JP5515870B2 - Blast furnace slag fine aggregate - Google Patents

Description

  The present invention relates to a blast furnace slag fine aggregate which is difficult to consolidate.

  Granulated blast furnace slag is produced directly into sand by injecting high-pressure water into molten slag discharged from the blast furnace and rapidly solidifying it. Blast furnace granulated slag can be used as a raw material for cement by finely pulverizing, as well as for civil engineering materials with as-manufactured granularity, and fine aggregate for concrete by adjusting the particle size and particle shape. The particle size and particle shape are adjusted by grinding the produced blast furnace granulated slag.

  When granulated blast furnace slag is used for fine aggregate for concrete, it may be piled up for a long period of time, and there is a problem of solidification. It is easy to consolidate especially when grinding. The cause of consolidation of granulated blast furnace slag is its latent hydraulic property, which is a necessary characteristic for cement raw materials. Therefore, when blast furnace slag manufactured for cement raw materials is also used for fine aggregate for concrete, measures to prevent caking are necessary. Many anti-caking technologies have been proposed in the past, but the most widely used is the method of adding an anti-caking agent to the granulated blast furnace slag (for example, see Patent Document 1). is there.

  By the way, in order to use granulated blast furnace slag as a fine aggregate for concrete, a quality equivalent to that of an existing fine aggregate may be required. Specifically, it has the same density and particle size distribution as natural sand. In general, blast furnace slag that is granulated immediately after being discharged from the blast furnace has a low density and a fine particle size. Therefore, once the rice is taken out, it is received in a pan and transported away from the blast furnace. There is also a manufacturing method. This is also called an out-of-furnace system. For example, Patent Document 2 discloses a coarsening technique using an out-of-furnace system. Although the granulated blast furnace slag by the out-of-furnace method has sufficient quality as a fine aggregate, it still has a problem of consolidation.

  For example, Patent Document 3 discloses a method for melting coal ash in a blast furnace slag received in a pan after pouring and water granulating the above problem. According to this technology, the coal ash is added to lower the viscosity of the molten slag to reduce the porosity of the slag and to reduce the vitrification rate to less than 80%, thereby suppressing consolidation.

Japanese Patent Laid-Open No. 54-130596 Japanese Patent Laid-Open No. 2001-240437 JP 2006-315907 A

  The present invention intends to provide a granulated blast furnace slag that is difficult to consolidate and a method for producing the same when the blast furnace slag is used for fine aggregate for concrete. In particular, a blast furnace granulated slag that does not exhibit latent hydraulic properties by adjusting the chemical components of the slag is provided.

In order to solve the above-mentioned problems, the present invention provides the following blast furnace slag fine aggregate.
(1) A blast furnace slag fine aggregate obtained by modifying blast furnace slag, wherein the content percentage by mass of the chemical components CaO and SiO ₂ is CaO / SiO ₂ <1, and 13 masses of Al ₂ O ₃ % by weight or more state, and are vitrification of 80% or more,
The total content of SiO ₂ and Al ₂ O _{3 in} the chemical components excluding the combustible components is 80% or more, and the ratio of the content mass% is SiO ₂ / Al ₂ O ₃ = 4.5 to 1. 5 to 10 to 30 parts by mass of the molten blast furnace slag 100 parts by mass to add and adjust chemical components,
The blast furnace slag fine aggregate is characterized in that the substance added for adjusting the chemical composition comprises a clayey substance and a siliceous substance . (2) The blast furnace slag fine aggregate as set forth in (1), wherein the clayey material is 50 to 80% by mass in a total of 100% by mass of the added clayey material and siliceous material. (3) In the CaO—SiO ₂ —Al ₂ O ₃ ternary phase diagram, the content percentage by mass of the chemical component of the blast furnace slag fine aggregate is (CaO: SiO ₂ : Al ₂ O ₃ ) = (39 : 43: 18), (37:40:23), and (34:48:18). The blast furnace slag fine bone according to (1) or (2) Wood.

  According to the present invention, it is not necessary to take an anti-caking measure by using an anti-caking agent and the post-manufacturing management of the fine aggregate is facilitated, and the utilization of granulated blast furnace slag is improved.

Is a _CaO-SiO 2 _-Al 2 _{O 3} ternary phase diagram showing the chemical composition of the slag.

Blast-furnace slag quality fine aggregate of the present invention, chemical components CaO, content wt% ratio of SiO ₂ is CaO / _SiO 2 <1, the _Al 2 _{O 3} containing 13 wt% or more, vitrification of 80% That's it. The inventors consider that it is difficult to satisfy the conflicting properties of hydraulic properties and hard-setting properties at the same time, and develop blast furnace slag that is hard to set and has reduced hydraulic properties, which is not particularly necessary for fine aggregate applications. Aimed. Usually, the content mass% ratio of the chemical components CaO and SiO ₂ of the blast furnace slag is operated at CaO / SiO ₂ = 1.2 to 1.3. When this component is used, the ground granulated blast furnace slag exhibits sufficient latent hydraulic properties. In JIS A6206, ((CaO%) + (MgO%) + (Al ₂ O ₃ %)) / (SiO ₂ %) ≧ 1.6 is defined for cement raw materials. Therefore, first, it was investigated the effect on caking of the chemical components, when a CaO / SiO 2 _<1 were found to the property of curing in most itself disappears.

  In addition, blast furnace slag for cement raw materials has improved latent hydraulic properties by making the vitrification rate close to 100% by rapid cooling by water granulation. For the blast furnace slag which is difficult to consolidate in the present invention, it was considered effective to lower the vitrification rate, but the low vitrification rate means that the crystallization rate is high, and in that case, the water granulation It was found that the pH of the water content of the slag was easily increased and induced caking. Therefore, in the present invention, it is preferable that the vitrification rate is high. If the vitrification rate was 80% or more, the caking was not affected.

  Regarding the judgment of consolidation, since the consolidation of blast furnace slag fine aggregate occurs in the summer (June to September), the aggregate should be observed for 3 months or more after constant temperature curing at 30 ° C. It can be hard to set. In general, the curing temperature is further raised and the test is often performed in a short period of time. In the present invention, it is considered that accurate determination is difficult with these methods, and the relative setting time obtained from the method according to Japanese Patent Application Laid-Open No. 2009-168802 was used. On the basis of a general blast furnace slag fine aggregate, if the consolidation time measured by the method is 30 to 40 days or more, it was judged to be hardly consolidated.

Components other than CaO and SiO _{2 in} the blast furnace slag fine aggregate of the present invention are not changed from the content before modification as much as possible. In particular, the third component, Al ₂ O _3, is contained in an amount of 13% by mass or more. When the Al ₂ O ₃ content is less than 13% by mass, the viscosity of the molten slag is rapidly increased, and it becomes difficult to produce fine aggregates by water granulation.

In the blast furnace slag fine aggregate of the present invention, more preferably, the content percentage by mass of the chemical component is (CaO: SiO ₂ : Al ₂ O _{3) in the} CaO—SiO ₂ —Al ₂ O ₃ ternary phase diagram. ) = (39:43:18), (37:40:23), and (34:48:18). FIG. 1 shows a CaO—SiO ₂ —Al ₂ O ₃ ternary phase diagram. Since the blast furnace slag fine aggregate of the present invention is produced by adding and melting a component adjusting material to normal blast furnace slag, the component adjusting material needs to be sufficiently melted. When adding any component adjusting material to the composition of the normal blast furnace slag shown in FIG. 1 to obtain a composition of CaO / SiO ₂ <1, it is preferable to make the melting point as low as possible. Moreover, it is easy to make vitrification rate high because melting | fusing point falls. As a result of intensive studies, in FIG. 1, (CaO: SiO ₂ : Al ₂ O ₃ ) is surrounded by the composition of (39:43:18), (37:40:23), and (34:48:18). A range was found to be preferred. Within this range, the melting point is about 1300 ° C. or less, and is the lowest melting point in the vicinity of the blast furnace slag composition. When the peripheral composition outside the range was also examined, a slag that was hard to consolidate was formed even in the composition outside the range, but the melting point was high, so that the production yield was lowered.

In the blast furnace slag fine aggregate of the present invention, for example, the total content of SiO ₂ and Al ₂ O _{3 in} the chemical components excluding combustible components is 80% or more, and the ratio of the content mass% is SiO _2. / Al ₂ O ₃ = 4.5 to 1.5 can be produced by adjusting the chemical component by adding 10 to 30 parts by mass with respect to 100 parts by mass of the blast furnace slag. In accordance with the above idea, the main component of the component-adjusting additive of the present invention is composed of SiO ₂ and Al ₂ O ₃ . The sum of the mass% of the components (SiO ₂ and Al ₂ O ₃ ) is 80% or more excluding combustible components. When the component mass% is less than 80%, when components other than SiO ₂ and Al ₂ O ₃ are added, the composition of the CaO—SiO ₂ —Al ₂ O ₃ ternary system can be controlled. It is not preferable because the melting point control becomes difficult due to the influence of the above components. The combustible component does not affect the composition control of the ternary system, and the combustible component is also effective as a heat source for maintaining the temperature of the blast furnace slag. Therefore, the total content by mass% of SiO ₂ and _Al 2 _{O 3)} may be at least 80% with the exception of the combustibles. Further, it is preferable that the ratio of the content by mass% is _{SiO 2 / Al 2 O 3 =} 4.5~1.5. If it is in this range, when it is gradually added to the blast furnace slag, the melting point gradually decreases, and the composition range of (CaO: SiO ₂ : Al ₂ O ₃ ) can be easily controlled. When the composition is other than SiO ₂ / Al ₂ O ₃ = 4.5 to 1.5, the melting point hardly decreases or increases, so that granulation is difficult and the yield may be decreased. Moreover, it is preferable that 10-30 mass parts is melt-added with respect to 100 mass parts of blast furnace slag as a component adjustment material. Melting addition means adding a component adjusting material to the molten blast furnace slag, melting the component adjusting material, and adding it to the blast furnace slag. In order to add a substance (component adjusting material) that satisfies the component conditions to the composition range of (CaO: SiO ₂ : Al ₂ O ₃ ), at least 10 parts by mass is required. If it exceeds 30 parts by mass, it deviates from the composition range of (CaO: SiO ₂ : Al ₂ O ₃ ), the melting point becomes high, the production is difficult, and the yield may be lowered.

  In the present invention, it is preferable to use coal ash as a substance to be added for adjusting the chemical components as described above. The chemical composition of the coal ash is in the range of chemical components necessary for the component-adjusting material of the present invention, and since carbon is included as a combustible component, it is also effective as a heat source for maintaining the temperature of the blast furnace slag.

In the present invention, it is also possible to use a substance composed of a clayey substance and a siliceous substance for chemical component adjustment. The main component of the clay material is composed of SiO ₂ and Al ₂ O ₃ , and for example, kaolinite, halosite, allophane, and the like can be used. The main component of the siliceous substance is SiO ₂ , and for example, silica sand, quartz dust, silica fume and the like can be used. And since it is difficult to control the composition range of the above (CaO: SiO ₂ : Al ₂ O ₃ ) by using each of them individually, both substances should be in the range of chemical components necessary for the component adjusting material of the present invention. Adjust the mixing. More preferably, of the total 100 mass% of the clayey material and siliceous material to be added, the clayey material is 50 to 80 mass%. If it is less than 50% by mass, it becomes difficult to dissolve uniformly due to an increase in the SiO ₂ component, and it becomes difficult to prevent stable consolidation. If it exceeds 80% by mass, the addition amount range in which the melting point is lowered becomes narrow and control becomes difficult. In the present invention, it is recommended to add a mixture of a siliceous material and a siliceous material, but it is also possible to first melt and add the siliceous material, and then melt and add the clayey material. In this method, it is possible to add more effectively while lowering the melting point, and it is possible to dissolve evenly.

  The conventional technology can be used to manufacture the blast furnace slag fine aggregate of the present invention. The molten slag extracted from the blast furnace is received in a pan, and the powder of the component adjusting material is blown into the molten slag and melted. The slag temperature for water granulation is not particularly limited as long as the component adjusting material is sufficiently dissolved, but as is clear from FIG. If the dissolution is insufficient, the anti-caking effect is not stable.

Tables 1 and 2 show the presence / absence of slag additives in the Reference Examples, Examples (Table 1) and Comparative Examples (Table 2), the three-component mass ratio, the vitrification rate, and the consolidation time. The chemical content of each additive substance is as follows: coal ash is SiO ₂ (59% by mass), Al ₂ O ₃ (26% by mass), C (9% by mass), clay is SiO ₂ (47% by mass), Al ₂ O ₃ (40% by mass), silica sand is SiO ₂ (93% by mass), and Al ₂ O ₃ (4% by mass). No. 1 (coal ash) is 20 parts by mass, No. 2, 3 (coal ash) is 15 parts by mass, No. 4 (coal ash) is 18 parts by mass, No. 5 (coal) Ashes) is 17 parts by mass, No. 6 (clay: silica sand = 80: 20) is 18 parts by mass, No. 7 (clay: silica sand = 70: 30) is 20 parts by mass, No. 8 (clay: silica sand = 70 : 30) is 17 parts by mass, and No. 9 (clay: silica sand = 50: 50) is 25 parts by mass.

The slag shown in the reference examples, examples and comparative examples was produced by the following method. About 40 t of molten slag discharged from the blast furnace was received in a slag pan and transferred to a powder blowing treatment plant. The slag temperature is about 1380 ° C. The powder blowing lance was immersed in the molten slag, and oxygen was used as the carrier gas, and the additive substance powder (component adjusting material) was blown at a rate of about 200 kg / min for about 40 minutes. When the carbon content in the additive substance was less than 5% by mass, pulverized coal was mixed to add the carbon content to 5% by mass or more and less than 20% by mass. The addition amount was adjusted by the blowing time while monitoring the remaining amount of the powder hopper. The slag temperature after the treatment is about 1300 ° C. Then, it moved to the water-crushing treatment plant of the out-of-furnace system, and performed normal water-granulation treatment. When powder blowing was not performed, the pan that received the molten slag was directly transferred to an outside furnace type water granulation treatment plant and subjected to water granulation treatment.

The vitrification rate was controlled by adjusting the time until the material was melted after the additive material was melted. When increasing the vitrification rate, perform water granulation as soon as possible. When normal molten blast furnace slag was granulated by an out-of-furnace system, it was difficult to increase the vitrification rate as high as that in the furnace-front system. On the other hand, the slag used in the present invention tends to vitrify because there are more SiO ₂ components than ordinary blast furnace slag, and even in the case of an out-of-furnace system, it is possible to achieve a vitrification rate comparable to that in the furnace-front system. . On the other hand, when lowering the vitrification rate, the standby time until water granulation was increased. The vitrification rate was determined by measuring the content ratio between the glass phase and the crystal phase using X-ray diffraction.

The consolidation time shown in the Reference Examples, Examples and Comparative Examples was measured using a method according to Japanese Patent Application Laid-Open No. 2009-168802. First, the produced granulated slag was dried at 110 ° C. for 2 hours, and then finely pulverized to 100 μm or less. Next, after adding 1 mL of pure water to 10 g of fine powder and mixing well, a cylindrical test body having a diameter of 20 mm and a length of about 18 mm was prepared using a uniaxial compression molding machine. Each specimen was sealed in a plastic bag and cured in a 30 ° C. curing tank. The sample was taken out from the curing tank in a timely manner, and the ultrasonic propagation time was measured. As consolidation progresses, the propagation time decreases. The propagation time immediately after molding was set as the maximum value, the propagation time when no further decrease was observed was set as the minimum value, and the curing time until reaching the intermediate value of these logarithms was set as the consolidation time. It is obvious that the propagation time immediately after molding is the same for all samples, but since it is empirically found that the minimum value where no further decrease is seen is the same value, this curing time is set to a maximum of 6 months When it did not converge to the minimum value within 6 months, it was decided to extrapolate the change in propagation time and estimate the curing time to reach the intermediate value as the consolidation time.

FIG. 1 shows the slag of Table 1 on a three-component phase diagram. Blast furnace slag before the addition treatment is represented by BF, and coal ash and clay used as additives are represented by FA and CL, respectively. The reference examples and the examples of the present invention are indicated by ●, the comparative examples are indicated by *, and the composition range of claim 2 is indicated by a thick triangular frame.

Reference Examples 1 to 5 are blast furnace slag fine aggregates with different coal ash addition rates. The content ratio by mass of the chemical components CaO and SiO ₂ is CaO / SiO ₂ <1, and the three component content ratios in the thick triangular frame in FIG. Moreover, the vitrification rate was 80% or more. When the consolidation time was measured, Reference Examples 2 and 3 were several tens of days. In Reference Examples 1 and 2, since the propagation time did not converge to the minimum value within 6 months, it was estimated by the above method, but it seems that it does not solidify for a very long time.

  Examples 6 to 9 are blast furnace slag fine aggregates in which the mixing ratio and addition ratio of clay and silica sand are changed. The mixing ratio of the clay was 50 to 80% by mass, and the mixture was added to the molten blast furnace slag at 17 to 25% by mass. The consolidation time was several tens of days to 200 days or more.

Comparative example 1 is a blast furnace granulated slag fine aggregate of the furnace type. Since the content percentage by mass of the chemical components CaO and SiO ₂ is as high as CaO / SiO ₂ = 1.24 and the vitrification rate is also high, it is very easy to consolidate. Comparative Example 2 is an out-of-furnace blast furnace granulated slag fine aggregate. Although the vitrification rate is low, on the contrary, there are many crystals, so that the alkali stimulus is increased and it is very easy to consolidate.

In Comparative Example 3, 14% by mass of coal ash was added to make CaO / SiO ₂ = 0.99 <1, but because the vitrification rate was about the same as Comparative Example 2, alkali stimulation occurred and the consolidation time was It didn't get too long. Further, Comparative Example 4 is an example in which the addition of coal ash 8.5 wt%, not built added amount is insufficient CaO / SiO 2 _<1 and, occurs alkali stimulus that vitrification rate is low The consolidation time is not so long.

Comparative Examples 5 to 7 are examples in which a mixture of clay and silica sand was added. Since the addition rate was 5 to 9% by mass, CaO / SiO ₂ <1 was not satisfied, and the consolidation time could not be made too long when the vitrification rate was 80% or more.

Claims (3)

A blast furnace slag fine aggregate obtained by modifying blast furnace slag, wherein the content ratio by mass of the chemical components CaO and SiO ₂ is CaO / SiO ₂ <1, and Al ₂ O ₃ is contained by 13 mass% or more. state, and are vitrification of 80% or more,
The total content of SiO ₂ and Al ₂ O _{3 in} the chemical components excluding the combustible components is 80% or more, and the ratio of the content mass% is SiO ₂ / Al ₂ O ₃ = 4.5 to 1. 5 to 10 to 30 parts by mass of the molten blast furnace slag 100 parts by mass to add and adjust chemical components,
The blast furnace slag fine aggregate is characterized in that the substance added for adjusting the chemical composition comprises a clayey substance and a siliceous substance .   2. The blast furnace slag fine aggregate according to claim 1, wherein the clay material is 50 to 80 mass% in a total of 100 mass% of the clay material and the siliceous material to be added.   The content percentage by mass of the chemical component of the blast furnace slag fine aggregate is CaO-SiO. ₂ -Al ₂ O ₃ In the ternary phase diagram, (CaO: SiO ₂ : Al ₂ O ₃ ) = (39:43:18), (37:40:23), (34:48:18) The range of the blast furnace slag quality according to claim 1 or 2, Fine aggregate.

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