KR920003022B1 - Preparation method of conerete product - Google Patents

Abstract

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Description

Manufacturing method of concrete molding

The present invention relates to aggregates, admixtures, water, retardants, glass fibers, etc., in cement blended with Portland cement clinker, clinker composed mainly of calcium sulfo aluminate (3CaO · 3Al ₂ O ₃ · CaSO ₄ ), gypsum, and blast furnace chain slugs. The present invention relates to a method for producing a concrete molded article, which is added by a common method to produce a concrete molded article, which is cured for at least 4 hours in a range of 15 ° C to 65 ° C. The present invention provides a concrete molded article such as GRC that does not deteriorate, bending does not decrease impact strength, decorative blocks that do not cause efflorescence and loses aesthetic appearance, or segments that do not erode by acids or sulfates.

When manufacturing concrete molded products, Portland cement, which is composed mainly of calcium silicate such as tricalcium silicate (3CaOSiO ₂ ) and silicate lime (2CaOSiO ₂ ), is kneaded with water and cured to harden. In the process, it is known that calcium hydroxide <Ca (OH) ₂ > is mainly composed of calcium silicate hydrate (CSH) which is a main product.

For example, silicate 3 lime (3CaO · SiO ₂₎ 50% by weight of silicate 2 Lime (2CaO · SiO ₂₎ 25% by weight containing ordinary Portland cement of calcium hydroxide with respect to the original cement 100 parts by weight in the <Ca (OH to ) ₂ > on the stoichiometry of 30 parts by weight.

Therefore, the pH of normal hardened cement or concrete is increased to about 12.8 to 13.2, which causes cement and concrete to maintain strong alkalinity.

Therefore, in composite GRC (glass fiber reinforced concrete) made of alkali glass fiber and Portland cement, the glass fiber is eroded by a high alkali atmosphere of calcium hydroxide <Ca (OH) ₂ > produced from cement over a long period of time, and the tensile strength of GRC It is generally known that excessive bending strength performance and impact resistance deteriorate.

In addition, as color cement products or color concrete products colored with pigments, Ca (OH) _{2 produced} from cement precipitates on the rear surface by moving the void velocity from the inside of the cement hardened body or concrete, or reacts with CO ₂ in the air at the rear surface. Therefore, since it becomes CaCO ₃ and precipitates, so-called wind sea occurs and aesthetic appearance is often damaged.

In addition, various acid, sulfates in seawater or hot spring water, and Ca (OH) ₂ produced from cement react with each other to erode the hardened concrete or concrete and cause sulfate expansion.

Thus, lowering the alkalinity by preventing the production of calcium hydroxide <Ca (OH) ₂ > in cement is extremely difficult since the production of Ca (OH) ₂ is an intrinsic shape of the hydration reaction of Portland cement, and conventionally, for example, Ca (OH) ) ₂ and the reaction easy to active silica and active alumina to a material added to the calcium silicate hydrate (CaO-SiO ₂ -H ₂ O system containing a) and calcium aluminate hydrate (based _{CaO-Al 2 O 3 -H 2} O) As a method of fixing with an insoluble hydrate, there have been attempts, but the formation of Ca (OH) ₂ has not yet been sufficiently prevented.

The present invention uses a special cement that does not produce Ca (OH) ₂ , to solve the expansion crack often occurs when producing so-called glass fiber reinforced concrete, color concrete, concrete subjected to the action of acid or sea water, etc. It was made for.

Next, the reason why this special cement exhibits physical properties equivalent to that of Portland cement without generating Ca (OH) ₂ will be described.

Calcium sulfo aluminate 3CaO.3Al ₂ O ₃ .CaSO ₄ reacts with calcium hydroxide and gypsum upon hydration to form an ethrin guide, as shown in the following equation.

_{3CaO · 3Al 2 O 3 · CaSO} 4 ( calcium sulfo aluminate) + 3CaSO ₄ (gypsum) + 6Ca (OH) ₂ (calcium _{hydroxide) + 90H 2 O → 3 (} 3CaO · Al 2 O 3 · 3CaSO 4 · 32H 2 O (Etrin guide)

By this reaction there is a anhydrite and calcium hydroxide to be consumed, calcium hydroxide <Ca (OH) _2> as, calcium hydroxide produced by the hydration of Portland cement clinker <Ca (OH) _2> is supplied.

Calcium <Ca (OH) _2> is not to be generated, Portland disposed of by the calcium <Ca (OH) _2> generated from the cement clinker, consuming all the calcium sulfo aluminate, calcium hydroxide <Ca (OH) in the system ₂ It is extremely important that> does not exist. This reaction is shown in the following scheme. Here, calcium sulfo aluminate clinker contains calcium sulfo aluminate as a main compound.

I.e. silicate 3 lime in the Portland cement clinker (3CaO · SiO ₂₎ and the silicic acid 2 Lime (2CaO · SiO ₂₎ is a calcium hydroxide Ca (OH) ₂ to the sign language hayeoseo generated, calcium sulfo aluminate _{(3CaO · 3Al 2 O 3 ·} CaSO _4), to react with gypsum (3CaSO _4), when the composition is to generate a lean eth- guide.

[Calcium Sulfo Aluminate Clinky]

Therefore, typical cements in the present invention are composed of Portland cement clinker as a source of Ca (OH) ₂ , calcium sulfo aluminate clinker mainly composed of calcium sulfo aluminate, anhydrous gypsum and blast furnace chain slug.

Portland cement clinker is used to secure durability after curing to produce CSH. The blending amount of Portland cement clinker is 20% by weight or more, and 70% by weight or less to avoid excessive generation of Ca (OH) ₂ . do. As the Portland cement clinker, portland cement clinker, medium heat portland cement clinker, high strength steel portland cement clinker, white portland cement clinker, sulfate resistant portland cement clinker, etc. can be used. Gypsum can be used to mix portland cement and mixed cement with portland cement added with silica and blast furnace slug.

Calcium sulfo aluminate clinker, the clinker in the applicant company and a product containing about 70% of the _{3CaO · 3Al 2 O 3 · CaSO} 4. The compounding amount of calcium sulfo aluminate clinker and anhydrous gypsum is 10% by weight or more because Ca (OH) ₂ is allowed to react without exception, but in order to prevent the durability of deterioration due to the formation of a large amount of ethrin guides, It is 40 weight% or less. In addition to calcium sulfo aluminate, calcium aluminates such as CaO · Al ₂ O ₃ , 12CaO · 7Al ₂ O _2, and the like also react with Ca (OH) ₂ and gypsum to form an ethrin guide. However, since 3CaO · Al ₂ O ₃ is the same calcium aluminate but does not react with Ca (OH) ₂ , calcium aluminate having a CaO / Al ₂ O ₃ molar ratio such as 3CaO · Al ₂ O ₃ greater than 3 cannot be used.

Thus, instead of a calcium sulfo aluminate clinker, it is possible to use an alumina cement containing _{CaO · Al 2 O 3, 12CaO} · 7Al 2 O 3.

As gypsum, dihydrate gypsum CaSO ₄ 2H ₂ O can be used instead of anhydrous gypsum CaSO ₄ .

The blast furnace slag is mainly composed of CaO · SiO ₂ and Al ₂ O ₃ , and reacts with calcium hydroxide <Ca (OH) ₂ > and gypsum CaSO ₄ in the system to produce CSH or ethrin guide. As shown in FIG. _2, calcium hydroxide <Ca (OH) ₂ > is trapped.

In order to exert the effect of the blast furnace chain slug, more than 20% by weight of the blast furnace slug should be blended. The compounding quantity is 60 weight% or less.

Instead of the blast furnace chain slug, ash which reacts with Ca (OH) _{2 in the} system can be used, which is mainly composed of SiO ₂ , Al ₂ O ₃ , CaO and the like.

Calcium hydroxide <Ca (OH) ₂ > produced during the hydration of cement finally contains CSH (equivalent to CaO ₂ SiO ₂ 3H ₂ O) and ethrin guide (3CaOAl ₂ O ₃ 3CaSO ₄ 32H ₂ O). It must be fixed as.

The molar ratio of CaO / SiO _{2 in} CSH = 1.5, the CaO / Al ₂ O ₃ molar ratio in ethrin guides = 3, and part of the lime powder (CaO) in cement forms gypsum (CaSO ₄ ), thus (3Al ₂ O ₃ In the case of + 1.5SiO ₂ ) / (CaO—SO ₃ ) molar ratio ≧ 1, there is no stoichiometric free calcium hydroxide <Ca (OH) ₂ > in the system.

On the other hand, if the molar ratio exceeds 1.5, the original function of the cement is lost, resulting in poor hardening and strength development. Therefore, the molar ratio of (3Al ₂ O ₃ + 1.5SiO ₂ ) / (CaO-SO ₃ ) is preferably 1.0 or more and 1.5 or less.

The special cement described above has an extremely interesting characteristic of not containing Ca (OH) ₂ in the cured body. Therefore, when used for glass fiber reinforced concrete GRC, since glass fiber does not receive alkali erosion over a long term, the fall of strength and an impact value can be prevented. When used for color concrete, it is possible to prevent wind damage due to Ca (OH) ₂ or CaCO ₃ and to improve the corrosion resistance of concrete to various acids and seawater.

However, this special cement has one major drawback when used in concrete. Portland cement clinker and the clinker whose main ingredient is calcium sulfo aluminate are all hydraulic, so that when both break the balance of hydration, good curing is not expected. At low temperatures, i.e., below 15 ° C, in particular below 10 ° C, the hydration of the Portland cement clinker is somewhat delayed, whereas the hydration of calcium sulfo aluminate rarely proceeds, and therefore, at low temperatures to normal temperatures, above 15 ° C. When is changed, the hydrate of calcium sulfo aluminate proceeds in the state of hardening by the hydration of C ₃ S, C ₃ S of the Portland cement clinker, the tensile stress occurs in the hardened body, the hardened body causes expansion crack Is the point.

The present inventors have examined the method of solving this expansion crack and found that it is an effective method to maintain the temperature at 15 ° C. or higher by curing steam at low temperatures.

That is, it maintains at 15 degreeC or more. When the curing temperature is maintained above 15 ° C., the hydration reaction of Portland cement and the hydration reaction of calcium sulfo aluminate clinker proceed simultaneously, so that the expansion force generated when the ethrin guide is produced by the hydration of calcium sulfo aluminate is It is absorbed by natural concrete, which has not yet hardened sufficiently, so that concrete does not cause expansion cracks. By curing at a temperature of 15 ° C. or higher for 4 hours, unreacted calcium sulfo aluminate and gypsum are reduced, so that expansion force that is already cracked after curing cannot be generated. The accelerated curing temperature is preferably 65 ° C. or lower as in the case of ordinary concrete products.

The curing method in the present invention is not intended to accelerate the appearance of strength as in the case of ordinary concrete and to speed up the mold. In a normal concrete product, there is no problem if the curing period is extended even at a low temperature, but in the concrete of the present invention, even if the curing period is extended at a low temperature, the tendency of cracking in the concrete cannot be reduced.

Generally, in concrete products using ordinary white cement or ordinary portland cement, there is a problem in that wind seas are generated by mid-term curing. The special cement used in the present invention is characterized in that no wind damage occurs even in the middle stage of curing. Therefore, by using the special cement of the present invention to steam curing, a concrete product which does not generate wind damage can be obtained.

Although this special cement tends to be slightly faster in condensation, the setting time of cement can be delayed by appropriate addition of oxycarboxylic acid or salt thereof such as sodium citrate and citric acid.

The speed of the uptime, the temperature increase, or the temperature decrease in accelerated curing may be the same as in the case of ordinary concrete products.

Example 1

Usually 25% by weight of Portland cement clinker, 15% by weight of calcium sulfo aluminate clinker, 15% by weight of anhydrous gypsum and 45% by weight of blast furnace chain slug were mixed and ground to obtain cement for use in the present invention. The molar ratio of (3Al ₂ O ₃ + 1.5SiO ₂ ) / (CaO-SO ₃ ) in cement was 1.31.

To the cement of the present invention, a silica sand, a water reducing agent, Fahwang Mighty (manufactured by Nippon Kogyo Co., Ltd.), sodium citrate, water, and alkali glass fibers were added to secure the molding time, and then kneaded until homogeneous with a mixer to obtain GRC. . The mixing | blending of GRC was S / C = 1.0, W / C = 0.40, the water reducing agent C * 1%, sodium citrate C * 0.4%, and GF C * 5%. After molding into a mold of 200 cm in length × 100 cm in width × 1 cm in depth, the surface was pressurized, followed by medium temperature curing for 3 hours at elevated temperature, 30 ° C. × 6 hours in fat and oil, and natural cooling to obtain a glass fiber reinforced concrete sheet. As the fertilizer, a glass fiber reinforced concrete plate obtained by curing at room temperature without steam curing was used.

And the minimum of the room temperature in 1 day from shaping | molding to completion | finish of steam curing was 1 degreeC, and the highest was 17 degreeC.

Each GRC plate is left at room temperature for up to 3 days after molding, after which it is demolded and exposed to the outdoors vertically.

Three months after the exposure, the state of the plate was determined. The results are shown in the first table.

TABLE 1

The non-vapor-cured GRC plates rarely reacted with calcium sulfo aluminate clinkers at three days after molding, although they exhibited sufficient curing strength by hydration of the Portland cement clinker. Therefore, after exposure to the outdoors, unhydrated calcium sulfo aluminate gradually reacted with an increase in air temperature and rainfall to produce and expand an ethrin guide, causing cracks in the GRC plate.

Example 2

In this example, two types of cement shown in Table 2 were used.

TABLE 2

Pigment red iron oxide, citric acid, silica sand, and water for delaying condensation were added to the cements A and B shown in the second table, respectively, and kneaded with a mixer to obtain two kinds of color mortar. As for the mixing | blending of color mortar, S / C = 1.0, W / C = 0.34, the pigment addition amount Cx5%, and the citric acid addition amount were Cx0.2% in cement A and Cx0.5% in cement B.

By vibrating pressure, these color mortars were molded to a thickness of 10 mm on a base layer of porous concrete (usually 100 mm x 200 mm x 40 mm) using portland cement 5-10 mm discontinuous particle size. Immediately after demolding, steam-cured and colored water-permeable decorative blocks (dimensions 100 × 200 × 50 mm) were obtained by natural cooling for 3 hours at elevated temperature, 50 ° C. × 8 hours, 6 hours or 4 hours. As a comparison, a decorative block was maintained as it was at 5 ° C. after molding without steam curing. And kneading and shaping | molding were all performed in the 5 degreeC constant temperature room, and the block which finished steam curing was returned to the 5 degreeC constant temperature stall, and was left still.

Each decorative block was taken out in a 5 degreeC constant temperature room after 3 days of shaping | molding, and immersed in 20 degreeC water. The state of the block was observed 10 days after the molding. The results are shown in Table 3.

TABLE 3

Neither block had any abnormality in the base concrete. Steam curing of Nos. 1 to 3 and Nos. 5 to 7 was cured by 50 ° C. × 4.6 or 8 hours in accordance with the present invention, and no cracking occurred in underwater immersion. As for No. 4 and No. 8, a crack generate | occur | produced and all fell as a comparison. Samples were taken from each block after 3 days of molding, and measured by powder X-ray diffraction. As a result, in Nos. 1 to 3 and 5 to No. 7, calcium sulfo aluminate 3CaO.3Al ₂ O _3. CaSO ₄ and gypsum were hardly fixed, but unreacted 3CaO · 3Al ₂ O ₃ · CaSO ₄ , CaSO _4, or CaSO ₄ · 2H ₂ O was detected in Nos. 4 and 8.

Claims (1)

Silicate 3 lime (3CaO · SiO _2), silicates 2 Lime (2CaO · SiO ₂₎ port LAN de cement clinker from 20 to 70% by weight, calcium sulfo aluminate as a main component of calcium silicate, such as 3CaO · 3Al ₂ O ₃ · CaSO _{As a composition of} 10 to 40% by weight of clinker ₄ as a main component, 10 to 40% by weight of anhydrous gypsum or dihydrate gypsum, blast furnace chain slug or ash content and (3Al ₂ O ₃ + 1.5SiO ₂ ) / (CaO-SO ₃ ) Aggregate, admixture, water, retardant in cement with a molar ratio of 1.0 to 1.5. Method for producing a concrete molded article characterized in that the glass fiber or the like is appropriately added by a common method to make a concrete molded article, which is cured at least 4 hours at a temperature in the range of 15 ℃ to 65 ℃.