JP2010006680A - Expansive composition and expansive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide expansive concrete using inexpensive quick lime, necessitating no complicated treatment of finely preparing a plurality of raw materials and usable for mortar concrete for construction in low addition, suppressing the deterioration of strength of the concrete, exhibiting a proper expansion performance and reducing the occurrence of crack in the concrete. <P>SOLUTION: An expansive composition and the expansive material are a powdery composition containing ≥80 mass% free quick lime having 3-60 μm crystal diameter, consisting essentially of quick lime particle having 20-250 mL 4N-HCl activity and having 2,000-3,400 cm<SP>2</SP>/g fineness and containing ≤30 mass% cement and ≤20 mass% gypsum with the free quick lime. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cement composition, such as a concrete concrete structure such as a PC concrete road bridge, a railway bridge deck, a tunnel lining, a railing, a warehouse floor slab, and a general building structure such as a three-dimensional parking lot. The present invention relates to an expandable composition and an expandable material that are mixed for suppression and used for construction.

  In recent years, in order to increase the durability of concrete structures, a concrete expansion material that suppresses cracking of concrete has attracted attention, and demand has been increasing. In particular, in order to reduce cracks, it is effective to use an expanding material, and it is essential to reduce the amount of the expanding material used to reduce the economic burden.

  Two types of expansive materials for concrete are typically used: ettringite-based expansive materials containing ettringite-producing substances such as calcium sulfoaluminate as active ingredients and quicklime-based expansive materials containing free quicklime as active ingredients. Yes. 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. This quicklime expansion material is also known in various formulations and forms depending on characteristics and applications (see, for example, Patent Documents 3 and 4).

  However, with quicklime-based expandable materials, expansion control is difficult because of the large variation in the degree of firing (soft burn, medium burn, hard burn). In addition, when hard calcined lime is used, even if the amount of expansion is small due to various conditions, the strength of the concrete is reduced, or excessive expansion properties are exhibited, and the strength of the concrete may be drastically reduced.

  A solution that solves these problems is a lime-based expansion material. For example, an expandable clinker composition is known in which free lime is generated in a form in which alite is included (see, for example, Patent Document 1). This expandable clinker composition has the characteristics that expansion control is easy and strength reduction is small.

  Further, an ettringite / lime composite expansion material mainly composed of free quick lime and an ettringite-forming substance is also known. (For example, see Patent Document 2)

The expandable composition, in general concrete, is used as a low addition unit type expansion material amount 20 kg / m ^3. On the other hand, in order to adjust the hydration reaction timing and expansion performance of the expansible composition, a finely blended raw material of a plurality of component raw materials is fired into a clinker composition, which is pulverized and manufactured. Yes. Therefore, the cost of raw materials used is high, and the manufacturing cost naturally increases in the manufacturing process. Therefore, the manufacturing cost of mortar / concrete using the expanded material is also increased.

  On the other hand, in addition to the above problem that the conventional quicklime-based expansion material is difficult to control the amount of expansion, those that are manufactured inexpensively using quicklime do not have quality performance for construction use, Limited to product applications. The expansion material for construction is very different from the expansion material for products.For example, the place where expansive concrete is poured is in various construction sites, and the temperature of the environment expands as the expansive concrete that is poured is densified. It is difficult to use quick lime that is sensitive to temperature changes at low cost.

Furthermore, in recent years, the Architectural Institute of Japan has published “Shrinkage Crack Control Design / Construction Guidelines (Draft) / Explanation for Reinforced Concrete Buildings”. In addition, in order to increase the durability of concrete structures, it is predicted that the spread of concrete expansion materials that suppress cracks in concrete will be further predicted in the future. Inflatable materials are being demanded, which is a problem.
Japanese Patent Laid-Open No. 2004-210551 JP 2001-316147 A JP 2005-162565 A JP 2007-45665 A

  The present invention solves the above-described conventional problems, and while using inexpensive quick lime, it is not necessary to delicately prepare a plurality of raw materials as in the past and to perform complicated processing and to suppress an increase in cost. An expandable composition that can be used for construction work with low addition to mortar and concrete, suppresses deterioration of concrete strength, exhibits appropriate expansion performance, and reduces cracks in concrete, and the expandability An expansion material comprising the composition and a mortar / concrete thereof are provided.

The present invention relates to an expandable composition, an expandable material comprising the expandable composition, and mortar / concrete containing these, which have solved the above problems by having the following configuration.
[1] A composition having a free quick lime content of 80% by mass or more and a crystal diameter of the free quick lime of 3 to 60 μm, the main component being quick lime particles having a 4N-HCl activity of 20 to 250 ml. An expandable composition for mortar and concrete.
[2] An expandable composition obtained by pulverizing the composition of [1] to a fineness of 2000 to 3400 cm ² / g.
[3] An expandable material comprising cement and gypsum in the expandable composition of [2] above.
[4] The expansion material according to [3], wherein the cement content is 30% by mass or less and the gypsum content is 20% by mass or less.
[5] The expansion material according to [4], which is blended in a unit amount of 10 to 25 kg / m ³ with respect to mortar / concrete containing cement as a binder phase forming component.
[6] Mortar / concrete containing the expansible composition or expansive material according to any one of [1] to [5] above.

  By using the expansive composition or the expansive material of the present invention for mortar / concrete containing cement as a binder phase forming component, it is possible to impart an optimum expansive effect and effectively suppress cracking of the concrete.

In addition, the expandable composition of the present invention preferably has a fineness of 2000 to 3400 cm ² / g, so that it is comparable to or slightly lower than commercially available cement, so that it has good mixing with cement, and cement and gypsum can be used. The blended material has high expansibility and strength development. Moreover, even when these expansible compositions are used in combination with ordinary Portland cement, cracking of concrete can be effectively suppressed with a lower additive amount (for example, 15 kg / m ³ ).

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

The expansive composition of the present invention is a composition in which the content of free quick lime is 80% by mass or more and the crystal diameter of the free quick lime is 3 to 60 μm, and the 4N-HCl activity is 20 to 250 ml. It is an expandable composition for mortar and concrete characterized by containing particles as a main component, and is obtained by pulverizing the expandable composition to a fineness of 2000 to 3400 cm ² / g.

  The production method of the expandable composition of the present invention is not particularly limited, but is mainly a clinker composition obtained by heating a raw material such as limestone or a pulverized product thereof, and contains 80% or more of free quick lime. If the content of free quicklime is less than 80%, calcium oxide contributing to expansion is insufficient, other impurities are increased, and the expansion and strength performance are adversely affected.

The mineral composition other than free quicklime in the clinker composition is not particularly limited as long as it is less than 20%. In addition, for example, one or more of calcium silicate (C ₃ S), calcium aluminate (C ₃ A), and anhydrous gypsum (CaSO ₄ ), more preferably all three are included as a generated phase. This is preferable because weathering resistance is improved.

  The crystal diameter of the free quick lime contained in the expandable composition of the present invention is 3 to 60 μm, preferably 15 to 40 μm. The crystal diameter of 3 to 60 μm means that the crystal diameter of 3 to 60 μm is 70% or more, preferably 80% or more. The total of the crystal diameters of less than 3 μm and more than 60 μm may be less than 30%, preferably less than 20%.

  The crystal size of free quick lime is important for controlling the hydration activity of quick lime. If there is a lot of free quick lime whose crystal size is smaller than 3 μm, calcium oxide that does not contribute to expansion will increase, and sufficient expansion performance can be obtained. Can not. Moreover, the free quick lime whose crystal diameter exceeds 60 micrometers is dead-burned, and expansion | swelling performance falls. Therefore, when the total amount of free quick lime whose crystal diameter is smaller than 3 μm and free quick lime whose crystal diameter exceeds 60 μm exceeds 30%, it becomes difficult to obtain a desired expansion effect.

  In addition, when the amount of free quick lime whose crystal diameter is smaller than 3 μm increases, it is easily affected by changes in the environmental temperature. For example, when the curing changes from a low temperature environment to a standard environment (20 ° C.), abnormalities are caused by rapid residual expansion. There is a possibility of causing expansion and strength reduction. Further, when the amount of free quick lime whose crystal diameter exceeds 60 μm increases, when the environmental temperature changes under high temperature, the coarsened calcium oxide reacts gradually to cause delayed expansion, which is not preferable.

  Furthermore, the free quicklime contained in the expansible composition of the present invention is mainly composed of quicklime particles having a 4N-HCl activity of 20 to 250 ml. The 4N-HCl activity refers to the activity by 4N-hydrochloric acid titration method. A method for measuring the activity of the swelling substance by the 4N-hydrochloric acid titration method is shown below.

(1) Roughly crush the expanded material and adjust to a particle size of 1 mm to 2.5 mm.
(2) Take 4L of distilled water in a 5L beaker, warm it to 40 ± 2 ° C, set the stirrer so that the stirring blade is 20mm from the bottom of the beaker center, and rotate at 350rpm. Allow to stir.
(3) Add 2-3 drops of phenolphthalein indicator to a beaker.
(4) 100 g of the expanded material whose particle size has been adjusted is placed in a beaker at a time and measurement is started.
(5) Titrate with 4N-hydrochloric acid every 10 minutes after the start of measurement using a 10 ml burette.
(6) Titrate until the neutralized band of the solution is below the 3L scale of the beaker.
(7) The titer is recorded and measured for 10 minutes, and the total titer (ml) of 4N-hydrochloric acid during this period is defined as the activity.

  Hard calcined quicklime with a high degree of sintering having an activity of 20 to 250 ml is preferable because it effectively delays the hydration rate and develops effective hydration expansion. An expanded material having an activity of more than 250 ml is not preferable because the degree of sintering is not high and the initial hydration is remarkable, and the amount of calcium oxide that does not contribute to expansion increases, resulting in a decrease in expansion performance. The activity is more preferably 30 to 150 ml. A product having a high degree of sintering having an activity of less than 20 ml requires a large amount of heat necessary for sintering and takes a firing time, resulting in an increase in manufacturing cost. Moreover, there is a possibility that free quick lime is dead-burned calcified (crystal diameter is 60 μm or more) when it is sintered excessively.

The powdery expandable composition of the present invention is obtained by pulverizing the clinker composition. The fineness (Blaine specific surface area) is preferably ^{2000~3400cm 2 / g, 2300~2800cm 2 /} g is more preferable. If the fineness is less than 2000 cm ² / g, coarse particles of 300 μm or more are mixed and the residual amount of 150 μm is increased, which may cause rough surface and pop-out of the hardened concrete surface, and there are many coarse particles with a large expansion effect. Therefore, there is a concern about overexpansion. On the other hand, before the powder degree exceeds the 3400 cm ² / g, free lime crystals to be milled, the free lime is less having an appropriate crystal size (3~60μm), sufficient curing body tissue is formed May expand and cause excessive expansion and reduced strength.

  In addition, the crystal diameter of the free quick lime contained in the expansible composition powder having the above fineness is suitably in the range of 3 to 60 μm, as before pulverization, and those having a crystal diameter of 3 to 60 μm are 70% or more, Preferably it is 80% or more.

The expandable material of the present invention is obtained by blending cement and gypsum with the above expandable composition (clinker composition powder). Cement and gypsum are used to adjust the expansion performance of the expandable composition. The type of cement is not limited, but an early strong cement with a high C ₃ S content that contributes greatly to the strength development in the hydration process of the early to mid-term concrete is preferable, and a delayed type low heat cement and a blast furnace cement exhibit strength. It is not preferable because of its slow nature.

  The cement content is preferably 30% or less. If the cement content exceeds 30%, the content of the clinker composition, which is an expansion material in the expandable composition, decreases, and an effective expansion amount cannot be exhibited with low addition.

  In addition to the role of adjusting expansion performance, gypsum improves strength development at low temperatures and suppresses long-term drying shrinkage. The content of gypsum in the expansion material is suitably 20% or less, preferably about 5 to 10%. If the gypsum content exceeds 20%, the expansion reaction may be delayed depending on various conditions, resulting in overexpansion and a decrease in strength. Further, the content of the clinker composition that is an expansion material in the expansion composition is high. Since it is relatively lowered and a sufficient expansion effect cannot be obtained, it is not preferable.

Any kind of gypsum may be used for the expansion material of the present invention, but type II anhydrous gypsum is preferable. The anhydrous gypsum used has a fineness of 3000 cm ² / g or more, since the desired reaction activity can be obtained. More preferably, gypsum having a fineness of 6000 cm ² / g or more is preferable. The upper limit of the fineness is not particularly limited, but about 15000 cm ² / g is suitable for the cost of increasing the fineness because the effect is reduced.

The raw material of the clinker composition which is an expansion | swelling component is not limited. Examples of the raw material for the CaO component include quick lime, inexpensive limestone (tankal), and slaked lime, which contain impurities (MgO, Na ₂ O, K ₂ SO _4, etc.) as long as they do not impair the sinterability of the clinker composition. May be.

  The manufacturing method of a clinker composition is not limited. What is necessary is just to manufacture suitably using the heat processing by baking by a rotary kiln, melting by an electric furnace, etc. The clinker composition is manufactured at a firing temperature of 900 to 1500 ° C., although the sintering temperature is not limited because the sinterability varies depending on the mixing ratio of raw materials, particularly the content of impurities.

  The means for mixing the clinker composition with cement and gypsum is not limited. In general, it can be homogenized and mixed by a Henschel mixer or a jet mixer.

The expansion material of the present invention is used in a low additive amount of 10 to ³⁰ kg / m ³ with respect to mortar, concrete or the like containing cement as a binder phase forming component. Even if the expansion material of the present invention is used in a low addition amount of the above unit amount, it has high expansion performance, exhibits effective expansion performance, and can sufficiently exhibit cracking suppression of concrete. In addition, if the unit amount of the expansion material is less than 10 kg / m ³ , the expansion performance is insufficient, and effective cracking cannot be suppressed, and if the unit amount exceeds 30 kg / m ³ , overexpansion may occur and the strength may decrease. Because there is not appropriate.

  The expandable material of the present invention may contain other components that can be used for, for example, mortar and concrete as long as the effect is not substantially lost. Specific examples of such components include various cements, various aggregates, fibers, water reducing agents (including dispersants, high performance water reducing agents, AE water reducing agents, high performance AE water reducing agents, etc.), shrinkage reducing agents, Examples thereof include silica fume, slag, setting accelerator, setting retarder, thickener, water retention agent, rust preventive agent, air entraining agent, antifoaming agent, and foaming agent.

Examples of the present invention are shown below together with comparative examples.
(Preparation of expandable composition)
Using the materials shown in Table 1, the Tankaru powder as a main material, subjected to electric furnace fired at 1300 ° C., to produce a clinker composition shown in Table 2 was ground to a fineness 1800~3920cm ² / g. Gypsum and early-strength cement were mixed with the powdered clinker composition using a Henschel mixer to prepare an expandable composition. Table 3 shows the components of the expandable composition (low addition type expandable material). In addition, the free lime crystal diameter in a clinker composition was confirmed by the composition image using the electron beam microanalyzer (EPMA) apparatus.

  In Table 3, with respect to the preferred range of the present invention, Reference Sample 1 is a sample with an excessively fineness, Reference Sample 2 is a sample with an excessively fineness, Reference Sample 3 is a sample with an excessive amount of gypsum, and Reference Sample 4 is A sample with an excessive amount of cement, reference sample 5 is a sample with a small amount of free quick lime of the clinker composition, and reference sample 6 is a sample with 4N-HCl activity of free quick lime being too high.

[Example I / Comparative Example I]
Concrete containing the expansible composition shown in Table 3 was prepared. Table 4 shows the materials used for the concrete. The amount of unit expansion material in concrete is selected to be less than the conventional low additive type (20 kg / m ³ or less), and the water cement ratio is set to 50.0% and the fine aggregate ratio is 46.4%. Table 5 Concrete was kneaded and mixed. The expansion performance and strength performance of the mixed concrete were confirmed. The expansion performance was in accordance with the standard [Constrained Expansion and Shrinkage Test Method (Method A) in JIS A 6202 Concrete Expansive Material Appendix 2]. The strength performance was in accordance with the standard [JIS A 1108 Concrete Compressive Strength Test Method], and the specimen was prepared in accordance with the standard [JIS A 1132]. The test results are shown in Table 6.

Examples (Sample Nos. 1 to 7) using the expansion material of the present invention (Invention Samples 1 to 6) are low addition unit expansions of 11 to 18 kg / m ³ in the concrete constrained expansion rate of 7 days of age. Exhibits good expansion performance of 153 to 240 μm in terms of the amount of material, and meets the Japan Society of Civil Engineers standards (concrete expansion rate of concrete at 7 days of age: 150 to 250 μm) specified in the “Guideline for Construction of Expanded Concrete” by the above test method. The results were satisfactory, and the quality was good with no reduction in strength.

Comparative sample No. 9 in which the unit expansion material amount in concrete is 25 kg / m ³ or more, Comparative sample No. 11 in which the fineness of the clinker composition is less than 2000 cm ² / g, and the gypsum content in the expansive composition is 30 % Comparative sample No. 12 and free quick lime crystals in clinker composition are small (contains less than 5μ), 4N-HCl activity exceeds 250 ml, and comparative sample No. 15 is over-expanded. And a strength decrease of 10% or more with respect to plain concrete was observed.

Comparative sample No. 10 using a commercial expansion material having a unit expansion material amount (16 kg / m ³ ) equivalent to that of the expansion composition of the present invention, and comparison sample No. in which the cement content in the expansion composition exceeds 30% .13, Comparative Sample No. 14 having a free quicklime content of less than 70% in the clinker composition was insufficient in expansion performance, and the concrete constrained expansion rate at age 7 was 150 μm or less.

Example II / Comparative Example II
Concrete containing the intumescent composition of the present invention of Example I (Invention Samples 1 to 6) and the expandable composition of Reference Sample 2 (Comparative Sample No. 18) in which the fineness of the clinker composition is 3400 cm ² / g or more Were prepared and subjected to expansion and strength performance tests against environmental temperature changes. Since the temperature dependence of calcium oxide, which is a swellable material, is remarkable, lime-based expandable materials are molded at a low temperature (5 ° C) at which the hydration reaction is delayed, cured at low temperatures for 2 days, and then at the standard temperature The temperature change which transfers curing to (20 degreeC) was given. As the cement, blast furnace cement in which the hydration reaction tends to be delayed was used. Table 7 shows the concrete composition. In the same manner as in Example 1, the expansion performance and strength performance of the mixed concrete were confirmed. The test results are shown in Table 7 and FIG.

Samples Nos. 11 to 17 using the expandable composition of the present invention (Invention Samples 1 to 6) have a severe temperature change from a low temperature environment (5 ° C.) to a standard environment (20 ° C.) accompanying the early age of the material. Without depending, it satisfied the civil engineering society standard 150-250 × 10 ⁻⁶ with 7 days expansion rate. Moreover, the compressive strength was almost the same as that of plain concrete, and no decrease in strength was observed.

On the other hand, comparative sample No. 18 using an expandable composition (reference sample 2) having a fineness of clinker composition of 3400 cm ² / g or more is rapidly expanded immediately after the curing is transferred to the standard environment (20 ° C.). An expansion of 200 × 10 ⁻⁶ or more was observed at a material age of 3 days.

[Example III / Comparative Example III]
Using the most preferred expansible composition in the present invention, concrete was prepared using a commercially available expansive material as a comparative sample, a length change test was performed, and the amount of drying shrinkage was measured. The materials used were the same as in Example 1. Table 8 shows the concrete composition. The length change test conformed to the standard [Constrained Expansion and Shrinkage Test Method (Method B) in Appendix 2 of JIS A 6202 Concrete Expansion Material]. The test results are shown in FIG.

Sample Nos. 21 and 22 using the intumescent composition of the present invention product (Examples 4 and 5) have an expansion amount of 200 to 240 × 10 ^{−6 at} 7 days of age with a unit expansion material amount of 15 kg / m ³ added. The dry shrinkage amount at the age of 6 weeks was about 300 × 10 ⁻⁶ , and the drying shrinkage reduction effect equivalent to that of Comparative Sample No. 24 to which 20 kg / m ^{3 of} a commercially available expansion material was added was brought about. On the other hand, Comparative Sample No. 23 to which a commercially available expansion material was added at a unit expansion material amount of 16 kg / m ³ had a small expansion amount of 120 × 10 ⁻⁶ and a dry shrinkage amount of 400 × 10 ⁻⁶ at 6 weeks of age. The amount of reduction in drying shrinkage was also small.

Graph showing the results of Example II and Comparative Example II Graph showing the results of Example III and Comparative Example III

Claims (6)

A composition in which the content of free quick lime is 80% by mass or more and the crystal size of the free quick lime is 3 to 60 μm, and the main component is quick lime particles having 4N-HCl activity of 20 to 250 ml. An expandable composition for mortar and concrete.
An expandable composition obtained by pulverizing the composition of claim 1 to a fineness of 2000 to 3400 cm ² / g.
An expandable material comprising cement and gypsum in the expandable composition of claim 2.
The expandable material according to claim 3, wherein the cement content is 30% by mass or less and the gypsum content is 20% by mass or less.
The expansion material according to claim 4, which is blended in a unit amount of 10 to 25 kg / m ³ with respect to mortar and concrete containing cement as a binder phase forming component.
The mortar concrete containing the expansible composition thru | or expansion | swelling material in any one of Claims 1-5.

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