JP2007045647A - Cement composition, concrete, and method for producing the cement composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cement composition which exhibits excellent flowability stably immediately after kneading and also causes little change with time in flowability without depending on the brand (kind) of dispersants, in concrete having a low water/cement ratio and using a polycarboxylic acid-based dispersant. <P>SOLUTION: The cement composition contains cement clinker and gypsum. In the cement composition, the content of hemihydrate gypsum is 0.2-3.5 mass%, the ratio of the amount of the hemihydrate gypsum to the total amount of the hemihydrate gypsum and dihydrate gypsum is 50-95 mass%, and the content of water-soluble alkali is 0.17-0.32 mass%. The particles obtained by pulverizing the cement composition have a stuck water amount of 0.003-1.0 mass% based on the cement composition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cement composition containing a cement clinker and gypsum, specifically, in a low water cement ratio concrete using a polycarboxylic acid-based dispersant, excellent in fluidity immediately after mixing with water. The present invention also relates to a cement composition that enables the production of concrete having a small change in fluidity with time.

  In recent years, the use of high-strength concrete and high-fluidity concrete is increasing due to diversification and sophistication of required performance for building structures and the like. In such concrete, in order to obtain high fluidity, many polycarboxylic acid-based dispersants are used.

  In general, a polycarboxylic acid-based dispersant is excellent in dispersion performance and also in sustainability of the dispersion effect. However, it is known that the effect of the polycarboxylic acid dispersant is strongly influenced by the properties of the cement composition (Non-Patent Document 1). For this reason, depending on the cement production plant or production lot, the amount of polycarboxylic acid-based dispersant added to obtain a predetermined fluidity in a cement kneaded product, such as cement paste, mortar, or concrete, may vary, The problem is that the change in flowability of the kneaded material with time increases.

  Further, in order to improve the durability of a building structure or the like, concrete having a low water cement ratio (= water + dispersant (mass%) / cement composition (mass%) × 100%), for example, a water cement ratio of 0.1. The use of less than 40% concrete is increasing. As the water-cement ratio decreases, the effects of the composition and content of the cement composition and the type and content of the polycarboxylic acid dispersant on the fluidity of the concrete become more pronounced. It is difficult to manufacture stably.

As a method for improving fluidity when using a polycarboxylic acid-based dispersant, Patent Document 1 discloses that a mixture of cement clinker powder and gypsum in which the amount of C ₃ A is more than 5% by weight and not more than 15% by weight. , High-flowing water composed of Portland cement, cement dispersant and water containing gypsum so as to satisfy the following formula (1) in terms of SO ₃ and having a hemihydrate gypsum content satisfying the following formula (2) in terms of SO ₃ A hard composition is disclosed.
0.02A + 1.00 ≦ B ≦ 0.20A + 2.00 (1)
C ≦ 0.02A + 0.90 (2)
Here, A is the amount of C ₃ A (% by weight) in the cement clinker, B is the gypsum content in the cement composition (SO ₃ equivalent weight%), and C is the content of hemihydrate gypsum in the cement composition (SO _{3 3} equivalent weight%). And, the cement paste having a water cement ratio of 27% using the polycarboxylic acid-based dispersant has improved fluidity, in particular, temporal change in fluidity.

Further, Patent Document 2, at a rate of hemihydrate gypsum occupying the total amount of gypsum and hemihydrate gypsum cement composition is converted to SO ₃ in 70 wt% or more, and semi water gypsum content SO ₃ A hydraulic composition containing Portland cement in excess of 1.2% by mass, a polycarboxylic acid-based high-performance water reducing agent (dispersant) and water is disclosed, and a water cement ratio using a polycarboxylic acid-based dispersant is 32. The mortar of 5 to 35% and the concrete of 37% of the water cement ratio have improved change in fluidity with time.

  Further, Patent Document 3 discloses a hydraulic composition containing a polycarboxylic acid-based water reducing agent, wherein the hydraulic binder is Portland cement having a water-soluble alkali content of 0.25% or less. , And mortar with a 37% water cement ratio has improved flow over time.

However, although the hydraulic composition of Patent Document 1 has good fluidity with cement paste, it has been pointed out that the aging of fluidity becomes large with mortar and concrete. In particular, the fluidity of concrete containing fine aggregates and aggregates in cement, particularly concrete with a water cement ratio of 40% or less using a polycarboxylic acid dispersant, is different from the fluidity of cement paste and mortar, The problem is that it is difficult to obtain concrete having fluidity of a predetermined target value, which exhibits complicated behavior that cannot be explained only by the content of gypsum in the cement according to the form or the water-soluble alkali content. For this reason, in the technique disclosed in the above-mentioned patent document, there is a problem that in the concrete having a low water cement ratio of 40% or less, a mixture having excellent fluidity and a poor one is mixed. The flow rate of concrete, particularly the change over time of flowability, has not yet reached a level where it can be stably improved.
Report of Fluidity Research Committee, Japan Cement Association (September 2003), pages 135-137 JP 2000-302518 A JP 2004-196624 A Japanese Patent Laid-Open No. 11-302062

  The present invention is a concrete having a low water cement ratio using a polycarboxylic acid-based dispersant, which is stable and excellent in fluidity immediately after mixing with water, regardless of the brand (type) of the dispersant. It is an object to provide a cement composition having a small change in property over time.

The main terms used in this specification have the following meanings.
“Water cement ratio” refers to the mass ratio of water and dispersant to a cement composition, ie, a cement composition containing cement clinker and gypsum. “Low water cement ratio” means a water cement ratio of 40% or less. “Cement paste” refers to a kneaded material containing a cement composition, water, and a polycarboxylic acid-based dispersant, and “concrete” refers to a kneaded material that includes a cement composition, water, and a polycarboxylic acid-based dispersant. Furthermore, it refers to a kneaded product in which fine aggregate and coarse aggregate are added. “Mortar” is a mixture of cement composition, water, and polycarboxylic acid-based dispersant, with fine aggregate, that is, sand added. A kneaded product.
The terms other than the above are used in the meaning of terms generally used in the technical field of concrete, for example, as defined in JIS A0203-1993 “Concrete terms”.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have determined not only the amount of hemihydrate gypsum in the cement composition but also hemihydrate gypsum in the concrete having a low water cement ratio using a polycarboxylic acid-based dispersant. By controlling all of the ratio and the amount of water-soluble alkali within the optimum range, it was found that the fluidity immediately after kneading was excellent and the change in fluidity with time was small, and the present invention was completed.

  Moreover, when manufacturing the said cement composition, the manufacturing method of the cement composition which sprinkles a small amount of water and grind | pulverizes and adjusts the amount of hemihydrate gypsum and the adhering moisture content of a cement composition ground particle was discovered.

  That is, the present invention is a cement composition containing cement clinker and gypsum, wherein the amount of hemihydrate gypsum in the cement composition is 0.2 to 3.5% by mass, and the combination of hemihydrate gypsum and dihydrate gypsum. It is related with the cement composition whose ratio of the hemihydrate gypsum with respect to quantity is 50-95 mass%, and a water-soluble alkali amount is 0.17-0.32 mass%.

In the cement composition of the present invention, the amount of SO ₃ in the cement composition is 1.70 to 3.20% by mass, and the cement composition further contains 7 to 13% by mass of C ₃ A calculated by the Borg formula. It is preferable that the total amount of C ₃ A and C ₄ AF is 15 to 25% by mass, MgO is 0.8 to 1.8% by mass, and F is 0.03 to 0.07% by mass. . The present invention also relates to particles obtained by pulverizing the cement composition of the present invention, wherein the particles further have a moisture content of 0.003 to 1.0% by mass with respect to the cement composition. Preferably there is.

Further, the cement composition of the present invention or a concrete containing particles obtained by pulverizing the cement composition, a polycarboxylic acid-based dispersant, and water, wherein water per 1 m ^{3 of} concrete and blending of the dispersant into the cement composition The amount is 20 to 40% in terms of a water cement ratio, and relates to a concrete containing 0.5 to 3.0 parts by mass of a polycarboxylic acid-based dispersant with respect to 100 parts by mass of the cement composition.

  Further, when pulverizing a cement composition containing a cement clinker and gypsum, 0.1 to 5 parts by mass of water is sprayed on 100 parts by mass of the cement composition, and the amount of hemihydrate gypsum in the cement composition and the cement The present invention relates to a method for producing a cement composition that adjusts the amount of moisture adhering to the pulverized particles of the composition.

In the method of the present invention, the cement clinker has a SO ₃ amount (S) and a total alkali amount (R) of S / R molar ratio.
When S / R <0.7, 0.30 ≦ S ≦ 0.53 (mass%)
When 0.7 ≦ S / R ≦ 1.7
0.43-0.3xS ≦ R ≦ 0.76-0.3xS (mass%)
When 1.7 <S / R 0.27 ≦ R ≦ 0.47 (mass%)
It is preferable to contain in the range.

  According to the cement composition according to the present invention, in a concrete having a water cement ratio of 20 to 40% using a polycarboxylic acid-based dispersant, it is excellent in slump flow (or slump) expression immediately after being mixed with water and dispersed. The additive amount can be reduced. In addition, the slump flow after 60 minutes of mixing with water can maintain 50 to 60% or more of the slump flow immediately after mixing with water, and the change in fluidity with time is remarkably improved.

  Further, according to the cement composition of the present invention, not only concrete but also cement paste and mortar can ensure fluidity equal to or higher than that of the prior art.

  In addition, the cement composition according to the present invention makes it possible to supply low-water cement ratio concrete using a polycarboxylic acid-based dispersant with stable quality and low cost. For this reason, the fluidity | liquidity fall which becomes a problem on construction does not arise in the transport period from a concrete manufacturing factory to a construction site, and shortening of construction time etc. can be aimed at.

  Hereinafter, the present invention will be described in detail.

  The cement composition according to the present invention is a cement composition containing a cement clinker and gypsum, and can be produced using, for example, ordinary Portland cement as a raw material. The cement composition may appropriately contain limestone, blast furnace slag and / or fly ash as other components.

  The amount of hemihydrate gypsum in the cement composition is 0.2 to 3.5% by mass, and the ratio of hemihydrate gypsum to the total amount of dihydrate gypsum and hemihydrate gypsum (hereinafter referred to as “hemihydrate gypsum ratio”). Is 50 to 95% by mass, and the amount of water-soluble alkali is 0.17 to 0.32% by mass.

When the amount of hemihydrate gypsum is 0.2 to 3.5% by mass, it is possible to suppress the hydration of C ₃ A in the very initial stage, avoid quality abnormalities such as “stiffness” and abnormal condensation, Immediately after that, precipitation of dihydrate gypsum crystals can be suppressed, and further, increase in sulfate ion elution amount that inhibits the dispersion effect of polycarboxylic acid-based dispersants can be suppressed, so that the fluidity immediately after mixing of concrete can be kept good. it can. Therefore, since the amount of the polycarboxylic acid-based dispersant added to obtain a predetermined fluidity can be reduced, there is no problem of causing abnormalities in the coagulation properties.

  When the proportion of hemihydrate gypsum is 50% by mass or more, the change over time in the fluidity of the concrete can be reduced. In particular, in concrete having a water cement ratio of 20 to 40%, the slump flow after 60 minutes has passed after mixing can be properly maintained, and the pouring of concrete and the like can be facilitated. On the other hand, when the proportion of hemihydrate gypsum is 95% by mass or less, precipitation of dihydrate gypsum immediately after water contact and fluidity immediately after kneading do not decrease.

  When the water-soluble alkali amount is 0.17% by mass or more, the dispersion effect of the polycarboxylic acid-based dispersant is moderately exhibited and material separation does not occur, which is preferable in terms of durability of the concrete. In addition, it is not necessary to reduce the amount of polycarboxylic acid-based dispersant added to prevent material separation, so that the fluidity retention effect of the dispersant can be ensured, and the change in fluidity with time can be suppressed. Further, when the water-soluble alkali amount is 0.32% by mass or less, it is not necessary to increase the amount of the polycarboxylic acid-based dispersant added to obtain a predetermined fluidity, and there is no possibility of causing abnormalities in the coagulation properties.

The amount of SO ₃ in the cement composition is preferably 1.7 to 3.2% by mass. If the amount of SO ₃ in the cement composition is within this range, the initial strength development will not be reduced, and the long-term strength development will not be reduced.

In order to exhibit the fluidity improvement of the cement composition of the present invention more effectively, the amount of C ₃ A in the cement composition calculated by the Borg formula is 7 to 15% by mass, the amount of C ₃ A and C ₄ AF. The total amount is preferably 15 to 25% by mass.

  Moreover, it is preferable that the cement composition of this invention contains 0.8-1.8 mass% of MgO, and 0.03-0.07 mass% of F. When the amount of MgO and the amount of F are in this range, the formation of an aluminate phase is suppressed, and the fluidity does not decrease. In addition, if the MgO amount is in this range, the strength does not decrease, and if the F amount is in this range, the problem of setting delay does not occur.

  In the present invention, the amount of hemihydrate gypsum and the ratio of hemihydrate gypsum in the cement composition are controlled by the clinker temperature supplied to the mill, or the amount of water sprayed during pulverization of the cement composition and the clinker temperature supplied to the mill. be able to. The clinker temperature supplied to the mill controls the pulverization temperature when the cement composition is pulverized, using the cement temperature at the mill exit as an index. Furthermore, it can also be controlled by adjusting the amount of water brought into the pulverizing mill by the addition amount of gypsum, blast furnace slag, and limestone. For example, in order to increase the amount of hemihydrate gypsum, the clinker temperature is increased and the pulverization temperature is increased. Conversely, in order to reduce the hemihydrate gypsum amount ratio, the clinker temperature is lowered to lower the pulverization temperature and / or the water spray amount is increased to increase the water vapor pressure in the mill.

The amount of water-soluble alkali in the cement composition is controlled by adjusting the SO ₃ amount, Na ₂ O amount and K ₂ O amount in the clinker as a cement raw material to appropriate amounts. That is, FIG. 1 is a diagram showing the relationship between the SO ₃ amount in the clinker, the total alkali amount (Na ₂ O + 0.658K ₂ O amount), and the water-soluble alkali amount obtained by the present inventors. is there. Here, the cement clinker determines the SO ₃ amount (S) and the total alkali amount (R) with respect to the molar ratio of S / R.
When S / R <0.7, 0.30 ≦ S ≦ 0.53 (mass%)
When 0.7 ≦ S / R ≦ 1.7
0.43-0.3xS ≦ R ≦ 0.76-0.3xS (mass%)
When 1.7 <S / R 0.27 ≦ R ≦ 0.47 (mass%)
When the content is within the range, a water-soluble alkali amount of 0.17 to 0.32 mass% within the range of the present invention can be obtained. The SO ₃ amount (S) can be controlled by the type of fuel at the time of firing (for example, the amount of coal, oil coke, and heavy oil used), and the total alkali amount can be controlled by the ratio of the raw materials used for Si and Al sources. In the actual manufacturing process, the SO ₃ amount (S) of the clinker is generally determined by the fuel usage ratio, so after confirming the SO ₃ amount, the clay source material (lime ash, clay, construction generated soil, etc.) The amount of alkali can be adjusted by changing the ratio of use.

The particles obtained by pulverizing the cement composition of the present invention have a moisture content of 0.003 to 1.0% by mass, preferably 0.003 to 0.5% by mass, and particularly preferably 0.01 to 0.1% by mass. Have When the adhering moisture content of the cement composition pulverized particles is 0.003% by mass or more, there is sufficient water to cover the cement composition pulverized particles, and an effect can be exerted for suppressing the hydration of C ₃ A. In addition, the amount of water adhering to the cement composition pulverized particles can be measured from the amount of mass decrease at 20 to 100 ° C. in the mass reduction curve of differential thermogravimetric analysis shown in FIG. It can be carried out by controlling the grinding temperature and humidity in the mill.

In producing the cement composition of the present invention, at the time of pulverizing the cement composition, 0.1 to 5 parts by mass of water is sprayed on 100 parts by mass of the cement composition, and the amount of hemihydrate gypsum and the pulverized particles of the cement composition are dispersed. It is preferable to adjust the amount of moisture adhering to the surface. When the amount of water to be sprayed is 0.1 parts by mass or more, moisture can be attached to the entire cement composition pulverized particles, and the effect of suppressing the hydration of C ₃ A is sufficiently exhibited. When the amount of water to be sprayed is 5 parts by mass or less, weathering of the cement composition and the resulting decrease in strength development can be prevented.

At this time, the cement clinker is capable of combining the SO ₃ amount (S) and the total alkali amount (R) with respect to the molar ratio of S / R.
When S / R <0.7, 0.30 ≦ S ≦ 0.53 (mass%)
When 0.7 ≦ S / R ≦ 1.7
0.43-0.3xS ≦ R ≦ 0.76-0.3xS (mass%)
When 1.7 <S / R 0.27 ≦ R ≦ 0.47 (mass%)
It is preferable to contain in the range.

  As the cement composition pulverizer, a pulverizer such as a tube mill or a vertical mill can be used. Further, the watering device may be any device that can supply a fixed amount, and may be poured into the clinker before the tube mill, or may be poured into gypsum, slag, limestone, or the like. As a method of controlling both the amount of moisture adhering to the cement composition pulverized particles and the amount of hemihydrate gypsum, the pulverization temperature and humidity in the mill by adjusting the watering amount and adjusting the temperature of the clinker supplied to the mill. Can be controlled. Specifically, the amount of water sprayed is in the range of 0.1 to 5 parts by mass with respect to 100 parts by mass of the clinker. The grinding temperature is adjusted by adjusting the temperature of the clinker supplied to the mill using the cement temperature at the outlet of the mill as an index. In addition, by changing the amount of additives such as gypsum, blast furnace slag, limestone and the like, the amount of moisture brought into the pulverizing mill can be adjusted to control.

  In the field of concrete, the polycarboxylic acid-based dispersant in the present invention generally has a carboxylic acid group in the chemical structural formula among chemical admixtures called high-performance AE water reducing agents or high-performance water reducing agents, and has side chains. And a dispersant having a molecular skeleton of a comb-type graft copolymer having a polyoxyethylene chain or the like.

  The concrete of the present invention has a water cement ratio of 20 to 40%, preferably 27 to 35%, and 0.5 to 3.0 parts by mass of a polycarboxylic acid-based dispersant with respect to 100 parts by mass of the cement composition. Preferably it contains 0.8 to 1.9 parts by mass.

  For concrete with a water-cement ratio of less than 20%, it is difficult to obtain a workable fluidity, and the amount of polycarboxylic acid-based dispersant used is extremely increased, which may adversely affect other qualities such as setting and strength. is there. On the other hand, if the water cement ratio exceeds 40%, high strength may not be obtained due to an increase in the unit water amount. Moreover, when the addition amount of the polycarboxylic acid-based dispersant is 0.5 parts by mass or more, sufficient dispersion performance can be exhibited, and when it is 3.0 parts by mass or less, the possibility of adversely affecting the setting and strength is avoided. it can.

  Hereinafter, the present invention will be described in detail by way of examples.

[1. Materials used]
The following materials were used.
(1) Cement composition The normal Portland cement N1-N12 manufactured using the normal Portland cement clinker K1-K10 shown in Table 1-1 was used for the cement. The cement composition uses an actual tube mill pulverized product, and N1, N11, and N12 are samples manufactured by using the same lot of clinker K1 and changing the temperature and watering amount during pulverization. Are all different samples. The watering amount is changed in the range of 0 to 3 parts by mass with respect to 100 parts by mass of the clinker, and the pulverization temperature is changed in the range of 50 to 120 ° C. with the clinker temperature supplied to the mill as an index of the cement temperature at the mill outlet. The cement temperature at the mill outlet was set to 60 to 135 ° C. Thereby, the amount of hemihydrate gypsum, the ratio of hemihydrate gypsum, and the amount of water-soluble alkali in the cement composition were adjusted as shown in Table 1-2.

  Moreover, "20-100 degreeC reduction (mass%) of TG" in Table 1-2 is an parameter | index for evaluating the amount of moisture adhering to the cement composition ground particle surface by watering, and shows in FIG. It is the weight loss (mass%) in the range of 20-100 degreeC at the time of heating up at 10 degreeC / min by differential thermogravimetric analysis (TG-DTA). The measurement method uses TG-DTA6200 (manufactured by Seiko Instruments Inc.) as a differential thermothermal gravimetric analyzer, and puts about 30 mg of the sample into a 30 μL capacity cell (aluminum container) having a 20 μm diameter hole. The temperature was raised from room temperature (20 ° C.) to 200 ° C. at a temperature rate of 5 ° C./min. An aluminum plate (31 mg) was used as a reference. FIG. 1 shows a measurement example. As shown in FIG. 2, the weight loss (ΔG1) from 20 to 100 ° C. was defined as the amount of moisture adhering to the cement composition pulverized particles.

(2) Polycarboxylic acid type dispersant The high performance AE water reducing agents A1 to A7 shown in Table 2 were used as the polycarboxylic acid type dispersant.

(3) Tap water was used as the water used for mixing.
(4) Fine aggregate (sand)
As fine aggregate (sand), standard sand (made by Cement Association) described in JIS R 5201 “Physical test method of cement” is used for mortar, and sea sand (fine sand / Wakamatsu (10%) from Kitakyushu + coarse) for concrete Sand / from Karatsu, Saga Prefecture (90%); coarse grain ratio 2.95) was used.
(5) Coarse aggregate As the coarse aggregate, crushed stone from Miyano, Yamaguchi Prefecture (coarse particle ratio 6.68) was used.

[2. Characterization of cement composition]
(1) Determination of gypsum The amount of hemihydrate gypsum and the amount of dihydrate gypsum were determined by differential thermogravimetric analysis (TG-DTA). Specifically, using a differential thermothermal gravimetric analyzer TG-DTA6200 (manufactured by Seiko Instruments Inc.), about 30 mg of a sample is placed in a cell (made of aluminum) having a hole of 20 μm in diameter and having a capacity of 30 μL. The temperature was raised from room temperature to 200 ° C. at a rate of 5 ° C./min. As shown in FIG. 3, the weight loss of 120 to 160 ° C. accompanying the dehydration of dihydrate gypsum: a mass% and the weight loss of 160 to 220 ° C. due to the dehydration of hemihydrate gypsum: b mass% were measured, and the formula ( The amount of dihydrate gypsum (mass%) and the amount of hemihydrate gypsum (mass%) in the cement composition were calculated using 3) and formula (4). Moreover, the ratio (mass%) of hemihydrate gypsum was computed using Formula (5). An aluminum plate was used as a reference.

Dihydrate gypsum amount (mass%) = weight loss a (mass%) × 172 (molecular weight of dihydrate gypsum) ÷ (1.5 × 18 (molecular weight of H ₂ O)) (3)
Hemihydrate gypsum amount (mass%) = (weight loss b (mass%) − weight loss a (mass%) ÷ 3) × 145 (molecular weight of hemihydrate gypsum) ÷ (0.5 × 18 (molecular weight of H ₂ O)) (4)
Hemihydrate gypsum ratio (mass%) = hemihydrate gypsum amount ÷ (semihydrate gypsum amount + dihydrate gypsum amount) x 100 (5)

(2) Water-soluble alkali amount The water-soluble alkali amount in the cement composition was quantified according to the Cement Association standard test method JCAS I-04 “Analytical method for water-soluble components of cement”.

(3) _CaO of mineral composition in the cement of the chemical components and Borg formula calculation of _{cement, SiO 2, Al 2 O 3} , Fe 2 O 3, MgO, SO 3, Na 2 O, K 2 O content (wt%) Was quantified according to JIS R 5202 “Chemical analysis method of Portland cement”. Further, the F content (mass%) was quantified according to the Cement Association Standard Test Method JCAS I-51 “Method for Quantifying Trace Components in Cement and Cement Raw Materials”. Further, the C ₃ A amount and the C ₄ AF amount calculated by the Borg formula were calculated by the formulas (6) and (7) defined in JIS R 5210 “Portland cement”.

C ₃ A (mass%) = 2.65 × Al ₂ O ₃ (mass%) − 1.69 × Fe ₂ O ₃ (mass%)
(6)
C ₄ AF (mass%) = 3.04 × Fe ₂ O ₃ (mass%) (7)

(4) Blaine specific surface area The Blaine specific surface area (cm ² / g) of the cement composition was measured according to JIS R 5201 “Physical test method of Portland cement”.

[3. Cement paste, mortar and concrete preparation and fluidity evaluation method]
(1) Preparation of cement paste, mortar and concrete Cement paste, mortar and concrete were prepared according to the formulation shown in Table 3. The cement paste was prepared according to the method described in JIS R 5201 “Cement physical test method” using a Hobart mixer and kneaded water in which the cement composition and the polycarboxylic acid dispersant were mixed in advance. The preparation of the mortar was conducted in accordance with the method described in JIS R 5201 “Physical testing method of cement”, and the cement composition and fine aggregate were added using a Hobart mixer, and then a polycarboxylic acid dispersant was mixed in advance. Kneaded water. The concrete was prepared according to JIS A 1138 “How to make concrete in a test room”. Specifically, using a forced biaxial mixer, the cement composition, the fine aggregate, and the coarse aggregate were added, and then water premixed with a polycarboxylic acid-based dispersant was added and kneaded for 90 seconds. The concrete composition was prepared in accordance with the concrete standard specifications [Construction] and the composition shown in Table 3. In addition, “fine aggregate ratio” in Table 3 represents the volume ratio of the fine aggregate amount with respect to the total aggregate amount in the concrete as a percentage, as defined in “Concrete terms” of JIS A 0203. The numerical value.

(2) Fluidity evaluation of cement paste The fluidity of cement paste was evaluated by the paste flow value. The paste flow value was measured immediately after the kneading, according to JASS 15 M-103 “Quality Standard for Self-Leveling Material”. Moreover, after leaving still for 60 minutes, the paste flow value was measured again, and the time-dependent change of fluidity was evaluated by paste flow residual ratio (paste flow after 60 minutes ÷ paste flow immediately after kneading × 100%).

(3) Evaluation of fluidity of mortar The fluidity of mortar was evaluated by the mortar flow value. The mortar flow was measured in accordance with JIS R 5201 “Cement physical test method”. After the completion of mixing, the mixture was stirred 10 times with a spoon, and the mortar was added to the flow cone to measure the mortar flow value. Moreover, after leaving still for 60 minutes, the mortar flow value was measured again, and the temporal change of fluidity was evaluated by the residual rate of mortar flow (mortar flow after 60 minutes ÷ mortar flow immediately after mixing × 100%).

(4) Fluidity evaluation of concrete The fluidity of concrete was evaluated by a slump flow value or a dispersant addition amount for obtaining a predetermined slump flow (600 ± 50 mm). After completion of the mixing of the concrete, the mixture was allowed to stand for 5 minutes, and the slump flow was measured according to JIS A 1150 “Concrete slump flow test method”. Moreover, after leaving still for 60 minutes, slump flow was measured again and the temporal change of fluidity | liquidity was evaluated by the slump flow residual rate (slump flow after 60 minutes ÷ slump flow after 5 minutes of mixing × 100%).

[4. Evaluation results of fluidity]
The fluidity of cement paste, mortar, and concrete having a water cement ratio of 35% blended with the polycarboxylic acid dispersant A1 was compared. Here, the addition amount of the polycarboxylic acid-based dispersant was changed so that a slump flow immediately after mixing the concrete was 600 ± 50 mm in each cement type. The results are shown in Table 4.

  In cement paste and mortar, the flow value after 60 minutes hardly changes compared with the flow value immediately after mixing, whereas in concrete, the flow value after 60 minutes is compared with the flow value immediately after mixing. May be significantly smaller. Moreover, despite the adjustment of the amount of polycarboxylic acid-based dispersant so that the slump flow immediately after mixing the concrete is 600 ± 50 mm regardless of the cement type, the residual rate of the slump flow value is It fluctuates greatly with 52 to 103%. Such a large variation in the residual rate is a phenomenon that is not observed in cement pace and mortar using the same cement composition.

  From the results of Table 4, cement paste or mortar with excellent fluidity does not mean concrete with excellent fluidity, but concrete with excellent fluidity is fluidity of cement paste or mortar with excellent fluidity. Can be said to mean.

  Table 5 shows the test results of concrete using the polycarboxylic acid dispersant A4 or A5 and changing the water-cement ratio. Here, the test was performed by changing the amount of the polycarboxylic acid-based dispersant added so that the slump flow immediately after mixing was 600 ± 50 mm.

  When the water-cement ratio is small, the amount of polycarboxylic acid-based dispersant added to obtain a slump flow of 600 ± 50 mm immediately after mixing varies greatly depending on the cement type. That is, at a water cement ratio of 40%, the amount of polycarboxylic acid-based dispersant added is almost constant at 0.9 to 1.1 parts by mass regardless of the type of cement in any dispersant. However, in the case of the dispersant A4, when the water cement ratio is 27%, the maximum-minimum difference of the dispersant addition amount corresponding to the cement type is 1.1 parts by mass, and when the water cement ratio is 35%, the maximum-minimum difference is 0. 9 parts by mass (Test Nos. 7 and 9). In the case of the dispersant A5, the maximum-minimum difference is 1.4 parts by mass at a water cement ratio of 27%, and the maximum-minimum difference is 1.3 parts by mass at a water cement ratio of 35% (Test No. 14). 15). Therefore, the lower the water-cement ratio, the greater the amount of dispersant added to obtain a predetermined slump flow between cement compositions. In addition, as the water-cement ratio decreases, the change in slump flow over time itself increases (remaining rate decreases).

  In addition, the cement types N1, N2, and N4, which are excellent in fluidity in concrete having a low water cement ratio (27%, 35%), are excellent in fluidity even in concrete having a higher water cement ratio (40%). Specifically, the cement types N1, N2, and N4 have a water cement ratio of 27%, and when the dispersant A4 is used, the residual rate is 51 to 52% (Test Nos. 6, 7, and 8). When A5 is used, the residual ratio is 65 to 93% (Test Nos. 11, 12, and 13), and the fluidity is good regardless of the type of the dispersant. Even at a water cement ratio of 35 and 40%, the fluidity of these cement compositions is good.

  On the other hand, the cement type N7 has a water cement ratio of 27%, and when the dispersant A4 is used, the residual rate is 51% (test No. 9), which is comparable to the cement types N1, N2, and N4, but the dispersant A5 Is used, the residual rate is 52% (Test Nos. 11, 12, and 13), which is lower than the cement types N1, N2, and N4. In addition, as shown in Table 4, the cement type N9 had a very high residual ratio when 1.5% of the dispersant A1 was added at a water cement ratio of 35% (test No. 6). In the case of 27%, in the case of Dispersant A4, the addition amount must be 1.9% (Test No. 10), and in the case of Dispersant A5, the addition amount must be 2.1% (Test No. 15). Compared with the types N1, N2, and N4, a large amount of dispersant must be added. As a result, a setting delay occurs and there is a problem in construction.

  Furthermore, in the concrete of low water cement ratio, the result of having evaluated the fluidity | liquidity of the concrete using the cement composition which has various characteristics using various polycarboxylic acid type-dispersants is shown in Table 6 and Table 7. . Table 6 shows the test results of concrete with a water cement ratio of 35% and Table 7 with a water cement ratio of 27%. Here, the amount of the dispersant added is 1.0 part by mass (constant), and the fluidity judgment immediately after kneading is “◯” for slump flow 600 ± 50 mm immediately after kneading. The residual rate of slump flow was changed to 50% or more when the water cement ratio was 27%, and 60% or more when the water cement ratio was 35%. Other than that, it was shown as a judgment “x”. In addition, the overall judgment was that the cement composition immediately after kneading and the residual ratio was judged as “◯” regardless of which dispersant was used, was judged as “総 合”, and otherwise “x”.

  From Table 6, in the concrete having a water cement ratio of 35%, the cement composition of the present invention (N1-4, 6, 11, 12) is excellent in fluidity immediately after mixing and slump flow after 60 minutes. The residual ratio of the water is 60% or more, and the change with time of the fluidity is also small (Test Nos. 16 to 35, 41 to 45, 68, and 69).

  On the other hand, the cement composition (N5) in which the amount of hemihydrate gypsum exceeds 3.5% by mass has a slump flow immediately after mixing of 310 and 320 mm when using A6 and A7 as the polycarboxylic acid-based dispersant. This was far below the target value of 600 ± 50 mm (Test Nos. 39 and 40). This is because the amount of hemihydrate gypsum increases the concentration of sulfate ions in the liquid phase and decreases the dispersion performance of the polycarboxylic acid admixture, and the precipitation of dihydrate gypsum This is because the particles are bonded and aggregated.

  The cement composition (N7) in which the water-soluble alkali amount is reduced to less than 0.17% by mass has a target slump flow of 670 to 685 mm immediately after mixing, regardless of which polycarboxylic acid dispersant is used. Exceeding 600 ± 50 mm resulted in material separation (Test No. 46, 48-51). In order to prevent material separation, the amount of polycarboxylic acid-based dispersant added was reduced to 0.7% by mass (Test No. 47). However, although material separation no longer occurred, the temporal change in fluidity increased. The residual slump flow rate after 60 minutes was as small as 52%.

  The cement composition (N8, 9) having a water-soluble alkali amount of more than 0.32% has a slump flow immediately after kneading of 474 to 533 mm and a target value of 600 ± regardless of which polycarboxylic acid dispersant is used. It was less than 50 mm (test No. 52, 54, 57, 59). In addition, in order to obtain the target slump flow, the amount of polycarboxylic acid-based dispersant added was increased to 2.0% by mass (Test No. 53), but a delay in setting occurred, and the concrete was not applied. I found out there was a problem.

  The cement composition (N10) having a hemihydrate gypsum ratio of 50% by mass or less has a long-term change in fluidity when A2, A3, and A6 are used as the polycarboxylic acid dispersant (Test Nos. 64 to 64). 66). In addition, when the polycarboxylic acid dispersant is A1 or A7, the fluidity immediately after mixing is poor (Test Nos. 63 and 67).

  From Table 7, the cement composition (N1, 2, 4) of the present invention is excellent in fluidity immediately after kneading, and the residual rate of slump flow after 60 minutes, even in concrete with a water cement ratio of 27%. Is 60% or more, and the change with time of fluidity is also small (Test Nos. 70 to 72, 75 to 77).

  As described above, in concrete having a low water cement ratio, the cement composition in which the amount of hemihydrate gypsum, the proportion of hemihydrate gypsum and the amount of water-soluble alkali according to the present invention are adjusted to the optimum ranges is a polycarboxylic acid dispersant. However, even if the amount of dispersant added is small, material separation does not occur and the coagulation properties are not affected. For this reason, it is excellent in the fluidity | liquidity immediately after kneading | mixing, and it becomes possible to make small the time-dependent change of fluidity | liquidity.

  Moreover, the cement composition (N11, 12) pulverized by spraying 0.2 part by mass or 3 parts by mass of water at the time of manufacturing the cement composition is more than the cement composition (N1) pulverized without spraying water. The fluidity is more excellent (Test No. 16, 68, 69). Therefore, a more preferable effect can be obtained by adding water during the production of the cement composition.

SO ₃ content in the clinker, the total amount of alkali _{(Na 2} O + 0.658K 2 O amount) is a diagram showing the relationship between the water-soluble alkali content. It is a figure which shows the example which measured the adhesion moisture content (weight reduction in 20-100 degreeC) of a cement composition particle | grain using differential thermogravimetric analysis (TG-DTA). It is a figure which shows the example which measured the dehydration amount of the dihydrate gypsum and hemihydrate gypsum in a cement composition using differential thermogravimetric analysis (TG-DTA).

Claims (7)

  A cement composition containing a cement clinker and gypsum, wherein the amount of hemihydrate gypsum in the cement composition is 0.2 to 3.5% by mass, and the amount of hemihydrate gypsum relative to the total amount of hemihydrate gypsum and dihydrate gypsum The cement composition is characterized by having a ratio of 50 to 95% by mass and a water-soluble alkali amount of 0.17 to 0.32% by mass. The cement composition according to claim 1, wherein the amount of SO ₃ in the cement composition is 1.70 to 3.20 mass%. The cement composition contains 7 to 13% by mass of B ₃ calculated C3 A, 15 to 25% by mass of C ₃ A and C ₄ AF, and 0.8 to 1.8 of MgO. The cement composition according to claim 1 or 2, comprising 0.03% to 0.07% by mass of F and 0.03 to 0.07% by mass of F.   A particle obtained by pulverizing the cement composition according to any one of claims 1 to 3, wherein the particle has a moisture content of 0.003 to 1.0 mass% with respect to the cement composition. Composition ground particles. A cement comprising the cement composition according to any one of claims 1 to 3 or the cement composition ground particles according to claim 4, a polycarboxylic acid-based dispersant, and water, wherein the concrete per 1 m ^{3 of the} concrete The blending amount of water and the dispersant with respect to the cement composition is 20 to 40% in terms of the water cement ratio, and 0.5 to 3.0 parts by mass of the polycarboxylic acid-based dispersant is included with respect to 100 parts by mass of the cement composition. concrete.   When a cement composition containing cement clinker and gypsum is pulverized, 0.1 to 5 parts by mass of water is sprayed on 100 parts by mass of the cement composition, and the amount of hemihydrate gypsum in the cement composition and the cement composition A method for producing a cement composition, comprising adjusting the amount of moisture adhering to the pulverized particles. The cement clinker determines the SO ₃ amount (S) and the total alkali amount (R) with respect to the molar ratio of S / R.
When S / R <0.7, 0.30 ≦ S ≦ 0.53 (mass%)
When 0.7 ≦ S / R ≦ 1.7
0.43-0.3xS ≦ R ≦ 0.76-0.3xS (mass%)
When 1.7 <S / R 0.27 ≦ R ≦ 0.47 (mass%)
The method according to claim 6, which is contained in the range of

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