JPH10114556A - Production of reclaimed cement, and reclaimed cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reclaimed cement high in initial and long-age strength and with the heat of hydration low at the time of processing the fine grain generated when spent cement is reclaimed to obtain a reclaimed cement. SOLUTION: The undersize obtained by separating the fine grains with 2.5-0.3mm, preferably 1.5-0.5mm, separation diameter is crushed and processed. The undersize is heat-treated at 400-800 deg.C, preferably at 600-750 deg.C or more preferably at about 700 deg.C and crushed. The crushed material is hat-treated at 400-800 deg.C, preferably at 650-700 deg.C or more preferably at about 700 deg.C. The crushed fine grain is controlled to <=0.1mm diameter and 8000-10000cm<2> /g Blaine specific surface. The content of the spent cement fine powder in the reclaimed cement is adjusted to >=60wt.%, especially to 60-80wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the recycling of waste concrete, and more particularly to a method for producing a recycled cement using fine powder generated during recovery of coarse aggregate and fine aggregate from concrete waste and a base material. It relates to recycled cement.

[0002]

2. Description of the Related Art Conventionally, most of concrete waste generated when dismantling concrete structures has been disposed of by landfilling, etc. Processing costs are also rising. On the other hand, the use of concrete waste as a resource has also been studied in accordance with the enactment of the Resource Recycling Law, and some of it has been used as paving stones for roadbed materials, etc. It is also possible to recover high quality fine aggregate and coarse aggregate.

[0003] However, in order to obtain high-quality aggregates, crushing and grinding of concrete pieces are required, so that 20 to 30% of waste concrete fine particles are generated.
These fine particles have no special use, and calcium hydroxide is generated with the hydration of cement.When the fine particles come into contact with water, calcium hydroxide dissolves and exhibits high alkalinity, thus causing water pollution. There are difficulties in landfill disposal,
Its disposal is a major problem.

Under such circumstances, a method of recycling as a hydraulic material by adding a mixed material composed of blast furnace slag, gypsum, cement, etc. to waste concrete fine powder (Japanese Patent Laid-Open No. Sho 62-62)
158146, JP-A-63-2842) have been proposed. However, these have the drawback that their strength after hydration curing is low, and that they require a lot of time for curing, and their uses are limited. Furthermore, in order to increase the strength after hydration hardening, it is necessary to significantly increase the amount of the mixed material such as slag, and therefore, the used amount of the waste concrete fine powder is only 20 to 50 parts by weight, At present, waste concrete fines have not been used in large quantities.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks, and effectively utilizes fine powder generated in the recycling of aggregate by advanced treatment of waste concrete without discarding it as a resource. It is an object of the present invention to provide a method for producing a regenerated cement having a high initial strength and a long-term strength and a low hydration heat generation property, and a regenerated cement.

[0006]

In order to achieve the above-mentioned object, according to the method for producing regenerated cement of the present invention, fine particles generated when reclaiming concrete waste material are prepared to produce regenerated cement. A fine particle having a separation diameter of 2.5 mm to 0.3 mm, preferably 1.5 mm.
(1) pulverizing and preparing the sieved material separated at a diameter of 0.5 to 0.5 mm (claim 1);
(Claim 2), heat treatment at 400 to 800 ° C. after grinding the pulverized material (Claim 3), and a particle diameter of 0.1 mm or less and a Blaine specific surface area of 8000 cm. Pulverizing to ² / g or more (claim 4).

Further, according to the recycled cement of the present invention,
The waste concrete fine powder obtained by preparing any of the fine particles according to any one of the above is used as a main constituent material (Claim 5), and the waste concrete fine powder is at least 60% by weight or more (Claim 6). ). Hereinafter, the present invention will be described in detail.

[0008]

The first object of the present invention is to manufacture recycled cement by preparing fine particles generated when recovering high quality coarse aggregate and fine aggregate by subjecting concrete waste material to advanced treatment. Features. Preparation of the fine particles is performed by crushing the fine particles.
A sieve pass separated at m to 0.3 mm, preferably 1.5 mm to 0.5 mm is used. The inventors have found that the separation diameter of the fine particles greatly affects the physical properties of the regenerated cement, and as a result of various studies, determined that the separation diameter of the fine particles is in the predetermined range, that is, slightly coarse. The present invention has been completed by improving the fluidity of mortar and concrete by taking in a part of fine aggregate and pulverizing the fine aggregate.

Fine particles having a separation diameter of less than 0.3 mm, even when used as such or when crushed and applied to mortar or concrete, have poor fluidity of the mortar or concrete and reduce the weight due to entrainment of air. The strength decrease is remarkable. For example, although the Blaine specific surface area of the under-sieved material having a separation diameter of 150 μm is about 5600 cm ² / g, when this is used for regenerated cement, the mortar flow in the JIS mortar test is 18
0 mm, the mortar weight is 2.053 kg / l. Even if the fine particles are crushed to a Blaine specific surface area of about 8000 cm ² / g, the mortar flow is 192 mm and the mortar weight is 2.
Although slightly improved to 066 kg / l, a decrease in weight due to poor fluidity is observed.

[0010] Further, even if the separated material having a separation diameter of more than 2.5 mm passes through the sieve, the amount of fine aggregate recovered becomes smaller than the effect of improving the fluidity, and the strength increases. It is not preferable because the increase in hydraulic performance due to the heating effect of the fine particles described below decreases.

Next, the material passed through the sieve is heated at 400 to 800 ° C., preferably 600 to 75 ° C. before or after the pulverization.
Heat treatment at 0 ° C. is desirable. As described above, fine particles are obtained as a residue obtained by crushing and grinding concrete waste material to separate and remove aggregates such as gravel, and crushed powder of coarse aggregate and fine aggregate, cement powder. Calcium silicate hydrate (CSH), which is a hydration product of
Monosulfate, calcium hydroxide, and calcium carbonate and some unhydrated cement particles, etc., the content of calcium carbonate increases with the aging of concrete, unhydrated cement particles hardly remain, There is almost no hydraulic action of the fine particles.

However, the fine particles become hydraulically hard by being heated at 400 ° C. or higher, and the hydraulic performance increases as the heating temperature increases. The cause of hydraulic is the formation of belite. Surprisingly, it has been found that the production of belite starts at a very low temperature of 400 ° C., and the amount of the produced fine particles increases as the heating temperature increases. But 80
When heated above 0 ° C, contained calcite decomposes to produce calcium oxide.
The increase in the amount of water is not only significant but also causes abnormal expansion. Therefore, when judged comprehensively, the heating temperature is preferably from 600 to 750 ° C, more preferably around 700 ° C.

In the pulverization of the fine particles, it is preferable that the particle size is 0.1 mm or less and the Blaine specific surface area is 8000 cm ² / g or more. As the pulverizing means, various pulverizing means such as a ball mill, a roller mill, and a disk mill can be used.
As described above, the fine particles contain hydration products of cement and some unhydrated cement particles, and the hydraulic performance is enhanced by heating. However, the particle size is 0.1 mm or less, and the fineness is 8000 cm. By setting it to ² / g or more, the hydraulic property is increased due to the appearance of the fine unhydrated cement particle surface, the hydration structure is destroyed, and the fluidity after the water kneading can be improved. If it is less than 8000 cm ² / g, hydration becomes non-uniform and strength is undesirably reduced. Usually, the specific surface area of the brane is 8,000 cm ² / g to 10,000 cm
More preferably, it is in the range of ² / g.

The reclaimed cement of the present invention comprises the waste concrete fine powder prepared as described above as a main constituent material, and preferably contains at least 60% by weight or more of the waste concrete fine powder. It is. That is,
In order to obtain high-strength recycled cement from waste concrete fine powder having almost no hydraulic property, various high-performance admixtures mainly composed of blast furnace slag fine powder described later are added to increase initial strength, and fine powder fly ash Activated pozzolans such as silica flour and the like are used to improve long-term strength, etc., but the amount of the waste concrete fine powder is 60% by weight or more, preferably 60 to 80% by weight in the recycled cement. Is preferred. If it is less than 60% by weight, the strength after curing will increase, but it will not be suitable for the large-scale use of concrete wastes aimed at by the present invention, and the mixing ratio of other materials such as blast furnace slag will increase, and the reaction heat will increase. It is not preferable from the viewpoint of low heat build-up because it rises. Also,
If it exceeds 80% by weight, the strength after curing is significantly reduced, which is not preferable.

Next, as a mixed material to be added to the waste concrete fine powder, blast furnace slag fine powder is optimal both economically and in terms of strength development. Particularly, in terms of strength development, the fineness of the blast furnace slag has a great effect, and the finer the powder, the better the strength development. In other words, when a large amount of concrete fine powder is used, the fineness of the slag powder is required to be evenly distributed around the concrete fine powder, and the fineness of the slag is determined by the mixing ratio of the waste concrete fine powder and the slag powder. When the value is multiplied by the fineness of the waste concrete fine powder, good strength development can be obtained. For example, waste concrete fine powder 60 parts by weight, slag powder 40
Assuming that the fineness of the waste concrete powder is 8000 cm ² / g in the recycled cement by weight, the fineness of the slag is
It is preferred to be 12000 cm ² / g or more.

If the amount of the blast furnace slag fine powder in the recycled cement is increased, the strength can be improved by increasing the blast furnace slag fine powder. Below, preferably 20 to 40
% By weight. If it exceeds 40% by weight, the strength after curing increases, but the amount of waste concrete fine powder cannot be increased, and the amount of heat of reaction is undesirably increased. When the content is less than 20% by weight,
This is not preferable because the strength after curing is significantly reduced.

The recycled cement of the present invention preferably contains gypsum in addition to the waste concrete fine powder and the blast furnace slag fine powder. By blending gypsum, it acts as a reaction stimulant for blast furnace slag and a void filler at the early stage of curing, and can increase initial strength and reduce drying shrinkage. As the gypsum, anhydrous gypsum, gypsum dihydrate, hemihydrate gypsum and the like can be used. The gypsum used in the present invention is preferably dried and pulverized to a fineness of 2000 to 7000 cm ² / g. As a pulverizing means, a vertical mill or a ball mill is preferable. For dihydrate gypsum, drying and pulverization are preferably performed at 60 ° C. or less. In addition, the gypsum can be mixed and pulverized together with the waste concrete fine particles. In this case, the fineness after the mixing and pulverization is 8000.
It is preferably at least cm ² / g. The amount of gypsum in the recycled cement is 2 to 2 gypsum in anhydrous conversion.
Preferably, it is 6% by weight. If it exceeds 6% by weight, the amount of swelling is so large that the strength after curing is undesirably reduced.

In the above-mentioned mixed material, cement fine powder and at least one activated pozzolan such as fine fly ash or silica flour having a particle size of 5 μm or less can be blended in place of a part of the blast furnace slag fine powder. . The incorporation of the fine cement powder enables the development of the initial strength, and the incorporation of the fine fly ash and the silica flour allows the medium to long-term strength enhancement.

As the cement, various cements such as ordinary Portland cement, early-strength Portland cement, moderately heated Portland cement, etc., as well as mixed cement and cement made mainly from municipal ash can be used. The fine cement powder used in the present invention is capable of accelerating the alkali stimulating effect of the fine blast furnace slag powder by pulverizing and classifying the fineness to the same level as that of the fine blast furnace slag powder by classification, and Early hydration can contribute to an improvement in initial strength. The blending amount of the cement fine powder is preferably about 1 to 12% by weight in the regenerated cement of the present invention by being replaced with an amount of 30% by weight or less of the blast furnace slag fine powder.
If the amount of the cement fine powder exceeds 12% by weight, the heat of reaction increases, which is not preferable. In addition, when cement is blended, the gypsum is not necessarily blended.
In addition, when the waste concrete is relatively young and has a high calcium hydroxide content, or when the gypsum is blended as a mixture, the cement fine powder does not necessarily need to be blended.

Amorphous activated pozzolan, such as fine fly ash and silica flour having a particle size of 5 μ or less, reacts with the high alkali calcium hydroxide produced by hydration of the blast furnace slag fine powder and cement fine powder. Mid-term (7 days)-
Long-term (after 28 days) strength can be exhibited. Amorphous pozzolans can be obtained by mixing 30 fine powders of the blast furnace slag.
It is preferable that about 1 to 12% by weight of the reclaimed cement of the present invention is replaced with less than 1% by weight.

As described above, the reclaimed cement of the present invention comprises waste concrete fine powder and blast furnace slag fine powder as main constituent materials, and gypsum, cement fine powder, and activated pozzolan such as fine powder fly ash and silica flour. At least one kind is blended, and the fineness of each material is adjusted and blended. The fineness after mixing these materials is 8500 cm ² / g or more in terms of Blaine value. It is preferable in terms of properties. The mixing is not particularly limited as long as uniform mixing is possible. Further, the waste concrete fine particles, blast furnace slag, and cement have different grindability of each material, and it is desirable to separately grind each of them in order to set an arbitrary fineness.

The regenerated cement of the present invention develops strength by kneading and curing water in an optional amount. Therefore, the reclaimed cement of the present invention can be used as a paste material, a mortar material, or a concrete material, with or without addition of various admixtures (materials), in addition to sand, gravel, and the like, similarly to general cement.

[0023]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. In addition, all the compounding ratios% shown below are% by weight.

(Example 1) Fine particles generated during the recovery of coarse aggregate and fine aggregate from concrete waste of 30 years of age are separated at a separation diameter of 4.0 mm to 0.15 mm into various sizes. An undersize sieve was obtained. Then, blast furnace slag 35.3 weight and under sieve pass was Blaine specific surface area of 8000 cm ² / waste concrete powder obtained by pulverizing such that g 60 parts by weight, Blaine specific surface area of 12000 ² / g Parts and 4.7 parts by weight of anhydrous gypsum having a specific surface area of 4000 cm ² / g to prepare a regenerated cement.
A mortar test was performed according to 5201. Each material was pulverized using a vertical mill, and then classified and prepared using CLASIEL (a classifier manufactured by Chichibu Onoda Co.). In addition, NO7 refers to the material passed under the sieve as it is (unground material, Blaine specific surface area 5600
cm ² / g). Table 1 shows the results.

[0025]

[Table 1]

As shown in Table 1, the separation diameter of the fine particles greatly affects the physical properties of the recycled cement.
When the concrete fine powder of 5 mm (150 μm) is supplied to the regenerated cement in an unground state (NO7), the fluidity is poor and the air is involved and the mortar weight is reduced. Further, even with NO6 obtained by pulverizing 150 μm-separated fine powder, although the mortar flow is slightly improved, a decrease in weight due to poor fluidity is observed, leading to a decrease in strength.
On the other hand, in the case of using the fine powder obtained by separating at 0.3 to 2.5 mm (NO2 to 5), the mortar flow, mortar capacity and compressive strength were all significantly improved.
It should be noted that even if the separated material having a separation diameter of more than 4.0 mm was crushed, the effect of improving the fluidity and strength was small and the amount of high quality fine aggregate recovered was reduced.

(Example 2) 60 parts by weight of a waste concrete fine powder obtained by pulverizing the fine particles of the waste concrete of Example 1 through a sieve separated at 1.2 mm into various finenesses, and a different fineness 35.3 parts by weight of blast furnace slag fine powder and 4.7 parts by weight of anhydrous gypsum having a Blaine specific surface area of 4000 cm ² / g were mixed to prepare a regenerated cement, which was subjected to a mortar strength test in accordance with JIS R5201. As shown in Table 2, the compressive strength is excellent when the fineness of the waste concrete is 8000 cm ² / g or more and the fineness of the blast furnace slag is 12000 cm ² / g or more.

[0028]

[Table 2]

(Example 3) The waste concrete fine particles of Example 1 were separated by 1.2 mm and heated under a sieve.
And waste concrete powder 60 parts by weight of Blaine specific surface area obtained by pulverizing such that 8000 cm ² / g, blast furnace slag of Blaine specific surface area of 12000 ² / g 35.3
Parts by weight and 4.7 parts by weight of anhydrous gypsum having a Blaine specific surface area of 4000 cm ² / g to prepare a regenerated cement.
A mortar strength test was performed according to SR 5201. As shown in Table 3, the strength of the waste concrete fine powder was increased by heating, but when the heating temperature reached 900 ° C., the amount of water increased not only significantly but also caused abnormal expansion due to the formation of calcium oxide. .

[0030]

[Table 3]

Example 4 Waste concrete fine powder obtained by pulverizing the waste concrete fine particles of Example 1 separated by 1.2 mm under a sieve to have a Blaine specific surface area of 8000 cm ² / g. And the specific surface area of Blaine is 12000cm
² / g blast furnace slag fine powder and a Blaine specific surface area of 400
0 cm ² / g of anhydrous gypsum and a Blaine specific surface area of 12000
Ordinary Portland cement of cm ² / g, fine fly ash having an average particle size of 5 μm or less, and silica flour of 1 μm or less were prepared and mixed at various ratios shown in Table 4 to obtain a regenerated cement. Next, a mortar strength test was performed according to JIS R 5201. As the results are shown in Table 4,
It can be seen that the present invention has a balance between early strength, stability and long-term strength.

[0032]

[Table 4]

[0033]

According to the present invention, waste coconut fine powder can be used in large quantities as a recycled cement having a balance between early strength, stability and long-term strength.
It can greatly contribute to effective use of resources and elimination of landfill depletion.

Claims (6)

[Claims] 1. A method for producing a recycled cement by preparing fine particles generated when a waste concrete material is regenerated, wherein the fine particles have a separation diameter of 2.5 mm to 0.3 mm,
A method for producing a recycled cement, characterized by pulverizing and preparing a material passed through a sieve separated preferably at 1.5 mm to 0.5 mm. 2. The method for producing a recycled cement according to claim 1, wherein the material passed under the sieve is heat-treated at 400 to 800 ° C. and pulverized. 3. The method for producing recycled cement according to claim 1, wherein the material passed under the sieve is pulverized and heat-treated at 400 to 800 ° C. 4. The method for producing a recycled cement according to claim 1, wherein the pulverization is performed to a particle diameter of 0.1 mm or less and a Blaine specific surface area of 8000 cm ² / g or more. 5. Recycled cement characterized by using, as a main constituent material, waste concrete fine powder obtained by preparing the fine granules according to claim 1. 6. The method according to claim 6, wherein the waste concrete powder is at least 60.
The recycled cement according to claim 5, wherein the cement content is at least 10% by weight.