JP2006036555A - Low outgassing mortar or concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To utilize lime stone aggregate or artificial lightweight aggregate which is not used alone as aggregate because of the deviation of particle distribution as aggregate for mortar or concrete in which the production of ammonia is prevented. <P>SOLUTION: The low outgassing mortar or concrete is produced by using lime stone in a quantity of ≥90 mass% of total aggregate component and blending and kneading it with a dispersant and thickening agent. Alternatively, the low outgassing mortar or concrete is produced by using artificial lightweight aggregate having no fracture surface on the surface in a quantity of ≥90 mass% of total aggregate component and blending and kneading it with the dispersant and the thickening agent. The low outgassing mortar or concrete can be also produced by using the lime stone and the artificial lightweight aggregate having no fracture surface on the surface in a quantity of ≥90 mass% of total aggregate component and blending and kneading it with the dispersant and the thickening agent. Instead of the thickening agent, inorganic powder having ≥1,500 cm<SP>2</SP>/g specific surface area can be also blended. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to mortar or concrete in which outgas such as ammonia generated from mortar or concrete is reduced. In the present specification, mortar or concrete may be simply referred to as concrete, and in this case, the term concrete means to include mortar.

  Ammonia generated from concrete is known to degrade artworks such as paintings and to reduce product yield in electronic device facilities. For this reason, it is required to use concrete with reduced ammonia generation in museums, museums, electronic device facilities, etc. In addition, the use of low-outgas concrete materials is recommended in various laboratories and special facilities. Yes.

  Ammonia, etc. generated from concrete is contained in cement-based kneaded materials in which the organic matter (nitrogen compounds) adhering to or contained in the concrete production materials (cement, aggregate, water, admixture, admixture, etc.) is highly alkaline. It is thought that it is denatured into ammonia, which is discharged out of the system along with the diffusion of water vapor. Therefore, in principle, if concrete is manufactured using a material that does not contain a gas generating substance such as a nitrogen compound, or a material that contains a trace amount, the outgas such as ammonia from the concrete can be suppressed.

From this viewpoint, a method for reducing the organic matter content in the cement (Patent Literature 1) and a method for reducing the organic matter content in the aggregate (Patent Literatures 2 and 3) have been proposed. In addition, a method of blending an ammonia decomposing agent, an absorbent, a carbonaceous additive and the like in a kneaded product (Patent Document 4 and Non-Patent Document 1) has been proposed.
JP 2001-2451 A, JP-A-10-287462, JP 2004-2099 A JP 2004-2070 A 22nd Air Cleaner and Contamination Control Competition, April 13-14, 2004, (C-17) Tanaka et al., Proceedings P257-259

  When reducing the organic matter in the cement by selecting the raw materials for cement production as in Patent Document 1, it is effective when using the cement, but when using ordinary general-purpose cement. The effect cannot be expected. A method using an ammonia decomposing agent or an absorbent can be expected to have a certain effect, but it requires special consideration in terms of work, cost and material properties in the production of concrete.

  Therefore, it is preferable to suppress the generation of ammonia by using ordinary general-purpose cement and without using special reagents such as decomposers and absorbents. It is most effective to avoid the entrainment of organic substances from the aggregate, which is the main factor. That is, it is advantageous to manufacture concrete using few aggregates even if it does not contain an organic substance like patent documents 2 and 3. However, in the case of Patent Document 2 that proposes the use of heat-treated aggregate, it requires equipment and heat energy for heat treatment of the aggregate. It has also been proposed to treat aggregates with hypochlorous acid, but again, equipment and reagents are required.

  In the patent document 3, the present inventors have proposed that crystallized stone material (stone material obtained by cooling and crystallizing molten slag originating from an incinerator and recrystallizing it) as an aggregate of concrete for clean space. Confirmed that ammonia gas generation can be significantly reduced. However, the production of crystal fossil materials is currently limited to one factory in Japan, and it has been found that it is difficult to stably supply this nationwide in terms of production system and cost. Therefore, an object of the present invention is to solve such a problem.

In order to solve the above-mentioned problems, the present inventors have used as an aggregate with a small amount of organic substances to replace the fossilized material.
(1) Limestone, which is said to have a low content of nitrogen compounds,
(2) We focused on artificial lightweight aggregates that have a history of sintering process.

  However, because of the uneven distribution of the particle size, it was found that it was not possible to produce concrete using only these as aggregates. However, even when using limestone or artificial lightweight aggregate with a biased particle size distribution, if a dispersant and a thickener, and in some cases, a dispersant and an inorganic powder are properly mixed and kneaded, there is no material separation and a good worker It became clear that a kneaded mixture of mortar or concrete having a good ability could be obtained, and that the cured product could be a good quality mortar or concrete having excellent strength characteristics and no generation of ammonia gas. It was also found that the thickener itself has the effect of suppressing ammonia generation.

  That is, according to the present invention, as mortar or concrete that solves the above problems, the blending amount of limestone is 90% by mass or more, preferably 95% by mass or more of the total aggregate components, and a dispersant and a thickener are blended. The blending amount of the kneaded low outgas mortar or concrete, or the artificial lightweight aggregate having no fracture surface on the surface is 90% by mass or more, preferably 95% by mass or more of the total aggregate component, and the dispersant and the thickener are used. Low-outgas mortar or concrete blended and kneaded, and further, the blending amount of limestone and artificial lightweight aggregate having no fracture surface on the surface is 90% by mass or more, preferably 95% by mass of the total aggregate component, and dispersant And a low outgas mortar or concrete kneaded with a thickener. Here, artificial lightweight aggregate with no fracture surface on the surface refers to artificial lightweight aggregate with a smooth surface, and does not have fracture surface on the surface that occurs when it is crushed or crushed. Say.

Furthermore, according to the present invention, there is provided a low-out mortar or concrete obtained by replacing the thickener with “inorganic powder having a specific surface area of 1500 cm ² / g or more” and kneading.

  As described above, if only limestone is used as aggregate, it is possible to avoid entrainment of nitrogen compounds through the aggregate into the concrete, but fine aggregate among limestone aggregates is generally coarser, and this is simply If the taste is aggregate, the quality equivalent to ordinary mortar and ordinary concrete cannot be obtained.

  Fig. 1 shows the particle size distribution of typical limestone crushed sand available on the market. As shown in Fig. 1, the particle size distribution of limestone crushed sand is within the upper and lower limits of the standard particle size curve defined in JIS A 5005. Although there is some, it is extremely biased toward the lower limit, and the overall grain size is coarse. Therefore, when using limestone crushed sand as an aggregate, it is necessary to use it by adjusting it to a grain size in the center of the standard grain size curve range by mixing with another aggregate of fine grain size. . In fact, the attempt was made to produce mortar or concrete by replacing the total amount of ordinary aggregate used in ordinary mortar or ordinary concrete with limestone obtained in the market. However, material separation occurred and workability was reduced. A fresh product that could be made was not obtained. This point is shown in the comparative example described later.

  Similarly, since artificial lightweight aggregates are manufactured through high-temperature firing, if only artificial lightweight aggregates are used as aggregates, it is possible to avoid entrainment of nitrogen compounds in the concrete via the aggregates. However, in this case as well, there is a bias in the particle size distribution, so it is not possible to obtain the same quality as ordinary concrete. FIG. 2 shows the particle size distribution of coal ash artificial aggregate, which is a calcined aggregate obtained by sintering coal ash and shale fine powder at a high temperature, as a representative example of artificial lightweight aggregate. As seen in Fig. 2, the particle size distribution of coal ash artificial aggregate is outside the upper and lower limits of the standard particle size curve defined in JIS A 5002. That is, there are no particles of 1.2 mm or less, and the coarse particle side is generally lower than the lower limit. Therefore, when this simple substance is used as aggregate, it cannot be kneaded like ordinary concrete, and it is impossible to obtain a concrete that has integrity. This point is also shown in the comparative example described later.

  In order to obtain particles on the fine particle side, for example, particles of 1.2 mm or less, it is conceivable to pulverize the artificial lightweight aggregate and mix the fine particles, but when pulverized, the crushing surface is exposed to the surface. , Nitrogen compounds contained in artificial lightweight aggregates (for example, nitrogen compounds contained in clay materials) are released from the crushing surface, which may promote ammonia generation. Therefore, the object of the present invention may not be achieved when an artificial lightweight aggregate whose particle size distribution is adjusted using a crushed or crushed artificial lightweight aggregate having a fractured surface is used. For this reason, when using an artificial lightweight aggregate, an artificial lightweight aggregate that does not substantially contain a crushed product or a crushed product, that is, a fractured surface is not used. However, in this case, since the particle size distribution is uneven, it is not possible to produce mortar or concrete having the same workability, strength characteristics, durability and economy as ordinary mortar or concrete.

According to the present invention, it has been found that this problem can be solved by the combined use of an appropriate dispersant and thickener. In other words, by blending an appropriate amount of an appropriate thickener together with a dispersant, a kneaded material with substantially no material separation can be obtained even when only limestone aggregate or artificial lightweight aggregate is used. The body can be excellent in strength properties and durability. The blending of the thickener also contributes to the suppression of ammonia gas generation. In addition, even if an inorganic powder having a specific surface area of 1500 m ² / g or more is used in place of the thickener, the same material separation resistance as that of the thickener can be obtained and a kneaded material without material separation can be obtained. it can.

The matters specified by the present invention will be described below.
The aggregate (fine aggregate or fine aggregate + coarse aggregate) used in the mortar or concrete of the present invention is limestone or / and artificial lightweight aggregate. As a result, it is possible to prevent the nitrogen component from being brought into the concrete from the aggregate component, and to reduce outgas such as ammonia generation from the concrete. Therefore, in the present invention, ideally, only limestone and / or artificial lightweight aggregate is used as an aggregate component (these are 100% by mass of the total aggregate component), but other than the limestone and / or artificial lightweight aggregate. If there is less than 10% by weight, and preferably less than 5% by weight, the amount of nitrogen compounds that cause the problem of ammonia generation is hardly accompanied, so other than limestone and / or artificial lightweight aggregate The amount of the aggregate component is acceptable if it is within the range of less than 10% by mass.

  Limestone aggregate is available on the market as fine aggregate and coarse aggregate as a crushed product. However, as described above, the particle size distribution is biased. In the present invention, it can be used as an aggregate without adjusting its particle size distribution. When adjusting the particle size distribution, it is preferable to adjust with a pulverized limestone aggregate. However, if the amount of adjustment is less than 10% by mass, preferably less than 5% by mass, ordinary sand can be used. The limestone aggregate used in the present invention only needs to have an absolute dry specific gravity of 2.5 or more and a water absorption of 3.0% or less.

  The artificial lightweight aggregate is a porous aggregate that is artificially manufactured through firing. Examples of artificial lightweight aggregate that can be obtained on the market include mesalite, asanolite, and super mesalite. Both are fired products at high temperatures. For this reason, artificial lightweight aggregates that do not have fracture surfaces on their surfaces are not accompanied by nitrogen compounds, but artificial lightweight aggregates that do not have fracture surfaces on their surfaces are based on their manufacturing history. Distribution is biased. For this reason, it is not possible to produce mortar or concrete with these artificial lightweight aggregates alone, and there are also implementation examples in which the total amount of aggregate is covered only with artificial lightweight aggregates that do not have these fracture surfaces on the surface. Absent. If the particle size distribution is adjusted using a crushed or crushed artificial lightweight aggregate, only the artificial lightweight aggregate can be used. There is.

  In the present invention, an artificial lightweight aggregate having no fracture surface on its surface can be used without adjusting its particle size distribution. When adjusting the particle size distribution, it is preferable that the limestone aggregate is crushed, but if the adjustment amount is less than 10% by mass, preferably less than 5% by mass, ordinary sand or gravel is used. It can also be used. As a typical artificial lightweight aggregate that can be used in the present invention, there is a coal ash artificial aggregate obtained by firing coal ash and shale fine powder at a high temperature.

  In the mortar or concrete of the present invention, even if substantially the total amount of aggregate is covered with limestone aggregate and / or artificial lightweight aggregate, normal aggregate can be obtained by blending appropriate amounts of appropriate dispersant and thickener. It is characterized in that it is possible to achieve workability, strength characteristics, etc. equivalent to those when used. For this reason, the use of dispersants and thickeners is essential in the mortar or concrete of the present invention. However, the thickener can be replaced with inorganic powder.

  The dispersant that can be used in the present invention is a chemical admixture that improves the dispersibility in water of a powder such as cement, and is particularly applicable as a chemical admixture for mortar or concrete. Typical examples thereof include AE agents, water reducing agents, AE water reducing agents, and high performance water reducing agents specified in JIS A 6204. Examples of the AE water reducing agent include lignin sulfonic acid type, oxycarboxylic acid type and polyol type, and examples of the high performance AE water reducing agent include those of polycarboxylic acid type, naphthalene type and aminosulfonic acid. Further, high performance water reducing agents such as melamine type, naphthalene type, polycarboxylic acid type and the like can be mentioned. It is also desirable to use an AE aid as needed. The amount of the dispersant added depends on the type and amount of the aggregate used, but generally may be in the range of C × 0.05% to C × 5.0% as a percentage of the cement (C).

  Examples of the thickener that can be used in the present invention include water-soluble polymers and polysaccharide polymers that have a function of retaining water by dissolving in water and exhibiting a thickening effect of cement milk. Typical water-soluble polymers include cellulose ethers such as methyl cellulose and hydroxyethyl cellulose. As the polysaccharide polymer, biosaccharides produced by microbial fermentation, such as rumzan gum, succinoglucan, welan gum, detan gum and the like can be used. Such water-soluble polymers and polysaccharide polymers generally have a function of holding water in place until the kneaded cement or concrete is hardened. In other words, the thickener blends the function of capturing excess moisture in the kneaded material and preventing the movement of excess moisture. As a result, it suppresses the occurrence of bleeding over time and increases the material separation resistance. It also works effectively for suppression. Considering that the generation behavior of ammonia gas from the molded body obtained from the kneaded product is accompanied by the diffusion of water from the surface of the molded body, the presence of a thickener reduces the diffusion of water from the surface of the molded body. This is because generation of ammonia gas from the molded body is suppressed.

  The present inventors have investigated the generation behavior of ammonia gas when various aggregates and cements are used. The generation of ammonia gas when natural aggregates are used is a process in which the cement hardening reaction proceeds. It was found that the generation behavior was remarkable in the early stage of the curing reaction where a large amount of mixed water would be present. At the beginning of the curing reaction, it is expected that the generated ammonia will once dissolve in water and be released as ammonia gas when the water is consumed, but the actual behavior is not clear. It is considered that it takes half a year or two years for the concrete structure of the construction work to be trapped in the matrix in the form of ammonia gas or ions generated during the hardening process and to stop releasing. It is presumed that the generation of ammonia gas is suppressed because the movement of water is prevented as described above by changing the viscosity (water retention) of the water in the material by blending the thickener. .

When an inorganic powder having a specific surface area of 1500 cm ² / g or more is added in place of the thickener, it is possible to promote the thickening of cement milk and increase the adhesive strength with the aggregate. Examples of the inorganic powder include limestone powder, fly ash, silica fume, and blast furnace slag powder. Limestone powder is preferable. Any of these may be added in a relatively large amount because the accompanying nitrogen compound does not cause a problem. For example, it is preferable to mix in the range of 5 to 70% by mass of the cement component.

  The mortar or concrete of the present invention can further reduce outgassing by blending an ammonia decomposing agent, an ammonia adsorbing agent, a gas adsorbing substance and the like into the kneaded material. Examples of the ammonia decomposing agent / adsorbent include at least one selected from the group consisting of hypochlorite, phosphoric acid, boric acid, hydrogen peroxide, and ozone water. Examples of the gas adsorbing material include activated carbon and zeolite. It is also possible to use drug-added activated carbon carrying an ammonia decomposing agent / adsorbent.

  Ordinary Portland cement can be used as the cement for producing the mortar or concrete of the present invention. As described above, since the present invention uses limestone aggregate and / or artificial lightweight aggregate, the main route of nitrogen compound entrainment in the material is avoided, and the entrainment from the cement is allowed to some extent by the incorporation of the thickener. Because it is done. That is, even if a nitrogen compound is slightly accompanied by cement from the cement, the generation of ammonia gas can be suppressed as a result of preventing the movement of water by blending the thickener. Therefore, according to the present invention, it is possible to obtain mortar or concrete that generates little ammonia gas even if ordinary Portland cement is used, but early-strength Portland cement and high belite cement, which are considered to generate little ammonia gas, Furthermore, low heat Portland cement can be used.

Seven types of concrete prepared according to the concrete composition shown in Table 2 using the materials shown in Table 1, ie, ordinary concrete (denoted as N)
・ Concrete using crystallized fossil (denoted T)
・ Concrete using limestone (C)
・ Concrete using artificial lightweight aggregate (coal ash artificial aggregate) (J)
・ Concrete with activated carbon added (K1)
・ Concrete with chemical-added activated carbon (denoted as K2)
・ Concrete with thickener added to ordinary concrete (M)
Various tests were conducted.

[Fresh concrete test]
Fresh properties were measured according to the test items and test methods shown in Table 3. The target values for fresh concrete were slump 18 ± 2.5cm, air volume 4.5 ± 1.5%, concrete temperature 20 ° C. The test results are shown in Table 4. From the results in Table 4, the slump values of 9.5 cm and 17.0 cm are also shown in the concrete (C) using limestone as an aggregate and the concrete (J) using an artificial lightweight aggregate as an aggregate. This is due to the addition of dispersants and thickeners.

For the purpose of comparison, but except for not adding thickener tried the preparation of comparative Concrete limestone to the same formulation as the concrete has an aggregate (C) (referred to as C _0), slump in C ₀ Test However, the slump value could not be measured.

For comparison, an attempt was made to produce comparative concrete (denoted as J ₀ ) with the same composition as concrete (J) made of artificial lightweight aggregate except that no thickener was added. _{At 0} , the slump test did not result in an integrated object, and the slump value could not be measured. That is, it was impossible to obtain concrete that could be carried out in both C ₀ and J ₀ .

[Measurement of ammonia generation amount]
A molded body (100 mm × 100 mm × 100 mm) was prepared from the above seven types of concrete, and ammonia generated from the test body was measured using the apparatus shown in FIG. Measurement conditions are 20 ° C. and 60% RH in a constant temperature and humidity chamber. Ammonia released from the concrete surface in the desiccator is 400 mL / min in a double gas absorption bottle containing 40 mL of ultrapure water. The sample was collected at a constant flow rate, sealed, and kept in a condition room at 20 ° C. and 60 RH until the test starting material age. The day when the sealed specimen was opened was defined as day 0, and the ammonia concentration in the collected liquid was determined at each time point on days 0, 1, 7, and 28. In order to promote the steady generation of ammonia, the ventilation was continued until the measurement end date even when the ammonia was not repaired. The ammonia concentration in the collected liquid was measured by analyzing the collected liquid by ion chromatography, and the amount of ammonia generated from the concrete surface (μg / (m ² · h)) was calculated from the analysis value. The results are shown in FIGS. 4 and 5 (cumulative generation amount of ammonia).

  FIG. 4 shows the change over time in the amount of ammonia generated, and the allowable line for the amount of ammonia generated is shown in the figure. From the results of FIG. 4, the amount of ammonia generated by the concretes of T, C, J, K1, K2 and M is lower than that of the concrete of N using ordinary aggregate, and the concrete using the limestone of C, In concrete using J's artificial lightweight aggregate, it falls below the tolerance line at the end of one day. In contrast, N concrete takes 28 days to fall below the tolerance line. Therefore, it can be seen that with C and J concretes, the withering period (a period of time for drying the concrete, usually half a year to one year after completion for the purpose of avoiding the adverse effects of ammonia) can be greatly shortened.

  Fig. 5 compares the cumulative amount of ammonia produced. As can be seen from the results in Fig. 5, the concrete produced by C and J has a cumulative amount produced more than the concrete using T crystallized aggregate. Low results were obtained. Further, in the M concrete in which the thickener is blended with the normal concrete, the cumulative amount of ammonia generated is lower than that of the N concrete without the thickener. This means that the thickener itself suppressed ammonia generation. This seems to be because the water retention function by the thickener played the role of suppressing ammonia release.

  As described above, according to the present invention, generation of ammonia gas from mortar or concrete material can be significantly reduced. For this reason, these materials can be used as materials that may come into contact with air in clean rooms such as semiconductor manufacturing, storage or exhibition rooms for artworks, biological or chemical laboratories, or other clean spaces. In addition, this mortar or concrete-based material has the same effect as ammonia mortar and concrete in that it suppresses ammonia generation without impairing the workability, strength characteristics, durability, and economic efficiency. It can be used in the same construction standards as general concrete as a structural material or finishing material for buildings with

It is a figure which shows the particle size distribution of limestone crushed sand. It is a figure which shows the particle size distribution of the artificial lightweight fine aggregate. It is an apparatus arrangement | positioning system diagram of the apparatus which measures the ammonia generation amount from a concrete test body. It is the figure which showed the time-dependent change of the ammonia generation amount of the 7 types of concrete tested. It is the figure which contrasted the cumulative generation amount of ammonia of 7 types of concrete tested.

Claims (6)

  Low outgas mortar or concrete in which the amount of limestone is 90% by mass or more of the total aggregate component, and kneaded with a dispersant and a thickener.   Low-outgas mortar or concrete in which the blending amount of artificial lightweight aggregate having no fracture surface on the surface is 90% by mass or more of the total aggregate components, and kneaded with a dispersant and a thickener.   Low outgas mortar or concrete in which limestone and artificial lightweight aggregates with no fracture surface on the surface are blended and kneaded with a dispersant and a thickener with a blending amount of 90% by mass or more of the total aggregate components. Low outgas mortar or concrete in which the amount of limestone is 90% by mass or more of the total aggregate components, and a dispersant and inorganic powder with a specific surface area of 1500 cm ² / g or more are mixed and kneaded. Low-outgas mortar with a blended amount of artificial lightweight aggregate that does not have a fracture surface on the surface and 90% by mass or more of the total aggregate components, and kneaded with a dispersant and inorganic powder with a specific surface area of 1500 cm ² / g or more Or concrete. Low outgas which knead compounded with limestone and artificial lightweight aggregate with no fracture surface on the surface, blending 90% by mass or more of total aggregate components, dispersant and inorganic powder with specific surface area of 1500cm ² / g or more Sex mortar or concrete.

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