JPS63260879A - How to prevent deterioration of cement structures - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for preventing the deterioration of cement-based structures, and in particular, to a method for preventing the deterioration of cement-based structures, and in particular, to provide a cement-based porous structure with excellent weather resistance and water permeation resistance after wear. The present invention relates to a durable deterioration prevention method that provides the following properties.

[Conventional technology and its problems]

In recent years, aging deterioration of cement-based structures has become a significant social problem. This is mainly due to the depletion of resources, the use of undesirable sea sand and crushed stone as aggregates, and the construction requirements associated with pumping hydraulic cementitious compositions to provide fluidity. This is thought to be due to the addition of more water than necessary to the composition. In such cement-based structures, for example.

(1) Rust formation of internal reinforcing bars due to neutralization of the structure; (2) Acceleration of rusting of reinforcing bars due to salt in the raw materials used or salt entering from the outside.

(3) The use of expandable aggregates causes phenomena such as cracking in hardened structures due to expansion and pop-outs, and these phenomena appear to accelerate the deterioration of cementitious structures. It is.

As a means to prevent such deterioration, conventional methods include forming a coating film of an organic polymer material such as epoxy resin on the surface of concrete structures to prevent the intrusion of water, gas, etc.; A method of forming a waterproof layer inside a cement structure by coating the surface of the structure with a silicone oligomer or polymer dissolved in an organic solvent, or with an aqueous solution of methyl siliconate or a silane monomer, impregnating it, and curing it. is proposed.

However, the former method is not only expensive because it cannot provide a satisfactory shielding effect unless the coating is thick, but also has problems with weather resistance depending on the material.
It is not always a satisfactory method as it is easily damaged by external forces. Also.

Generally, there is a strong tendency to dislike that the appearance of cement structures is impaired by such organic coatings.

On the other hand, the latter method was developed as a method to provide waterproof protection while making use of the texture of the structure, but this method also has problems with deterioration prevention performance such as waterproofness and heat insulation, and durability. Satisfactory practicality cannot be expected.

Therefore, an object of the present invention is to provide a practically desirable deterioration prevention method for forming a protective layer on cement-based structures that has excellent waterproof properties, heat insulation properties, etc. over a long period of time, and has particularly excellent weather resistance. It is in.

[Means for solving problems]

As a result of repeated experiments and research on an effective method for achieving the above object, the present inventors found that the number of carbon atoms in an alkyl group is 8 to 8.
12 alkyltrialkoxysilane and 3 to 3 carbon atoms
A composition obtained by mixing a silane having an alkyl group of No. 6 in a specific range ratio has good permeability into the interior of a cement-based porous structure.

In addition, the cured product has desirable water and heat insulation properties, suppresses alkali aggregate reaction, and effectively prevents salt damage caused by common salt, sulfur salt, etc., and is especially durable (weather resistance). It was also discovered that a deterioration prevention layer having excellent water permeation resistance after abrasion can be formed, and the present invention was completed based on this knowledge.

That is, the present invention provides a weight range of 60:40 to 40:60 between an alkyltrialkoxysilane having an alkyl group having 8 to 12 carbon atoms and an alkyltrialkoxysilane having an alkyl group having 3 to 6 carbon atoms. To provide a method for effectively preventing deterioration of a cement structure by applying a mixture in a proportion to the surface of the structure, impregnating it, and hardening it.

Cement-based structures in the method of the present invention include cement-based structures such as mortar and concrete using cement as a binder, as well as ceramic materials such as stone, bricks and tiles, and inorganic porous materials such as lightweight aggregates. Includes the body.

In the method of the present invention, the alkyltrialkoxysilanes used in combination for modifying the cement porous structure have the following general formula: % formula % (wherein R1 is an alkyl group, OR, is a lower alkoxy group (usually selected from a methoxy group and an ethoxy group), and the first component is an organosilicon compound represented by The second component is a silane having a group in which R1 has 3 to 6 carbon atoms.
These are silanes having an alkyl group of

In general, silane compounds with a small number of carbon atoms in R have good permeability into pores, but are inferior in water-blocking properties, heat-blocking properties, durability, etc. On the other hand, if the number of carbon atoms is too large, the silane compounds It has poor internal permeability, and its hydrophobicity cannot be used to impart satisfactory water-blocking properties, heat-blocking properties, etc. to porous structures.The reason is not clear, but the alkyl group is too large. This is thought to be because penetration into the porous layer becomes difficult, condensation of silanol groups is hindered due to steric hindrance, and orientation of alkyl groups is also insufficient.

The present invention has good hydrophobicity or water repellency, but has a relatively large number of carbon atoms (8 to 1
2) The first higher alkyltrialkoxysilane component having an alkyl group and a relatively small number of carbon atoms that have good permeability into cement porous structures but have poor water-blocking properties, heat-blocking properties, durability, etc. When combining a second lower alkyltrialkoxysilane having an alkyl group (having 3 to 6 carbon atoms) in a specific mixing range ratio, the disadvantages of each component are mutually covered by the advantages of the other component, and both components is based on the discovery that anti-degradation functional compositions can be formed that combine the desirable properties of each of the following. Alkyl groups with 12 carbon atoms, 1 carbon atom,
The use of silanes (2) is not preferred because a satisfactory deterioration prevention effect cannot be obtained.

In addition, in order to obtain the desired deterioration prevention performance, it is important to mix the first silane component and the second silane component in a specific mixing ratio, that is, in a weight range ratio of 60:40 to 40:60. be. When it deviates from this range, the above-mentioned satisfactory mixing effect cannot be obtained. For example, when the first component higher alkyltrialkoxysilane exceeds 60% by weight based on the composition, the composition The object of the present invention cannot be achieved because the penetration depth of the second component is completely insufficient, and if the second component, lower alkyltrialkoxysilane, exceeds 60% by weight based on the composition, cement thread ends, Although sufficient penetration into the interior can be obtained, it is not desirable because it does not provide a high degree of water-shielding and heat-shielding protection against deterioration.

These mixtures are prepared by selecting the respective silane components to be used in combination depending on the type of cement structure, its porous state, or the desired physical properties, etc., and adjusting the mixing ratio of both silane components as appropriate. A desired anti-deterioration effect can be achieved by selecting the desired one. Further, the mixing ratio of these is generally widely and preferably around 1 equivalent weight.

The silane compounds used in the deterioration prevention method of the present invention include octyltriethoxy (or methoxy) silane, decyltriethoxy (
or methoxy) silane and dodecyltriethoxy (or methoxy) silane. Examples of the silane compounds as the second component include propyltriethoxy (or methoxy) silane, butyltriethoxy (or methoxy) silane, and hexyltriethoxy (or methoxy) silane. Among these silane compounds, there is no essential difference between methoxylated compounds and ethoxylated compounds both chemically and physicochemically, and no substantial differences are observed in terms of their actions and effects.
The above-mentioned silane compounds may be used alone or in combination of two or more types in each group.

These silane compounds have low viscosity and low surface tension.7) The silane mixed composition can be applied as is to the surface of a cement structure.

It may be applied after being diluted with a suitable solvent, for example, methyl alcohol or ethyl alcohol, to a weight concentration of, for example, 10 to 50% by weight, and reaction promoters such as acids, alkalis, and metal salts. can be used in addition to the composition.

The silane compound applied to the surface of the structure penetrates into the structure, comes into contact with moisture, and is thereby hydrolyzed into highly reactive silanol. This silanol reacts with, for example, one-OH groups and other silanol groups present on the silica surface, undergoes dehydration condensation, forms strong siloxane bonds, and becomes a polymer. are arranged on the surface, and it is presumed that their hydrophobicity effectively prevents water from entering.

[Effect]

According to the method of the present invention, silanes applied to the surface of a cement structure penetrate deep enough from one surface, dehydrate and condense to form a hardened layer in which highly hydrophobic alkyl groups are densely arranged. , the intrusion of water, salt, etc. from the outside is effectively prevented. In addition, as shown in the examples below, these silane mixtures.

Unlike conventional silicone oligomers, it has a reinforcing effect similar to that seen in polymer cement.

〔Example〕

Next, the present invention will be explained in more detail using a specific example. Note that parts and percentages in the examples are by weight unless otherwise specified.

In addition, in order to test the deterioration prevention performance of the silane compounds according to the method of the present invention on cement structures, the following mortar and concrete were prepared as one representative cement structure, and these were used as test specimens to test various types of silane compounds. Physical properties were measured.

[Mortar] A composition prepared by mixing cement: sand: water in a mixing ratio of 1: 2: 0.65 was poured into the molds of various test specimens, and the molds were removed after 2 days and used thereafter. , temperature 20±2℃,
The specimens were cured for four weeks at a relative humidity of 65±5%.

[Concrete] Cement 425) tg, fine aggregate 704 kg, coarse aggregate 10
35kg, AE water reducing agent 1.062kg, its auxiliary agent 16.
5 g of water and 1 kg of water (40% of cement) were kneaded to form a mixture of 10 x 1. It was poured into a formwork of OX 10QI, removed from the mold after 2 days, and kept at a temperature of 20±2℃.
A specimen was prepared by curing for four weeks at a relative humidity of 65±5%.

Next, using these specimens, the deterioration prevention performance of various silane compounds on cement-based structural materials was evaluated by the following test method.

a) Apply a predetermined amount of silane to the entire surface of a mortar specimen with a penetration depth of 10 x 10 x 20 a*, leave it for 7 days at a temperature of 20 ± 2°C and a relative humidity of 65 ± 5%, and then split it. Wet the split surface with water and measure the depth of the water-filled area (the boundary line).

b) Apply a predetermined amount of silane to the entire surface of a mortar specimen with a water absorption rate of 4X4X16Q11, at a temperature of 20±2℃ and a relative humidity of 65±5%.
After being left under these conditions for 7 days, the sample was submerged in water, and the water absorption rate was determined from the weight increase after 30 days.

C) Water permeability test A predetermined amount of silane was applied to the entire surface of a 10 x 10 x 10 cm concrete specimen, and after being left for 7 days at a temperature of 20 ± 2°C and a relative humidity of 65 ± 5%, JISA691 was applied.
The progress of water permeability up to 30 days is measured using the water permeability test method of 0.

d) Heat insulation-1 Silane was applied at a predetermined ratio to one side of a mortar specimen having a diameter of 6.5 am and a thickness of 0.5 am, and the temperature was 20±2°C.

After being left for 7 days under conditions of relative humidity of 65±5%, the amount of chlorine ion permeation was measured by the method shown in the road bridge guidelines (draft) by the Concrete Institute of Technology.

e) Heat insulation - 2 A predetermined amount of silane was applied to the entire surface of a 4 x 4 x 16 cm mortar specimen, and the temperature was 20 ± 2°C and the relative humidity was 65 ± 5.
% for 7 days, the specimen was completely immersed in saturated saline, and the weight increase of the specimen was measured over time.

In addition, the specimen after one year is split open and the depth of penetration of chlorine ions into the interior is measured by fluorescein color reaction.

f) Alkali resistance 4 x 4
After being left for 7 days under the condition of 5% calcium hydroxide, the specimen is completely immersed in a saturated calcium hydroxide solution, and the weight increase of the specimen is measured over time.

g) Durability (weather resistance) The specimen whose water absorption rate was measured according to the above b)
After running it in a carbon arc accelerated weathering tester specified in SK-5400 for 2000 hours, it was taken out and placed in clean water, and the water absorption rate was measured after 30 days.

h) Protection in polishing environment A predetermined amount of silane is applied to the entire surface of a 10 x 10 x 20 cm mortar specimen, and after being left for 7 days at a temperature of 20 ± 2 °C and a relative humidity of 65 ± 5%, a width of 2 cm is applied. , depth 2■
Insert two grooves vertically and horizontally, J Is A 6910
Measured using the water permeability test method.

In addition, when applying the combined silane compounds to the surface of the specimen,
A predetermined amount of each silane compound was mixed with 4 ml of ethyl alcohol.
The total amount of silane compounds applied was 3%.
00 g/rl.

Examples 1-15. Comparative Examples 1 to 8 Deterioration prevention mixed compositions of various proportions of a first component of a higher alkyltrialkoxysilane and a second component of a lower alkyltrialkoxysilane were prepared as a 40% solution of ethyl alcohol, and these were added to the above-mentioned specimen. It was coated and applied, and various tests were conducted. The first and second components used, their usage ratios, and their measurement results are summarized in Table 1.

The abbreviations for the test materials in the table are as follows.

C1: Probyltriethoxysilane C4 Nibutyltriethoxysilane C,: Hexyltriethoxysilane C1: Octyltriethoxysilane C□. : Decyltriethoxysilane C12: Dodecyltriethoxysilane As is clear from the results in Table 1, the first silane component and the second silane component used in the method of the present invention are mixed in a ratio of 60:40 to 40:6.
In particular, the mixture (example) with a weight range ratio of 0.
Durability [Test method g)) and water permeation resistance after wear (Test method h)
)) It can be seen that it exhibits excellent performance in both cases.

Durability [Test method item g)], that is, maintenance of waterproof performance,
The water absorption rate is less than 1/2 that of the blank, and the water permeability after abrasion [test method h)], that is, the ability to maintain the protective ability even when the surface is abraded, is less than the water permeability of the blank. It is 1/3 or less.

Furthermore, it is clear that if the mixing ratio is outside the mixing range of the present invention, excellent performance that satisfies both durability and water permeability after abrasion cannot be obtained.

Claims (1)

[Claims] 1. 60:4 of an alkyltrialkoxysilane having an alkyl group having 8 to 12 carbon atoms and an alkyltrialkoxysilane having an alkyl group having 3 to 6 carbon atoms.
A method for preventing deterioration of a cementitious structure, comprising applying a mixture in a weight range of 0 to 40:60 to the surface of the cementitious structure, impregnating it, and curing it.