Hybrid fiber seawater coral sand engineering cement-based composite material and preparation method thereof

Abstract

The invention relates to the technical field of cement-based composite materials, and provides a hybrid fiber seawater coral sand engineering cement-based composite material and a preparation method thereof. Each cubic meter of the composite material is prepared from the following raw materials by mass: 600-700 kg of Portland cement; 580 to 650 kg of mineral powder; 300 to 600 kg of coral sand; 300 to 600 kg of seawater; 5-8 kg of a water reducing agent; 5 * 10 <-3 > to 10 * 10 <-3 > kg of steel fibers And 0.5 * 10 <-4 > to 3 * 10 <-4 > kg of polypropylene According to the invention, coral sand is used as fine aggregate, seawater is used as a mixing solution, a polycarboxylic acid water reducer is matched, and steel fibers and polypropylene fibers are introduced at the same time, so that a multi-dimensional enhanced synergistic mechanism is formed. By optimizing the mixing proportion of various fibers, the compressive strength, the splitting tensile strength and the after-peak toughness of the composite material can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cement-based composite materials, and in particular to a mixed fiber seawater coral sand engineering cement-based composite material and a preparation method thereof. Background Art

[0002] With the development of island and reef construction, constrained by remoteness from the mainland, high water resources, and material transportation costs, the use of local materials has become a key breakthrough. The combination of seawater and coral sand is considered an effective means of addressing the material sourcing issues in the preparation of island and reef concrete. Among them, Seawater Coral Sand Engineering Cementitious Composite (SCECC) is gaining increasing application in offshore infrastructure construction due to its advantages such as easy material acquisition and strong environmental adaptability.

[0003] However, due to the natural defects of coral aggregates such as low strength, high porosity, and high brittleness, SCECC materials generally suffer from poor ductility, early cracking, and weak deformation resistance, which seriously restricts their application safety and durability under extreme working conditions such as complex loads such as impact, vibration, or post-disaster fires.

[0004] Traditional reinforcement methods, such as adding a single fiber type (e.g., steel fiber, polyvinyl alcohol fiber, polypropylene fiber), can improve certain mechanical properties of a material to a certain extent, but struggle to achieve both high strength and high ductility, limiting their engineering applicability. A single fiber type often prioritizes either compressive or tensile strength, failing to fully meet complex engineering requirements.

[0005] In recent years, the concept of "hybrid fiber reinforcement" has gradually emerged. This involves incorporating multiple fibers with different elastic moduli and reinforcement mechanisms into cement-based composites, synergistically balancing crack control, impact resistance, and overall toughness. This approach could open up new avenues for improving the mechanical properties of traditional ECC (engineered cement-based composites) or SCECC (seawater coral sand engineered cement-based composites) in complex environments. However, its specific application in seawater coral sand systems is still lacking in systematic research and engineering practice verification, especially in the detailed analysis of fiber mixing ratios, stress-strain behavior evolution, and crack failure mechanisms. Summary of the Invention

[0006] The purpose of the present invention is to provide a mixed fiber seawater coral sand engineering cement-based composite material and a preparation method thereof, so as to fill the gaps in the prior art.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a mixed fiber seawater coral sand engineering cement-based composite material, wherein each cubic meter of the composite material is prepared from raw materials containing the following mass contents:

[0009]

[0010] Preferably, the Portland cement comprises P.O42.5 ordinary Portland cement;

[0011] The mineral powder comprises S95 grade mineral powder;

[0012] The particle size of the coral sand is ≤2.36 mm.

[0013] Preferably, the steel fiber has a length of 10 to 15 mm and a diameter of 0.1 to 0.3 mm;

[0014] The polypropylene fiber has a length of 4 to 8 mm and a diameter of 0.02 to 0.03 mm.

[0015] Preferably, the water reducer comprises a polycarboxylate water reducer.

[0016] Preferably, each cubic meter of composite material is prepared from raw materials containing the following mass contents:

[0017]

[0018] The present invention also provides a method for preparing the composite material, comprising the following steps:

[0019] (1) mixing silicate cement, mineral powder and coral sand to obtain a first mixture;

[0020] (2) mixing the obtained first mixture with the first portion of seawater to obtain a second mixture;

[0021] (3) mixing the obtained second mixture with steel fiber and polypropylene fiber to obtain a third mixture;

[0022] (4) mixing the obtained third mixture with a water reducer and the remaining seawater to obtain a fourth mixture;

[0023] (5) The fourth mixed material is subjected to environmental curing and seawater curing in sequence to obtain a composite material.

[0024] Preferably, the mass ratio of the first portion of seawater to the remaining portion of seawater is (85-95):(5-15).

[0025] Preferably, the temperature of the environmental curing is 18-23° C., the humidity is 93-98%, and the time is 20-30 hours.

[0026] Preferably, the seawater curing is performed by immersing the product in seawater for 25 to 30 days.

[0027] The present invention provides a mixed fiber seawater coral sand engineering cement-based composite material and a preparation method thereof. The present invention uses coral sand as fine aggregate, seawater as mixing liquid, and is mixed with a polycarboxylic acid water reducer, and simultaneously introduces steel fiber and polypropylene fiber to form a multi-dimensional reinforcement synergistic mechanism. By optimizing the mixing ratio of various types of fibers, the compressive strength and splitting tensile strength of the composite material can be significantly improved. The mixed steel fiber and polypropylene fiber form a synergistic reinforcement system in the material matrix, in which the steel fiber mainly controls the macro crack suppression and the organic fiber mainly controls the micro crack extension, jointly improving the crack control ability, increasing the peak strain, and slowing down the destruction process. The amount of the substances in the composite material of the present invention is specially customized for the characteristics of seawater and coral sand to ensure that it still has good mixing properties, mechanical properties and molding stability in a high-salt and high-porosity material environment.

[0028] The method provided by the present invention achieves uniform fiber dispersion by adjusting the feeding sequence, avoiding agglomeration and ensuring uniform and repeatable material properties. The present invention provides a high-performance marine engineering material with excellent strength, which can be widely used in island and reef foundations, offshore platforms, port protection, and wartime reinforcement projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart of the operation process of Example 1 of the present invention;

[0030] Figure 2 Product photos obtained for Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The present invention provides a mixed fiber seawater coral sand engineering cement-based composite material, wherein each cubic meter of the composite material is prepared from raw materials containing the following mass contents:

[0032]

[0033]

[0034] The raw materials for preparing the composite material of the present invention contain 600-700 kg of Portland cement per cubic meter, preferably 630-670 kg, and more preferably 650-660 kg; the Portland cement is preferably P.O42.5 ordinary Portland cement.

[0035] The raw materials for preparing the composite material of the present invention contain 580-650 kg of mineral powder per cubic meter, preferably 600-630 kg, and more preferably 615-620 kg; the mineral powder is preferably S95 grade mineral powder.

[0036] The raw materials for preparing the composite material of the present invention contain 300-600 kg of coral sand per cubic meter, preferably 400-480 kg, and more preferably 440-450 kg; the particle size of the coral sand is preferably ≤2.36 mm, more preferably ≤2.06 mm, and even more preferably ≤2.00 mm.

[0037] The raw materials for preparing the composite material of the present invention contain 300-600 kg of coral sand per cubic meter, preferably 400-475 kg, and more preferably 440-450 kg.

[0038] The raw materials for preparing the composite material of the present invention contain 5 to 8 kg of water reducer per cubic meter, preferably 6 to 7 kg, and more preferably 6.3 to 6.5 kg; the water reducer is preferably a polycarboxylate water reducer.

[0039] The raw materials for preparing the composite material of the present invention contain 5×10 -3 ~10×10 -3 kg steel fiber (SF), preferably 8×10 -3 ~9×10 -3 kg, more preferably 8.03×10 -3 ~8.5×10 -3 kg.

[0040] In the present invention, the length of the steel fiber is 10 to 15 mm, preferably 12 to 13 mm; the diameter is 0.1 to 0.3 mm, preferably 0.2 mm.

[0041] The raw materials for preparing the composite material of the present invention contain 1.5×10 -4 ~2×10 -4 kg polypropylene fibers, preferably 1.8 × 10 -4 ~1.9×10 -4 kg, more preferably 1.85×10 -4 ~1.87×10 -4 kg.

[0042] In the present invention, the polypropylene fiber has a length of 4 to 8 mm, preferably 5 to 7 mm, and more preferably 6 mm; and a diameter of 0.02 to 0.03 mm, preferably 0.024 to 0.026 mm.

[0043] The present invention also provides a method for preparing the composite material, comprising the following steps:

[0044] (1) mixing silicate cement, mineral powder and coral sand to obtain a first mixture;

[0045] (2) mixing the obtained first mixture with the first portion of seawater to obtain a second mixture;

[0046] (3) mixing the obtained second mixture with steel fiber and polypropylene fiber to obtain a third mixture;

[0047] (4) mixing the obtained third mixture with a water reducer and the remaining seawater to obtain a fourth mixture;

[0048] (5) The fourth mixed material is subjected to environmental curing and seawater curing in sequence to obtain a composite material.

[0049] In the present invention, the mixing in step (1) can be carried out in a blender, and the stirring speed during the mixing process is preferably 140 to 285 r / min, more preferably 180 to 240 r / min; the mixing time is preferably 1 to 3 min, more preferably 2 min.

[0050] In the present invention, the mixing in step (2) can be carried out in a blender, and the stirring speed during the mixing process is preferably 140 to 285 r / min, more preferably 180 to 240 r / min; the mixing time is preferably 1 to 4 min, more preferably 2 to 3 min.

[0051] In the present invention, the mixing process in step (3) is to slowly and evenly sprinkle the steel fiber and the polypropylene fiber during the stirring process; the mixing time is preferably 1 to 4 minutes, more preferably 2 to 3 minutes.

[0052] In the present invention, the mixing in step (4) can be carried out in a blender, and the stirring speed of the mixing process is preferably 140 to 285 r / min, more preferably 180 to 240 r / min; the mixing time is preferably 1 to 4 min, more preferably 2 to 3 min.

[0053] In the present invention, step (5) is firstly formed, poured into a trial mold and vibrated and leveled, and then environmental curing and seawater curing are carried out in sequence.

[0054] In the present invention, the temperature of the environmental curing is 18-23° C., preferably 20-21° C.; the humidity is 93-98%, 95-96%; and the time is 20-30 hours, preferably 24-26 hours.

[0055] In the present invention, the seawater curing is curing by immersing in seawater, and the curing time is 25 to 30 days, preferably 26 to 28 days.

[0056] In the present invention, the mass ratio of the first portion of seawater to the remaining portion of seawater is (85-95):(5-15), preferably (88-93):(7-12), and more preferably 90:10.

[0057] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0058] Example 1

[0059] Table 1 Parameters and quality of raw materials used in Example 1

[0060]

[0061]

[0062] The seawater used in this example was artificially prepared according to ASTM D1141-98 standard.

[0063] Table 2 Performance parameters of the slag powder (S95 grade granulated blast furnace slag powder) described in Example 1

[0064]

[0065] Table 3 Composition parameters of the slag powder (S95 grade granulated blast furnace slag powder) described in Example 1

[0066]

[0067] Preparation process:

[0068] (1) Dry material premixing: Add the weighed cement, mineral powder and coral sand into the mixer and dry mix for 2 minutes;

[0069] (2) Add liquid and stir: Add 90% artificial seawater and continue wet mixing for 2 minutes;

[0070] (3) Adding fibers: slowly and evenly sprinkle steel fibers and PP fibers into the mixture during stirring, and then stir for 2 minutes;

[0071] (4) Water replenishment and water reducing agent: Add the remaining artificial seawater and water reducing agent and continue stirring for 3 minutes;

[0072] (5) Forming and curing: Pour into the test mold and vibrate and smooth it, place it in an environment of 20℃ and 95% humidity for curing for 24 hours, remove it from the mold, and transfer it to artificial seawater for further curing for 28 days.

[0073] Experimental test:

[0074] To verify the mechanical properties of the composite materials, mixed materials (Examples 1, 2, and 3) and a control group (no fiber) were prepared. Aside from the type and amount of fiber incorporated, all other technical conditions remained consistent with those of Example 1. Standard compressive strength tests, splitting tensile tests, and stress-strain analysis were also conducted. Some representative data are as follows:

[0075] Table 4 Static compressive strength test (28 days, unit: MPa)

[0076]

[0077] Table 5 Splitting tensile strength (28 days, unit: MPa)

[0078]

[0079] As can be seen from the above examples, the present invention utilizes coral sand as fine aggregate, seawater as the mixing fluid, a polycarboxylate superplasticizer, and the simultaneous introduction of steel fiber and polypropylene fiber to form a multi-dimensional reinforcement synergistic mechanism. By optimizing the blending ratio of the various fibers, the compressive strength, splitting tensile strength, and post-peak toughness of the composite material can be significantly improved. The type and amount of fiber both affect the performance of the composite material, and the amount of fiber used is not necessarily better; it needs to be appropriately added.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A mixed fiber seawater coral sand engineering cement-based composite material, characterized in that: Each cubic meter of composite material is prepared from raw materials containing the following mass contents:

2. The composite material according to claim 1, characterized in that The Portland cement comprises P.O42.5 ordinary Portland cement; The mineral powder comprises S95 grade mineral powder; The particle size of the coral sand is ≤2.36 mm.

3. The composite material according to claim 1, characterized in that The steel fiber has a length of 10 to 15 mm and a diameter of 0.1 to 0.3 mm; The polypropylene fiber has a length of 4 to 8 mm and a diameter of 0.02 to 0.03 mm.

4. The composite material according to claim 1, characterized in that The water reducer comprises a polycarboxylate water reducer.

5. The composite material according to any one of claims 1 to 4, characterized in that Each cubic meter of composite material is prepared from raw materials containing the following mass contents:

6. The method for preparing the composite material according to any one of claims 1 to 5, characterized in that: The following steps are included: (1) mixing silicate cement, mineral powder and coral sand to obtain a first mixture; (2) mixing the obtained first mixture with the first portion of seawater to obtain a second mixture; (3) mixing the obtained second mixture with steel fiber and polypropylene fiber to obtain a third mixture; (4) mixing the obtained third mixture with a water reducer and the remaining seawater to obtain a fourth mixture; (5) The fourth mixed material is subjected to environmental curing and seawater curing in sequence to obtain a composite material.

7. The preparation method according to claim 6, characterized in that The mass ratio of the first part of seawater to the remaining part of seawater is (85-95):(5-15).

8. The preparation method according to claim 6 or 7, characterized in that The environmental curing temperature is 18-23° C., the humidity is 93-98%, and the time is 20-30 hours.

9. The preparation method according to claim 8, characterized in that The seawater curing is performed by immersing the product in seawater for 25 to 30 days.

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