JP2012051741A - Pc grout composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a premix-type ultralow viscosity PC (Prestressed Concrete) grout composition which expresses the high fluidity of ultralow viscosity, does not generate the bleeding even if a grout is injected to an actual PC structure, suppresses curing shrinkage crack with small autogenous shrinkage strain, and has a stable, high strength expression.SOLUTION: The premix-type ultralow viscosity PC grout composition contains 15 mass% or more of early-strength cement, 1.2-4.8 mass% of an expansive material, 0.02-0.1 mass% of a thickener, and 0.2-2.0 mass% of a cement dispersant.

Description

The present invention relates to a premix type PC grout composition. Specifically, the present invention relates to an ultra-low viscosity PC grout composition having excellent fluidity, high material separation resistance, and compressive strength at an age of 28 days exceeding 100 N / mm ² .

  In general, PC grout is used in prestressed concrete bridges as a duct filling material for ducts after tensioning PC steel in the inner cable. In addition to prestressed concrete bridges, PC grout is also used for building structures, container structures, and other internal cables, etc. The required performance is to protect PC steel from corrosion, and PC steel For example, it is possible to integrate the concrete members. Specifically, it is required that there is no material separation and no bleeding, that it has stable fluidity, can be easily injected into the voids, has sufficient compressive strength, and has a low chloride content.

  In recent years, in addition to the above required performance, in order to be able to adapt to the increase in the length of PC structures, the construction is very smooth and easy to clean even in narrow gaps and long spans. ) PC grout material is required. Specifically, it generally has a JP flow time (showing fluidity measured according to the Japan Society of Civil Engineers standard "PC grout test method (JSCEF531-1999)") and a flow time of 14 seconds or more. The type is a low viscosity type for 6 to 14 seconds, and an ultra low viscosity type for 6 seconds or less.

  There are two types of PC grout materials, premix type and admixture type, depending on the method of use in the field. The premix type is a material that premixes PC grout ingredients other than water in advance, reducing labor due to on-site construction, and achieving uniform quality performance. It has the feature of avoiding troubles. On the other hand, the admixture type is a method of mixing on-site procurement cement, admixture, and water on site, and has a feature that it can be constructed at a lower cost than the premix type.

  As a premix type, one having cement, a high-performance water reducing agent, a retarder, and a specific inorganic filler as a PC grout material component is known (for example, Patent Document 1). However, the self-shrinkage is large, and there are significant problems such as a decrease in adhesion to PC steel due to cracks in the sheath tube and occurrence of bleeding. Further, as a technique for suppressing self-shrinkage, a PC grout material mainly composed of cement, an expanding material, calcium carbonate, a high-performance water reducing agent, a retarder, and an antifoaming agent is known (for example, Patent Document 2). However, in many cases including these PC grouts, the polyethylene bag method [JSCE-F532-1999] is carried out as a bleeding rate test. This test method does not take into account the effect of PC steel during grouting on PC structures where PC steel is placed, and even if no bleeding occurs with this method, When injection was applied, there was a big problem that bleeding occurred. Further, PC grout materials made of high belite cement, silica fume, and cement dispersion having ultra-low viscosity and high strength are also known (for example, Patent Document 3). When grout was poured into an object, there was a big problem that bleeding occurred.

On the other hand, as an admixture type, an admixture for PC grout comprising a polycarboxylic acid-based cement dispersant, a thickener, and a lime-based admixture, in which bleeding is suppressed by the bleeding rate test method considering the actual PC structure. Is known (for example, Patent Document 4).
PC grout using this admixture is a stable and high fluidity as a PC grout material that can be adapted to the lengthening of PC structures in recent years (J14 funnel flow time immediately after kneading is less than 4 seconds, 60 minutes have passed) The increase in the subsequent flow time is less than 1 second), a good filling property can be ensured at a low injection pressure, and the separation resistance is excellent, no bleeding occurs, and a high compressive strength is expressed.

JP 1997-30855 A JP 2002-285512 A JP 2003-137634 A JP 2005-314154 A

  However, in recent years, when cement and PC grout admixture procured at the construction site are combined with water and PC grout is kneaded at the site, fluidity is guaranteed due to the influence of the cement character procured at the construction site. There are issues such as inability to do so. That is, the fluidity may vary greatly depending on the quality of the cement procured at the construction site. Generally, commercially available cements are all within the JIS standard range of cement, regardless of brand, manufacturing plant, lot-to-lot (inside), etc., and even when used for general ready-mixed concrete, there is a particular problem. Absent. On the other hand, in recent years, it has been recognized that the character has a tendency to vary greatly, especially due to the acceptance of waste into cement, etc., which affects the fluidity. Furthermore, when used with an admixture for PC grout material, the difference in the character of the cement used greatly affects the fluidity of the PC grout. In particular, the influence of the cement character on the fluidity is more likely to be affected by PC grouts with low viscosity and excellent fluidity. For example, the fluidity is remarkably lowered, and there are cases where poor pumping or construction failure occurs at the construction site, and a large amount of bleeding occurs even if the fluidity is good.

  Therefore, the problem of the present invention is that it exhibits ultra-low viscosity and high fluidity, no bleeding occurs even when grout is poured into an actual PC structure, and the self-shrinkage strain is small, which suppresses hardening shrinkage cracking. Another object of the present invention is to provide a premix type ultra-low viscosity PC grout composition having stable high strength development.

  Therefore, the present inventor has made various studies on the relationship between the characteristics of the premix type PC grout composition and the types and blending amounts of each component. The present inventors have found that a premix type PC grout composition that can solve the above-mentioned problems can be obtained by combining a thickener and a cement dispersant.

That is, the present invention is 15% by mass or more of early-strength cement, 1.2 to 4.8% by mass of an expanding material, 0.02 to 0.1% by mass of a thickener, and 0.2 to 2.0% by mass of a cement dispersant. % Is a premix type ultra-low viscosity PC grout composition.
The present invention also provides an ultra-low viscosity PC grout prepared by kneading the premix type ultra-low viscosity PC grout composition at a water / binder ratio of 30 to 45%.
Furthermore, the present invention is an ultra-low viscosity composition in which 0.001 to 0.08% by mass of an antifoaming agent is mixed in the premix type ultra-low viscosity PC grout composition and kneaded at a water / binder ratio of 30 to 45%. A viscous PC grout is provided.

  If the premix type ultra-low viscosity PC grout composition of the present invention is used, by using it at a specific water binding ratio, the ultra-low viscosity fluidity is expressed, and grout is injected into an actual PC structure. In addition, bleeding is not generated, the self-shrinkage strain is small, and curing shrinkage cracking is suppressed, and an ultra-low-viscosity PC grout having stable and high strength can be obtained. In addition, because it is a premix type PC grout material, it can always implement various PC structures that maintain stable quality performance, protect the PC steel from corrosion, and integrate the PC steel and member concrete. .

It is the schematic of a vertical pipe test. It is the schematic of an inclined pipe test.

  Hereinafter, the present invention will be specifically described. In addition,% is mass% except the case where it shows in particular and the case intrinsic | native to a unit.

  Although it does not specifically limit as (A) early strong cement used by this invention, Generally early strong Portland cement is mentioned. The content of the early strong cement in the premix type ultra-low viscosity PC grout composition of the present invention is 15% or more. If it is less than 15%, when grout is injected into an actual PC structure, particularly at a high temperature, bleeding occurs and the initial strength developability is also deteriorated. 20-80% is preferable and 40-80% is more preferable in order to suppress generation | occurrence | production of bleeding and to ensure a long pot life with ultrahigh flow.

  In addition to the early strong cement, cement and admixtures that can be used for mortar and concrete can be added as long as the effects of the present invention are not impaired. Examples of this cement and admixture include various portland cements such as normal, low heat, medium heat, white, etc., eco cement, and various mixed cements obtained by mixing fly ash, blast furnace slag, silica fume, etc. with these portland cement or eco cement, Examples thereof include gypsum, stone powder, clay mineral powder, slag powder, fly ash, silica fume, inorganic filler, and the like, and one or more of these can be used as long as the effects of the present invention are not inhibited.

The expansion material (B) used in the present invention is not particularly limited, and in general, an ettringite-producing substance such as calcium lime-based expansion material containing calcium oxide and calcium sulfoaluminate as an active ingredient. Representative examples include ettringite-based expansion materials and composite expansion materials of free quick lime and ettringite-producing substances. Of these, quicklime-based expansive materials are generally known to have high hydration reaction activity, and in particular, are excellent in the effect of suppressing large-scale initial shrinkage of concrete.
The content of the expansion material in the premix type ultra-low viscosity PC grout composition of the present invention is 1.2 to 4.8%, more preferably 1.8 to 4.0%. If it is less than 1.2%, the self-shrinkage increases, shrinkage cracks occur in the cured product, and the durability is impaired. If it exceeds 4.8%, there is a risk of poor fluidity, abnormal expansion due to excessive expansion, temperature cracking due to an increase in heat of hydration, etc., which is not preferable.

  The (C) thickener used in the present invention is not particularly limited, and examples thereof include a cellulose thickener, an acrylic thickener, and a guar gum thickener. Of these, cellulose-based thickeners are preferred, and preferred examples include carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, and hydroxypropylcellulose. The content of the thickener in the premix type ultra-low viscosity PC grout composition of the present invention is 0.02 to 0.1%, more preferably 0.025 to 0.065%. If it is less than 0.02%, the thickening effect is poor, and material separation and bleeding occur, which is not preferable. If it exceeds 0.1%, workability is remarkably lowered, and it is difficult to maintain good fresh properties.

  The (D) cement dispersant used in the present invention is not particularly limited, and examples thereof include polycarboxylate-based water reducing agents, naphthalene sulfonate-based water reducing agents, melamine sulfonate-based water reducing agents, and lignin sulfonate-based agents. A water reducing agent is mentioned, These 1 type (s) or 2 or more types can be used. As the water reducing agent to be used, it is preferable to use a high performance water reducing agent or a high performance AE water reducing agent because it is easy to make the grout ultra high strength. In addition, the melamine sulfonate water reducing agent is not easily affected by the water-soluble alkali of the cement, and it is easy to maintain a certain fluidity with respect to the variation of the cement. To preferred. The content of the cement dispersant in the premix type low-viscosity PC grout composition of the present invention is 0.2 to 2.0%, and more preferably 0.5 to 1.5%. If it is less than 0.2%, the effect of the dispersant is poor, and workability is remarkably lowered. If it exceeds 2.0%, the setting time is delayed and bleeding occurs, which is not preferable.

  A small amount of (E) an antifoaming agent can be mixed in the premix type ultra-low viscosity PC grout composition of the present invention. By mixing this antifoaming agent, a slight amount of bubbles in the grout can be eliminated, and the cured product can be further densified. The content of the antifoaming agent in the premix type ultra-low viscosity PC grout composition of the present invention is preferably 0.001 to 0.03%, and more preferably 0.003 to 0.015%. If it is less than 0.001%, the effect of the antifoaming agent is not exhibited, and if it exceeds 0.03%, bubbles are pushed up on the surface, and fragile parts such as skin breakage are generated, which is not preferable.

  In the premix type ultra-low viscosity PC grout composition of the present invention, an aggregate that can be used for mortar or concrete can be used within a range that does not substantially lose the effects of the present invention. For example, river sand, land sand, sea sand, crushed sand, quartz sand, river gravel, land gravel, crushed stone, artificial aggregate and the like can be used. In addition, although the kind of aggregate is not limited, a lightweight aggregate with a large water absorption rate is not preferable.

  The ultra-low viscosity PC grout composition of the present invention is used as a premix material. Therefore, all the components of the ultra-low viscosity PC grout composition of the present invention are mixed in advance to obtain a premix product in a powder form so that a predetermined amount of water is measured and kneaded. The method for premixing the blended components of the ultra-low viscosity PC grout composition of the present invention is not particularly limited, and gravity mixers such as V-type mixers and tiltable concrete mixers, Henschel mixers, ribbon mixers, paddle mixers, etc. Mixed in. In addition, the ultra-low viscosity PC grout composition of the present invention can be premixed by a method of measuring each material directly into a container such as a bag or a polyethylene container.

  In order to produce an ultra-low viscosity PC grout using the premix type ultra-low viscosity PC grout composition of the present invention, it is preferably kneaded at a water / binder ratio of 30 to 45%. If it is less than 30%, the balance between superfluidity and pot life cannot be achieved, and good workability cannot be maintained, which is not preferable. On the other hand, if it exceeds 45%, the occurrence of bleeding and strength development are reduced, which is not preferable.

  The water / binder ratio in the present invention is the mass of water with respect to the total mass of the cement to be the binder and the expander or hydraulic cement admixture (silica fume, fly ash, blast furnace slag fine powder, etc.). . Moreover, the mass of this water is the mass which also combined the water contained in the cement admixture etc. to be used.

  When the ultra-low viscosity PC grout of the present invention is kneaded at the above water / binder ratio, the flow time of JP funnel is 6 seconds or less, and it becomes ultra-low viscosity. If construction is performed using the ultra-low viscosity PC grout of the present invention, bleeding does not occur even when the grout is injected into an actual PC structure, and the self-shrinkage strain is small, which suppresses hardening shrinkage cracks and is stable. And high strength development. Moreover, it is possible to construct various PC structures that always maintain stable quality performance, protect the PC steel from corrosion, and integrate the PC steel and member concrete.

  Examples of the present invention will be described below together with comparative examples, but the present invention is not limited to the examples.

[Example 1 and Comparative Example 1]
The materials used are shown in Table 1. The materials shown in Table 1 were mixed using a Henschel mixer to prepare premix-type ultra-low viscosity PC grout compositions of the present invention (products 1 to 8 of the present invention). In addition, reference products (1 to 10) were also prepared as comparative reference products. Table 2 shows the blending ratio of each of the prepared grout compositions. Each grout composition was kneaded with water for 90 seconds using a grout mixer to prepare a grout material. In addition, all quality tests other than the compressive strength test were performed in a temperature-controlled room at 20 ± 3 ° C. and a humidity of 80% or more. The blending (%) in Table 2 is adjusted to a total of 100% with the most blended cement.

The grout materials of the present invention products (1-8) and reference products (2, 5, 7, 8) prepared in Table 2 were measured and evaluated for fluidity and workability (ensured pot life). Each evaluation test method is shown below.
Fluidity: Measured value of JP funnel flow time according to JSCE F531 “PC grout fluidity test method”. As an indicator of ultra-high flow (ultra-low viscosity), the JP flow time immediately after kneading was 6 seconds or less.
Workability (Securing pot life): The workability is maintained even after 60 minutes, and the measured value of the JP funnel flow time after 60 minutes is 8 as an index to ensure pot life. Less than a second was evaluated as ◯ (good), and 8 seconds or longer was evaluated as x (impossible).

The flowability and workability test results are shown in Table 3. In all the examples of the present invention, the JP funnel flow time immediately after the kneading is 6 seconds or less and the fluidity is excellent, and the JP funnel flow time 60 minutes after the kneading is 8 seconds or less. It was confirmed that it had excellent workability and sufficient pot life, and that workability was good.
On the other hand, in Comparative Example 1-1 in which 7.0% of the expansion material was mixed, the JP funnel flow time immediately after kneading was 6.9 seconds, which was inferior in fluidity, and a tightness was recognized until 60 minutes after kneading. It was. Comparative Example 1-2 with 0.1% cement dispersant, Comparative Example 1-3 with 25% water binder, and Comparative Example 1-4 with 0.15% thickener were kneaded. It was confirmed that JP funnel flow time immediately after climbing was inferior in fluidity as 10 seconds or more, and after 60 minutes from grout kneading, the tightness was remarkably strong and workability (pot life) could not be secured.

[Example 2 and Comparative Example 2]
For the grout materials of the present invention products (1-8) and reference products (1, 4, 6, 9) prepared in Table 2, a bleeding and cured body crack confirmation test was conducted. The evaluation test method is shown below.
Bleeding and cured body crack confirmation test: JHS 420-2004 “Vertical tube test” measured bleeding rate and the presence or absence of cracking after 24 hours of the grout cured body injected into the vertical tube was visually confirmed.

The vertical pipe test will be described below with reference to FIG.
As shown in FIG. 1, first, a strand of PC steel having a length of over 1.7 m is placed in the center of a PVC transparent sheath tube having a height of 1.7 m, an outer diameter of 89 mm, and an inner diameter of 79 mm. Then, the grout immediately after kneading was injected into the sheath tube to a height of 1.5 m using a grout pump. The inlet was tightly closed with a plate wire, the grout length immediately after injection was measured, a seal with a scale indication was attached to the top of the grout (1.5 m), and the grout length was based. The bleeding rate after 3 hours and 24 hours after the base length was measured with a scale attached to the sheath tube, and the bleeding rate was calculated by the following formula.
Bleeding rate (%) = (height of bleeding water) / (height of grout) × 100

  Table 4 shows the results of the bleeding and cured body crack confirmation test. In all the examples of the present invention, bleeding did not occur, and no cracks were observed after 24 hours in the cured grout. In Comparative Example 2-1 in which the expansion material was mixed with 0.8%, although no bleeding was generated, cracking was observed after 24 hours in the cured grout. In Comparative Example 2-2 in which 2.1% of the cement dispersant was mixed, 0.6% bleeding after 3 hours was observed. Further, in Comparative Example 2-3 in which the water binding ratio was 48% and Comparative Example 2-4 in which 0.01% of the thickener was mixed, remarkable bleeding of 1% or more was recognized.

[Example 3 and Comparative Example 3]
A compressive strength test was performed on the grout materials of the present invention products (1-8) and the reference product (3) prepared in Table 2.
The evaluation test method is shown below.
Compressive strength: according to JSCE-G 531 “Test method for compressive strength of PC grout”, compressive strength at age 3, 7, and 28 was measured.

The compressive strength test results are shown in Table 5. The examples of the present invention showed strength development of 60 N / mm ² or more at a material age of 3 days, and an ultrahigh strength of 100 N / mm ² or more was confirmed at a material age of 28 days. Comparative Example 2-1 in which 10% of early strong cement was mixed and low heat cement was used as an admixture material showed low initial strength development, and a low property of 45 days N / mm ^{2 at} 28 days of age.

Example 4 and Comparative Example 4
The material separation resistance test and self-shrinkage of the ultra-low viscosity PC grout composition (invention products 4 and 5, 6 in Table 2) and the comparative reference products (4, 10) in Table 2 which are considered to be more preferable in the present invention The test was conducted. The evaluation test method is shown below.
Material separation resistance test: Material separation resistance was confirmed according to JHS 419-2004 “Inclined tube test”. The inclined tube test will be described below with reference to FIG. 2. As shown in FIG. 2, a PVC transparent sheath tube having a length of about 5 m, an outer diameter of 90 m, and an inner diameter of 79 mm inserted with 12 strands of PC steel is set at an angle of 30. It was installed at a degree, PC grout was injected, and material separation resistance such as generation of bleeding water and movement phenomenon of bleeding water was measured visually.
The index of material separation resistance is shown below.
○: Bleeding is not observed.
Δ: Bleeding water is slightly generated and there is water movement, but it does not concentrate at the upper end.
X: Bleeding water is generated, bleeding is accumulated at the upper end, and material separation occurs.
Self-shrinkage test: Self-shrinkage strain was measured in accordance with JCI standard JCI-SAS3 “Concrete self-shrinkage stress test method (draft)”. At this time, the starting point of the self-shrinkage strain was the initial time.

  Table 6 shows the material separation resistance and self-shrinkage test results. In all of the examples of the present invention, no bleeding was observed after 3 hours and 24 hours, and good material separation resistance was confirmed. The self-shrinkage also showed an expansion of 3 to 100 μm at a material age of 1 day. On the other hand, in Comparative Example 4-1 in which 2.1% of the cement dispersant was mixed, it was confirmed that bleeding was remarkably generated and bleeding was accumulated also at the upper end. Self-shrinkage showed 180μ shrinkage. In Comparative Example 4-2 in which the expansion material was not mixed and the antifoaming agent was mixed in 0.1%, in the material separation resistance test, a slight amount of bubbles and bleeding water appeared on the upper surface of the inclined tube, and a slight movement of water was observed. . As for the self-shrinkage, a large shrinkage of 650 μm was confirmed at the age of 1 day.

According to the present invention, an ultra-low viscosity PC that has ultra-low viscosity, high flow, sufficient work time can be secured, material separation resistance is large, compressive strength exceeds 100 N / mm ² , and self-shrinkage hardly occurs during curing. Since a grout is obtained, it can be suitably used for filling gaps in ducts after tension of PC steel in prestressed concrete bridges, filling parts of super high-rise building joints, super high strength members, etc. .

Claims (3)

  Premix containing 15% by weight or more of early-strength cement, 1.2 to 4.8% by weight of expansion material, 0.02 to 0.1% by weight of thickener and 0.2 to 2.0% by weight of cement dispersant Type of ultra-low viscosity PC grout composition.   Furthermore, the ultra-low-viscosity PC grout composition of Claim 1 which contains 0.001-0.8 mass% of antifoamers.   An ultra-low viscosity PC grout obtained by kneading the premix type ultra-low viscosity PC grout composition according to claim 1 or 2 at a water / binder ratio of 30 to 45%.

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