JP5709653B2 - Method for obtaining dynamic elastic modulus of coarse aggregate and method for predicting drying shrinkage strain of concrete - Google Patents
Method for obtaining dynamic elastic modulus of coarse aggregate and method for predicting drying shrinkage strain of concrete Download PDFInfo
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- 239000004567 concrete Substances 0.000 title claims description 52
- 238000001035 drying Methods 0.000 title claims description 37
- 238000000034 method Methods 0.000 title claims description 29
- 239000011435 rock Substances 0.000 claims description 28
- 238000005259 measurement Methods 0.000 description 16
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 230000008602 contraction Effects 0.000 description 6
- 239000000463 material Substances 0.000 description 5
- 239000004568 cement Substances 0.000 description 4
- 239000004576 sand Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 235000019738 Limestone Nutrition 0.000 description 2
- 210000000988 bone and bone Anatomy 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 239000006028 limestone Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 239000011398 Portland cement Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000010881 fly ash Substances 0.000 description 1
- 239000010438 granite Substances 0.000 description 1
- -1 hard sandstone Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000011150 reinforced concrete Substances 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000010454 slate Substances 0.000 description 1
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Description
本発明は、粗骨材の動弾性係数を求める方法と、該係数を用いてコンクリートの乾燥収縮ひずみを予測する方法に関する。 The present invention relates to a method for obtaining a dynamic elastic modulus of a coarse aggregate and a method for predicting a drying shrinkage strain of concrete using the coefficient.
コンクリートは引張強度が低いため、コンクリートの収縮によりひび割れ（収縮ひび割れ）が発生する場合がある。このひび割れは、コンクリート造建築物の美観を損なうほか、コンクリートの水密性・気密性の低下や鉄筋の腐食などの、建築物の耐久性低下の原因にもなっている。したがって、コンクリートの耐久性を確保するためには、収縮ひび割れを制御することが必要となる。
この収縮ひび割れは、乾燥によって生じるコンクリートの収縮ひずみ（以下「乾燥収縮ひずみ」という。）と高い相関があることが知られている。したがって、コンクリートの収縮ひび割れを制御するためには、乾燥収縮ひずみを知る必要がある。
Since concrete has low tensile strength, cracks (shrinkage cracks) may occur due to shrinkage of the concrete. These cracks not only detract from the aesthetics of the concrete building, but also cause deterioration in the durability of the building, such as deterioration of the water and air tightness of the concrete and corrosion of the reinforcing bars. Therefore, in order to ensure the durability of concrete, it is necessary to control shrinkage cracks.
This shrinkage crack is known to have a high correlation with the shrinkage strain of concrete caused by drying (hereinafter referred to as “drying shrinkage strain”). Therefore, in order to control the shrinkage crack of concrete, it is necessary to know the drying shrinkage strain.
従来、乾燥収縮ひずみは、ＪＩＳ Ａ １１２９−１〜３「モルタル及びコンクリートの長さ変化測定方法」と、附属書Ａ（参考）「モルタル及びコンクリートの乾燥による自由収縮ひずみ試験方法」に準じ、実測していた。
具体的には、工事に用いようとしているコンクリートの配合に従い、１００×１００×４００ｍｍの角柱供試体を作製し、この供試体を２０℃で７日間、水中養生した後、温度２０±２℃、相対湿度６０±５％ＲＨの環境下に置き、乾燥期間６か月後における供試体の乾燥収縮ひずみを実測して求めていた。
Conventionally, the drying shrinkage strain was measured according to JIS A 1129-1-3 “Method for measuring changes in length of mortar and concrete” and Annex A (reference) “Test method for free shrinkage strain by drying mortar and concrete”. Was.
Specifically, according to the concrete composition to be used for the construction, a 100 × 100 × 400 mm prismatic specimen was prepared, and this specimen was cured in water at 20 ° C. for 7 days. The sample was placed in an environment with a relative humidity of 60 ± 5% RH, and the drying shrinkage strain of the specimen after the drying period of 6 months was measured and determined.
しかし、この方法では、乾燥収縮ひずみの値が、収縮ひび割れ抑制のために要求される値以下であるか否か判明するまで、６か月もの長期間を要する。したがって、前記ＪＩＳの方法では、コンクリートの品質管理に時間がかかることが問題であった。 However, in this method, it takes a long period of 6 months until it is determined whether or not the value of the drying shrinkage strain is not more than the value required for suppressing shrinkage cracking. Therefore, the JIS method has a problem that it takes time to control the quality of the concrete.
そこで、この問題に対処するため、コンクリートの乾燥収縮ひずみを、前記ＪＩＳ等の試験によらずに、推測することができる予測式が提案されている。
例えば、非特許文献１では、コンクリートの体積、外気に接する表面積、体積表面積比、相対湿度などのパラメータを含む式に、セメントなどの種類の影響を表す修正係数を含む式を乗じてなる下記の提案式（予測式）が提示されている。
Therefore, in order to deal with this problem, a prediction formula has been proposed that can estimate the drying shrinkage strain of concrete without using the JIS test.
For example, in Non-Patent Document 1, the following formula is formed by multiplying an equation including parameters such as the volume of concrete, a surface area in contact with the outside air, a volume surface area ratio, a relative humidity, and a correction coefficient representing the effect of the type of cement and the like. A proposal formula (prediction formula) is presented.
しかし、上記の提案式では、粗骨材などのコンクリートの構成材料の特性は、ほとんど考慮されず、非特許文献１の付図２．４中の提案式の図に示すように、その予測精度は必ずしも十分とはいえない（図１の左上の図参照）。 However, in the above proposed formula, the characteristics of the constituent materials of concrete such as coarse aggregate are hardly considered, and the prediction accuracy is as shown in the diagram of the proposed formula in Attached Figure 2.4 of Non-Patent Document 1. It is not necessarily sufficient (see the upper left figure in FIG. 1).
また、非特許文献２では、粗骨材の動弾性係数とコンクリートの収縮率（乾燥収縮ひずみ）との間の相関関係が示されている（図２参照）。
しかし、この図２から分かるように、例えば、動弾性係数が１５ｋＮ／ｍｍ２の粗骨材を用いたコンクリートの収縮率は、その平均値が約６００μであるのに対し、その変動幅は約４００μ（±２００μ）もあって、平均値に対する変動幅の割合は約７割と大きい。したがって、非特許文献２に記載の相関関係に基づき、粗骨材の動弾性係数を用いてコンクリートの収縮率を予測したとしても、その精度は不十分であると予想され、更なる精度の向上が望まれている。
However, as can be seen from FIG. 2, for example, the shrinkage rate of concrete using a coarse aggregate having a kinematic elastic modulus of 15 kN / mm 2 is about 600 μm, whereas the fluctuation range is about There are 400μ (± 200μ), and the ratio of the fluctuation range to the average value is as large as about 70%. Therefore, even if the shrinkage rate of concrete is predicted using the dynamic elastic modulus of coarse aggregate based on the correlation described in
そこで、本発明は、コンクリートの乾燥収縮ひずみを、簡易に精度よく予測することができる方法等を提供することを目的とする。 Then, an object of this invention is to provide the method etc. which can predict the drying shrinkage | contraction distortion of concrete easily and accurately.
本発明者は、上記課題を解決するために鋭意研究した結果、最長径が特定の長さ以上の粗骨材を、平面加工等の端部の処理を行うことなく、そのまま用いて求めた動弾性係数と、該粗骨材を用いたコンクリートの乾燥収縮ひずみとの間に、良好な直線関係があること等を見い出し、本発明を完成した。 As a result of earnest research to solve the above problems, the present inventor has obtained the motion obtained by using the coarse aggregate having the longest diameter not less than a specific length as it is without performing end processing such as planar processing. The present invention was completed by finding that there is a good linear relationship between the elastic modulus and the drying shrinkage strain of the concrete using the coarse aggregate.
すなわち、本発明は以下の構成を有するものである。
［１］下記の（Ａ）工程および（Ｂ）工程を少なくとも含む、粗骨材の動弾性係数を求める方法を用いて求めた動弾性係数が、３３．７〜５６．３ｋＮ／ｍｍ ２ の火成岩、または該動弾性係数が３７．９〜６２．３ｋＮ／ｍｍ ２ の堆積岩である粗骨材を含むコンクリートの乾燥収縮ひずみを予測する方法であって、
該粗骨材の動弾性係数の値を用いて、下記（３）式から該粗骨材を含むコンクリートの乾燥収縮ひずみの予測値を算出して予測する、コンクリートの乾燥収縮ひずみを予測する方法。
ｙ＝ａｘ−ｂ ……（３）
（式中、ｙは乾燥期間２６週におけるコンクリートの乾燥収縮ひずみ（×１０ −６ ）を、ｘは粗骨材の動弾性係数（ｋＮ／ｍｍ ２ ）を表す。また、ａは、粗骨材が火成岩の場合は１１．５３６、堆積岩の場合は２１．１９５であり、ｂは、粗骨材が火成岩の場合は１２０１．６、堆積岩の場合は１８１２．２である。）
（Ａ）最長径が１５ｍｍ以上の粗骨材の最長径の一端に、超音波伝播時間測定器の発信子を接触させるとともに、該粗骨材の最長径の他端に、該測定器の受信子を接触させた状態で、該粗骨材における超音波の伝播時間を測定する工程
（Ｂ）前記（Ａ）工程で得られた超音波伝播時間の値を用いて、下記（１）式に基づき該粗骨材の動弾性係数を算出する工程
Ｅｄ＝（Ｌ／Ｔ）２・ρ ……（１）
（式中、Ｅｄは動弾性係数を表し、Ｌは粗骨材の最長径を表し、Ｔは超音波伝播時間を表し、ρはＪＩＳ Ａ １１１０に準拠して求めた粗骨材の絶乾密度を表す。）
That is, the present invention has the following configuration.
[1] (A) step and step (B) at least including the dynamic elastic modulus was determined using the method for determining the dynamic elastic modulus of coarse aggregate the following, the 33.7~56.3kN / mm 2 igneous or animal modulus is a method for predicting the distortion drying shrinkage of concrete containing coarse aggregate is in sedimentary rocks 37.9~62.3kN / mm 2,
A method for predicting dry shrinkage strain of concrete by calculating a predicted value of dry shrinkage strain of concrete containing the coarse aggregate from the following equation (3) using the value of the dynamic elastic modulus of the coarse aggregate .
y = ax−b (3)
(In the formula, y represents the drying shrinkage strain (× 10 −6 ) of concrete at a drying period of 26 weeks , x represents the kinematic elastic modulus (kN / mm 2 ) of the coarse aggregate, and a represents the coarse aggregate. Is 11.536 for igneous rocks, 21.195 for sedimentary rocks, b is 1201.6 for coarse aggregates igneous rocks, and 1812.2 for sedimentary rocks.)
(A) The transmitter of the ultrasonic propagation time measuring instrument is brought into contact with one end of the longest diameter of the coarse aggregate having a longest diameter of 15 mm or more, and the other end of the longest diameter of the coarse aggregate is received by the measuring instrument. The step of measuring the ultrasonic wave propagation time in the coarse aggregate with the child in contact (B) Using the value of the ultrasonic wave propagation time obtained in the step (A), the following equation (1) Step of calculating the kinematic elastic coefficient of the coarse aggregate based on E d = (L / T) 2 · ρ (1)
(In the formula, E d represents the dynamic elastic modulus, L represents the longest diameter of the coarse aggregate, T represents the ultrasonic wave propagation time, and ρ represents the absolute dryness of the coarse aggregate determined in accordance with JIS A 1110. Represents density)
本発明の予測方法によれば、コンクリートの乾燥収縮ひずみを、精度よく予測することができる。
According to the prediction method of the present invention, the drying shrinkage strain of concrete can be accurately predicted.
本発明は、前記したとおり、（Ａ）粗骨材における超音波伝播時間の測定工程と、（Ｂ）粗骨材の動弾性係数の算出工程とを含んでなる、コンクリートの乾燥収縮ひずみを予測する方法である。
以下に、本発明について、粗骨材の動弾性係数を求める方法とコンクリートの乾燥収縮ひずみを予測する方法に分けて、説明する。
The present invention, as described above, the step of measuring ultrasonic wave propagation time in (A) coarse aggregate, (B) comprising a step of calculating the dynamic elastic modulus of coarse aggregate, the drying shrinkage strain concrete It is a method of prediction.
Hereinafter, the present invention will be described by dividing it into a method for obtaining the dynamic elastic modulus of the coarse aggregate and a method for predicting the drying shrinkage strain of the concrete.
１．粗骨材の動弾性係数を求める方法
（Ａ）粗骨材における超音波の伝播時間を測定する工程
（i）粗骨材について
該工程において測定に供する粗骨材の最長径は、通常、１５ｍｍ以上であり、２０ｍｍ以上が好ましく、２５ｍｍ超がより好ましい。粗骨材の最長径が１５ｍｍ未満では、超音波の伝播距離が短いため、超音波伝播時間の測定値の誤差が大きくなる傾向がある。
ここで最長径とは、粗骨材１個がちょうど納まる直方体を考え、この直方体を形成する３種の直行する線（縦線、横線および高さの線）のうち、最長の線およびその線の長さをいう。
1. Method of obtaining dynamic elastic modulus of coarse aggregate (A) Step of measuring ultrasonic propagation time in coarse aggregate (i) About coarse aggregate The longest diameter of the coarse aggregate used for measurement in this step is usually 15 mm. It is above, 20 mm or more is preferable and more than 25 mm is more preferable. When the longest diameter of the coarse aggregate is less than 15 mm, the propagation distance of the ultrasonic wave is short, so that the error in the measured value of the ultrasonic wave propagation time tends to increase.
Here, the longest diameter is a rectangular parallelepiped in which only one coarse aggregate is contained, and the longest line and its line among three kinds of perpendicular lines (vertical line, horizontal line, and height line) forming this rectangular parallelepiped. The length of
また、該工程において測定に供する粗骨材の状態は、風乾状態が好ましく、絶乾状態がより好ましい。ここで絶乾状態とは、粗骨材の質量が恒量になるまで乾燥した状態をいう。この粗骨材の状態を含水率で示すと、含水率が２．０質量％以下の粗骨材が好ましく、１．０質量％以下がより好ましく、０．１質量％以下が更に好ましい。該含水率が２．０質量％を超えると、超音波伝播時間の測定値の誤差が大きくなる傾向がある。 Moreover, the state of the coarse aggregate used for the measurement in this step is preferably an air-dried state, and more preferably an absolutely dry state. Here, the absolutely dry state means a state where the coarse aggregate is dried until the mass of the coarse aggregate becomes constant. When the state of this coarse aggregate is shown by the moisture content, a coarse aggregate having a moisture content of 2.0% by mass or less is preferable, 1.0% by mass or less is more preferable, and 0.1% by mass or less is still more preferable. When the moisture content exceeds 2.0% by mass, the error in the measured value of the ultrasonic propagation time tends to increase.
粗骨材の種類は、特に制限されないが、玄武岩、安山岩、流紋岩、花崗岩、角閃岩、斑レイ岩等の火成岩や、石灰石、硬質砂岩、粘板岩、砂岩、凝灰岩等の堆積岩や、砂利などから選ばれる、少なくとも１種以上が挙げられる。かかる粗骨材は、天然骨材でも再生骨材でもよい。また、前記測定に供する粗骨材は、コンクリートに用いる粗骨材と同一であれば、予測精度が向上するため好ましい。 The type of coarse aggregate is not particularly limited, but igneous rocks such as basalt, andesite, rhyolite, granite, amphibolite, gabbro, sedimentary rocks such as limestone, hard sandstone, slate, sandstone, tuff, gravel, etc. At least one selected from the group consisting of: Such coarse aggregate may be natural aggregate or recycled aggregate. Moreover, if the coarse aggregate used for the said measurement is the same as the coarse aggregate used for concrete, since prediction accuracy improves, it is preferable.
（ii）超音波伝播時間の測定について
該測定では、図３に示すように、粗骨材の最長径の一端に、超音波伝播時間測定器の発信子を接触させるとともに、該粗骨材の最長径の他端に、該測定器の受信子を接触させた状態で、該粗骨材における超音波の伝播時間を測定する。この測定方法では、粗骨材の最長径の両端を平面化する作業が不要となり、該測定の作業時間が、前記従来の方法と比べて、大幅に短縮できる。
超音波伝播時間の測定に供する粗骨材の個数は、１０個以上が好ましい。図４に示すように、粗骨材の測定個数が１０個以上であれば、該測定値の平均は、粗骨材の母集団の測定値の平均に収束する傾向がある。
(Ii) Measurement of ultrasonic propagation time In this measurement, as shown in FIG. 3, the transmitter of the ultrasonic propagation time measuring instrument is brought into contact with one end of the longest diameter of the coarse aggregate, and the coarse aggregate With the other end of the longest diameter in contact with the receiver of the measuring device, the propagation time of the ultrasonic wave in the coarse aggregate is measured. In this measurement method, the work of flattening both ends of the longest diameter of the coarse aggregate is unnecessary, and the work time of the measurement can be greatly shortened as compared with the conventional method.
The number of coarse aggregates used for measurement of ultrasonic propagation time is preferably 10 or more. As shown in FIG. 4, if the number of coarse aggregates measured is 10 or more, the average of the measured values tends to converge to the average of the measured values of the coarse aggregate population.
ここで用いる超音波伝播時間測定器の発信子や受信子の外径は、粗骨材の大きさや、粗骨材の最長径の端部の形状などにもよるが、例えば、粗骨材の最長径の端部が鋭端な場合は、該外径は５０ｍｍ以下が好ましく、２５ｍｍ以下がより好ましく、１５ｍｍ以下が更に好ましい。該外径が５０ｍｍ以上では、超音波伝播時間の測定値の誤差が大きくなる傾向がある。
超音波伝播時間の測定時の温度は、コンクリートが通常置かれる環境温度、例えば、６０℃程度以下なら、該測定値の変動は少なく、特に、制限されることはないが、一般には、１０〜４０℃の範囲が好ましい。
The outer diameter of the transmitter and receiver of the ultrasonic propagation time measuring instrument used here depends on the size of the coarse aggregate and the shape of the end of the longest diameter of the coarse aggregate. When the end of the longest diameter is sharp, the outer diameter is preferably 50 mm or less, more preferably 25 mm or less, and even more preferably 15 mm or less. When the outer diameter is 50 mm or more, there is a tendency that an error in the measured value of the ultrasonic propagation time becomes large.
The temperature at the time of measurement of the ultrasonic propagation time is an environmental temperature at which concrete is usually placed, for example, about 60 ° C. or less. A range of 40 ° C. is preferred.
（Ｂ）該粗骨材の動弾性係数を算出する工程
該工程において、前記（Ａ）工程で得られた超音波伝播時間を用いて、下記（１）式に基づき該粗骨材の動弾性係数を算出する。
Ｅｄ＝（Ｌ／Ｔ）２・ρ ……（１）
（式中、Ｅｄは動弾性係数を表し、Ｌは粗骨材の最長径を表し、Ｔは超音波伝播時間を表し、ρはＪＩＳ Ａ １１１０に準拠して求めた粗骨材の絶乾密度を表す。）
(B) The step of calculating the dynamic elastic modulus of the coarse aggregate In this step, using the ultrasonic wave propagation time obtained in the step (A), the dynamic elasticity of the coarse aggregate based on the following equation (1) Calculate the coefficient.
E d = (L / T) 2 · ρ (1)
(In the formula, E d represents the dynamic elastic modulus, L represents the longest diameter of the coarse aggregate, T represents the ultrasonic wave propagation time, and ρ represents the absolute dryness of the coarse aggregate determined in accordance with JIS A 1110. Represents density)
（２）粗骨材が火成岩または堆積岩である場合の予測方法
該方法は、前記粗骨材が火成岩または堆積岩において、該粗骨材の動弾性係数を用いて、下記（３）式から該粗骨材を含むコンクリートの乾燥収縮ひずみの予測値を算出して予測する方法である。
ｙ＝ａｘ−ｂ ……（３）
（式中、ｙは乾燥期間２６週におけるコンクリートの乾燥収縮ひずみ（×１０−６）を表し、ｘは粗骨材の動弾性係数（ｋＮ／ｍｍ２）を表す。また、ａは、粗骨材が火成岩の場合は１１．５３６、堆積岩の場合は２１．１９５であり、ｂは、粗骨材が火成岩の場合は１２０１．６、堆積岩の場合は１８１２．２である。）
なお、複数個の粗骨材について動弾性係数を求めた場合は、変数ｘは該係数の平均値を用いる。
(2) Prediction method when coarse aggregate is igneous rock or sedimentary rock The method is based on the following equation (3) using the dynamic elastic modulus of the coarse aggregate when the coarse aggregate is an igneous rock or sedimentary rock. This is a method of calculating and predicting a predicted value of drying shrinkage strain of concrete including aggregates.
y = ax−b (3)
(In the formula, y represents the drying shrinkage strain (× 10 −6 ) of the concrete at a drying period of 26 weeks, x represents the kinematic elastic modulus (kN / mm 2 ) of the coarse aggregate, and a is the coarse bone. (If the material is an igneous rock, it is 11.536, if it is a sedimentary rock, 21.195, and b is 1201.6 if the coarse aggregate is an igneous rock, and 1812.2 if it is a sedimentary rock.)
When the kinematic elastic coefficient is obtained for a plurality of coarse aggregates, the variable x uses the average value of the coefficients.
（３）本発明の予測方法の対象となるコンクリートの構成材料
本発明の予測方法の対象となるコンクリートにおいて、使用可能なセメントは、特に限定されず、ポルトランドセメント、混合セメントおよびエコセメントなどが挙げられる。また、前記使用可能な細骨材は、天然砂、砕砂、珪砂および再生砂などが挙げられる。また、前記使用可能な混和材（剤）は、減水剤、ＡＥ剤、フライアッシュ、高炉スラグ、石灰石微粉末などが挙げられる。
(3) Constituent material of concrete subject to prediction method of the present invention In the concrete subject to the prediction method of the present invention, usable cement is not particularly limited, and examples thereof include Portland cement, mixed cement and eco-cement. It is done. Examples of the fine aggregate that can be used include natural sand, crushed sand, silica sand, and regenerated sand. Examples of the usable admixture (agent) include water reducing agents, AE agents, fly ash, blast furnace slag, and fine limestone powder.
以下、本発明を実施例により具体的に説明するが、本発明はこれらの実施例に限定されるものではない。
１．粗骨材の最長径について
最長径が、それぞれ、５ｍｍ以上で１０ｍｍ未満、１０ｍｍ以上で１５ｍｍ未満、および、１５ｍｍ以上である細骨材を用いて、超音波伝播時間を測定し動弾性係数の平均、標準偏差および変動係数を求めた。その結果を表１に示す。
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
1. About the longest diameter of coarse aggregate The longest diameter is 5 mm or more, less than 10 mm, 10 mm or more, less than 15 mm and 15 mm or more. Standard deviation and coefficient of variation were determined. The results are shown in Table 1.
表１に示すように、変動係数は、最長径が１５ｍｍ以上の粗骨材では１５．８であり、５ｍｍ以上で１０ｍｍ未満の粗骨材の４９．０や、１０ｍｍ以上で１５ｍｍ未満の粗骨材の４３．０と比べ、格段に小さくなっている。したがって、最長径が１５ｍｍ以上の粗骨材を超音波伝播時間の測定に用いると、測定誤差は小さくなることが分かる。 As shown in Table 1, the coefficient of variation is 15.8 for coarse aggregate having a longest diameter of 15 mm or more, 49.0 for coarse aggregate of 5 mm or more and less than 10 mm, or coarse bone of 10 mm or more and less than 15 mm. Compared to 43.0 of the material, it is much smaller. Therefore, it can be seen that when a coarse aggregate having a longest diameter of 15 mm or more is used for measuring the ultrasonic propagation time, the measurement error is reduced.
２．粗骨材の測定個数について
粗骨材における超音波伝播時間の測定において、十分に高い精度を得る上で好ましい粗骨材の測定個数を見い出すための試験を行った。その試験方法を以下に示す。
（i）まず、表２に記載の粗骨材Ｎ（堆積岩）の４０個について超音波伝播時間を測定し、４０種の測定値の平均値（ｍ４０）を求めた。
（ii）次に、これらの４０種の測定値から、無作為に３種、５種、１０種、１５種および２０種を抽出して、それぞれの平均値（ｍ３、ｍ５、ｍ１０、ｍ１５およびｍ２０）を求めた。
（iii）さらに、前記（ii）の操作を合計で１０００回繰り返し、得られたｍ３、ｍ５、ｍ１０、ｍ１５およびｍ２０の値（それぞれについて、１０００種の値が存在する。）が、前記ｍ４０±（ｍ４０×１０％）の範囲に含まれる確率（割合）を求めた。
（iv）前記（i）〜（iii）の操作を、表１に記載の粗骨材Ｏ（堆積岩）および粗骨材Ｂ（火成岩）についても行った。これらの結果を図４に示す。
図４から分かるように、粗骨材の測定個数が１０個以上であれば、約９０％以上の確率で、測定値の平均値は前記の範囲に含まれる。したがって、粗骨材の測定個数は、粗骨材の種類によらず、１０個以上が好ましい。
2. Regarding the number of coarse aggregates to be measured In the measurement of the ultrasonic wave propagation time in the coarse aggregates, a test was performed to find the preferred number of coarse aggregates to be measured to obtain sufficiently high accuracy. The test method is shown below.
(I) First, the ultrasonic propagation time was measured for 40 coarse aggregates N (sedimentary rocks) listed in Table 2, and the average value (m 40 ) of 40 types of measured values was obtained.
(Ii) Next, 3 types, 5 types, 10 types, 15 types and 20 types are randomly extracted from these 40 types of measured values, and the average values (m 3 , m 5 , m 10) are respectively extracted. , M 15 and m 20 ).
(Iii) Further, the operation of (ii) is repeated 1000 times in total, and the obtained values of m 3 , m 5 , m 10 , m 15 and m 20 (each has 1000 values). However, the probability (ratio) included in the range of the m 40 ± (m 40 × 10%) was obtained.
(Iv) The operations (i) to (iii) were also performed on the coarse aggregate O (sedimentary rock) and coarse aggregate B (igneous rock) shown in Table 1. These results are shown in FIG.
As can be seen from FIG. 4, when the number of coarse aggregates measured is 10 or more, the average value of the measured values is included in the above range with a probability of about 90% or more. Therefore, the number of coarse aggregates measured is preferably 10 or more regardless of the type of coarse aggregate.
３．粗骨材の絶乾密度と動弾性係数について
表２と表３に示す粗骨材Ａ〜Ｓを用いて、絶乾密度をＪＩＳ Ａ １１１０に準拠して測定し、また、該粗骨材の動弾性係数を、本発明の方法により求めた。その結果を表２と表３に示す。
3. About absolute dry density and dynamic elastic modulus of coarse aggregate Using the coarse aggregates A to S shown in Tables 2 and 3, the absolute dry density was measured in accordance with JIS A 1110. The dynamic elastic modulus was determined by the method of the present invention. The results are shown in Tables 2 and 3.
４．コンクリートの乾燥収縮ひずみの測定
本発明の予測式の予測精度の確認において必要な実測値を得るため、ＪＩＳ Ａ １１２９−２（コンタクトゲージ方法）と附属書Ａ（参考）に準拠して、コンクリートの乾燥収縮ひずみを測定した。
具体的には、表２と表３に示す粗骨材Ａ〜Ｓを用いて、表４に示す配合のコンクリート供試体（１００×１００×４００ｍｍ）を作製した後、該供試体を材齢７日まで、２０℃の水中に浸漬して養生を行った。この養生後、引き続き、供試体を温度２０℃、相対湿度６０％ＲＨの室内に、乾燥期間２６週まで静置して乾燥させた。乾燥後、供試体は、ＪＩＳ Ａ １１２９−２（コンタクトゲージ方法）に準拠して、長さ変化（乾燥収縮ひずみ）を測定した。その結果を表２と表３に示す。
4). Measurement of Drying Shrinkage Strain of Concrete In order to obtain the actual measurement value necessary for confirming the prediction accuracy of the prediction formula of the present invention, in accordance with JIS A 1129-2 (contact gauge method) and Annex A (reference), Dry shrinkage strain was measured.
Specifically, using the coarse aggregates A to S shown in Tables 2 and 3, concrete specimens (100 × 100 × 400 mm) having the composition shown in Table 4 were prepared, and then the specimens were tested with a material age of 7 Until the day, it was cured by dipping in 20 ° C. water. After this curing, the specimen was then allowed to stand in a room at a temperature of 20 ° C. and a relative humidity of 60% RH for a drying period of 26 weeks and dried. After drying, the specimen measured the change in length (dry shrinkage strain) according to JIS A 1129-2 (contact gauge method). The results are shown in Tables 2 and 3.
５．粗骨材の動弾性係数とコンクリートの乾燥収縮ひずみとの関係
表２に記載の数値を用いて、動弾性係数とコンクリートの乾燥収縮ひずみ（実測値）との関係を図５に示す。図５から分かるように、（２）式は粗骨材の種類によらず全部の粗骨材に適用することができ、その決定係数（Ｒ２）は０．６５１３と大きい。また、（３）式は粗骨材が火成岩や堆積岩である場合に適用することができ、その決定係数（Ｒ２）は、火成岩の場合に０．８５８２、堆積岩の場合に０．８６２１と、さらに大きくなっている。したがって、本発明の方法により求めた粗骨材の動弾性係数と、該粗骨材を用いたコンクリートの乾燥収縮ひずみとの間には、明瞭な直線関係が存在していることが分かる。
また、（２）式や（３）式は、コンクリート配合によらず、コンクリートの乾燥収縮ひずみの予測に適用することができる。
5. Relationship between Coarse Elastic Coefficient of Coefficient and Drying Shrinkage Strain of Concrete Using the numerical values shown in Table 2, the relationship between the dynamic elastic modulus and the drying shrinkage strain (actually measured value) of concrete is shown in FIG. As can be seen from FIG. 5, equation (2) can be applied to all coarse aggregates regardless of the type of coarse aggregate, and its coefficient of determination (R 2 ) is as large as 0.6513. Further, the equation (3) can be applied when the coarse aggregate is an igneous rock or a sedimentary rock, and its coefficient of determination (R 2 ) is 0.8582 for an igneous rock, 0.8621 for a sedimentary rock, It is getting bigger. Therefore, it can be seen that there is a clear linear relationship between the dynamic elastic modulus of the coarse aggregate obtained by the method of the present invention and the drying shrinkage strain of the concrete using the coarse aggregate.
Moreover, (2) type | formula and (3) type | formula are applicable to prediction of the drying shrinkage | contraction strain of concrete irrespective of concrete mixing.
６．本発明の予測式の予測精度について
表３に記載の動弾性係数を用いて、本発明の予測式（２）式と（３）式に基づき算出したコンクリートの乾燥収縮ひずみの予測値と、実測値の関係を図６に示す（▲：（２）式に基づき予測値を算出した。□、◇：（３）式に基づき予測値を算出した。）。図６から分かるように、本発明の予測式を用いて算出した予測値は、実測値とよく一致している。したがって、本発明の予測式を用いれば、簡易に精度よく、コンクリートの乾燥収縮ひずみを予測することができる。
6). About the prediction accuracy of the prediction formula of the present invention Using the kinematic elastic coefficient shown in Table 3, the predicted value of the drying shrinkage strain of the concrete calculated based on the prediction formulas (2) and (3) of the present invention, and the actual measurement The relationship between the values is shown in FIG. 6 (▲: the predicted value was calculated based on the formula (2). □, ◇: the predicted value was calculated based on the formula (3)). As can be seen from FIG. 6, the predicted value calculated using the prediction formula of the present invention is in good agreement with the actually measured value. Therefore, if the prediction formula of the present invention is used, the drying shrinkage strain of concrete can be predicted easily and accurately.
１ 発信子
２ 受信子
３ 超音波伝播時間測定器
1
Claims (1)
該粗骨材の動弾性係数の値を用いて、下記（３）式から該粗骨材を含むコンクリートの乾燥収縮ひずみの予測値を算出して予測する、コンクリートの乾燥収縮ひずみを予測する方法。
ｙ＝ａｘ−ｂ ……（３）
（式中、ｙは乾燥期間２６週におけるコンクリートの乾燥収縮ひずみ（×１０ −６ ）を、ｘは粗骨材の動弾性係数（ｋＮ／ｍｍ ２ ）を表す。また、ａは、粗骨材が火成岩の場合は１１．５３６、堆積岩の場合は２１．１９５であり、ｂは、粗骨材が火成岩の場合は１２０１．６、堆積岩の場合は１８１２．２である。）
（Ａ）最長径が１５ｍｍ以上の粗骨材の最長径の一端に、超音波伝播時間測定器の発信子を接触させるとともに、該粗骨材の最長径の他端に、該測定器の受信子を接触させた状態で、該粗骨材における超音波の伝播時間を測定する工程
（Ｂ）前記（Ａ）工程で得られた超音波伝播時間の値を用いて、下記（１）式に基づき該粗骨材の動弾性係数を算出する工程
Ｅｄ＝（Ｌ／Ｔ）２・ρ ……（１）
（式中、Ｅｄは動弾性係数を表し、Ｌは粗骨材の最長径を表し、Ｔは超音波伝播時間を表し、ρはＪＩＳ Ａ １１１０に準拠して求めた粗骨材の絶乾密度を表す。）
Comprising the following a step (A) and (B) step at least, the dynamic elastic modulus was determined using a method for determining the dynamic elastic modulus of the coarse aggregate is igneous rocks 33.7~56.3kN / mm 2 or said, A method for predicting drying shrinkage strain of concrete including coarse aggregate which is a sedimentary rock having a kinematic elastic modulus of 37.9 to 62.3 kN / mm 2 ,
A method for predicting dry shrinkage strain of concrete by calculating a predicted value of dry shrinkage strain of concrete containing the coarse aggregate from the following equation (3) using the value of the dynamic elastic modulus of the coarse aggregate .
y = ax−b (3)
(In the formula, y represents the drying shrinkage strain (× 10 −6 ) of concrete at a drying period of 26 weeks , x represents the kinematic elastic modulus (kN / mm 2 ) of the coarse aggregate, and a represents the coarse aggregate. Is 11.536 for igneous rocks, 21.195 for sedimentary rocks, b is 1201.6 for coarse aggregates igneous rocks, and 1812.2 for sedimentary rocks.)
(A) The transmitter of the ultrasonic propagation time measuring instrument is brought into contact with one end of the longest diameter of the coarse aggregate having a longest diameter of 15 mm or more, and the other end of the longest diameter of the coarse aggregate is received by the measuring instrument. The step of measuring the ultrasonic wave propagation time in the coarse aggregate with the child in contact (B) Using the value of the ultrasonic wave propagation time obtained in the step (A), the following equation (1) Step of calculating the kinematic elastic coefficient of the coarse aggregate based on E d = (L / T) 2 · ρ (1)
(In the formula, E d represents the dynamic elastic modulus, L represents the longest diameter of the coarse aggregate, T represents the ultrasonic wave propagation time, and ρ represents the absolute dryness of the coarse aggregate determined in accordance with JIS A 1110. Represents density)
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