A method for introducing air into concrete closed-cell microfoam bubbles
By using a combination of AES and AOS surfactants and materials such as carboxymethyl cellulose in concrete, closed-cell microbubbles are formed, which solves the problem of poor bubble stability in concrete and improves the durability and workability of concrete.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LANZHOU RESOURCES & ENVIRONMENT VOC TECH COLLEGE
- Filing Date
- 2024-05-13
- Publication Date
- 2026-07-21
AI Technical Summary
When high-quality micro-bubbles are introduced into existing concrete, there are problems such as poor bubble stability, easy floating and cross-contamination, resulting in quality problems such as honeycomb surface and through cracks, and the amount of air entrainment is difficult to control.
A combination of air-entraining agents and plasticizing foam stabilizers is used, specifically a mixture of AES and AOS surfactants with materials such as carboxymethyl cellulose. Through stirring, uniformly distributed closed-cell microbubbles are formed, which enhances the workability and fluidity of concrete.
It achieves controllable bubble morphology and air entrainment, improves the durability properties of concrete such as impermeability and freeze-thaw resistance, solves the problems of bubble floating and cross-contamination, and improves the workability of concrete and the quality of hardened body.
Smart Images
Figure CN118439885B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of concrete preparation technology, and in particular to a method for entraining air in closed-cell microbubbles in concrete. Background Technology
[0002] Concrete is one of the most important engineering materials, and with the rapid development of concrete technology, the quality of concrete materials has been continuously improved. Closed-cell microbubbles can improve the workability and fluidity of concrete, reduce non-measurable indicators such as bleeding, settlement, and segregation, and are a major technical measure to cut off inherent defects such as capillary channels in concrete and improve its durability properties such as crack resistance, impermeability, and freeze-thaw resistance. Therefore, air-entraining technology is one of the important technical approaches to improve concrete quality. Currently, there are explicit requirements for the use of air-entraining agents in the design codes for pumped concrete, hydraulic and port engineering concrete, and nuclear engineering concrete.
[0003] Introducing high-quality microbubbles into concrete under suitable workability conditions is not particularly difficult. The key issue lies in the widespread use of polycarboxylate superplasticizers in concrete, leading to significant fluctuations in the concrete's plasticity and frequent segregation or slump. Severe slump results in a substantial decrease in air entrainment, failing to meet design requirements. Segregation easily leads to excessive bubble formation, but these bubbles are unstable, easily migrating and floating, forming large bubbles that cause serious quality problems in the hardened concrete, such as honeycomb-like surface defects, through cracks, and strength loss. Therefore, achieving high-quality air entrainment in concrete depends not only on the dosage of the air-entraining agent but also on factors such as the plasticity of the concrete. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a method for entraining air into closed-cell microbubbles in concrete with controllable air entrainment volume and bubble morphology.
[0005] To address the aforementioned problems, the present invention provides a method for entraining air in closed-cell microbubbles in concrete, characterized in that: the method involves adding 0.5-1 kg of air-entraining agent and 0.5-1 kg of concrete plasticizer and foam stabilizer per cubic meter of concrete during concrete preparation; the air-entraining agent is made from surfactant AES (sodium fatty alcohol polyoxyethylene ether sulfate), surfactant AOS (sodium α-olefin sulfonate), and water; the concrete plasticizer and foam stabilizer is made from carboxymethyl cellulose, redispersible soluble latex powder, polyacrylamide, and mineral powder.
[0006] The air-entraining agent is prepared by mixing 15-20 parts of surfactant AES, 20-25 parts of surfactant AOS, and 60 parts of water by weight, stirring until completely dissolved, and then allowing it to stand at room temperature for 20-24 hours.
[0007] The concrete plasticizer and foam stabilizer is prepared by grinding and mixing 8-10 parts of carboxymethyl cellulose, 14-16 parts of redispersible soluble latex powder, 14-16 parts of polyacrylamide and 60 parts of mineral powder in a small ball mill for 30-40 minutes by weight.
[0008] A closed-cell microbubble air-entrained concrete prepared using the above method.
[0009] The closed-cell microbubble air-entrained concrete described above is characterized by the following steps: after adding aggregate, sand, cement, fly ash and polycarboxylate superplasticizer to a concrete mixer, a concrete plasticizer and foam stabilizer is added first, followed by an air-entraining agent, and then water is added and stirred for 150 to 180 seconds to obtain the concrete.
[0010] Compared with the prior art, the present invention has the following advantages: 1. This invention uses both concrete air-entraining agent and concrete plasticizer and foam stabilizer, which can reduce the degree of concrete slump or segregation, keep the concrete in a good plastic state for a long time, eliminate the influence of state factors, and make the air entrainment amount and bubble morphology controllable.
[0011] 2. This invention adds a concrete plasticizer and foam stabilizer during concrete production, improving the workability and fluidity of the concrete and giving it a good plastic working state. Under these conditions, due to the active effect of the air-entraining agent, abundant, uniformly sized, and evenly distributed microbubbles are formed during concrete mixing, improving the air-entraining efficiency of the agent. Simultaneously, the plasticizer and foam stabilizer gives the concrete a good cohesive plastic state, preventing the microbubbles from floating or interconnecting, and ensuring they are evenly distributed throughout the concrete. This solves the technical problems of poor bubble stability, easy floating, interconnection, and rupture, as well as serious quality problems such as honeycomb surface defects, through cracks, and strength loss in hardened concrete.
[0012] 3. The air-entraining agent of this invention combines AES (sodium fatty alcohol polyoxyethylene ether sulfate) and the surfactant AOS (sodium α-olefin sulfonate). AES possesses some characteristics of both nonionic and anionic surfactants, exhibiting significant resistance to hard water and being suitable for surface activity in alkaline cement environments. AOS more readily introduces microbubbles during stirring; the combined use of both results in abundant foam, primarily composed of microbubbles.
[0013] 4. Using the method of this invention, an appropriate amount of uniformly distributed closed-cell microbubbles with a pore size range of 200-800 μm can be introduced into the concrete mixing process. An appropriate amount of micro- and nano-bubbles can improve the workability and fluidity of concrete.
[0014] 5. The air-entraining method described in this invention can fill and block the pores in concrete, thereby cutting off the connection of capillary channels, reducing the through-pore defects inside the concrete, and effectively improving the durability properties of concrete such as impermeability, frost resistance and salt ion erosion resistance.
[0015] 6. The method of the present invention is simple to use, has low quality risk, and has broad application prospects. Attached Figure Description
[0016] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
[0017] Figure 1 This is a scanning electron microscope image of a hardened concrete sample from the present invention. Detailed Implementation
[0018] A method for entraining air in closed-cell microbubbles in concrete involves adding 0.5-1 kg of an air-entraining agent and 0.5-1 kg of a concrete plasticizer and foam stabilizer per cubic meter of concrete during preparation. The air-entraining agent is made from surfactants AES (sodium fatty alcohol polyoxyethylene ether sulfate), AOS (sodium α-olefin sulfonate), and water; the concrete plasticizer and foam stabilizer is made from carboxymethyl cellulose, redispersible soluble latex powder, polyacrylamide, and mineral powder.
[0019] Among them, the air-entraining agent is made by mixing 15-20 parts of surfactant AES, 20-25 parts of surfactant AOS (sodium α-olefin sulfonate) and 60 parts of water by weight (kg), stirring evenly, and allowing it to stand at room temperature for 20-24 hours after complete dissolution.
[0020] Concrete plasticizer and foam stabilizer is made by grinding and mixing 8-10 parts of carboxymethyl cellulose, 14-16 parts of redispersible soluble latex powder, 14-16 parts of polyacrylamide and 60 parts of mineral powder in a small ball mill for 30-40 minutes, based on weight (kg).
[0021] A closed-cell microbubble air-entrained concrete prepared by the above method: After adding gravel, sand, cement, fly ash and polycarboxylate superplasticizer to a concrete mixer, first add concrete plasticizer and foam stabilizer, then add air-entraining agent, and then add water and stir for 150 to 180 seconds to obtain the concrete.
[0022] Raw materials and testing methods in this invention: Raw materials used in the experiment Surfactants AES, AOS, carboxymethyl cellulose, redispersible soluble latex powder, and polyacrylamide are all commercially available products.
[0023] The gravel, sand, P·O42.5 grade cement, fly ash, mineral powder, and polycarboxylate superplasticizer were all purchased from the market and all met the relevant national standards.
[0024] Cement: P·O42.5 grade ordinary Portland cement; Aggregate: Construction crushed stone, meeting the technical requirements specified in GB / T 14685-2011 "Construction Gravel and Crushed Stone", with a nominal particle size of 5~40mm; Sand: Meeting the medium sand requirements specified in GB / T 14684-2011 "Construction Sand", with a fineness modulus of 3.1; Fly ash: Technical indicators meeting the Class III requirements specified in GB / T 1596-2017 "Fly Ash Used in Cement and Concrete".
[0025]
Experimental Methods
[0026] Concrete tests were conducted according to the test methods specified in GB / T 8076-2008 "Concrete Admixtures". Concrete mix proportions: cement: 380 kg, aggregate: 980 kg, sand: 880 kg, fly ash: 50 kg, water: 175 kg, polycarboxylate superplasticizer dosage: 7.6 kg.
[0027] Example 1 Concrete mix proportions: cement: 380kg, aggregate: 980kg, sand: 880kg, fly ash: 50kg, water: 175kg, polycarboxylate superplasticizer dosage: 7.6kg, air-entraining agent: 0.5kg, concrete plasticizer and foam stabilizer: 0.5kg.
[0028] Example 2 Concrete mix proportions: cement: 380kg, aggregate: 980kg, sand: 880kg, fly ash: 50kg, water: 175kg, polycarboxylate superplasticizer dosage: 7.6kg, air-entraining agent: 0.5kg, concrete plasticizer and foam stabilizer: 1.0kg.
[0029] Example 3 Concrete mix proportions: cement: 380kg, aggregate: 980kg, sand: 880kg, fly ash: 50kg, water: 175kg, polycarboxylate superplasticizer dosage: 7.6kg, air-entraining agent: 1.0kg, concrete plasticizer and foam stabilizer: 0.5kg.
[0030] Example 4 Concrete mix proportions: Cement: 380kg, Aggregate: 980kg, Sand: 880kg, Fly ash: 50kg, Water: 175kg, Polycarboxylate superplasticizer dosage: 7.6kg, Air-entraining agent: 1.0kg, Concrete plasticizer and foam stabilizer: 1.0kg.
[0031] The concrete prepared using the method of the present invention in Examples 1 to 4 was tested according to GB / T 8076-2008 "Concrete Admixtures", and the test results are shown in Table 1.
[0032] Table 1: Test Results of Concrete Technical Indicators As shown in Table 1, the air content of concrete steadily increases with the increase of the dosage of air-entraining agent and concrete plasticizer / foam stabilizer. This indicates that the air-entraining method, due to the effect of the concrete plasticizer / foam stabilizer, can stably introduce an appropriate amount of micro-bubbles into the concrete, facilitating production control. This solves the problem in engineering production where a single air-entraining agent is affected by changes in material viscosity, resulting in inconsistent foam volume. Furthermore, it addresses the poor foam stability of highly fluid concrete, the tendency of bubbles to float and connect after concrete pouring, leading to uneven distribution of concrete binder, aggregate, and bubbles in three dimensions, and honeycomb-like pitting on the concrete surface.
[0033] As can be seen from the changes in concrete strength in Table 1, when the strength can increase or decrease steadily with the air content, it indicates that the size and distribution of the air bubbles are uniform and stable. The foam quality obtained by using this method is good, which is convenient for the strength design of concrete with a specific air content.
[0034] Figure 1 This refers to the microstructure of air-entrained concrete. (The text abruptly ends here.) Figure 1 As can be seen, the concrete cross-section has no through-voids, the surface is not smooth, and there is no honeycomb or pitting. The air bubbles in the concrete are uniformly distributed and of consistent size, with microbubbles ranging from approximately 200-800 μm in diameter. An appropriate amount of micro- and nano-bubbles can improve the workability and fluidity of concrete, and can also fill and block pores in the concrete, cutting off capillary channels and reducing through-voids within the concrete, thereby effectively improving the concrete's impermeability, freeze-thaw resistance, and resistance to salt ion attack.
Claims
1. A method for entraining air from microbubbles in closed-cell concrete, characterized in that: The method refers to a concrete mix proportion of: 380 kg cement, 980 kg aggregate, 880 kg sand, 50 kg fly ash, 175 kg water, 7.6 kg polycarboxylate superplasticizer, 0.5 kg air-entraining agent, and 0.5 kg concrete plasticizer and foam stabilizer; and the concrete contains uniformly distributed air bubbles of consistent size, with micro-bubble diameters ranging from 200 to 800 μm. The air-entraining agent is composed of 15-20 parts by weight of surfactant AES, 20-25 parts by weight of surfactant AOS, and 60 parts by weight of water. The concrete plasticizer and foam stabilizer is prepared by grinding and mixing 8-10 parts by weight of carboxymethyl cellulose, 14-16 parts by weight of redispersible soluble latex powder, 14-16 parts by weight of polyacrylamide, and 60 parts by weight of mineral powder in a small ball mill for 30-40 minutes.
2. A closed-cell microbubble air-entrained concrete prepared by the method described in claim 1.
3. The closed-cell microbubble air-entrained concrete as described in claim 2, characterized in that: After adding gravel, sand, cement, fly ash, and polycarboxylate superplasticizer to a concrete mixer, first add concrete plasticizer and foam stabilizer, then add air-entraining agent, and finally add water and mix for 150 to 180 seconds to obtain the final product.