KR100874210B1 - High elasticity and high strength structural concrete using limestone refuse - Google Patents

Abstract

A high elastic-high intensity structural concrete using limestone debris is provided to improve a performance of a concrete structure by promoting a coefficient of elasticity and evaluating a coefficient of elasticity of a compressive strength according to the combination variable to the concrete using the limestone debris as thick aggregate. A high elastic-high intensity structural concrete using limestone debris comprises water, cement, thick aggregate, and a blending material. The thick aggregate is limestone debris. The limestone debris contains calcium carbonate of 65~85 weight%. A water-binder ratio of the high elastic-high intensity structural concrete using the limestone debris is 20~40%.

Description

High elasticity and high strength structural concrete using limestone refuse}

The present invention relates to a high-elasticity-high strength structural concrete utilizing limestone waste-rock in the structural concrete comprising water, cement, coarse aggregate, and admixture, wherein the coarse aggregate is limestone waste-rock.

Recently, the demand for high-strength concrete is increasing due to the rapid growth of the construction industry and the increase in the size of the structure. In general, concrete is composed of a composite material hardened by kneading aggregates such as sand and gravel with cement and water. In high-strength concrete, strength of aggregates such as gravel itself may be a problem. However, the problem of depletion of natural aggregates such as gravel among the components constituting the concrete is on the rise, the replacement aggregate that can replace the natural aggregate is urgently required.

On the other hand, limestone is an indispensable resource in the cement industry, but since the cement industry generally uses high-quality limestone, low-quality limestone waste-rock produced in mines is left unattended, causing great problems in aesthetic or environmental aspects. have.

In general, the elastic modulus of concrete is affected by the material and strength of concrete. In the same type of concrete, the higher the compressive strength, the larger the elastic modulus. Therefore, when the elastic modulus is large, high strength concrete can be obtained. On the other hand, the elastic modulus of concrete corresponds to an important material variable required in the design, analysis, or sag control of the structure. It is becoming. And these functional expressions are regressions based on experimental values and contain a lot of uncertainty. Therefore, systematic re-establishment of modulus of elasticity is necessary for the technical development of concrete industry and the practical use of high strength concrete. In fact, the elastic modulus equations of the US ACI 318-99 and ACI 363 norms and the AIJ norms of the Japanese AIJ norm, which are currently applied in the design or analysis of reinforced concrete structures in Korea, are overestimated than actual values for high strength concrete above 40 MPa. It has been pointed out.

An object of the present invention created to solve the above problems is as follows.

First, by using high elasticity-high strength concrete using the limestone waste-rock as a coarse aggregate as a structural member, it is an object of the present invention to achieve economical construction by simultaneously saving resources and reducing environmental load.

Second, by evaluating the elastic modulus of each compressive strength according to the mixing parameters for concrete using limestone waste-rock as coarse aggregate, the elastic modulus is improved to improve the performance of concrete structures.

In order to solve the above problems, the present invention is a structural concrete comprising water, cement, coarse aggregates, admixtures, the coarse aggregate is a high elasticity-high strength structural concrete utilizing limestone waste-rock, characterized in that the limestone waste-rock To provide.

In particular, in the case of using limestone waste-rock containing 65 to 85% by weight of calcium carbonate, high elasticity-high strength concrete can be obtained by increasing the modulus of elasticity, and in addition, the strength is controlled by controlling the water-bonding ratio and the type and content of the admixture. High strength concrete of 40 ~ 100MPa can be obtained.

According to the present invention as described above is expected the following effects.

First, by using high-strength concrete using limestone waste-rock as coarse aggregate as a structural member, it is possible to achieve economical construction by simultaneously saving resources and reducing environmental load.

Second, by evaluating the elastic modulus according to the compressive strength of the high-strength concrete using the limestone waste-rock as coarse aggregate, it is possible to improve the performance of the concrete structure by improving the elastic modulus.

Hereinafter, the present invention will be described in detail with reference to preferred examples and experimental examples.
High-elasticity-high strength structural concrete utilizing the limestone waste-rock of the present invention is characterized in that in the structural concrete composed of water, cement, coarse aggregate, admixture, the coarse aggregate is limestone waste-rock.
Here, limestone waste-rock can be used containing 65 to 85% by weight of calcium carbonate.
In addition, the high-elasticity-high strength structural concrete using the limestone waste-rock of the present invention has a water-bonding ratio of 20 to 40%, the coarse aggregate has a weight of 900 to 1100kg / ㎥, and the admixture is a fly ash or a substitution rate of 15 to 30% It is characterized in that any one of 30 to 50% blast furnace slag fine powder or silica fume having a substitution rate of 7 to 15%. In this case, the admixture may be used by selecting either fly ash, blast furnace slag fine powder or silica fume.

In the present invention, in order to manufacture high elastic-high strength structural concrete using limestone waste-rock, concrete specimens were prepared according to the type and composition of coarse aggregate, and the concrete compressive strength and elastic modulus were measured. Here, the compressor was attached to the specimen in accordance with ASTM C469 and subjected to two iterations up to 40% of the maximum compressive strength using a 200 ton UTM, and a secant coefficient for strength corresponding to 40% of the maximum compressive strength. modulus was used to measure the elastic modulus of concrete.

The modulus of elasticity enhancement used in the present invention means a value obtained by dividing the measured modulus of elasticity by the modulus of elasticity according to the ACI 363 standard.

Cement was used as a material for concrete mixing. One type of cement was used as a cement, and the admixture was a fly ash having a specific gravity of 2.2 and a powder degree of 3600㎠ / g, a blast furnace slag with a specific gravity of 2.9 and a powder degree of 3600㎠ / g, crystalline. Silica fume of the product was used. In addition, coarse aggregates are generally used granite aggregates used in ready-mixed concrete and limestone waste-rock with a certain amount of calcium carbonate. The coarse aggregates have a maximum size of 20 mm and 25 mm.

[ Example 1 Modulus of Elastic Modulus According to Type of Coarse Aggregate

First, in order to grasp the elastic modulus characteristics of the concrete according to the type of coarse aggregate, in the present invention, the concrete produced according to the mixing parameters as shown in [Table 1-1] in the range of the design strength 40 ~ 100MPa, respectively, 7 days, 14 days The modulus of elasticity was evaluated for days and 28 days, and the modulus of elasticity enhancement was calculated.

[Table 1-1] Mixing Parameters of Concrete

Water-binding ratio (%) 20, 25, 30, 35, 40 Coarse aggregate volume (G _v ) 0.34, 0.36, 0.38 Unit quantity (kg / ㎥) 155, 165 Coarse Aggregate Type Limestone, granite

Limestone waste-rock used here has the chemical composition shown in [Table 1-2].

[Table 1-2] Chemical Composition of Limestone Waste Rocks

division Chemical composition (%) Converted CaCO ₃ (%) LOI SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO SO ₃ K ₂ O Na ₂ O Ingredient 31.76 20.73 2.79 1.82 39.98 1.89 0.21 0.65 0.04 71.35

As a result, the modulus of elastic modulus increased by the change of coarse aggregate volume did not show a constant tendency, and the modulus of elastic modulus showed a higher modulus of elastic modulus than that of granite when the type of coarse aggregate was limestone. In this case, when the coarse aggregate volume is 0.36, the experimental results of the elastic modulus enhancement rate for each rock type according to the water-bonding material ratio are summarized as in [Table 1-3].

[Table 1-3] Modulus Enhancement Rate by Coarse Aggregate Types

division Water-binding ratio (%) Unit quantity (kg / ㎥) Coarse Aggregate Type % Improvement, experimental value / ACI 363 7 days 14 days 28 days No.1 20    165   limestone 19.0 20.1 21.0 No.2 25 24.2 29.4 27.4 No.3 30 22.9 26.1 23.5 No.4 35 19.2 21.7 24.4 No.5 40 25.5 24.7 25.3 No.6 20   granite 2.0 4.3 0.1 No.7 25 9.2 6.8 3.9 No.8 30 8.0 4.8 7.0 No.9 35 6.0 11.0 7.2 No.10 40 5.5 8.8 8.9

When limestone and granite are used as coarse aggregates in [Table 1-3], the modulus of elastic modulus increases by age according to the type of coarse aggregate is shown in FIG. Here, Figures 1 (a), (b) and (c) show the modulus of elasticity enhancement at 7, 14 and 28 days of age, respectively. As shown in (a) to (c) of Figure 1, when the limestone waste-rock is used, it is possible to obtain a higher modulus of elasticity than ACI 363 Code.

[ Example 2 Properties of Compressive Strength and Elastic Modulus of Concrete According to Calcium Carbonate Content

In order to understand the compressive strength and elastic modulus characteristics of concrete according to the calcium carbonate content of coarse aggregate, concrete was prepared to have the formulation as shown in Table [2-1].

[Table 2-1] Mixing Parameters of Concrete

Water-binding ratio (%) Fine Aggregate Rate (%) Unit material amount (kg / ㎥) Unit quantity cement Silica fume 20 36.0  165 759 66 25 44.0 614 46 30 41.0 550 - 35 43.0 471 -

In the above formulation, the compressive strength and modulus of elasticity of concrete were measured at 3, 7, 14, and 28 days, respectively, for coarse aggregate samples having coarse aggregate types and component contents as shown in Table [2-2]. The calcium carbonate content of the limestone waste-rock used here is on the order of 63%, 75% and 93% by weight, respectively.

[Table 2-2] Chemical Composition by Sample

Sample Name Chemical composition (%) SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO SO ₃ K ₂ O CaCO ₃ granite 70.5 14.3 1.6 1.6 0.6 0.2 5.1 - Limestone NO.1 2.30 0.7 0.3 52.1 1.0 0.0 0.1 93.0 Limestone NO.2 16.5 3.6 2.2 41.7 1.6 0.4 0.9 74.4 Limestone NO.3 23.5 5.9 4.5 35.1 2.9 0.1 1.0 62.7

The compressive strength and modulus of elasticity of each concrete at 28 days of age are shown in [Table 2-3].

[Table 2-3] Concrete Compressive Strength and Modulus of Elasticity Improvement by Samples at 28 Days of Age

Water-binding ratio (%) Compressive strength (MPa) / modulus of elasticity (GPa) granite Limestone NO.1 Limestone NO.2 Limestone NO.3 20 96.2 / 37.5 94.5 / 45.2 95.9 / 44.0 100.0 / 43.7 25 78.6 / 35.3 77.5 / 43.1 78.0 / 42.8 79.7 / 42.0 30 59.8 / 34.5 61.0 / 40.9 60.5 / 39.2 63.2 / 38.4 35 52.1 / 32.2 50.8 / 37.1 51.5 / 35.5 53.8 / 34.1

Experimental results show higher modulus of elastic modulus in all samples using limestone waste-rock than in the case of coarse aggregates. Therefore, in consideration of the ease of limestone waste-rock acquisition according to the calcium carbonate content, limestone waste-rock containing 65 to 85% by weight of calcium carbonate will be used as coarse aggregate. In addition, considering the relationship with the compressive strength of the concrete, preferably, limestone waste rock containing 75% by weight of calcium carbonate may be used as a coarse aggregate. At this time, calcium carbonate means the weight of calcium carbonate equivalent.

[ Example 3 ] Miscible  Modulus of Elasticity according to Type and Substitution Rate

In this experiment, tests were planned as shown in Table 3-1 to understand the characteristics of the modulus of elasticity according to the type and the substitution rate of the admixture. Coarse aggregate was used as limestone, and the coarse aggregate volume (G _v ) was 0.36.

[Table 3-1] Mixing Parameters of Concrete

Water-binding ratio (%) 25, 35 Fly Ash Substitution Rate (%) 15, 30 Unit quantity (kg / ㎥) 165 Blast furnace slag fine powder substitution rate (%) 30, 50 Silica fume substitution rate (%) 7.5, 15

The results of the experiment are summarized in [Table 3-2] and FIG.

[Table 3-2] Enhancement Rate of Elastic Modulus According to Kinds and Substitution Rate of Admixtures

division Unit quantity (kg / ㎥) Class of Admixtures Admixture substitution rate (%) Promotion rate (%) 7 days 14 days 28 days 25% water-binding 35% water-binding ratio 25% water-binding 35% water-binding ratio 25% water-binding 35% water-binding ratio No.1    165 OPC 0 24.2 30.7 30.5 26.3 23.1 27.3 No.2 Fly ash 15 22.5 26.1 25.6 27.6 24.6 24.7 No.3 30 23.8 32.3 23.6 29.8 22.4 31.7 No.4 Blast furnace slag powder 30 24.7 20.9 27.4 27.5 25.2 23.6 No.5 50 25.4 21.4 23.6 26.3 20.4 26.3 No.6 Silica fume 7.5 17.1 20.4 18.7 22.4 13.1 20.7 No.7 15 8.2 17.2 10.9 16.2 9.2 16.22

When the fly ash is used as shown in (a) to (c) of Figure 2, it can be seen that the elastic modulus is enhanced according to the amount of fly ash used. In the case of using blast furnace slag powder, when the water-bonding material ratio is high, the modulus of elasticity is slightly lower than that of the fly ash. However, when the water-binding material ratio is low, the elastic modulus is equivalent to that of the fly ash. Indicated.

[ Example 4 Elastic Modulus Characteristics of Coarse Aggregate Consumption

In this experiment, the experiment was planned as shown in [Table 4-1] to understand the characteristics of elastic modulus according to the amount of coarse aggregate. As coarse aggregate used here, limestone waste-rock composed of the components shown in [Table 1-2] was used.

[Table 4-1] Mixing Parameters of Concrete

Water-binding ratio (%) 25, 35 Fly Ash Substitution Rate (%) 15 Unit quantity (kg / ㎥) 165 Coarse aggregate weight (kg / ㎥) 900, 1000, 1100

Compressive strength and modulus of elasticity of concrete were measured at 7, 14 and 28 days of age, respectively. At this time, the change of the modulus of elasticity enhancement according to the amount of limestone aggregate is summarized in [Table 4-2] and FIG.

[Table 4-2] Modulus of Elasticity Improvement According to Limestone Aggregate Usage

division Water-binding ratio (%) Formulation Variables Promotion rate (%) Unit quantity (kg / ㎥) Admixture (%) Weight (kg / ㎥) 7 days 14 days 28 days No.1  35   165  Fly Ash 15 900 27.7 24.2 25.8 No.2 1000 28.4 24.2 27.6 No.3 1100 35.2 38.2 34.5 No.4  25 900 32.8 22.5 22.2 No.5 1000 32.9 24.5 24.1 No.6 1100 33.0 26.8 23.7

As shown in [Table 4-2] and FIG. 3, the use of limestone aggregate showed an improvement in modulus of elasticity. In particular, when the amount of limestone aggregate used is 1100kg / ㎥, it can be seen that the modulus of elasticity was improved up to 34.5%. This is more pronounced here when the water-binding ratio is 35%.

While the invention has been described in connection with the preferred embodiment as mentioned above, various modifications and variations are possible without departing from the spirit of the invention. Therefore, the claims of the present invention include modifications and variations that fall within the true scope of the invention.

1 is a graph showing the elastic modulus enhancement rate for each age according to the type of coarse aggregate.

2 is a graph showing the modulus of elasticity enhancement according to the type and the substitution rate of the admixture.

Figure 3 is a graph showing the modulus of elasticity increase according to the limestone aggregate usage.

Claims (5)

In the structural concrete, including water, cement, coarse aggregate, admixture, The coarse aggregate is high elasticity-high strength structural concrete utilizing limestone waste-rock, characterized in that limestone waste-rock. In claim 1, The limestone waste-rock is a high-elasticity-high strength structural concrete utilizing limestone waste-rock, characterized in that containing 65 to 85% by weight of calcium carbonate. The method of claim 1 or 2, The high-elasticity-high strength structural concrete using the limestone waste-rock is a high-elasticity-high strength structural concrete using the limestone waste-rock, characterized in that the water-bonding material ratio is 20 to 40%. The method of claim 1 or 2, The admixture is a high-elasticity-high strength structural concrete using limestone waste-rock, characterized in that any one of fly ash having a substitution rate of 15 to 30% or fine blast furnace slag of substitution rate of 30 to 50% or silica fume having a substitution rate of 7 to 15%. The method of claim 1 or 2, The coarse aggregate is high elasticity-high strength structural concrete using limestone waste-rock, characterized in that the weight is 900 ~ 1100kg / ㎥.

Images