CN116589249A - Seawater and sand engineering cement-based composite material and preparation method thereof - Google Patents

Abstract

The application relates to a sea water and sea sand engineering cement-based composite material and a preparation method thereof, wherein the raw materials comprise 300-900 parts of cement, 300-900 parts of auxiliary gel material, 300-400 parts of sea water, 400-500 parts of sea sand, 1-10 parts of water reducer and 10-30 parts of fiber according to parts by weight; wherein the auxiliary gel material is one of fly ash or mineral powder. The cement-based composite material for the sea water and sea sand engineering has high toughness, high ductility and high durability, and can be used for practical engineering of offshore construction, cross-sea bridges and the like.

Description

Seawater and sand engineering cement-based composite material and preparation method thereof

technical field

The invention relates to the technical field of building materials, in particular to a cement-based composite material for seawater and sand engineering and a preparation method thereof.

Background technique

With the rapid development of marine engineering and coastal engineering construction, there are more and more island reefs and coastal engineering construction far away from land. Concrete with cement as the main cementitious material has developed into the building material with the largest amount and the widest range of use due to its abundant raw material sources, simple preparation process, low production cost, and stable mechanical properties. main building materials. However, with the continuous emergence of major engineering constructions, high-rise large-span, and important building structures with special functional requirements, the requirements for the mechanical properties and durability of concrete structures are also getting higher and higher. Therefore, higher strength of concrete materials and Better durability is a major requirement for the steady development of marine engineering. Although traditional concrete has good performance, it is brittle and prone to cracks under load. Harmful substances in the environment (CO ₂ , Cl ^- , SO ₄ ^2- , etc.) enter the interior of the concrete through the cracks and react with the concrete. , Damage to the internal structure of the concrete causes the cracks to gradually increase, resulting in structural damage. Especially in the marine environment, concrete will not only be exposed to harmful substances in the air, but also be eroded by the harsh environment unique to the ocean (wet-dry cycle, biofouling, seawater erosion, etc.).

Contents of the invention

The invention provides a cement-based composite material for seawater and sand engineering and a preparation method thereof. The desalinated seawater and sea sand can be used in building structures, and the sea water and sea sand can promote cement hydration and improve the early strength of concrete. Sea-sand engineering cement-based composite materials have the advantages of good compactness, good crack control ability and high durability, and solve the above-mentioned technical problems.

The solution of the present invention to solve the above-mentioned technical problems is as follows: a cement-based composite material for seawater and sand engineering (seawater and sea sand ECC), its raw materials include 300-900 parts by mass of cement, and 300-900 parts of auxiliary gel material , 300-400 parts of seawater, 400-500 parts of sea sand, 1-10 parts of superplasticizer, 10-30 parts of fiber;

Wherein, the auxiliary gel material is one of fly ash or mineral powder.

Preferably, its raw materials include 600 parts by mass of cement, 600 parts of auxiliary gel material, 360 parts of seawater, 432 parts of sea sand, 5.3 parts of water reducing agent, and 19.5 parts of fiber (that is, the fiber volume dosage is the concrete volume 1.5% of );

Wherein, the auxiliary gel material is one of fly ash or mineral powder.

Preferably, its raw materials include 600 parts by mass of cement, 600 parts of fly ash, 360 parts of seawater, 432 parts of sea sand, 5.3 parts of water reducing agent and 19.5 parts of fiber.

Preferably, its raw materials include 600 parts by mass of cement, 600 parts of mineral powder, 360 parts of seawater, 432 parts of sea sand, 5.3 parts of water reducing agent and 19.5 parts of fiber.

Preferably, the fly ash is primary fly ash with a density of 2.55g/cm ³ , a bulk density of 1.12g/cm ³ and a water content of 0.85%.

Preferably, the mineral powder is S95 mineral powder with a density of 2.9g/cm ³ and a specific surface area of 412m ² /g.

Preferably, the cement is grade P.O 42.5 ordinary Portland cement.

Preferably, the fibers are PVA fibers with a length of 12 mm and a diameter of 40 μm.

Preferably, the water reducer is polycarboxylate water reducer.

As mentioned above, the preparation method of seawater and sea sand engineering cement-based composite material comprises the following steps:

1) The raw materials will be measured according to the quality ratio for subsequent use;

2) Mix cement, auxiliary gel material and fine aggregate evenly, add gel material 1 and some fibers at the same time, stir for 1 minute to make it evenly mixed;

3) Mix the water reducer and water to obtain a mixed solution, pour part of the mixed solution into the mixture prepared in step 2), stir, then pour the rest of the mixed solution, stir for 1 minute to make it evenly mixed;

4) Stir continuously, add the remaining fibers to the mixture prepared in step 3), pour the test piece, and after demoulding and standard curing, the cement-based composite material for seawater and sea sand engineering of the present invention is obtained.

Preferably, the added amount of fibers is 1/2 of the total mass of fibers.

Preferably, the added amount of the mixed liquid is 1/2 of the total mass of the mixed liquid.

The beneficial effects of the present invention are as follows:

1. The present invention promotes the hydration of C ₃ A in the cement matrix through chloride ions in seawater, and improves the compressive strength of seawater sea sand ECC under long-term age compared with freshwater standard sand ECC. Substances that do not participate in the reaction, such as shells, inhibit the shrinkage of seawater and sea sand ECC.

2. By mixing fly ash and mineral powder, the present invention can not only be used as a gel material, but also reduce the amount of cement, reduce carbon emissions in the production process, and improve the flexural toughness and ductility of seawater and sea sand ECC.

3. The addition of PVA fiber in the invention makes seawater sea sand ECC have better tensile properties, bending properties, shear resistance and fatigue resistance than ordinary sea water sea sand concrete. The shear strength of seawater sea sand ECC with the same size is more than 40% higher than that of ordinary seawater sea sand concrete.

4. The undisturbed sea sand of the South China Sea used in the present invention reduces the exploitation of natural resources such as river sand, helps protect land resources, and promotes ecological protection.

In summary, the cement-based composite material for seawater and sand engineering provided by the present invention has high toughness, high ductility and high durability, and can be used in practical projects such as offshore buildings and sea-crossing bridges.

The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly and implement it according to the contents of the description, the preferred embodiments of the present invention and accompanying drawings are described in detail below. The specific embodiment of the present invention is given in detail by the following examples and accompanying drawings.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention. In the attached picture:

Fig. 1 is the broken line graph that comparative example 1 and embodiment 1-3 (W-F50, S-F25, S-F50, S-F75) sample compressive strength change with age;

Fig. 2 is the 7d, 28d line chart of embodiment 1-3 (S-F25, S-F50, S-F75) sample compressive strength;

Fig. 3 is the broken line graph that comparative example 1 and embodiment 4-6 (W-K50, S-K25, S-K50, S-K75) sample compressive strength change with age;

Fig. 4 is the 7d, 28d line chart of embodiment 4-6 (S-K25, S-K50, S-K75) sample compressive strength;

Fig. 5 is the broken line graph of embodiment 1-3 (S-F25, S-F50, S-F7) 5 sample bending toughness index;

Fig. 6 is the line graph of embodiment 4-6 (S-K25, S-K50, S-K75) sample bending toughness index;

Fig. 7 is the broken line graph that embodiment 1, comparative example 1 (W-K50, S-K50) sample drying shrinkage strain changes with curing age;

Fig. 8 is the broken line graph that embodiment 1-3 (S-F25, S-F50, S-F75) sample drying shrinkage strain changes with curing age;

Fig. 9 is a broken line graph of the drying shrinkage strain of samples of Examples 4-6 (S-K25, S-K50, S-K75) changing with curing age.

Detailed ways

The principles and features of the present invention are described below in conjunction with the accompanying drawings, and the examples given are only used to explain the present invention, and are not intended to limit the scope of the present invention.

In following each embodiment and comparative example, the raw material that adopts is as follows:

Sea sand is South China Sea sand.

The seawater is self-prepared seawater in the laboratory. The raw materials in the seawater are 24.5 parts by mass, NaCl 24.5 parts, NaSO ₄ 4.05 parts, KCl 0.7 parts, CaCl ₂ 1.2 parts, MgCl ₂ 6H ₂ O11.1 parts, NaHCO ₃ 0.201 copies.

The cement is grade P.O 42.5 ordinary Portland cement.

The water reducer is polycarboxylate water reducer.

Fiber is PVA fiber length 12mm, diameter 40μm

The standard sand is China ISO standard sand.

Fresh water was laboratory tap water.

The composition of fly ash and slag is shown in Table 1.

Table 1. Composition ratio of fly ash and mineral powder

The characterization methods and test specimen dimensions described in each of the following embodiments and comparative examples are as follows:

The size of the bending strength test specimen is 400mm in length, 100mm in width, and 15mm in thickness. A four-point bending test device is used. The span of the base branch is 300mm, and the span of the loading point at the top is 100mm.

The compressive strength refers to the specification GB/T 50081-2016 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The test specimen is a cube with a side length of 100mm, and the test instrument is a universal testing machine.

The calculation method of bending toughness test refers to the American toughness index method ASTM-C-1018.

For the test method of drying shrinkage and strain, refer to JC/T 603-2004 "Test Method for Drying Shrinkage of Cement Mortar", and the size of the test piece is a prism of 25mm*25mm*280mm.

Example 1

The fly ash dosage is 50% (the ratio of the fly ash quality and the gel material total mass) in the seawater sea sand ECC (marked as S-F50) provided in this example, and the PVA fiber dosage is 1.5% (PVA fiber volume to the total volume of concrete).

The preparation steps of seawater sea sand ECC are as follows:

(1) Weigh 600 parts of cement, 600 parts of fly ash, 360 parts of seawater, 432 parts of sea sand, 5.3 parts of water reducing agent, and 19.5 parts of PVA fiber by mass fraction;

(2) Add cement, fly ash, sea sand, and 1/2PVA fiber into the cement mortar mixing pot for stirring;

(3) Mix the water reducing agent and seawater in a container for weighing water, shake it evenly, and slowly pour the mixed solution into the stirring pot;

(4) Continue to stir, and at the same time add the remaining PVA fiber into the mixing pot evenly, pour it into the prepared test mold after stirring evenly, remove the mold after curing at room temperature for 1 day, and move it into the standard curing room for curing until testing age.

S-F50 sample characterization test results are as follows:

The 7-day, 28-day, 58-day, 88-day, 118-day, and 148-day compressive strengths are 30.51Mpa, 43.86MPa, 50.67MPa, 58.07MPa, 62.12MPa, and 63.85MPa, respectively.

The bending strength is 5.12Mpa, and the ultimate strength is 6.95MPa.

ECC flexural toughness I ₅ , I ₁₀ , and I ₂₀ are 4.909, 9.608, and 12.592, respectively.

The 5-day and 28-day drying shrinkage strains were 0.0408 and 0.095, respectively.

Example 2

The amount of fly ash in the seawater sea sand ECC (referred to as S-F25) provided in this example is 25%, and the amount of PVA fiber is 1.5%.

The raw materials and preparation steps used in this example are basically the same as in Example 1, except that 900 parts of cement and 300 parts of fly ash are weighed in parts by mass.

The characterization results of the S-F25 sample are as follows:

The 7-day, 28-day, 58-day, 88-day, 118-day, and 148-day compressive strengths are 36.33Mpa, 47.24MPa, 55.95MPa, 64.01MPa, 65.24MPa, and 66.12MPa, respectively.

The bending strength is 7.23Mpa, and the ultimate strength is 8.45MPa.

Bending toughness I ₅ and I ₁₀ are 4.38 and 7.171 respectively.

Example 3

In the seawater sea sand ECC (referred to as S-F75) provided in this example, the fly ash content is 25%, and the PVA fiber content is 1.5%.

The raw materials and preparation steps used in this example are basically the same as in Example 1, except that 300 parts of cement and 900 parts of fly ash are weighed in parts by mass.

The characterization results of the S-F75 sample are as follows:

The 7-day, 28-day, 58-day, 88-day, 118-day, and 148-day compressive strengths are 22.41MPa, 34.52MPa, 45.03MPa, 44.74MPa, 47.64MPa, and 49.35MPa, respectively.

The ECC flexural strength of the seawater sea sand is 3.67Mpa, and the ultimate strength is 5.00MPa.

The ECC flexural toughness I ₅ , I ₁₀ , and I ₂₀ of the seawater sea sand are 6.005, 11.684, and 14.760, respectively.

Example 4

In the seawater sand ECC provided in this example (marked as S-K50), the mineral powder content is 50%, and the PVA fiber content is 1.5%.

The raw materials and preparation steps used in this example are basically the same as in Example 1, except that the fly ash is replaced by mineral powder.

S-K50 sample characterization test results are as follows:

7 days, 28 days, 58 days, 88 days, 118 days, 148 days compressive strength are 45.95Mpa, 47.58MPa, 55.25MPa, 53.24MPa, 55.42MPa, 56.76MPa respectively.

The bending strength is 7.73Mpa, and the ultimate strength is 8.17MPa.

Bending toughness I ₅ , I ₁₀ , and I ₂₀ are 3.228, 5.596, and 6.657, respectively.

Example 5

In the seawater sea sand ECC (referred to as S-F25) provided in this example, the mineral powder content is 25%, and the PVA fiber content is 1.5%.

The raw materials and preparation steps used in this example are basically the same as those in Example 2, except that 900 parts of cement and 300 parts of mineral powder are weighed in parts by mass.

S-F25 sample characterization test results are as follows:

The 7-day, 28-day, 58-day, 88-day, 118-day, and 148-day compressive strengths are 50.81MPa, 52.24MPa, 52.95MPa, 51.54MPa, 53.45MPa, and 54.15MPa, respectively.

The bending strength is 8.31Mpa, and the ultimate strength is 9.94MPa.

Bending toughness I ₅ , I ₁₀ , and I ₂₀ are 2.587, 3.285, and 0, respectively.

Example 6

In the seawater sea sand ECC (referred to as S-F75) provided in this example, the mineral powder content is 75%, and the PVA fiber content is 1.5%.

The raw materials and preparation steps used in this example are basically the same as those in Example 2, except that 300 parts of cement and 900 parts of mineral powder are weighed in parts by mass.

The characterization results of the S-F75 sample are as follows:

The 7-day, 28-day, 58-day, 88-day, 118-day, and 148-day compressive strengths are 43.61Mpa, 44.79MPa, 49.79MPa, 51.98MPa, 52.46MPa, and 54.46MPa, respectively.

The bending strength is 5.84Mpa, and the ultimate strength is 6.97MPa.

Bending toughness I ₅ , I ₁₀ , and I ₂₀ are 4.767, 8.540, and 10.530, respectively.

Comparative example 1

In the cement-based composite material provided in this example (referred to as W-F50), the admixture of fly ash is 50%, and the admixture of PVA fiber is 1.5%.

The raw materials and preparation steps used in this example are basically the same as those in Example 2, except that seawater is replaced with fresh water, and sea sand is replaced with standard sand.

The characterization test results of the W-F50 sample are as follows:

The compressive strengths of 7 days, 28 days, 58 days, 88 days, 118 days and 148 days are 30.81MPa, 45.11MPa, 51.25MPa, 54.86MPa, 58.76MPa and 62.58MPa respectively.

The 5-day and 28-day drying shrinkage strains were 0.0564 and 0.144, respectively.

The raw material proportions of each embodiment and comparative example are arranged as shown in Table 1.

Each embodiment of table 1 and comparative example material proportioning

Figure 1 is a broken line diagram of the compressive strength of samples W-F50, S-F25, S-F50, and S-F75 changing with age. -F75 sample shows better compressive strength with the extension of age.

Figure 2 is the 7d and 28d line graphs of the compressive strength of S-F25, S-F50, and S-F75 samples. It can be seen that with the increase of fly ash content, the short-term test compressive strength decreases.

Figure 3 is a line graph of the compressive strength of W-K50, S-K25, S-K50, and S-K75 samples changing with age. Compared with the W-F50 sample not mixed with seawater and sea sand, the sample mixed with mineral powder The specimens showed worse compressive strength with the extension of age.

Figure 4 is the 7d and 28d line graphs of the compressive strength of S-K25, S-K50, and S-K75 samples. It can be seen that with the increase of the amount of mineral powder added, the compressive strength of the test decreases in a short period of time.

Figure 5 is a line graph of the flexural toughness index of S-F25, S-F50, and S-F75 samples. It can be seen that the flexural toughness index increases with the increase of the amount of fly ash added.

Figure 6 is a line graph of the flexural toughness index of samples S-K25, S-K50, and S-K75. It can be seen that the flexural toughness index increases with the increase of the amount of fly ash added.

Figure 7 is a line graph of the drying shrinkage strain of W-K50 and S-K50 samples changing with the curing age. Compared with the W-F50 sample not mixed with seawater and sea sand, the extension of S-F50 and samples with age, Exhibits a small drying shrinkage strain.

Figure 8 is a line graph of the drying shrinkage strain of samples S-F25, S-F50, and S-F75 changing with the curing age. It can be seen that the drying shrinkage strain becomes smaller as the amount of fly ash added increases.

Figure 9 is a line graph of the drying shrinkage strain of samples S-K25, S-K50, and S-K75 changing with the curing age. It can be seen that the drying shrinkage strain decreases with the increase in the amount of mineral powder added.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form; all those skilled in the art can smoothly implement the present invention as shown in the attached drawings and the above descriptions. However, any equivalent change, modification and evolution made by those skilled in the art without departing from the scope of the technical solution of the present invention by using the technical content disclosed above are all equivalent implementations of the present invention Example; at the same time, any modification, modification and evolution of any equivalent changes made to the above embodiments according to the substantive technology of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims (10)

1. A seawater sea sand engineering cement-based composite material is characterized in that its raw materials include 300-900 parts of cement, 300-900 parts of auxiliary gel material, 300-400 parts of seawater, and 400 parts of sea sand by mass parts. -500 parts, 1-10 parts of water reducer, 10-30 parts of fiber; Wherein, the auxiliary gel material is one of fly ash or mineral powder. 2. A kind of seawater sea sand engineering cement-based composite material according to claim 1, is characterized in that, its raw material comprises 600 parts in cement by mass fraction, 600 parts in auxiliary gel materials, 360 parts in seawater, 432 parts in sea sand parts, 5.3 parts of superplasticizer, 19.5 parts of fiber; Wherein, the auxiliary gel material is one of fly ash or mineral powder. 3. A cement-based composite material for seawater and sand engineering according to claim 1, wherein the fly ash is a first-grade fly ash with a density of 2.55g/cm ³ and a bulk density of 1.12g/cm ³ , the water content is 0.85%. 4. A cement-based composite material for seawater and sand engineering according to claim 1, wherein the mineral powder is S95 mineral powder with a density of 2.9g/cm ³ and a specific surface area of 412m ² /g. 5. A cement-based composite material for seawater and sand engineering according to claim 1, wherein the cement is P.O 42.5 grade ordinary Portland cement. 6 . The seawater and sand engineering cement-based composite material according to claim 1 , wherein the fibers are PVA fibers with a length of 12 mm and a diameter of 40 μm. 7. The seawater and sea sand engineering cement-based composite material according to claim 1, wherein the water reducer is polycarboxylate water reducer. 8. A preparation method according to any one of claims 1-7, comprising the steps of: 1) The raw materials will be measured according to the quality ratio for subsequent use; 2) Mix cement, auxiliary gel material and fine aggregate evenly, and add gel material 1 and some fibers at the same time; 3) Mix the water reducer and water to obtain a mixed solution, pour part of the mixed solution into the mixture prepared in step 2), stir, then pour the rest of the mixed solution, and stir; 4) Stir continuously, add the remaining fibers to the mixture prepared in step 3), pour the test piece, and after demoulding and standard curing, the cement-based composite material for seawater and sea sand engineering of the present invention is obtained. 9. A kind of cement-based composite material for seawater and sand engineering according to claim 8, characterized in that, in the step 2), the amount of fiber added is 1/2 of the total fiber mass. 10. A cement-based composite material for seawater and sand engineering according to claim 8, characterized in that, in the step 3), the amount of the mixed solution is 1/2 of the total mass of the mixed solution.