KR20110102749A - Cement - Google Patents

Abstract

The present invention relates to an ultra-low calorific cement composition developed to maintain high strength while being useful for a concrete structure in which the temperature rise due to the heat of hydration generated during the hydration reaction is greatly reduced and the section thickness of the member is sensitive to the heat of hydration. In the present invention, incorporating amorphous silica and coal ash into the low calorific cement, but having a composition ratio of 30 parts by weight of low heat cement, 30 parts by weight of amorphous silica and 40 parts by weight of coal ash based on 100 parts by weight of the total cement composition. The cumulative heat of hydration is less than 35cal / g is provided an ultra-low calorific cement composition characterized in that it has a compressive strength of 20 ~ 30MPa 28 days.

Description

Ultra-low Calorie Cement Composition {Cement}

The present invention relates to an ultra-low heat cement composition, specifically, the temperature rise due to the heat of hydration generated during the hydration reaction is greatly reduced, so that the cross-sectional thickness of the member can be useful for concrete structures that are sensitive to the heat of hydration, while maintaining high strength. It relates to an ultra low heat cement composition developed to maintain.

Recently, as the demand for investment in SOC has been increased, the size of civil and building structures has been accelerated, so that the large structures, sub-structures such as bridges and bridges of long bridges, large ramens, high-rise buildings Mass concrete structures with large member sizes, such as underground structures such as LNG foundation tanks, are being constructed.

In constructing such a mass concrete structure, the most important factor that determines the quality and construction period of the entire concrete is cracking that occurs when the temperature stress inside the concrete is greater than or equal to the tensile strength by the heat of hydration of the cement. The heat of hydration of mass concrete depends on the amount of cement unit and the heat of hydration of cement.

The hydration calorific properties of cement are expressed by the hydration calorific value and the hydration calorific rate, and the cement concrete for mass concrete should generate hydration heat gently over the entire time while having a small total hydration calorific value. In other words, the cumulative heat of hydration must be small.

In order to reduce the heat of hydration, conventionally, low heat cements such as medium heat cement, blast furnace cement, four low heat portland cements of KS standard KS L 5201, low heat portland cement specified in ASTM Type IV, and the like are proposed. come.

However, in advanced countries, low heat cements with lower hydration calorific value than the low heat cements of ASTM Type IV have been continuously developed in the 1980s for the purpose of shortening the air, placing large amounts of concrete, and reducing construction costs. These recent low heat cement compositions have generally been developed in the form of:

1) A mixture of low heat cement and ordinary Portland cement.

2) A mixture of blast-furnace slag with ordinary Portland cement.

3) A mixture of fly ash in ordinary Portland cement.

4) A mixture of blast-furnace slag and fly ash, usually in Portland cement.

In general, the heat of dissolution of ordinary Portland cement is 604.8 cal / g, and the heat of dissolution of blast furnace slag and fly ash is 585.6 cal / g and 221.04 cal / g, respectively, which is lower than that of ordinary Portland cement. Therefore, when blast furnace slag and fly ash are usually mixed in Portland cement, the heat of hydration decreases according to the mixing ratio. However, when the blast furnace slag or fly ash is mixed with portland cement, the heat of hydration can be reduced as the amount of addition increases, but the initial strength and the 28-day strength are greatly reduced due to the delay in hydration.

In addition, when the low heat cement is usually mixed with portland cement, the compressive strength is good, but the heat of hydration is higher than that of the low heat cement alone because the heat of dissolution is high.

Moreover, the conventional low heat generation cement composition developed so far shows a relatively high heat of hydration of about 60 cal / g, which is 28 days of cumulative heat of hydration, and in most cases, a separate cooling device is used when mass concrete is poured. Therefore, the development of "ultra" low heat cement composition capable of expressing the required compressive strength while lowering the cumulative heat of hydration for 28 days is urgently requested.

The present invention has been developed in accordance with the above needs, specifically provides a "super" low heat cement composition having a cumulative hydration heat of 35 cal / g or less after the 28-day cured age and 20 ~ 30 MPa age of 28 days compression strength It aims to do it.

In order to achieve the above object, in the present invention, while mixing amorphous silica and coal ash in the low-heating cement, the composition ratio of 30 parts by weight of low-heat cement, 30 parts by weight of amorphous silica and 40 parts by weight of coal ash with respect to 100 parts by weight of the total cement composition It is configured so that the age of 28 days cumulative heat of hydration 35cal / g or less is provided with an ultra-low calorific cement composition characterized in that it has a compressive strength of 20 ~ 30MPa 28 days.

Amorphous silica in the invention has a degree of 4000~4300cm ² / g powder, coal ash is preferred to have a fineness of 3,000~4,500cm ² / g, the low heat generating cement the four kinds of KS Standard KS L 5201 The low heat Portland cement is preferably composed of a bellite content of 40 parts by weight or more (specifically 45 to 50 parts by weight) with respect to 100 parts by weight of the four types of portland cement. In particular, the four types of low-heat Portland cement of the KS standard KS L 5201 is 49 parts by weight of bellite, 28 parts by weight of aluminate, 6 parts by weight of aluminate, 12 parts by weight of ferrite, and inorganic sulfate based on 100 parts by weight of the total amount of low heat Portland cement. It may have a composition of 5 parts by weight.

The ultra-low calorific cement composition of the present invention has a very low exothermic performance by maintaining the 28-day compressive strength of 20 to 30 MPa while maintaining the 28-day cumulative heat of hydration of 35 cal / g or less. This can be very useful for many applications that may result.

1 and 2 are histograms of the results of the 28-day compressive strength measurement and the 28-day cumulative hydration heat measurement of the comparative examples, respectively.
3 and 4 are bar graphs of the results of measuring the 28-day compressive strength and the 28-day cumulative hydration heat measurement results for the comparative examples and the examples of the present invention, respectively.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Although the present invention has been described with reference to the embodiments shown in the drawings, this is described as one embodiment, whereby the technical spirit of the present invention and its core configuration and operation are not limited.

In the present invention, ultra-low heat generation comprising four low-heat Portland cement of KS standard KS L 5201, amorphous silica and coal ash, 30 parts by weight of low-heat cement, 30 parts by weight of amorphous silica and 40 parts by weight of coal ash based on 100 parts by weight of the cement composition. Cement compositions are provided.

In particular, in the ultra-low calorific cement composition of the present invention, the four low-heat portland cements of the current KS standard KS L 5201 have a content of bellite (2CaO®SiO ₂ / or less, abbreviated as "C ₂ S"). As the content of 40 parts by weight or more based on 100 parts by weight of the four types of Portland cement, it is preferable to use the content of 45 to 50 parts by weight based on 100 parts by weight of the bellite four types of Portland cement.

More specifically, four types of low heat Portland cement of KS standard KS L 5201 contained in the ultra low heat cement composition of the present invention are manufactured from clinker obtained by calcining a raw material containing limestone and clay at high temperature (about 1450 ° C.). Alite (alite: 3CaO.SiO ₂ / or less, abbreviated as "C ₃ S"), bellite, aluminate (aluminate: 3CaO.Al ₂ O ₃ / or less, abbreviated as "C ₃ A." Ferrite (ferrite: 4CaO · Al ₂ O ₃ · Fe ₂ O ₃ / hereinafter, abbreviated as “C ₄ AF”), and in some cases, inorganic sulfate may be further included. Has a composition of 1.

Belllight
(2CaOSiO ₂ ) Alite
(3CaOSiO ₂ ) Aluminate
(3CaOAl ₂ O ₃ ) ferrite
_{(4CaO · Al 2 O 3 ·} Fe 2 O 3) weapon
sulfate Low heat
Portland
cement 49 28 6 12 5

Each numerical value of Table 1 means parts by weight of 100 parts by weight of four kinds of low heat Portland cement of KS standard KS L 5201.

However, the four types of low heat Portland cement of the KS standard as described above has a limit of low compressive strength expression because of its large content of bellite (C ₂ S). In order to solve this problem, in the present invention, by mixing amorphous silica and coal ash in four kinds of low heat Portland cement of KS standard having a bellite content of 40 parts by weight or more as described above, very low cumulative heat of hydration (less than 35 cal / g of age 28 days cumulative hydration heat) ), While having an excellent compressive strength (age 28 days compressive strength of 20 ~ 30MPa), "ultra" low heat cement composition was implemented.

In the ultra-low calorific cement composition of the present invention, the amorphous silica is preferably included in 30 parts by weight based on 100 parts by weight of the ultra low calorific cement composition. If the amorphous silica is less than 30 parts by weight, the reduction of the heat of hydration is small, and if it exceeds 30 parts by weight, the initial strength and the 28-day strength is reduced. Therefore, in the present invention, the amorphous silica is included in 30 parts by weight based on 100 parts by weight of the ultra-low calorific cement composition.

On the other hand, amorphous silica has a different activity index according to the powder degree, the higher the powder index, the higher the activity index, the higher the initial strength and the 28-day strength is expressed, but also has a problem that the 28-day cumulative heat of hydration also increases. Therefore, in the present invention is 4000 ~ 5000cm amorphous silica preferably has a fineness of ² / g, and, in order to reduce the cost of grinding to have a fineness of 4000~4300cm ² / g is more preferred.

In the ultra-low calorific cement composition of the present invention, the coal ash is preferably included in an amount of 40 parts by weight based on 100 parts by weight of the ultra low calorific cement composition. Although coal ash has a heat reduction effect of hydration from 10 parts by weight or more, it must be contained in 40 parts by weight in order to expect effective heat reduction effect. In addition, as the amount of coal ash is increased, the effect of reducing heat of hydration is also increased. However, since the expression of initial strength and 28-day strength is very low as the amount of coal ash is added, the coal ash is 40 parts by weight with respect to 100 parts by weight of the ultra-low calorific cement composition. It is contained. In addition, in this invention, it is preferable that the powdery degree of coal ash is 3,000-4,500 cm <^2> / g.

The ultra-low calorific cement composition of the present invention having such a composition has an age of 28 days of cumulative heat of hydration of 35 cal / g or less and an age of 28 days of compressive strength of 20 to 30 MPa.

The following describes in more detail the features and configuration of the present invention through various embodiments and comparative examples of the present invention. However, the present invention is not limited to these examples.

First, Table 2 is the composition of the comparative example was carried out a comparative test to confirm the effect of mixing the amorphous silica and coal ash, respectively, in the known low-heating cement.

Low fever
cement Amorphous
Silica Coal ash W / C 28 days
Compressive strength
(MPa) 28 days
Cumulative Heat
(cal / g) Comparative Example 1 100 - - 0.5 41.97 68.4 Comparative Example 2 70 30 - 0.5 48.53 78.4 Comparative Example 3 50 50 - 0.5 44.35 70.6 Comparative Example 4 30 70 - 0.5 37.55 62.4 Comparative Example 5 90 - 10 0.5 33.25 66.5 Comparative Example 6 70 - 30 0.5 20.03 48.7 Comparative Example 7 50 - 50 0.5 11.25 27.9

Each numerical value of Table 2 means parts by weight of each component based on 100 parts by weight of the total cement composition, and W / C means water / cement ratio. In addition, "low heat cement" means four low heat portland cements of the conventional KS standard KS L 5201.

As described above, after incorporating amorphous silica or coal ash into four kinds of low heat Portland cements of the conventional KS standard KS L 5201, the compressive strength and the cumulative heat of hydration were measured for 28 days. The compressive strength test method of cement mortar) was carried out, and the heat of hydration was measured according to KS L 5121 (Test method of hydration heat of Portland cement).

1 and 2 show bar graphs of the results of measuring the 28-day compressive strength and the 28-day cumulative hydration heat for the comparative examples of Table 2, respectively. As can be seen from Table 2, Fig. 1 and Fig. 2 above, in the case of four conventional low-temperature Portland cements of KS standard KS L 5201, which are not containing any amorphous silica and coal ash (Comparative Example 1), 28 days Compressive strength and cumulative heat of hydration were measured at 41.97 MPa and 68.4 cal / g, respectively.

However, Comparative Example 2, Comparative Example 3, and Comparative Example 4, in which amorphous silica was mixed with four conventional low-temperature Portland cements of KS standard KS L 5201 based on 100 parts by weight of cement composition, respectively, 30, 50, and 70 parts by weight, respectively. As a result of measuring the 28-day compressive strength and cumulative heat of hydration, the 28-day compressive strength of Comparative Example 2 mixed with 30 parts by weight of amorphous silica showed 48.53 MPa higher than the 28-day compressive strength of the low calorific cement of Comparative Example 1 . However, as the amount of amorphous silica increased, the compressive strength decreased.

On the other hand, in the 28-day cumulative heat of hydration, it decreases as the amount of amorphous silica is increased, and 78.4 cal / g, 70.6 cal / g, respectively, when the amorphous silica is mixed with 30, 50, and 70 parts by weight based on 100 parts by weight of the cement composition. The cumulative heat of hydration of 62.4 cal / g was shown. As described above, in the case of the amorphous silica, as the content increases, the effect of reducing the heat of hydration becomes larger, but the decrease becomes smaller. On the other hand, it can be seen that the phenomenon that the compressive strength decreases as described above occurs. Therefore, the amorphous silica is preferably included in 30 parts by weight based on 100 parts by weight of the ultra-low heating cement composition.

On the other hand, with respect to coal ash, Comparative Example 5, Comparative Example 6 in which coal ash was mixed with four kinds of low heat Portland cements of KS standard KS L 5201, which are known in the related art, based on 100 parts by weight of cement composition, respectively. As a result of measuring the 28-day compressive strength and the cumulative heat of hydration for Comparative Example 7, when the coal ash contained 10, 30 and 50 parts by weight, respectively, the 28-day compressive strength was 33.25 MPa, 20.03 MPa and 11.25 MPa, respectively. The cumulative heat of hydration for 28 days was 66.5 cal / g, 48.7 cal / g and 27.9 cal / g, respectively. That is, it can be seen that the compressive strength and the heat of hydration are greatly reduced as the content of coal ash is increased.

In particular, in the case where 10 parts by weight of coal ash is mixed (Comparative Example 5), the cumulative hydration heat is lower than that of Comparative Example 1, and it can be seen that the coal ash exhibits a greater heat reduction effect than amorphous silica. However, in the case of Comparative Example 5, the compressive strength of 28 days was lower than that of Comparative Example 1, and it was found that there was a problem that the compressive strength also greatly decreased when the content of coal ash was increased.

Following the preliminary comparative experiment according to the amorphous silica and coal ash as described above was performed a comparative test for the embodiment according to the present invention, the results are summarized in Table 3.

Low fever
cement Amorphous
Silica Coal ash W / C 28 days
Compressive strength (MPa) 28 days
Cumulative heat of hydration (cal / g) Comparative Example 8 60 30 10 0.5 45.98 65.8 Comparative Example 9 50 30 20 0.5 41.63 57.3 Comparative Example 10 40 30 30 0.5 36.17 44.8 Example 1 30 30 40 0.5 24.12 34.3 Comparative Example 11 20 30 50 0.5 16.74 30.2

Each numerical value of Table 3 means parts by weight of each component with respect to 100 parts by weight of the total cement composition, W / C means the water / cement ratio. In addition, "low heat cement" means four low heat portland cements of the conventional KS standard KS L 5201.

Thus, Comparative Examples 8 to 10, Example 1, and Comparative Example 11 were also subjected to a compressive strength test according to KS L 5105 (Test method for compressive strength of hydraulic cement mortar), and KS L 5121 (Test method for hydration heat of portland cement). ), The heat of hydration was measured, and the 28-day compressive strength and cumulative heat of hydration were measured.

3 and 4 show bar graphs of the results of measuring the 28-day compressive strength and the 28-day cumulative hydration heat for the Comparative Examples and Examples of Table 3, respectively.

Comparative Example 8 includes 60 parts by weight of low-heat cement, 30 parts by weight of amorphous silica, and 10 parts by weight of coal ash, based on 100 parts by weight of the total cement composition, as shown in FIGS. 3, 4, and 3, and age 28-day compressive strength. Is 45.98 MPa, which is higher than the conventional low heat cement containing no amorphous silica and coal, and the cumulative heat of hydration was 65.8 cal / g, slightly lower than the conventional low heat cement containing no amorphous silica and coal. , Higher than 35 cal / g for the purpose of the present invention.

Comparative Examples 9, 10, Example 1 and Comparative Example 11 also fixed the content of amorphous silica to 30 parts by weight relative to 100 parts by weight of the total cement composition, respectively, and the addition amount of coal ash to 20, 30, 40 and 50 parts by weight As shown in FIGS. 3, 4, and 3, in Comparative Examples 8, 9, and 10, the 28-day cumulative heat of hydration was 57.3 cal / g and 44.8 cal / g, respectively, and the 28-day cumulative heat of hydration was increased with the addition of coal ash. Decreased. However, in the case of Comparative Examples 8, 9, and 10, the cumulative heat of hydration for 28 days was higher than the value of 35 cal / g, which is the object of the present invention, and thus it was found to be inappropriate.

On the other hand, in Example 1 corresponding to the present invention, the 28-day cumulative hydration heat was 34.3 cal / g, and the 28-day cumulative hydration heat was lower than 35 cal / g, which is the object of the present invention. It was suitable to show 24.12 MPa within the range of 20-30 MPa of 28-day compressive strength aimed at by this invention. However, in Comparative Example 11, the cumulative heat of hydration for 28 days was 30.2 cal / g, which is lower than 35 cal / g, which is the purpose of the present invention, but the 28-day compressive strength was 16.74 PMa lower than 20 to 30 MPa.

As described above, in the present invention, incorporating amorphous silica and coal ash into four kinds of low heat portland cement of KS standard KS L 5201, 30 parts by weight of low heat cement, 30 parts by weight of amorphous silica and 40 parts by weight of coal ash based on 100 parts by weight of the cement composition. By the cement composition having a composition ratio, the “ultra” low heat cement composition having a cumulative heat of hydration of 35 cal / g for 28 days and having a compressive strength of 20 to 30 MPa for 28 days was realized.

Claims (3)

Incorporating amorphous silica and coal ash into the low calorific cement, 30 parts by weight of low heat cement, 30 parts by weight of amorphous silica and 40 parts by weight of coal ash, based on 100 parts by weight of the total cement composition, the heat of hydration 35cal / g 28 days Ultra-low calorific cement composition, characterized in that it has a compressive strength of 20 ~ 30MPa below 28 days.
The method of claim 1,
Amorphous silica is 4000~4300cm has a view of the ² / g powder, coal ash is a ultra-low heat cement composition characterized by having a fineness of 3,000~4,500cm ² / g.
The method according to claim 1 or 2,
The low calorific cement is four kinds of low heat portland cement of KS standard KS L 5201, the ultra-low calorific cement composition, characterized in that the content of bellite, 40 parts by weight or more based on 100 parts by weight of the four kinds of portland cement.

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