JP6168711B2 - Concrete sludge fine powder recovery method and concrete sludge fine powder - Google Patents

Description

  The present invention relates to a recovery method for recovering cement content from residual concrete or return concrete, or washing waste water generated from a ready-mixed concrete factory, and the like, and a concrete sludge fine powder.

  Concrete made of cement, sand, gravel, mortar made of cement and sand, etc. are manufactured by a ready-mixed concrete factory and transported to a concrete placement site by a mixer truck. The ready mixed concrete factory is equipped with a mixer for mixing concrete as is well known in the art. A mixer truck can be placed under the concrete mixing mixer. After completion of the kneading, when the gate of the concrete kneading mixer is opened, the concrete is put into the drum of the delivered mixer truck through the hopper. In substantially the same way, mortar is also produced and fed into the mixer drum via a hopper.

  A mixer truck loaded with concrete, mortar, etc. heads for the installation site. Then, when the drum is rotated in reverse at the placement site, concrete, mortar, etc. are unloaded. After unloading, the mortar and the like adhering to the chute and the discharge vane are washed, and the washed waste water after washing is accumulated in the drum of the mixer truck. Such washing wastewater contains cement components and thus falls under industrial waste and is not allowed to be disposed of directly in vacant land, roads, rivers, etc. near the unloading site. Therefore, the cleaning wastewater is transported to a predetermined cleaning wastewater treatment facility by the mixer truck. In general, the cleaning wastewater treatment facility is installed in a ready-mixed concrete factory, and cleaning wastewater generated by cleaning equipment such as mixers in the factory is treated. The cleaning wastewater transported by the mixer truck is also treated with this cleaning wastewater. Processed at a processing facility. The remaining concrete and return concrete are treated in the same way. That is, when residual concrete and return concrete are present in the drum, predetermined water is added to the drum to form a slurry, which is transported to a cleaning wastewater treatment facility where it is processed.

  Washing wastewater as described above, residual concrete made into a slurry, return concrete, etc. can be referred to as a slurry-like object to be processed, but the slurry-like object to be processed contains a large amount of sludge composed of cement in addition to gravel and sand. include. In recent years, various patent documents have proposed methods for recovering cement as a fine powder from such a slurry-like workpiece as described below.

JP 2002-254099 A Japanese Patent No. 4447276 JP 2014-88278 A

The concrete sludge fine powder recovery method described in Patent Document 1 includes the following steps (A1) to (A7). That is,
(A1) A fine sand removing step for obtaining recovered water from which fine sand contained in washing wastewater and treated wastewater is removed so that the sand content is 10% by mass or less;
(A2) a coagulation precipitation step of adding an inorganic flocculant to the recovered water obtained by the step and separating and precipitating into supernatant water and sludge water;
(A3) a dehydration step of dewatering the sludge water separated in the step to produce a dehydrated cake;
(A4) Crushing treatment step of crushing the dehydrated cake obtained in this step before curing and plane rolling to a thickness of 10 to 15 mm;
(A5) a drying step of drying the dehydrated cake crushed in the step so that the water content is 50 to 60% by mass and the maximum particle size is 20 mm or less;
(A6) a fine pulverization step for producing rounded fine particles by finely pulverizing the dry sludge obtained in the step with a pulverizer using wind power;
(A7) It consists of the collection process which collects the microparticles | fine-particles manufactured at this process.

On the other hand, the concrete sludge fine powder recovery method described in Patent Document 2 includes the following steps (B1) to (B4). That is,
(B1) A separation step of separating sludge and sand in the slurry-like object to obtain sludge water having a sand content of 10% by mass or less;
(B2) a fine sand content removing step of separating and removing fine sand content from the sludge water obtained by the separation step by a wet cyclone;
(B3) A dehydrated cake production process for obtaining a dehydrated cake having a moisture content of 25 to 45 mass% by subjecting the concentrated sludge water obtained in the fine sand content removing process to a filter press, and (B4) a dehydrated cake obtained by the dehydrated cake production process. Is continuously supplied from one end of a horizontal rotary drum to a fixed amount, and the supplied dewatered cake is scooped up to a predetermined height by a lifter provided on its inner peripheral wall and dropped, and its internal space Crushing with a crushing stirring blade provided in the above, at this time hot air is blown from the one end, crushing and drying of the dewatered cake is carried out substantially simultaneously, and concrete sludge is continuously applied from the other end It consists of crushing and drying process to obtain fine powder.

  In any of the collection methods, there is some process difference until gravel and sand are separated from the slurry-like object to be reduced to a predetermined sand content and dehydrated to obtain a dehydrated cake. Is also substantially common. Further, in the other concrete sludge fine powder collection methods different from the collection methods described in Patent Documents 1 and 2, substantially the same steps are performed until a dehydrated cake is obtained. However, in the recovery method described in Patent Document 1, the dewatered cake is crushed and then dried, and then finely pulverized using wind power to collect finely pulverized concrete sludge fine powder. In the recovery method described in Patent Document 2, the dewatered cake is continuously supplied to a horizontal rotating drum provided with a crushing stirring blade and hot air is blown into the crushing and drying substantially simultaneously. It is carried out to obtain concrete sludge fine powder, and the process is different. Due to such differences in drying and pulverization processes, the properties of the obtained concrete sludge fine powder are slightly different as described in the respective documents. Also in other concrete sludge fine powder recovery methods, the dewatered cake should be dried and pulverized in slightly different steps to obtain concrete sludge fine powder, and the properties should be slightly different depending on the difference in the steps. However, even if the concrete sludge fine powder collected by any method can be used for common purposes, for example, as a soft ground improvement material, or as described in Patent Document 3 It can be used as a material for a water-curable cured body. Furthermore, as a substitute for cement, it can be used as a material for hardened cement bodies such as concrete and mortar.

  The concrete sludge fine powder can be recovered from the slurry-like object to be processed by the recovery methods described in Patent Documents 1 and 2, or by other recovery methods. The recovered concrete sludge fine powder can be used for various purposes. However, there is room for improvement when used as a material for hardened cement as a substitute for cement. Specifically, when concrete sludge fine powder is used as a substitute for cement, a relatively large amount of water reducing agent is required. Since a large amount of water reducing agent is required, there is a problem in that the cost of the cement cured body is increased.

  Therefore, the present invention requires less use of a water reducing agent when the concrete sludge fine powder is used as a material for a cement hardened body as a substitute for cement, and thus can provide a cement hardened body at a low cost. An object of the present invention is to provide a concrete sludge fine powder recovery method for obtaining such a concrete sludge fine powder, and a concrete sludge fine powder. Such a concrete sludge fine powder should have excellent properties with less viscosity than conventional concrete sludge fine powder even when used for other purposes.

The present invention collects concrete sludge fine powder mainly composed of cement from a slurry-like material to be treated such as residual concrete or return concrete to which predetermined water has been added, or washing waste water generated from a ready-mixed concrete factory. It is configured as a recovery method. The recovery method includes a separation step of removing gravel, sand, and fine sand from the slurry-like object to obtain sludge water, a dehydration step of dehydrating the sludge water to obtain a dehydrated cake, And a crushing / drying step of drying to obtain a concrete sludge fine powder. And a crushing process is provided in a crushing / drying process or as a subsequent process of the crushing / drying process so that the concrete sludge fine powder is crushed to a state where particles having a particle diameter of 200 μm or more are not substantially present. When carrying out the crushing and crushing process, the dehydrated cake is put into a predetermined drum, crushing and stirring blades provided in the drum are rotated to crush and hot air is supplied into the drum. Crushing and drying in parallel. When a pulverization process is performed as a post process, the pulverization process is performed by a pin mill, a jet mill, a ball mill, or a roller mill.

That is, in order to achieve the above object, the invention according to claim 1 is a slurry-like object to be treated such as residual concrete or return concrete to which predetermined water is added, or washing waste water generated from a ready mixed concrete factory. From the above, a recovery method for recovering fine powder of concrete sludge mainly containing cement, which is a separation method for removing gravel, sand and fine sand from the slurry-like material to obtain sludge water consists of a step, a dehydration step to obtain a dehydrated cake to dehydrate the sludge water, and crushing and drying of the dehydrated cake crushing and drying to obtain a concrete sludge powder, the crushing and drying step, the dehydrated cake Is put into a predetermined drum, and crushing and stirring blades provided in the drum are rotated and crushed and hot air is supplied into the drum. Crushing and drying to be performed in parallel concrete sludge powder particle size 200μm or more particles is configured as a method of recovering powder concrete sludge fines, characterized in that ground to the substantial absence.
The invention according to claim 2 is a concrete mainly composed of cement from a slurry-like object to be treated such as residual concrete or return concrete to which predetermined water is added, or washing waste water generated from a ready mixed concrete factory. A recovery method for recovering sludge fine powder, wherein the recovery method includes a separation step of removing gravel, sand and fine sand from the slurry-like object to obtain sludge water, and dehydrating the sludge water. A dehydration step for obtaining a dehydrated cake, a crushing and drying step for crushing and drying the dehydrated cake to obtain a fine powder of concrete sludge, and a concrete sludge fine powder obtained in the crushing and drying step for pin mill, jet mill, ball mill, or I and a grinding step of the state where substantially no particle size 200μm or more particles by crushing by the roller mill It is configured as a method of recovering powder concrete sludge fines, wherein.
According to a third aspect of the present invention, in the recovery method according to the second aspect, in the crushing / drying step, the dehydrated cake is charged into a predetermined drum, and a crushing stirring blade provided in the drum is rotated. The method is configured as a concrete sludge fine powder recovery method in which hot air is supplied into the drum and the crushing and drying are substantially performed in parallel.

As described above, according to the present invention, the main component is cement from a slurry-like workpiece such as residual concrete or return concrete to which predetermined water has been added, or cleaning wastewater generated from a ready-mixed concrete factory. A recovery method for recovering fine powder of concrete sludge. The recovery method includes a separation step of removing gravel, sand and fine sand from a slurry-like object to obtain sludge water, and dewatering the sludge water by dehydration. It comprises a dehydration step for obtaining a cake and a crushing / drying step for crushing and drying the dehydrated cake to obtain a concrete sludge fine powder. In the crushing / drying step, the dehydrated cake is put into a predetermined drum, and crushing stirring blades provided in the drum are rotated to crush and hot air is supplied into the drum to substantially crush and dry. Are carried out in parallel, and the concrete sludge fine powder is pulverized into a state in which particles having a particle size of 200 μm or more are substantially absent. That is, the concrete sludge fine powder obtained by this recovery method is guaranteed to have a particle size of less than 200 μm. As clarified by the experiment described in the “DETAILED DESCRIPTION OF THE INVENTION”, a concrete sludge fine powder substantially free of particles having a particle size of 200 μm or more is used as a cement substitute material as a substitute for cement. When used, the viscosity is small and the amount of water reducing agent used is small. That is, the effect that a hardened cement body can be provided at low cost is obtained. Of course, since the viscosity is so small, a concrete sludge fine powder substantially free of particles having a particle size of 200 μm or more can be used as a soft ground improvement material, or water hardening as described in Patent Document 3. It should be easy to handle even if used as a material for a heat-resistant cured body. According to another invention, the recovery method includes the separation step, the dehydration step, the crushing / drying step, and the concrete sludge fine powder obtained in the crushing / drying step by pulverizing with a pin mill, jet mill, ball mill, or roller mill. It consists of a pulverizing step in which particles of 200 μm or more are substantially absent. Also according to this invention, the obtained concrete sludge fine powder is guaranteed to have a particle size of less than 200 μm, so that the same effect can be obtained.

It is a block diagram showing typically a recovery method of concrete sludge fine powder concerning an embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a part of collection apparatus of the concrete sludge fine powder which concerns on embodiment of this invention, and is a figure which shows typically the crushing and drying apparatus which crushes and grinds a dewatering cake, The (a) (b) is each horizontal type It is front sectional drawing which shows the rotary dryer of this, and a vertical crushing and drying apparatus. It is a graph which shows the particle size distribution of concrete sludge fine powder. It is a figure which shows typically the state by which the cement particle aggregated and kneaded with kneading water as a nucleus.

  An embodiment of the present invention will be described. The concrete sludge fine powder recovery method according to the present embodiment recovers the concrete content from a slurry-like workpiece such as washing waste water generated in a ready-mixed concrete factory, residual concrete / returned concrete in a slurry state, etc. Is the method. A recovery step according to the present embodiment for realizing the recovery method is shown in FIG.

  In the recovery step according to the present embodiment, first, a slurry-like workpiece is obtained. For example, the washing waste water S1 for washing the mixer or the like of the ready mixed concrete factory and the washing waste water S1 for washing the drum of the mixer truck are already in the form of a slurry, and thus can be handled as a slurry-like object. On the other hand, the remaining concrete / returned concrete S2 has a low fluidity and is difficult to process, so pretreatment is required. That is, a slurrying step S3 is performed in which predetermined water is added to the remaining concrete / return concrete S2 and stirred. As a result, the remaining concrete / returned concrete becomes a slurry. That is, a slurry-like workpiece is obtained.

  The slurry-like workpiece is first processed by a separation process. The separation step is a step of removing aggregates and the like from the slurry-like workpiece. In the present embodiment, the separation step includes an aggregate separation step S4 and a fine sand content removal step S5. The aggregate separation step S4 is performed by a plurality of vibrating sieves having different mesh sizes, and sequentially processes the slurry-like workpieces to separate aggregates such as gravel and sand. The collected aggregate is sent to a predetermined bin according to the particle size in order to be reused. The remaining sieve after the aggregate is separated is sludge water containing cement. The fine sand removal step S5 is performed by a wet cyclone in the present embodiment, and is a step of removing fine sand, that is, fine sand from sludge water. The sludge water from which the fine sand has been removed in the fine sand removal step S5 is processed in the next dewatering step S6. However, when the amount of cement contained in the sludge water is small, other residual concrete / returned concrete may be reused as water for slurrying in the slurrying step S3. If it does in this way, although a separation process will be repeated again, sludge water will concentrate a cement part. That is, concentrated sludge water is obtained. In any case, gravel, sand, and fine sand are removed from the sludge water or the concentrated sludge water so that the sand content is 10% by mass or less in the separation step, and sent to the next dehydration step S6.

  The dewatering step S6 is a step in which sludge water or concentrated sludge water is treated with a filter press and dehydrated to obtain a dehydrated cake. In the present embodiment, the moisture content of the dehydrated cake is set to 25 to 45% by mass.

  In the crushing / drying step S7, the dewatered cake is crushed and dried to obtain a concrete sludge fine powder. The crushing / drying step S7 can be performed by various apparatuses, but in the present embodiment, a rotary dryer RD shown in FIG. 2A is used. The rotary dryer RD is roughly configured from a rotating drum 1 that is laid down horizontally, into which a dehydrated cake is placed, and crushing and drying are performed simultaneously. The rotary drum 1 is provided with a plurality of lifters 5, 5,... On the inner peripheral surface so as to rotate integrally with the rotary drum 1, and the dewatered cake is scooped up to a predetermined height. Then it comes to fall. The rotating drum 1 is provided with a rotating shaft 7 that rotates at a high speed at a predetermined position, and the rotating shaft 7 is provided with a plurality of choppers, that is, crushing stirring blades 9, 9,. As a result, the dehydrated cake that is scooped up and dropped is crushed. At one end of the rotating drum 1 is provided an inlet 10 through which dehydrated cake is continuously charged, and a dryer 2 for supplying hot air into the drum. The dehydrated cake is dried by this hot air. An exhaust hood 12 is provided at the other end of the rotating drum 1. When the dewatered cake is crushed in the rotating drum 1 and dried, it becomes a concrete sludge fine powder, but the concrete sludge fine powder is continuously sent to the exhaust hood 12 together with hot air. Since the inside of the exhaust hood 12 is sufficiently wide, the speed of the gas sent from the rotary drum 1 to the exhaust hood 12 is sufficiently slow. Thereby, the concrete sludge fine powder settles on the bottom of the exhaust hood 12 by gravity. The settled concrete sludge fine powder is discharged from the discharge port 13 to the outside. The rotary dryer RD according to the present embodiment obtains concrete sludge fine powder from the dehydrated cake by carrying out crushing and drying substantially simultaneously. High-quality concrete sludge fine powder that is contained in a large amount can be obtained.

  In the collection step according to the present embodiment, the pulverization step S8 is finally performed. The pulverization step S8 uses a pin mill in the present embodiment, but may use a jet mill, a ball mill, or a roller mill. The concrete sludge fine powder is pulverized by the pulverization step S8. Thus, substantially no particles having a particle size of 250 μm or more are present, more preferably, substantially no particles having a particle size of 200 μm or more are present. This makes it possible to reduce the amount of water reducing agent used when the concrete sludge fine powder is used as a cement hardened material instead of cement.

An experiment was conducted to examine how the particle size of the concrete sludge fine powder changes in the pulverization step S8.
Experimental methods and results:
The remaining concrete / returned concrete is subjected to the slurry adding step S3, the aggregate separating step S4, the fine sand removing step S5, and the dewatering step S6 described above, and then crushed by the rotary dryer RD according to the present embodiment. -The drying process S7 was implemented and the concrete sludge fine powder was obtained. That is, in the crushing / drying step S7, the dehydrated cake was continuously supplied, and the concrete sludge fine powder was continuously obtained. With respect to the obtained concrete sludge fine powder, the particle size distribution of the particles, that is, the particle size distribution was examined, and a graph G1 in FIG. 3 was obtained. The particle size distribution was measured with a laser diffraction / scattering particle size distribution measuring instrument (product number: LMS-2000e) manufactured by Seishin Corporation. Next, a pulverization step S8 for pulverizing the concrete sludge fine powder with a pin mill was performed, and the particle size distribution of the pulverized concrete sludge fine powder was examined to obtain a graph G2 in FIG.

Evaluation of experimental results:
In the concrete sludge fine powder obtained by carrying out the crushing / drying step S7 by the rotary dryer RD composed of the horizontal rotary drum 1, particles having a particle diameter of 200 to 400 μm were observed at a certain frequency. In particular, particles having a particle size of 250 μm were contained at a frequency of 1%. As a result, in the graph G1 of the particle size distribution, a small bump having a vertex near the particle size of 250 μm was formed. When the pulverization step S8 for pulverizing such concrete sludge fine powder with a pin mill is performed, the concrete sludge fine powder is substantially free of particles having a particle size of 250 μm or more, or particles having a particle size of 200 μm or more. Was confirmed.

Discussion:
The reason why particles having a particle size of 250 μm or more remained in the concrete sludge fine powder obtained in the crushing / drying step S7 at a predetermined frequency and the particles having a particle size of 250 μm or more in the concrete sludge fine powder pulverized in the pulverization step S8. Consider the reason why it no longer exists. A cement paste obtained by kneading cement and water, or a concrete obtained by kneading cement, water and aggregate, as shown in FIG. The cement particles C, C,... Aggregate and condense so that a small amount of water W is held inside. This is so-called primary nucleation, and a nucleus N having a predetermined size is formed. As the hydration reaction further proceeds, such nuclei N loosely combine with other nuclei to form secondary nuclei. Since the binding force of secondary nucleation is weak, it can be easily cut by simply rotating the drum of the mixer truck, and there is no particular problem with the properties of the concrete at the initial stage. If the hydration reaction further proceeds, these nuclei N, N. It is estimated that the cement particles in the remaining concrete / returned concrete are partially nucleated, and the others remain as particles. The primary nucleated nucleus N has a relatively strong bonding force. When the crushing / drying step S7 is performed from the remaining concrete / returned concrete through the recovery process, the particulate concrete sludge fine powder collides with each other and a shearing force is applied. Depending on the shearing force, It is difficult to uncouple the nucleus N. If a strong dispersion action by the rotating crushing stirring blade 9 acts, the bond of the nuclei N can be released, but there is no guarantee that all the nuclei N are processed by the crushing stirring blade 9. Therefore, a part of the nuclei N, N,... Are combined and contained in the concrete sludge fine powder, and it is assumed that the nuclei N having a particle diameter of about 250 μm are present at a predetermined ratio. When these remaining nuclei N, N,... Are pulverized in the concrete sludge fine powder in the pulverization step S8, substantially all of the bonds are released and separated into cement particles C, C,. Guessed.

Investigating the effect of concrete sludge fine powder on the amount of water reducing agent required depending on whether concrete sludge fine powder contains particles with a particle size of 250 μm or more when mortar is produced using concrete sludge fine powder as a substitute for cement An experiment was conducted.
Experimental methods and results:
The remaining concrete / returned concrete was processed, and the slurrying step S3, the aggregate separation step S4, the fine sand removal step S5, the dewatering step S6, and the crushing / drying step S7 were performed to obtain concrete sludge fine powder. This was used as the concrete sludge fine powder of Comparative Example 1. The same treatment was performed 4 times to obtain 4 times of concrete sludge fine powder, which were used as the concrete sludge fine powder of Comparative 2-5. Next, the concrete sludge fine powders of Comparative 1 to 5 were separated by a predetermined amount, and the pulverization step S8 was performed so that particles having a particle diameter of 250 μm or more were substantially eliminated. These were made into the concrete sludge fine powder of this invention 1-5, respectively. Thereby, the concrete sludge fine powder of Comparative 1-5 and this invention 1-5 was obtained. Each of the concrete sludge fine powders of Comparative 1 to 5 and the concrete sludge fine powders of the present invention 1 to 5 were used as substitutes for cement, and mortars were produced as shown in Table 1. In Table 1, DSP means concrete sludge fine powder, W / C is a water cement ratio, and concrete sludge fine powder was regarded as cement. When producing mortar using each concrete sludge fine powder, the water reducing agent was adjusted to 160 mm in the table flow test. Table 1 shows the amount of the water reducing agent added when the result of the table flow test is approximately 160 mm. Further, the specific surface area of each concrete sludge fine powder was measured by the brane air permeation method.

Evaluation and discussion of experimental results:
Compared to the case where the concrete sludge fine powder of Comparative 1 to 5 in which particles having a particle size of 250 μm or more are present, the concrete sludge fine powder of the present invention 1 to 5 having substantially no particle size of 250 μm or more is used. Then, it has confirmed that the usage-amount of a water reducing agent decreased significantly. Generally, in the case of cement, the larger the specific surface area, the easier the water used for kneading is absorbed by the cement particles, and the viscosity of the mortar tends to increase. In other words, the larger the specific surface area, the more water reducing agent is required. Considering from such technical common sense in cement, the concrete sludge fine powder should require more water reducing agent as the specific surface area increases. However, in this experiment, it was confirmed that the specific surface area of the concrete sludge fine powder was increased by performing the pulverization step S8, but the necessary water reducing agent was decreased. The reason for this is unclear, but in the concrete sludge fine powders of Comparative 1 to 5, there is a predetermined proportion of core N as shown in FIG. 4, which has absorbed water inside. As a result, water may be consumed and the viscosity of the concrete may have increased. In any case, it can be confirmed that a concrete sludge fine powder substantially free of particles having a particle size of 250 μm or more requires a small amount of water reducing agent when used as a substitute for cement to produce mortar. It was. When concrete is produced using concrete sludge fine powder as a substitute for cement, the amount of water reducing agent used should be changed in the same manner depending on the presence or absence of particles having a particle size of 250 μm or more.

  Next, a method for collecting fine concrete sludge powder according to the second embodiment of the present invention will be described. In the recovery method according to the second embodiment, the crushing / drying step S7 is performed using the crushing / drying device 15 provided with the bowl-shaped drum shown in FIG. Step S8 is not performed. The crushing / drying device 15 is similar to the rotary dryer RD in that the dewatered cake is processed to obtain a fine powder of concrete sludge, but the processing is a batch type. The crushing / drying device 15 includes a bowl-shaped drum 16, and a rotary stirring blade 18 having a vertical rotation shaft is provided in the drum 16. The dewatered cake is scooped upward along the inner peripheral surface of the drum 16 by the rotary stirring blade 18 and falls near the center. In this way, the dehydrated cake is convected in the drum 16. The drum 16 is provided with a predetermined chopper, that is, a crushing stirring blade 19 near the center of the drum 16, and this crushes and crushes the dehydrated cake that is rotating at high speed. The drum 16 is provided with a dryer 20, and hot air is supplied to the inside by the dryer 20, and exhausted from an exhaust port not shown in the drawing. With this configuration, the dehydrated cake is crushed and dried substantially simultaneously, and the crushed dehydrated cake is efficiently crushed and crushed by the crushing stirring blade 19. The crushing / drying device 15 can process the dewatered cake in a batch manner to obtain fine powder of concrete sludge. If it does so, even if a dewatering cake changes to a concrete sludge fine powder, a process can also be continued forcibly for a predetermined time. Then, the concrete sludge fine powder is pulverized by the crushing and stirring blade 19, and processing substantially equivalent to the pulverization step S8 is performed. That is, by carrying out the crushing / drying step S7 for a sufficient time, the obtained concrete sludge fine powder can be made substantially free of particles having a particle size of 250 μm or more.

Also by the concrete sludge fine powder recovery method according to the second embodiment, a concrete sludge fine powder substantially free of particles having a particle size of 250 μm or more can be obtained, and such a concrete sludge fine powder can be used for cement. An experiment was conducted to confirm that a small amount of water reducing agent is sufficient when producing concrete by using as an alternative.
Experimental methods and results:
The dewatering cake was processed using the crushing / drying device 15 and the crushing / drying step S7 was performed over a sufficient time. When the particle size distribution of the obtained concrete sludge fine powder was examined, it was confirmed that particles having a particle size of 200 μm or more were not substantially contained. The concrete sludge fine powder was then used as a substitute for cement to produce a mortar. At this time, the composition of each material of the mortar was the same as the experiment of Example 2. Then, the amount of the water reducing agent added was adjusted so that the result of the table flow test was approximately 160 mm. The following data were obtained from the experiment.
Use rate of water reducing agent in mortar: 1.4%
Mortar table flow test: 161mm
Specific surface area of concrete sludge fine powder: 8050 cm2 / g

Evaluation and discussion of experimental results:
Considering the specific surface area of the concrete sludge fine powder, it can be said that the amount of water reducing agent used to produce the mortar is very small.
Also by the concrete sludge fine powder recovery method according to the second embodiment in which the pulverization step S8 is not performed, a concrete sludge fine powder substantially free of particles having a particle size of 250 μm or more can be obtained, and such concrete It was confirmed that the amount of water reducing agent used was small when mortar was produced using sludge fine powder as a substitute for cement.

DESCRIPTION OF SYMBOLS 1 Rotating drum 2 Dryer 5 Lifter 7 Rotating shaft 9 Crushing stirring blade 10 Input port 12 Exhaust hood 13 Discharge port 15 Crushing / drying device 16 Drum 18 Rotating stirring blade 19 Crushing stirring blade 20 Dryer RD Rotary dryer

Claims (3)

It is a recovery method that recovers concrete sludge fine powder mainly composed of cement from slurry-like treated materials such as residual concrete or return concrete to which predetermined water has been added, or washing wastewater generated from ready-mixed concrete factories. There,
The recovery method includes a separation step of removing gravel, sand and fine sand from the slurry-like object to obtain sludge water, a dehydration step of dehydrating the sludge water to obtain a dehydrated cake, and crushing the dehydrated cake・ It consists of a crushing and drying process to obtain concrete sludge fine powder by drying,
In the crushing / drying step, the dehydrated cake is put into a predetermined drum, crushing and stirring blades provided in the drum are rotated to crush and hot air is supplied into the drum to substantially crush and dry. A method for recovering concrete sludge fine powder, characterized in that the concrete sludge fine powder is pulverized in a state where particles having a particle size of 200 μm or more are substantially absent by performing drying in parallel . It is a recovery method that recovers concrete sludge fine powder mainly composed of cement from slurry-like treated materials such as residual concrete or return concrete to which predetermined water has been added, or washing wastewater generated from ready-mixed concrete factories. There,
The recovery method includes a separation step of removing gravel, sand and fine sand from the slurry-like object to obtain sludge water, a dehydration step of dehydrating the sludge water to obtain a dehydrated cake, and crushing the dehydrated cake・ Crushing / drying process to obtain concrete sludge fine powder by drying, and crushing the concrete sludge fine powder obtained in the crushing / drying process with a pin mill, jet mill, ball mill, or roller mill to obtain particles having a particle size of 200 μm or more. A method for recovering fine powder of concrete sludge, characterized by comprising a pulverizing step to make it substantially nonexistent. 3. The recovery method according to claim 2 , wherein in the crushing / drying step, the dehydrated cake is put into a predetermined drum, and a crushing stirring blade provided in the drum is rotated to crush and hot air is introduced into the drum. The concrete sludge fine powder is recovered by substantially simultaneously crushing and drying.

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