JPS5843349B2 - Admixture for mortar and concrete that enhances watertightness and has rust prevention effects - Google Patents

Description

Detailed Description of the Invention: Generally used as waterproofing admixtures for mortar and concrete, there are (1) chloride-based, (2) sodium silicate-based, and (3) siliceous powder-based inorganic compounds. (4) Zirconium compounds, organic type (1) fatty acid type (2)
＞There are many types such as paraffin emulsion (3) asphalt emulsion (4) resin emulsion (5) water-soluble resin, each with filling properties, rapid setting properties, dispersibility,
It has properties such as water reduction, water repellency, and water retention, but most of these properties are exhibited when the water utilization reaction in mortar and concrete is progressing ideally due to its waterproofing mechanism.

However, the water use reaction of cement in mortar/concrete is such that even if sufficient curing (water and temperature is provided) under standard experimental conditions, only about 80 φ of cement particles will water in a period of about 1 month (4 weeks). Not harmonious.

In the case of actual on-site construction, curing is neglected, resulting in insufficient water use, and even when it is generally considered that the cement has hardened, two-thirds of the cement particles remain unreacted. There is also a theory.

In the end, it takes about 2 to 3 minutes for the mortar and concrete to reach a stable state as the appropriate amount of moisture is added and the reaction progresses gradually.
It is said to take years.

In this way, as a practical matter, it is difficult for the mixed waterproofing admixture to fully demonstrate its performance in mortar and concrete with insufficient water availability.

The watertightness of mortar and concrete improves as the cement's water use reaction progresses, so in the case of on-site construction where sufficient curing is difficult, it is recommended to promote the water use reaction of cement to hasten hardening and make the mortar and concrete denser. A waterproofing admixture with a waterproofing mechanism that strengthens the material and improves waterproofness is desirable.

Chloride-based products (mainly calcium chloride-based products) belong to this type of waterproofing mechanism to some extent, but the ferrous hydroxide film, which is stable in an alkaline environment, is destroyed by the peptizing action of chloride ions in chloride. It is known that rusting of reinforcing steel etc. is accelerated.

Furthermore, in recent years, sea sand has been used for mortar and concrete from the bottom of fine aggregate, and the salt adhering to this sea sand causes iron products such as reinforcing bars in mortar and concrete to rust and corrode, causing structures to deteriorate. This has become a serious problem as it has the serious effect of reducing the durability of the metal.

As a countermeasure to this problem, rust preventives containing nitrite as a main ingredient have been proposed, and some of them are in the stage of practical application.

When mixing mortar/concrete using fine aggregate containing salt, it is conceivable to use a waterproofing admixture and a rust preventive agent together to make the mortar/concrete waterproof. In addition to creating management problems and complications such as measurement and addition methods, it is also necessary to thoroughly test and confirm in advance whether there will be any interaction between the waterproofing admixture and the rust preventive agent used together. be.

The present invention promotes the hydration reaction and hardening of cement without containing any chloride, thereby enhancing the watertightness of mortar and concrete, and also contains 0 and 1, which are normally contained in sea sand.
-0.3% by weight of salt (salt content of sea sand used as fine aggregate for mortar and concrete without salt removal treatment is 0.3% at maximum, about 0.24φ on average). The present invention provides an admixture for mortar and concrete that also has a rust effect.

The admixture of the present invention is 50 parts by weight of glycerin triacetate (40-60), 130 parts by weight of calcium acetate (100-160), 75 parts by weight of double-chloride lactic acid steel/monocalcium phosphate (60-90), sodium nitrite or calcium nitrite. 40 parts by weight (20-60) and 5 parts by weight (3-7) of triethanolamine (the numbers in parentheses indicate the range of increase/decrease).

Considering the test results and costs, the most effective amount of admixture to be added is 1 weight of the admixture with the above composition based on the weight of cement in the mortar or concrete.

Next, the effects of each of the above components will be described.

(1) Glycerin triacetate Glycerin triacetate gradually decomposes inside mortar and concrete to generate glycerin and acetic acid.

Glycerin has water-retaining properties and prevents premature drying of mortar and concrete.

When acetic acid is mixed with triethanolamine, which is a hardening accelerator, it promotes the water utilization reaction of cement and effectively accelerates hardening.

(2) Calcium acetate Calcium acetate serves as an auxiliary agent that accelerates the start of the hydration reaction of cement, and like the acetic acid described above, it exhibits an excellent effect in accelerating hardening when mixed with triethanolamine.

Calcium acetate also has the effect of inhibiting rusting and corrosion on the surface of iron products such as reinforcing bars by interacting with other ions coexisting in a corrosive environment.

(3) Double salt lactic acid steel/monocalcium phosphate Double salt lactic acid steel/monocalcium phosphate decomposes into silver lactate and monocalcium phosphate.

Silver lactate interacts with calcium hydroxide produced by the water use reaction of cement to become copper hydroxide and calcium lactate, promoting the water use reaction of cement.

Copper hydroxide fills voids and densifies, while calcium lactate provides added strength and durability.

Monobasic calcium phosphate develops strength gradually, so it is effective over a long period of time.

Furthermore, it is known that monobasic calcium phosphate has the same rust-preventing effect as general phosphates, but the rust-preventing effect is significantly improved when used in combination with nitrite or the like.

(4) Sodium nitrite or calcium nitrite Alkali metal salts or alkaline earth metal salts of nitrite, such as sodium nitrite or calcium nitrite, have been known for a long time as rust preventive agents and are the most common.

In the present invention, among nitrites having a rust-preventing effect, sodium nitrite or calcium nitrite is used because they have a curing accelerating effect without adversely affecting the properties of mortar or concrete, and from the viewpoint of cost.

(5) Triethanolamine Triethanolamine has a curing accelerating effect even when used alone, but in (1) above,
As described in (2), when used in combination with acetic acid or acetate in an appropriate formulation, the effects are significantly improved.

Although the effects of the individual components of the present invention have been mainly explained above, the present invention does not simply utilize the actions and effects of each of these individual components alone, but rather has a significantly significant interaction between these components. The major aim is to take advantage of the synergistic effect caused by the interaction of these two, which produces excellent effects even when added in small amounts.

It has been confirmed that the addition of the admixture of the present invention does not adversely affect the properties of mortar/concrete, such as a significant change in setting time, a decrease in workability, or a decrease in strength.

The results of this test are shown in Tables 1 and 2.

The test results shown in Table 1 show that even when the admixture of the present invention is added, there is no significant difference in coagulation that causes any problems.

Table 2 compares the same mix of concrete (IJ) with and without the admixture of the present invention added in an amount of 1 weight of cement in terms of slump, air content, concrete temperature, and compressive strength.

The test results shown in Table 2 show that even if the admixture of the present invention is added to concrete of the same composition, the properties of fresh concrete such as slump are generally the same, and the compressive strength tends to be increased.

Next, the effect of the admixture of the present invention will be explained by showing examples.Example 1 Water permeability test and water absorption testWater permeability and water absorption tests were conducted according to JIS1404.

The amount of the admixture of the present invention added was 1 weight of cement.

The water permeability test was conducted at a water pressure of 3 Kp/ffl for 1 hour, and the water absorption test was conducted at water immersion times of 1 hour, 5 hours, and 24 hours.

Curing after demolding includes (1) curing in a humid phase with a temperature of 20°C and a humidity of 80°C or more as per JIS 1404 (hereinafter referred to as humidity curing), and (2) a temperature of 20°C and a humidity of 80°C or more. Tests were conducted on two cases: 60% cured in a test room (hereinafter abbreviated as humidity curing).

From the results in Tables 3 and 4, even when kept moist and sufficiently cured, there is a significant difference in both water permeability and water absorption when comparing the admixtures with and without the admixture of the present invention. However, when left to cure in the air, the resistance to water permeation increases and the effect becomes more pronounced.

Example 2 Sea sand with a salt (NaC2) content of 0.3 weight was used, and the admixture of the present invention was added to the cement: sand: water = 1: 2.5: 0.6. (2) No additive added (3) Salt-free sand obtained by removing salt from the above sea sand and no admixtures added. Knead mortar and mold to a size of 4 x 4 x 16 α, During molding, a polished steel rod of φ4 x 100 mm was embedded in the center along the longitudinal direction to prepare a specimen.

After curing the mold for one day, it was removed from the mold and exposed outdoors.

After being exposed outdoors for 6 months, these specimens were destroyed, the polished steel rods were taken out, and the state of rust was observed in detail with the naked eye.

The results are shown in Table 5.

From the results in Table 5, it is recognized that iron products in mortar made using sea sand with a salt content of 0.3 weight by weight are sufficiently rust-proofed by adding the admixture of the present invention.

Example 3 Corrosion prevention test on concrete using sea sand with a salt (NaC2) content of 0.3 weight φ.

In order to remove the influence of surfactants that may have some effect on rust prevention (for example, calcium lignosulfonate, which is used as an AE water reducer, is said to have some rust prevention effect), concrete is Non
AE Ordinary Portland Cement 300 to 9/m8 (manufactured by Nippon Cement Co., Ltd.) Water (tap water) 180 K9/m8
Fine aggregate (sea sand, specific gravity 2.62) 804Kp/m”
Coarse aggregate (produced for rhinoceros, specific gravity 2.64) 1077 to 97m3
It was kneaded with the following composition.

(1) Concrete in which the admixture of the present invention is added by one weight more than the weight of cement (2) In which it is not added (3) Concrete made using sand with zero salinity obtained by removing salt from the sea sand without adding any admixture. was kneaded, molded into a mold of 15 cm x 30 cm, and a reinforcing bar of 1 x 10 crfL polished at the time of molding was embedded in the center to prepare a specimen.

After curing the mold for one day, it was removed from the mold and exposed outdoors.

After being exposed outdoors for 6 months and 2 years, the specimens were destroyed, the reinforcing bars were taken out, and the state of rust was observed in detail with the naked eye.

The results are shown in Table 6.

From the results in Table 6, iron products such as reinforcing bars in concrete using sea sand with a salt content of 0.3% by weight as fine aggregate are:
It is recognized that the addition of the admixture of the present invention provides sufficient rust prevention over a long period of time.

Example 4 Water permeability test and rust prevention test 2 parts of CaCl were added to 1 part of mortar mixing water with the following composition.
．． A corrosive environment for iron products such as reinforcing bars was created by dissolving 5% by weight.

When 21.5% by weight of CaCl in the kneading water is converted into the amount of NaCl contained in the soft carapace, it is approximately 0.3% by weight.

The sand used was a mixture of standard sand from Toyoura, standard sand from Soma, and silica sand for glass manufacturing in the ratio specified in JIS 1404. Cement: Sand: Ca C7
Mortars were kneaded with a ratio of 21.5% aqueous solution-1=3:0.56 (1) with 1% by weight of the admixture of the present invention added to the cement weight, and (2) with no addition.

The specimen for water permeability test was molded to a size of φ15X4CrfL, and the specimen for rust prevention test was molded to a size of 4X4X16crIL as in Example 2.
A 4x100mm polished steel rod was buried.

The specimens for the water permeability test were removed from the mold and cured as specified in JIS 1404, and the water permeability test was conducted at a water pressure of 3 to 50 ml for 1 hour.

The specimens for the rust prevention test were removed from the mold 48 hours after molding and exposed outdoors for 6 months.

After exposure, the specimen was destroyed, the polished steel rod was taken out, and its rusted state was observed in detail with the naked eye.

The results are shown in Table 7.

From the results in Table 7, 0.3 weight φ in terms of NaCl for fine aggregate
When the admixture of the present invention is added to a case where the admixture contains a certain amount of chloride, the watertightness is enhanced even when sufficiently cured due to the synergistic effect between the components of the admixture (as shown in Example 1). (If curing is insufficient, the significant difference in watertightness becomes even more significant) and also has the effect of suppressing rusting and corrosion of iron products such as reinforcing bars caused by chlorides.

Claims (1)

[Claims] 1. Watertightness of mortar or concrete can be improved by adding a composition consisting of glycerin triacetate, calcium acetate, double-chloride lactic acid steel/basic calcium phosphate, sodium nitrite or calcium nitrite, and triethanolamine during mixing of mortar or concrete. A mortar/concrete admixture that can enhance the corrosion of iron products such as reinforcing bars and wire mesh in mortar or concrete and suppress corrosion caused by salt.