CN112279591A

CN112279591A - Cement-based concrete plate with high early strength and preparation method thereof

Info

Publication number: CN112279591A
Application number: CN202011203800.5A
Authority: CN
Inventors: 李智鸿; 蔡海峰; 钟保民
Original assignee: Foshan Dongpeng Ceramic Co Ltd; Foshan Dongpeng Ceramic Development Co Ltd; Guangdong Dongpeng Holdings Co Ltd
Current assignee: Foshan Dongpeng Ceramic Co Ltd; Foshan Dongpeng Ceramic Development Co Ltd; Guangdong Dongpeng Holdings Co Ltd
Priority date: 2020-11-02
Filing date: 2020-11-02
Publication date: 2021-01-29
Anticipated expiration: 2040-11-02
Also published as: CN112279591B

Abstract

The invention discloses a cement-based concrete board with high early strength and a preparation method thereof, wherein the board comprises the following raw materials in parts by weight: 200 portions of ordinary Portland cement, 100 portions of ordinary quartz and 180 portions of fused quartz, and 5-15 portions of fused quartz. The preparation method comprises the following steps: (1) uniformly mixing the raw materials according to the formula amount to obtain slurry; (2) pouring the slurry into a mold, and demolding after curing to obtain a concrete slab; (3) steam pressure curing; (4) curing for 2 days to obtain a molded product. A small amount of fused quartz is used as an additive in the formula, so that the early strength of the concrete plate is effectively improved, the later strength of the concrete plate is improved, the metal piece is not corroded, and the metal piece can have a longer service life.

Description

Cement-based concrete plate with high early strength and preparation method thereof

Technical Field

The invention relates to the technical field of concrete plates, in particular to a cement-based concrete plate with high early strength and a preparation method thereof.

Background

Concrete members are applied to infrastructure construction, and metal parts are often embedded in the concrete members so as to facilitate application. Generally, concrete members require high early strength to achieve good application effects, while concrete plates have higher requirements for early strength.

In the prior art, the early strength of the concrete plate is improved by adding an early strength agent into a formula. The early strength agent is of chloride, sulfate, organic amine and the like, and has the defects of late expansion cracking and unobvious effect of corroding the embedded metal piece and the concrete plate respectively. Especially common chlorates exist chloride ions after being doped into concrete, which causes the corrosion of embedded metal parts such as reinforcing steel bars, shortens the service life of concrete plates and causes the later cracking of concrete. Meanwhile, the early strength agent only has a function of improving the early strength of the concrete plate, but has no function on the later strength.

In view of the above, there is a need for a concrete slab with high early strength and no corrosion to metal parts.

Disclosure of Invention

The invention aims to provide a cement-based concrete plate with high early strength and a preparation method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a cement-based concrete plate with high early strength comprises the following raw materials in parts by weight: 200 portions of ordinary Portland cement, 100 portions of ordinary quartz and 180 portions of fused quartz, and 5-15 portions of fused quartz.

Further, 100-180 parts of the common quartz comprises 10-20 parts of 40-70 mesh common quartz, 20-50 parts of 80-100 mesh common quartz, 50-80 parts of 325 mesh common quartz and 20-30 parts of 1000 mesh common quartz.

Further, the particle size of the fused silica is 1000-3000 meshes.

Furthermore, the raw materials in parts by weight also comprise 1-4 parts of water reducing agent, 0.1-0.4 part of hydroxypropyl methyl cellulose, 0.5-1 part of defoaming agent and 0.05-0.1 part of thixotropic lubricant.

The preparation method of the cement-based concrete plate with high early strength comprises the following steps:

(1) uniformly mixing the raw materials according to the formula amount to obtain slurry;

(2) pouring the slurry into a mold, and demolding after curing to obtain a concrete slab;

(3) placing the concrete slab in the step (2) into an autoclave, and keeping the temperature and the pressure constant for 8-13 hours under the conditions that the pressure in the autoclave is 0.8-1.2MPa and the temperature is 155 ℃;

(4) and (4) curing the concrete plate subjected to the step (3) for 2 days to obtain a molded product.

Further, in the step (2) and the step (4), the curing conditions are as follows: the temperature is 18-22 ℃, and the relative humidity is 94-96%.

Further, in the step (3), the internal pressure of the autoclave is gradually increased to 0.8-1.2MPa within 50-70min, and the temperature is increased to 145-155 ℃.

Further, in the step (3), the internal pressure of the autoclave is reduced to be less than or equal to 0.1MPa after 200min, and the temperature is reduced to room temperature.

Further, the method also comprises a step (5) after the step (4): immersing half of the molded product in water under the environment with the temperature of 20 ℃ and the relative humidity of 50%, and continuously maintaining for 6-10 days.

The invention has the beneficial effects that:

in the formula of the cement-based concrete plate, a small amount of fused quartz is added, and the small amount of fused quartz is used as an additive, so that the early strength of the concrete plate is effectively improved. The small amount of fused quartz replaces an early strength agent, so that the early strength of the concrete plate can be improved, and the later strength of the concrete plate can be improved. When the metal piece is pre-buried in the concrete plate according to production needs, the concrete slurry with the fused quartz does not corrode the metal piece, and the metal piece can have a long service life.

Detailed Description

The technical solution of the present invention will be further described with reference to the accompanying embodiments.

Fused silica is an amorphous glass phase substance formed by forming liquid silica at a very high temperature and then cooling instantaneously, has a large internal stress and is chemically active. According to the invention, the fused quartz is added into the formula of the concrete plate, the chemical activity of an amorphous mechanism of the fused quartz is utilized, under the high-temperature and high-pressure curing condition, active silicon-oxygen bonds in the fused quartz acquire energy and react with alkaline substances in cement to form a silicon-calcium compound, so that the binding power is increased, a continuous net-shaped framework is further generated, and the early flexural strength of the concrete plate can be effectively improved.

On the other hand, the alkali substances in the cement chemically react with the fused silica to produce a gel substance, and the gel substance absorbs water and undergoes volume expansion. The early cement structure is still not firm, the volume is still unstable, can expand in a certain range and does not crack, and at the moment, the alkaline substance reacts with fused silica to increase the cohesive force, and although the whole volume of the concrete is increased, the concrete is not cracked. However, when the concrete structure is fixed, if the alkalinity is too high (the amount of cement used is too large), the gel-forming substance absorbs water and swells, so that the matrix cracks.

Further, 100-180 parts of common quartz comprises 10-20 parts of 40-70 mesh common quartz, 20-50 parts of 80-100 mesh common quartz, 50-80 parts of 325 mesh common quartz and 20-30 parts of 1000 mesh common quartz.

The common quartz with various particle sizes is adopted, so that a better particle tight packing effect can be achieved, and the strength of the plate is further improved. The 40-70 mesh common quartz is common quartz containing quartz particles with different sizes within the particle size range of 40-70 meshes. Correspondingly, 20-50 parts of 80-100 mesh common quartz, 50-80 parts of 325 mesh common quartz and 20-30 parts of 1000 mesh common quartz refer to common quartz containing quartz particles with different sizes in the particle size range. The size of ordinary quartz is set like this, further makes the granule reach better close packing effect.

Furthermore, the particle size of the fused silica is 1000-3000 meshes. The fused quartz particles with smaller particle size are adopted, and the fused quartz particles have larger contact area with cement, so that the fused quartz particles and the cement react more fully. Preferably, the fused silica has a particle size of one or more of 1000 mesh, 2000 mesh and 3000 mesh, and more preferably, the fused silica has a particle size of 2000 mesh.

By adding the additive into the formula, the concrete slurry has better performances such as fluidity, suspension property, water retention property and the like, and the strength of the plate is improved.

In the preparation method, based on the formula of the cement-based concrete plate with high early strength, the autoclaved curing conditions are 0.8-1.2MPa and 145-155 ℃, so that the fused quartz and the cement can be subjected to full reaction.

By adopting reasonable temperature rise and pressure rise time, the reaction speed in the concrete slab uniformly rises, and the phenomenon that the strength of the plate is reduced due to overlarge local stress caused by overlarge reaction is avoided.

Further, in the step (3), the internal pressure of the autoclave is reduced to be less than or equal to 0.1MPa and the temperature is reduced to room temperature within 200 min.

At cooling step-down in-process, the concrete slab cooling is the desiccation, and concrete slab is comparatively fine and close, sets up longer cooling step-down process, can avoid this in-process concrete slab to lead to the production of crazing line because of the cooling is the desiccation too fast, is favorable to simultaneously evaporating the further exchange reaction of in-kettle concrete slab and steam, improves rupture strength.

Further, step (5) is included after step (4): immersing half of the molded product in water under the environment with the temperature of 20 ℃ and the relative humidity of 50%, and continuously maintaining for 6-10 days. At this time, the cement hydration reaction is basically finished, and the cement has stable flexural strength.

The invention is further illustrated by the following examples and comparative examples.

Example group A

The preparation method of the cement-based concrete plate with high early strength in the group of the embodiment comprises the following steps:

(2) pouring the slurry into a mold, wherein the curing conditions are as follows: maintaining at 20 deg.C and relative humidity of 95%, and demolding to obtain concrete slab;

(3) putting the concrete plate obtained in the step (2) into an autoclave, enabling the air pressure in the autoclave to gradually rise to 1MPa within 60min, enabling the temperature to rise to 150 ℃, keeping the temperature and the pressure constant for 10 hours under the conditions of 1MPa and 150 ℃ in the autoclave, reducing the air pressure in the autoclave to be less than or equal to 0.1MPa within 180min, and reducing the temperature to room temperature;

(4) and (4) curing the concrete slab subjected to the step (3) for 2 days under the following curing conditions: the temperature was 20 ℃ and the relative humidity was 95%, to obtain a molded article.

(5) Half of the molded article was immersed in water under an environment of 20 ℃ and 50% relative humidity, and curing was continued for 7 days.

The formulation in parts by weight of the early strength cementitious concrete panels of this example group is shown in the following table.

Raw materials	Example A1	Example A2	Example A3	Example A4	Example A5
						Ordinary portland cement	200	100	170	150	130
40-70 mesh common quartz	10	20	15	12	17
						80-100 mesh common quartz	50	45	20	40	30
325 mesh common quartz	50	80	75	65	55
						1000 mesh common quartz	25	20	30	26	28
Fused quartz	15	5	10	7	13
						Water reducing agent	3	1	4	3	3
Hydroxypropyl methylcellulose	0.4	0.1	0.2	0.3	0.2
						Defoaming agent	0.8	1	0.5	0.6	0.9
Redispersible latex powder	0.1	0.05	0.08	0.02	0.06
						Water (W)	40	20	60	30	40

Among them, the fused silica of example A1 had a particle size of 1000 mesh, the fused silica of examples A2 and A3 had a particle size of 2000 mesh, and the fused silica of examples A4 and A5 had a particle size of 3000 mesh.

Testing the bending strength of the concrete plate prepared according to the formula according to the testing method 2 part of the GB _ T35160.2-2017 synthetic stone, and carrying out an early bending strength test and a finished product bending strength test, wherein the early bending strength test is carried out on the concrete plate subjected to the step (4), and the finished product bending strength test is carried out on the concrete plate subjected to the step (5); and (5) observing whether obvious cracks appear on the surface of the concrete plate after the step (5) is finished and whether efflorescence exists on the surface. The results are shown in the following table.

Item	Example A1	Example A2	Example A3	Example A4	Example A5
						Early flexural strength MPa	15.65	14.33	15.92	15.23	15.62
Finished product breaking strength MPa	17.25	17.23	17.79	17.36	17.42
						Presence or absence of efflorescence on the surface of the sheet	Is free of	Is free of	Is free of	Is free of	Is free of
The finished product has no cracks	No obvious crack	No obvious crack	No obvious crack	No obvious crack	No obvious crack

Example group B

The following table shows the modification of the parameters of steps (2) to (5) of the preparation process of example group A using the formulation of example A1.

The concrete panels produced in this example were tested according to the test method of example group a for concrete panels, and the test results are shown in the following table.

Item	Example B1	Example B2	Example B3	Example B4
					Early flexural strength MPa	15.61	15.98	15.78	15.69
Finished product breaking strength MPa	17.62	17.83	17.75	17.69
					Presence or absence of efflorescence on the surface of the sheet	Is free of	Is free of	Is free of	Is free of
The finished product has no cracks	No obvious crack	No obvious crack	No obvious crack	No obvious crack

Comparative example group A

The amounts of ordinary quartz and fused silica were adjusted based on the formulation of example a3 using the preparation method of example group a, and the formulation in parts by weight of the cement-based concrete slab of this comparative example group is shown in the following table.

Raw materials	Comparative example A1	Comparative example A2	Comparative example A3	Comparative example A4	Comparative example A5
						Ordinary portland cement	170	170	170	170	170
40-70 mesh common quartz	15	15	15	25	5
						80-100 mesh common quartz	20	20	20	20	15
325 mesh common quartz	75	75	75	40	90
						1000 mesh common quartz	30	30	30	15	40
Fused quartz	10	18	50	10	10
						Water reducing agent	4	4	4	4	4
Hydroxypropyl methylcellulose	0.2	0.2	0.2	0.2	0.2
						Defoaming agent	0.5	0.5	0.5	0.5	0.5
Redispersible latex powder	0.08	0.08	0.08	0.08	0.08
						Water (W)	60	60	60	60	60

Of these, the comparative example No. A1 used fused silica having a particle size of 800 mesh.

Item	Comparative example A1	Comparative example A2	Comparative example A3	Comparative example A4	Comparative example A5
						Early flexural strength MPa	15.02	15.44	15.68	15.22	15.13
Finished product breaking strength MPa	17.53	17.22	17.87	16.91	16.95
						Presence or absence of efflorescence on the surface of the sheet	Is free of	Is provided with	Is provided with	Is free of	Is free of
The finished product has no cracks	No obvious crack	No obvious crack	No obvious crack	No obvious crack	No obvious crack

As can be seen from the above table, when the size of the fused silica grains is increased, the early flexural strength is reduced because the reaction speed with cement is reduced after the fused silica grains are increased, and the early flexural strength cannot be completely reacted, while the plate material achieves better flexural strength after the reaction is continued at the later stage, which means that the better early flexural strength can be achieved as the grains of the fused silica are smaller. When the addition amount of fused silica is increased, the strength of the plate is not greatly changed, and the phenomenon of saltpetering occurs. When the amount of the general quartz is changed, the strength of the plate is decreased due to the decrease in the particle packing density.

Comparative example group B

The parameters of step (3) were adjusted using the formulation of example a3 based on the preparation of example group a, as shown in the table below.

Item	Comparative example B1	Comparative example B2	Comparative example B3	Comparative example B4
					Early flexural strength MPa	14.71	16.01	14.74	15.62
Finished product breaking strength MPa	16.78	17.83	17.45	17.08
					Presence or absence of efflorescence on the surface of the sheet	Is free of	Is free of	Is provided with	Is free of
The finished product has no cracks	With obvious cracks	No obvious crack	No obvious crack	With obvious cracks

As can be seen from the above table, after the time for raising the temperature and raising the pressure and the time for lowering the temperature and lowering the pressure are shortened, the finished product has obvious cracks due to the excessively high change speed of the temperature and the air pressure in the autoclave; when the highest temperature and the highest pressure in the autoclave are reduced, incomplete reaction is caused, and the phenomenon of efflorescence occurs in the later period.

Comparative example C

The concrete plate formula of the comparative example adopts ordinary portland cement and the preparation method of the example group A, and the concrete plate formula of the comparative example comprises the following raw materials in parts by weight: 200 parts of ordinary portland cement, 10 parts of 40-70 mesh ordinary quartz, 50 parts of 70-100 mesh ordinary quartz, 50 parts of 325 mesh ordinary quartz, 25 parts of 1000 mesh ordinary quartz, 15 parts of 2000 mesh ordinary quartz, 3 parts of a polycarboxylic acid water reducing agent, 0.4 part of hydroxypropyl methyl cellulose, 0.8 part of a defoaming agent, 0.1 part of a thixotropic lubricant and 40 parts of water.

The early strength of the prepared concrete slab is 12.86MPa, the finished product strength is 15.62MPa, the finished product plate has no obvious crack, and the surface has no obvious efflorescence phenomenon.

The technical principle of the present invention is described above in connection with specific embodiments. The description is made for the purpose of illustrating the principles of the invention and should not be construed in any way as limiting the scope of the invention. Based on the explanations herein, those skilled in the art will be able to conceive of other embodiments of the present invention without inventive effort, which would fall within the scope of the present invention.

Claims

1. The cement-based concrete board with high early strength is characterized by comprising the following raw materials in parts by weight: 200 portions of ordinary Portland cement, 100 portions of ordinary quartz and 180 portions of fused quartz, and 5-15 portions of fused quartz.

2. The cement-based concrete panel with high early strength as recited in claim 1, wherein 100-180 parts of said ordinary quartz comprises 10-20 parts of 40-70 mesh ordinary quartz, 20-50 parts of 80-100 mesh ordinary quartz, 50-80 parts of 325 mesh ordinary quartz and 20-30 parts of 1000 mesh ordinary quartz.

3. The cement-based concrete panel with high early strength as recited in claim 1, wherein the fused silica has a particle size of 1000-3000 mesh.

4. The cement-based concrete slab with high early strength as claimed in claim 1, wherein the raw materials further comprise, in parts by weight, 1 to 4 parts of a water reducing agent, 0.1 to 0.4 part of hydroxypropyl methylcellulose, 0.5 to 1 part of a defoaming agent, and 0.05 to 0.1 part of a thixotropic lubricant.

5. A method of making a high early strength cementitious concrete panel as claimed in any one of claims 1 to 4 including the steps of:

6. The method according to claim 5, wherein in the steps (2) and (4), the curing conditions are as follows: the temperature is 18-22 ℃, and the relative humidity is 94-96%.

7. The production method according to claim 5, wherein in the step (3), the internal pressure of the autoclave is gradually increased to 0.8 to 1.2MPa and the temperature is increased to 145-155 ℃ over 50 to 70 min.

8. The preparation method as claimed in claim 5, wherein in the step (3), the internal pressure of the autoclave is reduced to less than or equal to 0.1MPa and the temperature is reduced to room temperature within 200 min.

9. The production method according to claim 5, further comprising step (5) after the step (4): immersing half of the molded product in water under the environment with the temperature of 20 ℃ and the relative humidity of 50%, and continuously maintaining for 6-10 days.