JPH10167778A - Treatment of cement-containing waste mud, hydraulic dried powder and its utilization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently treating a cement-containing waste mud such as a slime rejected with soil improving construction works, etc., or a ready mixed concrete waste mud rejected from a ready-mixed concrete factory, etc., obtain a hydraulic dried powder of the cement-containing waste mud and further provide a defnite method for utilizing the dried powder. SOLUTION: This method for treating a cement-containing waste mud comprises forcibly pulverizing and drying an unhardened cement-containing waste mud or its dehydrated cake. Thereby, a hydraulic dried powder having <=12% moisture content and >=20% unhardened cement is obtained. The method for carrying out the solidifying treatment of a hydrous waste mud comprises mixing the hydraulic dried powder with a cement substitute material or a cement admixture comprising the hydraulic dried powder and the hydrous waste mud, granulating the resultant mixture and solidifying the granulated material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating cement-containing waste mud, a hydraulically-dried powder obtained by treating cement-containing waste mud, and a method for using the dried powder.

[0002]

2. Description of the Related Art In civil engineering works and construction works using cement, various waste muds containing cement are generated.
For example, in the improvement work of soft ground, water stoppage work of excavated ground, construction of underground piles and underground walls, etc., the cement ground such as cement milk is applied to the ground to be improved by chemical injection method or high pressure injection injection method. When the solidifying material is injected, a large amount of waste clay containing cement called slime is generated.

[0003] The slime is a slurry having a very high moisture content, having a solid content of about several percent, and contains cement derived from a cement-based solidified material and earth and sand removed from an improved ground. Some of this cement is hardened, but most remains unhardened. The slime containing unhardened cement exhibits a very strong alkalinity, cannot be disposed or landfilled as it is, and is difficult to handle because of its solidifying property.

[0004] At the ground improvement construction site, slime collected in a tank or the like is dewatered by a dewatering equipment such as a belt press to reduce the volume of slime generated and to facilitate transportation, and the water content is reduced to about 40 to 70%. Dehydrated cake is transported to the slime processing center. In a slime treatment center, it is common to add quicklime or a polymer-based water-absorbing material to the dehydrated cake, solidify it in a state where the water content is further reduced, carry it to a final disposal site, and dispose of it. Therefore, the processing cost becomes enormous, and reuse of this slime is desired.

[0005] In a ready-mixed concrete factory or a construction site, unwashed cement-containing waste mud is generated when washing a ready-mixed transport vehicle or a pump truck. As with the slime, the ready-mixed waste mud is difficult to treat, and it is a fact that it is solidified at great cost and discarded.

[0006] However, although it contains unhardened cement, its solid content concentration and degree of hydration vary, and these cannot be reused as raw material cement as it is. It has been proposed to use the solidified material as a backfill material. However, even if a dehydration operation is performed to reduce a large amount of water, the dewatered cake still contains tens of percent of water. It was necessary to add a large amount of dry powder to the dried powder, and if this dry powder was prepared from a dehydrated cake, the drying cost was high and the method was not practical.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for efficiently treating cement-containing waste mud such as slime generated from soil improvement work and ready-mixed concrete waste mud generated from a ready-mixed concrete factory. To provide. Another object of the present invention is to provide a hydraulic dry powder that can be used for various purposes from such cement-containing waste mud.
It is a further object of the present invention to provide a specific method of using such a hydraulically dried powder.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, forcibly pulverize and dry the cement-containing waste mud to recover it as dry powder. The present inventors have found that the dried powder has hydraulic properties and can be effectively used as a cement substitute, a cement admixture, and the like, and thus completed the present invention.

That is, the present invention is a method for treating cement-containing waste mud, which comprises forcibly pulverizing and drying uncured cement-containing waste mud or a dewatered cake thereof.

Further, the present invention is a hydraulically-dried powder having a moisture content of 12% or less and an uncured cement of 20% or more obtained by forcibly pulverizing and drying uncured cement-containing waste mud or a dewatered cake thereof.

Further, the present invention is a cement substitute made of the above-mentioned hydraulic dried powder, and a cement admixture made of the above-mentioned hydraulic dried powder.

Further, the present invention is a method for solidifying a water-containing waste mud, which comprises mixing the above-mentioned hydraulically-dried powder with the water-containing waste mud, granulating the mixture, and solidifying the granulated material.

Hereinafter, the present invention will be described in detail. Examples of the uncured cement-containing waste mud to which the treatment method of the present invention can be applied include slime generated in ground improvement work and the like, ready-mixed concrete waste mud generated in a ready-mixed concrete factory, a construction site, a cement secondary product factory, and the like. For example, the former slime can be used to improve the soft ground, excavate ground water stoppage work, construction of underground piles and underground walls, etc. The cement-based solidification material is injected, and the slurry is collected as slurry. The latter ready-mixed concrete waste mud is a slurry-like waste mud that is collected when washing ready-mixed concrete transport vehicles, pump cars, machinery and the like. In many cases, these are in a shab-shab state having a solid content of less than 10%, and include unhardened cement, and further include aggregates such as earth and sand derived from the improved ground, sand and gravel.

First, in the treatment method of the present invention, this waste sludge having a low solid content is converted into a waste water by using a dewatering equipment usually used for dewatering such waste sludge or sludge, such as a belt press or a filter press. It is dehydrated to make a dehydrated cake having a water content of about 50 to 75% (solids concentration 25 to 50%). If the amount of waste sludge is small, it can be transported to a waste sludge treatment facility as it is and dewatered there. It is preferable to transport to a facility. Some waste sludge has a water content close to that of the dewatered cake, and the treatment method of the present invention can be applied to such waste sludge as it is.

Next, in the treatment method of the present invention, the water-containing cake is forcibly pulverized and dried to obtain a dry powder having a water content of 12% or less. The forced crushing and drying is an operation in which hot air is blown while applying a mechanical crushing force to a supplied material to simultaneously perform crushing and drying, and is a kind of flash drying method.

The equipment used for forced crushing and drying includes:
Arm-type impact crush dryer, hammer impact crush dryer,
Although there is a chain-type impact crush dryer, a chain-type impact crush dryer is particularly preferable in terms of drying efficiency and equipment maintenance. The chain-type impact crushing and drying machine is composed of a vertical cylindrical main body, a vertical shaft having a plurality of link chains incorporated therein, a driving device for rotating the same, and an auxiliary device.

[0017] The mechanism of the chain-type impact crushing and drying machine is such that the dewatered cake put into the inlet at the top of the dryer by the feeder is broken up by a chain that rotates at high speed around a vertical axis, becomes fine, and is dried by hot air. The particles are guided to a drying tube at a speed higher than the scattering speed of the particles, where the particles lose water and are collected by a cyclone separator. The dried powder is carried out of the cyclone separator, and a part of the dried powder may be circulated to the drying tube if necessary. The moisture content of the dried powder can be adjusted by setting the temperature of a thermometer provided at the cyclone separator inlet. If necessary, a suction fan or the like may be provided below the cyclone separator, and the inside of the dryer may be depressurized, thereby drying it under reduced pressure.

For the hot air supplied to the dryer, a dedicated hot air generator may be installed, or if there is a waste combustion furnace nearby, the waste heat may be used. Hot air temperature is usually 1
It is about 20-600 ° C, and the air volume depends on the water content of the dewatered cake, but 100-300m per ton of dewatered cake
^{About 3} is sufficient. When the above-mentioned chain-type impact crusher / dryer is used, about 30 kg of the dewatered cake can be treated with 1 liter of fuel (in the case of kerosene), and the efficiency is extremely high.

The hydraulically dried powder of the present invention (hereinafter sometimes abbreviated as dry powder) which has been forcedly pulverized and dried has a moisture content of 12%.
Or less, preferably 10% or less. In addition,
The water content in the present invention refers to the water content that evaporates when the temperature is maintained at 105 ° C. If the moisture content of the dried powder exceeds 12%, the hydration reaction of the uncured cement in the dried powder proceeds, and the storage stability is undesirably reduced. Increasing the temperature and air volume of the hot air and increasing the circulation rate of the dried powder can lower the moisture content of the dried powder to 1% or less, but increases the drying cost and decreases the productivity of the processing equipment. Therefore, the water content is preferably about 5%.

The hydraulically dried powder of the present invention contains at least 20% of unhardened cement, and at least 50% depending on the source. And it turned out that a dry powder can be hydrated similarly to a cement, and there exists some dry powder which expresses the strength near cement. The method of using the dry powder of the present invention is
This is used as a cement substitute or a cement admixture.

In order to use the dry powder as a substitute for cement, a mortar using dry powder instead of cement is prepared, and a strength test specified in JIS is performed on the mortar to measure the strength. As a result, the dry powder exhibiting a strength close to that of cement can be replaced with all of the cement.
In addition, even a dry powder having a lower strength than that of cement can be replaced with all of the cement in applications that do not require much strength, such as soil improvement materials and cement blocks.

As another method of using the dry powder, there is a so-called cement admixture in which a part of the cement is replaced with the cement. That is, in the preparation of cement milk, cement mortar and cement concrete, the amount of cement can be reduced by replacing a part of the cement with the dry powder. For example, you may mix | blend with a household cement preparation, a cement mortar for advisors, etc. Also,
In the manufacturing process of various cement secondary products such as cement blocks, cement treads, cement gutters, etc., a dry powder can be mixed with ordinary cement. Further, when the dry powder is mixed, fine powder, sand and the like other than the cement component contained in the dry powder can be used as an aggregate, so that the amount of the aggregate can be reduced.

Other uses of the dry powder of the present invention include slime generated in ground improvement work, cement waste mud generated in a ready-mixed concrete plant, sewage sludge generated in a sewage treatment plant, and various types of plants. It can be used as a moisture control hardening material for solidifying hydrated waste sludge such as hydrated sludge and reusing them. These water-containing waste muds are made into a dewatered cake having a water content of about 50% by a dehydrator such as a belt press, and an equal amount of dry powder is mixed with the dewatered cake to have a water content of about 25%. Using a drum-type granulator, a high-speed granulator, or the like, it is possible to granulate into granules having a diameter of several mm. When this is cured, the uncured cement component derived from the dry powder hardens, and a granulated product having high crushing strength is obtained.

The granulated material obtained from the water-containing waste mud and the dried powder in this way can be effectively used as a backfill material for burial works of water and sewage pipes, subway works, tunnel works and the like.
In recent years, in the method of discharging pore water in the ground, which has attracted attention as a measure against liquefaction, for example, in the gravel drain method, crushed stone is used as an insertion material, but this granulated material can be used instead of crushed stone. .

[0025]

Hereinafter, the present invention will be described with reference to Examples.
The present invention is not limited by these.

Example 1 A slime having a water content of 90% or more collected at a ground improvement construction site by a high-pressure injection injection method was dewatered by a belt press dewatering device to obtain a dewatered cake having a water content of about 50%. Next, a dry powder was prepared from the dehydrated cake by a forced crushing and drying apparatus. As the forced crushing and drying apparatus, an FM type chain impact crushing and drying machine (trade name: KUDAKERA) 100D manufactured by Fujimoto Polcon Co., Ltd. was used. The dewatered cake is supplied to this raw material charging device at 500 kg / hr, hot air of 650 ° C. is blown at 80 m ³ / hr from the hot air blowing port, and the drying tube outlet is operated to maintain the temperature at 110 ° C. A dry powder was obtained at 270 Kg / hr. The resulting dried powder had a water content of 7.5%.

Next, using the dried powder, ordinary Portland cement and standard sand, various mortars were prepared in the proportions shown in Table 1, and these mortars were subjected to JIS R52.
A mortar strength test was performed on the basis of No. 01, and the compressive strength (age 7 days) was measured. Table 1 shows the mixing ratio of the mortar and the results of the strength test. In Table 1, the value in parentheses in the column of compressive strength indicates the strength ratio when the cement is taken as 100.

[0028] The dried powder is JIS R5
The heat of hydration was measured based on 203. The flow value of the mortar was measured by changing the mixing water amount with respect to the dry powder, and the amount of water was determined so as to be substantially close to the cement flow value specified by JIS. It was 575 parts by weight (36.5%). When the heat of hydration of this mortar was measured, it was 31 at the age of 7 days.
It was 8 J / g.

[0029]

[Table 1]

Example 2 A mortar for a cement block was prepared by using the dry powder or the ordinary Portland cement of Example 1 and crushed sand and fine sand as aggregates in the mixing ratio shown in Table 2. The mortar was subjected to a strength test of the mortar according to JIS R5201, and the bending strength (7 and 28 days of material age) was measured. Table 2 shows the mixing ratio of the mortar and the results of the strength test.
Listed in In Table 2, the lower column of water in the mixing ratio indicates the water-cement ratio (W / C), and the lower column of flexural strength indicates 10% of cement.
It represents the intensity ratio when it is set to 0.

[0031]

[Table 2]

Example 3 100 parts by weight of the dewatered cake of Example 1 having a water content of 50%
A mixture obtained by mixing 40 parts by weight of the dry powder of Example 1 was supplied to a high-speed granulator at 300 kg / hr to granulate, and the granulated product was cured for 7 days and solidified. The obtained granulated product has a coarse particle ratio of 3.36, a specific gravity of surface dry of 2.13, and a specific gravity of absolute dry of 1.7.
7. Water absorption was 20.2%.

Next, various mortars were prepared in the proportions shown in Table 3 using ordinary Portland cement as cement and this granulated material (artificial sand) or standard sand as aggregate, and these mortars were based on JIS R5201. A mortar strength test was performed to measure the compressive strength (age 7 days). Table 3 shows the proportions of the mortar and the results of the strength test. In Table 3, () in the column of the compressive strength indicates the strength ratio when the standard sand is set to 100.

[0034]

[Table 3]

[0035]

According to the present invention, the cement-containing waste mud can be recovered as a hydraulically-dried powder by forcibly pulverizing and drying it, and this hydraulically-dried powder can be reused as a cement substitute or a cement admixture. It can be used, and the hydraulically dried powder can be used for the treatment of hydrated sludge. Further, the processing cost is low and the practicality is extremely high.

Claims (6)

[Claims] 1. A method for treating cement-containing waste mud, comprising forcibly pulverizing and drying uncured cement-containing waste mud or a dewatered cake thereof. 2. The method for treating cement-containing waste mud according to claim 1, wherein the forced crushing and drying is performed by a chain type impact crushing and drying machine. 3. A hydraulically dried powder having a moisture content of 12% or less and an uncured cement of 20% or more, obtained by forcibly pulverizing and drying a dewatered cake of uncured cement-containing waste mud. 4. A cement substitute comprising the hydraulically-dried powder according to claim 3. 5. A cement admixture comprising the hydraulically-dried powder according to claim 3. 6. A method for solidifying hydrated waste mud, comprising mixing the hydrated waste mud with the hydraulically-dried powder according to claim 3 and granulating the resulting mixture to solidify the granulated material.