1. A method of improving the durability of a concrete article using a carbonized coating, comprising the steps of:

uniformly mixing 80-100 parts of carbonized active cementing material, 0-20 parts of auxiliary calcium source, 0.1-2.0 parts of carbonized layer reinforcing agent, 1-6 parts of water reducing agent and 25-45 parts of water to obtain carbonized coating;

and coating the carbonized coating on the surface of a product substrate, and standing and carbonizing to obtain the concrete product coated with the carbonized coating.

2. The method for improving the durability of a concrete product by utilizing the carbonized coating according to claim 1, wherein the raw materials of the carbonized coating comprise, by mass percent: 80-100 parts of carbonized active cementing material, 10-20 parts of auxiliary calcium source, 0.1-2.0 parts of carbonized layer reinforcing agent, 1-6 parts of water reducing agent and 25-45 parts of water.

3. The method for improving the durability of concrete products by using the carbonized coating according to claim 1 or 2, wherein the carbonized active cementing material is one or more of steel slag powder, gamma-type dicalcium silicate, monocalcium silicate and tricalcium disilicate.

4. The method for improving the durability of a concrete product using a carbonized coating according to claim 1 or 2, wherein the auxiliary calcium source is calcium hydroxide.

5. The method for improving the durability of a concrete product by using the carbonized coating according to claim 1 or 2, wherein the carbonized layer reinforcing agent is one or more of polyethylene glycol, polyvinyl alcohol, chitin and carboxymethyl cellulose.

6. The method for improving the durability of the concrete product by utilizing the carbonized coating according to claim 1 or 2, characterized in that the water reducing agent is a polycarboxylic acid type high efficiency water reducing agent.

7. The method for improving the durability of a concrete product by using a carbonized coating according to claim 1 or 2, characterized in that the product matrix is at least one of a hardened concrete product or a cement paste, a mortar product.

8. The method for improving the durability of a concrete product using a carbonized coating according to claim 7, wherein said hardened concrete product is a room temperature cured product, a steam cured product or an autoclave cured product.

9. The method for improving the durability of a concrete product by using a carbonized coating according to claim 1, wherein the temperature of the standing process is 5-50 ℃, the relative humidity is 10% -50%, and the time is 5-120 min.

10. The method for improving the durability of a concrete product by using a carbonized coating according to claim 1, wherein the temperature of the carbonization environment is 5-50 ℃, the relative humidity is 50% -100%, the carbon dioxide concentration is 80% -99%, and CO is added during the carbonization process₂The gas partial pressure is 0.1-0.5MPa, and the carbonization time is 4-24 h.

Background

The concrete product has good quality controllability and short production period, and is widely applied to the construction of basic facilities such as fabricated buildings, bridges, tunnels and the like. However, the concrete product is easy to corrode and further destroy and lose efficacy when being in service in areas with high contents of sulfate, chloride and the like such as saline-alkali soil, coastal areas and the like, and the service time of the concrete product is greatly shortened, so that the concrete product has important significance in improving the durability.

Generally, effective methods for improving the erosion resistance of concrete products can be divided into two categories: (1) the erosion resistance of the concrete material is improved; (2) and carrying out surface coating treatment on the concrete product. The surface coating can economically, conveniently and effectively improve the durability of the concrete product and has wide application in engineering.

The surface coating material of concrete products is various, such as silane/siloxane, epoxy resin, polyurethane, asphalt, magnesium phosphate cement and the like. Researches show that the calcium carbonate has high stability to chloride ions and sulfate ions, can obviously improve the sulfate corrosion resistance and the chloride ion corrosion resistance of concrete products when being uniformly distributed on the surface of the concrete products to form a layer film structure, and has good application prospect when being used as a coating material of the concrete products.

However, the research on improving the durability of concrete products by using a carbonized coating mainly containing calcium carbonate is only reported recently. Meanwhile, the utilization rate of the product curing device is improved, and the improvement of the production efficiency is an important part in the production process of concrete products, so that the production efficiency must be considered when the product coating is researched and developed.

Disclosure of Invention

In view of the above, it is necessary to provide a method for improving the durability of a concrete product by using a carbonized coating, so as to solve the technical problems of low efficiency and low utilization rate of curing devices in the prior art.

The invention provides a method for improving the durability of a concrete product by utilizing a carbonized coating, which comprises the following steps:

s1, uniformly mixing 80-100 parts of carbonized active cementing material, 0-20 parts of auxiliary calcium source, 0.1-2.0 parts of carbonized layer reinforcing agent, 1-6 parts of water reducing agent and 25-45 parts of water to obtain carbonized coating;

and S2, coating the carbonized coating on the surface of the product substrate, and standing and carbonizing to obtain the concrete product coated with the carbonized coating.

Compared with the prior art, the invention has the beneficial effects that:

by introducing the auxiliary calcium source, the invention can shorten the carbonization time, is beneficial to improving the utilization rate and the production efficiency of the carbonization device and meets the requirements of the production process of products; the invention applies the carbonized coating prepared by the carbonized active cementing materials such as steel slag and the like to the surface of the concrete product, realizes the aim of economically, conveniently and effectively improving the durability of the concrete product by the calcium carbonate coating, widens the application range of the carbonized active cementing materials, can greatly store carbon dioxide and has obvious environmental benefit.

Drawings

FIG. 1 is a process flow diagram of one embodiment of a method of the present invention for improving the durability of a concrete article using a carbonized coating;

FIG. 2 is a graph of a steam curing schedule for a steam concrete product used in the present invention;

FIG. 3 is a graph showing the autoclave curing system of the autoclaved concrete article used in the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Referring to fig. 1, the present invention provides a method for improving durability of a concrete product using a carbonized coating, comprising the steps of:

s1, uniformly mixing 80-100 parts of carbonized active cementing material, 0-20 parts of auxiliary calcium source, 0.1-2.0 parts of carbonized layer reinforcing agent, 1-6 parts of water reducing agent and 25-45 parts of water to obtain carbonized coating;

and S2, coating the carbonized coating on the surface of the product substrate, and standing and carbonizing to obtain the concrete product coated with the carbonized coating.

According to the invention, after water accounting for 25-45% of the total amount of the carbonization active cementing material and the auxiliary calcium source is added, the prepared coating has good fluidity, the coating process is more favorably realized, the formed coating has good compactness, and the water content can be reduced and the carbonization effect can be improved through the standing process. The low water content of the coating causes poor coating fluidity, finally causes poor coating compactness, and reduces the durability improving capability of the coating; too high a water content of the coating will not facilitate carbonization and will also reduce the ability of the coating to improve durability.

In this embodiment, the carbonized active cementing material is one or more of steel slag powder, gamma-dicalcium silicate, monocalcium silicate and tricalcium disilicate; the auxiliary calcium source is calcium hydroxide; the carbonized layer intensifier is one or more of polyethylene glycol, polyvinyl alcohol, chitin and carboxymethyl cellulose; the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent. The method utilizes calcium hydroxide as an auxiliary calcium source, can shorten the carbonization time, is favorable for improving the utilization rate and the production efficiency of the carbonization device, and meets the requirements of the production process of products. On one hand, the excessive calcium hydroxide can cause the system to generate high heat in the carbonization process, so that the water of the coating is evaporated, and the subsequent carbonization is not facilitated to be continued, thereby reducing the carbonization degree and being not beneficial to improving the compactness; on the other hand, high content of calcium hydroxide tends to result in incomplete carbonization, while non-carbonized calcium hydroxide is disadvantageous in improving durability.

In this embodiment, the raw materials of the carbonized coating, calculated by mass percent, include: 80-100 parts of carbonized active cementing material, 10-20 parts of auxiliary calcium source, 0.1-2.0 parts of carbonized layer reinforcing agent, 1-6 parts of water reducing agent and 25-45 parts of water.

In the present embodiment, the product substrate is at least one of a hardened concrete product, cement paste, and mortar product. Further, the hardened concrete product is a room temperature cured product, a steam cured product, or an autoclave cured product, preferably a steam cured product or an autoclave cured product, more preferably an autoclave cured product. The method of the invention is particularly suitable for improving the durability of steam cured concrete products.

In this embodiment, the coating mode is not limited by the present invention, and those skilled in the art can make routine selections as needed. For example, the coating is at least one of spraying, knife coating, or brush coating; the coating thickness is 0.2-2.0 mm.

In the embodiment, the temperature in the standing process is 5-50 ℃, the relative humidity is 10% -50%, and the time is 5-120 min.

In the embodiment, in the carbonization process, the temperature of the carbonization environment is 5-50 ℃, the relative humidity is 50-100%, the concentration of carbon dioxide is 80-99%, and CO is₂The gas partial pressure is 0.1-0.5MPa, and the carbonization time is 4-24 h. Further, the carbonization time is 4-10 h.

For avoiding redundancy, the concrete products in the following embodiments of the present invention include normal temperature cured products, steam cured products and autoclave cured products; respectively obtained by the following steps:

curing the product at normal temperature: the proportion of the components of the concrete products with different strength grades is shown in table 1. Mixing the weighed components according to the proportion, stirring uniformly, and respectively pouring the mixture into a container with the thickness of 100mm multiplied by 100mm and a container with the thickness of 100mm multiplied by 100mmThe mould is molded in a vibration mode; then sealing and curing for 24 hours, demoulding, transferring to a curing chamber with the temperature of 20 +/-0.5 ℃ and the humidity of 95 +/-0.5 percent, and curing for 7 days; and finally, polishing and removing the floating slurry with the thickness of 0.1-0.2mm on the surface of the test block, and then wiping the test block with a wet rag for later use. Wherein, the concrete test block of 100mm multiplied by 100mm is used for the performance test of sulfate erosion resistance,the test block is used for testing the corrosion resistance of the chloride ions.

TABLE 1C 30, C50 and C80 concrete weight ratio

Numbering	Cement	Water (W)	Sand	Crushing stone	Water reducing agent
						C30	380	159.6	744	1116	1.9
C50	480	153.6	726	1089	3.9
						C80	550	137.5	724	1087	8.3

Wherein, the cement is the commercially available P.I 52.5 cement; the water is tap water; the sand is commercial river sand, and fineness modulus of the sand adopted by C30, C50 and C80 is 2.3, 2.6 and 2.5 respectively; the crushed stone is commercially available continuous graded crushed stone, and the crushed stones adopted by C30, C50 and C80 are respectively continuous graded limestone crushed stone with the grain sizes of 5-31.5mm, 5-20mm and 5-20 mm; the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent with the solid content of 20%, and the water content in the water reducing agent is not counted in the weight part of water.

Steam curing the product: the proportion of each component of the Z30, Z50 and Z80 grade concrete products cured by steam is respectively the same as the proportion of C30, C50 and C80 grade concrete products cured at normal temperature, and the curing system is shown in figure 2.

Pressing and steaming to maintain the product: the proportions of the components of autoclaved grade-Y30, autoclaved grade-Y50 and autoclaved grade-Y80 concrete products are respectively the same as the proportions of normal-temperature cured grade-C30, grade-C50 and grade-C80 concrete products, and the curing system is shown in figure 3.

Example 1

(1) Mixing 90 parts of converter steel slag powder, 10 parts of calcium hydroxide, 0.1 part of polyvinyl alcohol (PVA), 0.2 part of sodium carboxymethylcellulose (CMC), 4 parts of water reducing agent and 34 parts of tap water, and uniformly mixing to obtain a carbonized coating; wherein the calcium hydroxide is chemical pure grade calcium hydroxide, the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent with the solid content of 40%, and the water content in the water reducing agent is not counted in the weight part of water;

(2) uniformly spraying the carbonized coating on a concrete test block by a paint spraying gun, controlling the spraying thickness to be 0.8-1.2mm, standing the sprayed test block for 30 minutes in an environment with the temperature of 20 +/-0.5 ℃ and the relative humidity of 45 +/-0.5%, and then putting the test block in a carbonization bucket for carbonization to obtain the concrete test block coated with the carbonized coating. Wherein the environmental temperature of the carbonization barrel is 20 +/-0.5 ℃, the carbonization humidity is controlled to be about 75 percent by potassium sulfate saturated solution, the concentration and the pressure of carbon dioxide are respectively 99 percent and 0.3MPa, and the carbonization time is 10 hours.

Example 2

(1) Mixing 100 parts of converter steel slag powder, 0.1 part of polyvinyl alcohol (PVA), 0.2 part of sodium carboxymethylcellulose (CMC), 6 parts of a water reducing agent and 28 parts of tap water, and uniformly mixing to obtain a carbonized coating; wherein the calcium hydroxide is chemical pure grade calcium hydroxide, the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent with the solid content of 40%, and the water content in the water reducing agent is not counted in the weight part of water;

(2) and (3) coating the carbonized coating on a concrete test block by scraping, wherein the scraping thickness is controlled to be 0.8-1.2mm, then standing the scraped test block for 30 minutes in an environment with the temperature of 20 +/-0.5 ℃ and the relative humidity of 45 +/-0.5%, and then putting the test block into a carbonization barrel for carbonization to obtain the concrete test block coated with the carbonized coating. Wherein the environmental temperature of the carbonization barrel is 20 +/-0.5 ℃, the carbonization humidity is controlled to be about 75 percent by potassium sulfate saturated solution, the concentration and the pressure of carbon dioxide are respectively 99 percent and 0.3MPa, and the carbonization time is 18 hours.

Example 3

(1) Mixing 80 parts of converter steel slag powder, 20 parts of calcium hydroxide, 0.7 part of polyvinyl alcohol (PVA), 1.3 parts of sodium carboxymethylcellulose (CMC), 1 part of water reducing agent and 45 parts of tap water, and uniformly mixing to obtain a carbonized coating; wherein the calcium hydroxide is chemical pure grade calcium hydroxide, the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent with the solid content of 40%, and the water content in the water reducing agent is not counted in the weight part of water;

(2) brushing the carbonized coating on a concrete test block, controlling the brushing thickness to be 0.8-1.2mm, standing the brushed test block for 120 minutes in an environment with the temperature of 20 +/-0.5 ℃ and the relative humidity of 45 +/-0.5%, and then putting the test block in a carbonization barrel for carbonization to obtain the concrete test block coated with the carbonized coating. Wherein the environmental temperature of the carbonization barrel is 20 +/-0.5 ℃, the carbonization humidity is controlled to be about 75 percent by potassium sulfate saturated solution, the concentration and the pressure of carbon dioxide are respectively 99 percent and 0.3MPa, and the carbonization time is 4 hours.

Comparative example 1

(1) Mixing 100 parts of converter steel slag powder, 0 part of calcium hydroxide, 0.1 part of polyvinyl alcohol (PVA), 0.2 part of sodium carboxymethylcellulose (CMC), 4 parts of water reducing agent and 34 parts of tap water, and uniformly mixing to obtain a carbonized coating; wherein the calcium hydroxide is chemical pure grade calcium hydroxide, the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent with the solid content of 40%, and the water content in the water reducing agent is not counted in the weight part of water;

(2) uniformly spraying the carbonized coating on a concrete test block by a paint spraying gun, controlling the spraying thickness to be 0.8-1.2mm, standing the sprayed test block for 30 minutes in an environment with the temperature of 20 +/-0.5 ℃ and the relative humidity of 45 +/-0.5%, and then putting the test block in a carbonization bucket for carbonization to obtain the concrete test block coated with the carbonized coating. Wherein the environmental temperature of the carbonization barrel is 20 +/-0.5 ℃, the carbonization humidity is controlled to be about 75 percent by potassium sulfate saturated solution, the concentration and the pressure of carbon dioxide are respectively 99 percent and 0.3MPa, and the carbonization time is 16 h.

Comparative example 2

(1) Mixing 60 parts of converter steel slag powder, 40 parts of calcium hydroxide, 0.1 part of polyvinyl alcohol (PVA), 0.2 part of sodium carboxymethyl cellulose (CMC), 4 parts of water reducing agent and 34 parts of tap water, and uniformly mixing to obtain a carbonized coating; wherein the calcium hydroxide is chemical pure grade calcium hydroxide, the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent with the solid content of 40%, and the water content in the water reducing agent is not counted in the weight part of water;

(2) uniformly spraying the carbonized coating on a concrete test block by a paint spraying gun, controlling the spraying thickness to be 0.8-1.2mm, standing the sprayed test block for 30 minutes in an environment with the temperature of 20 +/-0.5 ℃ and the relative humidity of 45 +/-0.5%, and then putting the test block in a carbonization bucket for carbonization to obtain the concrete test block coated with the carbonized coating. Wherein the environmental temperature of the carbonization barrel is 20 +/-0.5 ℃, the carbonization humidity is controlled to be about 75 percent by potassium sulfate saturated solution, the concentration and the pressure of carbon dioxide are respectively 99 percent and 0.3MPa, and the carbonization time is 10 hours.

Test group 1

The concrete products coated with the carbonized coatings in the above examples 1 to 3 and the concrete products not coated with the carbonized coatings were evaluated for compressive strength, sulfate erosion resistance and chloride ion erosion resistance, and the test results are shown in tables 2 to 5.

Wherein, in order to test the influence of the carbonized coating on the strength of the concrete product, the part of the test block with the thickness of 100mm multiplied by 100mm is continuously maintained in a curing room with the temperature of 20 +/-0.5 ℃ and the humidity of 95 +/-0.5 percent to the age of 28 days; and 7-day test blocks are adopted for evaluating the chloride ion corrosion resistance and the sulfate corrosion resistance.

Wherein, the rapid chloride ion migration coefficient method (RCM method) of evaluating the corrosion resistance of the chloride ions is executed in the standard of the test method of the long-term performance and the durability performance of the common concrete (GB/T50082-2009).

The sulfate erosion-dry-wet cycle test is adopted for evaluating the sulfate erosion resistance, and the specific test method comprises the following steps:

s1, placing the test block in a container, and completely soaking the test block in a 5% sodium sulfate solution for 12 hours;

s2, discharging the sulfate solution by a pump until the test block is completely exposed to the air;

s3, after S2 is finished, the fan is started to blow the sulfate solution on the surface of the test block, the running time of the fan is 2 hours, and after the fan stops running, the test block is kept stand for 10 hours; then pumping 5% sodium sulfate solution into the container by a pump to S1 state;

the steps S1-S3 are a cycle of 24 hours, and the sodium sulfate solution is replaced every 14 days until the test block is obviously cracked.

TABLE 2 compressive Strength (MPa) of samples of different concrete products with/without a carbonation coating (example 1)

Test specimen	Age of 7 days	Age of 28 days
			C30	23.7	39.2
C30 with a coating	25.0	40.5
			C50	42.6	59.4
C50 with a coating	42.4	60.6
			C80	65.3	93.3
C80 with a coating	66.0	94.2
			Z30	29.1	37.3
Z30 with a coating	29.5	39.7
			Z50	48.9	58.7
Z50 with a coating	49.3	58.6
			Z80	70.1	89.8
Z80 with a coating	71.6	90.4
			Y30	38.7	37.2
Y30 with a coating	38.2	38.3
			Y50	56.3	57.7
Y50 with a coating	58.7	59.1
			Y80	85.4	87.5
Y80 with a coating	86.1	88.4

As can be seen from the results in Table 2, the carbonized coating has no adverse effect on the strength of the concrete products of different curing systems in 7 days and 28 days, and has small contribution to the strength of the concrete products. It follows that the treatment of the surface of the concrete article by means of the carbonised coating does not adversely affect the use of the concrete article component, and therefore the technical process is feasible in the manufacture and application of concrete articles.

TABLE 3 durability test of concrete products of Normal temperature group in each example

Table 4 durability test of concrete products in steam-cured groups in examples

TABLE 5 concrete product durability test of autoclave set in each example

As can be seen from the results in tables 3-5, the carbonized coating layer can significantly improve the durability of concrete products of different curing systems. In the aspect of sulfate erosion resistance, the carbonized coating can improve the sulfate erosion resistance of the concrete product, and particularly can obviously improve the sulfate erosion resistance of the low-strength concrete; the concrete article coated with the carbonized coating has a chloride diffusion coefficient significantly lower than that of the uncoated treated concrete article in terms of resistance to chloride ion attack.

The three coating modes of spraying, blade coating and brush coating can achieve the purpose of improving the sulfate erosion resistance and the chloride ion erosion resistance of the concrete product.

Furthermore, from the results shown in tables 2 to 5, it is clear that steam curing, particularly autoclaving, can significantly improve the early compressive strength of the concrete product, but has a large negative effect on the sulfate attack resistance and chloride ion attack resistance of the concrete product. After the concrete subjected to steam curing and autoclaving curing is subjected to surface carbonization coating treatment, the sulfate corrosion resistance and the chloride ion corrosion resistance of the concrete are both remarkably improved, and the chloride ion diffusion coefficient of the concrete is lower than that of the concrete subjected to normal-temperature curing and surface coating-free treatment in the same grade, so that the surface carbonization coating can overcome the adverse effects of low sulfate corrosion resistance and low chloride ion corrosion resistance on concrete products caused by steam curing, particularly autoclaving curing.

Test group 2

The concrete products of the autoclave group of the concrete products coated with the carbonized coatings in the comparative examples 1-2 were evaluated for compressive strength, sulfate erosion resistance and chloride ion erosion resistance by the method of test group 1, and the test results are shown in table 6.

TABLE 6

As can be seen from the data in Table 6, the addition of calcium hydroxide can shorten the carbonization time and improve the production efficiency without affecting the product performance; if the amount of calcium hydroxide added is too large, the durability will be significantly reduced.

Compared with the prior art, the invention has the beneficial effects that:

(1) the coating coated on the surface of the cement-based product forms a compact and hard protective layer on the surface of the product after carbonization treatment, can well isolate harmful ions in an erosion environment, can effectively prevent the concrete product from being eroded, and improves the durability of the concrete product.

(2) The steel slag powder, the gamma-type dicalcium silicate, the monocalcium silicate and the tricalcium disilicate adopted by the invention are nontoxic and harmless, the raw materials are rich, the preparation cost is low, and the economic benefit is good. Meanwhile, the steel slag powder is used as the carbonized coating material, so that the durability of concrete is improved, the resource utilization of solid wastes can be promoted, the application range of the steel slag is widened, and the environment benefit is good.

(3) The steel slag powder, the gamma-type dicalcium silicate, the monocalcium silicate and the tricalcium silicate have excellent carbonization activity and can react with CO₂Reaction to form CaCO₃Can utilize the high concentration CO in the factory₂The flue gas is used as carbonized gas, thereby CO in the flue gas can be removed₂Curing is carried out, and the environment benefit is remarkable.

(4) The coating material can be sprayed, brushed and blade-coated by adjusting the proportion, has good applicability to cement-based products with complex structures and shapes, can be widely applied to concrete prefabricated parts of projects such as railways, bridges, tunnels and the like, and has simple process and easy realization of required construction conditions.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.