JPH058132B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of the Invention] The present invention relates to blast furnace slag powder used as a material for civil engineering and construction. More specifically, for improving the properties of concrete, i.e.
The present invention relates to a method for improving the quality of blast furnace slag powder used in Portland cement or mixed cement concrete in order to reduce heat of hydration, improve chemical resistance, or suppress alkaline aggregate reaction. [Background of the Invention] Blast furnace slag, which is produced as a by-product in steel mills, has the property of being stimulated and hardened (latent hydraulicity) by, for example, alkaline components eluted during cement hydration. used in the production of concrete. Furthermore, in recent years, with the decrease in quality aggregates for concrete, deterioration of structures due to alkaline aggregate reactions has become a problem, and the use of blast furnace slag has been recommended as one of the countermeasures. In addition, concrete containing blast furnace slag is known to have excellent properties such as heat of hydration, chemical resistance, seawater resistance, and heat resistance. For this reason, cement and concrete to which blast furnace slag has been added are widely used in dam construction, port construction, sewerage construction, grouting construction, etc. However, when blast furnace slag is added, there are problems such as the development of initial strength is generally delayed, and concrete to which a large amount of blast furnace slag is added has a large surface deterioration or shrinkage during drying. Blast furnace slag is pulverized and then added to Portland cement or mixed cement, or mixed and pulverized with Portland cement clinker. In addition, blast furnace slag powder is added when producing ready-mixed concrete or when producing secondary products such as various building materials and humid pipes. [Prior Art and Problems] As mentioned above, blast furnace slag is used in a wide range of civil engineering and construction fields, but on the other hand, cement or concrete containing blast furnace slag has a problem in that the development of initial strength is delayed. This decrease in initial strength increases as the amount of blast furnace slag increases, and becomes more pronounced as the curing temperature decreases. Known methods for improving the strength of blast furnace slag powder include highly pulverizing blast furnace slag, adding admixtures, and modifying blast furnace slag itself. this house,
Regarding the method described above, for example, by pulverizing the material to a Blaine specific surface area of about 8000 cm ² /g, the strength development property is considerably improved. However, since the pulverizability of blast furnace slag is generally low, producing high-quality pulverization as described above requires an increase in the power required for pulverization and an increase in the amount of wear of the pulverizing media, resulting in significantly higher manufacturing costs. There are problems such as a decline in liquidity. As for the method, admixtures such as limestone powder, slaked lime, chlorides, sulfates, water glass, and caustic alkali are known. These admixtures are effective in improving initial strength, but there are problems such as long-term strength being lower than when no admixture is added, and durability (salt damage, alkali aggregate reaction, etc.) decreasing. It was hot. As for a further method, a composition adjusting agent is added to the molten slag to create a glass composition (mainly CaO,
Methods of optimizing the cooling conditions (such _as quenching starting temperature, method, speed, atmosphere, etc.) or limiting the cooling conditions (quenching start temperature, method, speed, atmosphere _, etc.) have been adopted. However, these methods are only possible when the blast furnace slag is still in a molten state, that is, only in steel plants, and the places where they can be implemented are limited.
The operation was complicated, as it was necessary to control the composition, particle size, amount added, and cooling conditions in a timely manner. Further, although this method can be expected to have a certain degree of improvement effect, it cannot be said to be sufficient. As described above, conventional methods have had many problems in easily and inexpensively producing blast furnace slag powder that exhibits excellent initial and long-term strength development without impairing other properties. [Purpose of the invention] The present invention is directed to an admixture for blast furnace slag that exhibits excellent strength at early and long-term ages and is particularly effective during low-temperature curing, as well as a blast furnace slag composition (blast furnace slag and admixture). These products can ultimately be used in civil engineering and construction work, building materials, and the manufacture of various secondary products. Note that the admixture and blast furnace slag composition of the present invention do not impair durability (alkali aggregate reaction, salt damage). [Summary of the Invention] The present invention provides calcium carbonate, calcium oxide,
The present invention relates to a blast furnace slag admixture comprising a mixture of alkali sulfate and anhydrous gypsum, and a blast furnace slag composition comprising this admixture and blast furnace slag. [Detailed Description of the Invention] The blast furnace slag admixture of the present invention consists of calcium carbonate, calcium oxide, alkali sulfate and anhydrous gypsum. Among these, as the calcium carbonate, crushed limestone, chemically manufactured or by-product heavy or light calcium carbonate, etc. can be used. Calcium oxide obtained by calcining calcium carbonate and calcium hydroxide can be used.
Examples of alkali sulfates include sodium sulfate and potassium sulfate. As the anhydrous gypsum, type anhydrous gypsum is preferred. These constituents may be present alone or as double salts (e.g. 2CaO・_SiO2・
CaCO ₃ , 2CaO・SiO ₂・CaSO ₄ , 2CaSO ₄・
K ₂ SO ₄ ). The composition ratio of the admixture for blast furnace slag is 10 to 50% by weight of calcium carbonate and 5% by weight of calcium oxide.
-30% by weight, 5-20% by weight alkali sulfate and 5-40% by weight anhydrous gypsum. More preferred proportions of the constituents are 10 to 35% by weight of calcium carbonate, 5 to 20% by weight of calcium oxide, 5 to 15% by weight of alkali sulfate, and 10 to 30% by weight of type anhydrous gypsum, in which case _SiO2 ,
There is no problem even if Al ₂ O ₃ , Fe ₂ O ₃ , MgO and these compounds coexist. The proportion of the components is 10 to 50% by weight of calcium carbonate and 5 to 50% by weight of calcium oxide.
30% by weight, alkali sulfate from 5 to 20% by weight, and anhydrous gypsum from 5 to 40% by weight, the initial strength improvement effect is insufficient, long-term strength decreases, or strength development during low temperature curing occurs. There are problems such as inferior performance. The amount of the admixture of the present invention added to blast furnace slag is 1 to 20%, preferably 2.5 to 10%, based on the external weight.
% is desirable. If it is less than 1%, no significant effect of improving the quality of blast furnace slag can be expected, and if it exceeds 20%, the characteristics of blast furnace slag as an admixture for cement will be impaired, which is not preferable. In this case, the fineness of blast furnace slag powder is normal particle size (Blaine value 3500-5500cm ² /g)
can be used. As mentioned above, the admixture can be produced by mixing the required amounts of each component, but it is also possible to use an admixture that matches the types of the components and their mixing ratios, or an admixture that is similar to that. For example, it is also possible to use kottler dust, boiler dust, etc., which is called kiln dust, which is a by-product of cement manufacturing equipment. If the constituent components deviate from the proportions set forth in claim 2 of the present application, a sufficient effect can be achieved by appropriately correcting the deficiency. These constituent components in the dust are often present in the form of double salts, and this has an extremely favorable effect on improving the properties of blast furnace slag.
The composition of kiln dust varies considerably depending on the type of cement manufacturing equipment (NSP, SP, DB, etc.), and as an admixture in this application, DB is used as an admixture.
(Kiln with a dry boiler), particularly kiln dust, is preferred. Examples 1 to 3, Comparative Examples 1 to 6 Admixtures were prepared by changing the blending ratios of calcium carbonate, calcium oxide, potassium sulfate (anhydrous salt), and type anhydrous gypsum. A blast furnace slag composition was prepared by adding 5% by weight (internal division basis) of this admixture to blast furnace slag powder (Blaine specific surface area 4300 cm ² /g). Furthermore, blast furnace cement made by adding this blast furnace slag composition to ordinary Portland cement in an amount of 50% by weight (based on internal percentage) was tested in accordance with JIS R 5201-1981 ``Physical Test Methods for Cement''.
The mortar strength was tested. The mortar compressive strength of these blast furnace cements is shown in Table 1, expressed as a strength ratio when that of ordinary Portland cement is taken as 100.

[Table] Examples 4 to 5, Comparative Examples 7 to 8 In Example 2, the mortar strength was tested by changing the mixing ratio of the admixture to the blast furnace slag powder. The results are shown in Table 2.

[Table] Examples 6 to 9 Kottorel dust from DB (dry boiler kiln) was used as an admixture, and 7.5% by weight (internal division basis) was added to blast furnace slag powder (Blaine specific surface area 4060 cm ² /g). A blast furnace slag composition was prepared.
Furthermore, for blast furnace cement made by adding this blast furnace slag composition to ordinary Portland cement in an amount of 50% by weight (inner division basis), the results of 3. The mortar strength was tested on days 1, 7 and 28. Table 3 shows the chemical composition of Kottorel dust, and the norm of this dust is calcium carbonate 25
Weight%, calcium oxide 8% by weight, potassium sulfate 9% by weight, anhydrous gypsum 19% by weight, 2CaO・SiO ₂ 20
6% by weight of quartz and 13% by weight of others.
However, this norm includes the above compound in the double salt. In addition, using the admixture of Example 2, the same procedure as above was carried out.
Blast furnace slag composition and blast furnace cement (blast furnace slag composition 50% by weight) were prepared by adding 7.5% by weight,
The mortar strength was tested when cured in water at 20°C and 20°C.
Blast furnace cement without adding admixtures (blast furnace slag amount
The mortar strength of each material age when curing at 20°C with
7) When using the admixture of Example 2 (Examples 8 and 9)
Table 4 shows the mortar strength ratio (compression) of .

【table】

[Table] In addition, the heat of hydration was measured and
An alkaline aggregate reaction test was conducted using ASTM C 227 (mortar bar method), and the results were not significantly different from those obtained when no admixture was added. [Effects of the invention] Blast furnace slag powder is added during the production of cement, ready-mixed concrete, building materials, secondary products, etc., with the main purposes of reducing heat of hydration, improving chemical resistance, and suppressing alkali aggregate reactions. However, this addition generally causes a problem in that the initial strength, especially during low temperature curing, is considerably reduced. Conventional methods for improving this have included pulverization of blast furnace slag, addition of various admixtures, chemical components, etc.
Modification of blast furnace slag itself, such as adjusting the vitrification rate, is known. However, these methods have had problems such as a significant increase in manufacturing costs, insufficient effect of improving strength development during low temperature curing, reduction in long-term strength development, and restrictions on the locations where they can be applied. As a result of various studies regarding the above-mentioned problems, it was discovered that an admixture mainly consisting of calcium carbonate, calcium oxide, alkali sulfate, and anhydrous gypsum can activate blast furnace slag through their synergistic effect. This effect improves both initial strength and long-term strength, and can be said to be an excellent improvement method that cannot be achieved by adding the above constituent components alone. Furthermore, it has been found that dust from a cement kiln containing the constituent components of the present invention is excellent as a stimulant for blast furnace slag, and is particularly effective in improving strength development during low-temperature curing. This makes it possible to provide an admixture with excellent strength development without impairing the characteristics of blast furnace slag addition (heat of hydration, durability), as well as blast furnace slag compositions and blast furnace cement containing this admixture. Summer.

Claims (1)

[Claims] 1. An admixture for blast furnace slag comprising a mixture of calcium carbonate, calcium oxide, alkali sulfate and anhydrous gypsum. 2. The blend for blast furnace slag according to claim 1, which contains 10 to 50% by weight of calcium carbonate, 5 to 30% by weight of calcium oxide, 5 to 20% by weight of alkali sulfate, and 5 to 40% by weight of anhydrous gypsum. agent. 3 100 parts by weight of blast furnace slag powder and calcium carbonate,
A blast furnace slag composition comprising 1 to 20 parts by weight of a mixture of calcium oxide, alkali sulfate and anhydrous gypsum. 4. The blast furnace slag composition according to claim 3, wherein part or all of the mixture is Kottle dust or boiler dust generated in the cement manufacturing process.