CN113105201A

CN113105201A - Concrete canvas for underwater environment service and preparation method thereof

Info

Publication number: CN113105201A
Application number: CN202110380574.6A
Authority: CN
Inventors: 陈惠苏; 王春霖
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2021-04-09
Filing date: 2021-04-09
Publication date: 2021-07-13
Anticipated expiration: 2041-04-09
Also published as: CN113105201B

Abstract

The invention discloses a concrete canvas for underwater environment service and a preparation method thereof, wherein the concrete canvas comprises a cement matrix and a three-dimensional spacing fabric for filling the cement matrix, the cement matrix consists of sulphoaluminate cement clinker and semi-hydrated gypsum, and the mass ratio of the sulphoaluminate cement clinker to the semi-hydrated gypsum is 75-90: 10 to 25. The preparation method comprises the steps of sieving the raw materials by a 100-mesh sieve, uniformly mixing, and then vibrating the uniformly mixed cement powder into the three-dimensional space fabric in several times until the three-dimensional space fabric is tightly filled and the cement powder cannot be refilled. The invention is suitable for underwater environment, in particular for water-saturated environment such as reservoir bottom, ditch substrate, ditch protection and the like. No bending cracking and good working performance. The high-strength concrete has good mechanical properties, the strength development is fast, the strength is stable within 5 days, and the strength is higher than that under the natural curing condition.

Description

Concrete canvas for underwater environment service and preparation method thereof

Technical Field

The invention belongs to a concrete canvas and a preparation method thereof, and particularly relates to a concrete canvas for underwater environment service and a preparation method thereof.

Background

The concrete canvas is a novel building material, has the advantages of fast condensation and hardening, high early strength, excellent shielding performance and wide application field, and can be used for slope protection, water pipes, ditch substrates, tents and the like.

Different humidity environments have a greater impact on the cement matrix. At present, much research on concrete canvas is conducted under natural dry curing (T20 ± 2 ℃ RH 60 ± 5%) conditions, and the amount of water involved in hydration is small, while the research on concrete canvas in humid environment, especially underwater environment is small. And part of the formula suitable for natural dry-state maintenance of the concrete canvas can be bent and cracked in an underwater environment, so that the concrete canvas loses the working performance, and therefore the concrete canvas suitable for the underwater environment needs to be researched, so that the concrete canvas can play an excellent role in water-saturated environments such as ditches, pool substrates, pipelines and the like. The performance of the common concrete canvas is greatly influenced by the watering amount, and the watering amount and the watering uniformity of the concrete canvas are controlled by the experience and proficiency of people. Therefore, an easy watering method is needed.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a concrete canvas which does not warp in the water environment; the second purpose of the invention is to provide a preparation method of the concrete canvas.

The technical scheme is as follows: the invention relates to a concrete canvas for underwater environment service, which comprises a cement matrix and a three-dimensional spacing fabric for filling the cement matrix, wherein the cement matrix consists of sulphoaluminate cement clinker and semi-hydrated gypsum, and the mass ratio of the sulphoaluminate cement clinker to the semi-hydrated gypsum is 75-90: 10 to 25.

Further, in the components, the sulphoaluminate cement clinker is formed by 725 sulphoaluminate cement cementing materials, wherein the mineral phase C in the sulphoaluminate cement clinker₄A₃50-80% of S, and a mineral phase beta-C₂The mass fraction of S is 5-30%, and the gypsum phase is not contained. Because of the special powder filling and water spraying forming mode of the concrete canvas, the concrete canvas has higher porosity than concrete which is formed by stirring under the same gel material mixing ratio. The higher porosity can therefore be compensated by the volume expansion produced by the formation of ettringite. By controlling the main mineral phase of the sulphate aluminum cement pure clinker to be

It can be compounded with gypsum to produce ettringite, which produces volume expansion to make up the pores of concrete canvas. A typical chemical reaction equation is shown in formula 1.

Furthermore, alpha-type semi-hydrated gypsum is adopted as the semi-hydrated gypsum, the natural alpha-type semi-hydrated gypsum is marked with alpha 40, and the specific surface area is about 565m²The content of the semi-hydrated gypsum is higher than 93 percent, the drying strength is higher than 30MPa, the dissolving process is quick, the hydration reaction is facilitated, the crystallization is good and firm, and the strength is high. It can be combined with

The mineral phase cement clinker reacts, the special effect of controlling the content of generated ettringite can be achieved by limiting the content of the components of the mineral phase cement clinker and the mineral phase cement clinker, so that the volume stability of the concrete canvas is different from that of the cement paste with the same proportion, and the generation amount of the ettringite can be controlled, so that the concrete canvas is still stable in volume and keeps the original working performance in the environment containing a large amount of water.

Further, the three-dimensional space fabric comprises a sparse weaving surface, space yarns and a dense weaving surface, wherein the sparse weaving surface, the space yarns and the dense weaving surface are all prepared from PET fibers; the spacing yarn is composed of warp yarns and weft yarns, two ends of the warp yarns and the weft yarns are respectively connected with the weaving surface and the weaving surface, specifically, the warp yarns and the weft yarns can be connected at a certain angle according to the weaving requirement of the fabric, and the spacing yarn is filled with a cement matrix. The thickness of the three-dimensional space fabric is 5-15 mm, the three-dimensional space fabric is soft and can be folded due to the control of the thickness, the storage and the transportation are convenient, square holes for the penetration of a cement matrix are formed in the sparse weaving surface, the square holes are beneficial to enabling cement powder to quickly vibrate into the three-dimensional space fabric, and compared with traditional round holes, the vibration-in efficiency of the powder can be greatly improved, the total content of the cement powder entering the three-dimensional space fabric is improved, and therefore the prepared concrete canvas is more compact and firm; the pore diameter of the dense weaving surface of the bottom surface is smaller than the average grain diameter of the cement powder so as to prevent the powder from leaking.

Furthermore, the upper part of the sparse weaving surface is provided with a gluing layer for sealing, and the specific sealant is waterproof and high-temperature-resistant PVC glue, so that the prepared concrete canvas further has the functions of corrosion prevention and water prevention.

The principle of the invention is as follows: the concrete canvas is generally cured naturally in a dry state, and the curing conditions are as follows: t20 ± 2 ℃ RH 60 ± 5%, however, as shown in formula 1, the amount of ettringite produced requires not only gypsum but also a sufficient amount of water. In a water body environment, the generation amount of ettringite in a system needs to be controlled due to water saturation, namely, the generation of proper expansion is controlled, the porosity is filled, and the mechanical property of the concrete canvas is improved. According to the invention, 725 sulphoaluminate cement cementing materials with specific mineral phase compositions are adopted and mixed with alpha-type semi-hydrated gypsum capable of reacting with the same, and the effect of preventing the concrete canvas from warping when used in an underwater environment is achieved by controlling the content of each raw material component; meanwhile, the three-dimensional spacer fabric has anisotropy, and the sparse weaving surface and the dense weaving surface as well as the limitation effect of the warp yarns and the weft yarns, so that the concrete canvas is further controlled not to warp by the three-dimensional spacer fabric under the internal stress generated when the ettringite grows and expands and the tension of the three-dimensional spacer fabric to the concrete canvas in different directions in the process of expanding the ettringite.

The invention also discloses a preparation method of the concrete canvas for the underwater environment service, which comprises the following steps;

(1) sieving the raw materials of the cement matrix by a 100-mesh sieve, and then placing the raw materials in a stirrer to stir at a low speed so as to fully mix the powdery raw materials;

(2) vibrating the mixed cement powder into the three-dimensional space fabric for several times until the three-dimensional space fabric is tightly filled;

(3) and coating PVC glue on the sparse weaving surface of the densely-filled three-dimensional space fabric to seal the cement powder, and preparing the concrete canvas.

Further, in the step (2), the three-dimensional spacing fabric is placed on a vibration table with adjustable vibration amplitude and vibration frequency, the vibration amplitude is adjusted from low to high along with the increase of the vibration frequency of the cement powder, and the vibration frequency is adjusted from high to low along with the increase of the vibration frequency of the cement powder; wherein the vibration amplitude is 0.7-0.8 mm, and the vibration frequency is 46-50 Hz. In the whole filling process, cement powder is uniformly paved on the surface of the three-dimensional space fabric as much as possible, higher frequency and lower amplitude are adopted when the cement powder just vibrates into the three-dimensional space fabric, the original frequency and amplitude filling efficiency is lower along with the gradual filling of the cement powder, and the frequency and amplitude are adjusted and the lower frequency and higher amplitude are adopted when the continuous filling cannot be carried out. The three-dimensional space fabric is used for smoothly discharging air in the three-dimensional space fabric, so that the cement powder is more densely filled.

Further, in the step (1), the low-speed stirring specifically includes: stirring for 15-25 min at a rotation speed of 135-145 r/min and a revolution speed of 57-67 r/min. The low-speed stirring is adopted here to prevent the powder from escaping while ensuring uniform stirring of the powder, and adversely affects the accuracy of the mixing ratio of the materials.

Further, when the three-dimensional fabric is actually used, the three-dimensional fabric is laid on a working surface, and water is sprayed until the concrete canvas is completely submerged into the water surface. If the cement powder is used in water-saturated environments such as the bottom of a reservoir and the substrate of a ditch, water can be directly injected, and the cement powder can be prevented from escaping only by preventing the water flow from impacting a certain part too much.

Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: (1) the cement matrix for the concrete canvas system suitable for the underwater environment can be prepared only by containing two components, so that the concrete canvas can be kept to be non-warped for a long time in the underwater environment, the requirement of adapting to the underwater environment is met, and the cement matrix is particularly suitable for water-saturated environments such as the bottom of a reservoir, a ditch substrate and a ditch protection; (2) the concrete canvas prepared by the invention has good mechanical property, the strength development is fast, the strength reaches stability in 5 days, the strength is higher than that under the natural curing condition, the 1d compressive strength of the prepared concrete canvas can reach more than 35MPa, and the 180d strength can reach more than 50 MPa.

Drawings

FIG. 1 is a schematic view showing that the concrete canvas prepared by the present invention is cured by soaking in water for 10d without warping;

FIG. 2 is a schematic diagram showing the warp of the concrete canvas prepared by the present invention after soaking and curing for 10 d;

FIG. 3 is a schematic structural view of a three-dimensional spacer fabric according to the present invention;

FIG. 4 is a schematic view of the solfration surface of FIG. 3;

FIG. 5 is a schematic view of the dense-woven side of FIG. 3.

Detailed Description

The technical solution of the present invention is further described in detail with reference to the accompanying drawings and examples.

The raw materials used in the following examples are all as follows:

the sulfoaluminate cement clinker used is numbered 72.5.

The sulphoaluminate cement mainly contains 59.8 percent of mass fraction

And 21.9 mass% of beta-C₂S。

The hemihydrate gypsum used is designated α 40.

Referring to fig. 3, the three-dimensional spacer fabric comprises a sparsely woven surface 1, spacer yarns 2 and a densely woven surface 3, wherein the sparsely woven surface 1, the spacer yarns 2 and the densely woven surface 3 are all made of PET fibers; the spacing yarns 2 are composed of warp yarns and weft yarns, two ends of the warp yarns and the weft yarns are respectively connected with the sparse weaving surface 1 and the dense weaving surface 3, the thickness of the used three-dimensional spacing fabric is 10mm, wherein, referring to fig. 4, the size of square holes 11 of the sparse weaving surface is 3.0mm x 2.5mm (the size of warp grids and the size of weft grids), and the dense weaving surface has no pores.

The water used meets the requirements of tap water of concrete water standard (JGJ 63-2006).

The glue used for gluing is PVC glue.

Test method

1) Weighing sulphoaluminate cement clinker and alpha 40 hemihydrate gypsum with different mass ratios respectively, sieving the sulphoaluminate cement clinker and the alpha 40 hemihydrate gypsum with a 100-mesh sieve, putting the raw materials into a stirrer, and stirring the raw materials for 20 minutes by a stirring blade at a rotation speed of 140 +/-5 r/min and a revolution speed of 62 +/-5 r/min so as to uniformly mix the raw materials;

2) cutting the three-dimensional space fabric into square blocks with the length, width and height of 160mm, 130mm and 10m, placing the square blocks into a triple-link die, placing the triple-link die on a vibrating table with adjustable amplitude frequency, vibrating uniformly mixed cement powder into the three-dimensional space fabric in several times, gradually increasing the amplitude from 0.7mm to 0.8mm along with the vibrating process, gradually decreasing the vibrating frequency from 50Hz to 46Hz until the three-dimensional space fabric is tightly filled and the cement powder cannot be refilled, and preparing the concrete canvas.

Two curing modes are adopted during specific use, and the curing modes comprise natural curing and water soaking curing.

For the natural curing samples, water was sprinkled until the water just soaked the back, and then transferred to an environment with T ═ 20 ± 2 ℃ RH ═ 60 ± 5% for curing.

For the sample of soaking water maintenance, put the sample into the case that the size is greater than the sample size, slowly to the incasement water injection, until the surface of water submerges concrete canvas and concrete canvas surface is more than 10mm apart from the surface of water, ambient temperature is that T ═ 20 +/-2 ℃.

12 groups of samples are prepared by the method, namely examples 1 to 12 respectively, and specific mixture ratio and performance parameters are shown in tables 1 and 2, wherein examples 1 to 5 are natural curing, and examples 6 to 12 are water soaking curing.

For the samples of example 5 and example 12, the surface of the hydrophobic surface is coated with PVC glue, and the other examples are not coated with glue.

Table 1 formulation and apparent density of the concrete canvas prepared in examples 1 to 12.

Table 2 compressive strength of the concrete canvas prepared in examples 1 to 12 in the thickness direction.

Comparing example 3 with example 5, it can be seen that the compressive strength of the concrete canvas is not greatly affected by the coating under the dry natural curing condition. It can be seen from examples 9 and 12 that the compressive strength of the concrete canvas is not greatly affected by the coating under the soaking curing condition. Therefore, when the glue coating does not disturb the arrangement of the cement matrix inside the concrete canvas, the influence of the glue coating on the compressive strength of the concrete canvas is small.

In the examples 1 to 10, no buckling cracking occurs, specifically referring to fig. 1, while in the example 11, buckling cracking occurs during curing for 10d, specifically referring to fig. 2, it can be found that when the gypsum content is too large, the volume expansion is too large, the concrete canvas is expanded and cracked, and the working performance is lost. Example 11 the compressive strength 5d reached the highest and decreased from 10d, which is closely related to the occurrence of buckling cracks during curing 10d, because the gypsum content was excessive, the water content was sufficient, the amount of generated ettringite was excessive, and the swelling amount was excessive, so that the concrete canvas was buckled and cracked.

Comparing examples 7-10 with example 6, it can be seen that the incorporation of the semi-hydrated gypsum during soaking and curing improves the compressive strength of the concrete canvas, wherein, compared with example 6, example 9 with the best strength improves the 1d strength by 42%, the 28d strength by 22% and the 180d strength by 25.7%. The reason is that the addition of the hemihydrate gypsum enables the sulphoaluminate cement to generate more ettringite phases, so that micro-expansion is generated, the pores in the concrete canvas are filled, and the porosity is reduced.

Comparing examples 1-4 with examples 6-10, it can be seen that the mechanical properties developed faster during soaking and curing, and the strength was higher. Among them, in example 9 in which the mechanical properties during curing with water were the best, the 28d strength was improved by 9% and the 180d strength was improved by 17.5% compared with example 3 in which the natural dry curing properties were the best. This is because the formation of ettringite depends on water, and the amount of water is sufficient during soaking and curing, so that more ettringite can be formed. Excessive ettringite can cause cracking, so that when the gypsum is soaked in water for curing, a small amount of gypsum can obtain enough swelling amount so as to fill up pores and obtain better mechanical property.

Comparative example 1

In order to explore the influence of the sulphoaluminate cement clinker with different mineral compositions on the mechanical property of the concrete canvas under the soaking curing condition, three different sulphoaluminate cements are selected.

Test group one: 725 sulphoaluminate cement cements: mainly containing 59.8% by mass

And 21.9 mass% of beta-C₂S, no gypsum phase.

Test group two: 725 quick hardening sulphoaluminate cement: mainly containing 37.6% by mass

18.8% by mass of beta-C₂S, 16.7 percent of gypsum by mass fraction.

Test group three: 825 high belite type sulphoaluminate cement: mainly containing 21.0 mass percent of

34.8% by mass of beta-C₂S。

The test method is as above, the sample is put into a box with the size larger than that of the sample, water is slowly injected into the box until the water surface submerges the concrete canvas and the surface of the concrete canvas is more than 10mm away from the water surface, the environmental temperature is T20 +/-2 ℃, three groups of comparison tests are respectively carried out, and the test method specifically refers to the table 3 and the table 4.

Table 3 three sets of comparative tests were performed to prepare the concrete canvas compositions and apparent densities.

Table 4 three sets of comparative tests were performed to prepare concrete canvas having compressive strength in the thickness direction.

Since test group three had the lowest

Mass fraction of

Hydration was faster and was the early strength-bearing phase, so test group three had the lowest strength at 1d, while test group three had the highest beta-C₂S, is a late strength-bearing phase, therefore even if

The content is less, the compression strength in the thickness direction of the test group III in 28d is higher than that of the test group II, and the test group II is lower

The compressive strength in the thickness direction is relatively low. And the strength of the test group I is the highest, which indicates that the formula modification is feasible under the water soaking curing.

Comparative example 2

The influence of different semi-hydrated gypsum on the mechanical property of the concrete canvas under the soaking curing condition is explored.

Test group one: alpha hemihydrate gypsum, designated by alpha 40, with specific surface area of 565m²/kg。

Test group two: alpha hemihydrate gypsum marked by alpha 60 and having a specific surface area of 136m²/kg。

Test group three: anhydrous gypsum, specific surface area 387m²/kg。

The test method is as above, the sample is put into a box with the size larger than that of the sample, water is slowly injected into the box until the water surface submerges the concrete canvas and the surface of the concrete canvas is more than 10mm away from the water surface, the environmental temperature is T20 +/-2 ℃, three groups of comparison tests are respectively carried out, and the test method specifically refers to tables 5 and 6.

Table 5 three sets of comparative tests were performed to prepare the concrete canvas compositions and apparent densities.

Table 6 three sets of comparative tests were performed to prepare concrete canvas having compressive strength in the thickness direction.

Comparing test group three and test group one, two respectively, the hemihydrate gypsum develops faster than the anhydrite strength, and the 28d strength is higher, so the concrete canvas is suitable for the hemihydrate gypsum. Comparing the first test group with the second test group, it was found that the strength of the first test group developed rapidly and the strength of the first test group was higher at 28d, which is probably because the α 40 of the first test group had a higher specific surface area than the α 60 of the second test group, and thus the specific surface area of the gypsum was crucial for the strength development of the concrete canvas.

Claims

1. The utility model provides a concrete canvas of environment in service under water, includes the cement base member and is used for filling the three-dimensional interval fabric of cement base member which characterized in that: the cement matrix consists of sulphoaluminate cement clinker and semi-hydrated gypsum, and the mass ratio of the sulphoaluminate cement clinker to the semi-hydrated gypsum is 75-90: 10 to 25.

2. The underwater in-service concrete canvas as claimed in claim 1, wherein: the sulphoaluminate cement clinker adopts 725 sulphoaluminate cement cementing materials, wherein the mineral phase C in the sulphoaluminate cement clinker₄A₃50-80% of S, and a mineral phase beta-C₂The mass fraction of S is 5-30%.

3. The underwater in-service concrete canvas as claimed in claim 1, wherein: the semi-hydrated gypsum adopts alpha-type semi-hydrated gypsum.

4. The underwater in-service concrete canvas as claimed in claim 1, wherein: the three-dimensional space fabric comprises a sparse weaving surface (1), space yarns (2) and a dense weaving surface (3); the spacing yarn (2) is composed of warp yarns and weft yarns, two ends of the warp yarns and the weft yarns are respectively connected with the sparse weaving surface (1) and the dense weaving surface (3), and a cement matrix is filled in the spacing yarn (2).

5. The underwater in-service concrete canvas as claimed in claim 4, wherein: the thickness of the three-dimensional spacer fabric is 5-15 mm, and square holes (11) for the penetration of a cement matrix are formed in the sparse weaving surface (1).

6. The underwater in-service concrete canvas as claimed in claim 4, wherein: and a glue coating layer (4) for sealing is arranged above the sparse weaving surface (1).

7. The underwater in-service concrete canvas as claimed in claim 4, wherein: the sparse weaving surface (1), the spacing yarns (2) and the dense weaving surface (3) are all made of PET fibers.

8. A method for preparing a concrete canvas for use in an underwater environment as claimed in any one of claims 1 to 3, comprising the steps of;

9. The method for preparing the concrete canvas for underwater environment service as claimed in claim 8, wherein: in the step (2), the three-dimensional spacer fabric is placed on a vibrating table with adjustable vibration amplitude and vibration frequency, the vibration amplitude is adjusted from low to high along with the increase of the vibration frequency of the cement powder, and the vibration frequency is adjusted from high to low along with the increase of the vibration frequency of the cement powder; wherein the vibration amplitude is 0.7-0.8 mm, and the vibration frequency is 46-50 Hz.

10. The method for preparing the concrete canvas for underwater environment service as claimed in claim 8, wherein: in the step (1), the low-speed stirring specifically comprises the following steps: stirring for 15-25 min at a rotation speed of 135-145 r/min and a revolution speed of 57-67 r/min.