JPH05286746A - Concrete composition needless to compact for mass concrete structure - Google Patents

Abstract

PURPOSE:To secure flowability and material separation resistance and to obtain a concrete excellent in the physical properties in the hardened concrete such as strength. CONSTITUTION:A coarse aggregate having 40mm maximum size, a low-heat cement, 165kg/m<3> of water, limestone powder and a high-performance AE water reducing agent are mixed. When the volume of the cement is denoted by C, the volume of water by W and the volume of the limestone powder by L, 0.86<=(C+L)/W<=1.18 and 0.47<=L/C<=0.98 are fulfilled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low exothermic compaction-free concrete composition applied to a mass concrete structure, and more specifically to a coarse aggregate having a maximum dimension of 40 mm and a low exothermic cement as material components. And a compaction-free concrete composition having high fluidity.

[0002]

[Prior art and its problems] In the construction of large-scale concrete structures such as an anchorage (abutment) and piers (piers) of dams and long bridges, a large amount of concrete is poured at once, so the heat of hydration of cement In order to suppress the temperature rise of the concrete due to the use of low heat-generating cement, the material and mixing aspect of the concrete have been devised so as to reduce the cement amount as much as possible. In recent years, in particular, due to the tendency toward large-scale concrete structures and the demand for rapid mass construction, measures against temperature cracks caused by heat of hydration in mass concrete have become more important issues.

On the other hand, in recent years in the field of concrete technology development, new high-quality concrete with high fluidity called high-performance concrete or compaction-free concrete has been developed. It is well known that the new concrete is in the limelight.
This is because it has an advantage that compaction work can be largely omitted.

However, in the above-mentioned mass concrete, suppressing the temperature rise of the concrete is given the highest priority and the unit cement amount is reduced as much as possible.
Since the fluidity of concrete is extremely poor, it is customary to perform sufficient compaction when placing concrete. Until now, no attempt has been made to impart high fluidity to such poorly mixed concrete so that compaction is unnecessary. That is, for example, by applying a compaction-free concrete containing low heat-generating cement and coarse aggregate having a maximum size of 40 mm as a material component to the anchorages, etc. The idea of filling concrete without causing material separation has not been conceived so far.

[0005]

It is an object of the present invention to maintain high fluidity and material separation resistance, which makes compaction unnecessary, for concrete having low heat generation used for mass concrete structures, and has strength characteristics. Another object of the present invention is to provide a concrete composition having properties equal to or higher than those of conventional mass concretes in terms of properties of hardened concrete. The present inventors have completed the invention of the present application as a result of repeating a test for a total of 1200 m ³ in accordance with this purpose.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention is a coarse aggregate having a maximum size of 40 mm,
Low heat-generating cement, unit water content of 165 kg / m ³ or less, limestone powder and high-performance AE water reducing agent, and
The volume of low exothermic cement (C), the volume of water (W),
The present invention relates to a compaction-free concrete composition for a mass concrete structure that satisfies the following formulas (1) and (2) when the volume of limestone powder is represented by (L). (1) 0.86 ≦ (C + L) /W≦1.18 (2) 0.47 ≦ L / C ≦ 0.98

[0007]

[Detailed Description of the Invention] The basis of high-quality concrete mix design is to reduce the amount of unit water as much as possible within the range of required strength, durability, watertightness and suitable workability. Is. Even for compaction-free concrete, after hardening, it must be guaranteed to have a quality equal to or better than that of conventional hard concrete. To that end, the unit water content of the compaction-free concrete of the present invention should not exceed the standard unit water content of conventional hard concrete.

In the compaction-free concrete of the present invention, the maximum size of the coarse aggregate used to reduce the amount of unit cement is 40 mm as a measure against temperature cracks. Here, the grain size of the coarse aggregate is JIS A 5005.
Crushed stone 4005, crushed stone 4020 specified in “crushed stone for concrete”, or blast furnace slag coarse aggregate 4005, blast furnace slag coarse aggregate 4020 specified in JIS A 5011 “Blast furnace slag coarse aggregate for concrete” Say. The standard unit water amount limit of conventional concrete using 40 mm aggregate is about 165 kg / m ³ when the AE water reducing agent is used as an admixture. Therefore,
Also in the present invention, the value is limited.

The low exothermic cement to be blended in the present invention includes two components such as portland cement such as moderate heat cement, sulfate resistant cement and other low exothermic cement, blast furnace B type, blast furnace C type and fly ash cement. It is possible to use a mixed cement of the type, a ternary mixed cement in which Portland cement, blast furnace slag fine powder and fly ash are mixed.

The limestone powder blended in the present invention is a fine powder of limestone or a fine powder obtained by crushing concrete using crushed limestone aggregate which has been used for a long time. Limestone is a sedimentary rock mainly composed of calcium carbonate, and its generation is derived from corals, sea lilies, lime algae, shellfish, etc., so reef limestone fine powder and other mineral fine powders without hydration activity are also used. can do. It should be noted that if it is only necessary to secure the fluidity of fresh concrete, it is possible to increase the amount of hydraulic component materials such as blast furnace slag fine powder, expansive material, and fly ash, but the hydration reaction of hydraulic component materials is also possible. Since the heat generated by the heat increases, the risk of temperature cracking after curing increases.

In the present invention, in order to impart material separation resistance to fresh concrete and ensure sufficient fluidity and deformability, the total volume of low heat-generating cement and limestone powder relative to the volume of water is Ratio is 0.86 ~
It must be within the range of 1.18.

The material separation of fresh concrete is governed by the degree of freedom of movement of the internal free water. On the concrete mix, if the amount of solid particles is so large that the solid particles come into contact with each other to form crosslinks, the movement of pore water does not occur,
Material separation does not occur, but the desired fluidity of concrete cannot be ensured. On the other hand, if the solid particles are relatively small and float in water, the fluidity of the concrete can be secured, but the solid particles having a large specific gravity will settle, and the water having a small specific gravity will float. This tendency becomes more remarkable as the maximum size of the aggregate used increases.

Therefore, in compaction-free concrete, it is necessary to have a certain amount of free water that can be moved, but in the present invention, a relatively large amount of solid fine particles are mixed in the concrete, and high performance AE is achieved. By adding an appropriate amount of water-reducing agent and dispersing them, the water flow formed between solid particles is narrowed and the moving speed of free water is reduced to prevent material separation of concrete with a maximum size of coarse aggregate of 40 mm. To do.

According to the test results conducted by the present inventors, if the total volume of solid fine particle components having a cement particle size or less is 0.86 to 1.18 with respect to 1.0 volume of water. ,
It has been confirmed that even if the maximum size of the coarse aggregate is concrete of 40 mm, sufficient fluidity and deformability are retained, and that no problematic material separation occurs. In this case, if the amount of the solid fine particles relative to water is less than 0.86, the water moves faster, and the coarse aggregate tends to settle,
Further, when the amount of the solid fine particles exceeds 1.18, the moving speed of water becomes extremely small, the viscosity becomes excessively high, and the fluidity of concrete decreases.

In the present invention, the volume ratio of the limestone powder to the cement is 0.47 in order to stick the limestone powder with the low heat-generating cement and to suppress the calorific value of the low heat-generating cement to the minimum. It is necessary to be in the range of 0.98.

As described above, limestone powders are mixed in order to maintain the fluidity while suppressing the heat generation of the low heat-generating cement. Mineral fine particles such as limestone powders having almost no hydration activity. Not only does not contribute to the strength development of concrete by itself, but if only such mineral fine particles aggregate and exist in a part of the hardened structure of concrete, it becomes a defect in strength. There is naturally a limit to the amount of limestone powder that can be mixed with. That is, the amount of the limestone powder to be mixed must be within a range that allows the hydration product of the low-pyrogenic cement to stick around these individual fine particles.

According to the results of the tests conducted by the inventors of the present invention, in which the amount of cement and the amount of water were kept constant and the amount of limestone powder mixed was increased or decreased, the material separation was suppressed as the amount of limestone powder mixed increased, and Although the strength tends to increase, the tendency reached a maximum at a maximum volume of limestone powder of 0.98 with respect to a cement volume of 1.0. On the other hand, when the amount of limestone powder mixed is smaller than the amount of cement, material separation is likely to occur and the desired fluidity cannot be maintained. In this case, it is possible to impart fluidity by increasing the amount of cement, but this is not desirable in controlling the temperature crack as described above. Therefore, assuming that the amount of cement calculated from the strength is not increased, the lower limit of the amount of limestone powder to be mixed for securing the fluidity of concrete is 0.
It became 47 times.

The finer the particle size of the mineral fine particles having almost no activity represented by limestone powder, the larger the specific surface area thereof, and the sticking effect of the hydraulic component material represented by low heat-generating cement decreases. You need to consider that. In the present invention, the fineness of the limestone powder is suitably within the range of 3500 to 9000 cm ² / g in terms of Blaine value. That is, if it is less than 3500 cm ² / g, the material separation of the concrete is likely to occur, while if it exceeds 9000 cm ² / g, the unit water content increases to give the desired fluidity, or as described later. This is because the amount of the high-performance AE water reducing agent used excessively increases.

The compaction-free concrete of the present invention is a mixture of a large amount of solid fine particles containing cement as compared with conventional mass concrete, and it is an important requirement that they be uniformly dispersed in fresh concrete. Become. Therefore, to improve the dispersibility of solid fine particles in water,
Moreover, high performance AE that does not adversely affect the properties of hardened concrete
Use a water reducing agent.

The high-performance AE water-reducing agent can be appropriately selected from various commonly used cement additives. For example, formalin condensate of β-naphthalene sulfonate, formalin condensate of melamine sulfonate, polycarboxylic acid ether compound, polystyrene sulfonate, hydroxypolyacrylate, α, β-
Copolymer of unsaturated dicarboxylic acid and olefin, copolymer derived from polyethylene glycol monoallyl ether and maleic acid type monomer, isobutylene-styrene maleic acid type, isobutylene-acrylic acid ester-maleic acid type, isobutylene-styrene -Acrylic acid ester-maleic acid-based copolymers, modified lignin sulfonic acid compounds, aromatic amino sulfonic acid-based polymer compounds, and the like as main components are included.

The high performance AE water reducing agent is blended in a dry weight of 0.7% to 2% with respect to the low heat-generating cement. Further, this blending ratio corresponds to 0.4% to 1.2% in dry weight with respect to the total amount of the low heat-generating cement and the limestone powder. The high-performance AE water reducing agent is generally added to the mixing water and mixed, but it may be mixed in advance with the cement or the limestone powder before the main mixing.

Also in the present invention, an AE agent, a set accelerator, a set retarder, a strength enhancer, an antifreeze / antifreeze agent, which is commonly used as an admixture for cement concrete, is used according to the purpose of use and the application of mass concrete. Agents and the like can be mixed.

The non-compacting concrete composition according to the present invention is, in addition to the above-mentioned mass concrete, precast concrete, prestressed concrete, tunnel lining and other general civil construction structures, in which a complex formwork or reinforcing bar is used. Of course, it can also be applied to construction on a structure where densely arranged bars.

[0024]

EXAMPLES Hereinafter, the experiments conducted on the compaction-free concrete composition of the present invention will be described. [Preparation of concrete] The materials used are as follows. (1) Cement In Experiment (I), a two-component low heat-generating cement (manufactured by Ube Cement) was used. This cement is composed of low heat generation Portland cement and blast furnace slag fine powder, and has a specific gravity of 3.0.
The Blaine value was 4850 cm ² / g. In the experiment (II), a three-component low heat-generating cement (made by Tokuyama Cement) was used. The cement consists of ordinary Portland cement, ground granulated blast furnace slag and fly ash, and has a specific gravity of 2.
80, and the Blaine value was 5240 cm ² / g.

(2) Fine aggregate In the experiment (I), sea sand from the main island (surface dry specific gravity 2.54, water absorption 2.36, coarse grain ratio 2.39) was used. Experiment (II)
Then, sea sand from Hiroshima, Kagawa prefecture (2.55 surface dry specific gravity, water absorption 1.98, coarse grain ratio 2.56) and crushed sand from Nishijima, Hyogo prefecture (2.55 surface dry specific gravity, water absorption 2.11) , Coarse grain ratio 2.9
7) was mixed at a weight ratio of 8: 2 and used.

(3) Coarse aggregate In the experiment (I), crushed rhyolite from Kamijima (maximum size 40 m
m, surface dry specific gravity 2.64, water absorption rate 0.57, coarse grain ratio 7.2
1) was used. In the experiment (II), crushed stone from Ako, Hyogo prefecture (maximum size 40 mm, surface dry specific gravity 2.63, water absorption rate 0.5
6, the coarse grain ratio 7.10) was used.

(4) Limestone powder The limestone powder used in the experiment (I) had a specific gravity of 2.71, a lime purity of 99.0%, and a Blaine value of 7500 cm ² / g. The limestone powder used in the experiment (II) had a specific gravity of 2.71, a lime purity of 99.1%, and a Blaine value of 5500 cm ² / g.

(5) Admixture In Experiment (I), a modified lignin complex (manufactured by NM) was used as a high-performance AE water-reducing agent, and a modified alkylcarboxylic acid compound (manufactured by NM) was used as an air entrainer.
It was used. In Experiment (II), a modified lignin complex (manufactured by NM) or a polycarboxylic acid ether compound (manufactured by NM) was used as a high-performance AE water reducing agent, and a modified alkylcarboxylic acid compound (manufactured by NM) was used as an air entrainer. )It was used. (6) Water Tap water was used in both experiments (I) and (II).

Concrete was prepared by mixing the above materials as shown in Tables 1 and 2 below. 100 for kneading
A liter twin screw forced mixer was used. In the experiment (I), the unit water amount was kept constant, and the water-cement ratio and the admixture amount of limestone powder were increased or decreased. In Experiment (II), two types of high-performance AE water reducing agents were used, and the unit amount of water and the water-cement ratio were kept constant to increase or decrease the amount of limestone powder mixed. In Table 2, Formulation Nos. 21 to 23 used the high-performance AE water reducing agent of the modified lignin composite, and Formulation Nos. 24 to 26 used the high-performance AE water reducing agent of the polycarboxylic acid ether type composite. In addition, the admixture amount of the admixture was finely adjusted in Experiments (I) and (II) so that the slump flow of the concrete was 55 ± 5 cm and the air amount was 3.5 ± 1%.

[0030]

[Table 1]Experiment (I) recipe W / C Unit amount (kg / m ³ )Admixture Gross weight (C + L) / W L / C Compound No . (%)water C Stone powder (%) (kg / m ³ ) 1 60.5 145 240 90 3.3 2310 0.78 0.41 2 60.5 145 240 120 3.4 2314 0.86 0.55 3 60.5 145 240 150 3.5 2334 0.94 0.70 4 60.5 145 240 180 3.6 2347 1.01 0.84 5 60.5 145 240 210 3.7 2347 1.09 0.98 6 55.8 145 260 90 3.0 2320 0.83 0.38 7 55.8 145 260 120 3.1 2324 0.90 0.51 8 55.8 145 260 150 3.4 2324 0.99 0.64 9 55.8 145 260 180 3.5 2345 1.06 0.77 10 55.8 145 260 210 3.6 2350 1.14 0.90 11 51.8 145 280 90 2.9 2325 0.87 0.35 12 51.8 145 280 120 3.1 2325 0.94 0.47 13 51.8 145 280 150 3.4 2328 1.03 0.60 14 51.8 145 280 180 3.6 2338 1.10 0.72 15 51.8 145 280 210 3.7 2345 1.18 0.84 ＊ W / C: water cement ratio, C: cement ＊ admixture Agent: High-performance AE water reducing agent used for cement
(Wt%) * C: Volume of cement, L: Volume of limestone powder, W: Water
volume

[0031]

[Table 2] Experiment (II) Recipe Table W / C Unit Amount (kg / m ³ ) Total Admixture Weight (C + L) / W L / C Recipe No. ( % ) Water C Stone Powder ( % ) ( kg / m ³ ) 21 53.8 140 260 120 2.9 2294 0.98 0.47 22 53.8 140 260 150 3.1 2296 1.06 0.59 23 53.8 140 260 180 3.4 2297 1.14 0.71 24 53.8 140 260 150 2.7 2296 1.06 0.59 25 53.8 140 260 180 3.0 2297 1.14 0.71 26 53.8 140 260 220 3.0 2298 1.24 0.87 * W / C: Water cement ratio, C: Cement * Admixture: Amount of high-performance AE water reducing agent to cement (wt%) * C: Volume of cement, L: Volume of limestone powder, W : Volume of water

[Test Method and Test Results] The following tests were carried out on each of the above-mentioned mixed samples in order to examine the properties of fresh concrete and the physical properties of hardened concrete. The test items and test methods are as follows. (1) Slump flow test: In a slump test based on JIS A 1101, the spread of concrete on a horizontal flat plate was measured. (2) Air amount test: Based on JIS A 1128. (3) Breathing test: Based on JIS A 1123. (4) Compressive strength test: Based on JIS A 1108.

Tables 3 and 4 below show the properties of the fresh concrete after 5 minutes from the discharge from the mixer and the compressive strength of the hardened concrete after 28 days. In the “Status” column of the table, ○ indicates that the material separation resistance and fluidity are both good by visual observation of fresh concrete, and Δ indicates that the material separation appears to some extent or the viscosity is slightly high. The crosses indicate that material separation has occurred or that it is highly viscous.

[0034]

TABLE 3 Experiment (I) characteristics and properties SF air amount B state compressive strength formulation No. (Cm) (%) (%) (kgf / cm 2) 1 55.5 4.2 0.42 × 291 2 55.0 4.5 0.48 △ 300 3 56.5 4.3 0.42 ○ 305 4 55.0 4.7 0.18 ○ 336 5 55.0 4.5 0.08 ○ 335 6 56.0 4.2 0.50 × 311 7 55.0 4.3 0.40 ○ 318 8 58.0 4.4 0.55 ○ 328 9 59.0 4.2 0.06 ○ 348 10 57.0 4.3 0.0 ○ 362 11 55.0 4.4 0.21 × 344 12 55.0 4.5 0.0 ○ 353 13 56.0 4.4 0.0 ○ 353 14 55.5 3.7 0.0 ○ 390 15 155.0 5.0 0.0 0.0 388 * SF: Slump flow, B: Breathing rate

[0035]

TABLE 4 Experiment (II) Characteristics and properties SF air amount B state compressive strength formulation No. (Cm) (%) (%) (kgf / cm 2) 21 54.0 4.3 2.16 △ 284 22 53.0 4.1 1.53 ○ 292 23 56.0 4.0 1.90 ○ 303 324 55.0 3.7 1.70 ○ 324 25 57.5 3.8 1.20 ○ 329 26 57.0 3.7 0.85 × 330

[0036]

According to the present invention, by mixing a predetermined amount of limestone powder and a high-performance AE water-reducing agent in low heat-generating cement, the fluidity and material separation resistance of concrete with a maximum aggregate size of 40 mm can be improved. It is suitable as a concrete for mass concrete structures because it retains its properties and has sufficient performance in terms of the strength characteristics of hardened concrete, etc. This makes it possible to simplify the placement work,
In addition, the excellent effect that compaction work is unnecessary can be obtained.

In particular, if this compaction-free concrete is applied to anchorages and piers of long bridges, the concrete will flow between anchorages, overcrowded rebars peculiar to piers and steel frames without causing material separation. The area around can be reliably filled.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Okamura Ho, 2-2-E-4 Benten, Urayasu City, Chiba Prefecture (72) Inventor, Katsuyoshi Kanazawa 1-166 Hiraiso, Tarumi-ku, Kobe City, Hyogo Honshu-Shikoku Connecting Bridge Public Corporation First Construction Bureau (72) Inventor Akihiro Abe 5-15 Toranomon, Minato-ku, Tokyo Honshu-Shikoku Communication Bridge Public Corporation Headquarters (72) Inventor Isa Arima 1-1-66 Hiraiso, Tarumi-ku, Kobe-shi, Hyogo Prefecture Honshu-Shikoku Connecting Bridge Public Corporation 1st Construction Bureau (72) Inventor Nobuaki Furuya 1-1 No. 1 Hiraiso, Tarumi-ku, Kobe City, Hyogo Prefecture Honshu Shikoku Connecting Bridge Public Corporation 1st Construction Bureau (72) Inventor Kenjiro Tanaka Tsukuba, Ibaraki Prefecture 1043-1, Onigakubo, Shimoyama, Kumagai Technical Research Institute, Ltd. (72) Inventor, Koichi Sato, 1043-1, Shimoyama, Onigabo, Onigaku, Tsukuba, Ibaraki (72) Inventor Shigeyuki Togawa 2-3 Kandajimachi, Chiyoda-ku, Tokyo Obayashi Corporation Tokyo Headquarters (72) Inventor Ryuichi Chikamatsu 2-3 Kandaji-cho, Chiyoda-ku, Tokyo Obayashi Corporation Tokyo Head office

Claims (2)

[Claims] 1. A mixture of coarse aggregate having a maximum size of 40 mm, low heat-generating cement, unit water amount of 165 kg / m ³ or less, limestone powder and a high-performance AE water reducing agent, and the volume of low heat-generating cement. (C), the volume of water (W), and the volume of limestone powder (L), the following (1) and (2)
A compaction-free concrete composition for a mass concrete structure satisfying the formula. (1) 0.86 ≦ (C + L) /W≦1.18 (2) 0.47 ≦ L / C ≦ 0.98 2. The compaction-free concrete composition for mass concrete structures according to claim 1, wherein the limestone powder has a fineness in a range of 3500 to 9000 cm ² / g in terms of Blaine value. ..