KR101468987B1 - Coke-ash containing ground granulated blast-furance slag composition and method for manufacturing of the same - Google Patents

Abstract

In the present invention, existing gypsum used in producing blast furnace slag fine powder for concrete is replaced by a mixture including coke-ash, natural anhydrous gypsum, and siliceous gypsum. Based on the total weight of a blast furnace slag fine powder composition, 0.5 wt% or more to less than 6 wt% of coke ash, 1-3 wt% of natural anhydrous gypsum, and 0.5-3.5 wt% of siliceous gypsum are included. At the same time, based on the total weight of the blast furnace slag fine powder composition, 0.1 wt% or more to less than 1.80 wt% of free calcium oxide (free-CaO) is included. By using an alternative mixed gypsum including coke-ash, siliceous gypsum, and natural anhydrous gypsum of the present invention in place of natural anhydrous gypsum and desulfurized gypsum which are gypsums that are widely used for a blast furnace slag fine powder composition, the used amount of natural anhydrous gypsum that entirely imported can be reduced, and coke-ash and siliceous gypsum generated from domestic cogeneration plants can be actively utilized.

Description

Technical Field The present invention relates to a slag fine powder composition for cement mortar or concrete containing Coke-ash and a method for producing the same,

Generally, gypsum is used for controlling the setting time and strength in the process of manufacturing blast furnace slag powder (KS F2563) for concrete, and natural gypsum or desulfurization gypsum is mainly used. The natural anhydrous gypsum is excellent in quality but depends on imports of all the products and has a high price. The desulfurized gypsum contains moisture, which causes problems in metering and processing.

In the present invention, in order to solve the problems of the natural anhydrous gypsum and the desulfurized gypsum which have been used for producing the conventional blast furnace slag fine powder, coke-ash, natural anhydrous gypsum, fly ash, (Hereinafter referred to as "siliceous gypsum"), and to produce blast furnace slag fine powders having better physical properties than those of the conventional natural anhydrous gypsum or desulfurized gypsum alone. By applying such a blast furnace slag powder to a cement mortar or a concrete mixture composition, it is possible to provide a cement or concrete composition having excellent physical properties and performance.

Furnace slag is a by-product produced when pig iron is made in a furnace. When raw materials including iron ore, coke and limestone are melted at a temperature of 1500 ° C or higher, molasses and mineral components dissolve, And the blast furnace slag is discharged. This blast furnace slag is quenched by high-pressure water and is referred to as blast furnace slag, and an appropriate amount of gypsum is added to the blast furnace slag thus produced to be mixed and pulverized, or the blast furnace slag and gypsum are separately pulverized, , And the mixture is referred to as a blast furnace slag fine powder.

The blast furnace slag fine powder is mixed with Portland cement to prepare a mortar composition, or the mortar composition is further mixed with a chemical admixture as an aggregate and a cement activator to prepare a concrete composition.

Generally, natural anhydrous gypsum or desulfurized gypsum is used for the production of the blast furnace slag fine powder. The natural anhydrous gypsum used therein contains about 55% of sulfur trioxide (SO ₃ ), and the desulfurization gypsum contains about 40% . In the KS standard (KS F 2563) for blast furnace slag for concrete containing such gypsum, the ratio of sulfur trioxide is specified to be 4.0 wt% or less with respect to the total weight of the blast furnace slag fine powder, and the gypsum used is KS L5313 and KS L9005, or any equivalent thereto.

In the mortar or concrete composition, the calcium oxide and sulfur trioxide components act as cement alkali stimulants and play an important role in the strength development of final cement or concrete. At present, the total amount of natural anhydrous gypsum used in the blast furnace slag powder to provide the above components depends on imports. Desulfurization gypsum is a substitute for this gypsum. The amount of sulfur trioxide is lower than that of natural anhydrous gypsum, and it exists in the form of sludge containing about 10% of water, so that it is difficult to quantify, input, There is a problem.

In order to solve the above-mentioned problems, there has been proposed a method for activating fine powder of blast furnace slag, cement and concrete using desulfurized gypsum, siliceous gypsum and mangos in the patent No. 0054859 and waste water gypsum in the registered patent No. 1308388. However, There is still room for improvements in the strength and physical properties of the final product, cement or concrete, and there is no particular technical interest in the amount of calcium oxide, especially free-CaO.

Generally, calcium oxide exerts an effect of promoting the hydration reaction of the blast furnace slag fine powder. Specifically, the calcium oxide generates calcium hydroxide (Ca (OH) ₂ ) in the hydration reaction process, and the initial strength is expressed by the pottery effect. The Ca ^{2 +} ions released from calcium hydroxide silicate contained in the blast furnace slag (SiO ₂₎ or aluminate (Al ₂ O ₃₎ reacts with the calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH) And the like.

However, the calcium oxide is combined with silicate, aluminum oxide and iron trioxide to form a clinker mineral and the remaining small amount of calcium oxide component is referred to as free calcium oxide. This free calcium oxide is used as a substitute for natural anhydrous gypsum It is contained in a small amount in the siliceous gypsum (fly ash) and coke ash to be used, and it is caused by uneven mixing of raw materials or unevenness of firing temperature.

When the amount of free calcium oxide is less than 1.5% by weight based on the total weight of the cement, there is no serious problem. However, when the amount of calcium oxide is more than a certain amount, high heat is generated during the hydration reaction with water, And may cause deterioration in quality due to cracks and twisting phenomenon of the structure due to a change in volume during curing, and it may cause damage such as cracking due to expansion in the long-term age after curing.

Therefore, in using silicate grit and cork ash as a substitute for natural anhydrous gypsum, its composition needs to be optimized so that the amount of free calcium oxide can be maintained within an acceptable range, The physical properties of cement or concrete should not be significantly deteriorated as compared with the conventional blast furnace slag fine powder using only natural anhydrous gypsum.

In the present invention, an alternative (mixed) gypsum composition for use in the production of cement mortar or concrete blast furnace slag fine powder having a specific optimized composition and a method for producing the same are proposed. Cement mortar composition or concrete composition.

Patent No. 0054859 Patent No. 1308388

The present invention relies on the replacement of existing anhydrous gypsum used in the manufacture of conventional blast furnace slag fine powders with alternative (mixed) gypsum, which is a mixture of silicate gypsum (fly ash), coke ash and natural anhydrous gypsum To reduce the amount of natural anhydrite used.

Coke ash generated by pulverized coal combustion in a coal mine coal-fired power plant and petroleum coke, which is a by-product of pyrolysis thermal cracking process, is used as fuel in a cycle fluidized bed boiler cogeneration plant is called a blast furnace slag fine powder And to optimize the mixing ratio thereof to improve the physical properties such as compressive strength and stability of the final cement or concrete structure.

Since the portland cement used in the preparation of the cement mortar composition contains about 1 to 1.2% by weight of free-CaO component, in the present invention, the amount of free calcium oxide contained in the final cement is not more than 1.5% The composition of the blast furnace slag composition is optimized so as to prevent problems such as cracking after curing.

The blast furnace slag fine powder composition for cement mortar or concrete according to the present invention which can solve the problems of the prior art and improve the strength or stability of the cement or concrete structure is characterized in that the blast furnace slag finest powder composition contains not less than 0.5% A coke ash of less than 7% by weight, 1 to 3% by weight of natural anhydrous gypsum, 0.5 to 3.5% by weight of silicate gypsum and 87 to 98% by weight of blast furnace slag, wherein the total weight of the blast furnace slag fine powder composition Free calcium oxide (free-CaO) is contained in an amount of 0.1 wt% or more and less than 1.80 wt%.

The cement mortar composition can be prepared by mixing portland cement at a weight ratio of 1: 1 to the blast furnace slag fine powder composition. Further, a chemical admixture, which is an aggregate and a cement activator, is further mixed with the prepared cement mortar composition to prepare a concrete composition can do.

Another embodiment of the present invention is a method for producing a blast furnace slag composition for a cement mortar or a concrete, comprising the steps of: (a) mixing 0.5 to 7% by weight of coke ash, 1 to 3% by weight of natural anhydrous gypsum, and 0.5 to 3.5% by weight of silicate gypsum; and (b) blending the mixture of the first step with blast furnace slag in an amount of 87 to 98 wt% based on the weight of the blast furnace slag fine powder % By weight of the composition.

Preferably, the second step is performed by heating at a temperature of 200 to 250 ° C. The cement mortar or concrete blast furnace slag fine powder composition prepared by this method is mixed with Portland cement at a weight ratio of 1: 1 to form a cement mortar composition And the concrete composition can be prepared by mixing the cement mortar composition with a chemical admixture as an aggregate and a cement activator.

INDUSTRIAL APPLICABILITY According to the present invention, by using an alternative mixed gypsum containing the coke ash, siliceous gypsum and natural anhydrous gypsum of the present invention in place of natural anhydrous gypsum and desulfurization gypsum which are widely used in conventional blast furnace slag fine powder compositions, It is possible to save resources and to be eco-friendly because it can reduce the amount of natural anhydrous gypsum to be used, and can actively use coke ash and siliceous gypsum, which are generated as byproducts in domestic cogeneration power plants.

In addition, by optimizing the mixing composition of such substituted gypsum, it is possible to produce cement and concrete having excellent strength as compared with the case of using natural gypsum and desulfurization gypsum.

FIG. 1 shows an image obtained by filtering raw material and sieve of coke ash. In the raw sample of coke ash, fine pulverized particles having a size of 90 μm or more are contained at a level of 0.3 to 3.0%.
Fig. 2 is an image showing the stability of the mortar through changes in length before and after curing of the cement mortar.
Fig. 3 shows an experimental apparatus for observing changes in the hydration heat of concrete according to the content of free calcium oxide.
FIG. 4 is a graph showing the temperature of concrete varying with time according to the type of gypsum.
5 is an image showing whether or not the concrete specimen is cracked according to the amount of calcium oxide glass.

Natural gypsum and desulfurization gypsum are widely used as gypsum slag powder for concrete. Since the natural anhydrous gypsum does not contain moisture and is easy to handle and contains a large amount of cement alkali stimulants such as calcium oxide and sulfur trioxide, it has an advantage of securing strength when used for mortar or large crate formulations, It is widely used in blast furnace slag fine powders.

However, the above-mentioned natural anhydrous gypsum is entirely dependent on imports, and desulfurized gypsum has a problem that the trioctylation component contains less moisture than natural anhydrite. Accordingly, the present invention provides a cement mortar and concrete having improved performance and physical properties by using a mixture of cork ash, siliceous gypsum and natural anhydrous gypsum instead of a single use of natural anhydrous gypsum or desulfurized gypsum.

The analysis results of the major constituents of the conventional widely used natural anhydrous gypsum and desulfurization gypsum and the coke ash and siliceous gypsum to be used in the present invention are shown in the following Table 1.

division Main components (% by weight) Silicate MgO SO ₃ Total calcium oxide (free calcium oxide) Natural anhydrous gypsum 0.8 to 2.0 0.1 to 0.2 55 ~ 57 40.0 (-) Desulfurization plaster 1-3 0.3 to 0.5 40 to 44 30 ~ 35 (-) Siliceous gypsum 45 to 55 1-3 5 to 10 15 to 25 (5 to 10) Coke ash 5-12 1-2 20 ~ 30 50 to 60 (15 to 35)

Among the components of each gypsum in Table 1, calcium oxide (CaO) and sulfur trioxide (SO ₃ ) serve as cement alkali stimulants. Natural anhydrite contains the highest proportion of trioxide, and coke ash It can be seen that calcium oxide is the most abundant. In particular, in the present invention, calcium silicate gypsum and coke ash which are intended to be used in place of natural anhydrite gypsum contain a considerable amount of free calcium oxide, unlike conventional natural anhydrous gypsum and desulfurization gypsum The measurement method of calcium is described later in [Example 1]).

As mentioned in the Background of the Invention, calcium oxide generally promotes hydration reaction of blast furnace slag fine powder. Specifically, calcium oxide produces calcium hydroxide (Ca (OH) ₂ ) in the hydration reaction process, And the initial strength is expressed by the magnetizing effect. The Ca ^{2 +} ions released from calcium hydroxide silicate contained in the blast furnace slag (SiO ₂₎ or aluminate (Al ₂ O ₃₎ reacts with the calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH) And the like.

When the amount of free calcium oxide (CaO) that can be contained in the calcium oxide is increased to a certain amount or more, high heat is generated in the hydration reaction process to be combined with water, so that the cement and concrete are quickly condensed before curing, It may cause deterioration of quality due to cracks and distortion of the structure due to a change in volume during curing, and it may cause damage such as cracking due to expansion in the long-term age after curing. Therefore, when preparing the blast furnace slag fine powder composition using the alternate mixed gypsum (coke ash and silicate gypsum), it is necessary to control the amount of the calcium free glass oxide to an appropriate level.

Sulfur dioxide has a high initial solubility and acts as a coagulation retardant for cement. However, it acts as a reaction promoter for blast furnace slag, which exhibits latent hydraulic properties, and plays an important role in securing initial workability and exhibiting strength. According to the KS standard, the ratio of the trioxide term to the total weight of the blast furnace slag powder is 4.0% by weight or less.

Magnesium oxide (MgO) reacts with H ₂ O to form magnesium hydroxide (Mg (OH) ₂ ) in the presence of an appropriate amount (10.0% or less in the KS standard) and causes volume expansion. .

Hereinafter, the technical features of the present invention will be described in detail with reference to embodiments and drawings. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents. shall.

blast furnace Slag Fine powder  Preparation of composition

(1) Blast furnace slag Composition ratio of fine powder composition

Blended mixture of natural anhydrous gypsum, silicate gypsum and coke ash and blast furnace slag with the composition as shown in the following Table 2 were blended to prepare blast furnace slag fine powders as in Experimental Examples 1 to 6, Comparative Example 1 (fine blast furnace slag using only natural anhydrous gypsum) and blast furnace slag fine powder using conventional mixed gypsum (Japanese Patent No. 1308388) were used as Comparative Example 2 and Comparative Example 3 using only coke ash. Comparative Example 4 was used to prepare fine blast furnace slag compositions having various compositions.

division
Mixture composition (% by weight) Within the overall composition
Content (% by weight) Blast furnace
Slag Natural anhydrous
gypsum Desulfurization plaster Siliceous gypsum Coke ash sulphate of soda Free calcium oxide Sulfur trioxide Comparative Example 1 96.5 3.5 - - - - - 2.11 Comparative Example 2 91.5 - 3.5 3.0 - 0.2 0.01 0.96 Experimental Example 1 96.5 2.0 - 1.0 0.5 - 0.16 1.09 Experimental Example 2 96 2.0 - 1.0 1.0 - 0.31 1.21 Experimental Example 3 94 2.0 - 1.0 3.0 - 0.92 1.71 Experimental Example 4 92 2.0 - 1.0 5.0 - 1.38 2.21 Experimental Example 5 91 2.0 - 1.0 6.0 - 1.56 2.41 Experimental Example 6 90 2.0 - 1.0 7.0 - 1.80 2.72 Experimental Example 7 87 2.0 - 1.0 10.0 - 2.19 3.30 Comparative Example 3 93 - - - 7.0 - 1.85 1.76 Comparative Example 4 90 - - - 10.0 - 2.69 2.51

The blast furnace slag fine powder compositions of [Experimental Examples 1] to [Experimental Example 6] and [Comparative Examples 1] to [Comparative Example 4] were prepared by adding each gypsum to the blast furnace slag, Crushing the blast furnace slag and the gypsum, mixing the blast furnace slag and the gypsum at a constant ratio, and then pulverizing the blast furnace slag and the gypsum. In this embodiment, each of the experimental examples and comparative examples are manufactured by the latter method.

Particularly, as shown in FIG. 1, since fine crushed particles of about 90 μm or more are contained in the range of 0.3 to 3.0%, the coke ash yarn can cause poor construction on the hardened surface of the structure when using simple substitution with cement or blast furnace slag fine powder.

Therefore, in the present embodiment, the crushing and classification step of the coke ash was applied to the pretreatment step, and then the composition of Table 2 was used.

(2) Blast furnace slag Determination of the glass powder composition of calcium oxide

The amount of free calcium oxide in the blast furnace slag fine powder composition was quantified by the following method.

1 g of the blast furnace slag fine powder composition sample is weighed, placed in a 100 ml Erlenmeyer flask, and 50 ml of ethylene glycol is added. Next, 5 ~ 6 pieces of glass beads were placed and the stopper was closed and treated in a water bath of 60 ~ 70 ° C for about 30 minutes. At this time, shake well regularly every 5 minutes to avoid lumps.

The filtration step was carried out to separate the free calcium oxide dissolved in ethylene glycol from the sample. Two filtration paper was placed on a Buchner funnel having a diameter of 5 cm, and a few drops of ethylene glycol were dropped on the filter paper, After filtration, it is washed three times with ethylene glycol. Add 3 drops of Bromocresol Green indicator to a 300 ml filtration flask connected to a suction pump and titrate with 0.1 N hydrochloric acid solution. When the clear green color appears, set as the end point.

Approximately 10 g of calcium carbonate (CaCO ₃ ) is placed in a platinum crucible and ignited at about 1050 to 1100 ° C. until it becomes constant, thereby producing pure calcium oxide. After cooling in a desiccator, the sample was titrated by adding various weights corresponding to 0.1 to 5.0% of the sample, and a graph of the titration amount of 0.1 N hydrochloric acid equivalent to the weight loss of calcium oxide was prepared to prepare a standard quantitative graph do.

In this standardized quantitative graph, the titration of 0.1 N hydrochloric acid determined at the end point of the preceding step is found, and the amount of calcium free oxide can be confirmed by finishing at one digit below the decimal point.

cement Mortar  Compressive Strength and Stability

The blast furnace slag fine powder composition prepared in the composition of Example 1 was mixed with Portland cement, which is a conventional cement, in a weight ratio of 1: 1 to prepare a cement mortar composition. The cement mortar composition time was classified into a second result termination , And the compressive strength of the cement specimen (see FIG. 2) was measured with time. Also, the change of length before and after curing was measured and the stability was calculated.

division
Setting time Mortar Compressive Strength (MPa) First minute (minute) Closing (city) 1 day 3 days 7 days 14 days 28th Comparative Example 1 250 7:20 6.2 22.7 33.4 44.5 57.5 Comparative Example 2 260 7:30 6.1 23.1 33.9 44.9 58.1 Experimental Example 1 250 7:10 5.7 21.5 31.5 43.1 56.2 Experimental Example 2 240 7:00 6.5 23.4 34.6 45.2 58.5 Experimental Example 3 230 6:50 6.7 23.6 34.1 45.9 59.1 Experimental Example 4 210 6:20 6.9 24.2 34.5 46.2 59.9 Experimental Example 5 200 6:00 7.1 24.4 34.9 46.5 59.7 Experimental Example 6 180 5:30 7.2 22.4 32.5 43.2 54.2 Comparative Example 3 160 5:10 7.1 21.4 31.5 42.5 53.5 Comparative Example 4 130 4:30 7.4 20.4 30.4 40.5 51.1

As can be seen from the results of the above Table 3, when the blast furnace slag fine powders of Experimental Examples 1 to 5 using the alternative mixed gypsum of the present invention (a mixture of coke ash, silicate gypsum and natural anhydrous gypsum) were used, It was confirmed that the setting time was shortened as compared with the case of using the gypsum (Comparative Example 1) or the existing mixed gypsum (Comparative Example 2), and the compressive strength was also increased after a long time (for example, 28 days) Of the total population.

However, when the amount of the coke ash was 7 wt% or more (Example 6) or when only the coke ash was used, the compressive strength was rather reduced and the condensation time was too fast.

The stability in Table 4 below, that is, the change in length before and after curing, tended to slightly expand in Comparative Examples and Experimental Examples except for Comparative Example 1. However, in the KS specification (KS L5210) of blast furnace slag cement (0.2%) of the blast furnace slag cement stability (autoclave swelling) (except for Experiment 7).

However, it was confirmed that the rate of change of stability increased with the increase of the amount of coke ash, and it was found that when the amount of coke ash was 7% by weight (Example 6), the rate of change was not more than 0.15% , And in the case of Experimental Example 7, it was confirmed to exceed 0.2% which is the range defined by the KS standard.

division
Stability (length change) Curing before After curing Difference Rate of change (%) Comparative Example 1 29.952 29.945 -0.007 -0.023 Comparative Example 2 29.944 29.945 0.001 0.003 Experimental Example 2 29.966 29.975 0.009 0.030 Experimental Example 3 29.961 29.977 0.016 0.053 Experimental Example 4 29.964 29.999 0.035 0.117 Experimental Example 6 29.975 30.022 0.047 0.157 Experimental Example 7 29.977 30.045 0.068 0.227

Concrete Compressive Strength

The cement mortar composition prepared in [Example 1] described above was mixed with fine aggregate, aggregate containing coarse aggregate, and chemical admixture to prepare a concrete mixture composition. The design of the concrete mix composition used was 166 kg per unit volume (1 m ³ ), according to specification 25 (maximum coarse aggregate size: mm) -24 (target strength: MPa) 348 kg of cement, 845 kg of sand, 960 kg of coarse aggregate and 1.91 kg of chemical admixture.

Except that mortar having the composition of Example 1 was used for the cement, and the results of measuring the slump value and the strength indicating the physical properties of the concrete mixture thus prepared were shown in the following Are shown in [Table 5].

division
Properties Concrete Compressive Strength (MPa) Slump (mm) 3 days 7 days 14 days 28th 91 days Comparative Example 1 160 10.2 21.4 27.5 32.9 41.2 Comparative Example 2 170 10.9 22.5 29.0 33.6 41.9 Experimental Example 1 160 10.0 20.9 26.4 33.1 42.2 Experimental Example 2 165 10.8 22.4 29.4 34.5 42.5 Experimental Example 3 160 11.2 23.1 30.3 34.9 42.9 Experimental Example 4 160 11.5 23.9 30.9 35.1 43.5 Experimental Example 5 160 11.8 24.0 31.2 35.4 43.8 Experimental Example 6 165 9.8 21.5 28.5 31.5 40.6

As can be seen from the results of the above Table 5, the compressive strength of the concrete containing the slag fine powder composition of Experimental Examples 1 to 5, which showed excellent results in the mortar compressive strength test of Example 2, ranged from 14 days to 91 days Were higher than those of Comparative Examples 1 and 2 over the measurement period.

Concrete slump change over time

The mortar composition prepared in [Example 1] was mixed with aggregate composed of fine aggregate and coarse aggregate and chemical admixture as cement activator to prepare concrete mixture. The design of the used concrete mixture composition was 172 kg (1 m ³ ) per unit volume (1 m ³ ) according to the specification 25 (coarse aggregate maximum: mm) -24 (target strength: MPa) -180 , 360 kg of cement, 833 kg of sand, 946 kg of coarse aggregate and 1.98 kg of chemical admixture.

The cement was produced by the same composition and method except that the mortar having the composition of Example 1 was used. The concrete mixture thus prepared was measured for slump change with time, and the results are shown in Table 6 ].

division
Change in slump over time (mm) Immediately 30 minutes 60 minutes 90 minutes 120 minutes Comparative Example 1 185 170 140 130 120 Comparative Example 2 190 170 145 135 120 Experimental Example 1 195 165 140 125 115 Experimental Example 2 190 165 135 125 115 Experimental Example 3 185 155 130 120 110 Experimental Example 4 190 150 130 115 105 Experimental Example 5 195 150 125 110 100 Experimental Example 6 195 145 120 105 90

As can be seen from the results of the slump in Table 6, the initial slump retention force of the concrete mixture containing the blast furnace slag fine powder compositions of Experimental Examples 2 to 5, which showed excellent results in the mortar compression strength test of Example 2, It was confirmed that they were reduced to be equal or slightly reduced as compared with Comparative Examples 1 to 2. In Experimental Example 6,

concrete Hydration heat  change

In order to observe the changes in the hydration heat of concrete according to the content of free calcium oxide, the experiment was carried out in the same manner as shown in FIG. 3. The composition of the concrete composition used was 25 (maximum coarse aggregate: mm) 170 kg of water, 575 kg of cement, 642 kg of sand, 967 kg of coarse aggregate and 6.90 kg of chemical admixture were used per unit volume (1 m ³ ) according to the MPa-150 (target slump value: mm) ).

The same composition and method were used for the cement, except that the mortar of the composition prepared in [Example 1] was used. The change in the hydration heat of the concrete for the thus prepared concrete mixture is shown in Fig.

As shown in FIG. 4, the hydration temperature of the concrete increased in proportion to the content of coke ash for about 36 hours after the concrete was poured. This indicates that the amount of calcium oxide contained in the coke ash The higher the hydration temperature, the higher the possibility of cracks in the concrete due to the temperature difference.

concrete Specimen  Expansion crack

According to the results of Examples 1 to 5, when the amount of free calcium oxide is increased to 1.80 wt% or more with respect to the total blast furnace slag fine powder composition, the conventional compressive strength decreases, the congealing speed becomes too high, and the slump property also deteriorates And hydration heat was also increased.

FIG. 5 shows the results of confirming whether cracks were formed after a concrete specimen using the blast furnace slag fine powder compositions of Experimental Example 5 and Experimental Example 6 was left for 6 months or longer for a long period of time. In the case of the concrete specimen of FIG. 5A in which the blast furnace slag fine powder of Experimental Example 5 was used, no crack could be observed even after the 6-month standing time, but the concrete of FIG. 5B using the blast furnace slag fine powder of Experimental Example 6 Many cracks were found in the specimen.

Claims (8)

In a blast furnace slag fine powder composition for cement mortar or concrete,
Based on the total weight of the blast furnace slag fine powder composition, 0.5 to 7% by weight of coke ash, 1 to 3% by weight of natural anhydrous gypsum, 0.5 to 3.5% by weight of silicate gypsum and blast furnace slag 87 To 98% by weight,
A cement mortar or concrete blast furnace slag fine powder composition comprising coke ash characterized in that free calcium oxide (CaO) is contained in an amount of 0.1 wt% to less than 1.80 wt% based on the total weight of the blast furnace slag fine powder composition . delete A cement mortar composition in which the blast furnace slag fine powder composition according to claim 1 and Portland cement are mixed at a weight ratio of 1: 1. A concrete composition comprising the cement mortar composition according to claim 3 mixed with a chemical admixture which is an aggregate and a cement activator. A method for producing a blast furnace slag fine powder composition for cement mortar or concrete,
(a) a first step of mixing 0.5 wt% to less than 7 wt% of coke ash, 1 to 3 wt% of natural anhydrous gypsum, and 0.5 to 3.5 wt% of siliceous gypsum based on the total weight of the blast furnace slag fine powder composition; And
(b) adding and blending the blast furnace slag to the blast furnace slag in a range of 87 to 98 wt% of the blast furnace slag fineness weight after the mixing of the first stage proceeds. A method for producing a cement mortar or concrete blast furnace slag fine powder composition containing coke ash. 6. The method of claim 5,
Wherein the second step is performed by heating at a temperature of 200 to 250 ° C. 11. The method of claim 9, wherein the coke-ash is a cement mortar or concrete blast furnace slag. A method for producing a cement mortar composition according to claim 5 or 6, wherein the Portland cement is mixed with the cement mortar or concrete blast furnace slag fine powder composition at a weight ratio of 1: 1. A method for producing a concrete composition, which comprises mixing a cement mortar composition prepared by the method of claim 7 with a chemical admixture which is an aggregate and a cement activator.

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