JP4847056B2 - Concrete containing crushed shell - Google Patents

Description

  The present invention relates to concrete containing crushed shells as fine aggregates, and more particularly to concrete containing crushed shells having a specific particle size distribution and blast furnace cement.

  A large amount of seashells are generated as marine waste from shells such as oysters and scallops that are captured or collected by the fishery, and many of them are recycled, that is, cannot be recycled, and are landfilled as animal and plant residue. Or they have been left unattended on the beach because of no appropriate disposal.

  However, in recent years, land that can be used as landfill sites tends to decrease year by year, and due to environmental problems such as bad odors that occur when shells are left unattended, recycling of discarded shells is difficult. Recycling has gained more and more attention.

  On the other hand, as aggregates for concrete, sand and crushed sand such as river sand, mountain sand or sea sand as fine aggregate, and gravel and crushed stone such as river gravel or mountain gravel have been generally used as coarse aggregate. However, in recent years, in view of the problem of depletion of these natural aggregates and the preservation of the global environment, the use of various industrial byproducts and industrial wastes as substitutes for aggregates has been studied.

  R & D to use this shell waste as a concrete aggregate based on the flow of the above-mentioned demand for recycling shell waste and the utilization of industrial by-products and industrial waste as concrete aggregate Has come to be advanced.

  Such research includes, for example, research on coarsely pulverizing shells to a size of several tens of millimeters, and using this in place of coarse aggregates to produce porous concrete, or until sandy fine particles are obtained. There are studies that use finely crushed shells as part of concrete fine aggregates.

  When shells are used as concrete aggregates, there are two ways to use fine aggregates and coarse aggregates as in the above example, but shells are used for general concrete. When considered, it is often used as a fine aggregate for the following reasons.

(1) Since shells are less strong than gravel and crushed stone, using this instead of coarse aggregate will result in concrete with significantly reduced strength compared to ordinary concrete using gravel and crushed stone.

(2) Concrete used in general construction work must have workability that allows it to be easily filled into the formwork, but shells should be sized to a size suitable for the coarse aggregate blended in the concrete. When crushed, if this shell is a scallop shell, for example, it will produce a very thin and flat coarse aggregate, and if it is a oyster shell, for example, it will be thin, flat and rough on rough surfaces. Since aggregate is produced, it becomes very difficult to obtain concrete having good fluidity, that is, good workability.

  In this way, when shells are used as aggregates in general concrete, it is better to use these shells as fine aggregates in view of ensuring sufficient strength and workability for the concrete. It can be said that the utility value is high, but there are the following problems when the shell is made of fine aggregate.

(1) Even when replacing ordinary fine aggregates with shells, the replacement rate is limited to about 20-30% by volume so as not to cause a significant decrease in strength with concrete. From the viewpoint of effectively using as much as possible, further improvement of the substitution rate is desired.
(2) In order to ensure good workability with concrete made from shells of fine aggregate, this shell is finely pulverized to a particle size of 5 mm or less, which is suitable for fine aggregates. However, this work is not practical because it requires a lot of labor and cost.

に示される粒度分布を有する貝殻粉砕物を細骨材として用い、かつ、高炉セメントをセメントとして用いると、細骨材における貝殻粉砕物の置換率が３０容量％を超えても、良好なワーカビリティーが確保されるとともに、通常の細骨材のみを用いたコンクリートと同等またはそれ以上の強度を有するコンクリートが得られること、
を見出した。 The inventor has conducted various studies to solve the above-described problems,
Table-1 below,

When the shell pulverized product having the particle size distribution shown in FIG. 5 is used as the fine aggregate and the blast furnace cement is used as the cement, even if the replacement rate of the shell pulverized product in the fine aggregate exceeds 30% by volume, good workability is obtained. To obtain a concrete having a strength equal to or higher than that of ordinary concrete using only fine aggregates,
I found.

The present invention was invented based on such knowledge,
Concrete, characterized in that a shell pulverized product having the particle size distribution shown in Table 1 is used as a part or all of the fine aggregate, and blast furnace cement is used as cement.
It is related to.

  According to the present invention, the crushed shell material is used as a fine aggregate of concrete, and a blast furnace cement is also used as the cement. As a result, it is possible to obtain a concrete that has the same or better strength as concrete that uses only fine aggregates and that has good workability. As a result, it is possible not only to reduce the harmful effects and burdens caused by the disposal of this large amount of shellfish waste, but also to remove aggregate sand, gravel and crushed stones from the natural environment. By reducing the amount, it can also contribute to environmental conservation of the earth.

  As the blast furnace cement used in the present invention, for example, in addition to “JIS R 5211 blast furnace cement” types A, B and C, “JIS R 5210 Portland cement” mixed with blast furnace slag fine powder is used. In this latter case, JIS R 5210 Portland cement and ground granulated blast furnace slag are generally mixed in a volume ratio of 95-30 to 5-70.

  In general, any type of shell can be used as the shell, but scallops or oyster shells are suitable, and scallop shells mainly composed of calcium carbonate are particularly preferably used.

  In the concrete in which the crushed shell material having the particle size distribution shown in Table 1 is used as a fine aggregate and combined with ordinary Portland cement, the strength tends to decrease as the blending amount of the crushed shell material increases. is there. This tendency has been obtained by conventional research, “in order to prevent a large decrease in strength with hardened concrete, the replacement rate with ordinary fine aggregate is limited to about 20 to 30%”. It matches the result.

  By adopting a blast furnace cement as a cement to be combined with a fine aggregate shell crushed material, it is possible to obtain a strength equal to or higher than that of conventional concrete containing a normal aggregate. The reason for this is thought to be the result of the reaction between calcium carbonate, the main component of the shell pulverized product, and various calcium aluminates that are easily formed in blast furnace cement. In addition, it is considered that the establishment of the particle size distribution shown in Table 1 in the crushed shell is also contributing.

  The particle size distribution of the crushed shell material shown in Table 1 is shown in FIG. 1 of the accompanying drawings. When the particle size of the crushed shell becomes coarser than the range shown in Table 1, in other words, when the particle size range of the crushed shell is shifted to the right from the range shown in FIG. Not only can sufficient strength not be obtained, but good workability cannot be obtained with fresh concrete, while the particle size of the shell pulverized product becomes finer than the range shown in Table 1, in other words, the particle size range of the shell pulverized product. 1 shifts to the left from the range of FIG. 1, the reactivity with the blast furnace cement is enhanced, but it cannot be easily manufactured with the rotary crushing and mixing machine and is not practical in terms of cost. As the proportion of fine-grained components increases and the viscosity of concrete increases, it becomes difficult to use in large quantities. Therefore, the particle size range of shell crushed material is within the range shown in Table-1. It has become an essential requirement for the present invention.

In order to make the shell into a pulverized product having the particle size distribution shown in Table 1, generally any kind of crusher or crusher can be used.
By using a rotary crushing mixer as shown in Japanese Patent No. 3554829 relating to the applicant's patent, and adjusting the number of revolutions during crushing, the shell crush having the particle size distribution shown in Table 1 above Products can be manufactured easily, and as a result, the use of this rotary crushing mixer for the production of crushed shells has sufficient practicality in terms of cost,
The inventor has also found out.

  FIG. 2 shows the relationship between the particle size distribution of the pulverized material obtained when the scallop shells are pulverized using the above rotary crushing mixer and the rotational speed of the rotary crushing mixer. It can be seen that as the rotational speed increases, the particle size distribution curve shifts to the left, and the particle size of the pulverized product becomes generally finer. Thus, according to the rotary crushing and mixing machine, shell pulverized products having various particle sizes can be easily obtained within the range of the particle size distribution shown in Table 1 by adjusting the rotation speed thereof.

  The following examples are intended to specifically illustrate preferred examples for practicing the present invention, and are not intended to limit the invention to these examples.

Example 1
Using the materials shown in Table-2 below, and according to the concrete composition shown in Table-3 below, that is, using blast furnace cement type B as cement, and 0% by volume of fine aggregate river sand, 25% volume, 50% volume, 75% volume and 100% volume were replaced with ground shell material. Ordinary Portland cement was used as cement, and 0%, 25% and 50% volume of river sand was ground with shell material. In each of these cases, the cement, fine aggregate, and coarse aggregate were first put into a mixer and kneaded, and then mixed with water and AE water reducing agent for 90 seconds. Comparative sample 1, inventive samples 1, 2, 3, 4 and comparative samples 2, 3, 4 were produced. The above shell pulverized product has a particle size distribution as shown by the particle size distribution curve-●-in Fig. 2 by being pulverized under the rotation speed of 900 rpm using the rotary crushing and mixing machine. there were.

  The fresh concrete produced as described above is subjected to a slump test and an air amount test, and the concrete after curing is measured for compressive strength at the age of 7 and 28 days. Table 4 of Table 1 also shows that the concrete ratio in each case of 0%, 25%, 50%, 75% and 100% of the crushed shell relative to the compressive strength of the concrete in which the crushed shell is replaced by 0% The compression strength ratio, that is, the compression strength ratio shown in Table 4 is shown in FIG.

  According to Table-4 and FIG. 3, the usage amount of the crushed shells in the inventive samples 1, 2, 3 and 4, that is, the replacement rate with river sand which is a normal fine aggregate is 25%, 50% and 75, respectively. However, the compression strength of these samples according to the present invention was not compared with that of Comparative Sample 1 as compared with Comparative Sample 1 in which the substitution rate with river sand was 0%. It can be seen that the strength is exceeded. Such a result clearly shows that the present invention tends to be significantly different from the prior art in which the replacement rate of the crushed shell in concrete is recognized to be limited to about 20 to 30%.

  Further, in Comparative Sample 3 in which normal Portland cement was used as the cement and the replacement rate of the shell crushed material was 25%, the compression strength was reduced compared to Comparative Sample 2 in which the replacement rate was 0%, and It can be seen that in the comparative sample 4 in which the substitution rate was 50%, this strength reduction was further remarkable. Such a result shows a tendency similar to that of the conventional technique in which the substitution rate of the shell pulverized material is limited to about 20 to 30% at the maximum in the concrete in which ordinary Portland cement is used as the cement. The tendency which is remarkably different from the sample of the present invention is clearly shown.

  As is clear from the above description, the present invention uses conventional ground aggregates instead of ordinary fine aggregates as a fine aggregate, and blast furnace cement as a cement. Since concrete which is inferior to concrete can be provided, the present invention can be used in a wide range of fields to which such ordinary concrete is applied.

It is a graph which shows the particle size range of the shell crushed material used by this invention. It is a graph which shows the relationship between the rotation speed of the rotary crushing mixer preferably used by this invention, and the particle size distribution of the shell ground material obtained by this rotary crushing mixer. It is a graph which shows the compressive-strength ratio of concrete with the substitution rate of 0%, 25%, 50%, 75%, and 100% of the shell ground material with respect to the concrete with the replacement rate of the shell ground material of 0%.

Claims (2)

A concrete characterized in that a shell pulverized product having a particle size distribution shown in the following Table-1 is used as part or all of the fine aggregate, and blast furnace cement is used as cement.

The concrete according to claim 1, which is a crushed shell obtained by treating the crushed shell with a rotary crushing and mixing machine.

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