Carbonated reinforced coral aggregate and method of making same
By adjusting the water-to-solid ratio of the slurry and adding cellulose to improve fluidity, combined with vibration and carbonization curing techniques, the problem of insufficient pore filling in coral reef aggregates was solved, resulting in a significant improvement in mechanical properties and environmentally friendly large-scale application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN UNIV OF TECH
- Filing Date
- 2023-12-19
- Publication Date
- 2026-05-19
AI Technical Summary
In existing technologies, the pores of coral reef aggregate with larger particle size are difficult to be fully filled by carbonized cementitious materials during the carbonization process, resulting in poor mechanical properties. Furthermore, traditional methods are not effective in improving the mechanical properties of coral reef aggregate in large-scale applications.
By adjusting the water-to-solid ratio of the carbonized cementitious material slurry, adding cellulose such as HPMC and CMC to improve fluidity and uniformity, and removing air bubbles through vibration, the slurry penetrates into the pores of the coral reef aggregate. Subsequently, carbonation curing is carried out in a carbon dioxide environment to generate calcium carbonate to fill the pores and improve mechanical properties.
The prepared carbonized reinforced coral reef aggregate has low porosity, excellent mechanical properties, high carbon absorption, and low price, making it suitable for large-scale promotion. It is also compatible with existing preparation processes and is environmentally friendly.
Smart Images
Figure BDA0004616192620000071
Abstract
Description
Technical Field
[0001] This invention relates to the field of building materials technology, and in particular to a carbonized reinforced coral reef aggregate and its preparation method. Background Technology
[0002] Land reclamation refers to the process of pumping reef rocks and coral sand deposited on the foreshore slopes and lagoons onto the reef flats using dredgers, creating artificial islands that rise to a certain height above sea level after the water recedes. Coral sand is the primary soil and rock material in land reclamation projects. It is formed over millions of years by the biological remains of reef-building coral colonies, resulting from a series of physical, chemical, and biochemical processes. It is a soil and rock medium primarily composed of insoluble carbonates such as calcium carbonate and magnesium carbonate. The unique marine origin of coral sand, and the fact that it was largely not transported long distances during deposition, gives it characteristics that are significantly different from terrestrial sediments, such as highly irregular particle shapes, high porosity, easy breakage, and frequent cementation. This also results in mechanical properties that differ from ordinary terrestrial soils, exhibiting the characteristic of particle breakage even under conventional engineering stress levels. In addition, coral sand is the only material used for land reclamation of islands and reefs. Due to its unique marine biological origin and pore structure characteristics, coral sand particles will break under normal engineering stress levels, resulting in poor mechanical properties.
[0003] The main reason for this problem is that coral sand contains a large number of pores (porosity ratio of 0.9). These porous weak points often crack and fail under stress, resulting in significantly lower mechanical properties of coral sand compared to similar calcium carbonate materials. Therefore, patent CN202110501985.6 proposes using carbonized cementitious materials to fill the pores of coral reefs. First, the carbonized cementitious material is thoroughly mixed with calcium carbonate-based sand powder (such as coral sand powder). Then, water is added to the mixed dry mixture, and it is molded into a blank. Finally, the blank is carbonized to obtain the calcium carbonate-based sand powder-reinforced carbonized hardened body. However, the coral sand powder in this invention has a small particle size (1–300 μm), making it easy to be fully coated by the powder. Pore filling can be achieved by mixing it with carbonized cementitious material powder and adding water. For aggregates with larger particle sizes (5–40 mm) and more pores, which are more common in actual reclamation applications, it is difficult to fill all the pores and to distribute the aggregate evenly with water within the pores, hindering the carbonation reaction and resulting in insufficient mechanical properties of the coral reef aggregate. Furthermore, simply increasing the water-to-solid ratio to improve the fluidity of the slurry will reduce the amount of carbonized cementitious material entering the pores, making it difficult to fill the pores of the coral reef aggregate after the carbonization reaction, resulting in poor mechanical properties. Summary of the Invention
[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a carbonized reinforced coral reef aggregate and its preparation method, thereby solving the technical problem of poor mechanical properties of coral reef aggregate in the prior art.
[0005] To achieve the above-mentioned technical objectives, the technical solution provided by this invention is as follows:
[0006] In a first aspect, the present invention provides a method for preparing carbonized reinforced coral reef aggregate, comprising the following steps: mixing 100 parts by weight of carbonized cementitious material, 40-70 parts by weight of water and 1-5 parts by weight of cellulose, and stirring thoroughly to obtain a slurry; placing coral reef aggregate A on a sieve and immersing it completely in the slurry, and removing the sieve after shaking it for a period of time to obtain coral reef aggregate B; pre-drying coral reef aggregate B to obtain coral reef aggregate C; and carbonizing coral reef aggregate C in a carbon dioxide environment to obtain carbonized reinforced coral reef aggregate.
[0007] Secondly, the present invention provides a carbonized reinforced coral reef aggregate prepared by the above-described preparation method.
[0008] Compared with the prior art, the beneficial effects of the present invention include:
[0009] This invention adjusts the water-to-solid ratio of the carbonized cementitious material slurry to regulate its fluidity. The addition of cellulose enhances the slurry's fluidity and uniformity, ensuring that more carbonized cementitious material penetrates the pores of the coral reef aggregate at the same water-to-solid ratio. Simultaneously, vibration removes air bubbles from the aggregate, filling the pores with the carbonized cementitious material. Subsequently, carbonation curing technology causes minerals such as calcium silicate in the cementitious material to carbonize, producing calcium carbonate that fills the pores, reducing water absorption and significantly improving the mechanical properties of the coral reef aggregate. This method is suitable for large-particle-size coral reef aggregates, and the resulting carbonized reinforced coral reef aggregate exhibits low porosity, excellent mechanical properties, and high carbon absorption. It is highly compatible with existing preparation processes, inexpensive, environmentally friendly, and easily scaled up. Detailed Implementation
[0010] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0011] To address the issue of poor mechanical properties in traditional coral reef aggregates, particularly the difficulty in improving the mechanical properties of larger-sized coral reef aggregates through simple filling with cementitious materials, this invention utilizes the rheological properties of a carbonizable slurry to penetrate into the pores of the coral reef aggregate. Simultaneously, vibration removes air bubbles from within the aggregate, ensuring the slurry completely fills the pores. Pre-curing removes excess moisture, providing pathways for carbon dioxide penetration during the carbonation process. Carbonation curing then allows the carbonized cementitious material within the pores to generate calcium carbonate and other products, filling the pores. Since the main component of coral reef aggregate is calcium carbonate, this provides a template for the growth of the carbonized calcium carbonate and ensures a tight bond, significantly improving the mechanical properties of the carbon-enhanced coral reef aggregate.
[0012] This invention provides a method for preparing carbonized reinforced coral reef aggregate, comprising the following steps:
[0013] By weight, mix 100 parts carbonized cementitious material, 40-70 parts water and 1-5 parts cellulose, and stir thoroughly to obtain a slurry;
[0014] Coral reef aggregate A is placed on a screen and completely immersed in the slurry. After the screen is shaken for a period of time, it is removed to obtain coral reef aggregate B.
[0015] Coral reef aggregate B is placed in an oven and pre-dried to a specified water-to-solid ratio to obtain coral reef aggregate C;
[0016] Coral reef aggregate C is placed in a carbonization reactor and carbonized in a carbon dioxide environment to obtain carbonized reinforced coral reef aggregate.
[0017] Preferably, the cellulose comprises a mixture of hydroxypropyl methylcellulose (HPMC) and carboxymethyl cellulose (CMC).
[0018] More preferably, the mixing ratio of the carbonized cementitious material with water, HPMC, and CMC is 100:(40-70):(1-2):(1-2). Insufficient water content in the slurry will result in insufficient slurry fluidity; excessive water content will result in insufficient carbonized cementitious material in the slurry, making it difficult to fill pores after carbonization. Insufficient HPMC and CMC content in the slurry will lead to poor slurry homogeneity and fluidity, making it difficult to uniformly fill pores. Excessive HPMC and CMC content will result in excessively high slurry viscosity, making it difficult to penetrate pores.
[0019] Preferably, the particle size of the coral reef aggregate A is 5mm to 40mm.
[0020] Preferably, the carbonized cementitious material includes one or more of γ-C2S, C3S2, CS, low-calcium calcium silicate, steel slag, and magnesium slag; wherein γ-C2S, C3S2, and CS have essentially the same effect as carbonized cementitious materials; the particle size of the carbonized cementitious material is <70μm. Larger particle sizes make it difficult for the carbonized cementitious material to penetrate the micron-sized pores in the coral reef aggregate, leading to a decrease in its mechanical properties.
[0021] Preferably, the screen aperture size is smaller than the particle size of coral reef aggregate A and larger than the particle size of carbonized cementitious material; more preferably, the screen aperture size is ≤3mm.
[0022] Preferably, the oscillation time of the screen is 1 to 5 minutes. Too short an oscillation time will make it difficult for air bubbles inside the aggregate to escape, resulting in the slurry not filling the pores of the aggregate. Too long an oscillation time will cause the slurry to settle and stratify, reducing the amount of cementitious material in the aggregate and making it difficult to fill the pores.
[0023] Preferably, when pre-drying the coral reef aggregate, the pre-drying process can either expose the coral reef aggregate to a ventilated drying environment or place it in a closed space at a certain temperature to accelerate the drying process. Pre-drying is sufficient until the water-to-solid ratio of the slurry is 0.05–0.1. A water-to-solid ratio that is too low will make the carbonation reaction difficult to proceed, while a water-to-solid ratio that is too high will cause water to clog the pores, making it difficult for carbon dioxide to enter the aggregate.
[0024] Preferably, the coral reef aggregate C is placed in a carbonization reactor for carbonization curing; the carbonization curing conditions under a CO2 atmosphere are: time of 12-36 hours, curing temperature of 5-90°C, relative humidity of 30-80%, and CO2 concentration of 10-99%.
[0025] This invention provides carbonized reinforced coral reef aggregate prepared by the above-described preparation method.
[0026] Main mechanism of action and advantages of this invention:
[0027] (1) In this invention, carbonized cementitious material is mixed with water, HPMC, and CMC, and thoroughly stirred to obtain a slurry. Coral reef aggregate is placed on a sieve and completely immersed in the slurry. The sieve is then removed after being vibrated for a period of time. The coral reef aggregate is placed in an oven for pre-drying to a specified water-to-solid ratio. The coral reef aggregate is then placed in a carbonization reactor for carbonization. This invention adjusts the water-to-solid ratio (amount of water in the slurry) of the carbonized cementitious material slurry to adjust the fluidity of the carbonized cementitious material. By adding hydroxypropyl methylcellulose (HPMC) and carboxymethyl cellulose (CMC), the fluidity and uniformity of the slurry are synergistically improved, ensuring that more carbonized cementitious material can penetrate into the pores of the coral reef aggregate at the same water-to-solid ratio. At the same time, air bubbles inside the aggregate are expelled by vibration, allowing the pores to be filled by the carbonized cementitious material. Subsequently, carbonization curing technology is used to carbonize minerals such as calcium silicate in the carbonized cementitious material to produce calcium carbonate, which fills the pores and significantly improves the mechanical properties of the coral reef aggregate.
[0028] (2) The present invention promotes the filling of the slurry by oscillation. The more fully the slurry is filled, the better the reinforcement effect on the aggregate. At the same time, since the slurry contains a lot of water, a large number of pores will be left after pre-drying, which is conducive to the formation of channels for carbon dioxide to enter. Finally, the volume expansion of the carbonation reaction will fill the pores, forming a dense calcium carbonate structure, which greatly reduces the water absorption rate and effectively enhances its mechanical properties.
[0029] (3) The coral reef aggregate provided by the present invention has large particle size, low porosity, excellent mechanical properties, and high carbon absorption capacity. It is highly compatible with existing preparation processes, inexpensive, environmentally friendly, and easy to promote on a large scale.
[0030] In this invention, unless otherwise specified, all raw materials required for preparation are commercially available products well known to those skilled in the art.
[0031] The present invention does not impose any particular limitation on the process of mixing the gelling material with water, HPMC, and CMC; any process known in the art that can mix the materials evenly is acceptable.
[0032] The present invention does not have any special requirements for the oscillation mode and frequency of the screen; it is sufficient to follow a process well known in the art to remove air bubbles from the coral reef aggregate.
[0033] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0034] In the following examples, the coral reef aggregate used has a particle size of 5mm-40mm, the carbonized cementitious material has a particle size of <70μm, and the screen mesh size is 150μm.
[0035] Example 1
[0036] The carbonized cementitious material in Example 1 consists of γ-C2S;
[0037] A method for preparing carbonized reinforced coral reef aggregate:
[0038] By weight, 100 parts of carbonized gelling material are mixed with 50 parts of water, 2 parts of hydroxypropyl methylcellulose (HPMC), and 2 parts of carboxymethyl cellulose (CMC), and stirred thoroughly to obtain a slurry;
[0039] Place coral reef aggregate A on a screen and immerse it completely in the slurry. After shaking the screen for 4 minutes, remove it to obtain coral reef aggregate B.
[0040] Coral reef aggregate B was placed in an oven and pre-dried until the water-to-solid ratio of the slurry was 0.07, thus obtaining coral reef aggregate C;
[0041] Coral reef aggregate C was placed in a carbonization reactor and carbonized for 24 hours with a carbon dioxide concentration of 99%. The carbonization curing temperature was 20℃ and the relative humidity was 60%, resulting in carbonized reinforced coral reef aggregate.
[0042] Example 2
[0043] The only difference from Example 1 is that the carbonized gelling material component is C3S2, and the composition of the slurry in the preparation method is 100 parts carbonized gelling material, 70 parts water, 2 parts hydroxypropyl methylcellulose (HPMC), and 2 parts carboxymethyl cellulose (CMC); other steps and conditions are the same as in Example 1.
[0044] Example 3
[0045] The only difference from Example 1 is that the carbonized cementitious material component is CS, and the sieve oscillation time in the preparation method is 2 min; the other steps and conditions are the same as in Example 1.
[0046] Example 4
[0047] The only difference from Example 1 is that the water-to-solid ratio of the slurry is 0.05 during pre-drying in the preparation method. Other steps and conditions are the same as in Example 1.
[0048] Comparative Example 1
[0049] The only difference from Example 1 is that in the preparation method, the carbonized cementitious material is first mixed with coral reef aggregate, HPMC and CMC and then water is added and mixed, and then poured into a container with a sieve; the other steps and conditions are the same as in Example 1.
[0050] Comparative Example 2
[0051] The only difference from Example 1 is that the composition of the slurry in the preparation method is 100 parts carbonized gelling material, 20 parts water, 2 parts hydroxypropyl methylcellulose (HPMC), and 2 parts carboxymethyl cellulose (CMC). The other preparation methods are the same as in Example 1.
[0052] Comparative Example 3
[0053] The only difference from Example 1 is that the composition of the slurry in the preparation method is 100 parts carbonized cementitious material and 50 parts water; the other steps and conditions are the same as in Example 1.
[0054] Comparative Example 4
[0055] The only difference from Example 1 is that the composition of the slurry in the preparation method is 100 parts carbonized gelling material, 50 parts water, and 2 parts hydroxypropyl methylcellulose (HPMC), while the other steps and conditions are the same as in Example 1.
[0056] Comparative Example 5
[0057] The only difference from Example 1 is that the composition of the slurry in the preparation method is 100 parts carbonized gelling material, 50 parts water, and 2 parts carboxymethyl cellulose (CMC), while the other steps and conditions are the same as in Example 1.
[0058] Comparative Example 6
[0059] The only difference from Example 1 is that the sieve oscillation time in the preparation method is 10s, while the other steps and conditions are the same as in Example 1.
[0060] Comparative Example 7
[0061] The only difference from Example 1 is that the sieve oscillation time in the preparation method is 10 min, while the other steps and conditions are the same as in Example 1.
[0062] Comparative Example 8
[0063] The only difference from Example 1 is that the water-to-solid ratio of the slurry is 0.3 during pre-drying in the preparation method. Other steps and conditions are the same as in Example 1.
[0064] Performance testing
[0065] The degree of carbonization, water absorption, and compressive strength of the carbonized reinforced coral reef aggregates prepared in Examples 1-4 and Comparative Examples 1-8 were tested. The test method for the degree of carbonization was as follows: the loss on ignition of the carbonized cementitious material at 300℃-1000℃ was tested in a high-temperature furnace, and the theoretical maximum carbon fixation was calculated by the mass of the remaining solid after heating to 1000℃; finally, the degree of carbonization was obtained by dividing the loss on ignition by the theoretical maximum carbon fixation. The compressive strength and water absorption were tested according to GB / T 17431.2 "Detailed Rules for Testing Lightweight Aggregates". The test results are shown in Table 1.
[0066] Table 1. Physical properties of coral reef aggregates prepared in Examples 1-4 and Comparative Examples 1-8
[0067]
[0068] As shown in Table 1, the coral reef aggregate prepared by this invention has a large carbon absorption capacity (the carbonization degree of the carbonized cementitious material reaches 31-37%), high compressive strength (8.9-9.5 MPa), and low water absorption (6.7-7.0%). It can be used as a high-performance dredged and filled island-building rock and soil material, as well as as concrete aggregate.
[0069] A comparison of the data from the carbonized reinforced coral reef aggregate prepared in Example 1 and the carbonized reinforced coral reef aggregate prepared in Comparative Example 1 in Table 1 shows that the mixing sequence during the slurry preparation process has a significant impact on the performance of the carbonized reinforced coral reef aggregate. The method of mixing the carbonized cementitious material with the coral reef aggregate, HPMC, CMC and then adding water will result in less carbonized cementitious material entering the pores. After the carbonization reaction, it will be difficult to fill the pores of the coral reef aggregate, resulting in poor mechanical properties and increased porosity.
[0070] A comparison of the data from the carbonized reinforced coral reef aggregates prepared in Examples 1-2 and Comparative Example 2 in Table 1 shows that the amount of water used in the carbonized reinforced coral reef aggregates has a significant impact on the carbonization reaction. When the amount of water is too low, the water required for the carbonization reaction is insufficient, resulting in insufficient filling of pores and a decrease in aggregate strength. When the amount of water is too high, the slurry concentration will decrease, and the amount of carbonized cementitious material that ultimately enters the coral reef aggregates will be reduced, thereby reducing the performance of the resulting carbonized reinforced coral reef aggregates.
[0071] A comparison of the data of carbonized reinforced coral reef aggregate prepared in Example 1 and the carbonized reinforced coral reef aggregate prepared in Comparative Examples 3-5 in Table 1 shows that HPMC and CMC have a significant impact on fluidity. The absence of either one will lead to a decrease in slurry fluidity, making it difficult to fill pores, and ultimately resulting in a decrease in the strength of the carbonized reinforced coral reef aggregate. This indicates that the use of HPMC and CMC in combination in this invention can produce a synergistic effect.
[0072] A comparison of the data from the carbonized reinforced coral reef aggregates prepared in Examples 1 and 3 in Table 1 with those prepared in Comparative Examples 6 and 7 shows that the oscillation time of the screen is very important. If the oscillation time is too short, it will be difficult for air bubbles inside the aggregate to be vented, and the slurry will be difficult to enter the internal pores of the aggregate. If the oscillation time is too long, it will cause the slurry to settle and stratify, reduce the amount of cementitious material in the aggregate, make it difficult to fill the pores, and also reduce the relevant properties of the obtained carbonized reinforced coral reef aggregate.
[0073] A comparison of the data of carbonized reinforced coral reef aggregate prepared in Examples 1 and 4 and the carbonized reinforced coral reef aggregate prepared in Comparative Example 8 in Table 1 shows that the water-to-solid ratio control after pre-drying is very important. If the water-to-solid ratio is too low, the carbonization reaction will be difficult to proceed; if the water-to-solid ratio is too high, the water will block the pores, making it difficult for carbon dioxide gas to enter the pores and reducing the degree of carbonization of the carbonized cementitious material.
[0074] This invention provides a carbonized reinforced coral reef aggregate and its preparation method, comprising the following steps: mixing carbonized cementitious material with water, hydroxypropyl methylcellulose (HPMC), and carboxymethyl cellulose (CMC), and stirring thoroughly to obtain a slurry; placing the coral reef aggregate on a sieve and completely immersing it in the slurry, then removing the sieve after shaking it for a period of time; pre-drying the coral reef aggregate in an oven to a specified water-to-solid ratio; and placing the coral reef aggregate in a carbonization reactor and carbonizing it in a carbon dioxide environment. The carbonized slurry containing HPMC and CMC has excellent fluidity, allowing it to penetrate into the pores of the coral reef aggregate and expel air bubbles from the aggregate through shaking. Excess moisture is then removed using pre-curing technology, providing a channel for carbon dioxide penetration during the carbonization reaction; further, carbonization curing allows the carbonized cementitious material in the pores of the coral reef aggregate to carbonize and generate products such as calcium carbonate, filling the pores of the coral reef aggregate and forming a dense calcium carbonate structure, greatly reducing water absorption and improving its mechanical strength.
[0075] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A method for preparing carbonized reinforced coral reef aggregate, characterized in that, Includes the following steps: By weight, mix 100 parts carbonized cementitious material, 40-70 parts water and 1-5 parts cellulose, and stir thoroughly to obtain a slurry; Coral reef aggregate A is placed on a screen and completely immersed in the slurry. After the screen is shaken for a period of time, it is removed to obtain coral reef aggregate B. Coral reef aggregate B is pre-dried to obtain coral reef aggregate C; Coral reef aggregate C was carbonized and cured in a carbon dioxide environment to obtain carbonized reinforced coral reef aggregate. The cellulose includes a mixture of hydroxypropyl methylcellulose and carboxymethyl cellulose; The mass ratio of the carbonized gelling material, water, hydroxypropyl methylcellulose and carboxymethyl cellulose is 100:(40-70):(1-2):(1-2); The particle size of the coral reef aggregate A is 5mm to 40mm; The sieve oscillation time is 1–5 minutes; Coral reef aggregate B is pre-dried to a water-to-solid ratio of 0.05–0.1 in the slurry.
2. The method for preparing carbonized reinforced coral reef aggregate according to claim 1, characterized in that, The carbonized cementitious material includes one or more of low-calcium calcium silicate, steel slag, and magnesium slag; the particle size of the carbonized cementitious material is <70μm.
3. The method for preparing carbonized reinforced coral reef aggregate according to claim 1, characterized in that, The sieve aperture size is smaller than the particle size of coral reef aggregate A, and the sieve aperture size is larger than the particle size of carbonized cementitious material.
4. The method for preparing carbonized reinforced coral reef aggregate according to claim 1, characterized in that, The conditions for carbonization and curing of coral reef aggregates are: time 12-36 hours, curing temperature 5-90℃, relative humidity 30-80%, and CO2 concentration 10-99%.
5. Carbonized reinforced coral reef aggregate prepared by the preparation method according to any one of claims 1-4.