JPH0825778B2 - Method for producing seawater-resistant cement material and seawater-resistant mortar or concrete - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a seawater-resistant cement material, particularly a cement material having high resistance to corrosion of seawater and a seawater-resistant mortar or concrete.

(Prior Art) Conventionally, erosion damage of concrete structures due to seawater has occurred in various places, and infiltration of seawater into concrete also corrodes and damages internal reinforcing bars, resulting in the collapse of concrete structures.

When hardened concrete containing various cements is immersed in seawater, erosion progresses with the passage of time, and the residual strength ratio due to erosion significantly decreases in the 10-year immersion test as shown in FIG.

Therefore, various means have been tried such that seawater does not enter the concrete, for example, a method of adding rubber latex or synthetic resin emulsion having excellent corrosion resistance to cement, hydrofluoric acid silicic acid on hardened concrete, There are a method of coating and permeating zinc silicofluoride or the like, a method of impregnating a high-molecular prepolymer and then polymerizing, and a method of coating hardened concrete with an inorganic material such as a mixture of sodium silicate.

(Problems to be Solved by the Invention) However, the conventional seawater-resistant treatment method requires a special polymer agent, requires complicated steps, and is disadvantageous in terms of cost.

By the way, Portland cement is the most common cement in calcium silicate composition, but Portland cement produces a large amount of Ca (OH) ₂ during hydration and hardening, and when this reacts with seawater components, cement water As a result of causing deterioration of the structure of the Japanese cured product, seawater permeates and the seawater resistance deteriorates.

Fine powder (ultrafine particle) SiO _{2 is} added to this Portland cement.
Was added and mixed, for example, chemical composition SiO ₂ : 44.1%, Al
₂ O ₃ : 8.8%, Fe ₂ O ₃ : 3.0%, CaO: 38.6%, MgO: 1.4%, Na ₂
A cement material with O: 0.4%, K ₂ O: 0.7%, ignition loss: 1.9% and a specific gravity of 2.66 is commercially available.

The cement material captures Ca (OH) ₂ with SiO ₂ by the following reaction scheme, because it is intended to stabilize, considered it is preferable to use the cement.

Ca (OH) ₂ + SiO ₂ → CxSyHz (however, C: CaO, S: SiO ₂ , H: H ₂ O) However, even if the present inventors have done this as a result of experiments, the Portlandite: Ca (O
H) ₂ remains, and as a result of an immersion test for 8 weeks for the extremely seawater (hot seawater) shown in FIG. 1 as a graph (b),
We have found that the seawater resistance is not satisfactory.

(Means for Solving Problems) As a result of the study in view of the above, the present inventor has found that seawater resistance which can significantly improve seawater resistance by firmly capturing calcium hydroxide generated and released in cement. Succeeded in providing cement material.

That is, the present invention is a method for producing the following seawater-resistant cement material and seawater-resistant mortar or concrete.

(1) A seawater-resistant cement material, characterized in that fine powder silicon dioxide and acidic aluminum phosphate are added to and mixed with Portland cement which is a calcium silicate type cement.

(2) The addition amount of acidic aluminum phosphate is 0.1 to 5 parts by weight with respect to 100 parts by weight of Portland cement which is a calcium silicate cement, (1)
The seawater-resistant cement material according to the item.

(3) 30 to 120 parts by weight of finely powdered silicon dioxide and 0.1 to 5 parts by weight of acidic aluminum phosphate are added to 100 parts by weight of Portland cement and mixed, and the above (1) or ( The seawater-resistant cement material according to the item 2).

(4) A method for producing seawater-resistant mortar or concrete, characterized in that fine powder silicon dioxide and acidic aluminum phosphate are added to and mixed with Portland cement which is a calcium silicate type cement.

(5) The addition amount of acidic aluminum phosphate is 0.1 to 5 parts by weight based on 100 parts by weight of Portland cement which is a calcium silicate cement (4)
A method for producing a seawater-resistant mortar or concrete according to the item.

(6) 30 to 120 parts by weight of finely divided silicon dioxide and 0.1 to 5 parts by weight of acidic aluminum phosphate are added and mixed with 100 parts by weight of Portland cement, and the mixture is added to the above (4) or (5). A method for producing a seawater-resistant mortar or concrete according to the item.

Portland cement, which is a calcium silicate type cement, is a commonly used cement and is easily available at a low price, but as described above, calcium silicate has the following reactions during hydration when producing mortar or concrete. Generate a large amount of Ca (OH) ₂ .

2C ₃ S ＋ 6H ₂ O → C ₃ S ₂ H ₃ ＋ 3Ca (OH) ₂ 2C ₂ S ＋ 4H ₂ O → C ₃ S ₂ H ₃ ＋ Ca (OH) ₂ And the portlandite produced as above is Mg in seawater. Ions and SO ₄ ions react with each other to form gypsum (CaSO ₄ ), which is C ₃ A in concrete (however, A
= Al ₂ O ₃ ) and reacts with ettringite (C ₃ A · 3CaSO ₄ ·
3H ₂ O) is generated and expanded, resulting in the destruction of mortar and concrete.

By the way, in calcium silicate cement with a large amount of ultrafine SiO ₂ added, a part of portlandite is captured as a stable compound by the reaction of Ca (OH) ₂ + SiO ₂ → CxSyHz, and CaO produces poisons. Is blocked to a large extent.

The amount of the ultrafine SiO ₂ added is preferably 30 to 120 parts by weight with respect to 100 parts by weight of calcium silicate cement.

However, even this way the tissue does not have sufficient resistance to seawater.

The present inventor, after repeated studies to improve this point, when adding acidic aluminum phosphate to calcium silicate-based cement and mixing, especially, with respect to 100 parts by weight of Portland cement of calcium silicate-based cement, 30-120 parts by weight of powdered silicon dioxide and 0.1% of acidic aluminum phosphate.
When ~ 5 parts by weight was added and mixed to prepare a hydraulic cement material, it was found that the hydrated cured product was a stable product excellent in seawater resistance.

Here, the acidic aluminum phosphate used in the present invention preferably contains aluminum and phosphorus in an atomic ratio (refers to a gram-atl ratio) of Al / P 1/3 to 2/3.

Various methods for producing acidic aluminum phosphate have been proposed, but industrially, aluminum hydroxide and phosphoric acid are mixed so as to have a predetermined Al / P ratio, and a high-viscosity liquid obtained by heating and dehydration is mixed with hot air. The method of spraying and drying is generally adopted.

The acidic aluminum phosphate used in the present invention is effectively used without being limited to its production method as long as it contains aluminum and phosphorus at an atomic ratio of Al / P 1/3 to 2/3. can do. Acidic aluminum phosphate obtained by spray-drying the reaction product of phosphoric acid and aluminum hydroxide as shown above generally has a very high hygroscopicity. It is necessary to use non-breathable packaging material such as bags, fibers or plastic drums.

For example, aluminum sesquiphosphate (AlH ₃ (PO ₄ ) / 3H ₂ O) proposed in JP-A No. 50-104799 has a low hygroscopic property, and a mixture with cement is stored for a long time in a normal cement packaging form. Since it is possible, it is a more preferable acidic aluminum phosphate for practical use.

Liquid acidic aluminum phosphate is widely used as a refractory binder and is readily available.When using this liquid acidic aluminum phosphate, when cement and water are mixed together, the cement and water should be used at the same time. Alternatively, after dissolving a predetermined amount of acidic aluminum phosphate in water in advance or after mixing cement and water, a predetermined amount of acidic aluminum phosphate may be added and kneaded.

As a matter of course, powdery or solid acidic aluminum phosphate can be similarly added at the time of producing mortar and concrete.

It is speculated that this is due to the progress of the following reaction and the action of the sparingly water-soluble calcium phosphate produced.

According to the present invention, residual acidic Ca (OH) ₂ is completely and stably captured by the added acidic aluminum phosphate, and chemically stable Ca ₃ (PO ₄ ) ₂ is generated in seawater. As a result, the inventive cement material has excellent seawater resistance.

As the cement used in the present invention, since the material is easily available, it is possible to add fine powder Si to conventional Portland cement.
It is preferable to add a large amount of O ₂ .

The addition amount of acidic aluminum phosphate is preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of cement. If the addition amount is less than 0.1 parts by weight, the effect is not sufficiently observed, and if the addition amount is more than 5 parts by weight, the viscosity of the cement slurry during hydration is high, and the workability is deteriorated in the generally used construction method, and it is practical. Not.

Further, the seawater-resistant cement material of the present invention, water by a conventional method,
When mortar or concrete is prepared by adding an admixture, calcium phosphate produced by the chemical reaction as described above is a fine crystalline particle, and the fine crystalline particle is filled in the mortar and the concrete structure pores and sealed. As a result, mortar and concrete have a low porosity and are excellent in seawater resistance with no permeability to seawater.

And, as described above, the porosity is low, mortar having no seawater permeability, and if the seawater-resistant cement material of the present invention is used to obtain concrete, the permeated water freezes and expands in a low temperature environment, mortar and concrete. It does not destroy the structure, and therefore the spalling resistance is extremely superior to the conventional cement materials.

(Example) calcium silicate based cement (added ultrafine SiO ₂ 40 to 50 wt% containing Portland cement) per 100 parts by weight,
Acid aluminum phosphate 0.5 parts by weight, fine seconds 40 parts by weight, water 5
After adding 0 parts by weight and mixing, the mixture was cured and cured to obtain a hardened cement product.

When this cement hardened product was subjected to an immersion test in seawater (hot seawater) for 8 weeks, as shown in FIG. 1, the cement hardened product (a) of the cement material of the present invention was It can be seen that the change in length is smaller than that of the products (c), (d), etc., and the seawater resistance is excellent. As for the residual strength ratio (%), as shown in FIG. 2, the example of the present invention shows the graph shown as (a) in FIG. It can be seen that high strength is preserved over the entire period.

(Effects of the Invention) As described above, the cement material of the present invention captures residual Ca (OH) ₂ completely and stably by the action of the added acidic aluminum phosphate when the cement is hydrated and hardened. At the same time, Ca ₃ (P
Since O ₄ ) ₂ is produced, the cement material of the present invention has excellent seawater resistance as a result.

Further, the seawater-resistant cement material of the present invention, water by a conventional method,
When mortar or concrete is prepared by adding an admixture or the like, calcium phosphate produced by the chemical reaction as described above is a fine crystalline particle, and the fine crystalline particle is evenly and densely filled in the mortar and concrete structure pores. As a result, the permeability to seawater is extremely low.

Therefore, even in a low temperature environment, the permeated water does not freeze and expand, and is not subject to the freeze-thaw action that destroys the mortar and concrete structures, and therefore the spalling resistance is much higher than when using conventional cement materials. It will be excellent.

In addition, since the generated calcium phosphate has a high hardness, the mortar and the concrete structure have excellent wear resistance, and the structure that comes into contact with ice, ice and sand, particularly the polar marine structure. It can be used advantageously.

Furthermore, since aluminum phosphate acts as a hardening accelerator, the strength development time after placing a mortar or uncured concrete is significantly shortened.

Therefore, the concrete obtained by using the seawater-resistant cement material of the present invention is constructed in a harbor, a shore, an ocean, and subjected to the action of seawater, for example, an offshore platform,
Even when applied to not only seawall structures, marine concrete structures such as fish reefs, but also structures on land that are affected by waves and salt winds, they are not susceptible to deterioration.

[Brief description of drawings]

FIG. 1 is a graph showing changes in expansion coefficient due to immersion in seawater of a cured product obtained by using a seawater-resistant cement material of an example of the present invention and a cured product obtained by using another conventional cement material. FIG. 2 is a graph showing changes in the residual strength ratio in a 10-year seawater immersion test of hardened materials using various cements. (A): Cured product using the cement material of the present invention (b): Cured product using fine powder SiO ₂ added Portland cement (c): Cured product using sulfate-containing Portland cement (d): Using normal Portland cement Cured product of NP: Normal cured product of Portland cement FP: Cured product of B type fly ash cement SP: Cured product of B type blast furnace cement PP: Cured product of A type silica cement

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI technical display location // C04B 111: 24 (72) Inventor Minoru Sawade 2-16-1 Kyobashi, Chuo-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Takuro Odawara, 2-16-1, Kyobashi, Chuo-ku, Tokyo Shimizu Construction Co., Ltd. (72) Inventor Kouji Nakajima 4-12-2 Miyamae, Suginami-ku, Tokyo (72) ) Innovator Shinji Iino 3-4-22, Hikoshimasako-cho, Shimonoseki-shi, Yamaguchi Prefecture (72) Inventor Yukio Takahashi 6 799, Kuno, Shimonoseki-shi, Yamaguchi Prefecture (72) Minor Oshima 6 Hikoshimasako-cho, Shimonoseki-shi, Yamaguchi Prefecture 2-45 (56) References JP-A-48-47528 (JP, A) JP-A-59-21558 (JP, A)

Claims (6)

[Claims] 1. A seawater-resistant cement material comprising a Portland cement, which is a calcium silicate-based cement, to which fine powder silicon dioxide and acidic aluminum phosphate are added and mixed. 2. The seawater resistant composition according to claim 1, wherein the amount of the acidic aluminum phosphate added is 0.1 to 5 parts by weight with respect to 100 parts by weight of Portland cement which is a calcium silicate cement. Cement material. 3. To 100 parts by weight of Portland cement,
30-120 parts by weight of finely powdered silicon dioxide and 0.1-5 parts by weight of acidic aluminum phosphate are added and mixed, and the seawater-resistant cement according to claim 1 or 2. Material. 4. A method for producing seawater-resistant mortar or concrete, characterized in that fine powder silicon dioxide and acidic aluminum phosphate are added to and mixed with Portland cement which is a calcium silicate cement. 5. The resistance according to claim 4, wherein the amount of acidic aluminum phosphate added is 0.1 to 5 parts by weight with respect to 100 parts by weight of Portland cement of calcium silicate cement. Method for producing seawater mortar or concrete. 6. For 100 parts by weight of Portland cement,
30 to 120 parts by weight of finely powdered silicon dioxide and 0.1 to 5 parts by weight of acidic aluminum phosphate are added and mixed, and the seawater-resistant mortar or concrete according to claim 4 or 5. Manufacturing method.