CN112321211A

CN112321211A - Cement-based concrete plate adopting low-alkalinity cement and preparation method thereof

Info

Publication number: CN112321211A
Application number: CN202011203809.6A
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: 2021-02-05
Anticipated expiration: 2040-11-02
Also published as: CN112321211B

Abstract

The invention discloses a cement-based concrete plate adopting low-alkalinity cement and a preparation method thereof, wherein the cement-based concrete plate comprises the following raw materials in parts by weight: 100-200 parts of low-alkalinity cement, 80-140 parts of fused silica, 50-200 parts of common silica and 20-60 parts of water. The preparation method of the cement-based concrete plate adopting the low-alkalinity cement 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) and curing the concrete slab for 2 days to obtain a molded product. The fused quartz can improve the early strength of the plate, and also serves as a framework of concrete and has a function of improving the later strength. The use of the low-alkalinity cement avoids the phenomenon of the surface of the plate becoming efflorescent. The concrete slurry of the fused quartz does not corrode the metal piece, and the metal piece can have a longer service life.

Description

Cement-based concrete plate adopting low-alkalinity cement and preparation method thereof

Technical Field

The invention relates to the technical field of concrete plates, in particular to a cement-based concrete plate adopting low-alkalinity cement 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 adopting low-alkalinity cement and a preparation method thereof.

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

a cement-based concrete plate adopting low-alkalinity cement comprises the following raw materials in parts by weight: 100-200 parts of low-alkalinity cement, 80-140 parts of fused silica, 50-200 parts of common silica and 20-60 parts of water.

Further, 80-140 parts of the fused silica comprises 30-55 parts of 70-100 mesh fused silica, 40-60 parts of 120-200 mesh fused silica and 10-25 parts of 325 mesh fused silica.

Further, the particle size of the common quartz is 325 mesh.

Furthermore, the cement-based concrete plate also comprises 1-4 parts of water reducing agent, 0.1-0.4 part of hydroxypropyl methyl cellulose, 0.1-0.6 part of defoaming agent and 0.1-0.5 part of redispersible latex powder.

The preparation method of the cement-based concrete plate adopting the low-alkalinity cement 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 10-16 hours under the conditions of 1.2-1.4MPa in the autoclave and 185 ℃ of 175-;

(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 1.2-1.4MPa within 1.5-2.5 hours, and the temperature is increased to 175-185 ℃.

Further, in the step (3), the internal pressure of the autoclave is reduced to be less than or equal to 0.1MPa after 5-7 hours, and the temperature is reduced to room temperature.

Further, the method also comprises a step (5) after the step (4): and continuously maintaining the molded product for 50-60 days.

The invention has the beneficial effects that:

the cement-based concrete plate adopts low-alkalinity cement and fused quartz with a larger weight ratio in the formula, and the fused quartz can react with alkali in the cement to generate hydration products, so that the early strength of the plate is improved, and the fused quartz also serves as a skeleton of the concrete as aggregate. The alkalinity of the low-alkalinity cement is low, so that the alkalinity of the low-alkalinity cement can be completely consumed in the plate preparation process, and the phenomenon of surface efflorescence of the plate is avoided.

The alkaline substance reacts with the fused silica to increase the cohesive force in the early stage, so that although the whole volume of the concrete is increased, the concrete cannot crack, 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 longer service life.

Detailed Description

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

The invention provides a cement-based concrete plate adopting low-alkalinity cement, which comprises the following raw materials in parts by weight: 100-200 parts of low-alkalinity cement, 80-140 parts of fused silica, 50-200 parts of common silica and 20-60 parts of water.

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.

The cement-based concrete plate adopts low-alkalinity cement and fused quartz with a larger weight ratio in the formula, the fused quartz can react with alkali in the cement to generate hydration products, the early strength of the plate is improved, the fused quartz also serves as a skeleton of the concrete, on the other hand, in the traditional concrete, the reaction between the cement and the quartz is very little, and the binding power between the hydration products formed by adding water into the cement and the quartz is insufficient. And the alkalinity of the low-alkalinity cement is low, so that the alkalinity of the low-alkalinity cement can be completely consumed in the plate preparation process, and the phenomenon of surface efflorescence of the plate is avoided. Meanwhile, the board achieves better strength by controlling the weight ratio of the low-alkalinity cement to the molten use, when the use amount of the low-alkalinity cement is too small, the fused quartz is difficult to fully react to form a sufficient gel network structure, so that the overall strength of the board is not obviously increased; if the dosage of the low-alkalinity cement is too much, the alkalinity in the cement cannot be consumed as far as possible in the preparation process, and the residual alkali can continue to slowly react with fused quartz in the subsequent use, so that the efflorescence phenomenon occurs, and the quality stability of the concrete is not facilitated.

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 insecure, and the volume is still unstable, can expand in certain extent and not ftracture, utilizes alkaline material and fused silica to produce the reaction and increase the cohesive force this moment, and although the whole volume of concrete can increase, still can not ftracture, can improve the later stage intensity of concrete panel. 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, 80-140 parts of fused silica comprises 30-55 parts of 70-100 mesh fused silica, 40-60 parts of 120-200 mesh fused silica and 10-25 parts of 325 mesh fused silica.

The particle size of the fused quartz is set to be 70-100 meshes, 120-200 meshes and 325 meshes, so that the fused quartz can fully react with low-alkalinity cement, the autoclaved curing time in the preparation process is shortened, and the plate has better compactness. If the particle size of the fused quartz is large, the fused quartz is difficult to fully react with the low-alkalinity cement, and the alkalinity of the cement can be remained, so that the fused quartz continuously and slowly reacts with the fused quartz at a later stage, and the quality stability of the plate is influenced.

Further, the particle size of the ordinary quartz is 325 mesh. The common quartz with the particle size is matched with the fused quartz with the multi-stage particle size, so that the concrete raw materials can be tightly stacked, the arrangement of particles in the concrete plate is more uniform and compact, and the improvement of the overall strength is facilitated.

Furthermore, the cement-based concrete plate also comprises 1-4 parts of water reducing agent, 0.1-0.4 part of hydroxypropyl methyl cellulose, 0.1-0.6 part of defoaming agent and 0.1-0.5 part of redispersible latex powder. 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. The redispersible latex powder can improve the workability and the flow property of concrete slurry, increase the thixotropy and the anti-sagging property of the slurry, improve the cohesive force of the slurry, prolong the opening time of the slurry and enhance the water retention property of the slurry; after the slurry is cured, the redispersible latex powder can also improve the tensile strength, increase the bending strength, reduce the elastic modulus, improve the deformability, increase the compactness of the plate, increase the wear-resisting strength, improve the cohesive strength and reduce the water absorption.

Based on the formula of the cement-based concrete plate adopting the low-alkalinity cement, the autoclaved curing conditions are set to be 1.2-1.4MPa and 175-185 ℃, so that the low-alkalinity cement in the formula can be ensured to fully react with the fused quartz with larger specific gravity, and the reaction is ensured to be complete.

Further, in the step (3), the internal pressure of the autoclave is gradually increased to 1.2-1.4MPa within 1.5-2.5 hours, and the temperature is increased to 175-185 ℃. By adopting longer time for raising temperature and boosting pressure, the reaction speed in the concrete slab is uniformly raised, and the reduction of the strength of the slab caused by overlarge local stress due to 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 5-7 hours.

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): and maintaining the formed product for 50-60 days, wherein the cement hydration reaction is basically finished and the formed product has stable breaking 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 adopting the low-alkalinity cement in the embodiment group comprises the following steps:

(2) pouring the slurry into a mould, and demoulding after curing to obtain the concrete slab, wherein the curing conditions are as follows: the temperature is 20 ℃, and the relative humidity is 95%;

(3) putting the concrete plate obtained in the step (2) into an autoclave, gradually increasing the internal air pressure of the autoclave to 1.3MPa within 2 hours, increasing the temperature to 180 ℃, keeping the temperature and the pressure constant for 13 hours, reducing the internal air pressure of the autoclave to be less than or equal to 0.1MPa within 6 hours, 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 is 20 ℃, and the relative humidity is 95 percent, so as to obtain a formed product;

(5): the molded article was further cured for 54 days.

The formulations in parts by weight of the cement-based concrete panels using low alkalinity cements of this example group are shown in the following table.

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. The results are shown in the following table.

Item	Example A1	Example A2	Example A3	Example A4	Example A5
						Early flexural strength MPa	12.66	13.27	13.89	13.68	13.75
Finished product breaking strength MPa	13.91	13.89	14.33	14.2	14.56
						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.

Comparative example group A

The amount of fused silica was 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 using low alkalinity cement of this comparative example group is shown in the following table.

Raw materials	Comparative example A1	Comparative example A2	Comparative example A3
				Low alkalinity cement	160	160	160
70-100 mesh fused quartz	20	70	20
				120-200 mesh fused silica	30	10	80
325 mesh fused quartz	5	10	10
				325 mesh common quartz	200	200	200
Water reducing agent	2	2	2
				Hydroxypropyl methylcellulose	0.4	0.4	0.4
Defoaming agent	0.6	0.6	0.6
				Redispersible latex powder	0.4	0.4	0.4
Water (W)	60	60	60
				Item	Comparative example A1	Comparative example A2	Comparative example A3
Early flexural strength MPa	12.05	11.84	12.15
				Finished product breaking strength MPa	12.99	12.56	13.08
The finished product has no cracks	No obvious crack	No obvious crack	No obvious crack

Item	Comparative example A1	Comparative example A2	Comparative example A3
				Early flexural strength MPa	12.05	11.84	12.15
Finished product breaking strength MPa	12.99	12.56	13.08
				The finished product has no cracks	No obvious crack	No obvious crack	No obvious crack

As can be seen from the above table, when the total amount of the fused silica is reduced, the amount of the fused silica of 70-100 meshes is increased, or the amount of the fused silica of 120-200 meshes is increased while the amount of the fused silica of 70-100 meshes is reduced, the early strength and the finished strength of the concrete slab are reduced. The particle size of the 70-100 mesh fused silica is large, which is difficult to perform sufficient reaction with cement, thus reducing the strength of the plate, and when the usage amount of the 70-100 mesh fused silica is small and the usage amount of the 120-200 mesh fused silica is increased, the effect of material close packing is insufficient, thus reducing the strength of the plate.

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	10.56	10.31	13.92	13.96
Finished product breaking strength MPa	11.23	11.28	14.34	14.37
					The finished product has no cracks	With obvious cracks	With obvious cracks	No obvious crack	No obvious crack

After the temperature and pressure rising time or the temperature and pressure reducing time is shortened, the concrete slab has obvious cracks, and after the temperature and pressure rising time or the temperature and pressure reducing time is increased, the strength of the concrete slab is not changed greatly, so that the better plate strength can be ensured and the production efficiency can be higher by adopting the temperature and pressure rising time of 1.5 to 2.5 hours and the temperature and pressure reducing time of 5 to 7 hours.

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, 50 parts of 70-100 mesh fused quartz, 40 parts of 100-200 mesh fused quartz, 25 parts of 325 mesh fused quartz, 150 parts of 325 mesh ordinary quartz, 4 parts of polycarboxylic acid water reducing agent, 0.2 part of hydroxypropyl methyl cellulose, 0.4 part of defoaming agent, 0.5 part of redispersible latex powder and 50 parts of water.

The early strength of the prepared concrete slab is 13.64MPa, the finished product strength is 14.02MPa, and the finished product plate has obvious cracks.

Comparative example D

The formula of the concrete plate of the comparative example only adopts common quartz, the preparation method of the example group A is adopted, and the formula of the concrete plate of the comparative example comprises the following raw materials in parts by weight: 200 parts of low-alkalinity portland cement, 50 parts of 70-100-mesh common quartz, 40 parts of 100-sand 200-mesh common quartz, 175 parts of 325-mesh common quartz, 4 parts of polycarboxylic acid water reducing agent, 0.2 part of hydroxypropyl methyl cellulose, 0.4 part of defoaming agent, 0.5 part of redispersible latex powder and 50 parts of water.

The early strength of the prepared concrete slab is 10.32MPa, the finished product strength is 11.36MPa, and the finished product plate has obvious cracks.

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 adopting the low-alkalinity cement is characterized by comprising the following raw materials in parts by weight: 100-200 parts of low-alkalinity cement, 80-140 parts of fused silica, 50-200 parts of common silica and 20-60 parts of water.

2. The cement-based concrete slab using low alkalinity cement as claimed in claim 1, wherein 80-140 parts of said fused silica comprises 30-55 parts of 70-100 mesh fused silica, 40-60 parts of 120-200 mesh fused silica and 10-25 parts of 325 mesh fused silica.

3. The cement-based concrete board using low alkalinity cement as claimed in claim 1, wherein said ordinary quartz has a particle size of 325 mesh.

4. The cement-based concrete slab adopting low-alkalinity cement as claimed in claim 1, wherein the raw materials in parts by weight further include 1-4 parts of water reducing agent, 0.1-0.4 part of hydroxypropyl methylcellulose, 0.1-0.6 part of defoaming agent and 0.1-0.5 part of redispersible latex powder.

5. The method of making a cement-based concrete panel using low alkalinity cement as claimed in any one of claims 1 to 4, comprising 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 1.2 to 1.4MPa for 1.5 to 2.5 hours, and the temperature is increased to 175-185 ℃.

8. The production method according to claim 5, wherein in the step (3), the internal pressure of the autoclave is reduced to 0.1MPa or less and the temperature is reduced to room temperature over a period of 5 to 7 hours.

9. The production method according to claim 5, further comprising step (5) after the step (4): and continuously maintaining the molded product for 50-60 days.