Low-carbon marine cement-based solidified soil and co2 split-flow pre-mineralization method thereof

Abstract

The application discloses a kind of low-carbon marine cement-based solidified soil and its CO2 diversion pre-mineralization method, it is related to offshore wind power foundation protection and novel building material technical field, and it is made by the following weight parts of component: coastal beach sludge: 100~130 parts, sludge weight is 70%~100% with water content ratio;Ordinary Portland cement: 10~15 parts;S95 grade superfine mineral powder: 8~12 parts;Cellulose ether: 0.03~0.06 parts;Anhydrous sodium sulfate: 0.8~1.5 parts;Polycarboxylic acid water reducing agent: 0.03~0.06 parts;Sodium gluconate: 0.03~0.10 parts;Calcium formate: 0.5~1.5 parts;Anionic polyacrylamide: 0.005~0.015 parts.Suitable for winter low-temperature construction environment, coastal beach sludge is mainly used as main raw material offshore wind power pile foundation anti-scouring low-temperature early-strength anti-scouring flow state solidified soil.

Description

Technical Field

[0001] This invention relates to the field of offshore wind power foundation protection and new building materials technology, and in particular to a low-carbon marine cement-based solidified soil and its CO2 diversion premineralization method. Background Technology

[0002] Backfilling and protection of scour pits in offshore wind turbine foundations faces severe technical challenges in low-temperature environments (especially in winter or high-latitude sea areas where ambient temperatures can drop to 5–10°C). Low temperatures significantly inhibit the hydration rate of cementitious materials, leading to slow hardening of the fluidized solidified soil and severely delayed early strength development, resulting in the following prominent problems: Firstly, the erosion resistance develops too slowly. Under tidal action, the water flow velocity in the backfill area can reach 2-3 m / s. If the newly poured fluidized solidified soil cannot develop sufficient strength to resist the erosion of the periodic water flow within a few hours after pouring, it will be easily eroded and peeled off, failing to form an effective protective layer. In severe cases, it may even be completely washed away, leading to the failure of the protective project, resulting in material waste and project delays.

[0003] Secondly, the construction window is severely limited. To compensate for the slow hydration at low temperatures, existing technologies often use sodium sulfate (anhydrous sodium sulfate) as an early-strength activator. However, the activating effect of sodium sulfate is relatively rapid. Although it can accelerate early strength growth to some extent, it also leads to an excessively rapid loss of slurry fluidity over time, significantly shortening the workable time from mixing to pouring. This change places stringent demands on the organization and scheduling of offshore construction and pumping equipment. If the pouring process is delayed, the slurry may experience premature setting, pipe blockage, or failure to flow by gravity, seriously affecting construction quality and efficiency.

[0004] Meanwhile, in order to reduce engineering costs, there is an increasing tendency in the field to increase the amount of sludge and reduce the amount of cement. This technological trend makes the problem of low-temperature early strength more prominent—the absolute amount of cement minerals available for hydration is insufficient, and it is difficult to obtain ideal early strength by simply using sodium sulfate for activation. It is evident that there is a lack of a fluidized solidified soil material in the current technology that can both rapidly obtain early erosion resistance under low-temperature conditions and maintain a relatively long workable time. There is an urgent need to develop a new material system that takes into account both early strength performance and construction adaptability. Summary of the Invention

[0005] This invention provides a low-carbon marine cement-based solidified soil and its CO2 diversion pre-mineralization method to address the prominent contradictions of slow early strength development and inability to form effective erosion resistance during tidal cycles in low-temperature winter environments, as well as the rapid loss of fluidity and narrow construction window caused by the addition of sodium sulfate for early strength. This invention achieves reliable construction and rapid hardening under low-temperature conditions. It is suitable for low-temperature, early-strength, erosion-resistant fluidized solidified soil for offshore wind power pile foundations using nearshore tidal mud as the main raw material in low-temperature winter construction environments.

[0006] According to one aspect of this disclosure, a low-carbon marine cement-based solidified soil is provided, characterized in that it is made from the following components in parts by weight: nearshore tidal flat slurry: 100-130 parts, based on the weight of slurry with a water content of 70%-100%; ordinary silicate cement: 10-15 parts; S95 grade ultrafine mineral powder: 8-12 parts; cellulose ether: 0.03-0.06 parts; sodium sulfate: 0.8-1.5 parts; polycarboxylate superplasticizer: 0.03-0.06 parts; sodium gluconate: 0.03-0.10 parts; calcium formate: 0.5-1.5 parts; anionic polyacrylamide: 0.005-0.015 parts; The nearshore tidal flat silt is natural tidal flat silt from the sea area adjacent to the offshore wind farm, with a salt content of 1% to 3% and an organic matter content of ≤5%.

[0007] In one possible implementation, the cellulose ether is hydroxypropyl methylcellulose ether or hydroxyethyl cellulose, with a viscosity specification of 150,000 to 200,000 mPa·s.

[0008] In one possible implementation, the sodium gluconate is industrial grade with a purity of ≥98%.

[0009] In one possible implementation, the calcium formate is industrial grade with a purity of ≥96%.

[0010] In one possible implementation, the anionic polyacrylamide has a molecular weight of 8 million to 12 million.

[0011] In one possible implementation, the sodium sulfate is industrial anhydrous sodium sulfate with a purity ≥98%.

[0012] A method for CO2 diversion and premineralization of low-carbon marine cement-based solidified soil, the method comprising: S1, silt pretreatment: Near-shore mudflat silt is passed through a 5mm sieve to remove impurities, the moisture content is tested and adjusted to 70% to 100%, and qualified silt slurry is prepared for use. S2, Dry Mix Preparation: According to the proportion, ordinary Portland cement, S95 grade ultrafine mineral powder, sodium sulfate, calcium formate, and polycarboxylate superplasticizer are added to a dry powder mixer and stirred for 3-5 minutes until uniform to obtain dry mix; S3, Preparation of admixture solution: Dissolve cellulose ether, sodium gluconate and anionic polyacrylamide in mixing water according to the ratio, and stir until completely dissolved to obtain admixture solution; S4, Preparation of fluidized solidified soil: Put the sludge slurry from step S1 into the mixer, start the mixer, slowly add the dry mixture from step S2, and stir for 1 to 2 minutes; then add the admixture solution from step S3, and continue stirring for 3 to 5 minutes until the slurry is uniform, thus obtaining low-temperature early-strength erosion-resistant fluidized solidified soil.

[0013] In one possible implementation, the method further includes: S5, send the solidified soil from S4 into the mineralization reaction device; Carbon dioxide of a preset concentration is uniformly introduced into the reactor, making full contact with the solidified soil, penetrating into the interior of the solidified soil, and reacting with the alkaline substances produced by cement hydration to generate carbonate crystals. While sealing carbon, the soil strength is rapidly enhanced. The carbon dioxide mentioned includes industrial waste gas.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. Rapid early strength development at low temperatures allows for the construction of a ternary time-controlled early strength system, precisely resolving the conflict between early strength development at low temperatures and the construction window: This invention overcomes the technical limitations of traditional single early-strength agents. Through the synergistic combination of sodium gluconate, sodium sulfate, and calcium formate, it achieves for the first time "precise timing control" of the solidification and hardening process of fluidized solidified soil. In the initial mixing stage (0~120 minutes): Sodium gluconate plays a moderate retarding role, effectively inhibiting premature hydration of cement particles. Combined with the dispersing effect of polycarboxylate superplasticizer, the slurry maintains excellent fluidity within 90~120 minutes, and the loss rate over time is controlled within 15%. This provides sufficient operating time for long-distance pumping and complex pouring operations at sea, and significantly reduces the stringent requirements for construction organization and scheduling.

[0015] After pouring and settling: As the retarding effect naturally subsides, the early strength performance of sodium sulfate and calcium formate is released efficiently. Sodium sulfate effectively activates the pozzolanic activity of S95 grade ultrafine mineral powder, while calcium formate accelerates the hydration process of C3S minerals in cement. The two act on different cementitious components, producing a significant synergistic effect.

[0016] Tests showed that, under low-temperature curing conditions of 5℃, the unconfined compressive strength of the solidified soil of this invention reached over 0.3 MPa underwater after 1 day (up to 0.40 MPa in the examples), far superior to the comparative scheme with only sodium sulfate admixture. This "slow at first, fast later" setting and hardening rhythm fundamentally resolves the inherent contradiction between early strength and workability, providing reliable early strength assurance for pile foundation protection projects in winter and high-latitude sea areas.

[0017] 2. Constructing a dual anti-erosion mechanism of "polymer network physical anchoring - hydration product chemical bonding" to achieve full-cycle protection: Addressing the technical pain point that newly poured and solidified soil is easily dispersed by tidal currents in the "zero strength" stage, this invention innovatively introduces anionic polyacrylamide, providing dual protection that is sequentially connected with the later hydration and hardening process. Physical anchoring stage (0-2 hours after pouring): The long molecular chains of anionic polyacrylamide rapidly form a three-dimensional network structure in the slurry, giving the solidified soil excellent structural viscosity and cohesion. Even before the chemical cementitious strength is established, it can resist the early tidal scouring with a flow velocity of up to 2.5 m / s by means of the physical network. The underwater cement loss rate is controlled below 5%, achieving the immediate protective effect of "physically locking" the material in the scouring pit.

[0018] Chemical bonding stage (after hydration hardening): As the ternary early-strength system kicks in, hydration products are continuously generated, interweaving and synergistically reinforcing the aforementioned physical network to form a stable spatial framework structure, providing long-term, reliable erosion resistance. The two stages are closely sequential, achieving full-process protection from the initial casting stage to long-term service.

[0019] 3. Coupled with CO2 diversion pre-mineralization technology to achieve synergistic effects of "low-carbon enhancement". This invention introduces a CO2 diversion pre-mineralization step after the preparation of the fluidized solidified soil. Industrial waste gas containing CO2 is uniformly introduced into the solidified soil through a gas diversion pipeline system. The CO2 permeates and reacts in situ with alkaline substances such as calcium hydroxide produced during cement hydration, generating stable carbonate crystals. This process not only effectively seals up industrial waste CO2, resulting in significant carbon emission reduction benefits, but also fills the soil pores with the generated carbonate crystals, further densifying the microstructure. This allows the solidified soil to gain additional strength while sealing carbon (in the examples, the 28-day strength can reach over 0.85 MPa), truly achieving a synergistic unity of "low carbon" and "high strength."

[0020] 4. The resource utilization of high-volume sludge has both significant economic and environmental value. This invention achieves performance far exceeding conventional formulations through the synergistic effect of the aforementioned multi-component combination, while maintaining a low-cost formulation with a nearshore tidal flat silt content of 100-130 parts (based on a moisture content of 70%-100%) and a common silicate cement content of only 10-15 parts. This technology can effectively utilize large quantities of waste tidal flat silt generated from offshore wind power dredging, significantly reducing off-site disposal costs and carbon emissions. It aligns with the development direction of green construction and circular economy in marine engineering, demonstrating outstanding economic and social benefits. Attached Figure Description

[0021] Figure 1The diagram shows a flowchart of a CO2 diversion and premineralization method for low-carbon marine cement-based solidified soil according to an embodiment of the present disclosure. Detailed Implementation

[0022] Various exemplary embodiments, features, and aspects of this disclosure will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0023] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0024] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art have not been described in detail in order to highlight the main points of this disclosure.

[0025] Example 1: A low-carbon marine cement-based solidified soil, with the following component weight ratios: nearshore tidal flat sludge (85% water content): 115 parts; P·O 42.5 ordinary Portland cement: 12 parts; S95 grade ultrafine mineral powder: 10 parts; hydroxypropyl methylcellulose ether (viscosity 180,000 mPa·s): 0.04 parts; sodium sulfate (industrial anhydrous sodium sulfate, purity 99%): 1.2 parts; polycarboxylate superplasticizer (powder, water reduction rate 27%): 0.04 parts; sodium gluconate (industrial grade, purity 98%): 0.06 parts; calcium formate (industrial grade, purity 96%): 1.0 part; anionic polyacrylamide (molecular weight 10 million): 0.01 parts. Preparation method: S1, the tidal flat silt passed through a 5mm sieve, with a moisture content of 85%, is qualified and can be used directly.

[0026] S2, put cement, mineral powder, sodium sulfate, calcium formate and polycarboxylate superplasticizer into a dry powder mixer and stir for 4 minutes to obtain a uniform dry mix.

[0027] S3, dissolve cellulose ether, sodium gluconate, and anionic polyacrylamide in an appropriate amount of fresh water and stir until completely dissolved to obtain an additive solution.

[0028] S4. Add 115 parts of sludge slurry to a forced mixer, and add dry mix while mixing. Mix for 1.5 minutes; then add the admixture solution and continue mixing for 4 minutes to obtain a uniform, fluidized solidified soil. The measured initial flowability is 220 mm.

[0029] S5, send the solidified soil from S4 into the mineralization reaction device; Carbon dioxide of a preset concentration is uniformly introduced into the reactor, making full contact with the solidified soil, penetrating into the interior of the solidified soil, and reacting with the alkaline substances produced by cement hydration to generate carbonate crystals. While sealing carbon, the soil strength is rapidly enhanced. The carbon dioxide mentioned includes industrial waste gas.

[0030] Low-temperature performance testing (all specimens were molded and cured at a constant temperature of 5℃): Unconfined compressive strength underwater in 1 day: 0.35 MPa 3D underwater unconfined compressive strength: 0.52 MPa 7-day underwater unconfined compressive strength: 0.71 MPa 28-day underwater unconfined compressive strength: 0.85 MPa Flow over time: initial 220 mm, 205 mm at 60 minutes, 190 mm at 120 minutes (loss rate 13.6%). Underwater cement loss rate: 3.8% Early erosion resistance test (water tank started 1 hour after pouring, flow rate 2.5 m / s, erosion for 30 minutes): mass loss rate 4.2%. Example 2: A low-carbon marine cement-based solidified soil, with the following component weight ratios: nearshore tidal flat sludge (75% water content): 100 parts; P·O 42.5 ordinary Portland cement: 15 parts; S95 grade ultrafine mineral powder: 8 parts; hydroxypropyl methylcellulose ether (viscosity 150,000 mPa·s): 0.03 parts; sodium sulfate: 0.8 parts; polycarboxylate superplasticizer: 0.03 parts; sodium gluconate: 0.03 parts; calcium formate: 1.5 parts; anionic polyacrylamide (molecular weight 8 million): 0.005 parts; the preparation method is the same as in Example 1. Results of curing at 5℃: 1-day strength 0.40 MPa, 28-day strength 0.92 MPa, initial flowability 210 mm, 120-minute flowability 185 mm (loss rate 11.9%), early scour mass loss rate 3.8%.

[0031] Example 3: A low-carbon marine cement-based solidified soil, with the following component weight ratios: nearshore tidal flat sludge (98% water content): 130 parts; P·O 42.5 ordinary Portland cement: 10 parts; S95 grade ultrafine mineral powder: 12 parts; hydroxyethyl cellulose (viscosity 200,000 mPa·s): 0.06 parts; sodium sulfate: 1.5 parts; polycarboxylate superplasticizer: 0.06 parts; sodium gluconate: 0.10 parts; calcium formate: 0.5 parts; anionic polyacrylamide (molecular weight 12 million): 0.015 parts; the preparation method is the same as in Example 1. Results of curing at 5℃: 1-day strength 0.28 MPa, 28-day strength 0.76 MPa, initial flowability 235 mm, 120-minute flowability 195 mm (loss rate 17.0%), early scour mass loss rate 4.8%.

[0032] This invention achieves significant performance improvements by adding only small amounts of sodium gluconate and calcium formate, while maintaining a high sludge content (100-130 parts) and a low cement content (10-15 parts). The overall cost is far lower than that of solutions using all commercial materials, demonstrating outstanding economic advantages. Simultaneously, it facilitates the large-scale disposal of nearshore tidal flat sludge, aligning with the development direction of marine engineering waste resource utilization and green construction, thus yielding substantial social and environmental benefits.

[0033] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A low-carbon marine cement-based solidified soil, characterized in that, It is made from the following components in parts by weight: nearshore mud slurry: 100-130 parts, based on the weight of mud slurry with a water content of 70%-100%; ordinary silicate cement: 10-15 parts; S95 grade ultrafine mineral powder: 8-12 parts; Cellulose ether: 0.03–0.06 parts; Sodium sulfate: 0.8–1.5 parts; polycarboxylate superplasticizer: 0.03–0.06 parts; Sodium gluconate: 0.03–0.10 parts; calcium formate: 0.5–1.5 parts; anionic polyacrylamide: 0.005–0.015 parts; The near-shore mudflat silt is natural mudflat silt from the sea area adjacent to the offshore wind farm, with a salt content of 1% to 3% and an organic matter content of ≤5%.

2. The low-carbon marine cement-based solidified soil according to claim 1, characterized in that, The cellulose ether is hydroxypropyl methylcellulose ether or hydroxyethyl cellulose, with a viscosity specification of 150,000 to 200,000 mPa·s.

3. The low-carbon marine cement-based solidified soil according to claim 1, characterized in that, The sodium gluconate is industrial grade with a purity of ≥98%.

4. The low-carbon marine cement-based solidified soil according to claim 1, characterized in that, The calcium formate is industrial grade with a purity of ≥96%.

5. The low-carbon marine cement-based solidified soil according to claim 1, characterized in that, The anionic polyacrylamide has a molecular weight of 8 million to 12 million.

6. The low-carbon marine cement-based solidified soil according to claim 1, characterized in that, The sodium sulfate is industrial anhydrous sodium sulfate with a purity of ≥98%.

7. A method for CO2 diversion and pre-mineralization of low-carbon marine cement-based solidified soil, characterized in that, The method includes: S1, silt pretreatment: Near-shore mudflat silt is passed through a 5mm sieve to remove impurities, the moisture content is tested and adjusted to 70% to 100%, and qualified silt slurry is prepared for use. S2, Dry Mix Preparation: According to the proportion, ordinary Portland cement, S95 grade ultrafine mineral powder, sodium sulfate, calcium formate, and polycarboxylate superplasticizer are added to a dry powder mixer and stirred for 3-5 minutes until uniform to obtain dry mix; S3, Preparation of admixture solution: Dissolve cellulose ether, sodium gluconate and anionic polyacrylamide in mixing water according to the ratio, and stir until completely dissolved to obtain admixture solution; S4, Preparation of fluidized solidified soil: Put the sludge slurry from step S1 into the mixer, start the mixer, slowly add the dry mixture from step S2, and stir for 1 to 2 minutes; then add the admixture solution from step S3, and continue stirring for 3 to 5 minutes until the slurry is uniform, thus obtaining low-temperature early-strength erosion-resistant fluidized solidified soil.

8. The method for CO2 diversion and pre-mineralization of low-carbon marine cement-based solidified soil according to claim 7, characterized in that, The method further includes: S5, send the solidified soil from S4 into the mineralization reaction device; Carbon dioxide of a preset concentration is uniformly introduced into the reactor, making full contact with the solidified soil, penetrating into the interior of the solidified soil, and reacting with the alkaline substances produced by cement hydration to generate carbonate crystals. While sealing carbon, the soil strength is rapidly enhanced. The carbon dioxide mentioned includes industrial waste gas.

Images