JPH031254B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method and an apparatus for recycling the washing residue of ready-mixed concrete generated when a transport vehicle, a plant mixer, etc. are washed with ready-mixed concrete. [Prior Art] This type of fresh concrete washing residue includes gravel, sand, and sludge. Conventionally, it has been known that washing water for fresh concrete contains several percent of sludge, which is recovered and used as concrete mixing water (for example, Kiyota Okada, "Concrete Engineering Handbook" (1981, 11, 20), Asakura Shoten,
p128). However, although some of the washed concrete residue is used by mixing it with new fresh concrete, the majority of it is currently thrown away. Generally, when cement interacts with water, the cement hydrate that forms around cement particles hardens itself over time and becomes water-impermeable. Even if you mix it with fresh concrete, considering the strength of hardened concrete, it does not change the water/cement ratio and you will only get the same effect as mixing aggregate such as gravel or sand. It is. [Problems to be Solved by the Invention] For this reason, there is currently little use for the washing residue of ready-mixed concrete, and if the dumping site is selected incorrectly, there is a possibility that it may cause pollution as industrial waste. The purpose of the present invention is to finely pulverize the sludge contained in the washing residue of ready-mixed concrete and effectively utilize the unhydrated cement in the sludge, thereby not causing pollution problems and reducing the amount of new cement used. It is an object of the present invention to provide a method and apparatus for recycling the washing residue of ready-mixed concrete that can be reduced and contribute to resource saving. [Means for Solving the Problems] The configuration of the present invention for achieving the above object is as follows.
Description will be given based on the drawings and FIG. 2 corresponding to the embodiment. As shown in FIG. 1, the method for recycling fresh concrete washing residue of the present invention includes a classification step 1 of wet-classifying fresh concrete washing residue A to extract sludge water from which gravel and sand have been removed; A concentration step 2 of concentrating the sludge water, a dehydration step 3 of dehydrating the concentrated sludge water by squeezing to obtain a sludge cake, a drying step 4 of drying the sludge cake, and a vibratory pulverization of the dried sludge cake with a vibrating ball mill. The present invention is characterized in that it includes a pulverization step 5 of obtaining fine sludge powder DH containing cement components in which unhydrated cement appears on the surface. As shown in FIG. 2, the apparatus for recycling fresh concrete washing residue of the present invention includes a classifier 10 for wet-classifying fresh concrete washing residue to extract sludge water from which gravel and sand have been removed; A shaker 20 for forcibly sedimenting the sludge contained in the sludge, a dehydrator 30 for squeezing the sludge water with a high sludge concentration obtained by this sedimentation, a dryer 40 for drying the dehydrated sludge cake, and a vibratory pulverizer for the dried sludge cake. The present invention is characterized in that it is equipped with a vibrating ball mill 50 for obtaining fine sludge powder containing cement components with unhydrated cement appearing on the surface. [Function] When cement interacts with water, cement particles form a cement hydrate around the cement particles as shown in FIG. 3, and an unhydrated cement encapsulated by the cement hydrate. This study focused on a well-known phenomenon (Special Publication No. 44-14833) that caused the sludge consisting of cement hydrate and non-cement hydrate contained in the washing residue of fresh concrete to be mixed with other gravel or sand. After drying this sludge, it is vibrated and pulverized in a vibrating ball mill to obtain fine sludge powder DH in which unhydrated cement appears on the surface as shown in Figure 4. , this sludge fine powder DH is used to obtain a new function similar to that of cement, and to regenerate the washing residue of ready-mixed concrete. Furthermore, as shown by the broken line in Figure 1, if the sludge cake is pulverized and then dry classified, it is possible to separate the two, as the cement hydrate has a lower specific gravity than the unhydrated cement. It is possible to obtain fine sludge powder DH that contains a large amount of unhydrated cement and is even more similar to new cement. [Effects of the Invention] As described above, according to the present invention, cement surrounded by cement hydrate is produced by dry vibratory pulverization of sludge in the washing residue of fresh concrete using a vibrating ball mill. Unhydrated substances can be made to appear on the surface of the sludge powder. This makes it possible to extract unhydrated cement from the washing residue of ready-mixed concrete, which conventionally had little use and had no choice but to be dumped, eliminating the need to dispose of it as industrial waste and solving the pollution problem. At the same time, cement resources can be used efficiently. In particular, since the vibratory ball mill produces finer cement particles than ordinary cement, the mortar or concrete using the sludge fine powder of the present invention has better plasticity (viscosity) than conventional ones and resists separation of the material. It has excellent properties and has advantages in construction. [Example] Next, an example of the present invention will be described in detail in the order of steps based on the drawings. <Classification of sludge water> The fresh concrete wash water 14 generated when washing the fresh concrete transport vehicle or the fresh concrete mixer vehicle 12 is supplied to the classifier 10 of the spiral classifier, and it is divided into gravel G, gravel G, etc. according to the particle size. Wet classification into sand S and sludge water H. Gravel G and sand S are stored in a tank 16. The sludge water H is a suspension in which water is used as a dispersion medium and, as shown in FIG. 3, sludge in which unhydrated cement is encapsulated by hydrated cement is used as a dispersed phase. <Concentration of sludge water> Collect the classified sludge water H into the collection tank 21,
A pump 22 provided at the bottom of the recovery tank 21 sends the sludge to a sludge tank 24 via a cyclone 23.
The remaining gravel G and sand S are separated by the cyclone 23 and returned to the classifier 10. The sludge water H at the bottom of the sludge tank 24 is sent to the sludge tanker 20 by a pump 25 while stirring the sludge water H at the bottom of the sludge tank 24 with a stirrer 24a at a low speed to prevent the sludge water H from hardening.
A liquid level switch 24b is turned on when the sludge water tank 24 reaches a predetermined water level, and drives the pump 25 to rotate. In the shaker 20, the sludge content is forcibly settled by the stirrer 20a, and the supernatant water with a low sludge concentration is returned to the sludge water tank 24 through the pipe 27, while the sludge water H with a sludge concentration of about 10 to 20% is sent to the next tank. Send to dehydrator 30. If the concentration of the sludge sent to the dehydrator 30 is less than 10%, the working efficiency of the next dewatering step will deteriorate, and if it is more than 20%, the residence time in the sludge 20 will be prolonged, which is not preferable. In this example the sludge concentration is 15%. <Dehydration of sludge water> A predetermined amount of the sludge water concentrated by the sludge filter 20 is collected and supplied to the dehydrator 30, where it is compressed at a low speed and dehydrated. In this example, the dehydrator 30 is
The number of rooms is 2, the excess area is ^2.48m2 , and the room volume is 50.
Using a filter press with a driving pressure of 4 kg.
Inject 50 ml of sludge water into the chamber at f/cm ² as a single treatment amount. It takes about 20 minutes per cycle to squeeze out the water from the filter and dehydrate it, resulting in a water content of 30.
~40% sludge cake SC is obtained. <Drying of Sludge Cake> After naturally drying this sludge cake SC to a moisture content of 10%, it is force-dried using a dryer 40 at a constant temperature for a long period of time. Here, in order to increase drying efficiency, it is preferable that the sludge cake SC be coarsely pulverized before drying. In this example, Slutji Cake
After naturally drying the SC in the sludge cake storage area,
It is continuously charged into a hopper 41 and supplied to a crusher 43 via a conveyor 42. Kratsusha 43
After coarsely pulverizing the sludge into a sludge mass M with a diameter of about 4 cm,
The sludge mass M is supplied to the dryer 40 of the rotary kiln via the hopper 44 → conveyor 45 → hopper 46 → conveyor 47. Here, the sludge mass M is treated at high temperature and dried to an absolutely dry state. <Fine Grinding of Sludge Cake> After coarsely grinding the dried sludge mass M, it is vibrated into fine powder using a vibrating ball mill 50. In this example, after the dried sludge mass M is temporarily stored in a tank 51, it is continuously supplied to a vibrating ball mill 50 via a conveyor 52, where it is vibrated and pulverized to obtain fine sludge powder. This vibratory ball mill 50 consists of a first stage mill 50a and a second stage mill 50b. The obtained sludge powder is sent to a plant or a sludge powder tank 55 by a screw conveyor 53 and a bucket conveyor 54. As shown in FIG. 4, this fine sludge powder becomes fine sludge powder DH in which cement hydrates are exfoliated and unhydrated cement appears on the surface. By adding this sludge powder DH to new cement and adding aggregate such as gravel or sand to create ready-mixed concrete, the amount of new cement can be reduced. [Test Examples, Comparative Examples] Next, in order to confirm the effects of the present invention, a sludge cake SC was dehydrated using the dehydrator 30 and air-dried in a sludge cake storage area, and the sludge cake SC was collected using a mallet or the like to give a diameter of 4 cm. After making the sludge mass M into a sludge mass M of about
The material was dried at a temperature of about 30 hours to an absolutely dry state, and then pulverized by vibration using a vibrating ball mill.
This vibrating ball mill has a maximum excitation force of 2000Kg, 19.2
Hz vibro mill, the first stage mill contains a total of 36 kg of cylindrical steel bars with a diameter of approximately 23 mm, a length of approximately 580 mm, and a grain weight of approximately 1.7 kg, and the second stage mill contains a total of 36 kg of cylindrical steel bars with a diameter of approximately 12 kg.
Contains a total of 36 kg of steel balls with a diameter of 6.9 g. Sludge mass M of 30 kg per hour was continuously supplied to this vibrating ball mill to obtain fine sludge powder. A concrete strength test was conducted using the sludge fine powder DH obtained by the above method together with cement. First, considering sludge fine powder DH as aggregate,
The strength of concrete mixed with sludge powder DH was compared with that of concrete not mixed with it (Test Example 1~
3. Comparative Examples 1 to 3). These results are shown in the table. Test example 1 Portland cement C192Kg, sludge fine powder
DH57Kg, sand S781Kg, gravel G1046Kg, water W165Kg
Mix uniformly with water/cement ratio (W/C ratio) 86
% concrete was prepared. When this concrete was placed in a designated formwork and its compressive strength was examined, it was found that
125Kgf/cm ² at 7 days old, 205Kgf/cm ² at 28 days old
It was hot. Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 8 cm. Comparative Example 1 Compared to Test Example 1, the same amount of the same materials as Test Example 1 were taken without adding sludge fine powder DH, and only sand S was increased from 781 Kg to 848 Kg, and these were uniformly kneaded. Concrete with the same W/C ratio as Test Example 1 was prepared. When this concrete was placed in a designated formwork and the compressive strength was examined, it was found to be 83 at the age of 7 days.
Kgf/cm ² , and it was 151 Kgf/cm ² at the age of 28 days. Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 8 cm. Test example 1 using the sludge fine powder DH of the present invention
It was found from Comparative Example 1 that the compressive strength increased by 1.51 times when the material was aged 7 days and by 1.36 times when the material was aged 28 days. Test example 2 Portland cement C267Kg, sludge fine powder
80 kg of DH, 784 kg of sand S, and 857 kg of gravel G are uniformly mixed with 203 kg of water to obtain a water/cement ratio (W/C ratio) of 76%.
concrete was prepared. This concrete was put into a predetermined formwork and the compressive strength was examined, and it was found to be 187 Kgf/cm ² at 7 days old and 284 Kgf/cm ² at 28 days old. Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 21 cm. Comparative Example 2 Compared to Test Example 2, the same amount of the same material as Test Example 2 was taken without adding sludge fine powder DH, and only sand S was increased from 784 Kg to 879 Kg, and these were uniformly kneaded. Concrete with the same W/C ratio as Test Example 2 was prepared. When this concrete was placed in a designated formwork and the compressive strength was examined, it was found that the age of the concrete was 7 days.
It was 117Kgf/cm ² , and 195Kgf/cm ² at 28 days old.
Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 21 cm. As a result, the compressive strength of Test Example 2 using the sludge fine powder DH of the present invention was 1.60 times that of Comparative Example 2 at the age of 7 days, and the compressive strength was 1.60 times higher at the age of 28 days.
It turns out that it increases by 1.46 times per day. Test example 3 Portland cement C250Kg, sludge fine powder
DH75Kg, sand S648Kg, gravel G1114Kg, water W165Kg
Mix uniformly with water/cement ratio (W/C ratio) 66
% concrete was prepared. When this concrete was placed in a designated formwork and its compressive strength was examined, it was found that
264Kgf/cm ² at 7 days old, 383Kgf/cm ² at 28 days old
It was hot. Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 8 cm. Comparative Example 3 Compared to Test Example 3, the same amount of the same materials as Test Example 3 were taken without adding sludge fine powder DH, and only sand S was increased from 648 Kg to 735 Kg, and these were uniformly kneaded. Concrete with the same W/C ratio as Test Example 3 was prepared. When this concrete was placed in a designated formwork and the compressive strength was examined, it was found that the age of the concrete was 7 days.
It was 167Kgf/cm ² , and 259Kgf/cm ² at 28 days old.
Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 8 cm. As a result, in Test Example 3 using the sludge fine powder DH of the present invention, the compressive strength was 1.58 times that of Comparative Example 3 at the age of 7 days, and the compressive strength was 1.58 times higher at the age of 28 days.
It turns out that it increases by 1.48 times per day. Next, considering the sludge fine powder DH as a new cement C, the strengths of concrete mixed with the sludge fine powder DH and concrete not mixed were compared (Test Examples 4 to 6, Comparative Examples 4 to 6). These results are shown in the table. Test example 4 Portland cement C236Kg, sludge fine powder
DH70Kg, sand S853Kg, gravel G824Kg are uniformly mixed with water W203Kg, water/cement ratio (W/C+DH
ratio) 66% concrete was prepared. When this concrete was put into a specified formwork and the compressive strength was examined, it was 142Kgf/cm ² at 7 days old and 226Kg at 28 days old.
It was f/cm ² . Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 21 cm. Comparative Example 4 Compared to Test Example 4, cement C was increased by the amount of sludge fine powder DH to 308 kg,
In addition, the sand S was increased from 853Kg to 879Kg, and the others were Test Example 4.
The same amount of the same material as in Test Example 4 was taken and mixed uniformly to prepare concrete with the same W/C ratio of 66% as in Test Example 4. When this concrete was placed in a specified formwork and the compressive strength was examined, it was found that the concrete had a compressive strength of 170
Kgf/cm ² , and it was 273 Kgf/cm ² at the age of 28 days. Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 21 cm. Test Example 4, in which the sludge fine powder DH of the present invention was considered as cement, had a compressive strength at 7 days of age compared to Comparative Example 4.
It was found that the increase was 0.84 times, and 0.83 times when the material was aged 28 days. Test example 5 Portland cement C217Kg, sludge fine powder
DH65Kg, sand S717Kg, gravel G1083Kg, water W165Kg
Mix uniformly with water/cement ratio (W/C+DH
(ratio) 58.5% concrete was prepared. When this concrete was put into a specified formwork and the compressive strength was examined, it was 199 kgf/cm ² at 7 days old and 300 kgf/cm 2 at 28 days old.
It was Kgf/ ^cm2 . Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 8 cm. Comparative Example 5 Compared to Test Example 5, cement C was increased by the amount of sludge fine powder DH to 282 kg,
In addition, the sand S was increased from 717Kg to 740Kg, and the other conditions were Test Example 5.
The same amount of the same material as in Test Example 5 was taken and mixed uniformly to prepare concrete with the same W/C ratio of 58.5% as in Test Example 5. When this concrete was placed in a designated formwork and the compressive strength was examined, it was found that the age of the concrete was 7 days.
It was 238Kgf/cm ² , and 350Kgf/cm ² at 28 days old.
Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 8 cm. Test Example 5, in which the sludge fine powder DH of the present invention was considered as cement, had a compressive strength at 7 days of age compared to Comparative Example 5.
It was found that it becomes 0.84 times, and 0.86 times when the wood age is 28 days. Test example 6 Portland cement C308Kg, sludge fine powder
DH92Kg, sand S714Kg, gravel G881Kg are uniformly mixed with water W203Kg, water/cement ratio (W/C+DH
(ratio) 50.8% concrete was prepared. When this concrete was placed in a specified formwork and the compressive strength was examined, it was 251Kgf/cm ² at 7 days old and 364 at 28 days old.
It was Kgf/ ^cm2 . Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 21 cm. Comparative Example 6 Compared to Test Example 6, cement C was increased by the amount of sludge fine powder DH to 400 kg,
In addition, the sand S was increased from 714Kg to 745Kg, and the others were Test Example 6.
The same amount of the same material was taken and mixed uniformly to prepare concrete with the same W/C ratio of 50.8% as in Test Example 6. When this concrete was placed in a designated formwork and the compressive strength was examined, it was found that the age of the concrete was 7 days.
It was 301Kgf/cm ² and 437Kgf/cm ² at 28 days old.
Further, when a slump test was conducted according to JIS A 1101, the slump value Sl was 21 cm. Test Example 6, in which the sludge fine powder DH of the present invention was considered as cement, had a compressive strength at 7 days of age compared to Comparative Example 6.
0.83 times, and 0.83 times when the wood age is 28 days. In addition, through Test Examples 1 to 6, it was observed that in all cases, the concrete was superior in plasticity (viscosity) and had a high property of resisting material separation compared to Comparative Examples 1 to 6, which did not use sludge fine powder DH as fresh concrete. The construction advantages were discovered.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the regeneration method of the present invention. FIG. 2 is a configuration diagram of a playback device according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of cement particles in cement mortar or concrete. Figure 4 is the third
FIG. 3 is a cross-sectional view when the cement particles shown in the figure are regenerated by the regeneration method of the present invention. 10: Classifier, 20: Shitsukuna, 30: Dehydrator, 40: Dryer, 50: Vibrating ball mill.

Claims (1)

[Scope of Claims] 1. A classification step for extracting sludge water from which gravel and sand have been removed by wet-classifying the washing residue of fresh concrete, a concentration step for concentrating this sludge water, and dehydration of the concentrated sludge water by compression. a drying step of drying the sludge cake; and a vibratory pulverization of the dried sludge cake in a vibrating ball mill to obtain a fine sludge powder containing cement components with unhydrated cement appearing on the surface. A method for recycling fresh concrete washing residue, the method comprising: a crushing step. 2. A classifier that extracts sludge water from which gravel and sand have been removed by wet-classifying the washing residue of fresh concrete, a sludge that forcibly settles the sludge contained in this sludge water, and a sludge water with a high sludge concentration obtained by this sedimentation. A dryer that dries the dehydrated sludge cake; and a vibrating ball mill that vibrates and pulverizes the dried sludge cake to obtain fine sludge powder containing cement components with unhydrated cement appearing on the surface. A device for recycling fresh concrete washing residue, which is characterized by the following: