JP2598616B2 - Fine aggregate obtained by crushing rhyolitic welded tuff and its production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine aggregate obtained by crushing rhyolitic (weak) welded tuff, which is used as crushed stone for concrete, and a method for producing the same.

[0002]

2. Description of the Related Art River sand is considered to be most preferable as fine aggregate. However, along with the depletion of river sand resources, recently, in addition to river sand, mountain sand, sea sand, land sand, crushed stone and the like are also used as fine aggregate. It is being used.

[0003] Rocks used as raw materials of crushed sand (hereinafter referred to as rough stones) are basalt, andesite, hard sandstone, hard limestone and the like. Soft sandstone, soft tuff, weathered rock and the like are unsuitable as crushed sand rough stones due to insufficient strength. Due to cost reasons, this crushed sand is passively used as a by-product generated at a certain rate during the production of crushed stones for coarse aggregates, and what has settled in the washing water of crushed dust. Only.

By the way, from Nara Prefecture to Mie Prefecture, Murou volcanic rock which is one of the fused tuffs is distributed. This welded tuff is a pyroclastic flow deposit due to Miocene volcanic activity, and the entirety is welded just like confectionery millet by the heat of the pyroclastic flow and the weight of the deposit.

[0005] This Murou volcanic rock is slightly used as rubble stone for civil engineering or crushed stone for roadbed material. However, as shown in FIG. According to JIS A 5005), the value of the stability test should be 12% or less, but crushed stone produced from Murou volcanic rock cannot be used as ordinary coarse aggregate because the value of the stability test is 20% or more and is poor. Was.

The Arima Group, mainly in the Arima district of Hyogo Prefecture, also known as rhyolitic welded tuff, is strongly consolidated by diagenesis forming sedimentary rocks, and is therefore processed into coarse aggregate. Although it is possible to use it and it is actually mining operation, commercial mining is not performed because the crushing cost is too large to process into fine aggregate.

[0007]

As the sources of fine aggregates are diversified into mountain sand, land sand and crushed stone sand, the production areas of each sand are becoming more residential and the regulations for environmental conservation are gradually being strengthened. It is
Under such an environment, there is a question whether domestic sand alone can sufficiently satisfy 500 million tons of domestic demand per year in the future.

In the Chugoku, Shikoku, and Kyushu regions in particular, most of the gravel depends on sea sand. However, the area where sea sand can be collected is decreasing year by year, and mountain sand and land sand contain organic impurities, mud, Sufficient water washing is required to remove the clay lumps, which increases costs. In addition, a large power is required to crush ordinary crushed stone to crushed sand, which increases the production cost.

As described above, crushed sand is not actively produced due to the crushing cost, but if the crushing cost is low, it can be a major supply source together with mountain sand and sea sand.

The present inventors have paid attention to the drawback that the aforementioned Murou volcanic rocks are unsuitable because they are easily broken as crushed stones. The hypothesis that this hypothesis could be used was made, and various experiments were conducted to confirm the validity of this hypothesis, and it was shown that rhyolite welded tuff, including Murou volcanic rock, would be useful as a raw stone for crushed sand. discovered. In particular, Murou volcanic rocks are distributed in the central Kinki region,
It is estimated that the layer thickness will reach 400 m or more and the total amount will reach 50 km ³ or more. If this can be used as fine aggregate, crushed sand can be supplied stably for a long time without importing crushed sand.

The present invention has been proposed based on a new finding that Murou volcanic rock can be used as a raw stone of crushed sand, and an object of the present invention is to enable a stable supply of fine aggregate at a low cost in the future. .

[0012]

In order to solve the above-mentioned problems, the present invention is characterized in that rhyolitic welded tuff is crushed to a particle size of 5 mm or less.

Further, according to the present invention, a crushed stone of rhyolitic welded tuff is separated at a welded portion by a hammer crusher to have a particle size of 5 mm.
It is characterized in that it is a crystal group of not more than mm.

[0014] More specifically, the rhyolitic welded tuff described above is characterized by being Murou volcanic rock.

[0015]

[Function] Rhyolite-welded tuff is composed of volcanic ash and pumice fragments-rich volcanic eruptions deposited at high temperatures, compressed and welded by the deposition load from above to solidify.

By using a hammer crusher,
Only the weakly viscous glassy part of the Murou volcanic rock is crushed. Therefore, it is possible to separate the crystals with relatively weak force at the interface between the crystals constituting the Murou volcanic rock. Good. In addition, when the particle diameter does not become 5 mm or less, almost all of it is crushed into crushed sand by being charged into the hammer crusher again.

The crushed stone thus produced from the fused tuff has a specific gravity of 2.52, a water absorption of 2.55% and a stability of 6.
3% and 5.8% of the total amount lost in the washing test satisfies the requirements for crushed stone for concrete of Japanese Industrial Standards (JIS A 5004).

The conditions of crushed stone used as coarse aggregate or crushed sand used as fine aggregate are determined by Japanese Industrial Standards (JIS A 5004 and A 5005) as shown in FIG. It is 2.5 or more and the water absorption is 3% or less. Furthermore, the stability of crushed stone is 12% or less, the amount lost in the washing test is 1% or less of the whole, and the crushed sand is 10% or less in stability and the amount lost in the washing test is 7% of the whole.
% Or less. This crushed stone or crushed stone sand preferably contains a large amount of quartz, feldspar and the like from the viewpoint of securing the required strength, and is crushed to a particle size of 0.074 m
It is better that mica and clay minerals, which are liable to generate fine powder (overcrushed material) of m or less, are small.

[0019]

Next, an embodiment of the present invention will be described with reference to FIG. This fine aggregate 1 uses Murou volcanic rock 2 as a raw stone.

The Muro volcanic rock 2 is a weakly welded layer mainly composed of columnar joints. Originally, a thin non-welded layer was located above and below it, but the weakly welded layer was exposed on the surface due to crustal deformation. It is. The sand particle size of the Murou volcanic rock is 5 mm or less, and is mostly about 1 to 2 mm. FIG. 2 is a diagram showing analysis values and norms of the Murou volcanic rock 2. According to FIG. 2, Murou volcanic rock 2 contains the largest amount of silicon dioxide, and its main crystals are high-temperature quartz, potassium feldspar and plagioclase.

The Murou volcanic rock 2 is mined by open pit mining. Since the Murou volcanic rock has columnar joints, it can be mined along the cracks. This columnar joint has a diameter of 1.0 to 1.5 m, and
Since plate joints are provided in the transverse direction at intervals slightly shorter than the diameter, the joints can be cut out as a lump having a size convenient for mining and transportation.

As shown in FIG. 1, this is crushed by using a jaw crusher A into an ore 2a large enough to be put into a cone crusher B.

The rough 2a is mixed with a cone crusher B for 50 minutes.
After secondary crushing into Oguri stone 2b having a diameter of about 100 mm to 100 mm, this Oguri stone 2b is put into a hammer crusher C,
Only the weakly welded portion (vitreous) 3 between the crystal grains is crushed three times, and the whole is crushed sand having a particle size of 5 mm or less. Note that the hammer crusher C is a device for crushing the Oguriishi 2b mainly by the hammer H and the rostor R at the tip of the arm.

The power required for secondary crushing and tertiary crushing will be described with reference to FIG. 3 in comparison with crushing of basalt and the like.

Basic crushing power value (WM value) of Murou volcanic rock 2
Is 20.8 (wh / t), about one-half as compared with the basic crushing power of limestone, and about one-third to one-quarter as compared with the basic crushing power of basalt. Low power value is required.

Further, the resistance to impact crushing of Murou volcanic rock 2 (C
Value) is 9.46 (ft · Lb / in), which is less than about one half of that of andesite or basalt.

The reason why the energy required for the crushing is small is that the high-temperature quartz 5 contained in the Murou volcanic rock 2,
This is because the main crystals such as potassium feldspar 6 and plagioclase 7 are kept as they are, and only the weakly welded portions (vitreous portions) 3 that are much more brittle than the respective crystals 5 to 7 between the crystals 5 to 7 are crushed. is there.

Therefore, in order to crush the Murou volcanic rock 2, the crushing capacity is designed based on the crushing data of the limestone, and the power (kw) of the motor is smaller than that of the limestone motor. Further, the Murou volcanic rock 2 can be easily crushed at a rotation speed lower than the rotation speed of a normal crushing machine.

As described above, most of the crystals separated at the weakly welded portions are high-temperature quartz 5, potassium feldspar 6, and plagioclase 7 (see FIG. 1). Used as fine aggregate 1.

Next, what characteristics the crushed stone produced from the Murou volcanic rock 2 has as the fine aggregate 1 will be described. In order to examine the quality as fine aggregate 1, a specific gravity test, a water absorption test, a stability test, and a washing test were respectively performed (J
IS A 5004).

FIG. 4 shows the results. According to FIG. 4, the absolute dry specific gravity of the crushed sand obtained by crushing the Murou volcanic rock 2 is 2.52,
The water absorption was 2.55%, the stability was 6.3%, and the amount lost in the washing test was 5.8% of the whole. From these figures, it was discovered that this crushed sand was sufficiently satisfactory as fine aggregate 1.

In particular, according to the method for testing the stability of aggregates with sodium sulfate (JIS A1122), the value of the stability test exceeded 20% at the stage of crushed stone having a particle size of 5 mm or more produced from Murou volcanic rock. On the other hand, by crushing the Murou volcanic rock 2 into crushed sand having a particle size of 5 mm or less, the numerical value of this stability test is greatly reduced to 6.3%. This is because the weakly welded portion 3 peculiar to the Murou volcanic rock 2 has a drawback in the stability test due to the intrusion of the sodium sulfate solution at the stage of crushed rock, but the crystal with a smooth surface is formed at the stage of crushed sand. And the use of a hammer crusher for crushing hardly damages the crystal, so that the sodium sulfate solution does not enter the crystal.

FIG. 5 shows crushing data of this embodiment. According to FIG. 5, the fine aggregate 1 obtained by crushing the Murou volcanic rock 2 has very little generation of fine powder having a particle size of 0.074 mm or less and conforms to Japanese Industrial Standards (JIS A 5004). Proven.

This means that the crushing energy is concentrated on the weakly welded portion 3, the crystal grains themselves are not crushed, and do not generate fine powder (over-crushed material).

It is to be noted that the recoverable amount of the Murou volcanic rock 2 is expected to be at least about 400 million m ³ and the amount of resources is extremely large, so that the demand in the Kinki region can be fully satisfied over a hundred and several decades.

Further, since the Murou volcanic rock 2 is crushed from the weakly welded portion 3 and the respective crystalline bodies 5 to 7 are not destroyed, there is almost no fine powder, and a dry manufacturing method in which a washing step can be omitted becomes possible, and the manufacturing cost can be greatly reduced.

[0037]

As described above, according to the present invention,
The rhyolite tuff, which is a rough stone, has a lower degree of welding than ordinary welded tuff and has a weaker bonding force between crystals, so it is easy to crush only the welded part when crushing, making it possible to produce crushed stone at very low cost. it can.

The rhyolitic tuff is preferably composed of high-temperature quartz or the like as crushed sand, and since mica and clay minerals are extremely small, fine aggregate produced by pulverizing it has almost no fine powder. Since water washing is not required, it is very suitable as crushed stone for concrete. In addition, Murou volcanic rock, a rhyolitic tuff, has a very large amount of resources. Therefore, it is necessary to supply high-quality fine aggregate free of impurities as crushed stone for concrete over a long period of time stably and inexpensively. Can be.

Further, the Murou volcanic rock has an effect that the transportation cost is low because the transportation is convenient adjacent to the large-scale consumption zone in the Kinki and Chubu areas, and the transportation cost can be suppressed.

[Brief description of the drawings]

FIG. 1 is a view schematically showing fine aggregate obtained by crushing Murou volcanic rock and a method for producing the fine aggregate.

FIG. 2 is a diagram showing analysis values and norm values of Murou volcanic rock.

FIG. 3 is a diagram showing a basic crushing power value (WM value) and an impact crush resistance value (C value).

FIG. 4 is a view showing aggregate performance of crushed stone and crushed stone manufactured from Murou volcanic rock.

FIG. 5 is a view showing crushing data of crushed sand obtained by crushing Muro volcanic rock and a particle size curve of crushed sand.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fine aggregate 2 Rhyolite welded tuff (Muro volcanic rock) 3 Welded part 5, 6, 7 Crystal C Hamma crusher

Claims (3)

(57) [Claims] 1. Fine aggregate obtained by crushing rhyolitic welded tuff to a particle size of 5 mm or less. 2. A method for producing fine aggregate, characterized in that crushed rhyolitic welded tuff is separated at a welded portion by a hammer crusher into crystallites having a grain size of 5 mm or less. 3. The fine aggregate according to claim 1, wherein the rhyolitic welded tuff is Muro volcanic rock.