JP2007254987A - Method of improving fluidity of grout material using low-heat portland cement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple method for improving fluidity of a grout material to ensure excellent workability of the grout material using low-heat portland cement. <P>SOLUTION: Fluidity of the grout material can be improved by mixing hydroxy carboxylic acid and/or hydroxy carboxylic acid salt in the grout material using the low-heat portland cement. It is preferable to mix 0.01-0.1 pts.mass of hydroxy carboxylic acid and/or hydroxy carboxylic acid salt in 100 pts.mass of hydraulic inorganic powder containing low-heat portland cement and a calcium sulfoaluminate expanding material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for improving the flowability of grout materials using low heat Portland cement, and in particular, used for cross-sectional repair or thickening of concrete structures deteriorated due to deterioration phenomena such as neutralization, salt damage, alkali aggregate reaction, and frost damage. To improve the fluidity of grout materials using low heat Portland cement used in the repair and reinforcement of concrete structures such as seismic reinforcement of piers made of reinforced concrete structures and under-surface pressure boosting methods of road slabs .

In general, it is desirable that the material used for the repair / reinforcement method of the concrete structure be as similar as possible to the mechanical properties of the material of the target concrete. Therefore, a cement-based material is preferably used.
Also, spraying and grout filling methods are used to repair and reinforce large sections of concrete structures. However, it is possible to cast and reduce the human burden, and the grout filling method is highly stable by manual operation. However, it has been applied to large-scale repairs and reinforcements.

However, the cement-based grout material is an excellent repair material in that it has sufficient form filling properties, strength, and the like, but has a drawback that cracks are likely to occur in the cross-section after repair due to various causes.
If a crack occurs in the cross section after repair, deterioration factors such as water, carbon dioxide gas, and chloride ions enter from the crack, resulting in a secondary problem that the cross section after repair gradually deteriorates.

By the way, various causes of cracks in the repaired cross section include temperature stress due to cement contained in the unit volume of cementitious grout material, self-shrinkage due to cement hydration, cross section after repair (hardened body) This is caused by shrinkage due to evaporation of moisture from the water.
Cracks caused by self-shrinkage due to cement hydration and drying shrinkage due to moisture evaporation from the repaired cross-section (hardened body) can be solved to some extent by using an expansion material or drying shrinkage reducing agent. (Patent Document 1).

Further, in order to reduce temperature stress due to heat of hydration caused by cement, there is a method of increasing the amount of dry silica sand as an aggregate to reduce the amount of unit cement, but there is a problem that material separation is likely to occur.
In view of this, a method using a low heat type cement that has a small initial heat generation amount and can reduce temperature stress has been proposed (Patent Documents 2, 3, and 4).

In view of such a point, as a grout material used for repair and reinforcement of a large cross section of a concrete structure, Patent Document 1 (Japanese Patent Laid-Open No. 2002-285153) discloses cement, classified fly ash having a specific specific surface area. And a cement-type grout material composition containing 100 parts by mass of a cement-based inorganic powder containing a calcium sulfoaluminate-based expansion material, 1 to 5 parts by mass of a drying shrinkage reducing agent, and 120 to 200 parts by mass of a fine aggregate. It is disclosed.
However, the cement used in this document is not particularly limited, and when low heat Portland cement is used, the fluidity is insufficient only with the disclosed technique.

Patent Document 2 (JP-A-8-268744) discloses Portland cement 27 to 47 parts by mass, granulated blast furnace slag powder 20 to 40 parts by mass, calcium carbonate fine powder 20 to 30 parts by mass, activated siliceous fines. Composition of 2 to 8 parts by weight of powder, 1 to 3 parts by weight of cement-based expansion material, 1 to 3 parts by weight of anhydrous gypsum, 0.3 to 1 part by weight of cement dispersant, and 0.05 to 0.2 parts by weight of curing retarder A low heat-type non-shrinkable filler for FRP-coated concrete repair method having the following is disclosed.
However, the adiabatic temperature rise test of this document shows a value of 50 ° C. or higher, and the temperature stress due to heat of hydration caused by cement cannot be sufficiently reduced.

Patent Document 3 (Japanese Patent Application Laid-Open No. 2003-89563) describes a water cement ratio (W / C) of 65 to 40% using low heat Portland cement and fine aggregate, and a mass ratio to the cement of 0.8 to 1.7% high-performance AE water reducing agent and 25 to 45 kg / m ^{3 of} an expanding material are blended, the mortar slump flow is 20 to 30 cm as a fresh property, and the drying shrinkage after curing is 8 × 10 ^-4 or less is disclosed.
In this document, low heat Portland cement is used. However, in the disclosed technique, the fluidity is remarkably lowered at the initial stage after kneading, and the fluidity is insufficient.

Furthermore, Patent Document 4 (Japanese Patent Laid-Open No. 2005-179781) discloses that the amount of belite in the clinker mineral composition is 45 to 75% by mass, the aluminate phase is 4.0% by mass or less, and the specific surface area is 3000. To 4500 cm ² / g is disclosed a high-strength cement composition comprising 70 to 84 parts by mass of low heat Portland cement and 16 to 30 parts by mass of silica fume.
In the technique disclosed in this document, instead of a material that can measure the flow time of J ₁₄ funnel, poor fluidity.

When the low heat Portland cement is used, the initial heat generation amount is small, so that the temperature stress can be reduced. However, as a physical property peculiar to the low heat Portland cement, there is a problem that the fluidity is remarkably lowered in the initial kneading time. There has been a demand for the development of a simple method for improving the fluidity of a grout material using a low heat Portland cement that solves such problems.
JP 2002-285153 A JP-A-8-268744 JP 2003-89563 A JP 2005-170781 A

Accordingly, an object of the present invention is to provide a simple method for improving the fluidity of a grout material in order to ensure good workability even with a grout material using low heat Portland cement.
Another object of the present invention is to provide a method for improving the fluidity of a grout material using a simple low heat Portland cement which improves good early strength development and long-term strength sustainability.

In order to solve the above-mentioned problems of the prior art, the present invention has been found that the fluidity can be remarkably improved even if it is a grout material using a low heat Portland cement by blending a specific component.
That is, the fluidity improving method of a grout material using the low heat Portland cement according to claim 1 of the present invention is characterized by blending oxycarboxylic acid and / or oxycarboxylate.
A method for improving the fluidity of a grout material using the low heat Portland cement according to claim 2, wherein the grout material using the low heat Portland cement according to claim 1, further comprising an alkali carbonate, an alkali hydrogen carbonate and an alkali sulfate. It is characterized by blending at least one selected from the group consisting of compounds.

  The flowability improving method of a grout material using the low heat Portland cement according to claim 3 is the flowability improving method of a grout material using the low heat Portland cement according to claim 1 or 2, wherein the low heat Portland cement and calcium sulfate are used. 0.01 to 0.1 parts by mass of oxycarboxylic acid and / or oxycarboxylate is added to 100 parts by mass of the hydraulic inorganic powder containing the aluminate-based expansion material.

  The method for improving the fluidity of a grout material using the low heat Portland cement according to claim 4 is the method for improving the fluidity of a grout material using the low heat Portland cement according to claim 2 or 3, wherein the low heat Portland cement and calcium sulfate are used. Mixing 0.5 to 3 parts by mass of at least one selected from the group consisting of alkali carbonates, alkali hydrogen carbonates and alkali sulfate compounds with respect to 100 parts by mass of the hydraulic inorganic powder containing the aluminate-based expansion material. Features.

  In the method for improving the fluidity of a grout material using the low heat Portland cement of the present invention, even when the low heat Portland cement is used, it is possible to easily suppress the decrease in fluidity, and the conventional cement-based grout material Compared to the above, it has the same or better fluidity, but can prevent material separation phenomenon, and has excellent effect on suppressing or preventing cracking due to temperature stress in the cross section after repair of concrete structure. In particular, good workability on site can be secured.

  Furthermore, in the method for improving the fluidity of grout materials using the low heat Portland cement of the present invention, in addition to the above effects, even when used for construction work such as repairing concrete structures, the strength development is quick and strong. Long-term sustainability is possible.

The present invention will be described below using an optimal example, but is not limited thereto.
In the method for improving the fluidity of a grout material using the low heat Portland cement according to the present invention, an oxycarboxylic acid and / or an oxycarboxylate salt is added to the grout material using the low heat Portland cement, so that As a physical property, it is a method capable of suppressing a significant decrease in fluidity in a short time in the initial stage of kneading.

As a cement used for the low heat Portland cement grout material which is the object of the fluidity improving method of the present invention, the kind is not particularly limited as long as it is a known low heat Portland cement, and one or more commercially available products are mixed. Can be used.
When using 2 or more types together, a mixing rate is not specifically limited, It can set suitably.
Here, the low heat Portland cement in this specification refers to, for example, a general low heat Portland cement specified in JIS.

By using the low heat Portland cement, the strength development is slow compared with ordinary Portland cement, but the hydration reaction progresses gently, so the temperature rise rate is reduced, the temperature rise of the concrete structure is suppressed, and the self-shrinkage In addition, the volume change can be reduced.
Therefore, the volume change of the concrete structure accompanying the temperature rise due to the hydration reaction of ordinary Portland cement can be prevented, and the occurrence of cracks in the concrete due to the volume change can be suppressed.

Specifically, since the low heat Portland cement grout material uses low heat Portland cement, 3CaO · SiO ₂ (C ₃ S) has higher hydration activity and higher enthalpy than grout material using ordinary Portland cement. Low heat Portland cement was used because it contains a small amount of 3CaO · Al ₂ O ₃ (C ₃ A), a relatively low hydration activity, and a small amount of enthalpy 2CaO · SiO ₂ (β-C ₂ S). The grout material has the effect that the calorific value associated with the initial hydration is reduced, and this makes it possible to effectively prevent cracking due to temperature stress.
This is because the heat of hydration is generally accumulated with cement hydration, and the temperature difference between the center part of the expanding grout member and the surface part where heat dissipation is large becomes large. As a result, surface cracks are generated. Therefore, in order to prevent cracks due to temperature stress, it is necessary to have a low calorific value, and this will be clarified by a simple adiabatic temperature rise test described later.

Furthermore, the shrinkage of the hardened body is caused by the drying shrinkage due to the capillary tension that acts when the capillary is formed in the hardened body as the cement hydrate is formed and the capillary water evaporates, and the cement and water before hydration. Both the self-shrinkage caused by the physical reduction of the volume of hydrate produced by hydration than the total amount can be considered, and when using low heat cement, the initial hydration is slow, Since the capillary gap is small and C ₃ S and C ₃ A having a large amount of self-shrinkage are small in the constituent components, they function advantageously with respect to the two shrinkages.

The low heat Portland cement may be mixed with various mixed materials usually used in the field.
Examples thereof include known cement mixed materials such as blast furnace slag fine powder, fly ash, silica fume, limestone powder, quartz powder, dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum.
When mixing these mixed materials, the mixing ratio is not particularly limited as long as the effects of the present invention are not adversely affected, and can be set as appropriate.

Further, the grout material in the fluidity improving method of the present invention preferably contains a calcium sulfoaluminate-based expansion material in addition to the low heat Portland cement as the hydraulic inorganic powder. The inflatable material is not particularly limited as long as it can appropriately expand the cross section after repair and can compensate for cracks due to drying shrinkage, and one or more known materials can be used.
What is necessary is just to adjust suitably as a hydraulic inorganic powder further so that the sum total of the low heat | fever Portland cement which mixed the said cement mixed material and the calcium sulfo aluminate type | system | group expansion material may be 100 mass parts as needed.

The ratio of the calcium sulfoaluminate-based expandable material is not particularly limited, but the calcium sulfone aluminate is usually used in a total amount of 100 parts by mass of the low heat Portland cement and the calcium sulfoaluminate mixed with the cement mixed material as necessary. The aluminate-based expansion material is preferably about 1 to 5 parts by mass, and more preferably 1.5 to 3 parts by mass.
If the ratio of the calcium sulfoaluminate-based expansion material in the hydraulic inorganic powder is less than the above range, cracks due to drying shrinkage may not be effectively compensated, and the calcium sulfoaluminum may not be compensated. If the proportion of the nate-based expandable material exceeds the above range, the repaired cross section may expand excessively, possibly causing cracks.

In the method for improving the fluidity of a grout material using the low heat Portland cement of the present invention, the grout material using the low heat Portland cement has a significant decrease in fluidity. An acid and / or oxycarboxylate is blended.
Specifically, in the method for improving the fluidity of the grout material of the present invention, oxycarboxylic acid and its salts are blended for the purpose of ensuring the initial fluidity from kneading to placing of the grout material.

Examples of these materials include citric acid, trisodium citrate, tartaric acid, disodium tartrate, sodium potassium tartrate, gluconic acid, and sodium gluconate.
The compounding amount of the oxycarboxylic acids is such that at least one oxycarboxylic acid or oxycarboxylate is used with respect to 100 parts by mass of the hydraulic inorganic powder containing the low heat Portland cement and the calcium sulfoaluminate-based expansion material. The total amount is preferably 0.005 to 0.1 parts by mass, and more preferably 0.01 to 0.08 parts by mass.
When the blending amount of the oxycarboxylic acids is less than the above range, the initial fluidity of the grout material is remarkably lowered, and when it exceeds the above range, the setting of the cement is significantly delayed.

Furthermore, in addition to blending the oxycarboxylic acid and / or oxycarboxylate, the method for improving the fluidity of a grout material using the low heat Portland cement of the present invention comprises an alkali carbonate, an alkali hydrogencarbonate and an alkali sulfate compound. It is desirable to blend at least one hydration accelerator selected from the group consisting of:
By blending the hydration accelerator into a grout material using low heat Portland cement, it becomes possible to suppress a decrease in the initial strength at which the hydration reaction becomes relatively slow by using the low heat Portland cement. It is also possible to compensate.
Examples of the hydration accelerator that can be used include sodium carbonate, potassium carbonate, lithium carbonate, sodium hydrogen carbonate, lithium sulfate and the like.

Further, the blending amount of the hydration accelerator is at least alkali carbonate, alkali hydrogen carbonate or lithium sulfate with respect to 100 parts by mass of the hydraulic inorganic powder containing low heat Portland cement and / or calcium sulfoaluminate-based expansion material. It is preferable to use 1 or more types and the total amount is 0.1 to 3 parts by mass, and more preferably 0.8 to 2 parts by mass.
This is because if the blending amount of the hydraulic accelerator is too small, the initial strength reduction cannot be suppressed or the initial strength cannot be compensated, and if too large, the initial fluidity of the grout may be lowered.

Furthermore, in the low heat Portland cement grout material used in the method of the present invention, the total amount of the low heat Portland cement mixed with the cement mixed material as described above and the calcium sulfoaluminate-based expansion material is 100 parts by mass. On the other hand, it is preferable that 1 to 5 parts by mass of a drying shrinkage reducing agent is blended.
When the blending amount of the drying shrinkage reducing agent is less than the above range, the sufficient drying shrinkage reducing effect may not be exhibited. On the other hand, even if the blending amount of the drying shrinkage reducing agent exceeds the above range, it may be blended in a large amount. This is because the drying shrinkage reduction effect is almost the same and is not economical.

The drying shrinkage reducing agent is not particularly limited as long as it can suppress or prevent the drying shrinkage of the cross section after repair by reducing the surface tension of water contained in the grout material. Can be used.
Examples thereof include lower alcohol alkylene oxide adducts, glycol ether / amino alcohol derivatives, polyethers, and low molecular weight alkylene oxide copolymers. These drying shrinkage reducing agents can be used alone or in combination of two or more. .
When two or more types are used in combination, the combination ratio is not particularly limited and can be set as appropriate.

Furthermore, in the low heat Portland cement grout material used in the method of the present invention, it is preferable that 120 to 200 parts by mass of fine aggregate is mixed with 100 parts by mass of the above-mentioned hydraulic inorganic powder.
When the amount of fine aggregate is less than the above range, the amount of unit cement in the grout material composition increases, and cracks are likely to occur in the repaired cross section due to temperature stress.
On the other hand, when the amount of fine aggregate exceeds the above range, it tends to cause an increase in drying shrinkage due to an increase in the water / cement ratio, a decrease in material separation resistance, a decrease in strength development of the grout material, etc. There is.

The fine aggregate is not particularly limited as long as it does not reduce the durability of the repaired cross section (cured body), and a known or commercially available product can be used.
Examples of the fine aggregate include dry silica sand, limestone sand, river sand, and crushed sand, which are generally known as fine aggregates for mortar or concrete, as defined in JAS S5.
Further, the particle size of the fine aggregate is not particularly limited and can be appropriately set. However, it is usually preferably 5 mm or less, and more preferably 3 mm or less when considering the filling property into the gap.

The grout material used in the present invention can be mixed with known chemical admixtures such as a high-performance water reducing agent, an antifoaming agent and a foaming agent as long as the effects of the present invention are not impaired.
These chemical admixtures can be used alone or in combination of two or more, and the mixing ratio of the chemical admixture or the combined use ratio in the case of using two or more kinds in combination is not limited and is preferably used while being adjusted as appropriate. .

The grout material used in the method of the present invention is obtained by kneading a grout material composition containing the above material and water, and preferably 30 to 30 parts by weight of water per 100 parts by weight of the hydraulic inorganic powder. It is obtained by blending 40 parts by mass and uniformly kneading.
Specifically, for example, the above-described grout material composition is obtained by blending a predetermined amount of water and kneading, and up to the construction site of the grout material, for example, a bag-packed grout material composition. It can be transported in a state, and a desired amount of grout material can be efficiently prepared at the time of construction.

The fresh property of the low heat Portland cement grout material obtained in this way provides high fluidity with a flow time of 6 to 10 seconds in a J funnel (J ₁₄ funnel) test at the lower end inner diameter. The range is necessary to obtain a predetermined fluidity. If it exceeds 10 seconds, the high fluidity necessary for filling cannot be obtained, and if it is less than 6 seconds, material separation may occur.
In addition, the grout material of the present invention has a high fluidity with a lower end inner diameter of 6 to 15 seconds in the J funnel test (J ₁₄ funnel test) even after 30 minutes after kneading. Thereby, predetermined workability and excellent workability can be ensured.

In addition, the low heat Portland cement grout material with improved initial strength in addition to the improvement of fluidity produced a grout material cylinder specimen of φ5 × 10 cm in accordance with the provisions of the Japan Highway Public Corporation test method “JHS 312-1992” described later. , age of 1 day, compressive strength measured after 4 weeks, and a 5N / mm ² or more in a day the age, also a 35~50N / mm ² at an age of 4 weeks. As a result, it is clear that early strength development is excellent and long-term high strength maintenance is provided.

The present invention will be specifically described with reference to the following examples and comparative examples.
(Materials used)
Low heat Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd.)
Normal Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd.)
Calcium sulfoaluminate-based expansion material (trade name “Sachs” manufactured by Sumitomo Osaka Cement Co., Ltd.)
Drying shrinkage reducing agent (trade name “TECTA F # 100” manufactured by Sumitomo Osaka Cement Co., Ltd.)
Lithium carbonate (Nippon Chemical Industry Co., Ltd.)
Sodium gluconate (manufactured by Kanto Chemical Co., Inc.)
Dry quartz sand (silica sand No. 3)
High performance water reducing agent (Mao 100, Kao Corporation)
Antifoaming agent (Adecanate B211F manufactured by Asahi Denka Kogyo Co., Ltd.)
Water (tap water)

(Examples 1 and 2 and Comparative Examples 1 to 3)
According to the mixing ratio shown in Table 1, each material and water were kneaded using a high-speed hand mixer to prepare a grout material.
Flowability of the resulting grout material, by adding a superplasticizer and defoamer, was adjusted to J ₁₄ funnel flow time is 8 ± 2 seconds or less (proper range).

When the blending amount of the high-performance water reducing agent is increased, the fluidity of the grout material is improved and the amount of mixed air is increased. Therefore, the antifoaming agent is blended for the purpose of defoaming the entrained air.
Evaluation of fluidity caused by the addition of superplasticizer J ₁₄ funnel, if enough defoamers defoaming is blended is evaluated by measurement of the unit volume weight of Table 1.
The specific adjustment method, J ₁₄ flow time was adjusted to a proper range by blending only first superplasticizer, measured unit volume mass of the time, then anti-foaming agent This is done by determining the upper limit of the amount by which the unit volume mass increases.
_However, adjustment of the fluidity of the grout by _{J 14} funnel flow time performed according to the provisions of the Japan Highway Public Corporation Test Method "JHS 312-1992", the resulting _{J 14} funnel flow time are shown in Table 1.

  Next, with respect to the grout materials of the above Examples 1 and 2 and Comparative Examples 1 to 3 whose flowability was adjusted to an appropriate range, (1) material separation resistance test, (2) compressive strength test, (3) simple Each test of the adiabatic temperature rise test was carried out in a constant temperature room at 20 ° C. according to the following method, and the results are shown in Table 1.

(How to perform each test)
(1) Material separation resistance test A sufficiently kneaded grout material was placed in a container having an internal volume of 5 liters and allowed to stand for 1 hour after kneading, and the presence or absence of fine aggregate separation and bleeding was visually confirmed.

(2) Compressive strength test In accordance with the regulations of the Japan Highway Public Corporation test method "JHS 312-1992", a grouting material cylindrical specimen having a diameter of 5 x 10 cm was prepared, and the compressive strength after 1 day and 4 weeks of age was measured.

(3) Simplified cross-sectional temperature rise test A grout material is placed on a cylindrical frame of φ10 x 20 cm and placed in a container sealed with styrofoam with a thickness of 10 cm, and the maximum temperature reached at the center of the grout material is measured by a thermocouple. It was measured by.

Moreover, in Comparative Example 1 and Comparative Example 2, since gluconic acid sodium gluconate is not blended, 30 minutes have elapsed although the initial fluidity of the obtained grout material is within the above-described appropriate range. Later fluidity was significantly impaired.
In Comparative Example 3, since the ordinary Portland cement was used, the simple heat insulation temperature increase was larger than that in the case of using the low heat Portland cement, and the length change rate was larger.

On the other hand, in Examples 1 and 2, when the fluidity of the grout is proper range (J ₁₄ funnel flow time 8 ± 2 seconds), separated and bleeding dry quartz sand (fine aggregate) was not at all observed .
In the simple adiabatic temperature rise test, the maximum temperature at the center of the grout material is less than 50 ° C., and cracks due to temperature stress can be effectively suppressed or prevented.
Moreover, also about the length change test, it is a result superior to the comparative example 3 which uses normal Portland cement by using low heat Portland cement.
Furthermore, it can be seen that the compressive strength in Example 2 is excellent in initial strength and long-term strength.
Thus, in the Examples, it is clear that the fluidity of the grout material using the low heat Portland cement is improved.

The flowability improvement method of the grout material using the low heat Portland cement of the present invention can easily improve the fluidity of the low heat Portland cement grout material that can reduce the temperature stress because the initial calorific value is small. The resulting grout material should be effectively applied to concrete structures, especially for reinforced concrete bridges with seismic reinforcement, and for repairing and reinforcing concrete structures by the method of increasing the bottom of road decks. Can do.

Claims (4)

A method for improving the fluidity of a grout material using a low heat Portland cement, characterized by comprising oxycarboxylic acid and / or oxycarboxylate. Furthermore, the fluidity improvement method of the grout material using the low heat Portland cement of Claim 1 characterized by mix | blending at least 1 sort (s) chosen from the group which consists of an alkali carbonate, an alkali hydrogencarbonate, and an alkali sulfate compound. 0.01-0.1 part by mass of oxycarboxylic acid and / or oxycarboxylate is added to 100 parts by mass of hydraulic inorganic powder containing low heat Portland cement and / or calcium sulfoaluminate-based expansion material. A method for improving the fluidity of a grout material using the low heat Portland cement according to claim 1 or 2. At least one selected from the group consisting of alkali carbonates, alkali hydrogen carbonates and alkali sulfate compounds is added to 100 parts by mass of the hydraulic inorganic powder containing the low heat Portland cement and / or calcium sulfoaluminate-based expansion material. A method for improving the fluidity of a grout material using the low heat Portland cement according to claim 2 or 3, wherein 5 to 3 parts by mass are blended.