JP3020962B2 - Highly durable cement composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a highly durable cement composition, and more specifically, to reduce or prevent alkali-aggregate reaction of mortar and concrete, and to improve durability such as salt resistance and sulfate resistance. The present invention relates to a highly durable cement composition capable of improving the durability.

<Conventional technology and its problems> In recent years, the amount of alkali in cement has increased due to the depletion of high-quality cement raw materials, changes in the firing method of cement, and the change to pulverized coal for firing fuel, etc. There has been a problem that an alkali-aggregate reaction occurs in combination with the deterioration in quality.

Also, the durability of mortar and concrete, such as salt resistance and sulfate resistance, has begun to be emphasized as ocean development progresses.However, simply reducing the water / cement ratio and increasing the strength will not significantly improve the durability. There was a problem that it was not recognized.

The use of blast-furnace slag cement has been recommended as a method of solving these problems at once.

Although the reason why blast furnace slag cement reduces or prevents the alkali-aggregate reaction is not clear, it has been recognized in the laboratory that it has a preventive effect. As for the durability such as salt resistance and sulfate resistance, the Al component in the blast furnace slag chemically absorbs the infiltrating chlorine ions and sulfate ions, and the Friedel salt (3CaO.Al ₂ O ₃ .CaCl ₂・ 10H ₂ O) and ettringite (3
It is fixed in the form of CaO ・ Al ₂ O ₃・ 3CaSO ₄・ 32H ₂ O) and utilizes the property of preventing further penetration.

The amount of blast furnace slag used is 4 parts by weight based on the total of 100 parts by weight of cement and blast furnace slag, even when suppressing alkali reaction or improving salt resistance and sulfate resistance.
0 parts by weight or more is recommended. Conventionally, the slag mixing ratio of blast furnace slag B type cement is generally 30 to 35% by weight,
Recently, it has been raised to 40-55% by weight.

In addition, the fineness (Brain value) of slag used in blast furnace slag cement is as coarse as about 4,000 cm ² / g, but recently, it has become more difficult to use high strength and, for example, salt resistance and alkali-aggregate reaction prevention. Fineness of 10,000 for high durability
It has been proposed to use an ultrafine slag having a particle size of about 00 cm ² / g and a maximum particle size of about 10 μm (Japanese Patent Laid-Open No. 281057/1986).

However, if the blast furnace slag is produced as a by-product from the reducing atmosphere, when each component is chemically analyzed and converted as an oxide, it is considered that there is a considerable weight increase in total and oxygen deficiency. When such blast furnace slag undergoes a hydration reaction with cement or slaked lime, a large amount of
Almost no calcium aluminate hydrate is detected by X-ray diffraction despite the presence of the Al component. However, when chlorine ions or sulfate ions penetrate there, it quickly generates Friedel salts and ettringite to stop the penetration, but easily adsorbs carbon dioxide and oxygen, causing the cured product to become neutralized or oxidized. It is easy to cause deterioration and rust of the reinforcing steel,
When considered comprehensively, there remains a problem in long-term durability.

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems. As a result of using the amorphous aluminum hydroxide, the amorphous aluminum hydroxide reacts under normal temperature or normal pressure steam curing conditions to reduce or prevent the alkali-aggregate reaction. The present invention has been completed by obtaining knowledge that can improve durability such as salt resistance and sulfate resistance.

<Means for Solving the Problems> That is, the present invention provides (1) 2 to 20 parts by weight of amorphous aluminum hydroxide and 0.2 to 2 parts by weight of a high-performance water reducing agent per 100 parts by weight of cement. A highly durable cement composition according to (1), further comprising a highly durable cement composition for reducing alkali-aggregate reaction, salt resistance and sulfate resistance, and (2) further comprising an expanding material.

 Hereinafter, the present invention will be described in detail.

Examples of the amorphous aluminum hydroxide used in the present invention include aluminum sludge discharged during processing of aluminum and intermediates during the production of alumina gel and the like.

Amorphous aluminum hydroxide is usually in the form of a wet cake or sol containing a large amount of water, and when it is added, it may be added as a slurry by adding a little water, or in the form of a slurry. It is more economical and preferable to add the product by wet grinding than to dry it.

The greater the amount of amorphous aluminum hydroxide used, the greater the effect of its use. However, if it exceeds 5 parts by weight with respect to 100 parts by weight of cement in concrete, crystalline calcium aluminate will be used. 2 to 20 parts by weight is particularly preferable because the strength gradually decreases, probably because the amount of hydrate increases.

The cement used in the high-durability cement composition of the present invention is a mixed cement of fly ash cement and silica cement, in addition to various portland cements such as ordinary / early high / super early / moderate heat / white.

In the production of mortar or concrete, various commercially available water reducing agents, AE agents, retarders, accelerators, expanders and the like which are usually used can be used in combination. In particular, it is preferable to use a high-performance water reducing agent in combination.
It promotes reduction or prevention of alkali-aggregate reaction and improvement of durability such as salt resistance and sulfate resistance.

High-performance water reducing agents are surfactants with a large dispersing ability that do not accompany excessive delay in coagulation or excessive air entrainment even when added in large amounts, and include salts of naphthalenesulfonic acid formaldehyde condensate and melaminesulfonic acid formaldehyde. Examples thereof include salts of condensates, high molecular weight lignin sulfonates and polycarboxylates as main components. Specifically, for example, Kao Corporation's trade name “Mighty 150”; FT-500, Bozoris Bussan Co., Ltd.
Product name "NL-4000" and the like.

The amount of high-performance water reducing agent used is 100 cement
0.2 to 2 parts by weight based on parts by weight.

In addition, in mortar and concrete using an expanding material, the amount of micropores increases by expanding,
It is particularly preferable to use the cement admixture of the present invention in combination, since chloride ions and sulfate ions can easily penetrate.

The expanding material is Denka CSA (trade name, manufactured by Denki Kagaku Kogyo Co., Ltd.)
# 20 ”and other ettringites and Onoda Cement Co., Ltd.
It is roughly divided into lime-based products such as the product name “Onoda Expan”.

The method for adding the highly durable cement composition of the present invention is not particularly limited. When kneading mortar or concrete, knead with amorphous aluminum hydroxide or a high-performance water reducing agent, which is charged as powder. Any method such as dispersing in water and mixing in advance with the cement can be used, and a method of dispersing and mixing in kneading water is preferable.

<Example> Hereinafter, the present invention will be described with reference to examples.

Example 1 Using a mortar composition of 800 parts by weight of cement, 1,600 parts by weight of sand, 8 parts by weight of a water reducing agent and 320 parts by weight of water, aluminum sludge was mixed with the same weight of water as amorphous aluminum hydroxide, Wet pulverization was performed with a pot mill made of aluminum, calculated as a solid content of amorphous aluminum hydroxide of 7.25% by weight, and added to the cement in a slurry form by changing the addition amount to 100 parts by weight of cement, kneading the mortar, and mixing 4 × 4 A specimen of × 16 cm was formed. Then, after about 5 hours from the molding, capping was performed, the temperature was raised to 65 ° C. at a rate of 15 ° C./hr, and the temperature was maintained for 4 hours, and the steam valve was stopped to allow natural cooling in a steam curing tank. The next day, it was demolded and immersed in a 3% NaCl aqueous solution to determine the amount of chlorine permeated for each material age. The results are shown in Table 1.

For the determination of chlorine, 4 × 4 ×
One cm was cut out, dried at 300 ° C., and the whole was finely pulverized and subjected to X-ray fluorescence analysis. In addition, the compressive strength of one day of material age was also measured for reference. <Material> Cement: Ordinary Portland cement manufactured by Denki Kagaku Kogyo Co., Ltd. Sand: Natural sand, Himekawa river sand from Niigata Prefecture Water reducer: Electrochemical industry Product name "DENKA"
FT-500 ”Water: Drinking water Amorphous aluminum hydroxide: Aluminum sludge, 85% by weight of volatile liquid, 5% by weight of non-volatile liquid, 9.5% by weight of Al ₂ O ₃ 14.5% by weight of Al (OH) ₃ .

The amount of aluminum hydroxide added is 100 parts by weight of cement. As is clear from Table 1, the addition of amorphous aluminum hydroxide has the effect of suppressing the penetration of chloride ions. It can be seen that the effect becomes significant as the amount is increased.

Example 2 The mortar of 1 day old prepared in Experiment Nos. 1-1 to 1-9 was pulverized with a brown crusher, immersed under a 250 μ sieve in 50 g, 3% NaSO ₄ aqueous solution 1 for 72 hours, and filtered.
After repeated washing with water, the mixture was dried at 200 ° C., finely ground, and the amount of adsorbed sulfate ions was determined by X-ray fluorescence analysis. The sulfate ion in the cement was obtained by obtaining a blank in a sample 250 μm below before immersion, and subtracting that amount. Table 2 shows the results.

As is apparent from Table 2, as the amount of amorphous aluminum hydroxide added increases, the amount of sulfate ion adsorbed increases, indicating that there is an action of blocking the permeating sulfate ion. , Suggests sulfate resistance.

Example 3 Using sand and silica having the particle sizes shown in Table 3, cement 800
Parts by weight, 1,800 parts by weight of sand and silica and 1N NaOH aqueous solution 4
Alkali-aggregate reaction test was carried out using 00 parts by weight of mortar and changing the amount of aluminum sturdge added to cement in the same manner as in Example 1.

The test specimen is a 4 × 4 × 16 cm triple mold, and mortar is molded at both ends so that a gauge plug for length change measurement can be embedded, and cured for 24 hours in a room at 20 ° C ± 3 and RH 80% or more. And remove it from the mold.
Cured in a thermo-hygrostat at ℃ ± 2, RH95% or more, 3 months, 6 months
The amount of swelling of the lunar age was measured. The results are shown in Table-4.

As is clear from Table 4, the effect of suppressing the expansion is shown by using amorphous aluminum hydroxide, and the effect is more remarkable as the amount used is increased.

The aluminum sludge was added in parts by weight with respect to 100 parts by weight of cement, and was added to the mortar on an outer basis.

The silica used was opal silica from Iwo Jima, and NaOH used a special grade reagent.

Example 4 Each unit amount of cement, water, sand, crushed stone, and water reducing agent was respectively
Gmax is 15m at 480, 140, 813, 1,005 and 7.2 (kg / m ³ )
m, s / a is 45%, air volume is 2.0%, slump value is 8 ± 2cm, and concrete mix of aluminum sludge and expander is used as shown in Table-5. It was created.

In the same curing method as in Example 1, the specimen (curing 1) which had been demolded the next day was cured with room temperature at room temperature without steam curing until the next day, and then subjected to standard curing for 28 days in a mold ( Curing 2) was immersed in a 3% NaCl aqueous solution, taken out after 3 months of age, the central part of the test material was cut into Φ10 × 2 cm, and the permeation amount of chloride ions was determined in the same manner as in Example 1. . The results are shown in Table-5.

<Materials> Intumescent material: "Onoda Expan" (trade name, manufactured by Onoda Cement Co., Ltd.) The base length at the time of measurement of constrained expansion is measured using a uniaxially constrained steel rod before concrete molding with a dial gauge. As is clear from Table 5, when the intumescent material is used alone, the permeation amount of chlorine ions is not added. However, it can be seen that the use of amorphous aluminum hydroxide has a large effect of suppressing the penetration and does not affect the expansion amount of the expanding material.

<Effect of the Invention> By using the highly durable cement composition of the present invention, it is possible to reduce the alkali-aggregate reaction and produce mortar or concrete with improved durability such as salt resistance and sulfate resistance. Can be.

 ──────────────────────────────────────────────────の Continuing from the front page Judge, Katsutoshi Ishii Judge Yoshiaki Moritake Judge Naoto Noda (56) References JP-A-58-69759 (JP, A) JP-A-56-54265 (JP, A)

Claims (2)

(57) [Claims] (1) 100 parts by weight of cement, 2 to 20 parts by weight of amorphous aluminum hydroxide, and 0.
A highly durable cement composition containing 2 to 2 parts by weight for reducing alkali-aggregate reaction, salt resistance and sulfate resistance. 2. The highly durable cement composition according to claim 1, further comprising an expanding material.