JP6447291B2 - Method for determining the composition of fresh concrete - Google Patents

Description

  The present invention relates to a method for determining the blending of fresh concrete.

Conventionally, part of Portland cement, which emits a large amount of CO ₂ during production as low-carbon or resource-saving concrete, is a blast furnace slag fine powder 4000 (hereinafter referred to as “JIS”) defined in JIS A 6206, which is an industrial byproduct. Blast furnace slag fine powder 4000 defined in A 6206 is referred to as “blast furnace slag fine powder”) and fly ash type II defined in JIS A 6201 (hereinafter referred to as “fly ash II defined in JIS A 6201”). Concrete in which “seed” is referred to as “fly ash”) is known (see, for example, Patent Document 1).

  However, concrete using these industrial wastes as raw materials can reduce carbon dioxide emitted during production, but also has problems such as low compressive strength and increased neutralization rate coefficient.

JP2013-203635A

  There is a need for a suitable blending method of concrete using industrial waste as a raw material.

  The main object of the present invention is to provide a suitable blending method of fresh concrete using industrial waste as a raw material.

The blending determination method for fresh concrete according to the present invention relates to a blending determination method for fresh concrete containing ordinary Portland cement, blast furnace slag fine powder, and fly ash. In the method for determining the composition of fresh concrete according to the present invention, the point X (N, BS, FA) is represented in a triangular composition diagram having normal Portland cement (N), blast furnace slag fine powder (BS) and fly ash (FA) as vertices = (39.58, 51.05, 9.37), point Y (N, BS, FA) = (3 5.8 9, 39.11, 25), point Z (N, BS, FA) = ( 42.49, 32.51, 25) The composition ratios of ordinary Portland cement, ground granulated blast furnace slag and fly ash are determined. By doing so, the neutralization rate coefficient, the apparent diffusion coefficient of chloride ions, and the temperature cracking index when the 28-day compressive strength is 45 N / mm ² can each determine a suitable blend of fresh concrete. . Specifically, according to the method for determining the composition of fresh concrete according to the present invention, when the 28-day compressive strength is 45 N / mm ² , the neutralization rate coefficient is 4.9 mm / week ^(1/2) or less. Yes, the composition of fresh concrete having an apparent diffusion coefficient of chloride ions of 0.5 or less and a temperature cracking index of 0.9 or more can be determined.

  “28-day compressive strength” means the compressive strength when the age of cement is 28 days.

  ADVANTAGE OF THE INVENTION According to this invention, the suitable compounding method of the fresh concrete which uses industrial waste as a raw material can be provided.

The mass proportions of ordinary Portland cement (N), ground granulated blast furnace slag (BS) and fly ash (FA) are (N, BS, FA) = (100, 0, 0) and (N, BS, FA) = ( 50, 50, 0), (N, BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) = (35, 40, 25) and (N, BS, FA) = (15, 60, 25) are graphs showing the relationship between the neutralization rate coefficient and the compression strength. It is the graph which showed the relationship between the neutralization rate coefficient in case compressive strength is 45 N / mm < ² >, and the mass ratio of normal Portland cement. It is a triangular composition diagram showing a range in which the neutralization rate coefficient is 4.9 mm / ^1/2 when the compressive strength is 45 N / mm ² . The mass proportions of ordinary Portland cement, ground granulated blast furnace slag, and fly ash are (N, BS, FA) = (100, 0, 0), (N, BS, FA) = (50, 50, 0), (N , BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) = (35, 40, 25), (N, BS , FA) = (15, 60, 25) is a graph showing the relationship between the apparent diffusion coefficient of chloride ions and the water binder ratio. The mass proportions of ordinary Portland cement, ground granulated blast furnace slag, and fly ash are (N, BS, FA) = (100, 0, 0), (N, BS, FA) = (50, 50, 0), ( N, BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) = (35, 40, 25), (N, It is the graph which showed the relationship between the compressive strength at the time of setting (BS, FA) = (15,60,25) and binder water ratio. Compressive strength is a graph showing the relation between the mass ratio of the ordinary Portland cement and apparent diffusion coefficient of chloride ions during 45N / mm ^2. It is a triangular composition diagram showing a range in which the apparent diffusion coefficient of chloride ions when the compressive strength is 45 N / mm ² is 0.5 or less. The mass proportions of ordinary Portland cement, ground granulated blast furnace slag, and fly ash are (N, BS, FA) = (100, 0, 0), (N, BS, FA) = (50, 50, 0), (N , BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) = (50, 25, 25), (N, BS , FA) = (15, 60, 25) is a graph showing the relationship between the compressive strength and the binder water ratio. The mass proportions of ordinary Portland cement, ground granulated blast furnace slag, and fly ash are (N, BS, FA) = (100, 0, 0), (N, BS, FA) = (50, 50, 0), (N , BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) = (50, 25, 25), (N, BS , FA) = (15, 60, 25) is a graph showing the relationship between the temperature stress crack index and the mass ratio of ordinary Portland cement. The mass proportions of ordinary Portland cement, ground granulated blast furnace slag, and fly ash are (N, BS, FA) = (100, 0, 0), (N, BS, FA) = (50, 50, 0), (N , BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) = (50, 25, 25), (N, BS , FA) = (15, 60, 25) is a graph showing the relationship between the temperature stress crack index and the mass ratio of blast furnace slag fine powder. It is a triangular composition diagram showing a range in which the temperature stress crack index when the compressive strength is 45 N / mm ² is 0.9 or more. In compression strength 45N / mm ^2, neutralization rate coefficient is 4.9 mm / week ^1/2 or less, the temperature stress cracking index is 0.90 or more, a triangular composition diagram showing a range of salt diffusion coefficient is 0.5 or less It is.

  In the present embodiment, a method for determining the composition of fresh concrete containing ordinary Portland cement, blast furnace slag fine powder, and fly ash will be described. Specifically, in this embodiment, a blending determination method of fresh concrete containing ordinary Portland cement, blast furnace slag fine powder, fly ash, water, fine aggregate, coarse aggregate, and a water reducing agent. explain.

  Blast furnace slag fine powder is a kind of admixture, and is a powder produced by pulverizing blast furnace slag produced when pig iron is produced in a blast furnace after being rapidly cooled with water. Blast furnace slag fine powder is added to cement as an admixture. Blast furnace slag fine powder has a property (latent hydraulic property) that causes a hydration reaction when stimulated by calcium hydroxide, alkali salts, gypsum, etc. generated by a hydration reaction of cement.

  Fly ash is ash generated at the time of combustion in a thermal power plant (large boiler) using coal as fuel, and is a spherical fine particle having a level that is blown up together with combustion gas.

  A water reducing agent is an admixture that imparts a negative charge to the surface of cement particles and disperses the particles to increase fluidity. As the water reducing agent, for example, an AE water reducing agent, a high performance water reducing agent, a high performance AE water reducing agent, or the like can be used. Of these, AE water reducing agents and high performance AE water reducing agents are preferably used. These water reducing agents are water reducing agents having a function as an AE agent. Here, the AE agent refers to a surfactant mixed to generate air bubbles in the concrete (air entrainment) for the purpose of improving work efficiency and increasing freezing / dissolution resistance.

  When a high-performance AE water reducing agent is used as the water reducing agent, the workability when concrete is mixed is improved, and the unit water volume can be greatly reduced as compared with the AE agent and the AE water reducing agent. Moreover, since concrete with a smaller water binder ratio can be obtained easily, durability of a concrete hardening body can be improved.

  The “high-performance AE water reducing agent” refers to an admixture that has air entrainment properties and has higher water reduction performance and better slump retention function than the AE agent and the AE water reducing agent.

In the method for determining the composition of fresh concrete according to the present embodiment, in the triangular composition diagram having normal Portland cement (N), blast furnace slag fine powder (BS) and fly ash (FA) as vertices, a point X (N, BS, FA ) = (39.58, 51.05, 9.37), point Y (N, BS, FA) = (3 5.8 9, 39.11, 25), point Z (N, BS, FA) = Within the range surrounded by (42.49, 32.51, 25), the respective composition ratios of ordinary Portland cement, ground granulated blast furnace slag and fly ash are determined. By doing so, the neutralization rate coefficient, the apparent diffusion coefficient of chloride ions, and the temperature cracking index when the 28-day compressive strength is 45 N / mm ² can each determine a suitable blend of fresh concrete. . Specifically, according to the blending determination method according to the present embodiment, when the 28-day compressive strength is 45 N / mm ² , the neutralization rate coefficient is 4.9 mm / week ^(1/2) or less, The composition of fresh concrete having an apparent diffusion coefficient of chloride ions of 0.5 or less and a temperature cracking index of 0.9 or more can be determined.

(Experimental example)
Hereinafter, the present invention will be described in more detail on the basis of specific experimental examples. However, the present invention is not limited to the following experimental examples, and may be appropriately modified and implemented without departing from the scope of the present invention. Is possible.

(Manufacture of fresh concrete)
Mix the binder (ordinary Portland cement, blast furnace slag fine powder, fly ash), water, fine aggregate, coarse aggregate and admixture (high performance AE water reducing agent) with the composition shown in Table 1 below. Manufactured. Specifically, when the water binder ratio is 40% or more, the binder, fine aggregate, and coarse aggregate are kneaded and mixed for 15 seconds, and then water containing an admixture is added. The tube was kneaded for 2 seconds to 90 seconds. If the water binder ratio is less than 40%, the binder and fine aggregate are kneaded and mixed, then water containing an admixture is added, the mortar is kneaded for 60 seconds, and then coarse aggregate is added. Then, the mixture was further kneaded for 60 seconds. Then, after leaving still for 5 minutes, fresh concrete was manufactured by kneading for 30 seconds.

  The following materials were used.

Ordinary Portland cement (N) (Ube Industries, Ltd., density 3.16 g / cm ³ )
Blast Furnace Slag Fine Powder (BS) (Chiba Riverment, Brain Value 4420 cm ² / g Fly Ash (FA) (J-Peck, Brain Value 3950 cm ² / g)
Fine aggregate (mixed sand): A mixture of mountain sand and crushed limestone at a mass ratio of 20 to 80 (surface dry density: 2.62 g / cm ³ , water absorption: 0.5%)
Coarse aggregate: Limestone aggregate (surface dry density: 2.69 g / cm ³ , water absorption: 1.75%)
Chemical admixture: High-performance AE water reducing agent (SEICAMENT 1100NT: manufactured by Nihon Sika Corporation)
Water: tap water

  In Table 1, “W / B” indicates a binder water ratio.

(Fresh concrete test)
For each fresh concrete produced as described above, the compressive strength, accelerated neutralization rate coefficient, and apparent diffusion coefficient of chloride ions (salt diffusion coefficient) were determined by the following methods. The results are shown in Table 2.

  Compressive strength: Measured according to JIS A 1108 “Method for testing compressive strength of concrete”.

  Accelerated neutralization rate coefficient: Measured according to JIS A 1153 “Promoted Neutralization Test Method for Concrete”.

  Salinity diffusion coefficient: It was carried out according to the Japan Society of Civil Engineers JSCE-G 572 "Test method for apparent diffusion coefficient of chloride ions in concrete by immersion".

  As for the temperature crack index, a three-dimensional finite element using a thermal stress analysis software (Computational Mechanics Research Center: ASTEM-MACS) was conducted using an adiabatic adiabatic temperature rise measuring device. It was obtained by analyzing by the method.

The following calculations were performed based on the results shown in Table 2.

[Accelerated neutralization rate coefficient]
FIG. 1 shows the mass proportions of ordinary Portland cement (N), blast furnace slag fine powder (BS), and fly ash (FA) (N, BS, FA) = (100, 0, 0), (N, BS, FA) = (50, 50, 0), (N, BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) It is the graph which showed the relationship between the neutralization speed coefficient and compression strength at the time of setting == (35,40,25), (N, BS, FA) = (15,60,25). The relation between the neutralization rate coefficient and the compressive strength was logarithmically approximated by the method of least squares, and the following relational expressions (1) to (6) were derived.

(N, BS, FA) = (100, 0, 0)
ap = −6.16 Log (Fr) +25.9 (1)
(N, BS, FA) = (50, 50, 0)
ap = −5.39 Log (Fr) +24.9 (2)
(N, BS, FA) = (15, 85, 0)
ap = −8.54 Log (Fr) +39.0 (3)
(N, BS, FA) = (75, 0, 25)
ap = −7.01 Log (Fr) +29.8 (4)
(N, BS, FA) = (35, 40, 25)
ap = −7.45 Log (Fr) +33.4 (5)
(N, BS, FA) = (15, 60, 25)
ap = −7.86 Log (Fr) +36.0 (6)
here,
ap: Neutralization rate coefficient (mm ² weeks ^1/2 )
Fr: Compressive strength (N / mm ² )
It is.

The neutralization rate coefficient when the compressive strength was 45 N / mm ² was obtained from the equations (1) to (6).

FIG. 2 is a graph showing the relationship between the neutralization rate coefficient when the compressive strength is 45 N / mm ² and the mass ratio of ordinary Portland cement. Exponential approximation was performed by the method of least squares, and the following relational expression was derived.

When the mass ratio of fly ash is 0%:
ap = 7.760e−0.011 ^Nm (7)
When fly ash mass ratio is 25%:
ap = 7.272e−0.011 ^Nm (8)
here,
Nm: Mass ratio of ordinary Portland cement.

According to the Architectural Institute of Japan “Guidelines for Design and Construction of Highly Durable Reinforced Concrete Structure (draft) / Explanation”, the neutralization depth is 25 mm or less after 26 weeks of neutralization. Since it becomes 4.9 mm / week ^1/2 , the mass ratio of ordinary Portland cement when the neutralization rate coefficient is 4.9 mm / week ^1/2 or less is obtained from the equations (7) to (8), respectively. It was. The results are shown in FIG.

In FIG. 3, the point A is (N, BS, FA) = (100, 0, 0). Point B is (N, BS, FA) = (41.80, 58.20, 0) Point C is (N, BS, FA) = (35.89, 39.11, 25). Point D is (N, BS, FA) = (75, 0, 25). Within the range surrounded by these points A, B, C and D, the neutralization rate coefficient is 4.9 mm / ^1/2 .

[Chloride ion diffusion coefficient]
FIG. 4 shows the mass proportions of ordinary Portland cement, ground granulated blast furnace slag, and fly ash (N, BS, FA) = (100, 0, 0) and (N, BS, FA) = (50, 50, 0), respectively. ), (N, BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) = (35, 40, 25), It is the graph which showed the relationship between the apparent diffusion coefficient of chloride ion at the time of (N, BS, FA) = (15, 60, 25), and a water binder ratio. The relation between the apparent diffusion coefficient of chloride ions and the water binder ratio was exponentially approximated by the method of least squares, and the following relational expression was derived.

(N, BS, FA) = (100, 0, 0)
D _cl = 0.0245e 0.0983 ^{W / B} (9)
(N, BS, FA) = (50, 50, 0)
D _cl = 0.1122e 0.0309 ^{W / B} (10)
(N, BS, FA) = (15, 85, 0)
D _cl = 0.0512e 0.0400 ^{W / B} (11)
(N, BS, FA) = (75, 0, 25)
D _cl = 0.0381e 0.0672 ^{W / B} (12)
(N, BS, FA) = (35, 40, 25)
D _cl = 0.0562e 0.0430 ^{W / B} (13)
(N, BS, FA) = (15, 60, 25)
D _cl = 0.0026e 0.1129 ^{W / B} (14)
here,
D _cl : Apparent diffusion coefficient W / B: Water binder ratio (%)
It is.

  FIG. 5 shows the mass ratios of ordinary Portland cement, ground granulated blast furnace slag and fly ash, (N, BS, FA) = (100, 0, 0), (N, BS, FA) = (50, 50, 0), (N, BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) = (35, 40, 25) , (N, BS, FA) = (15, 60, 25) is a graph showing the relationship between the compressive strength and the binder water ratio. An equation obtained by linear regression of the relationship between the compressive strength and the binder water ratio is shown below.

(N, BS, FA) = (100, 0,)
Fr = 31.99B / W-22.6 (15)
(N, BS, FA) = (50, 50, 0)
Fr = 28.74B / W-17.3 (16)
(N, BS, FA) = (15, 85, 0)
Fr = 18.02B / W-12.3 (17)
(N, BS, FA) = (75, 0, 25)
Fr = 26.85B / W-20.8 (18)
(N, BS, FA) = (35, 40, 25)
Fr = 24.59B / W-18.7 (19)
(N, BS, FA) = (15, 60, 25)
Fr = 19.54B / W-20.9 (20)
here,
Fr: Compressive strength (N / mm ² )
B / W: Binder water ratio.

From the formulas (9) to (20), the apparent diffusion coefficient of chloride ions when the compressive strength was 45 N / mm ² was determined. FIG. 6 is a graph showing the relationship between the apparent diffusion coefficient of chloride ions and the mass ratio of ordinary Portland cement when the compressive strength is 45 N / mm ² . Exponential approximation was performed by the method of least squares, and the following relational expression was derived.

When the mass ratio of fly ash is 0%:
D _cl = 0.1063e ^0.0315Nm (21)
When fly ash mass ratio is 25%:
D _cl = 0.0625e 0.0319 ^Nm (22)
here,
D _cl : Apparent diffusion coefficient Nm: Mass ratio of ordinary Portland cement.

  The mass ratio of ordinary Portland cement when the apparent diffusion coefficient of chloride ions was 0.5 or less was determined from the equations (21) to (22). From these values, the proportions of ordinary Portland cement, blast furnace slag fine powder, and fly ash when the apparent diffusion coefficient of chloride ions was 0.5 or less were determined. The results are shown in FIG. In FIG. 7, the point E is (N, BS, FA) = (49.15, 50.85, 0). The point F is (N, BS, FA) = (15, 85, 0). The point G is (N, BS, FA) = (15, 60, 25). Point H is (N, BS, FA) = (65.19, 9.81, 25).

[Temperature stress crack index]
FIG. 8 shows the mass ratios of ordinary Portland cement, ground granulated blast furnace slag, and fly ash (N, BS, FA) = (100, 0, 0) and (N, BS, FA) = (50, 50, 0), respectively. ), (N, BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) = (50, 25, 25), It is the graph which showed the relationship between the compression strength at the time of (N, BS, FA) = (15, 60, 25) and binder water ratio. An equation obtained by linear regression of the relationship between the compressive strength and the binder water ratio is shown below.

(N, BS, FA) = (100, 0,)
Fr = 31.99B / W-22.6 (23)
(N, BS, FA) = (50, 50, 0)
Fr = 28.74B / W-17.3 (24)
(N, BS, FA) = (15, 85, 0)
Fr = 18.02B / W-12.3 (25)
(N, BS, FA) = (75, 0, 25)
Fr = 26.85B / W-20.8 (26)
(N, BS, FA) = (50, 25, 25)
Fr = 26.72B / W-18.9 (27)
(N, BS, FA) = (15, 60, 25)
Fr = 19.54B / W-20.9 (28)
here,
Fr: Compressive strength (N / mm ² )
B / W: Binder water ratio.

A water binder ratio is obtained from the equations (23) to (28) so that the compressive strength is 45 N / mm ² , an adiabatic temperature rise test and a temperature stress analysis are performed at the obtained water binder ratio, and a temperature stress crack is generated. The index was determined. The results are shown in Table 1.

  FIG. 9 shows the mass ratios of ordinary Portland cement, ground granulated blast furnace slag, and fly ash (N, BS, FA) = (100, 0, 0) and (N, BS, FA) = (50, 50, 0), respectively. ), (N, BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) = (50, 25, 25), It is the graph which showed the relationship between the temperature stress crack index at the time of (N, BS, FA) = (15, 60, 25) and the mass ratio of normal Portland cement. FIG. 10 shows the mass ratios of ordinary Portland cement, ground granulated blast furnace slag, and fly ash (N, BS, FA) = (100, 0, 0) and (N, BS, FA) = (50, 50, 0), respectively. ), (N, BS, FA) = (15, 85, 0), (N, BS, FA) = (75, 0, 25), (N, BS, FA) = (50, 25, 25), It is the graph which showed the relationship between the temperature stress crack index at the time of (N, BS, FA) = (15, 60, 25), the mass ratio of normal Portland cement, and the mass ratio of blast furnace slag fine powder. An equation that approximates the relationship between the temperature stress crack index and the mass ratio of the ground granulated blast furnace slag by first and second order polynomials is shown below.

When the mass ratio of blast furnace slag fine powder is 0%:
σ _t = −5.20E-3Nm + 1.31 (29)
When the mass ratio of fly ash is 0%:
σ _t = 1.25E-4Nm ² -1.90E-2Nm + 1.44 (30)
When fly ash mass ratio is 25%:
σ _t = 1.50E-4Nm ² -1.72E-2Nm + 1.36 (31)
When the mass proportion of ordinary Portland cement is 50%:
σ _t = −3.20E-3BSm + 0.96 (32)
When the mass proportion of ordinary Portland cement is 15%:
σ _t = 1.60E-3BSm + 1.04 (33)
here,
Nm: Mass ratio of ordinary Portland cement BSm: Mass ratio of blast furnace slag fine powder.

  The mass proportion of ordinary Portland cement when the temperature stress cracking index is 0.9 or more was obtained from Equation (29) to Equation (31), and the mass proportion of blast furnace slag fine powder was obtained from Equation (32) to Equation (33), respectively. . From these values, the proportions of ordinary Portland cement, blast furnace slag fine powder and fly ash when the temperature stress crack index was 0.9 or more were determined. The results are shown in FIG. Point H is (N, BS, FA) = (37.84, 62.16, 0). Point I is (N, BS, FA) = (15, 85, 0). The point J is (N, BS, FA) = (15, 60, 25). The point K is (N, BS, FA) = (42.49, 32.51, 25). The point L is (N, BS, FA) = (78.85, 0, 21.15). The point M is (N, BS, FA) = (72.18, 2.82, 25). The point N is (N, BS, FA) = (75, 0, 25). In addition, the range where the mass ratio of fly ash exceeds 25% was excluded.

These results in compression strength 45N / mm ^2, neutralization rate coefficient is 4.9 mm / week ^1/2 or less, the temperature stress cracking index is 0.90 or more, all the salt diffusion coefficient is 0.5 or less It can be seen that the range satisfying the condition is within the range surrounded by the points X, Y and Z in FIG. Point X (N, BS, FA) = (39.58, 51.05, 9.37), Point Y (N, BS, FA) = (3 5.8 9, 39.11, 25), Point Z (N, BS, FA) = (42.49, 32.51, 25).

Claims (2)

A method for determining the composition of fresh concrete containing ordinary Portland cement, blast furnace slag fine powder, and fly ash,
In a triangular composition diagram having normal Portland cement (N), blast furnace slag fine powder (BS) and fly ash (FA) as vertices, point X (N, BS, FA) = (39.58, 51.05, 9. 37), point Y (N, BS, FA) = (3 5.8 9, 39.11, 25), point Z (N, BS, FA) = (42.49, 32.51, 25) Within the specified range, and
When the 28-day compressive strength is 45 N / mm ² , the neutralization rate coefficient is 4.9 mm / week ^(1/2) or less, the apparent diffusion coefficient of chloride ions is 0.5 or less, and the temperature A method for determining the composition of fresh concrete, in which the composition ratios of ordinary Portland cement, ground granulated blast furnace slag and fly ash are determined so that the crack index is 0.9 or more . Based on the neutralization rate coefficient when the 28-day compressive strength is 45 N / mm ² , the apparent diffusion coefficient of chloride ions and the temperature cracking index, the composition ratios of ordinary Portland cement, blast furnace slag fine powder and fly ash are The method for determining the composition of fresh concrete according to claim 1, wherein the determination is performed.