JPH08133804A - Production of artificial sand for civil engineering and construction - Google Patents

Abstract

PURPOSE: To provide a method for producing artificial sand having high compression strength and good processability and capable of being produced in a large scale without requiring a firing process. CONSTITUTION: This method for producing artificial sand for civil engineering and construction is to add water or water and a curable synthetic resin to a mixed material made by adding fine powder of lime stone or blastfurnace slug or a mixture thereof to a neutralized sludge, and further mixing the above mentioned material with a cement and a cement solidifying assistant mainly containing a zinc compound, a stearate and an amino compound, knead and mix the mixture at a high speed and produce mixed sand having <=5mm granule size. Thus, artificial sand in which harmful metals included in the neutralized sludge are occluded in the granules can be obtained. The artificial sand gives concrete constructions which have good processability, beautiful shape after processing and excellent strength and are inexpensive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an artificial sand for civil engineering, which is used as a ground material or a building material for roads and building structures.

[0002]

2. Description of the Related Art River sand and sea sand are used for civil engineering work such as harbors and roads, or as ground material for construction of high-rise buildings and bridges and civil engineering construction sand. River sand has a problem that it cannot be supplied in large quantities due to the exhaustion of resources. On the other hand, sea sand
Unlike river sand, it has the advantage that it can be supplied in large quantities, but the salt content corrodes the reinforcing steel inside the building and leads to cracking and collapse of concrete structures, so it is desalinated and used without any salt. However, there is a problem in that a large amount of treated water and purification of the treated water are costly when attempting sufficient desalination.

Due to these problems, each company is developing artificial sand that uses unutilized resources such as minerals and factory waste materials as aggregate. For example, the "fine aggregate composition for concrete in which an aggregate such as light sand, clay, and shale is mixed with shirasu foam" disclosed in JP-A-51-151719 uses shirasu foam. Since there is a large difference in specific gravity between the aggregates, there is a problem that the aggregates are separated in the unsolidified concrete and are easily destroyed after the construction.

The "spherical hard artificial sand composed of SiO ₂ , CaO, Al ₂ O ₃ and MgO components" presented in Japanese Patent Publication No. 57-35144 has a low crushing and pulverizing rate and is hard and difficult to be crushed. However, since iron blast furnace slag was used as the starting aggregate, there was a problem that due to the problem of aggregate procurement, a large-scale production system could not be established in the future, and the price was high and natural sand could not compete with it.

Further, the artificial sand produced by the method for producing coal ash sand in which cement and water are added to coal ash and granulated by a high speed mixer described in JP-A-4-24304 is mainly composed of coal ash. Since it is used as an aggregate, its strength is weak and there is a problem that it can only be applied to non-building structural applications.

[0006] In addition to this, Japanese Unexamined Patent Publication (Kokai) No. 4-124051 discloses that a dry powder of a wastewater precipitate obtained by washing ground minerals with water is mixed with a calcium compound, kneaded, molded into spherical pellets and dried, There is also an artificial sand produced by the method for producing an artificial aggregate containing synthetic anorthite obtained by firing at.

As described above, various artificial sands for civil engineering construction have been developed using various aggregate compositions or special manufacturing methods. However, artificial sands to date include artificial sands of low strength that are easily broken as described above, artificial sands having a high water absorption of 30% or more, artificial sands that are produced in small quantities because the main aggregate cannot be procured in large quantities, There were many problems such as artificial sand with price problems.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the problems of conventional artificial sand, has a high concrete compressive strength in a manufacturing process that does not require a firing process, has good workability, and can be mass-produced. The purpose is to provide inexpensive artificial sand.

[0009]

[Means for Solving the Problems] The gist of the present invention is to mix neutralized sludge with coal ash, blast furnace slag fine powder or a mixture thereof, and further to prepare a cement-solidification aid containing zinc compounds, stearates and amino compounds as main components. This is a method for producing an artificial sand for civil engineering construction, in which water or water and a curable synthetic resin are added to a mixed material in which cement is mixed and kneaded at high speed to produce mixed sand having a particle size of 5 mm or less.

[0010]

The present invention will be described in detail below. In the present invention, first, a mixed material is produced by mixing neutralized sludge with coal ash, a cement-solidifying aid, and cement. Neutralization sludge is a weak acid of the pickling solution used to remove the oxide film adhering to the surface of the steel sheet after passing through the rolling process in the steel product manufacturing process or to activate the surface of the steel sheet before performing surface treatment. The waste liquid is treated with a neutralization treatment liquid, and the resulting precipitate is dehydrated and contains Ca, SiO ₂ , and Fe ₂ O ₃ as main components.

Natural sand has a high material strength because it contains a large amount of SiO ₂ . On the contrary, neutralization sludge is Si
Since it contains less O _{2 and} more Ca and Fe ₂ O ₃ , it has lower strength than natural sand. These three components contained in this neutralized sludge are also the main components of cement and have no problem of impairing the hardening property, facilitating granulation and improving the sphericity (sphericity) of artificial sand (particles). It is an effective ingredient. Figure 1 shows the relationship between the amount of artificial sand of each shape and the amount of cement used in concrete. Spherical particles have the effect of reducing the amount of cement used compared to particles of each shape or flat shape. Show.

Coal ash is the main aggregate of the present invention together with the neutralized sludge, and has the effect of absorbing the water contained in the neutralized sludge and controlling it to an appropriate amount of water necessary for granulation, while at the same time reducing the weight. Promote. Fly ash (fine ash of coal ash), which is also called cyclonast or fly ash of incineration ash generated when coal burns, is used as the coal ash. Regarding the amount of coal ash mixed in the neutralized sludge,
Although not particularly limited, 15 to 50% is preferable in view of various properties required for the sand for civil engineering and construction materials such as strength and workability. Further, in the present invention, a part or all of the coal ash can be replaced with the blast furnace slag fine powder.

Blast-furnace slag fine powder is produced by further crushing sand-like slag slag in the form of sand, which is obtained by rapidly cooling high-temperature slag generated during blast furnace operation. Is also cheap.

Further, in the present invention, a cement-solidifying aid containing zinc compounds, stearates and amino compounds as main components is mixed. The cement solidification aid promotes the solidification action of cement, imparts long-term strength to the ground material or building material, and is contained in neutralized sludge and coal ash, for example, cadmium, cyanide, organic phosphorus, hexavalent chromium, The harmful metals such as mercury are confined in the granulated particles after the high speed kneading, and the effect of preventing the elution of these metals is exerted.

Further, cement such as ordinary Portland cement and blast furnace cement is mixed as an adhesive. The cement acts as a “glue” between the neutralized sludge in the granulated particles and the coal ash, and firmly bonds the two. As a result, it improves the compressive strength and bending strength of mortar and concrete made from such granulated particles, and builds a robust civil engineering structure.

The composite material blended with the above aggregates is
In order to accelerate the hydration reaction of cement and to improve the spherical rate of granulated particles, water or water and acrylic or SBR
Add (styrene-butadiene-rubber) type curable synthetic resin and knead at high speed. In particular, it is preferable to use a curable synthetic resin in order to prevent an excessive increase in water absorption while improving the spherical rate of the granulated particles.

High-speed kneading is a kneading method necessary for strongly colliding the granulated particles with each other to produce strong granulated particles and constructing a solid civil engineering structure. On the contrary, in low-speed kneading, the collision force between the particles is weak and the particles become soft,
There is a problem of building fragile civil engineering structures.

The particle size of the granulated particles is 5 by the high speed kneading.
If the particles are excessively large, the particles having different aggregate compositions are produced, and it becomes impossible to construct a civil engineering structure having high strength and long life. On the other hand, if the fine particles are less than 5 mm, the fluidity is improved during construction, and a civil engineering structure that is economical, beautiful in formability, and robust is constructed. Therefore, it is necessary to manufacture the mixed sand composed of granulated particles having a particle size of 5 mm or less.

[0019]

EXAMPLES Next, examples of the present invention will be described. Neutralized sludge containing 30 to 40% water by drying, coal ash (15 to 100% by weight of neutralized sludge), cement solidification aid (1 to 2% by weight of neutralized sludge) and cement (40 to 55 weight of neutralized sludge) is mixed, and the mixed material mixed with water is rotated at high speed (400 to 3000).
Each particle size (0-5
mm) mixed artificial sand.

Mortar and concrete were molded using these mixed artificial sands. At this time, the composition of various mixed artificial sands and the properties required for mortar and concrete at that time were investigated. Examples of manufacturing artificial sand for construction are shown in Tables 1 to 4. Tables 1 and 2 are manufactured as rough sand equivalent products.

[0021]

[Table 1] No. No. 1 has a bad granule shape, but No. 2 to No. No. 4 was coarse in particle size, but could be completely granulated.

Table 2 is a summary of various characteristics of the granulated product.

[Table 2] It is necessary to combine mortar that can be used as it is with soft ground improvement materials, and sea sand as concrete fine aggregate.

Aiming at the standard particle size range of the JSCE fine aggregate,
Table 3 shows the particle size adjusted.

[Table 3] Sea sand has a specific gravity of 2.55, a water absorption rate of 2.04%, and an actual volume ratio of 65.
6%, F.I. M = 2.65, artificial sand for construction is mixed
No. 4 was used. From the above results, the mixing ratio of the artificial sand for construction and the sea sand, which is within the standard particle size curve of the fine aggregate, is artificial sand for construction: sea sand = 2.5: 7.5.

Table 4 shows the results of examining the strength change of 1.2 mortar specimens when the mixing ratio of artificial sand for construction and sea sand was changed.

[Table 4] The use of 25% artificial sand for construction gives results close to the mortar strength of 100% sea sand. Therefore, if the particle size distribution is improved, 100% of the artificial sand for construction can be used sufficiently.

Next, Tables 5 to 12 show examples in which artificial sand for construction having the characteristics shown in Tables 1 to 4 was used for concrete.
Shown in Tables 5 to 8 are examples in which artificial sand for construction corresponding to rough sand is used alone.

[0026]

[Table 5]

[0027]

[Table 6]

[0028]

[Table 7]

[0029]

[Table 8]

Tables 9 to 12 show the results of the use as fine aggregate with a controlled particle size.

[Table 9]

[0031]

[Table 10]

[0032]

[Table 11]

[0033]

[Table 12]

W / C = 55% even when artificial sand for construction is used alone
In this case, a 4-week strength of 197.4 kgf / cm ² can be secured, and it can be sufficiently used as artificial sand for civil engineering structures. That is, the allowable stress for concrete for civil engineering structures is mainly 60 kgf / cm ² , and even considering the safety factor 3, the 4-week strength is 180 kgf / cm ² , and the test value clears this value. Further, when the grain size is adjusted, it is possible to expect a four-week strength that is about twice as high as W / C. Therefore, it can be sufficiently used as the artificial sand for construction that the present inventors initially expected.

On the other hand, there is another aggregate particle shape in the evaluation of artificial sand. Most of the sand is crushed in the natural state, and even if it is caught in running water or waves, the corners are sharpened and the sand becomes naturally spherical. The shape of the aggregate is preferably spherical or close to a cube, and flat or elongated ones have a large porosity,
It is undesirable to have a large amount of cement paste needed to make the required workability concrete. Further, the squared one has a large friction between the aggregate grains, and this also requires an increase in the paste amount.

One of the methods for displaying the shape numerically is the sphericity (φ) expressed by the following formula. In the formula, a, b, and c are dimensions of each surface of the aggregate grain shown in FIG.

[Equation 1] In the case of crushed stone particles, the particle size is about 0.72, and the artificial sand for construction uses an ideal particle shape close to 1.0. These features are
It is effective not only for fine aggregate for concrete but also for ground improvement material (composer, sand material for vibro method).

[0037]

As described above, the construction method using the mixed artificial sand produced by the present invention has good workability, and the constructed civil engineering structure is strong and has a beautiful shape. further,
Since concrete with high compressive strength can be obtained at low cost, civil engineering structures can be economically constructed.

[Brief description of drawings]

FIG. 1 shows the relationship between the shape of aggregate and the required cement amount.

FIG. 2 is a diagram showing a measurement site of an aggregate grain shape for obtaining a sphericity.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kaigo Shimizu Inventor, 1-1 Hibahata-machi, Tobata-ku, Kitakyushu, Kitakyushu, Fukuoka Inside the Nippon Steel Corporation Yawata Works (72) Inventor Takao Yamamoto Yawatahigashi, Kitakyushu, Fukuoka 9-27 Kawabuchi-cho Taihei Kogyo Co., Ltd. Yawata Branch (72) Inventor Yasushi Omori 9-27 Kawabuchi-cho Yahatahigashi-ku, Kitakyushu, Kitakyushu Fukuoka Prefecture Taira Kogyo Co., Ltd. Yawata Branch (72) Inventor Takeshi Mizuta 8-14-24 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan Chemitac Co., Ltd.

Claims (1)

[Claims] 1. A composite material in which coal ash, blast furnace slag fine powder or a mixture thereof is mixed with neutralized sludge, and further a zinc compound powder, a cement solidification aid containing stearate and an amino compound as main components, and cement are mixed. A method for producing an artificial sand for civil engineering, which comprises mixing water or water and a curable synthetic resin at high speed to produce a mixed sand having a particle size of 5 mm or less.