CN115286309B

CN115286309B - Island ecological type high-strength high-ductility cement-based composite material and preparation method thereof

Info

Publication number: CN115286309B
Application number: CN202210716253.3A
Authority: CN
Inventors: 郭丽萍; 楚英杰
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2022-06-23
Filing date: 2022-06-23
Publication date: 2023-05-30
Anticipated expiration: 2042-06-23
Also published as: CN115286309A

Abstract

The invention discloses an island ecological type high-strength high-ductility cement-based composite material, which comprises the following components in mass: 100 parts of cement, 15-50 parts of coral micropowder or shell micropowder or sea sand micropowder, 15-50 parts of silica fume, 30-50 parts of water, 50-70 parts of fine sand, 2-4 parts of water reducer and 2-4 parts of fiber. The island ecological type high-strength high-ductility cement-based composite material prepared by the invention has the advantages of high strength, high toughness, high ductility and low cost, and has great application prospect in island engineering; the existing resource of the ocean island is utilized by local materials, so that the full gradient comprehensive utilization of the island building material resource is realized, and the cost of marine building materials is saved. Meanwhile, a novel treatment mode is provided for island micro powder with the particle size smaller than 75 mu m, the land space of the ocean island is widened, and the ecological construction of the ocean island is facilitated.

Description

Island ecological type high-strength high-ductility cement-based composite material and preparation method thereof

Technical Field

The invention belongs to the field of building materials, and particularly relates to an island ecological type high-strength high-ductility cement-based composite material and a preparation method thereof.

Background

The ocean island reef is lack of sand and stone resources, so that the construction of the ocean island reef by using coral (shell) aggregate is a necessary trend of island reef engineering construction. In order to reduce the sea transportation cost, natural coral sand and shell sand are used as fine aggregates in actual engineering, and coral (shell) coarse aggregates are also commonly crushed into coral fine aggregates for use. However, coral (shell) aggregate is porous and highly brittle, and a large amount of fine powder is produced in the crushing process. Since coral (shell) aggregates are too high in water absorption, the content of fine powder in coral (shell) sand is usually strictly limited, resulting in a large amount of coral fine powder or shell fine powder being discarded. At the same time, too fine sea sand fines are also faced with these conditions. This not only compresses the limited land resources of the island but also increases the economic cost of disposing of the waste. On the other hand, the harsh marine environment also presents a great challenge to marine concrete construction. The concrete structures on the island are not only subject to damage by various aggressive ions in the marine environment, but also subject to environmental loads such as sea wind load, sea wave load, ocean current load and the like. The severe service environment puts more severe durability demands on marine concrete.

The high-ductility cement-based composite material (High Ductility Cementitious Composites, HDCC) is a novel composite material which takes cement, mineral admixture, aggregate, fiber, additive and the like as raw materials, has uniaxial ultimate tensile strain of not less than 0.5 percent and has average crack width of not more than 200 mu m. HDCC also shows good application prospect in the field of marine concrete with advantages such as high ductility and excellent crack control ability. The current research results show that the durability of concrete structures can be greatly improved by using HDCC. However, HDCCs are generally low in strength and cannot meet the requirements of practical engineering on high-strength and high-ductility cement-based composite materials. Meanwhile, high-quality ground quartz sand is generally used for preparing the HDCC and a large amount of cement is needed, so that the HDCC has higher use cost, is unfavorable for the promotion of the current 'double carbon' policy, and further limits the popularization and application of the HDCC in ocean island reef engineering with deficient resources.

The prior research results show that the sea sand is used for successfully preparing the HDCC, but the results are simply replaced by using the sea sand to replace the ground quartz sand, and the prior resources are not fully utilized in the island reef environment. Secondly, the application of the prior patent such as CN202010384985.8 ' ultra-high performance concrete of sea water mixing and full coral aggregate ' and preparation method ' to coral (shell) sand or sea sand is limited to the part larger than 75 μm. In addition, there is a precedent that low-grade raw materials such as coral (shell) sand and coral (shell) micropowder are used for omnidirectionally replacing building raw materials (such as aggregate, cement, mineral admixture and the like) needing ocean transportation to prepare the high-strength high-ductility cement-based composite material with compressive strength of more than 100MPa, flexural strength of more than 40MPa and tensile strain of more than 10% in 15 days.

Disclosure of Invention

The invention aims to: the invention aims to provide an island ecological type high-strength high-ductility cement-based composite material (ECO-HSHDCC) suitable for island engineering and a preparation method thereof. The composite material uses solid wastes existing on ocean island reefs in a large amount: coral, shell and sea sand micropowder with particle diameter smaller than 75 μm. The method not only provides a new mode for processing the island micro powder, widens the land space of the ocean island, saves the cost of marine construction raw materials, but also prepares the ecological high-strength high-ductility cement-based composite material suitable for island engineering, has high strength, high toughness, high ductility and lower cost, is favorable for popularization of application in the field of the ocean island engineering, and is also suitable for the engineering large background of local material taking of the ocean island engineering.

The technical scheme is as follows: the island ecological type high-strength high-ductility cement-based composite material comprises the following components in mass: 100 parts of cement, 15-50 parts of coral micropowder or shell micropowder or sea sand micropowder, 15-50 parts of silica fume, 30-50 parts of water, 50-70 parts of fine sand, 2-4 parts of water reducer and 2-4 parts of fiber, wherein the particle size range of the coral micropowder or shell micropowder or sea sand micropowder is 10-75 mu m.

Further, the cement is ordinary Portland cement with a strength grade of 42.5 or 52.5; the silicon dioxide content in the silica fume is not less than 90%; the fine sand is common river sand, sea sand, coral sand or shell sand, the grain diameter is 0.075-0.6 mm, and the fineness modulus is 1.4-1.8; the water is seawater or fresh water.

Further, the coral micropowder or the shell micropowder or the sea sand micropowder is one or more of coral micropowder or shell micropowder or sea sand micropowder.

Further, the water reducer is a liquid or solid powder polycarboxylate water reducer.

Further, the length of the fiber is 8-12 mm, the equivalent diameter is 17-40 mu m, the elastic modulus is not lower than 30GPa, the tensile strength is not lower than 1200MPa, and the fiber type is one or more of polyvinyl alcohol fiber, polyethylene fiber, polypropylene fiber, modified polyester fiber or polyoxymethylene fiber.

The preparation method of the island ecological type high-strength high-ductility cement-based composite material comprises the following steps:

step 1, cement, coral micropowder or shell micropowder or sea sand micropowder, silica fume, a water reducing agent and fine sand are dry mixed in a mixer for 1-2 minutes;

step 2, adding water and stirring for 3-4 minutes;

step 3, adding fiber and stirring for 5-8 minutes;

and 4, installing the die, removing the die after the plastic is completely lost, and performing standard curing for 4 days after steam curing for 9 days at 85 ℃.

Further, the water reducer adopts a solid water reducer, and water is added after dry mixing in the step 1; if the liquid water reducer is adopted, the water reducer is uniformly mixed with the water in the step 2 and then stirred.

Further, the total plastic loss time of ECO-HSHDCC is 24 to 48 hours after the start of stirring.

Further, in the step 1, the rotation speed of the stirrer is 130-140 revolutions per minute; in the

steps

2 and 3, the rotation speed of the stirrer is 140-285 rpm.

The beneficial effects are that: compared with the prior art, the invention has the following remarkable advantages:

(1) The island ecological type high-strength high-ductility cement-based composite material prepared by the invention has the advantages of high strength, high toughness, high ductility and low cost, and has great application prospect in island engineering;

(2) The local materials are utilized to utilize the existing resources of the ocean island, so that the cost of marine building raw materials is saved.

(3) Provides a new treatment mode for island micro powder with the grain diameter smaller than 75 mu m, widens the land space of the ocean island, and is beneficial to the ecological construction of the ocean island.

Drawings

FIG. 1 is a 15-day compression flexural strength comparison for five groups of samples;

FIG. 2 is a uniaxial tensile stress-strain plot of five groups of samples;

FIG. 3 is a typical stretch-crack morphology for five groups of samples;

FIG. 4 is a macroscopic morphology of the sample of example 5 after fracture-resistant failure.

Detailed Description

The technical scheme of the invention is further described below with reference to the accompanying drawings.

Example 1:

the blending ratio of HSHDCC is shown in table 1 below:

TABLE 1HSHDCC mix ratio (mass portion ratio)

The cement is ordinary silicate cement with the strength grade of 52.5R, the silicon dioxide content in the silica fume is not less than 90 percent, the grain diameter of river sand is 0.075-0.6 mm, the fineness modulus is 1.45, and the fiber type is polyethylene fiber.

The preparation method comprises the following steps:

1) Dry mixing cement, limestone powder, silica fume, a water reducing agent and fine sand in a stirrer for 90 seconds, wherein the rotation frequency of a blade of the stirrer is 130 revolutions per minute;

2) Adding water and stirring for 3 minutes, wherein the rotation frequency of a blade of the stirrer is 285 rpm;

3) Adding fiber and stirring for 4 minutes, wherein the rotation frequency of a blade of a stirrer is 285 rpm;

4) And (3) die filling, removing the die after 48 hours, and performing standard curing for 4 days after steam curing for 9 days at 85 ℃.

The 15-day compressive strength is 114.4MPa, the flexural strength is 38MPa, and the uniaxial tensile strain is more than 3%.

Example 2:

the compounding ratios of the ECO-HSHDCC of the present invention are shown in Table 2 below:

TABLE 2ECO-HSHDCC mix ratio (mass portion ratio)

The cement is ordinary silicate cement with the strength grade of 52.5R, the silicon dioxide content in the silica fume is not less than 90 percent, the coral micropowder is obtained by crushing coral coarse aggregate and sieving the crushed coral micropowder to obtain 10-75 mu m coral micropowder, the grain size of river sand is 0.075-0.6 mm, the fineness modulus is 1.45, and the fiber type is polyethylene fiber.

The preparation method comprises the following steps:

1) Dry mixing cement, coral micropowder, silica fume, water reducing agent and river sand in a stirrer for 90 seconds, wherein the rotation frequency of a blade of the stirrer is 130 revolutions per minute;

The 15-day compressive strength is 111.4MPa, the flexural strength is 38.6MPa, and the uniaxial tensile strain is more than 6%.

Example 3:

the compounding ratios of the ECO-HSHDCC of the present invention are shown in Table 3 below:

TABLE 3ECO-HSHDCC mix ratio (mass portion ratio)

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The cement is ordinary silicate cement with the strength grade of 52.5R, the silicon dioxide content in the silica fume is not less than 90 percent, the sea sand micro powder is natural sea sand micro powder which is sieved to obtain sea sand micro powder with the diameter of 10-75 mu m, the particle size of coral sand is 0.075-0.6 mm, the fineness modulus is 1.45 (obtained by directional compounding of broken coral sand, the particle size ratio of each particle size is the same as that of river sand), and the fiber type is polyethylene fiber.

The preparation method comprises the following steps:

1) Dry mixing cement, sea sand micropowder, silica fume, water reducing agent and coral sand in a stirrer for 90 seconds, wherein the rotation frequency of a blade of the stirrer is 130 revolutions per minute;

The 15-day compressive strength is 112.8MPa, the flexural strength is 38.2MPa, and the uniaxial tensile strain is close to 5%.

Example 4:

the mixing ratio of the coral shell ECO-HSHDCC is shown in the following table 4:

TABLE 4 Shell coral ECO-HSHDCC mix ratio (mass portion ratio)

The cement is ordinary silicate cement with the strength grade of 52.5R, the silicon dioxide content in the silica fume is not less than 90 percent, the shell micro powder is the shell micro powder obtained by crushing shell coarse aggregate and sieving the crushed shell coarse aggregate, the particle size of coral sand is 0.075-0.6 mm, the fineness modulus is 1.45 (obtained by directional compounding of crushed coral sand, the particle size ratio of each particle size is the same as that of river sand), and the fiber type is polyethylene fiber.

The preparation method comprises the following steps:

1) Dry mixing cement, shell micropowder, silica fume, water reducing agent and coral sand in a stirrer for 90 seconds, wherein the rotation frequency of a blade of the stirrer is 130 revolutions per minute;

The 15-day compressive strength is 109.6MPa, the flexural strength is 39.8MPa, and the uniaxial tensile strain is more than 9%.

Example 5:

the blending ratio of the full coral ECO-HSHDCC of the present invention is shown in the following Table 5:

TABLE 5 full coral ECO-HSHDCC mix ratio (mass portion ratio)

The cement is ordinary silicate cement with the strength grade of 52.5R, the silicon dioxide content in the silica fume is not less than 90 percent, the coral micropowder is the coral micropowder with the diameter of 10-75 mu m obtained by crushing coral coarse aggregate and sieving, the particle size of the coral sand is 0.075-0.6 mm, the fineness modulus is 1.45 (obtained by directional compounding of crushed coral sand, the particle size ratio of each particle size is the same as that of river sand), and the fiber type is polyethylene fiber.

The preparation method comprises the following steps:

1) Dry mixing cement, coral micropowder, silica fume, water reducing agent and coral sand in a stirrer for 90 seconds, wherein the rotation frequency of a blade of the stirrer is 130 revolutions per minute;

The 15-day compressive strength is tested to be 107.2MPa, the flexural strength is tested to be 41.7MPa, and the uniaxial tensile strain is more than 10%.

Comparative example 1 and example 2 show that coral micropowder was used instead of the starting material for sea transport: after the limestone powder is used for preparing the HSHDCC, the 15-day compressive strength of the limestone powder is up to 111.4MPa, the flexural strength of the limestone powder is up to 38.6MPa, and the uniaxial tensile strain is more than 6%. The 15-day compressive strength was reduced by only 2.6% and the 15-day compressive strength was increased by 1.5% as compared with example 1 prepared using limestone powder, and the increase in uniaxial tensile strain was more than 100%. Therefore, the preparation of the HSHDCC by using coral micropowder instead of limestone powder is not only completely feasible, but also can greatly improve the uniaxial tension strain of the HSHDCC and greatly improve the ductility of the HSHDCC. In addition, the use of coral micropowder can reduce the transportation cost of the cementing material by 10-30%, so that the coral micropowder has multiple purposes.

Comparative example 1 and examples 3, 4, 5 show that sea sand micropowder and coral (shell) micropowder are used instead of the raw materials to be maritime: limestone powder and island ground materials are used: after the coral sand is used for preparing the HSHDCC, the compressive strength of the coral sand for 15 days is not greatly influenced, the flexural strength and the uniaxial tensile strain are greatly improved, and particularly the full coral ECO-HSHDCC prepared in the example 5 has the flexural strength of up to 41.7MPa for 15 days and the uniaxial tensile strain of more than 10%. It can be seen that the use of sea sand micropowder, coral (shell) micropowder and island reef sand (coral sand, shell sand, sea sand, etc.) to replace the raw materials needed for sea transportation in all directions is not only completely feasible, but also can greatly promote the uniaxial tensile strain of the HSHDCC and greatly promote the ductility thereof. Meanwhile, the ECO-HSHDCC prepared by using the island-reef ground material can reduce the total raw material transportation cost by about 50%, and has great economic benefit.

Claims

1. An island ecological type high-strength high-ductility cement-based composite material is characterized by comprising the following components in mass: 100 parts of cement, 15-50 parts of coral micropowder or shell micropowder, 15-50 parts of silica fume, 30-50 parts of water, 50-70 parts of fine sand, 2-4 parts of water reducer and 2-4 parts of fiber; the particle size range of the coral micropowder or the shell micropowder is 10-75 mu m; the fine sand is coral sand or shell sand, the grain diameter is 0.075-0.6 mm, and the fineness modulus is 1.4-1.8.

2. The island-reef ecological high-strength high-ductility cement-based composite material of claim 1, wherein the cement is ordinary portland cement having a strength grade of 42.5 or 52.5; the silicon dioxide content in the silica fume is not less than 90%; the water is seawater or fresh water.

3. The island-reef ecological high-strength high-ductility cement-based composite material of claim 1, wherein the water reducing agent is a liquid or solid powder polycarboxylate water reducing agent.

4. The island-reef ecological high-strength high-ductility cement-based composite material according to claim 1, wherein the fiber has a length of 8 to 12mm, an equivalent diameter of 17 to 40 μm, an elastic modulus of not less than 30GPa, a tensile strength of not less than 1200MPa, and the fiber type is one or more of polyvinyl alcohol fiber, polyethylene fiber, polypropylene fiber, modified polyester fiber, or polyoxymethylene fiber.

5. A method for preparing the island-reef ecological high-strength high-ductility cement-based composite material according to claim 1, comprising the following steps:

step 1, cement, coral micropowder or shell micropowder, silica fume, a water reducing agent and fine sand are dry mixed in a mixer for 1-2 minutes;

step 2, adding water and stirring for 3-4 minutes;

step 3, adding fiber and stirring for 5-8 minutes;

6. The method for preparing the island-reef ecological high-strength high-ductility cement-based composite material according to claim 5, wherein the water reducer adopts a solid water reducer, and water is added after dry mixing in the step 1; if the liquid water reducer is adopted, the water reducer is uniformly mixed with the water in the step 2 and then stirred.

7. The method for producing an island-reef-form high-strength high-ductility cement-based composite material according to claim 5, wherein the island-form high-ductility cement-based composite material has a total plastic loss time of 24 to 48 hours after the start of stirring.

8. The method for preparing an island-reef ecological high-strength high-ductility cement-based composite material according to claim 5, wherein in the step 1, the rotation speed of the stirrer is 130-140 revolutions per minute; in the steps 2 and 3, the rotation speed of the stirrer is 140-285 rpm.