JPH0649604B2 - Hydraulic material composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydraulic material composition having a novel composition. More specifically, it relates to a hydraulic material composition which does not corrode coexisting steel materials even when sand containing a steel material corrosive component such as chloride, or seawater is used for molding.

[Conventional technology]

A steel material such as a reinforcing bar used as a reinforcing material for a hardened cement is usually protected from corrosion by a passivation film formed on the surface of the hardened cement because the hardened cement exhibits a strong alkalinity. However, when a corrosive substance such as chloride coexists in the hardened cement product, the action of chlorine ions or the like destroys the passivation film formed on the surface of the steel material and the corrosion of the steel material progresses.

When river sand is used as fine aggregate for concrete,
It is rare that a corrosive substance such as a chlorine compound is mixed in the hardened cement, and no measures have been taken to prevent corrosion of the steel material in the hardened cement. However, in recent years, there has been a shortage of high-quality river sand, and in place of this, sea sand is often used as a fine aggregate for concrete. By using this sea sand, chloride is inevitably mixed in the cement hardened body, and the chloride causes corrosion of the steel material in the hardened body, which ultimately shortens the life of buildings. is there.

As described above, the corrosion of steel materials caused by corrosive substances such as chlorides mixed in the cement hardened body by using sea sand has become a serious problem recently.

Further, there is also a problem that a steel material embedded in a hardened cement body that is in a state of coming into contact with a corrosive environment, particularly seawater and repeatedly dried and wet, is gradually corroded by a corrosive component penetrating into the hardened cement body.

When sea sand is used, a method of removing salt by washing sea sand is known as a method for preventing corrosion of steel materials by chlorides mixed in a cement hardened body. However, a very large amount of water is required to sufficiently reduce the concentration of chlorine ions in sea sand by washing with water. Therefore,
There are problems that the manufacturing cost of the fine aggregate increases, and fine powder in the sea sand flows out, so that a good fine aggregate cannot be obtained.

In addition, as a method of preventing corrosion of steel materials in a cement hardened body due to contact with corrosive environments such as seawater, thickening the concrete cover to suppress the entry of corrosive substances such as chlorides from the outside, A method of finishing the surface layer with a resin-based paint, tiles, etc. is known. This method is an effective method against invasion of chlorides from the outside, but as in the case of using sea sand or a corrosive admixture such as calcium chloride, cement is used. It is ineffective when a corrosive substance is present in the cured body from the beginning.

The following method is also known as a method for preventing corrosion of the steel material in the hardened cement product.

(A) A method using a steel material having a zinc-plated surface.

(B) Method using steel material coated with synthetic resin.

However, the method (a) is expensive, and when the steel material is welded at the work site, the welded part cannot be plated, and if no treatment is applied to the welded part, However, there is a problem that corrosion occurs from this portion, and the corrosion is more severe than that without zinc plating. The method (B) has a problem that the cost is high and the adhesion between the coated steel material and the hardened cement material is not good.

In addition to the method of imparting anticorrosion property to the steel material as described above, a method of controlling corrosion of the steel material by adding nitrite to the hardened cement has been proposed. Although this method suppresses the corrosion of the steel material in the cement hardened body to some extent, it cannot be said that the effect is sufficient. In particular, if the blending amount is insufficient, local corrosion (so-called pitting corrosion) may occur.

It is hard to say that all of the above methods are satisfactory when judged comprehensively in terms of corrosion resistance and price.

[Problems to be solved by the invention]

An object of the present invention is to provide a hydraulic material composition having a novel composition.

Another object of the present invention is a hardened cement body that does not corrode coexisting steel materials even when sand or seawater containing a corrosive component such as chloride is used in molding, or when it repeatedly contacts dry and wet with seawater. The present invention is to provide a hydraulic material composition.

Still another object of the present invention is to provide a hydraulic material composition which is not corrosive to steel materials as described above and whose setting time of cement hydration is not much different from that of ordinary cement.

Still another object of the present invention is to provide a hydraulic material composition that does not corrode steel materials and does not delay the development of strength of hardened cement.

Further objects and advantages of the present invention will be apparent from the following description.

[Means and Actions for Solving Problems]

According to the invention, such an object and advantage of the invention is characterized in that it contains zinc oxide with an average particle size of at least 20 μm in a proportion of 0.01 to 2.0% by weight with respect to the cement. Achieved by a hydraulic material composition.

The zinc oxide used in the present invention should have an average particle size of at least 20 μm, preferably 30 to 1000.
μm, particularly preferably 50-500 μm.

Further, zinc oxide needs to be contained in an amount of 0.01 to 2.0% by weight, preferably 0.05 to 0.
It is 5% by weight.

As described above, by containing zinc oxide having the above particle size in the above ratio, the composition of the present invention prevents corrosion of the steel material and the basic physical properties required for cement, such as hardening characteristics. Can be maintained. That is, when the content of zinc oxide having an average particle size of at least 20 μm is less than 0.01% by weight with respect to the cement, it is not possible to sufficiently prevent corrosion of the steel material in the hardened cement body,
On the other hand, the zinc oxide content of the particle size is 2.0 with respect to the cement.
When it exceeds the weight%, it is suitable for corrosion protection of steel,
When relatively fine zinc oxide having an average particle size of about 20 μm is added, hydration of the cement is suppressed, the setting time becomes longer, and the strength development of the hardened cement product is delayed, which causes problems.

Examples of the cement used in the present invention include various portland cements, blast furnace cements, and fly-ash cements.

The composition of the present invention is, for example, a powdery composition composed of cement and zinc oxide, a mortar composition composed of cement, zinc oxide and fine aggregate or a concrete composed of cement, zinc oxide, fine aggregate and coarse aggregate. It can be in the form of a composition for use. Further, the composition of the present invention is in the state of a wet kneaded product containing a sufficient amount of water in the composition of the composition as described above to further harden the cement in order to produce a steel-reinforced cement hardened product. You can also

Zinc oxide can be dry-mixed with cement, or can be added by dry-mixing when clinker is ground together with gypsum into cement. Zinc oxide is a commonly used admixture (material) such as a water reducing agent, A
E It is also possible to add it to the cement by mixing it with a water reducing agent or the like. The composition of the present invention can also be prepared by a method of mixing a cement containing zinc oxide with a conventional cement.

Furthermore, zinc oxide can also be added in the concrete or mortar manufacturing process in, for example, ready-mixed concrete plants. The timing of addition is not particularly limited as long as it is during kneading.

According to the research conducted by the present inventor, as the zinc oxide used in the present invention, a compound that can give zinc oxide by causing thermal decomposition at the temperature when firing is performed at a concentration of 800 ° C. or higher, for example, Zinc oxide obtained by heating basic zinc carbonate or zinc oxalate at a temperature of 800 ° C. or higher and calcining, or zinc oxide obtained by calcining zinc oxide at a temperature of 800 ° C. or higher. It was revealed that zinc oxide produced by firing fine particles of zinc oxide smaller than 20 μm at a temperature of 800 ° C. or higher is extremely excellent in terms of the above-mentioned anticorrosion effect and curability. Firing
It is carried out according to a method known per se, preferably in an electric furnace, a rotary kiln or the like.

Further, upon firing, it is possible to allow copper oxide to coexist with zinc oxide. The presence of such oxides of copper and lead not only promotes the firing of zinc oxide having an average particle size of at least 20 μm, but also acts advantageously on corrosion protection for steel materials.

It is needless to say that the fine aggregates, coarse aggregates, and additives used in the production of mortar or concrete can be those commonly used. However, according to the present invention, it is possible to use unsanded sea sand or an aggregate containing chloride. In addition to the water that is usually used for kneading,
Seawater can also be used.

That is, as long as the steel anticorrosive mortar or concrete of the present invention is used, even if sea sand is used as long as it has a normal chloride content, or even by using seawater as kneading water, cement It is possible to prevent steel corrosion in the hardened body.

Hereinafter, the present invention will be described in more detail with reference to Examples, Comparative Examples and Reference Examples.

〔Example〕

Examples 1 to 3, Comparative Example 1 and Reference Example 1 Normal Portland cement: Toyoura standard sand weight ratio of 1:
3. Water-cement ratio was 0.8, seawater was used as kneading water, and zinc oxide ore powder with an average particle size of 55 μm was added to the cement at the addition rate shown in Table 1 and kneading Was carried out to produce a mortar.

20x20x1 in a 40x40x10mm plywood mold
A steel plate whose mm surface had been polished and degreased was put therein, and the mortar was filled in the mold and cured at 20 ° C. for 2 days in a humid air of 90% humidity, and then the mold was removed to obtain a test piece.

After visually observing the hardening state of the specimen, it was cured in saturated steam at 65 ° C. for 7 days, 14 days, 28 days, 56 days, 91 days, and then split using a compression tester to obtain a steel plate. Then, the area ratio of the rusted portion of the steel sheet was measured. The results are shown in Table 2.

The setting test was carried out according to the physical test method for JIS R 5201 cement.

Examples 4 to 6 and Comparative Example 2 In Example 2, exactly the same as Example 2 except that zinc oxide powder having an average particle diameter of 55 μm was replaced with zinc oxide powder having an average particle diameter shown in Table 3. I went to. The results are shown in Table 4.

Examples 7 to 9 and Comparative Examples 3 and 4 zinc oxide having an average particle size of 2 μm at the temperature shown in Table 5,
After firing in an electric furnace for 0.5 hour, the powder was pulverized to produce zinc oxide having a particle size shown in Table 5. These zinc oxides were replaced with the zinc oxides of Example 2, and the other conditions were the same as in Example 2. The results are shown in Table 6.

Examples 10 and 11 and Comparative Examples 5 and 6 are examples when a commercially available water reducing agent is used in combination.

Commercially available water reducing agent A (lignin sulfonic acid type) or water reducing agent B (alkylallyl sulfonic acid type) was added to the composition of Example 8.
Was added in the ratio shown in Table 7, and the water cement ratio was 0.6.
Tested as 0. The results are shown in Table 8.

[Effects of the Invention] By using the hydraulic material composition of the present invention, it is possible to prevent corrosion of the steel material in the hardened cement product in a corrosive environment.

That is, even if unsanded sea sand is used as the fine aggregate, even if sea water is used as the kneading water, it is possible to prevent corrosion of the steel material in the cement hardened body, and to include ordinary chlorides. A reinforced concrete structure can be constructed without any change from the case of using fine aggregate or kneading water.

Further, it is possible to effectively prevent the corrosion of steel even in a structure such as a marine concrete structure in which chloride is likely to enter from the outside.

Furthermore, it becomes possible to use an admixture containing chloride in reinforced concrete. Furthermore, as compared with the conventional steel material corrosion protection technology, it is possible to achieve corrosion protection of steel material at a lower cost.

Further, zinc oxide having an average particle size of 20 μm or more does not adversely affect the hardened cement product, such as delaying the setting and hardening of cement.

Claims (5)

[Claims] 1. A hydraulic material composition characterized by containing zinc oxide having an average particle size of at least 20 μm in an amount of 0.01 to 2.0% by weight with respect to cement. 2. The composition according to claim 1, wherein the hydraulic material composition further contains fine aggregate in addition to cement and zinc oxide. 3. The composition according to claim 1, wherein the hydraulic material composition further contains fine aggregate and coarse aggregate in addition to cement and zinc oxide. 4. The composition according to any one of claims 1 to 3, wherein the hydraulic material composition further contains water in an amount sufficient to cure the cement. 5. Zinc oxide particles having an average particle size of at least 20 μm are 80 particles of zinc oxide having an average particle size smaller than 20 μm.
The composition according to claim 1, which is produced by firing at a temperature of 0 ° C or higher.