JPH0647490B2 - Admixture to enhance watertightness and durability of concrete and mortar - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an admixture for concrete and mortar. More specifically, the admixture is added at the time of kneading concrete or mortar.
Watertightness of concrete and mortar is enhanced, and further resistance to erosion deterioration due to carbonation of concrete and mortar due to carbon dioxide and acid rain is given to enhance the durability of concrete and mortar itself,
Not only when performing sufficient curing, but also when curing is insufficient after casting (curing may be omitted) It is also effective when used for actual construction in the field, concrete or mortar construction in the field of civil engineering The present invention relates to an admixture with a large amount.

[0002]

2. Description of the Related Art Commonly used waterproof admixtures for concrete and mortar include chloride-based, sodium silicate-based, siliceous powder-based, zirconium compounds, etc. There are various types such as fatty acid type, paraffin emulsion type, asphalt emulsion type, polymer dispersion type, water-soluble polymer type, and other inorganic mixture type, organic mixture type, inorganic and organic mixture type. , Each has properties such as quick-setting property, water-reducing property, filling property, and water-repellent property, but most of them have an ideal hydration reaction of cement in concrete or mortar due to their waterproofing mechanism. In that case, the characteristic is exhibited.

However, the hydration reaction of cement in concrete or mortar does not occur even after sufficient curing (giving water and temperature) under experimental standard conditions for a period of about 1 month (4 weeks). It hydrates only about 80%. In actual field construction, the curing is neglected, so that two-thirds of the cement particles remain unreacted, even when it is generally considered to be tentative hardening due to much less hydration. It is said that there is. It is said that it will take about 2 to 3 years for the concrete and mortar to reach a stable state after the appropriate hydration is given and the hydration reaction proceeds gradually.

As described above, as a practical problem, it is considered that a long time is required for the waterproof admixture mixed in the hydrated concrete or mortar to sufficiently exhibit its performance. ing.

In addition, for the deterioration of erosion caused by the neutralization of concrete or mortar and acid rain, the concrete and mortar may be additionally hammered (increased the cover thickness) by an amount commensurate with the service life, and various coating methods may be applied. Has been adopted,
It is necessary to make a decision in consideration of conditions such as price, ease of construction and repair, construction period, etc. Especially, as the coating material, (1) there should be no defects such as pinholes, etc. (2) adhesion to base concrete or mortar Being solid (3) Being able to apply the coating as it is with concrete or mortar structure (4) Being able to follow the shape of the concrete or mortar structure being coated (5) Temperature change It is necessary to satisfy the conditions such as (6) being thermally stable within the temperature range of the environment in which the covering material is used, etc. In reality, all of these conditions are satisfied. In many cases, it is impossible to find the material to be used, and it is unavoidable to select the material and construction method on the premise of regular repairs and repairs.

[0006]

The watertightness of concrete and mortar increases with the progress of the hydration reaction of cement. Therefore, the hydration reaction of cement should be improved especially in the case of on-site construction where sufficient curing cannot be achieved. A waterproofing admixture having a waterproofing mechanism that accelerates concrete and mortar to be dense and hard to enhance watertightness is desirable.

The chloride system belongs to such a waterproofing mechanism to some extent, but is stable in an alkaline environment due to the deflocculating action of chloride ions in the chloride.
Since the iron film is destroyed and rusting of reinforcing bars is promoted, the amount of chloride is strictly regulated by JIS. Therefore, the use of chloride must be avoided.

Further, in addition to the neutralization of concrete and mortar by carbon dioxide in the air, in recent years, the durability of concrete and mortar has been remarkably reduced due to erosion deterioration due to acid rain. .

Detailed Description of the Invention

In order to deal with this, an increase in cover thickness and various coating methods have been adopted, but basically, concrete and mortar itself are also provided with performance to cope with deterioration of external environmental conditions. It is considered necessary to improve the durability of concrete and mortar structures.

As is well known, the best way to increase the durability of concrete or mortar is to increase its compactness and reduce voids in the concrete or mortar that cause the penetration of erodible substances.

[0011]

Means for Solving the Problems The present invention addresses the above problems, and is well known as the main component of a hardening accelerator, calcium nitrite, copper lactate that promotes the hydration reaction of cement, and the hydration reaction of cement. Glycerin and sodium lactate, which help maintain the viscosity, and g-butoxy bis titanium, which imparts corrosion resistance and water repellency to concrete and mortar, are used as admixtures.

A remarkably significant interaction is observed between these components, which accelerates the hydration reaction of cement and enhances the watertightness of concrete and mortar, as well as the insolubility,
Generates a corrosion resistant substance and fills voids in concrete or mortar to make it solid and makes it difficult for erosive substances such as carbon dioxide and acid rain to permeate. Increases the durability of mortar and mortar.

[0013]

Next, the action and effect of each component will be described.

Calcium Nitrite Calcium nitrite accelerates the hydration reaction of cement and is used as a well-known main component of a hardening accelerator which replaces the chloride admixture of concrete and mortar.

Copper Lactate Copper lactate acts on calcium hydroxide produced by the hydration reaction of cement to form copper hydroxide and calcium lactate to accelerate the hydration reaction of cement. Copper hydroxide fills voids to make them solid, and calcium lactate contributes to strengthening.

Glycerin and Sodium Lactate Both glycerin and sodium lactate have water retention properties, and by using both together, evaporation of water inside concrete and mortar is suppressed and premature drying is prevented. Helps sustain hydration.

G-n-butoxy bis-titanium G-n-butoxy bis-titanium is gradually hydrolyzed in concrete and mortar, and titanium oxide is deposited to fill voids, giving corrosion resistance and water repellency to concrete and mortar. Give.

Although the action and effect of each component of the present invention have been described above, even if a single component is added, a great effect cannot be obtained.

In the present invention, not only the actions and effects of these individual components alone are used as they are, but a significantly significant interaction is observed between these components. Therefore, a synergistic effect due to the effective and appropriate combination of multiple components is obtained. The aim is to obtain excellent effects even with a small amount of additives.

By adding the admixture of the present invention,
According to JIS A62, the properties of concrete and mortar are not adversely affected such as remarkable change in setting time, decrease in workability, increase / decrease in entrained air amount and decrease in strength.
It confirmed by performing the test according to 04.

That is, based on 5.1.1 of JIS A6204, three cements of Mitsubishi, Onoda, and Sumitomo, which are arbitrarily selected from three different manufacturing companies, are selected, and three kinds of cements are mixed in an equal amount, and 321 kilograms of cement are mixed. Cubic rice, tap water 19
Specimens were prepared as shown in Table 1 using 1 kilogram par cubic rice, fine aggregate 813 kilogram par cubic rice, coarse aggregate 919 kilogram par cubic rice, and AE water reducing agent 0.803 kilogram par cubic rice.

[0022]

[Table 1]

From the above, when the admixture of the present invention was added and the admixture of the present invention was not added, the test results are shown in Table 2. Minutes, 10 minutes for closing, 0.5 cm for slump, 0.2% reduction in air volume,
The compressive strength was 32 kg per square centimeter after 7 days and 36 kg per square centimeter after 28 days. (* The admixture of the present invention was added in an amount of 1% by weight based on the mass of cement. The same applies to the amount added in the following examples.)

[0024]

[Table 2]

From the test results shown in Table 2, even if the admixture of the present invention is added to concrete having the same composition, the properties of fresh concrete such as setting, slump, and air content can be regarded to be about the same, and that of hardened concrete. It tends to be enhanced in terms of compressive strength, and it is confirmed that the addition of the admixture of the present invention has no adverse effect.

[0026]

EXAMPLES Examples of the admixture according to the present invention will be described below. Calcium nitrite 140 parts by weight (120-160) Copper lactate 30 parts by weight (20-40) Glycerin 120 parts by weight (100-140) Sodium lactate 60 parts by weight (40-80) G-n-butoxy bis-titanium 50 parts by weight An admixture was prepared as an aqueous solution by using each part by weight of (40 to 60) (the numbers in parentheses indicate the range of increase and decrease).

The amount added is considered to be the most effective amount in this example, considering the results of the test and the cost, and the admixture having the above composition is added to the cement weight in the concrete or mortar at 1%. The following tests were conducted as weight%.

(1) Water Permeation Test and Water Absorption Test Specimens were prepared according to JIS A1404, demolded 48 hours after molding, and then for 19 days. (A) Temperature of 20 ° C. and humidity of 80 according to JIS A1404
Cured in a humidity box of not less than 5% (hereinafter abbreviated as "moisture curing") (b) Assuming insufficient curing, temperature 20 ° C, humidity 6
According to JIS A1404, there are two cases of curing in a test room of 0% or less (hereinafter abbreviated as dry air curing).
Water permeability and water absorption tests were conducted. The test results are as shown in Tables 3 and 4.

[0029]

[Table 3]

[0030]

[Table 4]

From the results shown in Tables 3 and 4, even when the wet state was maintained and sufficient curing was carried out, the admixture of the present invention was compared with that without the admixture, and the water permeability and water absorption were compared. Although there is a significant difference in sex, when left to cure in the air, the resistance to water permeation increases and the effect of improving watertightness becomes remarkable.

(2) Neutralization test The test specimen was made by molding concrete with the same composition as in Table 1 and, after 24 hours, demolding,
For the subsequent 27 days, the test was conducted in two cases of moisture curing and dry curing as described above. The test started the neutralization acceleration test in the atmosphere of carbon dioxide concentration of 5%, temperature of 30 ° C, and humidity of 60%, and after the test material age, the specimen was split and the neutralization depth was determined by the phenolphthalein method. It was measured. The test results are shown in Table 5.

[0033]

[Table 5]

From the results shown in Table 5, even when the wet state is maintained and the mixture is sufficiently cured, the one with the admixture of the present invention has a smaller neutralization rate than the one without the admixture and is neutralized. It was confirmed that the inhibitory effect was improved, but the neutralization inhibitory effect was further increased when left to cure in the air.

(3) Acid resistance test Specimen is JIS A
Molded mortar prepared in accordance with 1404, demolded after 24 hours, and then for 27 days, in the same manner as above, two cases of moisture curing and dry curing, ASTM C267
The test was conducted according to. The immersion test solution used in the test has a pH
Using the test value of the test piece immediately before immersion in a 3.0 sulfuric acid solution, the weight, compressive strength and appearance of the test piece immersed in this test solution after the passage of the immersion material age were compared. Table 6 shows the test results for the weight reduction rate, Table 7 shows the test results for the compressive strength ratio, and Table 8 shows the test results for the change in appearance over time.

[0036]

[Table 6]

[0037]

[Table 7]

[0038]

[Table 8]

From the results shown in Tables 6, 7, and 8, the degree of erosion in which the hydrated product of cement reacts with acid to decompose shows that the admixture of the present invention is also eroded with the lapse of immersion time. However, the degree of erosion is obviously milder than that of the additive-free one, and the more the immersion material ages and the less the curing is, the more remarkable the difference between the additive and the additive-free of the present invention becomes. I was able to confirm that it would come.

[0040]

Summarizing the above examples, by adding the admixture of the present invention, the watertightness and neutralization resistance of concrete and mortar and acid rain can be achieved by the synergistic action between the composition components of the admixture. (PH of acid rain in Japan
The value is about 4.1 to 5.9), and the corrosion resistance due to erosive substances can be enhanced, and the durability of concrete or mortar itself becomes large. This effect becomes remarkable in the case of concrete or mortar that is not well-cured on site and has a great effect on enhancing watertightness and durability.

Claims (1)

[Claims] 1. An admixture for enhancing watertightness and durability of concrete and mortar comprising a composition of calcium nitrite, copper lactate, glycerin, sodium lactate and g-butoxy bis titanium.