Premixed concrete with concrete admixture and preparation method thereof

Abstract

The invention provides premixed concrete with a concrete admixture and a preparation method thereof, and belongs to the technical field of concrete, the premixed concrete comprises cement, fly ash, sand, gravel and a composite admixture; according to the weight of each cubic meter, the concrete comprises 300-350 kg / m < 3 > of cement, 80-100 kg / m < 3 > of fly ash, 700-750 kg / m < 3 > of sand, 1000-1100 kg / m < 3 > of gravel, 9.5-15.75 kg / m < 3 > of a composite admixture and 150-160 kg / m < 3 > of water. According to the invention, the composite admixture is added into the premixed concrete to improve the matching property with the cementing materials (cement and fly ash), so that the slump loss is reduced in the production and transportation process of the premixed concrete, the transportation efficiency of the concrete is greatly improved, the cost is saved, and the construction benefit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and particularly relates to a ready-mixed concrete with a concrete admixture and a preparation method thereof. Background Art

[0002] Concrete generally refers to an engineering composite material in which aggregate is cemented into a whole by a cementitious material. Usually, the term "concrete" refers to cement concrete, which uses cement as the cementitious material, sand and stone as aggregates; it is mixed with water in a certain proportion and obtained by stirring. It is also called ordinary concrete and is widely used in civil engineering. Ready-mixed concrete refers to a concrete mixture that is composed of cement, aggregate, water, and additives and mineral admixtures incorporated as required in certain proportions, measured and mixed in a mixing station, sold, and transported to the use location by a transport vehicle within a specified time. As the main building material in the construction industry, ready-mixed concrete has the characteristics of convenient construction, low price, convenient material collection, safety and environmental protection.

[0003] During the production and transportation of existing ready-mixed concrete, due to reasons such as long distances, congestion, or high temperatures, the slump loss of ready-mixed concrete is too large, not meeting the requirements of transportation and waiting. Therefore, a ready-mixed concrete with a concrete admixture and a preparation method thereof are needed. Summary of the Invention

[0004] The purpose of the present invention is to provide a ready-mixed concrete with a concrete admixture and a preparation method thereof, so as to solve the technical problem of excessive slump loss of existing ready-mixed concrete.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A ready-mixed concrete with a concrete admixture, the ready-mixed concrete comprising cement, fly ash, sand, gravel, and a composite admixture;

[0007] By weight per cubic meter,

[0008] cement 300 - 350 kg / m 3 、fly ash 80 - 100 kg / m 3 、sand 700 - 750 kg / m 3 、gravel 1000 - 1100 kg / m 3 、composite admixture 9.5 - 15.75 kg / m 3 water and 150 - 160 kg / m 3 .

[0009] Further, the cement is P·O 42.5 cement.

[0010] Further, the sand is medium sand with a fineness modulus of 2.6 - 3.0.

[0011] Further, the particle size of the crushed stone is 5 - 25 mm.

[0012] Further, the composite admixture accounts for 2.5 - 3.5% of the total weight of cement and fly ash.

[0013] Further, the composite admixture comprises components in the following mass percentages:

[0014] 40 - 50% of polycarboxylate water - reducing agent, 10 - 15% of sodium gluconate retarder, 5 - 10% of nano - silica, 3 - 5% of calcium lignosulfonate air - entraining agent, 2 - 4% of hydroxypropyl methylcellulose, 8 - 12% of calcium sulfoaluminate expansive agent, and the balance is water.

[0015] Further, the preparation method of the composite admixture comprises the following steps:

[0016] a. Mix the polycarboxylate water - reducing agent and the sodium gluconate retarder and stir evenly;

[0017] b. Sequentially add nano - silica and calcium lignosulfonate air - entraining agent, and continue to stir until uniform;

[0018] c. Add hydroxypropyl methylcellulose and calcium sulfoaluminate expansive agent, control the pH value at 6.5 - 7.5, and finally add water to adjust the viscosity to 500 - 800 mPa·s.

[0019] Further, in step a, the stirring temperature is 60°C; the stirring time is 30 min.

[0020] Further, in step b, the nano - silica is the nano - silica after ultrasonic dispersion treatment.

[0021] A preparation method of ready - mixed concrete with a concrete admixture comprises the following steps:

[0022] A. Dry - mix cement, fly ash, sand, and crushed stone evenly for 1 - 2 minutes;

[0023] B. Add water and the composite admixture, and wet - mix for 3 - 5 minutes until the slump reaches 180 - 220 mm;

[0024] C. Detect the uniformity before discharging, and then package or directly pump for construction.

[0025] Due to the adoption of the above - mentioned technical solution, the present invention has the following beneficial effects:

[0026] 1. In the present invention, a composite admixture is added to ready-mixed concrete. The polycarboxylate water reducer and sodium gluconate in the composite admixture synergistically extend the cement hydration induction period and reduce the slump loss; the nano-silica in the composite admixture fills the micro-pores with nano-particles, and the expansive agent compensates for shrinkage, jointly improving the impermeability; the calcium lignosulfonate in the composite admixture introduces uniform air bubbles (air content 4 - 5%), and hydroxypropyl methylcellulose prevents the air bubbles from escaping, synergistically improving the frost resistance; through the synergistic effect of each component in the composite admixture, the functions of water reduction, setting retardation, crack resistance, and frost resistance are achieved simultaneously.

[0027] 2. In the present invention, by adding a composite admixture, the compatibility with cementitious materials (cement and fly ash) is improved, the production cost is reduced, and the construction efficiency is increased.

[0028] 3. The preparation method of the ready-mixed concrete provided by the present invention can solve the safety problem of transporting flowing concrete, greatly improve the concrete transportation efficiency, save costs, and improve the construction benefits. Specific Embodiments

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the following preferred embodiments are given to further elaborate the present invention in detail. However, it should be noted that many details listed in the specification are only for enabling the reader to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be realized even without these specific details.

[0030] A ready-mixed concrete with a concrete admixture, the ready-mixed concrete includes cement, fly ash, sand, gravel, and a composite admixture; calculated by weight per cubic meter, cement (P·O 42.5) 300 - 350 kg / m 3 、fly ash 80 - 100 kg / m 3 、sand (medium sand, fineness modulus 2.6 - 3.0) 700 - 750 kg / m 3 、gravel (particle size 5 - 25 mm) 1000 - 1100 kg / m 3 、composite admixture (accounting for 2.5 - 3.5% of the total weight of cement and fly ash) 9.5 - 15.75 kg / m 3 water and 150 - 160 kg / m 3 .

[0031] The composite admixture includes the following components by mass percentage: polycarboxylate water reducer 40 - 50%, sodium gluconate setting retarder 10 - 15%, nano-silica 5 - 10% (particle size 30 nm), calcium lignosulfonate air-entraining agent 3 - 5%, hydroxypropyl methylcellulose 2 - 4%, calcium sulfoaluminate expansive agent 8 - 12%, and the balance is water.

[0032] The preparation method of the composite admixture includes the following steps:

[0033] a. Mix the polycarboxylate water reducer and the sodium gluconate retarder and stir for 30 min at 60 °C until uniform.

[0034] b. Add the nano-silica and the lignosulfonate air-entraining agent after ultrasonic dispersion treatment in sequence and continue to stir until uniform.

[0035] C. Add hydroxypropyl methylcellulose and calcium sulfoaluminate expansive agent, control the pH value at 6.5 - 7.5, and finally add water to adjust the viscosity to 500 - 800 mPa·s.

[0036] A preparation method of ready-mixed concrete with concrete admixtures, comprising the following steps:

[0037] A. Dry-mix 300 kg of cement, 80 kg of fly ash, 700 kg of sand and 1000 kg of gravel evenly for 1 - 2 minutes.

[0038] B. Add water and a composite admixture, and wet-mix for 3 - 5 minutes until the slump reaches 180 - 220 mm.

[0039] C. Detect the uniformity before discharging, and then package or directly pump for construction.

[0040] Example 1

[0041] Dry-mix 300 kg of cement, 80 kg of fly ash, 700 kg of sand and 1000 kg of gravel evenly for 1 - 2 minutes; add 150 kg of water, and the composite admixture is 2.5% of the total weight of cement and fly ash, then wet-mix for 3 - 5 minutes until the slump reaches 180 - 220 mm; detect the uniformity before discharging, and then package or directly pump for construction.

[0042] Example 2

[0043] Dry-mix 320 kg of cement, 90 kg of fly ash, 720 kg of sand and 1050 kg of gravel evenly for 1 - 2 minutes; add 155 kg of water, and the composite admixture is 3.0% of the total weight of cement and fly ash, then wet-mix for 3 - 5 minutes until the slump reaches 180 - 220 mm; detect the uniformity before discharging, and then package or directly pump for construction.

[0044] Example 3

[0045] Dry-mix 350 kg of cement, 100 kg of fly ash, 750 kg of sand and 1100 kg of gravel evenly for 1 - 2 minutes; add 160 kg of water, and the composite admixture is 3.5% of the total weight of cement and fly ash, then wet-mix for 3 - 5 minutes until the slump reaches 180 - 220 mm; detect the uniformity before discharging, and then package or directly pump for construction.

[0046] Comparative Example 1

[0047] Dry-mix 320 kg of cement, 90 kg of fly ash, 720 kg of sand and 1050 kg of crushed stone evenly for 1 - 2 minutes; add 155 kg of water, and the compound admixture (without nano-silica) is 3.0% of the total weight of cement and fly ash, then wet-mix for 3 - 5 minutes until the slump reaches 180 - 220 mm; detect the uniformity before discharging, and then package or directly pump for construction.

[0048] Comparative Example 2

[0049] Dry-mix 320 kg of cement, 90 kg of fly ash, 720 kg of sand and 1050 kg of crushed stone evenly for 1 - 2 minutes; add 155 kg of water, and the traditional admixture is 3.0% of the total weight of cement and fly ash, then wet-mix for 3 - 5 minutes until the slump reaches 180 - 220 mm; detect the uniformity before discharging, and then package or directly pump for construction.

[0050] The performance test results are shown in Table 1

[0051] Table 1 Performance Test Results

[0052]

[0053] It can be known from the performance test result table that the slump loss of the ready-mixed concrete obtained in Examples 1 - 3 is small, while the slump loss of the ready-mixed concrete obtained in Comparative Examples 1 - 2 is large; after 28 days, the compressive strength of the ready-mixed concrete obtained in Examples 1 - 3 is greater than that of the ready-mixed concrete obtained in Comparative Examples 1 - 2, and the frost resistance performance is high.

[0054] Application Example

[0055] A certain northern bridge project uses the ready-mixed concrete obtained in Example 2 of the present invention, and the construction environment temperature is -5 to 10 °C. The measured performance is as follows:

[0056] The pumping time is 2 h, and the slump drops from 210 mm to 185 mm (loss rate 11.9%);

[0057] The strength of the core sample taken after 28 days reaches 61.2 MPa, and the relative dynamic elastic modulus is 92.3% after 300 freeze-thaw cycles.

[0058] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A ready-mixed concrete with a concrete admixture, characterized in that: The ready-mixed concrete includes cement, fly ash, sand, gravel, composite admixture and water; By weight per cubic meter, Cement 300 - 350 kg / m 3 , Fly ash 80 - 100 kg / m 3 , Sand 700 - 750 kg / m 3 , Crushed stone 1000 - 1100 kg / m 3 , Composite admixture 9.5 - 15.75 kg / m 3 and Water 150 - 160 kg / m 3 .

2. The ready-mixed concrete with a concrete admixture according to claim 1, characterized in that: the cement is P·O 42.5 cement.

3. The ready-mixed concrete with a concrete admixture according to claim 1, characterized in that: The sand is medium sand with a fineness modulus of 2.6 - 3.

0.

4. A ready-mixed concrete with a concrete admixture according to claim 1, characterized in that: The particle size of the gravel is 5 - 25 mm.

5. The ready-mixed concrete with a concrete admixture according to claim 1, characterized in that: The composite admixture accounts for 2.5 - 3.5% of the total weight of cement and fly ash.

6. The ready-mixed concrete with a concrete admixture according to claim 1, characterized in that: The composite admixture includes the following components by mass percentage: 40 - 50% of polycarboxylate water reducer, 10 - 15% of sodium gluconate retarder, 5 - 10% of nano-silica, 3 - 5% of calcium lignosulfonate air-entraining agent, 2 - 4% of hydroxypropyl methyl cellulose, 8 - 12% of calcium sulfoaluminate expansive agent, and the balance is water.

7. A ready-mixed concrete with a concrete admixture according to claim 6, characterized in that: The preparation method of the composite admixture includes the following steps: a. Mix the polycarboxylate water reducer and the sodium gluconate retarder and stir evenly; b. Add nano-silica and calcium lignosulfonate air-entraining agent in sequence and continue to stir until uniform; C. Add hydroxypropyl methyl cellulose and calcium sulfoaluminate expansive agent, control the pH value at 6.5 - 7.5, and finally add water to adjust the viscosity to 500 - 800 mPa·s.

8. A ready-mixed concrete with a concrete admixture according to claim 7, characterized in that: In step a, the stirring temperature is 60°C; the stirring time is 30 min.

9. The ready-mixed concrete with a concrete admixture according to claim 7, characterized in that: In step b, the nano-silica is the nano-silica after ultrasonic dispersion treatment.

10. The preparation method of ready-mixed concrete with concrete admixture according to any one of claims 1-9, characterized in that: It includes the following steps: A. Dry-mix the cement, fly ash, sand and gravel evenly for 1 - 2 minutes; B. Add water and the composite admixture and wet-mix for 3 - 5 minutes until the slump reaches 180 - 220 mm; C. After detecting the uniformity, the ready-mixed concrete can be discharged.

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