JP6430745B2 - Method for determining the effectiveness of shrinkage reducing materials - Google Patents
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- 239000000463 material Substances 0.000 title claims description 63
- 230000001603 reducing effect Effects 0.000 title claims description 21
- 238000000034 method Methods 0.000 title claims description 19
- 239000004567 concrete Substances 0.000 claims description 102
- 238000012937 correction Methods 0.000 claims description 49
- 238000001035 drying Methods 0.000 claims description 44
- 239000003638 chemical reducing agent Substances 0.000 claims description 24
- 238000004364 calculation method Methods 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 2
- 230000000694 effects Effects 0.000 description 15
- 230000009467 reduction Effects 0.000 description 14
- 238000012360 testing method Methods 0.000 description 9
- 238000005336 cracking Methods 0.000 description 8
- 239000003795 chemical substances by application Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 238000013461 design Methods 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 230000003014 reinforcing effect Effects 0.000 description 3
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000004568 cement Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 229910001653 ettringite Inorganic materials 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000011150 reinforced concrete Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229920006267 polyester film Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 230000002040 relaxant effect Effects 0.000 description 1
- 230000036962 time dependent Effects 0.000 description 1
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- Curing Cements, Concrete, And Artificial Stone (AREA)
Description
本発明は、コンクリートの乾燥収縮ひび割れの制御において、収縮低減材料の有効性を判定するための方法に関する。 The present invention relates to a method for determining the effectiveness of shrinkage reducing materials in the control of dry shrinkage cracks in concrete.
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。この収縮ひび割れは、コンクリート構造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等の、構造物の耐久性低下の原因になる。したがって、コンクリートの耐久性を確保するには、この収縮ひび割れを制御する必要がある。 Since concrete has low tensile strength, cracks (shrinkage cracks) may occur due to shrinkage of the concrete. These shrinkage cracks not only detract from the aesthetics of the concrete structure, but also cause deterioration in the durability of the structure, such as deterioration of the water and air tightness of the concrete and corrosion of reinforcing bars. Therefore, in order to ensure the durability of concrete, it is necessary to control this shrinkage crack.
従来、収縮ひび割れの制御には、膨張材および収縮低減剤（以下「収縮低減材料」という。）が用いられてきた。そして、膨張材は石灰系およびエトリンガイト系があり、水和によりそれぞれ水酸化カルシウムおよびエトリンガイトの結晶が生成して、コンクリート中の空隙を埋めるとともに、初期の材齢における膨張により収縮を低減（補償）する。また、収縮低減剤は主にグリコールエーテル系とポリカルボン酸エーテル系があり、いずれもコンクリート中の水の表面張力を低下させて、乾燥収縮の主因である毛細管張力の緩和により収縮を低減する。これらの材料は、前記のように作用機序が異なるため、ひび割れ低減の目的や程度に応じて選定され、単独で使用または併用されている。
しかし、前記収縮低減材料の有効性を判定することは難しく、とりわけ、収縮低減材料によるひび割れ低減効果を定量的に評価（予測）する方法は知られていない。
Conventionally, an expansion material and a shrinkage reducing agent (hereinafter referred to as “shrinkage reducing material”) have been used to control shrinkage cracks. In addition, there are lime-based and ettringite-based expansion materials, and calcium hydroxide and ettringite crystals are formed by hydration to fill the voids in the concrete, and shrinkage is reduced by expansion at the early age (compensation). To do. Further, the shrinkage reducing agents mainly include glycol ether type and polycarboxylic acid ether type, both of which reduce the surface tension of water in the concrete and reduce the shrinkage by relaxing the capillary tension which is the main cause of drying shrinkage. Since these materials have different mechanisms of action as described above, they are selected according to the purpose and degree of crack reduction and are used alone or in combination.
However, it is difficult to determine the effectiveness of the shrinkage reducing material, and in particular, a method for quantitatively evaluating (predicting) the crack reducing effect of the shrinkage reducing material is not known.
そこで、本発明者らは、先に、収縮低減材料によるひび割れ低減効果の定量的評価方法等を提案した（特許文献１）。該方法は、無拘束の普通コンクリートの乾燥収縮ひずみ値と拘束された同一配合の普通コンクリートのひび割れ特性値から求めた回帰直線上の点であって、低収縮コンクリートのひび割れ特性値を示す点が指す乾燥収縮ひずみ値（ε）と、普通コンクリートの乾燥収縮ひずみ値（ε０）との差（ε０−ε）を指標に用いて、ひび割れ低減効果を評価する点に特徴がある。 Therefore, the present inventors have previously proposed a method for quantitatively evaluating the crack reduction effect of the shrinkage reducing material (Patent Document 1). The method is a point on the regression line obtained from the drying shrinkage strain value of unconstrained ordinary concrete and the cracking property value of constrained ordinary concrete, and shows the cracking property value of low shrinkage concrete. It is characterized in that the crack reduction effect is evaluated using the difference (ε 0 −ε) between the dry shrinkage strain value (ε) and the dry shrinkage strain value (ε 0 ) of ordinary concrete as an index.
そして、本発明は、ひび割れ低減効果の評価における前記指標の利点を活用したもので、収縮低減材料の使用によりコンクリートのひび割れを、予め設定した目標を満足するまでに低減できるか否か判定できる、収縮低減材料の有効性判定方法を提供することを目的にする。 And, the present invention utilizes the advantage of the index in the evaluation of the crack reduction effect, it can be determined whether or not the crack of the concrete can be reduced by using the shrinkage reduction material until the preset target is satisfied, An object of the present invention is to provide a method for determining the effectiveness of a shrinkage reducing material.
そこで、本発明者は、後掲の図３〜５に示す関係から特定の式（下記（１）〜（３）式）を導出し、該式を用いて収縮低減材料のひび割れ低減効果を乾燥収縮ひずみで表わし、該ひずみと修正ベース・マレー式（下記（４）〜（７）式）を用いてコンクリートのひび割れ本数等を算出し、該算出値に基づき、ひび割れの低減における収縮低減材料の有効性を判定できることを見い出し、本発明を完成させた。
すなわち、本発明は、以下の構成を有するものである。
Therefore, the present inventor derives a specific formula (the following formulas (1) to (3)) from the relationships shown in FIGS. 3 to 5 below, and uses the formula to dry the crack reduction effect of the shrinkage reducing material. It is expressed by shrinkage strain, and the number of cracks of concrete is calculated using the strain and the modified base Murray formula (the following formulas (4) to (7)). Based on the calculated value, the shrinkage reduction material in reducing cracks is calculated. The inventors have found that the effectiveness can be judged and completed the present invention.
That is, the present invention has the following configuration.
［１］下記（Ａ）〜（Ｃ）の工程を経て得た、下記ひび割れ本数および／またはひび割れ幅の目標値と、下記ひび割れ本数および／またはひび割れ幅の算出値とを比較して、該算出値が該目標値を満足すれば、収縮低減材料のコンクリートへの使用を有効と判定する、収縮低減材料の有効性判定方法であって、
下記補正係数（ｐ １ ）は０．８２〜０．８７、下記記補正係数（ｐ ２ ）は０．８２〜０．８６、下記補正係数（ｐ ３ ）は０．６４〜０．７２、下記補正値（ｑ １ ）は９０×１０ −６ 〜１９０×１０ −６ 、および下記補正値（ｑ ２ ）は５０×１０ −６ 〜２１０×１０ −６ の範囲内において選択される、収縮低減材料の有効性判定方法。
（Ａ）予めコンクリートのひび割れ本数および／またはひび割れ幅の目標値を設定する、ひび割れ目標値設定工程
（Ｂ）下記（１）〜（３）式のいずれかを用いて乾燥収縮ひずみを算出する、乾燥収縮ひずみ算出工程
（１）膨張材を用いる場合：
乾燥収縮ひずみ＝プレーンコンクリートの乾燥収縮ひずみ×補正係数（ｐ１）−補正値（ｑ１） ・・・（１）
（２）収縮低減剤を用いる場合：
乾燥収縮ひずみ＝プレーンコンクリートの乾燥収縮ひずみ×補正係数（ｐ２） ・・・（２）
（３）膨張材と収縮低減剤を併用する場合：
乾燥収縮ひずみ＝プレーンコンクリートの乾燥収縮ひずみ×補正係数（ｐ３）−補正値（ｑ２） ・・・（３）
（Ｃ）前記乾燥収縮ひずみと下記（４）〜（７）式を用いて、コンクリートのひび割れ本数および／またはひび割れ幅を算出する、ひび割れ特性値算出工程
The following correction coefficient (p 1 ) is 0.82 to 0.87, the following correction coefficient (p 2 ) is 0.82 to 0.86, the following correction coefficient (p 3 ) is 0.64 to 0.72, and The shrinkage-reducing material, wherein the correction value (q 1 ) is selected within the range of 90 × 10 −6 to 190 × 10 −6 , and the following correction value (q 2 ) is selected within the range of 50 × 10 −6 to 210 × 10 −6. Effectiveness judgment method.
(A) A crack target value setting step in which a target value of the number of cracks and / or crack width of concrete is set in advance. (B) Dry shrinkage strain is calculated using any of the following formulas (1) to (3). Drying shrinkage calculation process (1) When using an expansion material:
Drying shrinkage strain = drying shrinkage strain of plain concrete × correction coefficient (p 1 ) −correction value (q 1 ) (1)
(2) When using a shrinkage reducing agent:
Drying shrinkage strain = Drying shrinkage strain of plain concrete x Correction factor (p 2 ) (2)
(3) When using an expansion material and a shrinkage reducing agent in combination:
Drying shrinkage strain = drying shrinkage strain of plain concrete × correction coefficient (p 3 ) −correction value (q 2 ) (3)
(C) Crack characteristic value calculation step of calculating the number of cracks and / or crack width of concrete using the drying shrinkage strain and the following formulas (4) to (7)
[３]前記補正係数（ｐ１）が０．８７、前記補正係数（ｐ２）が０．８６、前記補正係数（ｐ３）が０．７２、前記補正値（ｑ１）が９０×１０−６、および前記補正値（ｑ２）が５０×１０−６ある、前記[１]または［２］に記載の収縮低減材料の有効性判定方法。
[3] The correction coefficient (p 1 ) is 0.87, the correction coefficient (p 2 ) is 0.86, the correction coefficient (p 3 ) is 0.72, and the correction value (q 1 ) is 90 × 10. −6 , and the correction value (q 2 ) is 50 × 10 −6 . The method for determining the effectiveness of the shrinkage-reducing material according to [1] or [2].
本発明の収縮低減材料の有効性判定方法によれば、収縮低減材料の使用によりコンクリートのひび割れを、予め設定した目標を満足するまでに低減できるか否か判定することができる。 According to the method for determining the effectiveness of the shrinkage reducing material of the present invention, it is possible to determine whether or not the cracks in the concrete can be reduced by satisfying a preset target by using the shrinkage reducing material.
本発明は、前記のとおり、（Ａ）ひび割れ目標値設定工程、（Ｂ）乾燥収縮ひずみ算出工程、および（Ｃ）ひび割れ特性値算出工程を含む、収縮低減材料の有効性判定方法である。以下、本発明について各工程に分け詳細に説明する。 As described above, the present invention is a method for determining the effectiveness of a shrinkage reducing material, which includes (A) a crack target value setting step, (B) a drying shrinkage strain calculation step, and (C) a crack characteristic value calculation step. Hereinafter, the present invention will be described in detail for each step.
（Ａ）ひび割れ目標値設定工程
該工程は、コンクリート構造物に要求される耐久性に基づき、予めコンクリートのひび割れ本数および／またはひび割れ幅の目標値を設定する工程である。
例えば、ひび割れ幅の標準的な設計値は、「鉄筋コンクリート造建築物の収縮ひび割れ制御設計・施工指針（案）・同解説」（日本建築学会 発行）では、外壁の漏水抵抗性を確保するための値として０．１ｍｍ以下、劣化抵抗性を確保するための値として屋外で０．２ｍｍ以下、屋内では０．３ｍｍ以下としている。本工程では、これらの値やコンクリート構造物の周囲の環境等を考慮して、前記ひび割れ本数および／またはひび割れ幅の目標値を設定するとよい。
(A) Crack target value setting step This step is a step of setting a target value of the number of cracks and / or crack width of concrete in advance based on the durability required for the concrete structure.
For example, the standard design value for the crack width is “Shrinkage crack control design / construction guidelines (draft) / commentary explanation for reinforced concrete buildings” (published by the Architectural Institute of Japan). The value is 0.1 mm or less, the value for ensuring deterioration resistance is 0.2 mm or less outdoors and 0.3 mm or less indoors. In this step, the target value of the number of cracks and / or the crack width may be set in consideration of these values and the environment surrounding the concrete structure.
（Ｂ）乾燥収縮ひずみ算出工程
該工程は、膨張材の有効性を判定する場合は前記（１）式を用い、収縮低減剤の有効性を判定する場合は前記（２）式を用い、膨張材および収縮低減剤を併用した場合の有効性を判定する場合は前記（３）式を用いて、乾燥収縮ひずみを算出する工程である。
次に、図３〜５を用いて前記（１）〜（３）式の導出方法を説明する。
(B) Drying Shrinkage Strain Calculation Step In this step, the above formula (1) is used when determining the effectiveness of the expansion material, and the above formula (2) is used when determining the effectiveness of the shrinkage reducing agent. When determining the effectiveness when the material and the shrinkage reducing agent are used in combination, it is a step of calculating the drying shrinkage strain using the above equation (3).
Next, a method for deriving the equations (1) to (3) will be described with reference to FIGS.
（i）図３〜５の説明
図３〜５の上側の直線は、無拘束のプレーンコンクリートの乾燥収縮ひずみの値（横軸）と、該プレーンコンクリートと同一配合の、拘束されたプレーンコンクリートのひび割れ係数の値（縦軸）を座標とするプロット（ＰＬ１〜ＰＬ３、各ＰＬあたりｎ＝２）、および、無拘束の収縮低減剤含有コンクリートの乾燥収縮ひずみの値（横軸）と、該収縮低減剤含有コンクリートと同一配合の、拘束された収縮低減剤含有コンクリートのひび割れ係数の値（縦軸）を座標とするプロット（ＳＲ１〜ＳＲ３、各ＳＲあたりｎ＝２）の合計１２個のプロットから求めた回帰直線である。
また、図３〜５の下側の直線は、無拘束の膨張材含有コンクリートの乾燥収縮ひずみの値（横軸）と、該膨張材含有コンクリートと同一配合の、拘束された膨張材含有コンクリートのひび割れ係数の値（縦軸）を座標とするプロット（ＥＸ１〜ＥＸ３、各ＥＸあたりｎ＝２）、および、無拘束の膨張材および収縮低減剤含有コンクリートの乾燥収縮ひずみの値（横軸）と、該膨張材および収縮低減剤含有コンクリートと同一配合の、拘束された膨張材および収縮低減剤含有コンクリートのひび割れ係数の値（縦軸）を座標とするプロット（ＥＸＳＲ１〜ＥＸＳＲ３、各ＥＸＳＲあたりｎ＝２）の合計１２個のプロットから求めた回帰直線である。
なお、拘束されたコンクリート試験体を図１に示す。
(I) Description of FIGS. 3 to 5 The upper straight line in FIGS. 3 to 5 shows the value of the drying shrinkage strain of the unconstrained plain concrete (horizontal axis) and the constrained plain concrete of the same composition as the plain concrete. A plot (PL1 to PL3, n = 2 for each PL) with the crack coefficient value (vertical axis) as coordinates, the value of the drying shrinkage strain of the unconstrained shrinkage reducing agent-containing concrete (horizontal axis), and the shrinkage From a total of 12 plots of plots (SR1 to SR3, n = 2 for each SR) whose coordinates are the cracking coefficient values (vertical axis) of constrained shrinkage reducing agent-containing concrete of the same composition as the reducing agent-containing concrete It is the obtained regression line.
Moreover, the lower straight line in FIGS. 3 to 5 shows the value of the drying shrinkage strain (horizontal axis) of the unconstrained expansive material-containing concrete and the constrained expansive material-containing concrete having the same composition as the expansive material-containing concrete. Plot (EX1 to EX3, n = 2 for each EX) with the crack coefficient value (vertical axis) as coordinates, and the value (horizontal axis) of drying shrinkage strain of unconstrained expansion material and shrinkage reducing agent-containing concrete , Plots (EXSR1 to EXSR3, n = EXSR for each EXSR) with the same value as the cracking coefficient (vertical axis) of the constrained expansion material and the shrinkage reduction agent-containing concrete of the same composition as the expansion material and the shrinkage reduction agent-containing concrete It is a regression line obtained from a total of 12 plots of 2).
The constrained concrete specimen is shown in FIG.
前記無拘束の全種類のコンクリートの乾燥収縮ひずみは、ＪＩＳ Ａ １１２９に準じて測定するか、または、「鉄筋コンクリート造建築物の収縮ひび割れ制御設計・施工指針（案）・同解説」の５ページに記載の（３．１）式を用いて算出するとよい。
なお、前記全種類のコンクリートとは、プレーンコンクリート、膨張材含有コンクリート、収縮低減剤含有コンクリート、および、膨張材および収縮低減剤含有コンクリートをいう。
The dry shrinkage strains of all types of unconstrained concrete are measured according to JIS A 1129, or on page 5 of “Control design for shrinkage cracks in reinforced concrete buildings, construction guidelines (draft), and explanation”. It is good to calculate using (3.1) Formula of description.
The all types of concrete refer to plain concrete, expansion material-containing concrete, shrinkage reducing agent-containing concrete, and expansion material and shrinkage reduction agent-containing concrete.
また、前記拘束された全種類のコンクリートのひび割れ係数とは、ひび割れの観測区間の距離に対するひび割れ幅の合計をいう。該ひび割れ幅は、例えば、図２のＰＬ１の（i）に示す、拘束されてひび割れが発生した試験体の中央部（ｂ）のひび割れ幅、および両側面から約１５ｍｍ内側（ａおよびｃ）の各ひび割れ幅の合計３点のひび割れ幅（上面および下面の両面で測れば合計６点）をクラックスケールで測定してその平均値で表わす。
前記ひび割れ幅の平均値は、例えば、図２のＰＬ１の（i）を用いて説明すると、最上位のひび割れでは０．２３である。そして、コンクリートのひび割れ係数は、ＰＬ１の（i）では９８０×１０−６（＝（０．２３＋０．２９＋０．２８＋０．１８）／１０００）、さらに、ＰＬ１の（ii）では９３０×１０−６（＝（０．１０＋０．２７＋０．２４＋０．１８＋０．１４）／１０００）となる。そして、これらの値は、それぞれ、図３のＰＬ１の上の白菱形と下の白菱形のプロットが示すひび割れ係数の値である。
In addition, the crack coefficient of all types of constrained concrete means the total crack width with respect to the distance of the crack observation section. The crack width is, for example, the crack width of the central part (b) of the test body where cracks are generated as shown in (i) of PL1 in FIG. 2, and about 15 mm inside (a and c) from both sides. The crack width of a total of three points of each crack width (a total of six points when measured on both the upper and lower surfaces) is measured with a crack scale and expressed as an average value.
The average value of the crack width is 0.23 for the uppermost crack, for example, using (i) of PL1 in FIG. The crack coefficient of concrete is 980 × 10 −6 (= (0.23 + 0.29 + 0.28 + 0.18) / 1000) for PL1 (i), and 930 × 10 −6 (PL) for (ii). = (0.10 + 0.27 + 0.24 + 0.18 + 0.14) / 1000). These values are the crack coefficient values indicated by the plots of the upper white rhombus and the lower white rhombus on PL1 in FIG.
（ii）（１）〜（３）式の導出
膨張材含有コンクリートの乾燥収縮ひずみは、通常、ＪＩＳ Ａ １１２９に準じて測定する。そして、この方法では、材齢７日を経過した後に、試験体（供試体）の長さの測定が始まるが、この７日の間に、膨張材含有コンクリート特有の収縮低減作用である材齢初期の膨張は終了しているため、該初期膨張による乾燥収縮ひずみの低減効果を把握して評価することはできない。かかる問題を解消するため、本発明における（１）式は、該初期膨張による低減効果を含めて乾燥収縮ひずみの低減効果を表す式である。すなわち、（１）式は、図３に示すＰＬの乾燥収縮ひずみ（εＰＬ）とＥＸの乾燥収縮ひずみ（εＥＸ）の差（△εＥＸ）を、膨張材による乾燥収縮ひずみの低減効果によるものと捉え、また、ＥＸから横軸に平行に線分を引いて、上の回帰直線との交点が示す乾燥収縮ひずみ（εＣ）とＥＸの乾燥収縮ひずみ（εＥＸ）の差（△εＣ）を、材齢初期におけるコンクリートの膨張による乾燥収縮ひずみの低減効果（収縮補償の効果）によるものとみなす。
そうすると、前記各乾燥収縮ひずみには以下の式が成り立つ。
εＰＬ＝εＣ＋△εＥＸ＋△εＣ
そうすると、前記収縮補償による効果を加味して修正された膨張材含有コンクリートの乾燥収縮ひずみεＣは、
εＣ＝（εＰＬ−△εＥＸ）−△εＣ ・・・（８）
ここで、εＥＸの測定を不要にしてεＣを算出する作業を簡易にするため、（８）式において（εＰＬ−△εＥＸ）＝εＰＬ×ｐ１とおき、また、△εＣ＝ｑ１とおくと、（１）式と同じ下記（９）式が得られる。
εＣ＝εＰＬ×ｐ１−ｑ１ ・・・（９）
(Ii) Derivation of Equations (1) to (3) The drying shrinkage strain of the expansive material-containing concrete is usually measured according to JIS A 1129. In this method, the measurement of the length of the specimen (specimen) starts after the age of 7 days has elapsed. During this 7 days, the age of the shrinkage-reducing action peculiar to the expanded material-containing concrete is exhibited. Since the initial expansion has been completed, the effect of reducing the drying shrinkage strain due to the initial expansion cannot be grasped and evaluated. In order to solve such a problem, the expression (1) in the present invention is an expression representing a drying shrinkage reduction effect including the reduction effect due to the initial expansion. That is, the equation (1) represents the difference (Δε EX ) between the drying shrinkage strain (ε PL ) of PL and the drying shrinkage strain (ε EX ) of EX shown in FIG. In addition, a line segment is drawn parallel to the horizontal axis from EX, and the difference between the drying shrinkage strain (ε C ) and the drying shrinkage strain (ε EX ) indicated by the intersection with the above regression line (Δε) C ) is considered to be due to the effect of reducing the drying shrinkage strain (the effect of shrinkage compensation) due to the expansion of the concrete in the early age.
Then, the following formula is established for each of the drying shrinkage strains.
ε PL = ε C + Δε EX + Δε C
Then, the drying shrinkage strain ε C of the expanded material-containing concrete modified in consideration of the effect of the shrinkage compensation,
ε C = (ε PL −Δε EX ) −Δε C (8)
Here, in order to simplify the work of calculating ε C without the need to measure ε EX , (ε PL −Δε EX ) = ε PL × p 1 is set in equation (8), and Δε C When q = 1 , the following equation (9) that is the same as equation (1) is obtained.
ε C = ε PL × p 1 −q 1 (9)
また、図４に示すように、収縮低減剤含有コンクリートでは、材齢初期の膨張はないから（すなわち、△εＣはゼロ）、ＳＲのプロットはＰＬのプロットと同じ直線上に並ぶ。したがって、（８）式において△εＥＸを△εＳＲに置き換えて（εＰＬ−△εＳＲ）＝εＰＬ×ｐ２、および△εＣ＝０とおくと、（２）式と同じ下記（１０）式が得られる。ただし、△εＳＲ＝εＰＬ−εＳＲである。
εＣ＝εＰＬ×ｐ２ ・・・（１０）
Further, as shown in FIG. 4, in the shrinkage-reducing agent-containing concrete, since there is no expansion in the early age (that is, Δε C is zero), the SR plot is arranged on the same straight line as the PL plot. Therefore, when Δε EX is replaced by Δε SR in equation (8) and (ε PL −Δε SR ) = ε PL × p 2 and Δε C = 0, the same as equation (2) below ( 10) Equation is obtained. However, it is △ ε SR = ε PL -ε SR .
ε C = ε PL × p 2 (10)
また、図５に示すように、ＥＸＳＲのプロットはＥＸのプロットと同じ直線上に並ぶことから、膨張材および収縮低減剤含有コンクリートの材齢初期の膨張による乾燥収縮ひずみの低減効果は、膨張材含有コンクリートの該効果と同じである。
また、図５に示すように、膨張材および収縮低減剤含有コンクリートの乾燥収縮ひずみの低減効果は、膨張材含有コンクリートおよび収縮低減剤含有コンクリートのそれぞれの効果の和{（１−ｐ１）＋（１−ｐ２）}で近似することができる。したがって、ｐ３≒〔１−{（１−ｐ１）＋（１−ｐ２）}〕となる。
そして、（８）式において△εＥＸを△εＥＸＳＲに置き換えて（εＰＬ−△εＥＸＳＲ）＝εＰＬ×ｐ３、および△εＣ＝ｑ２とおくと、（３）式と同じ下記（１１）式が得られる。ただし、△εＥＸＳＲ＝εＰＬ−εＥＸＳＲである。
εＣ＝εＰＬ×ｐ３−ｑ２ ・・・（１１）
In addition, as shown in FIG. 5, the EXSR plots are arranged on the same straight line as the EX plot. Therefore, the effect of reducing the drying shrinkage strain due to the expansion of the expansion material and the shrinkage-reducing agent-containing concrete at the early age is the expansion material. It is the same as the effect of the contained concrete.
Further, as shown in FIG. 5, the effect of reducing the drying shrinkage strain of the expansion material and the shrinkage reducing agent-containing concrete is the sum of the effects of the expansion material-containing concrete and the shrinkage reduction agent-containing concrete {(1-p 1 ) + (1-p 2 )} can be approximated. Therefore, p 3 ≈ [1-{(1-p 1 ) + (1-p 2 )}].
Then, in the equation (8), when Δε EX is replaced by Δε EXSR and (ε PL −Δε EXSR ) = ε PL × p 3 and Δε C = q 2 , the same as the equation (3) Equation (11) is obtained. However, it is △ ε EXSR = ε PL -ε EXSR .
ε C = ε PL × p 3 -q 2 (11)
次に、図３〜５に示すプロットの値（εＰＬ、εＥＸ、εＣ、εＳＲ、およびεＥＸＳＲ）と（９）〜（１１）式に基づき、（１）〜（３）式の補正係数（ｐ１、ｐ２、およびｐ３）と補正値（ｐ１、、ｐ２、およびｐ３）を求めた結果を表１に示す。表１に示すように、ｐ１は０．８２〜０．８７、ｐ２は０．８２〜０．８６、ｐ３は０．６４〜０．７２、ｑ１は９０×１０−６〜１９０×１０−６、およびｑ２は５０×１０−６〜２１０×１０−６が得られる。
さらに、乾燥収縮ひずみでは、安全側を見据えた評価（すなわち、本発明では補正係数をより大きく見積もり、補正値はより小さく見積もること）が求められるから、該評価に従い、前記の数値範囲において、ｐ１〜ｐ３は最大値、ｑ１およびｑ２は最小値を選択すると、ｐ１は０．８７、ｐ２は０．８６、ｐ３は０．７２、ｑ１は９０×１０−６、およびｑ２は５０×１０−６となる。
Next, based on the values (ε PL , ε EX , ε C , ε SR , and ε EXSR ) of the plots shown in FIGS. 3 to 5 and the equations (9) to (11), the equations (1) to (3) Table 1 shows the results of obtaining correction coefficients (p 1 , p 2 , and p 3 ) and correction values (p 1 , p 2 , and p 3 ). As shown in Table 1, p 1 is 0.82 to .87, p 2 is .82-.86, p 3 is 0.64-0.72, q 1 is 90 × 10 -6 to 190 × 10 −6 and q 2 are 50 × 10 −6 to 210 × 10 −6 .
Furthermore, since the drying shrinkage strain requires an evaluation with a focus on the safe side (that is, in the present invention, the correction coefficient is estimated to be larger and the correction value is estimated to be smaller). 1 to p 3 are maximum values, q 1 and q 2 are selected as minimum values, p 1 is 0.87, p 2 is 0.86, p 3 is 0.72, q 1 is 90 × 10 −6 , and q 2 is a 50 × 10 -6.
以下、本発明を実施例により説明するが、本発明はこれらの実施例に限定されない。
１．コンクリート試験体の作製
表２に示す材料を用いて、表３に示す配合のコンクリートを、２０℃、相対湿度８０％の室内で混練して、プレーンコンクリート（ＰＬ１〜３）、膨張材含有コンクリート（ＥＸ１〜３）、収縮低減剤含有コンクリート（ＳＲ１〜３）、膨張材および収縮低減剤含有コンクリート（ＥＸＳＲ１〜３）の拘束されたコンクリート試験体（図１に示す。）を、各コンクリートにつき２体ずつ合計２４体作製した。また、前記コンクリート（ＰＬ１〜３、ＥＸ１〜３、ＳＲ１〜３、ＥＸＳＲ１〜３）の無拘束のコンクリート試験体（１００×１００×４００ｍｍの試験体の中心部に埋込型ひずみ計を設置）を２体ずつ合計２４体作製した。
なお、各コンクリートのスランプは１８±２．５ｃｍ、空気量は４．５±１．５％になるように、高性能ＡＥ減水剤を用いて調整した。また、コンクリートの養生条件は、コンクリートの仕上げ面をポリエステルフィルムで被覆し、その上を湿布で覆った状態にして２０℃で材齢７日まで湿潤養生した後、２０℃、相対湿度６０％の室内に静置した。
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
1. Preparation of Concrete Specimen Using the materials shown in Table 2, the concretes shown in Table 3 were kneaded in a room at 20 ° C. and a relative humidity of 80% to obtain plain concrete (PL1 to PL3), expanded material-containing concrete ( EX1-3), concrete specimens containing shrinkage-reducing agent (SR1-3), and concrete specimens (shown in FIG. 1) restrained by expansion material and shrinkage-reducing agent-containing concrete (EXSR1-3) for each concrete. A total of 24 bodies were produced one by one. In addition, an unconstrained concrete specimen (an embedded strain gauge is installed at the center of a 100 × 100 × 400 mm specimen) of the concrete (PL1-3, EX1-3, SR1-3, EXSR1-3). A total of 24 bodies were produced by two bodies.
In addition, it adjusted using the high performance AE water reducing agent so that the slump of each concrete might be 18 +/- 2.5cm and an air amount might be 4.5 +/- 1.5%. The concrete curing conditions were as follows: the concrete finished surface was covered with a polyester film, covered with a compress, wet-cured at 20 ° C. until the age of 7 days, then 20 ° C. and 60% relative humidity. I left it indoors.
２．乾燥収縮ひずみとひび割れ幅の測定
無拘束の前記全種類のコンクリート試験体の乾燥収縮ひずみは、ＪＩＳ Ａ １１２９に準じて測定した。
また、拘束された前記全種類のコンクリート試験体は、図１に示すとおり、ひび割れの観測区間をＪＩＳ Ａ １１５１に規定する試験体の３００ｍｍから１０００ｍｍに延長するとともに、コンクリート内部に、鉄筋比が０．５％となるように異形鉄筋Ｄ１０を埋設したものである。また、該試験体はひび割れの性状を把握し易くするために拘束鋼材の断面積を大きくし、ＪＩＳ Ａ １１５１に規定する拘束鋼材比を約８％から３８．５％に変更して拘束度を高めたものである。そして、埋込型ひずみ計により無拘束の前記全種類のコンクリート試験体の乾燥収縮ひずみの経時変化を測定するとともに、乾燥材齢１８２日の拘束された前記全種類のコンクリート試験体のひび割れ幅を測定し、該ひび割れ幅からひび割れ係数（ひび割れ幅の合計（ｍｍ）／１０００（ｍｍ））を算出した。
なお、ひび割れ幅は、図２のＰＬ１の(i）に示すように、拘束されてひび割れが発生したコンクリート試験体の中央部（ｂ）のひび割れ幅、および両側面から約１５ｍｍ内側（ａおよびｃ）のひび割れ幅の合計３カ所のひび割れ幅（上面および下面の両面で測った合計６カ所）をクラックスケールで測定してその平均値を求めた。
拘束されたコンクリート試験体のひび割れ状況を図２に示し、乾燥材齢１８２日における無拘束のコンクリート試験体の乾燥収縮ひずみとひび割れ係数との関係を図３に示す。
2. Measurement of drying shrinkage strain and crack width The drying shrinkage strain of all the unconstrained concrete specimens was measured according to JIS A1129.
In addition, as shown in FIG. 1, the constrained all types of concrete specimens extend the crack observation section from 300 mm to 1000 mm of the specimen specified in JIS A 1151, and have a rebar ratio of 0 inside the concrete. The deformed rebar D10 is embedded so as to be 5%. In addition, in order to make it easier to grasp the properties of cracks, the test specimen increases the cross-sectional area of the restraint steel material, and the restraint steel material ratio specified in JIS A 1151 is changed from about 8% to 38.5%. It is an enhanced one. And while measuring the time-dependent change of the drying shrinkage strain of the all types of concrete specimens unconstrained by an embedded strain gauge, the crack width of all types of concrete specimens restrained by the dry material age of 182 days was measured. The crack coefficient (total crack width (mm) / 1000 (mm)) was calculated from the crack width.
In addition, as shown to (i) of PL1 of FIG. 2, the crack width is about 15 mm inside (a and c) from the crack width of the center part (b) of the concrete test body which was restrained and the crack generate | occur | produced. ) Crack widths at a total of three places (total of six places measured on both the upper and lower surfaces) were measured with a crack scale, and the average value was obtained.
FIG. 2 shows the cracking situation of the constrained concrete specimen, and FIG. 3 shows the relationship between the drying shrinkage strain and the cracking coefficient of the unconstrained concrete specimen at the dry material age of 182 days.
３．収縮低減材料の有効性の判定
表２に示すセメント、細骨材、および粗骨材を用いて、単位水量が１７５ｋｇ／ｍ３、水セメント比が５０％のプレーンコンクリートを製造し、ＪＩＳ Ａ １１２９に準じて該コンクリートの乾燥収縮ひずみを測定し、ＪＩＳ Ａ １１４９に準じて該コンクリートのヤング係数を測定した。その結果、該プレーンコンクリートの乾燥収縮ひずみは８７３×１０−６、ヤング係数は３１１００Ｎ／ｍｍ２であった。
次に、下記物性を有する、図６に示す１層１スパンの外壁を対象に、前記（１）〜（７）式を用いてひび割れ本数とひび割れ幅を算出した。なお、（１）〜（３）式において、補正係数（ｐ１）は０．８７、補正係数（ｐ２）は０．８６、補正係数（ｐ３）は０．７２、補正値（ｑ１）は９０×１０−６、および補正値（ｑ２）は５０×１０−６であり、また、ひび割れ本数の目標値は４本未満に設定した。
算出されたひび割れ本数は、それぞれ、プレーンコンクリートで４．７本、膨張材含有コンクリートで３．６本、収縮低減剤含有コンクリートで４．０本、膨張材および収縮低減剤含有コンクリートで３．１本であった。したがって、膨張材含有コンクリートと、膨張材および収縮低減剤含有コンクリートが目標値を満たすため、膨張材の単独使用、または膨張材と収縮低減剤の併用が有効と判定した。
3. Determination of effectiveness of shrinkage-reducing material Using the cement, fine aggregate, and coarse aggregate shown in Table 2, plain concrete having a unit water volume of 175 kg / m 3 and a water-cement ratio of 50% was manufactured. JIS A 1129 The dry shrinkage strain of the concrete was measured according to JIS A 1149, and the Young's modulus of the concrete was measured according to JIS A 1149. As a result, the dry shrinkage strain of the plain concrete was 873 × 10 −6 and the Young's modulus was 31100 N / mm 2 .
Next, the number of cracks and the crack width were calculated using the equations (1) to (7) for the outer wall of one layer and one span shown in FIG. In the equations (1) to (3), the correction coefficient (p 1 ) is 0.87, the correction coefficient (p 2 ) is 0.86, the correction coefficient (p 3 ) is 0.72, and the correction value (q 1 ) Was 90 × 10 −6 , and the correction value (q 2 ) was 50 × 10 −6 , and the target number of cracks was set to less than 4.
The calculated number of cracks is 4.7 for plain concrete, 3.6 for concrete containing expansive material, 4.0 for concrete containing shrinkage reducing agent, and 3.1 for concrete containing expansion agent and shrinkage reducing agent, respectively. It was a book. Therefore, since the expandable material-containing concrete and the expandable material and the shrinkage reducing agent-containing concrete satisfy the target values, it was determined that the use of the expandable material alone or the combined use of the expandable material and the shrinkage reducing agent was effective.
［外壁の物性］
鉄筋のヤング係数（Ｅｓ）＝２０００００Ｎ／ｍｍ２
拘束度（λ）＝０．５５
プレーンコンクリートの乾燥開始材齢ｔ０日における材齢ｔ日の収縮ひずみ（εｓｈ（ｔ、ｔ０））＝８７３×１０−６
クリープを考慮した低減係数（ｂ）＝２
外壁の長さ（Ｌ）＝９ｍ
ヤング係数比（ｎ）＝１２．９
鉄筋比（ρ）＝０．４％
プレーンコンクリートの引張限界ひずみ（εｔ）＝０．０００１
比例定数（ａ）＝０．０５
鉄筋径（ｄｂ）＝９．５３ｍｍ
[Physical properties of the outer wall]
Reinforcement Young's modulus (Es) = 200000 N / mm 2
Restraint degree (λ) = 0.55
Shrinkage strain (ε sh (t, t 0 )) at the age of t at the starting age of d 0 of plain concrete (ε sh (t, t 0 )) = 873 × 10 −6
Reduction factor considering creep (b) = 2
Outer wall length (L) = 9m
Young's modulus ratio (n) = 12.9
Reinforcing bar ratio (ρ) = 0.4%
Plain concrete tensile limit strain (ε t ) = 0.0001
Proportional constant (a) = 0.05
Reinforcing bar diameter (d b ) = 9.53 mm
Claims (2)
下記補正係数（ｐ １ ）は０．８２〜０．８７、下記記補正係数（ｐ ２ ）は０．８２〜０．８６、下記補正係数（ｐ ３ ）は０．６４〜０．７２、下記補正値（ｑ １ ）は９０×１０ −６ 〜１９０×１０ −６ 、および下記補正値（ｑ ２ ）は５０×１０ −６ 〜２１０×１０ −６ の範囲内において選択される、収縮低減材料の有効性判定方法。
（Ａ）予めコンクリートのひび割れ本数および／またはひび割れ幅の目標値を設定する、ひび割れ目標値設定工程
（Ｂ）下記（１）〜（３）式のいずれかを用いて乾燥収縮ひずみを算出する、乾燥収縮ひずみ算出工程
（１）膨張材を用いる場合：
乾燥収縮ひずみ＝プレーンコンクリートの乾燥収縮ひずみ×補正係数（ｐ１）−補正値（ｑ１） ・・・（１）
（２）収縮低減剤を用いる場合：
乾燥収縮ひずみ＝プレーンコンクリートの乾燥収縮ひずみ×補正係数（ｐ２） ・・・（２）
（３）膨張材と収縮低減剤を併用する場合：
乾燥収縮ひずみ＝プレーンコンクリートの乾燥収縮ひずみ×補正係数（ｐ３）−補正値（ｑ２） ・・・（３）
（Ｃ）前記乾燥収縮ひずみと下記（４）〜（７）式を用いて、コンクリートのひび割れ本数および／またはひび割れ幅を算出する、ひび割れ特性値算出工程
The following correction coefficient (p 1 ) is 0.82 to 0.87, the following correction coefficient (p 2 ) is 0.82 to 0.86, the following correction coefficient (p 3 ) is 0.64 to 0.72, and The shrinkage-reducing material, wherein the correction value (q 1 ) is selected within the range of 90 × 10 −6 to 190 × 10 −6 , and the following correction value (q 2 ) is selected within the range of 50 × 10 −6 to 210 × 10 −6. Effectiveness judgment method.
(A) A crack target value setting step in which a target value of the number of cracks and / or crack width of concrete is set in advance. (B) Dry shrinkage strain is calculated using any of the following formulas (1) to (3). Drying shrinkage calculation process (1) When using an expansion material:
Drying shrinkage strain = drying shrinkage strain of plain concrete × correction coefficient (p 1 ) −correction value (q 1 ) (1)
(2) When using a shrinkage reducing agent:
Drying shrinkage strain = Drying shrinkage strain of plain concrete x Correction factor (p 2 ) (2)
(3) When using an expansion material and a shrinkage reducing agent in combination:
Drying shrinkage strain = drying shrinkage strain of plain concrete × correction coefficient (p 3 ) −correction value (q 2 ) (3)
(C) Crack characteristic value calculation step of calculating the number of cracks and / or crack width of concrete using the drying shrinkage strain and the following formulas (4) to (7)
The correction coefficient (p 1 ) is 0.87, the correction coefficient (p 2 ) is 0.86, the correction coefficient (p 3 ) is 0.72, the correction value (q 1 ) is 90 × 10 −6 , The method for determining the effectiveness of a shrinkage-reducing material according to claim 1 , wherein the correction value (q 2 ) is 50 × 10 −6 .
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