KR100481082B1 - Method for manufacturing concrete blended with oyster shell and the concrete of the same - Google Patents

Abstract

The present invention relates to a concrete mixed with oyster shells recycled oyster shells, which are wastes generated in coastal oyster farms, and a method of manufacturing the same, and drying the oyster shells in a drying furnace at 100 to 120 ° C., wherein the dried oyster shells are 2.1 to 2.7 Crushing the oyster shell with the granulation rate, the concrete mixed with the oyster shell through the step of mixing with the cement, fine aggregate, coarse aggregate, admixture and water by replacing a certain proportion of the total fine aggregate used in concrete with the crushed oyster shell can do.

Description

Concrete mixed with oyster shells and method for manufacturing the same {METHOD FOR MANUFACTURING CONCRETE BLENDED WITH OYSTER SHELL AND THE CONCRETE OF THE SAME}

The present invention relates to a concrete and a method of manufacturing the same by mixing oyster shells, which are wastes generated in coastal areas, by replacing some of the total fine aggregates used for concrete production with crushed oyster shells.

Concrete is generally produced by mixing an appropriate amount of cement, fine aggregate, coarse aggregate and water, or by adding a small amount of admixture according to the required physical properties.

By the way, fine aggregate must use sand which is allowed to legal standard because of stability of construction structure. Sand is generally collected in rivers, and with the expansion of the construction market, its collection is gradually decreasing, and it is difficult to secure suitable sand, thereby increasing the manufacturing cost and adversely affecting the properties of concrete when using bad sand. Can be crazy In addition, the problems of natural and environmental destruction due to indiscriminate sampling are emerging.

On the other hand, in coastal areas, oyster shells, which are wastes due to oyster farming, are produced in large quantities, but only a portion of them are recycled as raw materials for fertilizer and calcium. Most of the oyster shells are not recycled, but are buried or illegally stacked around them. It is neglected. Therefore, it is difficult to secure landfills for oyster shells, as well as environmental damage and environmental pollution due to subsequent disposal of landfills and leaks, and when accumulated, severe odors and pollution may adversely affect hygiene and residential environment. Therefore, research is being conducted on environmentally friendly construction materials by recycling discarded oyster shells.

Accordingly, the present invention is designed to solve the above problems, it is easy to secure the raw material, reduce the cost, can maintain the required physical properties, and concrete that can prevent environmental pollution by recycling waste The purpose is to provide a manufacturing method.

Concrete of the present invention for achieving the above object is to replace a part of the fine aggregate in the concrete produced by mixing cement, fine aggregate, coarse aggregate, admixture and water with a crushed oyster shell having an assembly rate of 2.1 to 2.7 will be. In addition, the admixture may include a certain weight part of the AE reducing agent relative to 100 parts by weight of cement, and the crushed oyster shell is preferably 5 to 10 parts by weight of 100 parts by weight of the total fine aggregate.

And the method for producing concrete according to the present invention comprises the steps of putting the oyster shell in a drying furnace and drying by heating to 100 to 120 ℃, crushing the dried oyster shell into particles of the granulation rate of 2.1 to 2.7, a part of the total fine aggregate It consists of mixing cement, fine aggregate, coarse aggregate, admixture and water in place of oyster shell. In addition, in order to increase the workability and durability of concrete, it is preferable to use a constant weight part of the AE reducing agent with respect to 100 parts by weight of the cement as the admixture. In addition, the crushed oyster shell is preferably used 5 to 10 parts by weight of 100 parts by weight of the total fine aggregate required for concrete production.

Hereinafter, concrete and a manufacturing method of the mixed oyster shell of the present invention will be described in detail.

Concrete mixed with oyster shell according to the present invention is to replace a part of the fine aggregate in the concrete produced by mixing cement, fine aggregate, coarse aggregate, admixture and water with a crushed oyster shell having a granulation rate of 2.1 to 2.7.

Since the crushed oyster shell used in the concrete mixed with the oyster shell has a low assembly rate and has been dried for a long time, the slump (SLUMP) is small in the conventional compounding ratio, which makes it difficult to work or construct. Therefore, it is necessary to add a admixture for generating ETAINED AIR in order to improve the workability or workability while including the appropriate amount of air required for durability. It is preferable to use an AE reducing agent as such admixture, and it is preferable to use 0.3 weight part of AE water reducing agent with respect to 100 weight part of cement.

The crushed oyster shell is required to be properly mixed to the concrete properties of the concrete, preferably 5 to 10 parts by weight of 100 parts by weight of the total fine aggregate.

Method for producing concrete mixed oyster shell according to the present invention, the step of putting the oyster shell in a drying furnace and drying by heating at 100 to 120 ℃; Grinding the dried oyster shell into oyster shells having a granulation ratio of 2.1 to 2.7; A part of the total fine aggregate is replaced with the crushed oyster shell, and the cement, fine aggregate, coarse aggregate, admixture and water are mixed.

The drying at the temperature is for removing moisture to smoothly crush the oyster shell.

The dried oyster shell is put in a jaw crusher (JAW Crusher) and pulverized, passed through the 5mm or less to obtain a crushed oyster shell with a granulation rate of 2.1 to 2.7.

Here, the crushed oyster shell has a lower assembly rate than the sand (generally about 3.44) of the sand used as the general fine aggregate, so the workability of the concrete is reduced due to the low slump, and is sufficient to increase durability. It does not provide air volume. Therefore, in order to improve such workability and durability, the addition of a admixture is required. As the admixture, it is preferable to use 0.3 parts by weight of an AE reducing agent based on 100 parts by weight of cement.

In addition, the crushed oyster shell is preferably used 5 to 10 parts by weight of 100 parts by weight of the total fine aggregate required for concrete production.

The following is a test of the physical properties of the concrete produced by the above method.

Cement needed for concrete production was used one type of Portland cement. Fine aggregates used sand with specific gravity 2.61, water absorption rate 0.81%, assembly rate 3.44, and coarse aggregates used crushed stone with specific gravity 2.74, water absorption rate 0.60%, aggregate maximum diameter 25mm. It was.

In order to make the crushed oyster shell required for the production of concrete according to the present invention, first put the oyster shell to be used in the experiment in a drying furnace and dried by heating at 100 to 120 ℃ 24 hours, the dried oyster shell crushed using a jaw crusher (JAW Crusher) Then, it was passed through a 5mm sieve to make a crushed oyster shell having a granulation ratio 2.1 and a crushed oyster shell having a granulation ratio 2.7.

The crushed oyster shell angle was tested by specifying the A type oyster shell and B type oyster shell on the basis of the assembly rate in Table 1.

TABLE 1

Oyster shell type importance Absorption rate (%) Assembly rate Type A 2.39 4.40 2.7 Type B 2.1

Meanwhile, in order to compensate for the deterioration in workability due to mixing of oyster shells, 0.3 parts by weight of an AE reducing agent capable of generating entrained air was added to 100 parts by weight of cement.

The concrete mixing ratio of the experiment was 7 to 8 cm for the target slump of the standard mixture, and the amount of air was to satisfy 4 to 6% when the AE water reducing agent was added.

Table 2 shows the formulations except the AE water reducing agent among the mixing ratios used in the experiment, and the mixing ratio is the formulation that satisfies the standard value of W / C (water / cement) required for securing durability of marine concrete, and the design reference strength is 300 kgf. / cm ₂ was aimed at.

TABLE 2

Type of compound W / C (%) S / a (%) Unit weight (kg / m ³ ) W C S G NNO 45 43.2 180 400 725 (0) 1002 OA05OB05 45 43.4 180 400 689 (36) 998 OA10OB10 45 43.6 180 400 653 (73) 995 OA20OB20 45 44.0 180 400 580 (145) 988

Oyster shell input used as a substitute for fine aggregates, W: water, C: cement, S: sand, G: coarse aggregate, a: sand + coarse aggregate

The specimens produced by the above compounding ratios were classified as shown in Table 3.

TABLE 3

designation Whether to add AE reducing agent Oyster shell type Oyster Shell Replacement Rate (%) NNO radish - 0 OA05OA10OA20 radish Type A 51020 OB05OB10 Type B 510 RA05RA10RA20 U Type A 51020 RA05RA10 Type B 510

The experiment was carried out to evaluate the construction characteristics of fresh concrete (change of slump and air volume) and mechanical properties (compressive strength, split tensile strength, modulus of elastic modulus) of hardened concrete according to oyster shell replacement rate. I wanted to see.

Experimental Example 1

In order to investigate the workability or workability of the oyster shell mixed concrete, the slump change experiment of the unconsolidated concrete was performed according to the oyster shell replacement rate.

Low slump values mean poor workability or workability.

In the experiment, crushed oyster shell (type B) having a granulation rate of 2.1 and crushed oyster shell (type A) having a value of 2.7 were respectively changed in the range of 0 to 20 parts by weight of 100 parts by weight of the total aggregate, and the slump value immediately after the mixing was measured.

On the other hand, in order to determine the degree of workability improvement, the experiment was divided into the case where no admixture was added and the case where 0.3 parts by weight of AE reducing agent was added to 100 parts by weight of cement.

The results are shown in FIG. 1.

As can be seen from Figure 1 in the unconsolidated concrete without the AE reducing agent it can be seen that the slump is reduced by about 3cm as the replacement rate of the crushed oyster shell increases by 5%.

On the other hand, when the AE reducing agent is added, when the slump of 8 to 9 cm or more is satisfied, the replacement rate is approximately 10% for the A type, and the replacement rate is about 8% for the B type.

Experimental Example 2

Figure 2 shows the change in air volume according to the replacement rate of the crushed oyster shell.

In order to increase the durability of the concrete, it must have a proper amount of air.

Therefore, the air amount measurement test according to the air chamber pressure method was divided into A type crushed oyster shells, B type crushed oyster shells, and the case where AE water reducing agent was added to each of these samples, and the results are shown in FIG. 2.

 2, when the AE water reducing agent is not added, the air volume is almost constant at 2.0% or less regardless of the replacement rate of the oyster shell. This is because all of the air present inside the concrete is entrapped air that is mixed during bibeam and forming. This amount of air not only contributes to the increase in durability, but is also insufficient in marine concrete standards.

On the other hand, when 0.3 parts by weight of the AE reducing agent is added to 100 parts by weight of cement, it can be seen that a relatively good amount of air is shown. This is because the amount of air is greatly improved by the generation of entrained air according to the addition of the AE reducing agent.

In particular, it can be seen that in the case of the A-type concrete in which the AE water reducing agent is mixed, a good air amount is included up to a replacement rate of 10%.

Experimental Example 3

Figure 3 shows the change in bleeding rate according to the replacement rate of the crushed oyster shell.

Referring to FIG. 3, the change in the bleeding rate did not show a significant difference in the granulation rate of the crushed oyster shells and the presence or absence of the addition of an AE reducing agent.

When the replacement rate of oyster shell is 5% or more, the bleeding rate can be seen to be remarkably improved.

Experimental Example 4

Table 4 shows the change in setting time according to the replacement rate of the crushed oyster shell.

TABLE 4

% Substitution Whether admixture is added Condensation time (hour: minute) A type B type First closing Pouring temperature (℃) First closing Pouring temperature (℃) 0 radish 5:20 7:10 21.3 5:20 7:10 21.3 5 6:30 8:50 18.6 5:30 7:20 21.1 10 5:20 7:30 21.2 5:30 7:30 21.9 20 4:40 7:00 21.0 - - - 5 U 7:10 9:40 18.3 8:00 10:40 17.5 10 6:20 8:20 21.7 7:20 10:10 16.7 20 5:20 7:20 21.3 - - -

Figure 4 (a) is a graph showing the change in the set-up time according to the mixing of the crushed oyster shell when the type A oyster shell, Figure 4 (b) shows the change in the set-up time according to the mixing of the crushed oyster shell when the type B oyster shell will be.

One of the most important properties in the mechanical properties of concrete is strength expression, which can be evaluated by measuring the setting time of the concrete's setting and curing process.

The type of oyster shell, the replacement rate of the oyster shell and the presence or absence of the AE reducing agent were measured, and the curing time of each sample was measured and shown in Table 4 and FIG. 4.

From the hardening termination time, it can be seen that almost constant termination time is shown regardless of the type of oyster shell and the replacement rate. However, in case of adding AE reducing agent, the termination time was delayed about 1 hour regardless of the type of oyster shell and replacement rate. This result is generally a phenomenon that can occur in concrete to which the AE reducing agent is added.

As a result of the experiment, the end time of concrete was not significantly affected by the mixing rate of oyster shells and there were no problems such as abnormal condensation due to oyster shell input. Even if the crushed oyster shell is used within 20 parts by weight with respect to 100 parts by weight of the total fine aggregate as a substitute material for fine aggregate, there is no problem in the setting time.

Experimental Example 5

Table 5 shows the compressive strength, splitting tensile strength, and modulus of elasticity of hardened concrete mixed with oyster shell according to type, replacement rate, and use of AE reducing agent.

[Table 5] (Unit: kgf / cm ₂ )

Type of compound Compressive strength Split tensile strength Modulus of elasticity 3 days 7 days 28 days 7 days 28 days 28 days NNO 236 331 411 26.2 29.5 3.33 OA05 259 358 462 29.5 28.2 3.28 OA10 308 355 425 26.0 27.9 3.12 OA20 313 356 423 25.8 32.6 3.03 OB05 272 359 390 22.8 28.8 3.17 OB10 283 366 434 28.3 27.1 3.12 RA05 253 336 414 - - 3.16 RA10 247 314 349 - - 2.86 RA20 311 363 415 - - 2.95 RB05 239 292 380 - - 2.94 RB10 292 365 423 - - 3.11

Figure 5 (a) is a graph showing the compressive strength of the concrete mixed with oyster shell without adding the AE reducing agent.

Figure 5 (b) is a graph showing the compressive strength of the concrete mixed with oyster shell added to the AE water reducing agent.

In FIG. 5 (a), the compressive strength at the early age (3 days) of the concrete mixed with oyster shells without the AE water reducing agent was higher than that of the NNO standard mixture without oyster shells. As this increases, the compressive strength tends to increase.

The compressive strength at 28 days of age is higher than that of NNO, except in the case of 5% mixed oyster shell of type B (OB05).

In FIG. 5 (b), the compressive strength at the early age (3 days) of the concrete mixed with oyster shells added with the AE water reducing agent was also higher than that of the NNO standard mixture without mixing the oyster shells, but the age was increased. As the result, the compressive strength of the NNO standard formulation decreases or approaches. This is due to the effect of entrained air by the addition of AE reducing agent, not due to the replacement rate of the crushed oyster shell.

Experimental Example 6

6 is a graph showing the change in tensile strength according to the mixing of the oyster shell.

In FIG. 6, it was difficult to find a distinct tendency due to the mixing of oyster shells as in the compressive strength expression, but overall, the tensile strength at early age (3 days) increased with mixing oyster shells. However, the tensile strength at 28 days tended to be slightly lower than the tensile strength of the NNO standard formulation.

Experimental Example 7

Figure 7 shows the change in the elastic modulus of the concrete according to the oyster shell mixing.

In FIG. 7, it can be seen that the elastic modulus of the concrete generally decreases as the replacement rate of the oyster shell increases, since the elastic modulus of the oyster shell is smaller than that of the fine aggregate.

As described above, the concrete according to the present invention has the same physical properties as those of the conventional concrete using only sand as fine aggregate, and can only prevent the effect of resource utilization and environmental pollution by recycling the oyster shell, which is a coastal waste. Rather, it is effective in reducing construction costs by lowering the costs used to manufacture concrete.

1 is a graph showing a slump change according to the replacement rate of the crushed oyster shell,

2 is a graph showing the change in air volume according to the replacement rate of the crushed oyster shell,

3 is a graph showing the change in bleeding rate according to the replacement rate of the crushed oyster shell,

4 is a graph showing the change in setting time according to the replacement rate of the crushed oyster shell,

(a) is for oyster shell A type,

(b) is a graph of oyster shell B type,

5 is a graph showing the change in compressive strength according to the replacement rate of oyster shell,

(a) is the absence of admixtures,

(b) is a graph in the case of admixture addition,

Figure 6 is a graph showing the change in tensile strength according to the replacement rate of oyster shell

7 is a graph showing the change in the elastic modulus of concrete according to the oyster shell replacement rate.

Claims (6)

In concrete prepared by mixing cement, fine aggregate, coarse aggregate, admixture and water, the fine aggregate includes a crushed oyster shell having a granulation ratio of 2.1 to 2.7, wherein the crushed oyster shell is 5 of 100 parts by weight of the total fine aggregate. To 10 parts by weight, characterized in that the admixture is mixed with oyster shells, characterized in that 0.3 parts by weight of AE reducing agent with respect to 100 parts by weight of cement. delete delete Placing the oyster shell in a drying furnace and drying by heating at 100 to 120 ° C .; Grinding the dried oyster shell into oyster shells having a granulation ratio of 2.1 to 2.7; The crushed oyster shell is made of a process of mixing with cement, fine aggregate, coarse aggregate, admixture, and water. In the mixing process, the admixture is 0.3 parts by weight of an AE reducing agent based on 100 parts by weight of cement, and the crushed oyster shell is total Method for producing concrete mixed oyster shell, characterized in that 5 to 10 parts by weight of 100 parts by weight of the aggregate aggregate. delete delete