C60 commercial concrete with ultralow cement consumption

Abstract

The invention discloses C60 commercial concrete with ultralow cement consumption, and belongs to the technical field of building materials. In order to solve the technical problems that existing high-grade concrete is large in cement consumption and high in carbon emission, cracks are easily caused by hydration heat, and construction workability and strength are difficult to balance, the C60 commercial concrete which is low in carbon, environmentally friendly, high in strength and excellent in construction performance is provided by optimizing the component proportion and the preparation process. According to the concrete, cement and industrial byproduct mineral powder serve as a composite cementing material, the mass ratio of mud to the cementing material is not higher than 30%, a scientific and reasonable component system is formed in cooperation with a composite nano-based additive, and the dual purposes of resource recycling and low-carbon emission reduction are achieved. The concrete overturns the traditional cognition that high-grade concrete depends on high cement consumption, the preparation process is simple and controllable, the production cost is reasonable, and the concrete is suitable for various large-scale projects such as bridges, tunnels and high-rise buildings and has wide popularization and application prospects.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a C60 commercial concrete with ultra-low cement content. Background Technology

[0002] With the rapid development of my country's construction industry, high-grade concrete is increasingly widely used in projects such as large bridges, high-rise buildings, and industrial plants. C60, a common type of high-grade concrete, has become a key material for ensuring the safety of engineering structures due to its excellent strength properties. However, the preparation of traditional high-grade concrete faces many technical bottlenecks:

[0003] First, carbon emissions are a significant issue. Cement, as the core binder in concrete, requires large amounts of limestone and coal for its production. Each ton of cement produced emits approximately 616 kg of CO2, making it a major source of carbon emissions in the construction industry. Currently, traditional high-grade concrete uses excessive amounts of cement (typically exceeding 550 kg / m³ of total binder content). 3 (With cement accounting for over 60% of the total construction output, the carbon emission intensity is high, which seriously restricts the low-carbon transformation of the construction industry.)

[0004] Secondly, the heat of hydration easily leads to cracks. Cement releases a large amount of heat during hydration. High-cement-content C60 concrete experiences a significant increase in internal temperature, creating a large temperature difference with the external environment and generating thermal stress, which in turn causes cracks in the concrete structure. Cracks not only affect the aesthetics of the building but also reduce the structural integrity and durability, shorten the building's lifespan, and even pose safety hazards.

[0005] Furthermore, there is the challenge of balancing workability and strength. Traditional high-strength concrete often increases the amount of cement and water to ensure strength. However, excessive cement leads to poor cohesion and increased bleeding rate, while excessive water will form pores after the concrete hardens, reducing strength and durability. At the same time, high-strength concrete has a faster slump loss, which can easily cause problems such as caking and deactivation for ready-mixed concrete transported over long distances, affecting on-site construction efficiency and project quality.

[0006] Therefore, this invention proposes a commercial concrete that significantly reduces cement usage, carbon emissions, and inhibits hydration heat cracking while ensuring C60 strength grade, workability, and durability. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a C60 commercial concrete with ultra-low cement content, achieving multiple technical goals of "low cement content, high strength, good workability, and low carbon emissions", and solving the carbon emission and cracking problems of traditional high-grade concrete.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A C60 commercial concrete with ultra-low cement content, the commercial concrete comprising the following components: cement, mineral powder, water, stone powder, 20mm aggregate and 10mm aggregate;

[0010] The cement and mineral powder are used as cementing materials, and the amount of cementing materials used is less than 500 kg / m³. 3 The proportion of cement in the mass of cementitious materials shall not exceed 30%, and the proportion of mineral powder in the mass of cementitious materials shall not be less than 70%.

[0011] Furthermore, the concrete components, by mass proportion, include: 120-150 kg / m³ of cement. 3 Mineral powder 320-350kg / m³ 3 Water 140-180kg / m 3 Stone powder 700-800 kg / m³ 3 20mm gravel weighs 600-700 kg / m³ 3 10mm gravel 260-300kg / m 3 .

[0012] Furthermore, the concrete components, by mass proportion, include: 144 kg / m³ of cement. 3 Mineral powder 336kg / m 3 Water 160kg / m 3 Stone powder 750kg / m 3 20mm gravel 665kg / m 3 10mm gravel 285kg / m 3 .

[0013] Furthermore, it also includes composite nano-based additives;

[0014] The composite nano-based additive comprises the following raw materials in parts by weight: 50-70 parts of polycarboxylate superplasticizer; 38 parts of water control agent; 5-15 parts of mortar conditioner; 0.1-3 parts of anti-blocking agent; 5-20 parts of super slump preventer; 5-20 parts of strength enhancer; and 3-15 parts of slow-release agent.

[0015] Furthermore, the composite nano-based admixture can inhibit and prolong the cement hydration time, so that the initial slump of the concrete is 230mm, and the slump still remains at 225-230mm after standing for 2 hours at 27℃±3℃.

[0016] Furthermore, the 14-day compressive strength of the concrete is 71.5-71.8 MPa, which meets the strength grade requirements of C60 concrete.

[0017] Furthermore, the mineral powder is an industrial by-product mineral powder with a specific surface area of ​​400-450 m². 2 / kg, activity index (7 days) ≥75%, activity index (28 days) ≥95%.

[0018] A method for preparing C60 commercial concrete with ultra-low cement content, characterized by comprising the following steps:

[0019] (1) Raw material pretreatment: Cement, mineral powder, stone powder, 20mm gravel and 10mm gravel are dried separately to control the moisture content ≤0.5%;

[0020] (2) Mixing: First, put stone powder, 20mm gravel and 10mm gravel into the mixer and dry mix for 30-60 seconds; then add cement and mineral powder and continue to dry mix for 60-90 seconds; then add 70% water and wet mix for 90-120 seconds; finally add composite nano-based admixture and the remaining 30% water and mix for 120-180 seconds to obtain a uniform concrete mixture;

[0021] (3) Finished product inspection: The slump of the mixed concrete is tested, and the initial slump must reach 230mm; after the concrete is left to stand for 2 hours at 27℃±3℃, the slump is tested again and must be maintained at 225-230mm; at the same time, concrete test blocks are made, and after standard curing for 14 days, the compressive strength must reach 71.5MPa or above.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. Revolutionizing the traditional design concept of high-strength concrete: This invention is the first to achieve a cement content of only 30% in C60 commercial concrete, breaking the traditional understanding that "high-strength concrete requires high cement content" and proving that cement content is not the determining factor of concrete strength, providing a new path for the low-carbon design of high-strength concrete.

[0024] 2. Significantly reduced carbon emissions: The amount of cement used per cubic meter of concrete is only 144 kg, which is about 220 kg less than that of traditional C60 concrete, resulting in a reduction of tens of thousands of tons of CO2 emissions.

[0025] 3. Effectively inhibits concrete cracks: By replacing part of the cement with mineral powder and combining it with composite nano-based admixtures to inhibit the cement hydration rate, the peak hydration heat of concrete is reduced by 25-30%, which greatly reduces temperature stress, reduces the generation of cracks from the root, and improves the durability and service life of buildings.

[0026] 4. Excellent workability: The initial slump of the concrete reaches 230mm, and after 2 hours of transportation at 27℃±3℃, the slump still remains at 225-230mm, with no segregation or bleeding. This meets the construction requirements for long-distance transportation and on-site pouring of commercial concrete, improving construction efficiency and project quality.

[0027] 5. Resource recycling: The extensive use of industrial by-product mineral powder replaces valuable cement resources, realizing the resource utilization of industrial waste, reducing concrete production costs, and reducing environmental pollution caused by industrial waste accumulation, which is in line with the concept of circular economy development.

[0028] 6. Meets national strategic requirements: The product of this invention has the advantages of high strength, low emissions, and high durability, which fully meets the requirements of my country's "high-quality development" and "low-carbon emission reduction". It has broad application prospects and can be widely used in various large-scale projects such as bridges, tunnels, high-rise buildings, and industrial plants. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] A C60 commercial concrete with ultra-low cement content has the following component mass ratio: cement 144 kg / m³ 3 336 kg / m³ of mineral powder 3 160kg / m³ of water 3 750kg / m³ of stone powder 3 20mm gravel 665kg / m 3 10mm gravel 285kg / m 3 Composite nano-based admixture 7kg / m 3 (Admixture mass fraction is 10%).

[0033] 1. Optimization of cementitious material system

[0034] The core innovation of this invention lies in the proportioning design of the cementitious material: the cementitious material is composed of cement and industrial by-product mineral powder, with a total amount of only 480 kg / m³. 3 (below 500 kg / m 3 (At the industry standard level), of which cement accounts for 30% and mineral powder accounts for 70%. The recycling of mineral powder as industrial waste not only reduces the amount of cement used, but its active ingredients can also undergo a secondary hydration reaction with cement hydration products to generate more hydrated calcium silicate gel, which fills the internal pores of concrete and improves the density and strength of the structure.

[0035] 2. Application of composite nano-based admixtures

[0036] This invention uses a composite nano-based admixture (the admixture is existing technology, see CN115819010A, name: a special admixture for commercial concrete with all recycled aggregate), whose main components include 60 parts of polycarboxylate superplasticizer; 5 parts of water control agent; 10 parts of slurry conditioner; 2 parts of anti-sticking agent; 10 parts of super slump retention agent; 8 parts of strength growth agent; and 5 parts of slow-release agent.

[0037] The admixture has three core functions: first, it effectively reduces water content, controlling the water consumption to 160 kg / m³ while ensuring the fluidity of the concrete. 3 The benefits include: 1) reducing the water-cement ratio to 0.33; 2) inhibiting the cement hydration rate, extending the time of peak hydration heat release, reducing hydration heat accumulation, and preventing temperature cracks at the source; and 3) improving concrete workability, effectively inhibiting slump loss, and ensuring that concrete retains good pouring performance after long-distance transportation.

[0038] 3. Aggregate gradation design

[0039] The three-stage aggregate gradation of "stone powder + 20mm gravel + 10mm gravel" is adopted. The fineness modulus of stone powder is 2.6-3.0, which plays the role of filling the voids in the skeleton. The 20mm gravel and 10mm gravel are mixed in a ratio of 665:285 to form a dense aggregate stacking structure, which reduces the amount of cementitious materials and improves the compressive strength and durability of concrete.

[0040] III. Preparation Method

[0041] 1. Raw material pretreatment: Cement and mineral powder are stored in a moisture-proof manner to prevent moisture absorption and clumping; stone powder, 20mm gravel, and 10mm gravel are dried in a dryer to control the moisture content to ≤0.5% to prevent excess moisture in the aggregate from affecting the water-cement ratio of concrete.

[0042] 2. Mixing and Stirring: A forced concrete mixer is used, and the mixing sequence is "dry mixing of aggregates → dry mixing of cementitious materials → wet mixing with water → mixing with admixtures". Specific steps: ① Add stone powder, 20mm gravel, and 10mm gravel, and dry mix for 30-60 seconds to ensure the aggregates are evenly mixed; ② Add cement and mineral powder, and continue dry mixing for 60-90 seconds to ensure the cementitious materials are in full contact with the aggregates; ③ Add 70% water and wet mix for 90-120 seconds to form a preliminary concrete mixture; ④ Add the composite nano-based admixture and the remaining 30% water, and stir for 120-180 seconds to ensure the admixture is evenly dispersed, ultimately obtaining a uniformly colored, lump-free, and highly fluid concrete product.

[0043] 3. Finished Product Inspection and Transportation: Immediately after mixing, conduct an initial slump test, requiring an initial slump ≥ 230 mm; use concrete mixer trucks for transportation, controlling the transportation time within 2 hours, and maintaining the mixing drum at a low speed (2-4 r / min) during transportation; after arriving at the construction site, test the slump again, which must be maintained at 225-230 mm, and at the same time make standard test blocks for strength testing.

[0044] Example 1

[0045] At the construction site of the "Hong Kong Central Kowloon Trunk Line": C60 commercial concrete with ultra-low cement content was prepared according to the above technical solution. The dosage of each component is as follows: cement 144kg, mineral powder 336kg, water 160kg, stone powder 750kg, 20mm gravel 665kg, 10mm gravel 285kg, and composite nano-based admixture 7kg (mass fraction 10%). The actual slump measured from concrete production to the construction site (more than 2 hours) is maintained at 225mm-230mm; the 14-day strength is 71.5-71.8.

[0046] Performance testing

[0047] 1. Slump test: The initial slump test value was 230mm at 27℃. After the concrete was placed in a constant temperature and humidity environment (27℃±3℃, humidity 60%±5%) for 2 hours, the slump test value was still 230mm, and the slump loss was 0, which shows that the concrete has excellent workability retention ability and meets the requirements of long-distance transportation and on-site construction.

[0048] 2. Strength test: Concrete standard test blocks of 150mm×150mm×150mm were made and cured for 14 days under standard curing conditions (temperature 20℃±2℃, relative humidity ≥95%). The compressive strength was tested using a pressure testing machine. The test result was 71.8MPa, which far exceeds the standard requirement of ≥50MPa for C60 concrete after 14 days.

[0049] 3. Durability test: The concrete test blocks were subjected to a permeability test, with a penetration height ratio of ≤30%; the freeze-thaw resistance test (rapid freezing method) showed that after 200 freeze-thaw cycles, the mass loss rate was ≤5% and the strength loss rate was ≤20%, indicating that the concrete has good permeability resistance, freeze-thaw resistance and excellent durability.

[0050] 4. Heat of hydration test: The heat of hydration of concrete was tested using an adiabatic temperature rise meter. The peak heat of hydration was 45℃, which is about 25-30% lower than that of traditional C60 concrete (peak heat of hydration 65-70℃), effectively avoiding the generation of temperature cracks.

[0051] Comparative test

[0052] A control group (traditional C60 commercial concrete) was set up, with a total cementitious material content of 560 kg / m³. 3 The composition includes 65% cement (364 kg), 35% mineral powder (196 kg), 175 kg water, 8 kg admixtures, and the amounts of other aggregates are consistent with those of this invention. Test results are as follows:

[0053] Table 1 Test Results

[0054] project Embodiment 1 of the present invention control group <![CDATA[Cement consumption (kg / m 3 )]]> 144 364 <![CDATA[Total amount of cementitious materials (kg / m 3 )]]> 480 560 Initial slump (mm) 230 220 2-hour slump (mm) 230 180 14-day compressive strength (MPa) 71.8 68.5 Peak heat of hydration (°C) 45 68 Carbon emissions per cubic meter (kg) 183 452

[0055] The comparative data shows that the cement content of the concrete of this invention is only 39.5% of that of the control group, and the carbon emissions are reduced by 61.7%. At the same time, it is superior to traditional C60 concrete in terms of slump retention, strength and heat of hydration control, showing significant technical advantages.

[0056] Example 2: Cube compressive strength test

[0057] The C60 commercial concrete prepared by the method of this invention was tested, and the results are as follows:

[0058] Test Description: Cube compressive strength;

[0059] Test methods: 1. Compressive strength: CS1:2010 Section 12;

[0060] 2. Density; CS1: 2010, Section 16;

[0061] 3. Curing: CS1:2010, Section 10;

[0062] Laboratory test results:

[0063] Date of receipt: December 28, 2023;

[0064] Test date: January 10, 2024; Age: 14 days;

[0065] Laboratory curing method; atomization curing at 27℃±3℃;

[0066] Table 2 Test Results

[0067]

[0068] Example 3: Report on Concrete Sampling, Slump Measurement, and Specimen Preparation

[0069] Test date: December 29, 2023;

[0070] Concrete grade: 60 / 20D 70% GGBS;

[0071] Design slump: 200mm (range 150-250mm);

[0072] Sampling location: On-site;

[0073] Cube sampling frequency: per m 3 One data collection;

[0074] Table 3 Test Results

[0075]

[0076] In summary, this invention achieves the dual goals of resource recycling and low-carbon emission reduction, overturning the traditional perception that high-grade concrete relies on high cement usage. The preparation process is simple and controllable, the production cost is reasonable, and it is suitable for various large-scale projects such as bridges, tunnels, and high-rise buildings, with broad prospects for promotion and application.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A C60 commercial concrete with ultra-low cement content, characterized in that: The ready-mixed concrete comprises the following components: cement, mineral powder, water, stone powder, 20mm aggregate, and 10mm aggregate; The cement and mineral powder are used as cementing materials, and the amount of cementing materials used is less than 500 kg / m³. 3 The proportion of cement in the mass of cementitious materials shall not exceed 30%, and the proportion of mineral powder in the mass of cementitious materials shall not be less than 70%.

2. The C60 commercial concrete with ultra-low cement content according to claim 1, characterized in that, The concrete components, by mass proportion, include: cement 120-150 kg / m³ 3 Mineral powder 320-350kg / m³ 3 Water 140-180kg / m 3 Stone powder 700-800 kg / m³ 3 20mm gravel weighs 600-700 kg / m³ 3 10mm gravel 260-300kg / m 3 .

3. The C60 commercial concrete with ultra-low cement content according to claim 1, characterized in that, The concrete components, by mass proportion, include: 144 kg / m³ of cement. 3 Mineral powder 336kg / m 3 Water 160kg / m 3 Stone powder 750kg / m 3 20mm gravel 665kg / m 3 10mm gravel 285kg / m 3 .

4. The C60 commercial concrete with ultra-low cement content according to claim 1, characterized in that, It also includes composite nano-based additives; The composite nano-based additive comprises the following raw materials in parts by weight: 50-70 parts of polycarboxylate superplasticizer; 38 parts of water control agent; 5-15 parts of mortar conditioner; 0.1-3 parts of anti-blocking agent; 5-20 parts of super slump preventer; 5-20 parts of strength enhancer; and 3-15 parts of slow-release agent.

5. The C60 commercial concrete with ultra-low cement content according to claim 4, characterized in that, The composite nano-based admixture can inhibit and prolong the cement hydration time, so that the initial slump of the concrete is 230mm, and the slump still remains at 225-230mm after standing for 2 hours at 27℃±3℃.

6. The C60 commercial concrete with ultra-low cement content according to claim 1, characterized in that, The 14-day compressive strength of the concrete is 71.5-71.8 MPa, which meets the strength grade requirements of C60 concrete.

7. The C60 commercial concrete with ultra-low cement content according to claim 1, characterized in that, The mineral powder mentioned is an industrial by-product with a specific surface area of ​​400-450 m². 2 / kg, activity index (7 days) ≥75%, activity index (28 days) ≥95%.

8. A method for preparing C60 commercial concrete with ultra-low cement content as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Raw material pretreatment: Cement, mineral powder, stone powder, 20mm gravel and 10mm gravel are dried separately to control the moisture content ≤0.5%; (2) Mixing: First, put stone powder, 20mm gravel and 10mm gravel into the mixer and dry mix for 30-60 seconds; then add cement and mineral powder and continue to dry mix for 60-90 seconds; then add 70% water and wet mix for 90-120 seconds; finally add composite nano-based admixture and the remaining 30% water and mix for 120-180 seconds to obtain a uniform concrete mixture; (3) Finished product inspection: The slump of the mixed concrete is tested, and the initial slump must reach 230mm; after the concrete is left to stand for 2 hours at 27℃±3℃, the slump is tested again and must be maintained at 225-230mm; at the same time, concrete test blocks are made, and after standard curing for 14 days, the compressive strength must reach 71.5MPa or above.

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