JPH0135787B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing aggregate for concrete, which reduces and utilizes concrete waste liquid generated in a concrete product manufacturing factory.

(Conventional technology) Concrete product factories such as concrete poles, piles, and humid pipes use centrifugal force compaction to form and manufacture concrete products, and during this centrifugal force forming, approximately 4 to 6% of the product weight is produced as concrete waste liquid. is squeezed out.

The concrete waste liquid squeezed out in this way is
Disposing of the sludge as is would cause pollution, so the solids were first precipitated and the supernatant liquid was neutralized with acid before being discharged. Disposal of tons of waste is a problem from the perspective of environmental conservation, and it is also expected that it will be difficult to secure a landfill site, so the process will eventually come to a dead end. It seems inevitable.

Therefore, it is necessary to consider ways to recycle concrete waste liquid, and the reuse methods that have been studied so far include using concrete waste liquid as it is for making concrete, and recycling it into aggregate for concrete. There are two ways to do this.

In the former case, concrete waste liquid is considered to be separated into water and sludge, with the water being used as mixing water and the sludge being used as cement and fine aggregate. Most of the river gravel and sand used as materials have been mined, and now we are relying on expensive crushed sand as fine aggregate and sea sand, which is at risk of salt damage, while crushed stone and artificial aggregate are being used as coarse aggregate. The use of has been increasing in recent years.

Expansive rock, mining aggregate, fly assemblage, etc., began to be used for these artificial aggregates around 1965, and the amount was initially around 300,000 tons per year, but rapidly increased to around 9 million tons in 1980. Attempts have been made to reuse cement waste sludge as a material for these artificial aggregates, and small and medium-sized business associations are also focusing their efforts.

(Problems to be Solved by the Invention) When using the above-mentioned cement waste liquid and trying to mix it into concrete as it is, it is difficult to determine the mixing ratio because the ratio of water and sludge in the concrete waste liquid is not constant. Concrete waste liquid deteriorates over time, so it needs to be digested as quickly as possible, but planned digestion is difficult because the amount discharged varies depending on the plant or operating time. There are practical difficulties, such as the production of concrete, and quality problems such as large shrinkage when made into concrete products.

In addition, when using sludge as aggregate for concrete, conventional research has included firing in the process, which requires about 14,000 yen per ton of utilities for this firing, and on top of that, the fired material is put through a crusher. Since it must be crushed into small pieces, it is difficult to put it into practical use due to cost.

Furthermore, in order to implement this, existing treatment facilities could no longer be used, and new equipment such as baking equipment would need to be invested, which would require a huge amount of money.

The object of the present invention is to solve the above-mentioned problems in reusing sludge as aggregate for concrete, and to produce aggregate for concrete by a simple method and at low cost.

(Means for Solving the Problems) To achieve the above object, the present invention uses sludge obtained by dehydrating concrete waste liquid and fine particles of inorganic material such as silica sand or metallic material such as iron powder. This is a method for producing aggregate for concrete using concrete waste liquid, which is fed into a device with a granulation function to form granules with fine particles attached to the outer periphery.

When the granules thus obtained are left to stand for 2 to 3 days, they harden and can be used as aggregate for concrete.

(Function) When sludge and fine particles obtained by dehydrating concrete waste liquid are put into a device with a granulation function (a concrete mixer can also be used in addition to a granulator) and granulated, the sludge and fine particles obtained by dehydrating concrete waste liquid are granulated. Particles of various sizes are obtained with fine particles attached to them.

These fine particles have the function of preventing adhesion with other particles, and by selecting the type of fine particles, they can improve the properties of sludge and chemically stabilize concrete (for example, It can have functions such as delaying sexualization or reducing alkaline reactions.
The key point of the present invention is that uncured sludge can be successfully granulated by using these fine particles.

(Example) Sludge obtained from concrete waste liquid discharged from the manufacture of concrete products by centrifugal compaction has a cement content of over 70% and has sufficient hydraulic properties, so it can be ground into granules. They began research on the idea that it could be used as aggregate for concrete.

The components of sludge obtained from concrete drainage when concrete poles, piles, fume pipes, etc. are formed by centrifugal compaction are as follows.

Cement 73.9% Aggregate 12.8% Bound water 13.3% However, the amount that passes through a 0.15 mm sieve (Cement Concrete Magazine 1973 No. 318 P37
(Based on materials by Mr. Rokuro Sugiki) In order to find out whether the same sludge as above has the strength as an aggregate for concrete, the inventor used dewatered sludge obtained from concrete waste liquid 3 hours after it had been discharged to create a 10 cmφ x 20 cmH cylindrical specimen. As a result, the compressive strength of the material at 28 days of age was 250 to 300 Kg/ ^cm2 .

Next, the waste liquid with the same components as above is dehydrated and made into plate-shaped sludge, which is then crushed and sieved to 5 mm to 20 mm to make coarse aggregate. Concrete is made using 180 kg of cement per ¹ m3. A strength comparison test was conducted with similar concrete using crushed stone as aggregate. In other words, as in the strength test of the sludge itself, the material age was measured as a 10 cmφ x 20 cmH cylindrical specimen.
The average compressive strength of the three pieces on the 28th was examined and the following results were obtained.

Item using crushed stone 205Kg/cm ² Item using sludge aggregate using the method of the present invention
201Kg/cm ² Since the above results are almost the same, it is recognized that cement sludge can be used as is as aggregate.

Subsequently, various concretes with different compositions were made using the sludge aggregate produced by the method of the present invention, and compression tests similar to those described above were conducted. As a result, it was found that the sludge aggregate could be used as an aggregate for concrete with a strength of up to 300 kg/ ^cm2 . The conclusion was obtained.

The tests for confirming the possibility have been described above, and next, an example of a method for producing aggregate for concrete using concrete waste liquid will be described.

A dehydrator (manufactured by Hitachi, Ltd.) removes concrete waste liquid discharged within 4 hours from the manufacture of concrete poles, piles, humid pipes, etc. by centrifugal compaction.
TFA-10-28 type filter press method) to dehydrate to obtain a plate-shaped sludge measuring 50 cm x 60 cm x 2.5 cm.

In this case, the waste liquid separated from the sludge is reused as concrete mixing water after neutralization.

The sludge and fine particles (using silica sand from Gotsu) immediately after the above dehydration treatment were put into a granulator (a TM-55 small mixer for test kneading manufactured by Pacific Metals), which was rotated at 74 RPM. .

As a result, the plate-shaped sludge is gradually broken into smaller pieces, and the broken pieces become rounded and almost spherical, and fine particles adhere to the surface of the pieces to prevent other sludge from adhering to them.

In this case, it is better to use a slightly larger amount of fine particles, so that the excess fine particles do not adhere to the sludge, but remain in the concrete mixer and can be used for the next production.

In this way, granules coated with fine particles with a diameter of 2.5 mm to 40 mm are obtained, and if these granules are taken out of the granulator and allowed to age for 3 days or more, concrete aggregate with a hardness that can withstand the mixing of concrete can be obtained. The strength of the obtained concrete increases with the concrete that is subsequently mixed.

Small particles of 5 mm or less that occur during granulation can be used as fine aggregate in place of sand, but the generation rate of this fine aggregate can be kept low compared to crushed stone or crushed sand, and furthermore, the method of the present invention Experiments have shown that the use of sludge aggregate reduces the amount of cement and water used compared to using crushed stone.

This is because the sludge aggregate according to the present invention has a high actual area ratio because it has no corners and is almost spherical. (The actual area ratio of crushed stone is 55 to 60%, and the actual area ratio of the sludge aggregate according to the present invention is 65 to 70%) The above manufacturing process is summarized in FIG. 1.

The cement aggregate thus obtained has a surface dry specific gravity of 2.1 and a water content of about 21%, and the weight of concrete using the sludge aggregate of the present invention is 12% compared to that using crushed stone. % lighter.

In addition to silica sand, we tested crushed sand, fly ash, cement, etc. as fine particles, and all of them gave good results, especially when it is desired to use aggregate that can withstand chemical changes such as neutralization or alkali aggregate reactions. Fly ash is appropriate, and cement is used when trying to increase the strength of the aggregate.

In this way, fine particles can be used in various ways depending on the purpose.

In addition to the above-mentioned fine particles, it is also possible to use powders mixed with metals, such as iron powder, and even metal powders such as iron powder, which means that they do not reduce the strength of concrete. Any fine particles can be used.

In addition to the above-mentioned high-strength mixing mixer, devices having a granulation function include a tilting mixer for concrete, a crusher for aggregate, a breaker, a rod mill, and the like.

Next, the results of a compressive strength comparison test between the sludge aggregate according to the present invention and concrete using conventional crushed stone will be explained.

Attached Table 1 is a comparison where the blending conditions were changed to match the slumps as much as possible (the results were quite different), and Attached Table 2 is a comparison where the blending conditions were unified.

In Attached Tables 1 and 2, test numbers A used crushed stone, B and C used sludge aggregate according to the present invention, and the compressive strength of both was 10cmφ×20
The average value of the results of three tests using cmH specimens is shown.

In Attached Table 1 of the above test results, from test number 1A.
Both 1B and 2B are stronger than 2A, and 3A
and 3B have almost the same strength, and from this result, when the sludge aggregate obtained by the method of the present invention is used instead of crushed stone as coarse aggregate, the strength is equivalent to or higher than that using crushed stone, and the strength of the mixture is It was found that if done properly, the strength could be significantly increased.

In addition, in Attached Table 2, when using the sludge aggregate according to the present invention with the same volume as crushed stone (there is a difference in weight display due to the difference in specific gravity) as coarse aggregate, the strength is inferior to that using crushed stone. I understood.

From the results in Attached Tables 1 and 2 above, when using the sludge aggregate according to the present invention, it is proven that it has sufficient value as an aggregate for concrete, although special attention must be paid to the mixing in order to take advantage of its characteristics. It was done.

(Effects of the Invention) According to the method of the present invention explained above, effective aggregate for concrete can be obtained from concrete waste liquid very easily and at low cost. It is economically extremely advantageous because it can be reused in products, eliminates pollution caused by disposal, reduces the amount of depleted natural aggregate used, and prevents destruction of the natural environment as much as possible.
It is possible to provide a method for producing aggregate for concrete using concrete waste liquid, which can bring good news not only to next product manufacturing plants but also to the entire concrete industry.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the manufacturing process of the present invention.

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Claims (1)

[Claims] 1. Putting sludge obtained by dehydrating concrete waste liquid and fine particles of inorganic material such as silica sand or metallic material such as iron powder into a device with a granulation function,
A method for producing aggregate for concrete using concrete waste liquid, characterized in that it is made into granules with fine particles attached to the outer periphery.