KR20060079447A - Sulphuric acid resistant mortar composition for concrete - Google Patents

Abstract

The present invention relates to a sulfuric acid-resistant repair mortar composition for concrete that can extend the long-term life of the existing concrete by repairing the aged portion of the concrete by chemical erosion. The sulfuric acid-resistant repair mortar composition for concrete of the present invention is 100 parts by weight of Portland cement, 50 to 100 parts by weight of blast furnace slag, 10 to 20 parts by weight of expanding material, 0.5 to 5 parts by weight of fiber, 0.1 to 5 parts by weight of polymer resin, and a high performance water reducing agent. 1 to 3 parts by weight, inorganic thickener 0.02 to 0.08 parts by weight and silica sand 150 to 300 parts by weight. The composition of the present invention is suitable as a repair mortar for concrete, which is inferior to chemical erosion, and is economical in terms of overall construction cost because the amount that can be applied once is large in the mortar.

Sulfur Resistant, Mortar

Description

Sulfuric acid-resistant repair mortar composition for concrete {SULPHURIC ACID RESISTANT MORTAR COMPOSITION FOR CONCRETE}

1 is a graph showing the particle size distribution of blast furnace slag fine powder used in the composition of the present invention.

Figure 2 is a graph showing the results of differential thermal analysis (DTA) and thermogravimetric analysis (TG) of the cement hardened material incorporating slag having a high powder degree according to the present invention.

3 is a graph showing the results of experiments with sulfuric acid resistance (weight change rate) for the composition of the present invention according to the Tokyo Metropolitan Sewerage Bureau standard.

Figure 4 is a graph measuring the penetration resistance for the composition of the present invention according to the Tokyo Metropolitan Sewerage Bureau standards.

5A and 5B are fracture surface photographs of specimens taken after the sulfuric acid immersion experiments were performed for Comparative Examples and Examples of the present invention, respectively.

6 is a photograph showing a state in which the composition of the present invention is applied once on a concrete plate.

The present invention relates to a sulfuric acid resistant repair mortar composition for concrete, and more particularly, to a composition for repairing the aged portion of the concrete by chemical erosion to extend the long-term life of the existing concrete.

The aging of concrete structures is due to neutralization, salt damage, east sea, chemical erosion, alkali aggregate reaction, fatigue, weathering, fire, etc., and the concrete does not perform its original function and deteriorates with time. Double chemical corrosion is called chemical corrosion collectively as the aging phenomenon in which concrete is chemically reacted from the outside and the hydration products constituting the cement hardened body are deteriorated or decomposed and lose their binding ability.

In chemical corrosion, there is a small probability that chemical corrosion is a problem in a general environment, and organic matter contained in domestic sewage, etc. reacts by bacteria to produce sulfate ions, which causes concrete to erode concrete, hot spring areas or acid rain, etc. In most cases, concrete is eroded by acid. Therefore, the structures subject to chemical erosion include related structures such as chemical plants and food factories, underground structures of soil contamination and hot springs, sewage-related sewer pipes and covered structures.

Since chemical erosion is easy to be confused with the aging phenomenon caused by the neutralization, east sea, and salt sea, it is not sulphate-repairing mortar, but instead of the existing repair mortar. There are frequent cases of sharp drops.

Therefore, it is urgent to develop a dedicated mortar composition for repairing sewage pipes and covered structures that are highly likely to cause chemical corrosion separately from neutralization, east sea, and salt sea.

In order to solve the above problems of the prior art, the present invention is to provide a sulfuric acid-resistant repair mortar composition for concrete, which is excellent in chemical resistance and durability by supplementing the existing repair mortar properties by appropriately adjusting the components and component ratios resistant to chemical corrosion.

In order to achieve the above technical problem, the sulfuric acid resistant repair mortar composition for concrete of the present invention is 100 parts by weight of Portland cement, 50 to 100 parts by weight of blast furnace slag, 10 to 20 parts by weight of expanding material, 0.5 to 5 parts by weight of fiber, and a polymer resin of 0.1. It includes -5 parts by weight, 1 to 3 parts by weight of a high performance reducing agent, 0.02 to 0.08 parts by weight of inorganic thickener and 150 to 300 parts by weight of silica sand. In the present invention, the expanding agent is preferably 5 to 10 parts by weight of the CSA-based expanding agent and 5 to 10 parts by weight of the gypsum-based expanding agent.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In the powder used in the present invention, that is, the blast furnace slag fine powder, it is preferable that the particle size distribution is kept constant using grinding means such as a mill. For example, the blast furnace slag powder may be ground to an average diameter of about 6 ㎛. The reason for crushing the blast furnace slag powder is as follows.

First, the average particle size of a conventional cement is 16 mu m, and assuming that the cement particles are round particles, the size of particles that can enter the voids is about 6 mu m. The blast furnace slag powder is pulverized to about 6 μm to fill the cement particles, thereby increasing the filling rate, densifying and improving physical properties. The particle size distribution of the blast furnace slag fine powder used in the composition in the present invention is shown in FIG. 1.

Another reason for crushing the blast furnace slag powder is to suppress the amount of Ca (OH) ₂ produced. Hydration reactions and products of calcium silicate compounds C ₂ S and C ₃ S, which occupy the largest amount in Portland cement, are as follows.

2C ₃ S + 6H _→ C ₃ S ₂ H ₃ + 3CH

2C ₂ S + 4H _→ C ₃ S ₂ H ₃ + CH

Hydration products are largely generated from calcium silicate hydrate and calcium hydroxide, usually about 20-30% of calcium hydroxide in the cement hardening body. This calcium hydroxide is very weak to sulfuric acid, and gypsum is formed through the following reaction.

Ca (OH) ₂ + H ₂ SO _{4 →} CaSO ₄ 2H ₂ O

The resulting gypsum acts as a material to produce ethrinite, which causes expansion and destruction, causing cracking and peeling due to chemical corrosion.

Figure 2 shows the results of differential thermal analysis (DTA) and thermogravimetric analysis (TG) of the cement hardened material incorporating slag having a high powder density. As shown in the figure, a large amount of calcium silicate (CSH) hydrate is produced in the slag-incorporated cement, but no weak calcium hydroxide is generated in the acid. When calcium hydroxide is produced, a thermogravimetric reduction (TG) peak due to dehydration occurs around 450 to 500 ° C, but as shown in FIG. Therefore, this composition exhibits the outstanding effect also in sulfuric acid resistance.

In the composition of the present invention, the blast furnace slag fine powder is preferably used in an amount of about 50 to 100 parts by weight based on 100 parts by weight of Portland cement.

As a swelling agent used in the present invention, a CSA-based expander means a calcium sulpho aluminate system and inhibits dry shrinkage due to an external environment by imparting expansion properties without adversely affecting the physical properties of mortar itself. In addition to gypsum-based expanders, it prevents the mortar from cracking and improves the bond strength. The expanding agent is preferably used in about 10 to 20 parts by weight based on 100 parts by weight of Portland cement. In addition, when both the CSA-based and gypsum-based expanding agent is used as the expanding agent, it is preferably included 5 to 10 parts by weight.

The fiber used in the present invention has an average length of 4 mm, which does not interfere with the flowability of the composition, and is homogeneously dispersed in the mortar composition to prevent cracking after curing of the mortar composition and to improve bending strength. In the present invention, the fiber may be a conventional organic fiber such as polyethylene fiber.

The fiber is preferably used in about 0.5 to 5 parts by weight based on 100 parts by weight of Portland cement.

The polymer resin used in the present invention is an acid-resistant acrylic powder resin, which is a redispersable polymer powder for the pre-mixed type mortar composition, which can be mixed and used in the powder state when the powder is mixed. have. The weight average molecular weight of the acrylic powder resin is not particularly limited, but is generally 10 ⁵ to 10 ⁶ . When properly mixed with the cement component, the resin film is formed between the cement hydrates, thereby filling the capillary pores of the cement, thereby increasing the compactness and adhesion strength. In the present invention, the polymer resin is preferably included 0.1 to 5 parts by weight based on 100 parts by weight of the Portland cement.

The high performance sensitizer is preferably melamine or naphthalene, but polycarboxylic acid may be used. The high performance water reducing agent is preferably included in about 1 to 3 parts by weight based on 100 parts by weight of Portland cement.

Inorganic thickeners used in the present invention, in addition to improving viscosity, improve adhesion and cohesion, thereby inhibiting material separation, and when applying or spraying on an aged concrete structure wall or ceiling, which is a characteristic of the repair mortar, the coating thickness is maximized without loss of material. This has the advantage of being very economical to repair.

It is preferable that the inorganic thickener has a needle-like structure like fibers and has a static electricity on its surface. The acicular inorganic thickener is about 1.5 to 2.0 μm in length and about 30 mm 3 in diameter. When the inorganic thickener is mixed with cement components and water and applied to an aged concrete structure wall or ceiling, the inorganic thickener is oriented irregularly in the needle-like thickener if no stress is applied, and thus the material is not separated and homogeneous. However, when the force is applied, that is, when the mortar composition is applied to the aged concrete wall, it can be oriented in one direction and the fluidity can be improved, so that the maximum thickness can be applied at once without material loss, which is very economical. On the other hand, conventional organic thickeners can prevent material separation due to the improved viscosity, but due to the presence of improved viscosity, the fluidity is poor when applied or applied. This has the disadvantage of being difficult. The inorganic thickener is preferably included in about 0.02 ~ 0.08 parts by weight based on 100 parts by weight of Portland cement.

In addition, the composition of the present invention includes the silica sand as the aggregate, the aggregate is preferably contained 150 to 300 parts by weight of Portland cement.

The dry mortar composition of the present invention described above is constructed by mixing about 15 to 20 parts by weight of the blended water with respect to 100 parts by weight of Portland cement.

Hereinafter, the present invention will be described in more detail with reference to preferred examples and comparative examples, but the present invention is not limited thereto.

Example

Mortar example compositions of the present invention are shown in Table 1 below. The water powder ratio was fixed at 16%. Table 2 shows the results of physical properties of compressive strength, flexural strength, bond strength, and length change rate. Bond strength and flexural strength were measured by the Japanese dry method, compressive strength was measured by KS F 5105 and length change rate by KS F 2424. The setting time was measured by the Gilmore test method.

Sulfuric acid-resistant repair mortar characteristics are based on the Tokyo Metropolitan Sewerage Bureau standard, which requires the characteristics shown in Table 3.

division cement Blast furnace slag powder Inflating material Thickener High performance water reducer Polymer resin fiber sand #4 # 5 # 6 Example 1 24 22 2.4 0.012 0.36 0.72 0.52 10 20 20 Example 2 25 20.75 2.5 0.0125 0.375 0.75 0.61 Example 3 26 19.7 2.6 0.013 0.39 0.78 0.52 Example 4 27 18.52 2.7 0.0135 0.405 0.81 0.54 Comparative Example 1 45 - - - One 4

Physical properties Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Compressive strength (MPa) 3 days 41.9 42.3 40.6 43.6 45.5 7 days 52.5 51.5 50.9 56.3 56.3 28 days 64.5 65.8 63.2 65.7 68.5 Flexural strength (MPa) 3 days 7.2 7.1 6.8 6.9 1.7 7 days 8.6 8.5 8.6 8.5 2.5 28 days 12.5 11.5 13.5 12.6 3.5 Adhesion Strength (MPa) 14 days 5.8 5.9 5.5 5.4 1.0 28 days 6.8 6.9 6.5 7.0 1.2 Length change rate (× 10 ^-4 ) -3.6 -3.8 -3.4 -3.6 -8.0 Setting time First minute 120 120 130 125 115 Termination (minutes) 270 280 280 290 280

Required performance item Performance indicator Test Methods Strength Characteristics (Compressive Strength: MPa) Age 3 days 25 or more JIS R 5201 (20 ℃) 28 days 45 or more Strength Characteristics (Bending Strength: MPa) Age 3 days 3 or more 28 days 7 or more Penetration diffusion resistance 3 or less 5% sulfuric acid solution changed every week Shrinkage -0.001 or less JIS R 5201 (20 ℃) Adhesion strength 1.5 or more Dry type (20 degrees Celsius) Sulfuric acid resistance (after immersion for 30 days) (weight change rate) Less than ± 10 5% sulfuric acid solution changed every week Constructability (soil, spray) 1 coating thickness up to 2 cm

As can be seen from the above tables, the measured physical properties satisfy all the standards of the Tokyo Metropolitan Sewerage Bureau, and in the case of adhesion strength, they are also satisfied by the KS F 4175 (thin finish wall coating) test method. Appeared. In addition, the physical property value represents a physical property value irrelevant to use as a general repair mortar.

Figure 3 shows the results of the sulfuric acid resistance (weight change rate) test in accordance with the Tokyo Metropolitan Sewerage Bureau standards, Figure 4 is a graph showing the penetration resistance by the Tokyo Metropolitan Sewerage Bureau standards. 5A and 5B are photographs showing fracture planes of specimens after sulfuric acid immersion experiments of Comparative Examples and Examples, respectively. The sulfuric acid resistance was prepared by curing the specimen in water for 30 days, and then immersed in 5% sulfuric acid solution to remove the specimen every week, and the weight loss rate and penetration resistance were observed. The 5% sulfuric acid solution was changed every week.

The dotted lines in the photographs of FIGS. 5A and 5B represent the size of the prototype (5 × 5 × 5 cm). First, referring to Figure 5a, it can be seen that the general mortar by the composition of the comparative example fell off without maintaining the form of the specimen by the sulfuric acid erosion. However, in the case of the embodiment of Figure 5b it can be seen that the original form of the mortar as it is. The white part in the picture shows the product of the outer surface reacting with sulphate, which is represented by the penetration depth of sulfuric acid.

Through the sulfuric acid immersion test results, it can be seen that the mortar composition of the present invention is applied to various concrete structures exposed to sulfuric acid in addition to the repair mortar and exhibits excellent durability.

On the other hand, the composition of the present example was able to apply more than 2cm of the Tokyo Metropolitan Sewerage Bureau standard at the time of one application, but in the case of the comparative example it required three to four application operations to obtain a coating thickness of 2cm. 6 is a photograph showing a state in which the composition of the present invention is applied once on a concrete plate.

The composition of the present invention is very effective for the use of durable concrete structures by restoring the original function of the aged concrete structure in the following points.

1) The mortar composition presented in the present invention shows excellent fluidity without increasing the viscosity, and the coating amount is thicker than that of other mortars so that the overall construction cost is reduced, and thus it is a very economical repair mortar.

2) Particularly, chemically eroded structures are very suitable for repairing concrete eroded concrete due to its outstanding effects such as related structures such as chemical and food factories, underground structures in soil and hot spring areas, sewer pipes and covered structures in sewerage. It can be said.

3) It also contributes to the environment by recycling industrial byproducts.

Claims (2)

100 parts by weight of Portland cement; 50-100 parts by weight of blast furnace slag fine powder; 10 to 20 parts by weight of expandable material; 0.5 to 5 parts by weight of fibers; 0.1 to 5 parts by weight of the polymer resin; High performance water reducing agent 1-3 parts by weight; 0.02 to 0.08 parts by weight of inorganic thickener; And Sulfate-resistant repair mortar composition for concrete, characterized in that it comprises 150 to 300 parts by weight of silica sand. The method of claim 1, The inorganic thickener comprises magnesium aluminosilicate mineral and blast furnace slag fine powder, characterized in that the sulfuric acid-resistant repair mortar composition for concrete.

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