[0025] Cement, as a hydraulic binder, is a crucial source of early strength development in concrete. However, cement production generates significant carbon emissions. Replacing some cement with other powdered materials (such as fly ash and slag powder) can substantially reduce carbon dioxide emissions. However, with the shift of infrastructure construction focus to border regions and the vigorous promotion of clean energy sources like wind and hydropower, high-quality traditional mineral admixtures such as fly ash and slag powder are becoming increasingly scarce. In Xinjiang and Tibet, the price of fly ash delivered to construction sites is even higher than that of cement. Meanwhile, due to historical reasons, large quantities of solid waste such as kaolin, coal gangue, steel slag, and tailings have accumulated around border regions. Processing and utilizing these solid wastes to replace cement could not only directly reduce carbon emissions during concrete production but also improve problems such as high shrinkage and cracking caused by high cement usage in modern concrete.

[0026] The low-carbon admixture is obtained by compounding a carbon-fixing phase and an aluminum-rich phase. The aluminum-rich phase is obtained by initially grinding and crushing the aluminum-rich ore, followed by low-temperature calcination at 600℃~800℃ for 1~2 hours. The aluminum-rich ore specifically includes kaolin, clay, coal gangue, steel slag, and tailings. Due to geological sedimentation and environmental factors, these ores have low content of glassy substances and low potential hydration activity, making them difficult to directly replace cement. The low-temperature calcination process at 600℃~800℃ can open the Si-O and Al-O bonds in the ore, transforming the crystalline state into a glassy state, significantly improving the hydration activity of the aluminum-rich phase.

[0027] By combining cement with the aforementioned low-carbon admixtures, the amount of cement used per cubic meter of concrete can be reduced by 20% to 40% compared to the original amount, thereby significantly reducing carbon emissions during the concrete production process and helping the building materials industry achieve "carbon peak" and "carbon neutrality" as soon as possible.

[0028] By adopting the above technical solutions and controlling the mass ratio of shrinkage-reducing and crack-resistant materials in low-carbon cementitious materials, the strength development and durability of concrete can be dynamically adjusted. When the cement content is high, the early strength development of concrete is faster, but carbon emissions are higher, and the risk of cracking is also higher. Therefore, it is necessary to increase the mass ratio of shrinkage-reducing and crack-resistant materials in low-carbon cementitious materials accordingly. When the low-carbon admixture content is high, the 3-day strength development of concrete may be slower, but the strength development at 7 days and beyond is normal, with lower costs and carbon emissions, and a lower risk of cracking. Accordingly, the mass ratio of shrinkage-reducing and crack-resistant materials in low-carbon cementitious materials can be appropriately reduced. It is evident that controlling the proportions of each component in low-carbon cementitious materials within a certain range can, on the one hand, control the production cost of concrete while ensuring mechanical and durability performance, and on the other hand, has significant implications for controlling concrete carbon emissions and cracking risk. This makes low-carbon concrete have good practical significance and promising prospects for widespread application.

[0029] Preferably, the low-carbon admixture is prepared by the following method:

[0030] S1. Calcination: The aluminum-rich phase ore is initially ground and crushed, and then calcined at a low temperature of 600℃~800℃ for 1h~2h to obtain the aluminum-rich phase.

[0031] S2. Grinding: The calcined alumina-rich phase and carbon-fixed phase are thoroughly ground in a ball mill until a fine powder mixture with a fineness of 45μm is obtained.

[0032] By adopting the above technical solution, the Si-O bonds and Al-O bonds in the crystalline minerals of the aluminum-rich phase are opened by low-temperature calcination, thereby increasing the content of glassy components in the aluminum-rich phase. Then, by fully grinding with the carbon-fixed phase in a ball mill, the fineness and specific surface area are significantly improved, thereby further enhancing its reactivity.

[0033] Preferably, the aluminum-rich phase in S1 is any one of metakaolin, calcined clay, calcined coal gangue, steel slag powder, and tailings powder.

[0034] Preferably, the carbon-fixed phase in S2 is any one of ultrafine limestone powder, heavy calcium carbonate powder, dolomite powder, and marble powder.

[0035] Preferably, when the concrete strength grade is C25, C30 and C35, the shrinkage-reducing and crack-resistant material is a high-performance calcium sulfoaluminate expansive agent; when the concrete strength grade is C40, C45 and C50, the shrinkage-reducing and crack-resistant material is a calcium oxide-magnesium oxide composite expansive agent.

[0036] The expansion properties of high-performance calcium sulfoaluminate are greatly affected by the moisture content in concrete. The water content per cubic meter of concrete with strength grades C25, C30, and C35 is generally above 160 kg. Therefore, it is recommended to use high-performance calcium sulfoaluminate expansion agent. The expansion properties of calcium oxide-magnesium oxide mixtures are significantly affected by the temperature and structural constraints of concrete. C40, C45, and C50 strength grades are mostly large-volume concrete structures that bear the main load, and even include prestressed concrete structures. Therefore, it is recommended to use calcium oxide-magnesium oxide composite expansion agent.

[0037] Preferably, the high-performance calcium sulfoaluminate expanding agent is HP-CSA, with a sieve residue of no more than 15% on a 75-micron square hole sieve, a 7-day restricted expansion rate of more than 0.1% in water, and a 28-day restricted expansion rate of more than 0.06% in air.

[0038] Preferably, the calcium oxide-magnesium oxide composite expanding agent is a type HME-V composite expanding agent, with a sieve residue of no more than 10% on a 75-micron square hole sieve, a 7-day restricted expansion rate of more than 0.05% in water, and a 28-day restricted expansion rate of more than 0.01% in air.

[0039] A method for preparing low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials, characterized by comprising the following steps:

[0040] P1. Premixing: Low-carbon cementitious materials, sand, and crushed stone are put into a special mixer and mixed until uniform to obtain dry mixture;

[0041] P2. Mixing: Add the dry mix, water and admixtures into a forced mixer and mix for no less than 120 seconds to obtain low-shrinkage, high-crack-resistant, low-carbon concrete with a slump of 180mm~220mm.

[0042] The above preparation method has the advantages of simple operation and stable quality. The prepared concrete has good workability, mechanical properties and durability. At the same time, it makes comprehensive use of industrial solid wastes such as kaolin, coal gangue, steel slag and tailings, effectively reducing the amount of cement in the concrete and greatly reducing the carbon emissions in the concrete production process, which helps to achieve low-carbon concrete preparation.

[0043] Beneficial effects

[0044] 1. This invention uses aluminum-rich phases such as calcined metakaolin, calcined clay, calcined coal gangue, steel slag powder, and tailings powder, as well as carbon-fixing phases such as ultrafine limestone powder, heavy calcium carbonate powder, dolomite powder, and marble powder to replace cement in concrete preparation. This can reduce the amount of cement used per cubic meter of concrete by 20% to 40% compared to the original method, effectively reducing concrete production costs and cracking risks.

[0045] 2. This invention addresses the characteristics of water consumption and structural type in concrete of different strength grades. It proposes to use high-performance calcium sulfoaluminate expansive agent to prepare concrete of strength grades C25, C30 and C35, and to use calcium oxide-magnesium oxide composite expansive agent to prepare concrete of strength grades C40, C45 and C50. This invention is more targeted at the practical operation level and can ensure the actual application effect in engineering.

[0046] 3. The method for preparing low-shrinkage, high-crack-resistance, and low-carbon concrete mentioned in this invention has the advantages of simple operation and stable quality. The prepared concrete has good workability, mechanical properties, and durability. At the same time, it comprehensively utilizes industrial solid wastes such as coal gangue, steel slag, and tailings, effectively reducing the amount of cement used in concrete and greatly reducing the carbon emissions in the concrete production process, which helps to achieve low-carbon concrete preparation. Attached Figure Description

[0047] Figure 1 This is a flowchart of a method for preparing low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials, provided by the present invention. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to the embodiments.

[0049] The cement is silicate cement with optimized particle size distribution, wherein cement particles with a particle size of 0~3μm account for 3~7%, cement particles with a particle size of 3μm~10μm account for 7~20%, cement particles with a particle size of 1μm~20μm account for 30%~50%, cement particles with a particle size of 20μm~50μm account for 7~20%, and cement particles with a particle size greater than 50μm account for 3~7%.

[0050] The low-carbon admixture has a flowability ratio ≥105%, an activity index ≥80% at 7 days and 28 days, and a residue of ≤10% on a 45μm sieve.

[0051] The shrinkage-reducing and crack-resistant material has a 75-micron square hole sieve residue of no more than 15%, a 7-day restricted expansion rate in water of ≥0.05%, and a 28-day restricted expansion rate in air of greater than 0.06%.

[0052] The crushed stone is a continuous particle size of 5~31.5mm granite aggregate with a porosity of ≤40%.

[0053] The sand is manufactured limestone sand with a bulk density of 1500~1650 kg / m³. 3 The gradation belongs to medium sand in Zone II.

[0054] The admixtures include polycarboxylate-based high-performance water-reducing agents with a water reduction rate of not less than 30% and high-efficiency air-entraining agents with an air-entraining efficiency of >50%.

[0055] The water is tap water.

[0056] Example of preparation of low-carbon admixtures

[0057] Preparation Example 1

[0058] A low-carbon admixture is prepared by the following method:

[0059] S1. Calcination: Kaolinite and iron tailings are initially ground and crushed, and then calcined at a low temperature of 750℃ for 1 hour to obtain an aluminum-rich phase. The Al2O3 content of kaolinite is not less than 30%, the Al2O3 content of iron tailings is not less than 20%, and the mass ratio of kaolinite to iron tailings is 6:4.

[0060] S2. Grinding: The calcined alumina-rich phase and limestone are ball-milled in a ball mill at a speed of 50 r / min for 1 hour to fully grind into a low-carbon admixture with a fineness of no more than 10% of 75 micrometers, wherein the CaCO3 content of the limestone is no less than 90%.

[0061] Preparation Example 2

[0062] A low-carbon admixture is prepared by the following method:

[0063] S1. Calcination: Coal gangue and iron tailings are initially ground and crushed, and then calcined at a low temperature of 700℃ for 2 hours to obtain an aluminum-rich phase. The Al2O3 content of coal gangue is not less than 25%, the Al2O3 content of iron tailings is not less than 20%, and the mass ratio of coal gangue to iron tailings is 5:5.

[0064] S2. Grinding: The calcined aluminum-rich phase and marble are ball-milled in a ball mill at a speed of 50 r / min for 1.5 h to fully grind into a low-carbon admixture with a fineness of 75 microns and a fineness of no more than 10%, wherein the CaCO3 content of the marble is no less than 75%.

[0065] Preparation Example 3

[0066] A low-carbon admixture is prepared by the following method:

[0067] S1. Calcination: Coal gangue and steel slag are initially ground and crushed, and then calcined at low temperature at 800℃ for 2 hours to obtain an aluminum-rich phase. The Al2O3 content of coal gangue is not less than 25%, the Al2O3 content of steel slag is not less than 15%, and the mass ratio of coal gangue to iron tailings is 7:3.

[0068] S2. Grinding: The calcined aluminum-rich phase and dolomite are ball-milled in a ball mill at a speed of 50 r / min for 2 hours to fully grind into a low-carbon admixture with a fineness of 75 microns and a fineness of no more than 10%, wherein the CaCO3 content of the dolomite is no less than 80%.

[0069] Preparation Example 4

[0070] A low-carbon admixture is prepared by the following method:

[0071] S1. Calcination: Kaolinite and clay are initially ground and crushed, and then calcined at a low temperature of 700℃ for 1 hour to obtain an aluminum-rich phase. The Al2O3 content of kaolinite is not less than 30%, the Al2O3 content of clay is not less than 20%, and the mass ratio of kaolinite to clay is 6:4.

[0072] S2. Grinding: The calcined alumina-rich phase and limestone are ball-milled in a ball mill at a speed of 50 r / min for 1 hour to fully grind into a low-carbon admixture with a fineness of no more than 10% of 75 micrometers, wherein the CaCO3 content of the dolomite is no less than 90%.

[0073] Example 1

[0074] A low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials is provided. The raw material composition is shown in Table 1. The low-carbon admixture used is the one from Preparation Example 1, and the crack-resistant and shrinkage-reducing material is the high-performance expansion agent HP-CSA.

[0075] The preparation steps are as follows:

[0076] Cement, low-carbon admixtures, shrinkage-reducing and crack-resistant materials, sand, and crushed stone are put into a special mixer and mixed until uniform to obtain dry mix. The dry mix, water, and admixtures are then put into a forced mixer and mixed for 180 seconds to obtain low-shrinkage, high-crack-resistant, low-carbon concrete with a slump of 180mm to 220mm.

[0077] Example 2

[0078] A low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials is provided. The raw material composition is shown in Table 1. The low-carbon admixture used is from Preparation Example 2, and the crack-resistant and shrinkage-reducing material is a high-performance expansive agent of model HP-CSA.

[0079] The preparation steps are as follows:

[0080] Cement, low-carbon admixtures, shrinkage-reducing and crack-resistant materials, sand, and crushed stone are put into a special mixer and mixed until uniform to obtain dry mix. The dry mix, water, and admixtures are then put into a forced mixer and mixed for 180 seconds to obtain low-shrinkage, high-crack-resistant, low-carbon concrete with a slump of 180mm to 220mm.

[0081] Example 3

[0082] A low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials is provided. The raw material composition is shown in Table 1. The low-carbon admixture used is from Preparation Example 3, and the crack-resistant and shrinkage-reducing material is a high-performance expansive agent of model HP-CSA.

[0083] The preparation steps are as follows:

[0084] Cement, low-carbon admixtures, shrinkage-reducing and crack-resistant materials, sand, and crushed stone are put into a special mixer and mixed until uniform to obtain dry mix. The dry mix, water, and admixtures are then put into a forced mixer and mixed for 180 seconds to obtain low-shrinkage, high-crack-resistant, low-carbon concrete with a slump of 180mm to 220mm.

[0085] Example 4

[0086] A low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials is provided. The raw material composition is shown in Table 1. The low-carbon admixture used is selected from Preparation Example 4, and the crack-resistant and shrinkage-reducing material is selected from the high-performance expansion agent HP-CSA.

[0087] The preparation steps are as follows:

[0088] Cement, low-carbon admixtures, shrinkage-reducing and crack-resistant materials, sand, and crushed stone are put into a special mixer and mixed until uniform to obtain dry mix. The dry mix, water, and admixtures are then put into a forced mixer and mixed for 180 seconds to obtain low-shrinkage, high-crack-resistant, low-carbon concrete with a slump of 180mm to 220mm.

[0089] Example 5

[0090] A low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials is provided. The raw material composition is shown in Table 1. The low-carbon admixture used is from Preparation Example 1, and the crack-resistant and shrinkage-reducing material is HME-V type composite expansion agent.

[0091] The preparation steps are as follows:

[0092] Cement, low-carbon admixtures, shrinkage-reducing and crack-resistant materials, sand, and crushed stone are put into a special mixer and mixed until uniform to obtain dry mix. The dry mix, water, and admixtures are then put into a forced mixer and mixed for 180 seconds to obtain low-shrinkage, high-crack-resistant, low-carbon concrete with a slump of 180mm to 220mm.

[0093] Example 6

[0094] A low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials is provided. The raw material composition is shown in Table 1. The low-carbon admixture used is from Preparation Example 2, and the crack-resistant and shrinkage-reducing material is HME-V type composite expansion agent.

[0095] The preparation steps are as follows:

[0096] Cement, low-carbon admixtures, shrinkage-reducing and crack-resistant materials, sand, and crushed stone are put into a special mixer and mixed until uniform to obtain dry mix. The dry mix, water, and admixtures are then put into a forced mixer and mixed for 180 seconds to obtain low-shrinkage, high-crack-resistant, low-carbon concrete with a slump of 180mm to 220mm.

[0097] Example 7

[0098] A low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials is provided. The raw material composition is shown in Table 1. The low-carbon admixture used is from Preparation Example 3, and the crack-resistant and shrinkage-reducing material is HME-V type composite expansion agent.

[0099] The preparation steps are as follows:

[0100] Cement, low-carbon admixtures, shrinkage-reducing and crack-resistant materials, sand, and crushed stone are put into a special mixer and mixed until uniform to obtain dry mix. The dry mix, water, and admixtures are then put into a forced mixer and mixed for 180 seconds to obtain low-shrinkage, high-crack-resistant, low-carbon concrete with a slump of 180mm to 220mm.

[0101] Example 8

[0102] A low-shrinkage, high-crack-resistant, low-carbon concrete based on low-carbon cementitious materials is provided. The raw material composition is shown in Table 1. The low-carbon admixture used is from Preparation Example 4, and the crack-resistant and shrinkage-reducing material is HME-V type composite expansion agent.

[0103] The preparation steps are as follows:

[0104] Cement, low-carbon admixtures, shrinkage-reducing and crack-resistant materials, sand, and crushed stone are put into a special mixer and mixed until uniform to obtain dry mix. The dry mix, water, and admixtures are then put into a forced mixer and mixed for 180 seconds to obtain low-shrinkage, high-crack-resistant, low-carbon concrete with a slump of 180mm to 220mm.

[0105] Table 1. Raw material composition and weight of low-carbon concrete in Examples 1-8 (unit: kg / m³) 3 )

[0106]

[0107] Performance testing of low-carbon concrete

[0108] Mechanical property testing methods:

[0109] The low-carbon concrete prepared in Examples 1-8 was used to prepare standard cubic specimens with dimensions of 150mm × 150mm × 150mm. For each mix proportion, four sets of specimens were formed at 3d, 7d, 14d, and 28d. After demolding, the standard specimens were placed in a standard curing room for curing. At the specified curing age, the compressive strength of the specimens was tested using a universal testing machine. The test results are shown in Table 2.

[0110] Table 2 Compressive strength of low-carbon concrete prepared in Examples 1-8

[0111]

[0112] Methods for testing shrinkage and crack resistance:

[0113] The low-carbon concrete prepared in Examples 1-8 were used to prepare standard prism specimens with dimensions of 400mm × 100mm × 100mm. For each mix proportion, three specimens were formed in one set. After demolding, the standard specimens were placed in a curing chamber with a humidity of 60% for curing, and the 28-day drying shrinkage rate of each concrete was tested. Flat crack-resistant specimens of the low-carbon concrete prepared in Examples 1-8 were formed according to the "Standard for Test Methods of Long-Term Performance and Durability of Concrete" GB / T 50082. Cracking was observed 24 hours after molding. The test results are shown in Table 3.

[0114] Table 3. Drying shrinkage rate and average crack area of ​​low-carbon concrete prepared in Examples 1-8

[0115]

[0116] Carbon emission calculation method:

[0117] The carbon emissions of building materials were calculated according to the calculation method given in GB / T 51366, the standard for calculating carbon emissions of building materials. The carbon emissions of the low-carbon concrete prepared in Examples 1 to 8 were calculated and the results are shown in Table 4.

[0118] Table 4. Carbon emissions of low-carbon concrete prepared in Examples 1-8

[0119]

[0120] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0121] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A low-shrinkage, high-anti-cracking, low-carbon concrete based on low-carbon cementitious materials, characterized in that, The low-carbon cementing material 320-450 parts by weight; Sand 650-800 parts by weight; Gravel 900-1000 parts by weight; Water 120-160 parts by weight; Admixtures 3-5 parts by weight; The low-carbon cementing material comprises cement, low-carbon admixture and shrinkage and crack resistance material, wherein the cement accounts for 120-180 parts by weight, the low-carbon admixture accounts for 180-320 parts by weight, and the shrinkage and crack resistance material accounts for 20-40 parts by weight; The low-carbon admixture comprises a carbon fixation phase and an aluminum-rich phase; The shrinkage and crack resistance material is high-performance calcium sulphoaluminate expansive agent or calcium oxide-magnesium oxide composite expansive agent. The carbon fixation phase accounts for 10-30% and the aluminum-rich phase accounts for 70-90% in the low-carbon admixture, and the low-carbon admixture is prepared by the following method:

2. The low-shrinkage, high-anti-cracking, low-carbon concrete based on low-carbon cementitious materials according to claim 1, characterized in that: S1, calcination: the aluminum-rich phase raw ore is preliminarily ground and crushed, and then is calcined at 600-800 DEG C for 1-2 hours to obtain the aluminum-rich phase; S2, grinding: the calcined aluminum-rich phase and the carbon fixation phase are fully ground in a ball mill to obtain a fine powder mixture with a fineness meeting the requirement of 45 microns. When the concrete strength grade is C25, C30 or C35, the shrinkage and crack resistance material is high-performance calcium sulphoaluminate expansive agent; when the concrete strength grade is C40, C45 or C50, the shrinkage and crack resistance material is calcium oxide-magnesium oxide composite expansive agent. 3.The low-shrinkage, high-anti-cracking, low-carbon concrete based on low-carbon cementitious materials according to claim 1, characterized in that: The aluminum-rich phase in S1 is any one of metakaolin, calcined clay, calcined coal gangue, steel slag powder or tailings powder; the carbon fixation phase in S2 is any one of ultra-fine limestone powder, heavy calcium powder, dolomite powder or marble powder.

4. The low-shrinkage, high-anti-cracking, low-carbon concrete based on low-carbon cementitious materials according to claim 2, characterized in that: The high-performance calcium sulphoaluminate expansive agent is preferably high-performance expansive agent of HP-CSA type, with a 75-micron square hole screen residue of not more than 15%, a 7-day limited expansion rate in water of greater than 0.1%, and a 28-day limited expansion rate in air of greater than 0.06%; the calcium oxide-magnesium oxide composite expansive agent is preferably composite expansive agent of HME-V type, with CaO accounting for 50-70% in the components, light-burned MgO accounting for 30-50%, a light-burned MgO reactivity value of 100-180 seconds, a 75-micron square hole screen residue of not more than 10%, a 7-day limited expansion rate in water of greater than 0.05%, and a 28-day limited expansion rate in air of greater than 0.01%.

5. The low shrinkage, high crack resistance, low carbon concrete based on low carbon cementitious materials according to claim 3, characterized in that: The carbon emission parameters of different types of low-carbon concrete are as follows:

6. The low-shrinkage, high-anti-cracking, low-carbon concrete based on low-carbon cementitious materials according to any one of claims 1-5, characterized in that: The low-carbon cementitious material has a carbon emission of less than 200 kgCO 2e / m 3 during the production process of the cementitious material used in the single-component concrete.

7. The low shrinkage, high crack resistance, low carbon concrete based on low carbon cementitious materials according to any one of claims 1-5, characterized by: The carbon emission accounting stage of the concrete includes the production and transportation stage of raw materials for the concrete and the production and transportation stage of the concrete. The carbon emissions of C25 concrete is less than 230 kgCO 2e / m 3 ; The carbon emission of C30 concrete is less than 240 kgCO 2e / m 3 ; The carbon emissions of C35 concrete is less than 260 kg CO 2e / m 3 ; The carbon emissions of the C40 concrete are less than 270 kg CO2 / m 2e / m 3 ; The carbon emission of C45 concrete is less than 300 kgCO 2e / m 3 ; The carbon emission of C50 concrete is less than 320 kgCO 2e / m 3 .

8. The low-shrinkage, high-anti-cracking, low-carbon concrete based on low-carbon cementitious materials according to claim 7, characterized by: The method comprises the following steps:

9. A method for preparing a low shrinkage, high crack resistance, low carbon concrete based on low carbon cementitious materials according to any one of claims 1-8, characterized in that, P1, premixing: the low-carbon cementing material, sand and gravel are put into a special mixer for mixing and stirring to obtain dry mixture; P2, stirring: the dry mixture, water and admixtures are put into a forced stirrer for stirring for not less than 120 seconds to obtain low-shrinkage, high-anti-crack, low-carbon concrete with a slump control of 180-220 mm, an air content of 2-4% and an out-machine temperature of less than 26 DEG C. ​

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