Method for producing recycled material

Abstract

To provide a recycled material production method that allows inexpensive granulation of unused surplus ready-mixed concrete to produce recycled material.SOLUTION: A recycled material production method comprises producing recycled material by granulating unused surplus ready-mixed concrete, through addition of sludge powder and / or concrete admixture to the ready-mixed concrete, followed by mixing and agitation.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing recycled materials by granulating unused ready-mix concrete. [Background technology]

[0002] Ready-mixed concrete produced at a ready-mixed concrete manufacturing plant (hereinafter referred to as "ready-mixed concrete plant") is transported by agitator truck and poured at the construction site. At this time, excess concrete is generated because the construction site orders more than the required amount of ready-mixed concrete. This results in waste, including "returned concrete" that is returned to the ready-mixed concrete plant unused without being unloaded from the agitator truck, "residual concrete" that is unloaded at the construction site but remains unused and is returned to the ready-mixed concrete plant by agitator truck, and ready-mixed concrete that is produced at the ready-mixed concrete plant but not shipped and remains unused. This unused ready-mix concrete is usually discharged from the drum of an agitator truck or from the mixer of a ready-mix concrete plant before it hardens, and disposed of as industrial waste.

[0003] Disposing of these waste materials places a heavy burden on the management of ready-mixed concrete plants, and as a way to deal with this, methods of treating ready-mixed concrete have been proposed, such as those in Patent Documents 1 and 2, in which granulating materials are added to the ready-mixed concrete, and the concrete is mixed and stirred to form granules. These granulating materials are organic granulating materials such as the polymeric material used in Patent Document 1 and the hydrophilic polymer (cellulose-based) used in Patent Document 2.

[0004] Furthermore, in ready-mix concrete plants, large amounts of wash water are generated during daily operations to wash plant equipment and agitator trucks. This wash water contains a large amount of cement particles, and is compressed in a filter press to separate it into solid sludge cake and liquid sludge water. The sludge water is then reused as mixing water for concrete production by suppressing the cement content below a specified concentration. However, in order to separate the wash water into sludge water and sludge cake, equipment such as a trommel or filter press is required, and ready-mixed concrete plants that do not have such equipment filter the wash water, generating sludge residue that contains components that would normally become sludge cake. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-62943 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-101133 Summary of the Invention [Problem to be solved by the invention]

[0006] The above-mentioned method for treating ready-mixed concrete using an organic granulating agent involves the following problems. (1) Because the procurement costs of polymeric materials and hydrophilic polymers are high, the processing costs of ready-mixed concrete made using them are also high. (2) Both polymeric materials and hydrophilic polymers are chemical materials and place a burden on the natural environment. (3) In the treatment of wash water from ready-mix concrete plants, sludge water can be reused, but no effective reuse methods have been established for sludge cake and sludge residue. As a result, they are landfilled as sludge, incurring high processing costs of several thousand yen per ton, which places a heavy burden on the management of concrete manufacturing plants.

[0007] The present invention has been made in consideration of the above points, and its object is to solve the above problems and to provide a method for producing recycled materials by inexpensively granulating unused ready-mix concrete to produce recycled materials. [Means for solving the problem]

[0008] In the method for producing recycled materials of the present invention, sludge powder and / or concrete admixtures are added to unused ready-mixed concrete, and the mixture is mixed and stirred to granulate the ready-mixed concrete, thereby producing recycled materials. The ready-mixed concrete may further contain sludge residue and / or sludge cake. The concrete admixture may be ground granulated blast furnace slag. [Effects of the Invention]

[0009] The present invention has at least one of the following effects. (1) The sludge powder obtained from sludge cake, which was previously disposed of at great expense, is used to produce recycled materials from unused ready-mix concrete, which contributes to the effective use of resources and enables recycled materials to be procured at a reduced cost. (2) Concrete admixtures such as sludge powder and blast furnace slag powder have lower procurement costs than granulating materials such as polymeric materials and hydrophilic polymers, so the cost of processing ready-mixed concrete to produce recycled materials can be reduced. (3) Concrete admixtures, such as ground granulated blast furnace slag, are natural mineral-derived resources, and recycled materials are also environmentally friendly. (4) Sludge residue and sludge cake, which have traditionally been disposed of at great expense, can now be mixed with ready-mixed concrete to produce recycled materials. DETAILED DESCRIPTION OF THE INVENTION

[0010] The recycled material manufacturing method of the present invention will be described in detail below.

[0011] [Example 1] <1> Overall structure The method for producing recycled materials of the present invention involves granulating and solidifying ready-mixed concrete to produce recycled materials. Ready-mixed concrete includes returned concrete, leftover concrete, and unused ready-mixed concrete produced at ready-mixed concrete plants but not shipped. Recycling this concrete can eliminate the cost of disposing of ready-mixed concrete as industrial waste and the waste of resources.

[0012] <2> Granulation material In this embodiment, sludge powder is used as a granulating material when granulating ready-mixed concrete. The sludge powder used as the granulating material is produced from washing water generated by washing plant equipment and agitator vehicles, and is obtained, for example, by the following manufacturing process. (1) The wash water is separated into sludge cake and sludge water. The sludge water is reused as mixing water. (2) The sludge cake is classified into gravel-like sludge pieces, granular sludge particles, and sand-like sludge sand. The sludge particles and sludge sand are reused as recycled coarse aggregate and recycled fine aggregate, respectively. (3) The sludge pieces are crushed to produce sludge sand and sludge powder, and the sludge powder is collected using a dust collector, etc. The sludge sand is reused as recycled fine aggregate.

[0013] The sludge powder granulation material is produced from the wash water of concrete manufacturing facilities, which was previously disposed of at great expense using conventional technology, and various concrete manufacturing materials can be recovered as by-products of the production, which contributes to the effective use of resources and means that it can be procured at a negative cost, making it cheaper to procure than granulation materials such as polymeric materials and hydrophilic polymers. This reduces the cost of processing ready-mix concrete to produce recycled materials.

[0014] <3> Recycled material manufacturing The recycled material is produced by stirring and mixing ready-mixed concrete and granulation material, and then hardening it. Stirring and mixing can be done on the ground, or by adding granulation material to the drum of an agitator truck carrying ready-mixed concrete and rotating the drum to stir and mix the ready-mixed concrete and granulation material. Conventional concrete granulators (such as Koyo Machine Industry Co., Ltd.'s "Konjari-kun (registered trademark)") can also be used. By stirring and mixing the fresh concrete and granulation material, the granulation material absorbs the moisture in the fresh concrete, and the binding paste coats the outer periphery of the coarse aggregate in the fresh concrete in a layer.Then, the recycled material is produced by hardening. The sludge powder used as the granulating material has a large Blaine value, exhibits a dehydration effect, and can be granulated quickly.

[0015] <4> Recovery of fine powders including sludge powder The recycled material produced by the above process is dried and then classified using a trommel or the like to separate it into recycled coarse aggregate and recycled fine aggregate. Note that it may also be classified using a trommel or the like before drying and then dried. Dried and classified recycled fine aggregate contains a large amount of fine powder. By recovering the fine powder from this recycled fine aggregate, high-quality recycled fine aggregate that does not contain fine powder can be obtained. The fine powder can be collected using, for example, a dust collector in a batcher plant. Furthermore, since the recycled fine aggregate after classification does not contain large recycled coarse aggregate, the fine powder can be efficiently sucked up and collected. The recovered fine powder contains not only dust but also sludge powder that can be used as a granulating material, and the recovered sludge powder can be used again as a granulating material to granulate ready-mixed concrete. In addition, since the recycled fine aggregate before the fine powder is recovered contains sludge powder, it can be used as is for granulating ready-mixed concrete.

[0016] [Example 2] <1> Granulation of sludge residue and sludge cake with ready-mix concrete In the above-mentioned Example 1, a granulating material (sludge powder) was added to returned concrete, leftover concrete, and ready-mixed concrete that was produced at a ready-mixed concrete plant but not shipped and was left unused, and the like, and the mixture was granulated. However, sludge residue or sludge cake can also be added to the ready-mixed concrete and granulated together with the ready-mixed concrete. Sludge residue and sludge cake are generated during the daily operations of ready-mixed concrete plants, and have traditionally been disposed of at great expense. By granulating these together with ready-mixed concrete, not only can processing costs be reduced, but they can also be used as recycled materials. As mentioned above, sludge powder and various concrete manufacturing materials can be recovered from sludge cake, but this requires manufacturing equipment. However, even in ready-mixed concrete plants that do not have such manufacturing equipment, sludge cake can be granulated together with ready-mixed concrete by using a granulating agent.

[0017] [Example 3] <1> Other examples of granulation materials In the above-mentioned Examples 1 and 2, the recycled material was produced using sludge powder as a granulating material. As another example, ground granulated blast furnace slag or fly ash, which have conventionally been used as concrete admixtures, or a mixture thereof may be used as a granulating material or in combination with sludge powder to produce recycled materials. Like sludge powder, ground granulated blast furnace slag and fly ash have a high Blaine value, exhibit a dewatering effect, and can be granulated quickly. Furthermore, ground granulated blast furnace slag and fly ash have lower procurement costs than granulating materials such as polymeric materials and hydrophilic polymers. This reduces the cost of processing ready-mixed concrete to produce recycled materials. Ground granulated blast furnace slag is also a resource derived from natural minerals, making the recycled material environmentally friendly. The surface of recycled materials containing ground granulated blast furnace slag is covered with a binding paste containing ground granulated blast furnace slag. Therefore, when recycled materials are used as aggregate, the latent hydraulic properties of the ground granulated blast furnace slag are utilized, resulting in high performance as an aggregate. Furthermore, when recycled materials containing fly ash are used as aggregate, the fly ash generates a pozzolanic reaction, resulting in high performance as an aggregate.

Claims

1. A method for producing recycled materials, comprising adding sludge powder and / or concrete admixture to unused fresh concrete, mixing and stirring the mixture, and granulating the fresh concrete to produce recycled materials.

2. A process of classifying and drying the granulated recycled material to obtain recycled coarse aggregate and recycled fine aggregate; and recovering fine powder containing sludge powder from the recycled fine aggregate using a dust collector. The method for producing recycled materials according to claim 1.

3. The ready-mixed concrete further contains sludge residue and / or sludge cake. The method for producing recycled materials according to claim 1.

4. The concrete admixture is characterized in that it is ground granulated blast furnace slag and / or fly ash. The method for producing recycled materials according to any one of claims 1 to 3.