JPS63270600A - Method for curing ready-mixed concrete sludge - Google Patents

Abstract

PURPOSE:To reutilize ready-mixed concrete sludge by dehydrating the sludge, and then adding a small amt. of cement to dry and cure the sludge. CONSTITUTION:The sludge obtained by removing the ballast and sand from ready-mixed concrete waste water is passed through a dehydrator to reduce the water content to about 50%, the water content is further reduced to about 20-30% by air drying, then about 10wt.% cement, based on the sludge, is added and kneaded, the kneaded material is pressure-formed (granulation) into a desired form, and the sludge is dried and cured by air drying or a drier. By this method, the formed material of sludge has excellent hardness equivalent to the hardness when ready-mixed concrete is cured. As a result, the material can be utilized as secondary materials such as roadbed reinforcing material, or the formed material in the form of pebbles is spread over acidified land, embedded, and utilized as the soil improving agent, etc., having a neutralizing action and a water infiltrating action.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention reuses ready-mixed concrete sludge, for which there is no other treatment method other than disposing of it as industrial waste, as a secondary material for various uses. This paper relates to a method for solidifying raw concrete sludge that makes it possible to do this.

(Prior art and problems) Among the various pollution problems that occur in ready-mixed concrete (hereinafter simply referred to as ready-mixed concrete) factories, the problem of treating wastewater containing ready-mixed concrete is particularly serious, and has become a major social problem in recent years. . For example, when a ready-mixed concrete mixer truck completes unloading of ready-mixed concrete and returns to the factory to clean the inside of the drum, a large amount of ready-mixed concrete water containing gravel, sand, cement, and mud is produced. The amount of residue removed from one ready-mixed concrete truck is 16.5 kg of gravel, 48.8 kg of sand, and 12.5 kg of ready-mixed concrete sludge in - times of washing. ff, the amount of ready-mixed concrete water including water is enormous. Another month's worth of sludge (
In a small-scale factory, the amount of generated concrete (including so-called returned ready-mixed concrete) is about 10m3. Approximately 50% of the moisture remains in the cake after the moisture is reduced by a dehydrator, which is 40 to 70 m3 in medium-sized factories and 130 to 200 m3 in large-scale factories.

Furthermore, since sludge has strong alkalinity and is said to be impossible to reuse, the large amount of sludge-like sludge that remains after removing gravel and sand and dewatering must be disposed of at ready-mixed concrete plants. This was impossible, and the only way to dispose of it was to ask a specialized disposal company to dispose of it. These specialized disposal companies construct enclosures made of concrete to prevent underground seepage in uninhabited mountains, etc., and dispose of the ready-mixed concrete in these enclosures, and after it dries and solidifies, they do not dispose of it in landfills. is common.

FIG. 3 is a table showing the drying time and the change in hardness at each elapsed time when sludge water that has been dehydrated to a water content of about 50% is naturally dried. As is clear from this table, as the drying time increases and the degree of dryness increases, the hardness of the sludge decreases. This is because there is no binder that binds the particles that make up the sludge, so the sludge becomes powdery when dried.

However, this type of waste disposal by landfill tends to become more difficult year by year due to various obstacles such as difficulty in securing a disposal site and legal regulations, and accordingly, the cost of waste disposal by specialized companies has increased significantly. 0 trending
For example, while the selling price of 1rn3'"il of ready-mixed concrete is 11,500 yen, the fee paid to a specialized treatment company is 15,800 yen to 20,000 yen per 1m3 of sludge water. For ready-mixed concrete companies, the more they dispose of sludge legally, the more economic losses they suffer.As a result, the number of companies illegally dumping sludge is rapidly increasing.

Additionally, surplus ready-mixed concrete brought back to the T site after unloading, known as returned ready-mixed concrete, was conventionally often discarded.
There was no existing method for utilizing RR.Also, methods of solidifying sludge by adding various chemicals to the sludge have been repeatedly proposed, but each method requires many types of additives. It was not possible to avoid complicating the process and increasing costs.

(Means for Solving the Problems) The present invention has been made in view of the above, and enables effective reuse by solidifying sludge without complicating the process or increasing costs. Therefore, the present invention provides a method for solidifying ready-mixed concrete sludge in which a small amount of cement is added after dewatering the ready-mixed concrete sludge water and then dried and solidified.

(Example) Hereinafter, the method for solidifying fresh concrete sludge of the present invention will be described in detail.

First, the first step of the method of the present invention is a sludge water dehydration step. In this step, gravel and sand are removed from the ready-mixed concrete wastewater obtained by washing the inside of the drum of a ready-mixed mixer truck, and the sludge water is converted into sludge water. Then, the sludge water is dehydrated and filtered using a dehydrator to reduce the water content to about 50%.

Next, the sludge-like sludge water obtained in this way is
The moisture content can be reduced to 20-30% by the natural drying process. The sludge in this state is a cake of wet powder.

The third step is a step of adding cement powder as a binder, in which about 10 tonne of dead cement of the sludge cake obtained in the second step 1 is added to the sludge cake and kneaded. The optimum amount of cement to be added varies depending on the time that has passed since the sludge was generated; the more one hour passes, the more the activity of the sludge decreases, so the amount of cement to be added increases. That is, FIG. 1 is a table showing the relationship between the amount (ratio) of cement added in the third step and the solidification rate corresponding to each amount of addition. The time required, that is, the time to start the third step, is approximately 7 hours after the sludge is generated. As is clear from this table, the amount of cement can be saved by adding cement as early as possible after sludge generation. In particular, cement addition treatment up to 20 hours after occurrence is the most economical.

The cement-added sludge obtained in the third step is
In the fourth step, the molding step, the sludge is press-molded (granulated) into the shape of fresh pickles. In the I&mold step, it is preferable to apply strong pressure. For example, when used as a roadbed reinforcement material, it is molded into the size of gravel or pebbles. It is also possible to configure it in the shape of a plate, a block, or the like. It should be noted that the higher the moisture content of the sludge cake, the more difficult it becomes to mold it, and the greater the amount of cement required to solidify it. That is, Figure 52 shows the relationship between the moisture content of the sludge cake and the cement and jll required for each moisture content, and molding is impossible when the moisture content exceeds 25%.

Finally, in the drying step, step :jrj5, the shaped sludge is dried and solidified. As for the drying method, natural drying outdoors is sufficient, but it may also be carried out using a drying device or the like.

The sludge molded product dried and solidified in this way has a state in which the granular or powdered sludge is strongly bonded and integrated by cement as a binder, and has sufficient strength comparable to the hardness of ready-mixed concrete. ing. Therefore, it can be applied to various things such as roadbed reinforcement materials as secondary materials. It can also be used as a soil conditioner.0For example, a large number of pebble-shaped sludge molded materials made by molding and solidifying sludge can be buried in areas where land is dying due to acidification. This makes it possible to form a layer that has a neutralizing effect and is permeable to water.

In addition, since the sludge water has the highest activity of 18 within 24 hours after its generation, less cement can be added.

(Effects of Plan J5) As described below, according to the method for solidifying ready-mixed concrete sludge of the present invention, it is possible to solidify sludge and utilize tri effectively without complicating the process or increasing costs. can be achieved.

[Brief explanation of the drawing]

Figure 1 shows the amount of cement added in the third step! A table showing the relationship between the solidification rate and the solidification rate corresponding to each addition amount,
Figure 2 is a table showing the relationship between the moisture content of sludge cake and the cement required for each moisture content. Figure 3 is a table showing the relationship between the moisture content of sludge cake and the cement required for each moisture content. A table showing the drying time in the case of drying and the change in hardness at each elapsed time. Patent applicant: Suemoto Kogyo Co., Ltd. FM, 1
．． Patent attorney Kenshichi Suzuki ton 1-pu power Q winter 1, combination, a Fig. 3 Bas 7-+7 sod-4 sputum

Claims (1)

[Claims] A method for solidifying ready-mixed concrete sludge, which is characterized in that after dehydrating the ready-mixed concrete sludge water, a small amount of cement is added and the mixture is dried and solidified.