KR20170143253A - Cement composition for concrete - Google Patents

Abstract

The present invention relates to a cement composition comprising normal Portland cement, calcium sulfoaluminate, furnace slag, II-type anhydrous gypsum and silica fume, and a concrete composition comprising the same. The cement composition has initial shrinkage reduction resistance, bending strength and compression strength and can minimize deformation of a structure even if various variables occur during a curing process.

Description

Technical Field [0001] The present invention relates to a cement composition for concrete having improved bending strength and self-

The present invention relates to a cement composition that can be applied to various structures such as manhole, pile, hume pipe, and a concrete composition containing the same.

The general cement composition can form various structures by mixing cement paste and aggregate, and the strength development after curing is an important factor. However, these concrete have the advantage of high compressive strength, but they have a limit in that they can not be used for complicated or long structures such as piles due to low tensile strength and bending strength.

To solve this problem, a polymer cement composition or a calcium sulfo-aluminate cement composition is used in a hyperconcrete manhole or the like.

Korean Patent Laid-Open No. 10-2007-0095706 discloses a polymer cement composition. This is a mixture of thermosetting resin such as polyester resin, fine powder of slag and aggregate, and has physical properties such as tensile strength and flexural strength higher than that of a common cement composition, and has the advantage of controlling pot life or curing time during the curing process . However, the costs of raw materials themselves are high, and the supply and demand of raw materials is not easy due to fluctuations in oil prices due to the use of various resins. In addition, there is a problem of low energy efficiency due to high temperature and high pressure required in the curing process.

The calcium sulfo-aluminate-based cement composition is a high-strength cement composition having a performance similar to a polymer concrete manhole using a mixed cement and water as a binder. The calcium sulfo-aluminate-based cement composition is applied to a hyper-concrete for ultra-high-strength concrete. The calcium sulfo-aluminate-based cement composition has an advantage over the polymer cement composition in terms of relative cost, but still requires higher tensile strength and bending strength.

These conventional cement compositions require higher mechanical properties and therefore require higher mechanical properties such as tensile strength and flexural strength.

Particularly, even if a slight change occurs in the curing process during the formation of the structure, permanent deformation and damage may occur in the manufactured structure, so that the improvement of the theoretical values of the tensile strength and the bending strength is still limited.

In addition, conventional cement compositions can cause cracks when applied to concrete, and such cracks are caused by various factors such as material factors, construction factors, environment and structural factors. One of the frequent examples is dry shrinkage cracks. Dry shrinkage cracking is a phenomenon caused by shrinkage due to volume decrease due to capillary tension due to external movement of water during concrete hardening. Dry shrinkage is a phenomenon occurring in most concrete. When members are confined, cracks are caused by internal stress due to volume reduction, which is the cause of most cracks in concrete.

Recently, the possibility of cracks is increasing due to the increase of constraining force and internal stress acting on concrete such as slab of long span due to enlargement and long conversation and use of precast permanent form for construction convenience. In addition, there is a problem that it is difficult to secure workability such as production of ready-mixed concrete due to low fluidity due to degradation of aggregate used in concrete production. In addition, cracking due to drying shrinkage is increasing due to an increase in the unit yield.

Therefore, there is a need for a cement composition which is excellent in mechanical properties such as tensile strength and bending strength, crack resistance due to drying shrinkage, and has little influence on the structure deformation even when various parameters are generated in actual curing process.

Korean Patent Publication No. 10-2007-0095706

It is an object of the present invention to provide a cement composition having improved mechanical strength and crack resistance such as tensile strength, bending strength and compressive strength, and a concrete composition containing the same.

It is also an object of the present invention to provide a cement composition and a concrete composition containing the cement composition, wherein the deformation strength and the late strength are remarkably improved and the deformation of the structure can be minimized even if various parameters are generated during the curing process.

The cement composition according to one example of the present invention usually includes Portland cement, calcium sulfo-aluminate, blast furnace slag, type II anhydrous gypsum and silica fume.

In one example of the present invention, the cement composition may further comprise a polycarboxylic acid-based water reducing agent.

In one example of the present invention, the cement composition comprises 40 to 80% by weight of the ordinary Portland cement, 1 to 10% by weight of the calcium sulfo-aluminate, 10 to 30% by weight of the blast furnace slag, 0.5 to 10 wt% of anhydrous gypsum, 0.5 to 10 wt% of the silica fume, and 0.5 to 10 wt% of the polycarboxylic acid-based water reducing agent. However, this is a preferred example for further improving the effect of the present invention, but the present invention is not limited thereto.

In one example of the present invention, the powdery degree of the ordinary Portland cement may be 3,000 to 4,500 cm ² / g, the powdery degree of the calcium sulfo-aluminate may be 4,000 to 7,000 cm ² / g, The powdery degree of the slag may be in the range of 3,500 to 5,500 cm ² / g, the powdery degree of the II-type anhydrous gypsum may be in the range of 2,500 to 4,000 cm ² / g and the silica fume powder may be in the range of 100,000 to 150,000 cm ² / Lt; / RTI > However, this is a preferred example, and the present invention is not limited thereto.

The concrete composition according to an example of the present invention includes the cement composition, aggregate and water.

In one embodiment of the present invention, the concrete composition may include 100 to 600 parts by weight of the aggregate and 5 to 50 parts by weight of the aggregate with respect to 100 parts by weight of the cement composition. However, this is a preferred example, and the present invention is not limited thereto.

The method of manufacturing a concrete structure according to an exemplary embodiment of the present invention includes the steps of s1) placing the concrete composition, s2) first curing at 10 to 30 ° C for 15 to 90 minutes, s3) And c) curing by heating to 10 to 30 ° C. for 8 to 24 hours. However, it is also possible to apply the conventional method used in the technical field of the present invention.

In one example of the present invention, steps s2) and s3) may be performed on a vapor phase.

The cement composition of the present invention and the concrete composition containing the cement composition have an excellent mechanical strength and crack resistance such as tensile strength, flexural strength and compressive strength.

The cement composition of the present invention and the concrete composition containing the cement composition of the present invention have remarkably improved demolding strength and late strength so that the deformation of the structure can be minimized even if various parameters are generated during the curing process.

Hereinafter, the cement composition of the present invention and the concrete composition containing the cement composition will be described in detail with reference to the accompanying drawings.

In addition, unless otherwise defined, technical terms and scientific terms used in the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. In the following description, A description of the known function and configuration that can be blurred is omitted.

Also, " concrete " referred to in the present invention can be interpreted to mean a mortar.

Also, units of% used unclearly in the present invention means weight percent.

The cement composition according to one example of the present invention usually includes Portland cement, calcium sulfo-aluminate, blast furnace slag, type II anhydrous gypsum and silica fume.

It is known that the ordinary portland cement has a disadvantage in that when it is used in a general method, the tabular crystal of calcium silicate is produced and the tensile strength and the bending strength are remarkably lowered. However, in the case of the present invention, since the Portland cement is usually combined with calcium sulfo-aluminate, blast furnace slag, type II anhydrous gypsum and silica fume, it can have excellent tensile strength and bending strength, . Particularly, the initial shrinkage rate (before 7 days after pouring) is significantly reduced, and the demolding strength and the late strength are remarkably improved. Thus, even when various variables such as humidity change, temperature change, There is an effect that can be.

The demolding strength referred to in the present invention means the mechanical strength such as compressive strength and flexural strength of the structure 7 days after the composition is demolded from the mold after the composition is placed on the mold. Also, the late strength means mechanical strength such as compressive strength and flexural strength after 7 days from being poured. Generally, there are various variables such as a humidity change, a temperature change, a physical impact, and the like during the curing process in which a composition is put into a mold and a structure is manufactured through a curing process. And is a main object of the present invention.

Accordingly, the present invention uses a composition in which portland cement, calcium sulfo-aluminate, blast furnace slag, type II anhydrous gypsum and silica fume are combined, whereby the initial shrinkage rate is remarkably reduced and the demolding strength is remarkably improved, The strength and the deformation of the structure can be minimized. Therefore, even though the present invention is applied to a complicated or long structure such as a file, there is a remarkable effect that the mechanical strength can be realized so as to approach the theoretical compressive strength and the bending strength which have not been possible in the past.

The calcium sulfo-aluminate _{(3CaO · 3Al 2 O 3 ·} CaSO 4) is ordinary portland cement, blast furnace slag, II type by being combined with anhydrous gypsum and silica fume, may be made of the entangled structure is significantly improved tensile strength and flexural strength with each other have. Particularly, the initial shrinkage rate is remarkably decreased, and the demolding strength and the late strength are remarkably improved. Therefore, even if various parameters such as humidity and temperature change during the curing process, a predictable effect of minimizing the deformation of the manufactured structure can be obtained.

Generally, the blast furnace slag may mean a clay mineral such as silica, which is an impurity present in iron ore and coke, and ash produced when the ash is reacted with lime at a high temperature when producing pig iron from a blast furnace of a steel mill. Blast furnace slag has a drawback in that the curing hardening rate is slower than that of portland cement and exhibits a low strength development rate in the early curing process and increases the shrinkage due to the consumption of internal water after the initial curing by the latent hydraulic reaction. In addition, the blast furnace slag itself is not reactive and does not harden, which limits its usability.

However, in the present invention, since blast furnace slag and ordinary portland cement, calcium sulfo-aluminate, type II anhydrous gypsum and silica fume are bonded, the initial strength development rate is remarkably improved in the curing process, and the demolding strength is excellent and the initial shrinkage reduction is remarkably improved do. In addition, hydration reaction with the components of the present invention produces hydrates such as SH to form a dense structure, thereby improving mechanical strength such as compressive strength and flexural strength.

The Type II anhydrous gypsum is usually associated with portland cement, calcium sulfo-aluminate, blast furnace slag and silica fume, allowing excellent late strength to be expressed faster during the curing process, minimizing adverse effects due to the effects of various variables There is an effect that can be. Although not specifically described as a separate embodiment, specific effects can be obtained in which physical properties such as excellent late strength as well as crack resistance are improved.

The silica fume is usually combined with Portland cement, calcium sulfo-aluminate, blast furnace slag and type II anhydrous gypsum, thereby significantly improving the demolding strength and the late strength. In detail, microvoids are formed in the existing composition of the respective components. By making the microvoids filled with silica fume to have a dense structure, the mechanical strength can be improved. In addition, the above-described initial shrinkage ratio is remarkably reduced, and the demolding strength and the late strength are remarkably improved. As a more preferable example, when the silica fume has a particle diameter of 0.05 to 5 占 퐉, preferably 0.1 to 1 占 퐉, the above effect can be further improved.

The above-mentioned ordinary Portland cement, calcium sulfo-aluminate, blast furnace slag, type II anhydrous gypsum and silica are preferably powdery particles, and their powdery degree is not limited to the extent that the object of the present invention can be achieved Do not. As a more preferred example, the powdery degree of the ordinary Portland cement may be 3,000 to 4,500 cm ² / g, the powdery degree of the calcium sulfo-aluminate may be 4,000 to 7,000 cm ² / g, and the powder of the blast furnace slag turning may be 3,500 ~ 5,500 cm ² / g may be, powder diagram of the II-type anhydrous gypsum is 2,500 ~ 4,000 cm ² / g may be, fineness of the silica fume is 100,000 ~ 150,000 cm ² / g . If this is satisfied, the initial shrinkage rate can be significantly reduced and the demolding strength and the late strength can be further improved. However, it should be understood that the present invention has been described as a preferred example in which the effects of the present invention can be further improved.

In a preferred embodiment of the present invention, the cement composition may further comprise a polycarboxylic acid-based water reducing agent. When the polycarboxylic acid-based water reducing agent is combined with ordinary portland cement, calcium sulfo-aluminate, blast furnace slag, type II anhydrous gypsum and silica fume, the elapsed time from the curing process to the late strength is accelerated, There is an effect that the demolding strength and the latter strength are further increased. In addition, even though it has good water repellency and excellent demolding strength, the slump and the air amount can be maintained for a long time and the workability can be improved even in the case of poor aggregate. As a specific example, the polycarboxylic acid-based water reducing agent includes an air entraining and water reducing agent mainly composed of polyethylene glycol alkyl ether.

The composition ratio of the cement composition may be within a range that can achieve the object of the present invention. For example, the composition may comprise 40 to 80% by weight of the ordinary Portland cement, 1 to 10% by weight of the calcium sulfo-aluminate, 10 to 30% by weight of blast furnace slag, 0.5 to 10% by weight of the II-type anhydrous gypsum, and 0.5 to 10% by weight of the silica fume. More preferably, 50 to 70% by weight of the ordinary Portland cement, 3 to 7% by weight of the calcium sulfo-aluminate, 15 to 25% by weight of the blast furnace slag, 3 to 10% by weight of the II- % And 3 to 5% by weight of the silica fume. When the polycarboxylic acid-based water-reducing agent is further included, the amount of the polycarboxylic acid-based water-reducing agent may be 0.5 to 10% by weight. When the composition ratio is satisfied, the above-mentioned demolding strength and late strength can be further improved, and adverse effects due to various parameters can be minimized during the curing process, thereby improving the workability.

In one embodiment of the present invention, the cement composition may further include one or two or more organic acids selected from dioxysuccinic acid, succinic acid, citric acid and anhydrous citric acid, and calcium aluminate cement (CAC). If this is the case, by lowering the surface tension of the pore water in the cement, the drying shrinkage resistance can be improved by decreasing the stress caused by the drying of the capillary water, so that the demolding strength can be further improved. Also, by increasing the drying speed and absorbing the stress generated in the cement, the crack resistance can be improved, and the material separation resistance, workability and freeze-thaw durability can be improved. When the cement composition further contains the organic acid and calcium aluminate-based cement, the content ratio of each component may be as long as the above effect can be achieved. For example, the amount of the organic acid may be 0.1 to 5 wt. And 0.1 to 5 parts by weight of the calcium aluminate-based cement.

In one embodiment of the present invention, the cement composition may further include various additives as required. As an example, the additive may be selected from the group consisting of an air entraining agent, an aggregate, a volcanic ash, a dispersant, a curing modifier, a strength modifier, a curing retarder, a wetting agent, a water soluble polymer, a flow modifier, a water repellent, a permeability reducer, And the like can be included. These additives are known in various literatures and can be referred to.

The concrete composition according to an example of the present invention includes the cement composition, aggregate and water.

The aggregate may be a known aggregate used for concrete, and may include any one or two or more selected from silica sand, sand, lumber, washing sand, crushed aggregate, and the like. In a preferred example, the aggregate has a particle size of 6 mm or less, preferably 0.01 to 6 mm, in view of the above-described effect being exhibited.

In a preferred embodiment, the aggregate may include a fine aggregate having a particle size of 0.1 to 2 mm and a coarse aggregate having a particle size of 5 to 20 mm. If this is satisfied, mechanical strength such as compressive strength and flexural strength can be further improved.

The composition ratio of the concrete composition may be within a range that can achieve the object of the present invention. For example, 100 to 600 parts by weight of the aggregate and 5 to 50 parts by weight of the aggregate are included in 100 parts by weight of the cement composition . When this is satisfied, excellent demolding strength and later strength can be realized.

The method of manufacturing a concrete structure according to an exemplary embodiment of the present invention may use a known method, but in terms of realizing superior deformation strength and late strength, it is preferable to s1) pour the concrete composition, s2) C) curing at 10 to 30 ° C for 3 to 4 hours, s4) secondary curing by heating to 50 to 70 ° C for 1 to 4 hours, and s4) curing at 10 to 30 ° C for 8 to 24 hours Step < / RTI > If this is satisfied, the demolding strength and the late strength are remarkably improved, and the occurrence of various variables such as humidity change, temperature change, physical impact and the like in the curing process can be fundamentally minimized, and the deformation of the manufactured structure can be minimized There is an effect. Also, the above effects can be further improved when steps s2) and s3) are carried out on a steam. More preferably, the elevated temperature and the reduced temperature are performed at a constant speed, so that the structure can be stably manufactured, so that the deformation of the structure can be minimized.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples. However, the present invention is described in more detail with reference to the following Examples. However, the scope of the present invention is not limited by the following Examples.

The mixture powder is also based on the total amount of 3,650 cm ² / g of ordinary Portland cement (Holy cement), 66% by weight, fineness is 5,500 cm ² / g of calcium sulfo-aluminate (polar) 5.5% by weight, fineness is 4,400 cm ² / g of blast furnace slag (Jin global) 19.5% by weight, fineness is 3,250 cm ² / g of type II anhydrous gypsum (listening material) of 5% by weight and the fineness is 125,000 cm ² / g of silica fume (Chemie cone ) Were mixed to prepare a mixture. Each component of the mixture contains the components as shown in Table 1 below.

Components (% by weight) SiO ₂ Al ₂ O ₃ CaO Fe ₂ O ₃ MgO SO ₃ K ₂ O Na ₂ O TiO ₂ Usually Portland Cement 20.6 6.1 62.4 3.0 2.3 2.0 0.5 0.1 0.4 Calcium sulfo-aluminate 8.4 32.0 44.2 2.3 1.1 9.5 0.2 1.2 - Blast furnace slag 33.6 14.5 43.5 0.3 5.2 1.4 0.4 0.2 0.8 Type II anhydrous gypsum 0.8 - 40.5 - - 56.7 - - - Silica fume 95.0 0.6 0.4 0.3 0.7 - 1.0 0.2 -

Then, 102 parts by weight of the mixture and 102 parts by weight of sand having a diameter of 1 mm, 119 parts by weight of gravel having a diameter of 10 mm and 16 parts by weight of water were mixed to prepare a concrete composition.

The concrete composition was poured into a mold and cured at 20 DEG C for 2 hours. Subsequently, the temperature was raised to 60 ° C for 2 hours at a constant rate, and steam curing was maintained at 60 ° C for 7 hours in a vapor state. Then, the concrete was cured by heating at a constant rate up to 20 ° C for 13 hours to complete the concrete structure.

In order to evaluate the physical properties of the concrete structure, shrinkage percentage, flexural strength and compressive strength were measured by the KS F 2476 test method. Specifically, the physical properties at the time when 4 hours, 1 day, 3 days, 7 days, and 28 days elapsed from the time immediately after the concrete composition was poured were measured respectively. The results are shown in Tables 3, 4 and 5 Respectively.

The procedure of Example 1 was repeated, except that the mixture was further mixed with 4 parts by weight of a polycarboxylic acid-based water reducing agent (WRM50S, LG Chem) based on 100 parts by weight of the mixture.

In Example 2, the same procedures as in Example 2 were carried out except that 3 parts by weight of dioxysuccinic acid and 3 parts by weight of calcium aluminate cement (CA-25 R *, ALMATIS) were further mixed in 100 parts by weight of the mixture Respectively.

As a result, it was confirmed that the shrinkage ratio of Example 3 was lower than that of Example 2. Especially, it was confirmed that the initial shrinkage reduction effect of 7 days or less was more remarkable, and more specifically, the initial shrinkage reduction effect of 3 days or less was more remarkable. It was also confirmed that the flexural strength and compressive strength of Example 3 were superior.

[Comparative Examples 1 to 7]

The procedure of Example 2 was repeated except that the specific components were excluded from the mixture as shown in Table 2 below.

weight% Usually Portland Cement Calcium sulfo-aluminate Blast furnace slag Type II anhydrous gypsum Silica fume Example 1 66.0 5.5 19.5 5.0 4.0 Example 2 Comparative Example 1 100 - - - - Comparative Example 2 75.0 - 25.0 - - Comparative Example 3 - 85.0 - 7.5 7.5 Comparative Example 4 70.0 5.5 - 5.0 5.0 Comparative Example 5 70.0 5.5 19.5 5.0 - Comparative Example 6 70.0 5.5 19.5 - 5.0 Comparative Example 7 70.0 - 20 5.0 5.0

Tables 3 to 5 below show the shrinkage, flexural strength and compressive strength measured by the KS F 2476 test method.

Shrinkage (ring constraint test, 탆) 4 hours 1 day 3 days 7 days 28th Example 1 -16 -39 -139 -257 -486 Example 2 +50 -One -121 -201 -314 Comparative Example 1 -21 -57 -158 -269 -521 Comparative Example 2 -18 -40 -164 -273 -619 Comparative Example 3 +74 +12 -87 -210 -344 Comparative Example 4 +35 +3 -127 -211 -337 Comparative Example 5 +32 -39 -140 -261 -415 Comparative Example 6 +20 -12 -113 -222 -349 Comparative Example 7 -13 -58 -161 -270 -533

As shown in Table 3, it can be seen that the shrinkage ratio of Example 2 is significantly lower than that of Comparative Examples 1 to 7. [ Especially, it can be seen that the initial shrinkage reduction effect of 7 days or less is remarkable. Therefore, it can be understood that the structure can be formed more stably in the initial curing process, which is highly adverse to the environment.

Bending strength (kgf / cm ² ) 4 hours 1 day 3 days 7 days 28th Example 1 78.7 148.1 176.5 181.1 191.7 Example 2 83.3 152.1 183.2 184.3 209.9 Comparative Example 1 55.5 108.0 107.3 119.3 130.4 Comparative Example 2 42.1 87.3 102.7 120.8 154.7 Comparative Example 3 123.4 168.7 184.3 183.7 187.2 Comparative Example 4 85.6 138.4 163.7 167.8 171.4 Comparative Example 5 79.7 125.5 168.6 174.1 189.3 Comparative Example 6 67.1 117.4 167.2 175.3 188.4 Comparative Example 7 81.7 131.6 169.1 176.3 187.4

Compressive strength (Mpa) 4 hours 1 day 3 days 7 days 28th Example 1 81.5 92.1 118.3 120.1 135.3 Example 2 85.1 93.2 121.4 124.1 140.7 Comparative Example 1 47.5 73.2 69.3 74.5 94.1 Comparative Example 2 35.2 42.6 66.2 92.9 104.2 Comparative Example 3 87.2 101.7 124.7 123.3 132.4 Comparative Example 4 86.4 95.2 94.1 100.7 106.1 Comparative Example 5 64.4 92.8 99.1 107.4 106.6 Comparative Example 6 51.2 116.3 109.7 117.1 119.3 Comparative Example 7 50.4 78.2 90.7 99.7 113.7

As shown in Tables 4 and 5, in the case of Examples 1 and 2, it can be seen that the initial bending strength and the compressive strength are significantly higher than 7 days. Therefore, it can be seen that the structure can be formed more stably in the initial curing process, which is highly adverse to the environment.

Further, in the case of Example 2, it can be seen that the bending strength and the compressive strength are higher than those of Example 1 in terms of the total number of days.

Claims (9)

A cement composition comprising ordinary Portland cement, calcium sulfo-aluminate, blast furnace slag, type II anhydrous gypsum and silica fume. The method according to claim 1,
A cement composition further comprising a polycarboxylic acid-based water reducing agent. 3. The method of claim 2,
Wherein said cement composition comprises 40 to 80 wt% of said ordinary Portland cement, 1 to 10 wt% of said calcium sulfo-aluminate, 10 to 30 wt% of said blast furnace slag, 0.5 to 10 wt% of said II type anhydrous gypsum, 0.5 to 10% by weight of fume and 0.5 to 10% by weight of the polycarboxylic acid-based water reducing agent. The method according to claim 1,
The powdery degree of the ordinary Portland cement is 3,000 to 4,500 cm ² / g, the powdery degree of the calcium sulfo-aluminate is 4,000 to 7,000 cm ² / g, and the powdery degree of the blast furnace slag is 3,500 to 5,500 cm ² / g And the powdery degree of the II-type anhydrous gypsum is in the range of 2,500 to 4,000 cm ² / g, and the powder of the silica fume is in the range of 100,000 to 150,000 cm ² / g. 3. The method of claim 2,
Wherein the cement composition further comprises any one or two or more organic acids selected from dioxysuccinic acid, succinic acid, citric acid and anhydrous citric acid and calcium aluminate cement. A concrete composition comprising the cement composition of any one of claims 1 to 5, aggregate and water. The method according to claim 6,
100 to 600 parts by weight of the aggregate and 5 to 50 parts by weight of the water based on 100 parts by weight of the cement composition. s1) Placing the concrete composition of claim 6
s2) First curing at 10 to 30 占 폚 for 15 to 90 minutes
s3) for 1 to 4 hours to a temperature of 50 to 70 < [deg.] > C,
s4) and curing the mixture at a temperature of 10 to 30 DEG C for 8 to 24 hours to cure the concrete. 9. The method of claim 8,
Wherein the steps s2) and s3) are performed on a vapor phase.