JP4971273B2 - Method for estimating the unit water volume of concrete using an air meter - Google Patents

Description

  The present invention relates to a method for estimating a unit water amount of concrete using an air meter, which can improve estimation accuracy.

  The estimation of the unit water amount of concrete or the like is characterized by how to obtain the difference from the blended planned water amount caused by the amount of water contained in the aggregate. As a representative method of the unit water amount estimation method, a high-frequency heating method or a method using an air meter is known. The high-frequency heating method heats and removes the moisture contained in the aggregate, so that the estimation accuracy can be improved, but it takes time and the operation is troublesome. On the other hand, in the method using an air meter, since the moisture in the aggregate is not processed, it does not take time and can be carried out immediately and easily.

The method using an air meter here is a so-called “unit water amount estimation manual by the air meter method (Public Works Research Institute method)” (see Non-Patent Document 1). The Civil Engineering Research Institute method uses an air meter, and estimates the unit water volume by comparing “unit volume mass γ ₁ on the recipe” with “unit volume mass γ ₂ obtained in the test”. The unit volume mass is calculated as a value excluding the amount of air. It is assumed that the unit volume mass γ ₁ and γ ₂ show the same value in the concrete mixed with the regular composition.
Civil Engineering Research Laboratories, “Measurement of Unit Water Volume of Fresh Concrete”, “Unit Water Volume Estimation Manual by Air Meter Method (Public Works Research Institute Law) [pdf]”, [online], [Search September 5, 2008] Internet (URL: http://www.pwri.go.jp/jpn/seika/tani-suiryou/tani-suiryou.html)

  Usually, when using an air meter, concrete is manufactured based on a compounding table (mixing plan), a sample is taken with the manufactured concrete being uncured, and the amount of air contained in the sample is measured. In the background art, while the difference in the amount of air between the blending table and the manufactured concrete is expected, the unit water volume on the blending table depends on the amount of water contained in the fine aggregate, specifically the surface water of the fine aggregate. The unit water volume was estimated on the assumption that the various other quantities were the same in the blending table and the manufactured concrete, with only the error due to the setting.

  However, in the relationship between the blending table and the manufactured concrete, if there is a manufacturing error in any one of the measured values and air volume of each material such as cement, aggregate, water, etc., the volume of the entire manufactured concrete Does not match the volume based on the recipe. Therefore, even if each material is individually weighed in accordance with the preparation table, the unit volume mass of the produced concrete does not match the value in the preparation table. This is because, in the background art, the manufactured concrete was estimated using the unit water amount on the preparation table, assuming that it was a regular blend, and it was difficult to say that the unit water amount could be accurately estimated.

  Furthermore, if the manufactured concrete and the sample collected from this are the same, there is a question as to whether or not coarse aggregate could be sampled from the manufactured concrete at the same rate, and the error is also affected by the sampling operation. Can occur.

  In short, in the background art, although there is a manufacturing error between the mixing table and the concrete to be manufactured, the estimation is based only on the unit water amount on the mixing table, and an error may occur. There is also an error due to sampling between the manufactured concrete and the sample. Therefore, in the estimation method using the air meter of the background art, there are two stages of error generation factors.

  Therefore, without using the numerical value of the unit water amount on the preparation table affected by the manufacturing error, and also to reduce the sampling operation error, using the coarse aggregate amount of the sample that can be determined as a numerical value, It is preferable to estimate the unit water amount.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a method for estimating the unit water amount of concrete using an air meter that can improve the estimation accuracy.

The method for estimating the unit water amount of concrete using an air meter according to the present invention produces uncured product concrete by weighing based on a blending plan, collects sample concrete to be measured from the produced product concrete, It is a method for estimating the unit water amount of the product concrete from the measured value of the concrete, and the density (ω / V (kg / liter)) of the sample concrete obtained using an air meter, the amount of air in the sample concrete ( Air _m (%)) and the value of the unit coarse aggregate amount (G _m (kg / m ³ )) of the sample concrete, the planned unit cement amount (C ₀ (kg / m ³ )) of the mixing plan, and the planned unit Using the coarse aggregate amount (G ₀ (kg / m ³ )) and the planned air amount (Air ₀ (%)) value, the following formula 5 The unit water amount (W _A (kg / m ³ )) of the product concrete is estimated from the above.

ここで、
ρ_g：粗骨材密度（kg/リットル）
Ｃ_A：製品コンクリートの単位セメント量（kg/m³）
Ｓ_A：製品コンクリートの単位細骨材量（kg/m³）
Ｇ_A：製品コンクリートの単位粗骨材量（kg/m³）
Air_A：製品コンクリートの空気量（%）
Ｍ_m：サンプルコンクリートの単位モルタル量（混入空気量を含む）（リットル）
Ｓ_m：サンプルコンクリートの単位細骨材量（kg/m³）
Ｗ_m：サンプルコンクリートの単位水量（kg/m³）

ρ_s：細骨材密度（kg/リットル）
ρ_c'：水を使用した試験によるセメント密度（kg/リットル）
Ｃ_m：サンプルコンクリートの単位セメント量（kg/m³）

Formula 1:
C ₀ : G ₀ = C _A : G _A
Formula 2:
C ₀ / (1000 · (1−Air _0/100 )) = C _A / (1000 · (1−Air _A / 100))
Formula 3:
W _A : C _A : S _A = W _m : C _m : S _m
Formula 4:
Air _m = Air _A
Formula 5:

here,
ρ _g : Coarse aggregate density (kg / liter)
C _A : Unit cement amount of product concrete (kg / m ³ )
S _A : Unit fine aggregate amount of product concrete (kg / m ³ )
G _A: Unit coarse aggregate amount of product Concrete (kg / m ³⁾
Air _A : Product concrete air volume (%)
M _m : Amount of mortar of sample concrete (including mixed air) (liter)
S _m : Amount of fine aggregate of sample concrete (kg / m ³ )
W _m : Unit water volume of sample concrete (kg / m ³ )

ρ _s : Fine aggregate density (kg / liter)
ρ _{c '} : Cement density by test using water (kg / liter)
C _m : Unit cement amount of sample concrete (kg / m ³ )

  The coarse aggregate of the sample concrete is extracted by separating the sample concrete from other components by putting the sample concrete into a sieve and sieving in water.

  The weight of the coarse aggregate is measured by being immersed in water.

  In the concrete unit water amount estimation method using the air meter according to the present invention, the estimation accuracy of the unit water amount can be increased.

  Hereinafter, a preferred embodiment of a method for estimating a unit water amount of concrete using an air meter according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an outline of the concept of a unit water amount estimation method for concrete using the air meter according to the present embodiment.

  Assume that the unit volume mass of each material used in the blending plan, product concrete (product), and sample concrete (sample in the air meter) is equal. Here, the product concrete refers to, for example, uncured concrete manufactured by weighing at a production plant or the like based on a blending plan. The manufactured product concrete is shipped from, for example, a manufacturing plant and carried into the site, and sample concrete to be measured by an air meter is taken from the site-received concrete and the like carried into the site.

Using an air meter on the sample concrete collected, the density of the sample concrete (ω / V (kg / liter)), the amount of air in the sample concrete (Air _m (%)), and the amount of coarse aggregate of the sample concrete Obtain the measured value of (G _m (kg / m ³ )).

  Regarding the relationship between the blending plan and the product concrete, it is estimated that the unit water amount, the unit cement amount, the unit fine aggregate amount, and the unit coarse aggregate amount are different due to the surface water error of the fine aggregate and the manufacturing error. Moreover, it is estimated that the amount of mixed air is also different. The relationship between the mix plan and product concrete is as follows.

  In the mixing plan and product concrete, when considering the mixing ratio (mixing ratio: the same applies below), the mixing ratio of the unit cement amount and the unit coarse aggregate amount is both less likely to be affected by surface water, etc., and is accurate. Since weighing is performed, they are considered equal.

Formula 1:
C ₀ : G ₀ = C _A : G _A

here,
C ₀ : Plan unit cement amount (kg / m ³ )
C _A : Unit cement amount of product concrete (kg / m ³ )
G ₀ : Plan unit coarse aggregate amount (kg / m ³ )
G _A: Unit coarse aggregate amount of product Concrete (kg / m ³⁾

  In addition, in the blending plan and the product concrete, it is considered that the blending ratio of the unit cement amount is equal except for the air amount when considered by the blending ratio.

C _A / C ₀ = (100−Air _A ) / (100−Air ₀ )

This is a conversion of the following formula in liters.

Formula 2:
C ₀ / (1000 · (1−Air _0/100 )) = C _A / (1000 · (1−Air _A / 100))

here,
Air ₀ : Planned air volume (%)
Air _A : Air content in product concrete (%)

  On the other hand, regarding the relationship between the product concrete and the sample, it can be considered that the mixed air amount is equal.

Formula 4:
Air _m = Air _A

here,
Air _m : Air volume in sample concrete (%)

  Regarding the relationship between the product concrete and the sample, it can be estimated that the unit water amount, the unit cement amount, the unit fine aggregate amount, and the unit coarse aggregate amount are different due to the sampling error. This allows for sampling errors especially for coarse aggregates. It is unlikely that the fine mortar constituents of the particles are partially offset due to the sampling error of coarse aggregates with large particles compared to other ingredients, and the mixture of product concrete and sample mortar constituents Both ratios are considered equal.

Formula 3:
W _A : C _A : S _A = W _m : C _m : S _m

here,
W _A: unit water content of the product concrete (kg / m ³⁾
S _A : Unit fine aggregate amount of product concrete (kg / m ³ )
W _m : Unit water volume of sample concrete (kg / m ³ )
C _m : Unit cement amount of sample concrete (kg / m ³ )
S _m : Amount of fine aggregate of sample concrete (kg / m ³ )

The concrete unit water amount estimation method using the air meter according to the present embodiment is based on the above-mentioned concept, without using the numerical value of the unit water amount on the blending plan that is affected by the manufacturing error, and also for the error of the sampling operation. In order to decrease, the unit water amount of the product concrete is estimated using the coarse aggregate amount of the sample concrete that can be determined as a numerical value, and the actual value obtained by the measurement using the air meter described below is used. Thus, the unit water volume is estimated.

[1] Measurement operation using an air meter
[1.1] Instruments and materials used / Pressure type air meter / balance: A capacity of 25 kg or more and a minimum scale of 1 g or less are preferable.
-5 mm sieve: A sieve with a handle having a nominal aperture of 4.75 mm, a wire diameter of 1.6 mm, an outer diameter of φ250 mm, and a height of 300 mm is preferable.
・ Washing container: Used to wash sample concrete collected in a sieve. It is convenient to use 18-20 liter plastic buckets and pail cans.
-Towel waste: Used to wipe moisture adhering to coarse aggregate. To measure the weight of coarse aggregate in water, towel waste is not necessary, and a dedicated scale and container are used instead.

[1.2] Preparation before measurement / Measurement of mass and volume of air meter Measure the mass (w ₁ (kg)) of the lower container and lid of the air meter, and measure the volume (V (liter)) of the lower container. The volume is determined by filling the container with water and measuring the mass of the water. When the lower container is filled with water, it is preferable to use a glass plate in order to make the water surface accurately coincide with the upper edge of the container.
・ Air meter pressure gauge verification ・ Material coefficient setting The density of coarse aggregate to be used is determined based on the test result table, and the cement density is determined based on Table 1, etc. Also, the aggregate correction coefficient is measured according to JIS A 1128. When the aggregate correction factor is other than 0, a value obtained by subtracting the aggregate correction factor from the measured air amount is used as the measured air amount (Air _m (%)).

[1.3] Fill the lower container with sample concrete according to the measurement and air volume measurement method, level the surface, and tighten the lid.
・ Measure the mass (w ₂ (kg)) of each container. This is the case of the non-water injection method, but in the case of the water injection method, water is injected after this.
・ Measure the air volume in units of 0.1%.
・ Wash the sample concrete in the air meter on a 5mm sieve and take out only the coarse aggregate.
-The coarse aggregate remaining on the sieve is dried and saturated with water, and the mass (w ₃ (kg)) is measured. At this time, the surface of the washed coarse aggregate is wiped off with towel cloth.

[1.4] End of measurement By performing the above measurement operation, the density (ω / V () of the weight (ω (kg) = w ₂ −w ₁ ) and volume (V: volume of the lower container) of the sample concrete is measured. kg / liter)) as well as the actual value of the air content (Air _m (%)) in the sample concrete. The unit coarse aggregate amount (G _m (kg / m ³ )) of the sample concrete can also be obtained from the following equation as an actual measurement value.

Coarse aggregate weight in air meter (g (kg)) = w ₃ / (1-δg)
Unit coarse aggregate amount of sample concrete (G _m ) = g · 1000 / V Formula (i)

At this time, the value of the unit mortar amount (including the amount of mixed air) (M _m (liter)) of the sample concrete can also be obtained from the following equation. [rho _g is the coarse aggregate density (kg / l).

Unit mortar amount of sample concrete (M _m ) = 1000−G _m / ρ _g formula (ii)

[2] Derivation of unit water volume (W _A (kg / m ³ )) estimation formula for product concrete
[2.1] Physical quantities in the following description are as follows.

C ₀ : Plan unit cement amount (kg / m ³ )
G ₀ : Plan unit coarse aggregate amount (kg / m ³ )
Air ₀ : Planned air volume (%)

W _m : Unit water volume of sample concrete (kg / m ³ )
C _m : Unit cement amount of sample concrete (kg / m ³ )
S _m : Amount of fine aggregate of sample concrete (kg / m ³ )
G _m : Unit coarse aggregate amount of sample concrete (kg / m ³ ) = g · 1000 / V
Air _m : Air volume in sample concrete (%); measured value

W _A: unit water content of the product concrete (kg / m ³⁾
C _A : Unit cement amount of product concrete (kg / m ³ )
S _A : Unit fine aggregate amount of product concrete (kg / m ³ )
G _A: Unit coarse aggregate amount of product Concrete (kg / m ³⁾
Air _A : Air content in product concrete (%) = Air _m

ρ _w : Water density (kg / liter = g / cm ³ ) = 1.0
ρ _{c ′} : Cement density by water test (kg / liter); see Table 1 ρ _s : Fine aggregate density (kg / liter); According to test results table ρ _g : Coarse aggregate density (kg / liter) ; According to test report

ω: Weight of sample concrete in air meter (kg) = w ₂ −w ₁
V: air meter volume (liter); measured value g: coarse aggregate weight (kg) of sample concrete = w ₃ / (1−δg)
M _m : unit mortar amount of sample concrete (liter) = 1000−G _m / ρ _g

[2.2] Explain the derivation of the unit water quantity (W _A (kg / m ³ )) estimation formula for product concrete.

Rearranging equation 1 in G _A,

G _A = C _A · G ₀ / C ₀ Formula (iii)

It becomes.

Substituting Equation 4 and organizing Equation 2 with C _A ,

C _A = C ₀ · (100−Air _m ) / (100−Air ₀ ) Formula (iv)

It becomes.

Equation 3 shows that the mixing ratios of water, cement, and fine aggregate in the mortar of the product concrete and the sample concrete are equal, and from FIG. 1, each mortar component (unit) in the product concrete and the sample concrete is shown. Cement amount, unit water amount, unit fine aggregate amount) is obtained by subtracting coarse aggregate amount from the whole, and since the blending ratio of mortar components in these product concrete and sample concrete is equal,

C _A : (1000−G _A / ρ _g ) = C _m : (1000−G _m / ρ _g ) Formula (v)

It becomes.

Substituting the above formulas (ii) to (iv) into the formula (v) and arranging them by C _m ,

It becomes. This is defined as formula (vi).

Next, the relationship between the unit amount and the volume of the material in the sample concrete can be expressed as follows, taking into account the density of water (ρ _w = 1.0) and organizing by the amount excluding the air amount from the whole. Can do.

1000 · (1-Air _m / 100) = W _m + C _m / ρ _{c ′} + S _m / ρ _s + G _m / ρ _g (vii)

Moreover, when arranging by the mortar content (including the amount of mixed air) in the sample concrete M _m , it can be expressed as follows by subtracting the coarse aggregate from the whole.

M _m = 1000 · Air _m / 100 + W _m + C _m / ρ _{c ′} + S _m / ρ _s Formula (viii)

On the other hand, the density of sample concrete can be expressed as follows in terms of the amount of material excluding the amount of mixed air.

ω / V = (W _m + C _m + S _m + G _m ) / 1000 formula (ix)

When formula (ix) is arranged by unit fine aggregate amount S _m ,

S _m = 1000Ω / V−W _m −C _m −G _m Formula (x)

It becomes.

Substituting equation (x) into equation (viii) and organizing with W _m ,

It becomes. This is defined as equation (xi).

From Formula 3, in the product concrete and the sample concrete, it can be expressed as follows that the blending ratio of the unit water amount in the mortar obtained by subtracting the coarse aggregate amount from the whole is constant.

W _A : W _m = (1000−G _A / ρ _g ): (1000−G _m / ρ _g ) Formula (xii)

The equation (xii), using equation (ii) ~ (iv), when organized in W _A,

Thus, the above formula 5 is obtained.

Based on the above process, the unit water amount W _A product concrete is obtained as follows. First, C _m is calculated by adding C ₀ , G ₀ , Air ₀ of the formulation plan, the measured value M _m, and ρ _g which is a known amount to the above formula (vi). Next, the measured value M _m , G _m , Air _m , ω, V, the known quantities ρ _s , ρ _{c ′,} and the calculated value C _m are added to the above equation (xi) to calculate W _m . calculate. Finally, G ₀ and Air ₀ of the formulation plan, measured values M _m and Air _m , ρ _g which is a known amount, and calculated value W _m are included in the above formula 5. Thus, it is possible to obtain the unit water content W _A product concrete.

[2.3] Calculation of other quantities other than unit water quantity (a) Unit fine aggregate quantity S _{A of} product concrete:
From Formula 3, in the product concrete and sample concrete, it can be expressed as follows that the blending ratio of the unit fine aggregate amount in the mortar obtained by subtracting the coarse aggregate amount from the whole is constant.

S _A : S _m = (1000−G _A / ρ _g ) :( 1000−G _m / ρ _g ) Formula (xiii)

The formula (xiii), using the above equation (ii) ~ (iv), when organized in S _A,

It becomes. This is defined as equation (xiv).

Unit fine aggregate amount S _A product concrete is obtained as follows. First, S _m is calculated by adding measured values ω, V, G _m and calculated values W _m , C _m to the above equation (x). Next, G ₀ and Air ₀ of the formulation plan, measured values M _m and Air _m , ρ _g which is a known amount, and calculated value S _m are included in the above formula (xiv). Thus, it is possible to obtain the unit fine aggregate amount S _A product concrete.

(B) Unit cement amount C _{A of} product concrete:
The above formula 2 can be obtained by including C ₀ , Air ₀ of the blending plan and the measured value Air _m .

(C) Unit coarse aggregate amount G _{A of} product concrete:
In equation 1, it can be obtained by inclusion with C _0, G ₀ formulation plan, the calculation value C _A.

(D) The water-cement ratio (W _A / C _A ) of the product concrete can also be obtained.

[3] Evaluation of estimation formula for unit water volume of product concrete (W _A (kg / m ³ )) FIG. 2 and FIG. 3 show the background technology (Doken formula) and this embodiment (proposed formula) for the laboratory and It shows the error tendency between the measured value of unit water volume and the planned value in the field unloading test (with sample concrete) including manufacturing errors. FIG. 2 shows the result according to the background art, and FIG. 3 shows the result according to the present embodiment. The horizontal axis represents the unit water volume setting value, and the vertical axis represents the unit water volume calculation value. For each specimen, the unit water amount calculated value calculated using the measured value is plotted against the unit water amount set value. A straight line α is a case where the set value and the calculated value completely match, and dotted lines β and γ indicate a range of error ± 10 kg. The straight lines y1 and y2 are empirical formulas in the background art and the present embodiment. R ² is a multiple correlation coefficient. As can be understood from these figures, the proposed equation has a smaller error in the calculated value with respect to the set value and less variation in data than the Doken equation, and the estimation accuracy can be improved.

In the concrete unit water amount estimation method using the air meter according to the present embodiment described above, uncured product concrete is manufactured by measurement based on the blending plan, and the sample concrete to be measured from the manufactured product concrete Is a method to estimate the unit water volume of product concrete from the measured values of sample concrete, and the density of sample concrete (ω / V (kg / liter)) obtained using an air meter and the air in the sample concrete Value (Air _m (%)) and unit coarse aggregate amount (G _m (kg / m ³ )) of sample concrete, planned unit cement amount (C ₀ (kg / m ³ )) and plan of blending plan Using the value of the unit coarse aggregate amount (G ₀ (kg / m ³ )) and the planned air amount (Air ₀ (%)), from the relationship of Equation 1 to Equation 4 above, It has so as to estimate the unit water product Concrete ^{_{(W A (kg / m 3}} )) from the cleat does not use the planning unit water at all, it is possible to eliminate the influence of errors caused at the time of manufacture. Moreover, since the coarse aggregate amount of the sample concrete that can be determined as the measurement value is used, the measurement error related to the coarse aggregate amount caused by the sampling operation can be reduced. By these, the estimation accuracy of the unit water quantity of the concrete which uses an air meter can be improved significantly. In addition, for product concrete, the unit quantities of all materials can be calculated.

  Coarse aggregate of sample concrete was put in a sieve and all the sample concrete was put into a sieve and extracted from other components by sieving in water. Can be measured.

  If the weight of the coarse aggregate is measured by immersing it in water, it can be easily measured without requiring a drying operation.

  Moreover, workability | operativity can be improved by using the thing of a basket form as a sieve for washing out coarse aggregate.

It is explanatory drawing which shows the view of the unit water amount estimation method of the concrete which uses the air meter concerning this invention. It is a graph which shows the relationship between the unit water amount setting value and unit water amount calculation value according to background art. It is a graph which shows the relationship between the unit water quantity setting value and the unit water quantity calculation value according to the unit water quantity estimation method of the concrete which uses the air meter concerning this invention.

Claims (3)

A method of producing uncured product concrete by weighing based on the blending plan, collecting sample concrete to be measured from the produced product concrete, and estimating the unit water amount of the product concrete from the measured value of the sample concrete. There,
The density (ω / V (kg / liter)) of the sample concrete obtained using an air _{meter, the} amount of air in the sample concrete (Air _m (%)), and the unit coarse aggregate amount of the sample concrete (G _m (Kg / m ³ )), planned unit cement amount (C ₀ (kg / m ³ )), planned unit coarse aggregate amount (G ₀ (kg / m ³ )), and planned air amount (Air ₀ (%)) and
Unit water volume of concrete using an air meter characterized by estimating unit water volume (W _A (kg / m ³ )) of the product concrete from the sample concrete by the following formula 5 from the relationship of the following formulas 1 to 4. Estimation method.
Formula 1:
C ₀ : G ₀ = C _A : G _A
Formula 2:
C ₀ / (1000 · (1−Air _0/100 )) = C _A / (1000 · (1−Air _A / 100))
Formula 3:
W _A : C _A : S _A = W _m : C _m : S _m
Formula 4:
Air _m = Air _A
Formula 5:

here,
ρ _g : Coarse aggregate density (kg / liter)
C _A : Unit cement amount of product concrete (kg / m ³ )
S _A : Unit fine aggregate amount of product concrete (kg / m ³ )
G _A: Unit coarse aggregate amount of product Concrete (kg / m ³⁾
Air _A : Product concrete air volume (%)
M _m : Amount of mortar of sample concrete (including mixed air) (liter)
S _m : Amount of fine aggregate of sample concrete (kg / m ³ )
W _m : Unit water volume of sample concrete (kg / m ³ )

ρ _s : Fine aggregate density (kg / liter)
ρ _{c '} : Cement density by test using water (kg / liter)
C _m : Unit cement amount of sample concrete (kg / m ³ )

  The air meter according to claim 1, wherein the coarse aggregate of the sample concrete is extracted by separating the sample concrete from other components by putting the sample concrete into a sieve and sieving in water. A method for estimating the unit water volume of concrete.   The method for estimating a unit water amount of concrete using an air meter according to claim 1 or 2, wherein the weight of the coarse aggregate is measured by being immersed in water.

Images