JPH08109081A - Surface deterioration-preventing agent for cement cured material - Google Patents

Abstract

PURPOSE: To obtain a surface deterioration-preventing agent for a cement cured material capable of forming a modified surface layer having excellent abrasion resistance, weather resistance, water resistance and acid resistance by compounding a specific sodium silicate aqueous solution with a phosphatic compound having metal ion-blocking activity. CONSTITUTION: This surface deterioration-preventing agent for a cement cured material is obtained by compounding 100 pts.wt. of a sodium silicate aqueous solution having a molar ratio of SiO2 /Na2 O of 1-4 and a SiO2 content of 5-50wt.% with 0.02-15 pts.wt. of a phosphatic compound having metal ion- blocking activity. The surface deterioration-preventing agent is preferably compounded further with 0.002-15 pts.wt. of a silicon fluoride since the hardness is increased without deteriorating the water resistance, acid resistance, etc., by the silicon fluoride addition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface deterioration preventive agent for hardened cementitious materials.

[0002]

Cement-based hardened materials such as concrete, mortar and cement are widely used in the fields of construction and civil engineering. When these cement-based hardened materials are used indoors, especially when used as flooring materials, they cause dust generation due to surface abrasion.

Further, in outdoor use, carbon dioxide and acid rain in the air intrude through a myriad of fine pores of the cured product,
Such a cement-based cured product has a drawback that it is neutralized and the surface deteriorates significantly over time.

As a method of compensating for such drawbacks, conventionally, a method of applying an organic resin such as an epoxy resin or a polyurethane resin having excellent weather resistance and abrasion resistance to the surface of a hardened cement material has been used.

However, these organic resins are expensive and the construction is complicated. On the other hand, as an inexpensive inorganic material, Japanese Unexamined Patent Publication (Kokai) No. 60-36385 describes a cement-based surface modifier obtained by mixing an alkaline silicate aqueous solution with an aliphatic monohydric lower alcohol.

[0006]

However, in the method described in JP-A-60-36385, the aliphatic 1
Since the water resistance of the modified surface layer formed on the surface of the hardened cementitious material after the evaporation of the hydric lower alcohol is insufficient, the modified surface layer is leached out by rainwater, etc. However, even when used indoors, there is a problem that it is not suitable for use in environments such as floors that come into contact with water. Also,
It has almost no acid resistance, and it has a drawback that it cannot be used when acid resistance is required, such as in floors of food factories.

Therefore, the object of the present invention is to form a modified surface layer having excellent wear resistance, weather resistance, water resistance and acid resistance capable of solving such problems, and a hardened cementitious material. It is to provide a surface deterioration preventing agent.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have blended a specific sodium silicate aqueous solution with a predetermined amount of a phosphoric acid compound having a sequestering effect. When a cement-based cured product was coated with and impregnated with a deterioration inhibitor, it was found that the hardness, water resistance and acid resistance of the modified surface layer formed on the surface of the cured product were dramatically improved, and the present invention was completed. Came to do.

That is, the surface deterioration inhibitor of the cement-based cured product of the present invention is a sodium silicate having a SiO ₂ / Na ₂ O molar ratio of 1 to 4 and a SiO ₂ content of 5 to 50% by weight. It is characterized in that 100 parts by weight of an aqueous solution and 0.02 to 15 parts by weight of a phosphoric acid compound having a sequestering effect are blended.

Further, when the present inventors have added a predetermined amount of silicofluoride to the surface deterioration inhibitor of the cement-based cured product, the hardness can be further increased without impairing the performance such as water resistance and acid resistance. I found that I could do it. Therefore,
The cement-based cured product of the present invention has a surface deterioration preventing agent of 0.0
It is preferred that 02 to 15 parts by weight of silicofluoride is blended.

As described above, the aqueous solution of sodium silicate used in the present invention has a SiO ₂ / Na ₂ O molar ratio in the range of 1 to 4. If an aqueous solution of sodium silicate having a molar ratio of less than 1 is used, the effect of surface-modifying the hardened cementitious material is very small, which does not lead to prevention of deterioration. On the other hand, the molar ratio is 4
The larger aqueous sodium silicate solution contains colloidal silica, and the deterioration inhibitor using the sodium silicate has an increased viscosity and a low permeability.

The sodium silicate aqueous solution used in the present invention is
The SiO ₂ content is 5 to 50% by weight, and preferably 8 to 20% by weight in terms of practical efficiency. If the SiO ₂ content is less than the above, the surface-modifying effect of the cement-based cured product is very small, which does not lead to prevention of deterioration. On the other hand, when the SiO ₂ content exceeds the above range, the viscosity of the deterioration preventing agent using the sodium silicate increases and the permeability decreases.

The aqueous solution of sodium silicate having a SiO ₂ / Na ₂ O molar ratio of 1 to 4 and a SiO ₂ content of 5 to 50% by weight used in the present invention can be obtained by a conventionally known method. It can be easily obtained by a method in which soda glass obtained by melting and cooling silica sand and soda ash or caustic soda is dissolved in water. Further, a commercially available sodium silicate aqueous solution or a diluted aqueous solution of sodium silicate that satisfies the above conditions can be used.

The SiO ₂ content here is determined by the relationship between the SiO ₂ pure content in sodium silicate and the water content in the entire system containing sodium silicate, and is not necessarily used as a raw material. Of aqueous sodium silicate solution
₂ Does not indicate content.

The phosphoric acid compound used in the present invention may be any one as long as it exhibits a sequestering action, and typical examples thereof include sodium hexametaphosphate, sodium phosphate, sodium polyphosphate, sodium pyrophosphate and the like. You can These phosphoric acid compounds are added for the purpose of improving the water resistance and acid resistance of the modified surface layer of the cement-based cured product obtained by applying the deterioration inhibitor of the present invention, and sodium hexametaphosphate is particularly preferable for its water resistance and acid resistance. It is a preferable phosphoric acid compound because it exhibits remarkable effects including properties. The addition amount of the phosphoric acid compound having a sequestering effect in the present invention is 0.02 to 15 parts by weight, preferably 0.1 to 9 parts by weight in terms of practical efficiency. If the amount is less than the above amount, the water resistance of the modified surface layer of the cement-based cured product is not improved, on the other hand,
Even if added in an amount exceeding the above amount, not only the water resistance and acid resistance are not further improved, but also the permeability is lowered, so that the effects of the present invention cannot be sufficiently exhibited.

The silicofluorides which can be used in the present invention include barium silicofluoride, potassium silicofluoride,
Magnesium silicofluoride, sodium silicofluoride, zinc silicofluoride, etc. can be mentioned, and the addition amount is 0.0
02 to 15 parts by weight. Such silicofluoride is added for the purpose of further improving the hardness of the modified surface layer of the cement-based cured product obtained by applying the deterioration inhibitor of the present invention,
If the addition amount is less than 0.002 parts by weight, the hardness of the modified surface layer will not be improved, while if added in excess of 15 parts by weight, the hardness of the modified surface layer will not be improved further. However, since the permeability is lowered, the effect of the present invention cannot be sufficiently exhibited.

The surface deterioration inhibitor of the cement-based cured product of the present invention is prepared by sufficiently adding sodium phosphate and a phosphoric acid compound having a predetermined sequestering effect to water, and water and silicofluoride as required. It can be easily prepared by mixing with stirring. The raw materials may be mixed in any order. For example, a phosphoric acid compound or the like may be mixed as an aqueous solution with a sodium silicate aqueous solution, or they may be further diluted with water. However, when other water is mixed with these sodium silicate aqueous solutions, the sodium silicate aqueous solution which is a constituent element of the present invention is treated as being composed of sodium silicate in the system and total water in the system. .

In addition to the above-mentioned components, the surface-curing preventive agent for the hardened cementitious material of the present invention may contain optional components such as a colorant and a viscosity adjusting agent, if necessary, as long as the object of the present invention is not impaired. It can also be added and used.

[0019]

The surface deterioration inhibitor of the cement-based cured product of the present invention may be applied in any shape and history as long as it is a cement-based cured product, but comparison is made from the aesthetic sense of obtaining a uniform coating film without unevenness. It is preferable to use it for a new cement-based cured product.

In order to apply the surface deterioration inhibitor of the cement-based cured product of the present invention and allow it to penetrate into the cured product, a spray, a brush, a roller or the like can be used in the same manner as in ordinary paints.

[0021] The amount of surface degradation inhibitor cementitious cured product of the present invention, it may be suitably selected depending on the state of the application to cement-based cured product is in the range of 100g / m ² ~500g / m ² preferable. A sufficient amount of the modified layer having excellent water resistance and acid resistance can be formed on the surface of the hardened cementitious material by applying a sufficient amount of the solution, allowing it to permeate, and then naturally drying. As a result, this modified layer can continue to protect the cement-based cured product from physical deterioration due to external force and chemical deterioration due to neutralization and the like for a long period of time.

The mechanism by which the modified layer on the surface of the hardened cementitious material obtained by using the surface deterioration inhibitor of the hardened cementitious material of the present invention is excellent in strength, water resistance and acid resistance is still sufficiently elucidated. Although it has not been done, it is considered as follows. The reaction between slaked lime in concrete and sodium silicate is expressed by the following formula: Ca (OH) ₂ + Na ₂ SiO ₃ → CaSiO ₃ + 2N
It becomes aOH. At this time, the silicofluoride becomes a fluoride ion in the aqueous solution and exhibits a catalytic action. The reaction between slaked lime and sodium hexametaphosphate in concrete is

Embedded image Becomes

[0023]

EXAMPLES Next, the present invention will be specifically described by way of examples. Example 1 5 parts by weight of industrial sodium hexametaphosphate was gradually added to 130 parts by weight of warm water at 60 ° C. with stirring to dissolve an aqueous solution of hexametaphosphate, and SiO ₂ / Na ₂ O was added thereto.
100 parts by weight of an aqueous sodium silicate solution having a molar ratio of 3 and a SiO ₂ content of 30% by weight were added and sufficiently mixed with stirring to obtain a surface deterioration inhibitor for the cement-based cured product of the present invention. This surface deterioration inhibitor is colorless and transparent and has a viscosity of 4.6 cp.
It was s / 25 ° C and pH 11.5. The content of SiO _{2 in the} aqueous solution of sodium silicate in the surface deterioration preventing agent was 1
It is 7% by weight, and the amount of phosphoric acid compound is 2.2 parts by weight per 100 parts by weight of the aqueous sodium silicate solution.

Example 2 1 part by weight of sodium hexametaphosphate for industrial use and 0.5 part by weight of sodium silicofluoride were gradually added to 130 parts by weight of warm water at 60 ° C. with stirring to be dissolved in an aqueous solution of hexametaphosphate-sodium silicofluoride. And SiO ₂ / N
100 parts by weight of an aqueous solution of sodium silicate having a molar ratio of a ₂ O of 3 and a SiO ₂ content of 30% by weight was added, and the mixture was sufficiently stirred and mixed to obtain a surface deterioration inhibitor for the cement-based cured product of the present invention. It was This surface deterioration inhibitor is colorless and transparent and has a viscosity of 3.
It was 6 cps / 25 ° C and pH 11.5. The SiO ₂ content of the aqueous sodium silicate solution in this surface deterioration inhibitor was 17% by weight.
The amount of the phosphate compound per part by weight is 0.4 part by weight,
The amount of silicofluoride per 100 parts by weight of this aqueous sodium silicate solution is 0.2 parts by weight.

Example 3 A SiO ₂ / Na ₂ O molar ratio of 1.5 and Si
4 parts by weight of sodium phosphate was added to 100 parts by weight of an aqueous solution of sodium silicate having an O ₂ content of 9% by weight, and sufficiently mixed by stirring to obtain a surface deterioration inhibitor for the hardened cementitious material of the present invention. This surface deterioration inhibitor is colorless and transparent and has a viscosity of 2.3 cp.
It was s / 25 ° C and pH 12.6.

Example 4 The SiO ₂ / Na ₂ O molar ratio is 3.5 and Si
To 100 parts by weight of an aqueous solution of sodium silicate having an O ₂ content of 17% by weight, 1 part by weight of sodium polyphosphate and 0.01 parts by weight of potassium silicofluoride were added, and sufficiently stirred and mixed, and the surface of the cement-based cured product of the present invention was added. A deterioration inhibitor was obtained. This surface deterioration inhibitor is colorless and transparent and has a viscosity of 5.1 cps / 25 ° C.
The pH was 10.9.

Example 5 SiO ₂ / Na ₂ O molar ratio is 2 and SiO ₂
To 100 parts by weight of an aqueous solution of sodium silicate having a content of 6% by weight,
1 part by weight of sodium pyrophosphate was added and mixed sufficiently with stirring to obtain a surface deterioration inhibitor for the cement-based cured product of the present invention. This surface deterioration inhibitor is colorless and transparent and has a viscosity of 2.0 cp.
It was s / 25 ° C. and pH 12.4.

Example 6 The SiO ₂ / Na ₂ O molar ratio is 2 and the SiO ₂
1 part by weight of sodium hexametaphosphate was added to 100 parts by weight of an aqueous sodium silicate solution having a content of 42% by weight, and sufficiently mixed by stirring to obtain a surface deterioration inhibitor for the hardened cementitious material of the present invention. This surface deterioration inhibitor is colorless and transparent and has a viscosity of 7
It was 5 cps / 25 ° C. and pH was 12.3.

Example 7 The SiO ₂ / Na ₂ O molar ratio is 2 and the SiO ₂
0.05 part by weight of sodium hexametaphosphate was added to 100 parts by weight of a sodium silicate aqueous solution having a content of 13% by weight, and sufficiently stirred and mixed to obtain a surface deterioration inhibitor for the cement-based cured product of the present invention. This surface deterioration inhibitor was colorless and transparent, and had a viscosity of 5.5 cps / 25 ° C. and a pH of 12.6.

Example 8 SiO ₂ / Na ₂ O molar ratio is 2 and SiO ₂
To 100 parts by weight of an aqueous solution of sodium silicate having a content of 13% by weight, 8.5 parts by weight of sodium hexametaphosphate were added,
The mixture was thoroughly mixed with stirring to obtain a surface deterioration inhibitor for the hardened cementitious material of the present invention. The surface deterioration inhibitor was colorless and transparent, and had a viscosity of 9.6 cps / 25 ° C. and a pH of 12.6.

Example 9 SiO ₂ / Na ₂ O molar ratio of 2 and SiO ₂
To 100 parts by weight of a sodium silicate aqueous solution having a content of 13% by weight, 2 parts by weight of sodium hexametaphosphate and 0.5 parts by weight of zinc fluorosilide are added and sufficiently stirred and mixed to prevent surface deterioration of the cement-based cured product of the present invention. I got an agent. This surface deterioration inhibitor is colorless and transparent, and has a viscosity of 6.8 cps / 25 ° C, p
It was H12.5.

Example 10 SiO ₂ / Na ₂ O molar ratio is 2 and SiO ₂
To 100 parts by weight of an aqueous solution of sodium silicate having a content of 13% by weight, 2 parts by weight of sodium hexametaphosphate and 11.0 parts by weight of magnesium silicofluoride were added and sufficiently stirred and mixed to prevent surface deterioration of the cement-based cured product of the present invention. I got an agent. This surface deterioration inhibitor is colorless and transparent and has a viscosity of 9.9 cp.
It was s / 25 ° C and pH 12.6.

Comparative Example SiO ₂ / Na ₂ O molar ratio of 3 and SiO ₂
130 parts by weight of warm water at 60 ° C. was added to 100 parts by weight of an aqueous sodium silicate solution having a content of 30% by weight, and sufficiently mixed by stirring to obtain a chemical solution as a comparative example.

Next, ordinary Portland cement and silica sand 6
No. 2 was mixed at a weight ratio of 1: 2, and mortar kneaded to give a water-cement ratio of 65% was cast, and a mortar plate cured at room temperature for 7 days was prepared. The chemical solutions of Examples 1 to 10 and Comparative Example obtained as described above were applied to this mortar board at a rate of 250 g / m ² using a brush, and then at room temperature.
After being dried and cured for a day, a pencil hardness test, an abrasion ring test, and an accelerated neutralization test were performed. Further, the same test body was immersed in water for 7 days, and then dried in a drying container at 30 ° C. for 3 days, and the above-mentioned three kinds of tests were conducted. Furthermore, the same test piece was immersed in a 1% hydrochloric acid aqueous solution for 7 days, washed with water, and dried in a drying container at 30 ° C. for 3 days, and then subjected to a pencil hardness test and an abrasion ring test. For reference, the same test was performed on a mortar plate not coated with the chemical solution.

As for the degree of wear, an H-22 wear wheel was used.
It was expressed as a weight loss [g] after 300 rotations. The accelerated neutralization test was carried out under the conditions of 20 ° C. and a carbon dioxide gas concentration of 20% for 1 month, and the results are expressed as the neutralization depth. The results of these tests are as shown in Tables 1 and 2 below.

[0036]

[Table 1]

[0037]

[Table 2]

As is clear from Tables 1 and 2 above,
The surface deterioration inhibitors of the hardened cementitious cements of Examples 1 to 10 were excellent in carbon dioxide shielding effect, surface hardness strengthening performance, water resistance and acid resistance as compared with the chemicals of Comparative Example. Further, Examples 2, 4, 9 and 10 in which a silicofluoride is blended.
In comparison with the examples in which it was not blended, more excellent results were obtained in terms of hardness.

[0039]

As described above, in the surface deterioration preventing agent of the cement-based cured product of the present invention, a specific amount of a phosphoric acid compound having a sequestering effect is added to a specific sodium silicate aqueous solution. As a result, the following effects are obtained. By applying and permeating the cement-based cured product surface deterioration inhibitor of the present invention onto the surface of the cement-based cured product, a high-strength cement-cured product that can sufficiently protect the cement-based cured product from physical deterioration or damage due to external force is applied. A surface modified layer is obtained. The modified surface layer prevents infiltration of carbon dioxide, acid rain, and other chemicals in the air, and prevents chemical deterioration of the cement-based cured product. Since the modified surface layer has high strength and is particularly excellent in water resistance and acid resistance, the above-mentioned protective effect can be maintained for a long time.

Further, by adding a predetermined amount of silicofluoride to the surface deterioration inhibitor of the cement-based cured product of the present invention,
In addition to the above effects, the strength of the modified surface layer can be further increased.

Claims (2)

[Claims] 1. A 100 parts by weight aqueous solution of sodium silicate having a SiO ₂ / Na ₂ O molar ratio of 1 to 4 and a SiO ₂ content of 5 to 50% by weight, and phosphorus having a sequestering action. An agent for preventing surface deterioration of a cement-based cured product, which comprises 0.02 to 15 parts by weight of an acid compound. 2. The surface deterioration preventing agent according to claim 1, wherein 0.002 to 15 parts by weight of silicofluoride is blended.