JP6147634B2 - Early estimation method of structural concrete strength using ultra high strength concrete - Google Patents
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Description
本発明は、超高強度コンクリートを使用した構造体コンクリート強度を、初期材齢の圧縮強度に基づき推定する方法に関する。 The present invention relates to a method for estimating structure concrete strength using ultra-high-strength concrete based on compressive strength of initial age.
最近の超高層建築物において、設計の自由度や快適な居住空間を確保するため部材のスリム化や長スパン化が進んだ結果、コンクリートの設計基準強度が１００Ｎ／ｍｍ２以上の超高強度コンクリートが用いられるようになった。 In recent high-rise buildings, as a result of slimming of members and long spans to ensure freedom of design and comfortable living space, ultra-high-strength concrete with a concrete design standard strength of 100 N / mm 2 or more Came to be used.
一般に、水結合材比が３０％以下となるような超高強度コンクリートを用いて構築される柱や梁などの構造体は、硬化時の水和熱によって構造体の中心部の温度が高温となる。
材齢初期に自らの水和熱によって高温履歴を受けた構造体コンクリートは、初期材齢では標準水中養生供試体に比べて高い強度を発現するものの、材齢経過にともなう圧縮強度の増進が少なく、長期材齢では標準水中養生供試体よりも低い圧縮強度となる傾向にあるとされている。
そして、日本建築学会では、構造体の要求性能を得るために必要とされるコンクリートの圧縮強度（品質基準強度）において、構造体コンクリート強度が満足しなければならない材齢は９１日としている（非特許文献１）。
そのため、構造体コンクリート強度の推定方法にあっては、その都度、部材と同寸法の構造体モデルを作成する必要があるために、膨大な費用と期間とを要するという問題点があった。
Generally, structures such as columns and beams constructed using ultra-high-strength concrete with a water binder ratio of 30% or less have a high temperature at the center of the structure due to the heat of hydration during curing. Become.
Structural concrete that has undergone a high temperature history due to its own heat of hydration in the early age of age exhibits higher strength than the standard underwater curing specimen in the early age, but there is little increase in compressive strength with age. In long-term ages, the compressive strength tends to be lower than that of the standard underwater curing specimen.
In the Architectural Institute of Japan, in the compressive strength (quality standard strength) of concrete required to obtain the required performance of the structure, the age at which the structure concrete strength must be satisfied is 91 days (non- Patent Document 1).
Therefore, in the method for estimating the structure concrete strength, it is necessary to create a structure model having the same dimensions as the member each time, and thus there is a problem that enormous cost and time are required.
なお、構造体コンクリートとは、構造体とするために打ち込まれ、周囲の環境条件や水和熱による温度条件のもとで硬化したコンクリートである。また、構造体コンクリート強度とは、構造体コンクリートが発現している圧縮強度であり、一般に構造体または構造体と同時に打ち込まれ、同じ養生が施された部材から採取したコア供試体の圧縮強度で表される（非特許文献１）。 The structural concrete is concrete that has been driven into a structural body and hardened under ambient environmental conditions or temperature conditions due to heat of hydration. In addition, the structural concrete strength is the compressive strength at which the structural concrete is expressed, and is generally the compressive strength of the core specimen taken from the structure or the structure that is driven at the same time and is subjected to the same curing. (Non-Patent Document 1).
そこで、初期材齢の強度に基づき長期材齢の強度を推定する方法が、いくつか提案されている。
例えば、特許文献１では、練り混ぜ後のフレッシュコンクリートから、硬化後の強度を短時間で推定するコンクリート強度の推定方法であって、練り混ぜ直後のフレッシュコンクリートから試料を採取したのち、該試料を直ちに乾燥し、フレッシュコンクリート中の推定単位水量を算出し、ついで、配合上の単位セメント量または計量値から推定セメント水比を算出し、ついで、予め算定した、種々の配合のコンクリートのセメント水比とコンクリート強度との相関関係を示す回帰式を用いて、コンクリート強度を早期に推定する方法が提案されている。
しかし、該方法は単位水量と水セメント比の推定値から強度を推定するものであり、その他のコンクリートの特性は考慮されないため、推定精度は必ずしも十分ではなかった。
Thus, several methods for estimating the strength of the long-term age based on the strength of the initial age have been proposed.
For example,
However, this method estimates the strength from the estimated values of the unit water amount and the water-cement ratio, and other properties of the concrete are not taken into account, so the estimation accuracy is not always sufficient.
また、特許文献２では、管理用供試体の材齢２８日圧縮強度から所定の強度補正値を減ずることにより、構造体コア供試体の材齢９１日圧縮強度を推定する高強度コンクリート構造体の強度管理方法において、前記管理用供試体の圧縮強度が、前記構造体コア供試体の前記材齢９１日圧縮強度を上回る、または同等となるような値に設定されている高強度コンクリート構造体の強度管理方法が提案されている。
しかし、該方法では、待機期間が短縮されたとはいえ、それでも材齢２８日まで待たなければならず早期とはいえない。
Further, in
However, in this method, although the waiting period has been shortened, it still has to wait until the age of 28 days, which is not early.
そこで、本発明は、初期材齢の超高強度コンクリート供試体の圧縮強度から、超高強度コンクリートを使用した構造体コンクリート強度を推定する方法を提供することを目的とする。 Then, an object of this invention is to provide the method of estimating the structure concrete strength which uses ultra-high-strength concrete from the compressive strength of the ultra-high-strength concrete specimen of an early age.
本発明者らは、超高強度コンクリートを使用した構造体コンクリート強度の推定方法を種々検討したところ、下記の推定方法は前記目的を達成できることを見出し、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超高強度コンクリートを使用した構造体コンクリート強度の早期推定方法である。
［１］下記（Ａ）〜（Ｄ）の工程を経た材齢７日の超高強度コンクリート供試体の圧縮強度を、同一の材料および配合を有する超高強度コンクリートの材齢９１日における構造体コンクリート強度とみなして推定する、超高強度コンクリートを使用した構造体コンクリート強度の早期推定方法。
（Ａ）２０±３℃の環境下で、超高強度コンクリートを混練した後、該コンクリートを型枠に打ち込み、大気に接するコンクリート面をカバーした封かん状態で、２０±３℃の環境下で材齢１日まで超高強度コンクリートを養生する、前養生工程
（Ｂ）材齢１日が経過した時点で、前記超高強度コンクリートを打ち込んだ型枠の周辺の温度を、１２時間かけて８０〜８５℃まで昇温する、昇温工程
（Ｃ）前記温度に達した後、さらに１２時間にわたり、前記超高強度コンクリートを打ち込んだ型枠の周辺の温度を８０〜８５℃に保持して、材齢２日まで超高強度コンクリートを養生する、保温養生工程
（Ｄ）材齢２日が経過した時点で、前記超高強度コンクリートを打ち込んだ型枠の周辺の温度を、５日間かけて２０±３℃に降温する、降温工程
［２］標準水中養生した場合における材齢２８日の圧縮強度が１００Ｎ／ｍｍ２以上である超高強度コンクリートを、前記早期推定の対象コンクリートとする、前記［１］に記載の超高強度コンクリートを使用した構造体コンクリート強度の早期推定方法。
The inventors of the present invention have studied various estimation methods of structural concrete strength using ultra-high-strength concrete. As a result, the inventors have found that the following estimation method can achieve the object, and completed the present invention.
That is, the present invention is an early estimation method of structural concrete strength using ultra-high strength concrete having the following configuration.
[1] A structure at the age of 91 days of ultra high strength concrete having the same material and composition as the compressive strength of a 7 day old ultra high strength concrete specimen subjected to the following steps (A) to (D) An early estimation method for structural concrete strength using ultra-high-strength concrete that is estimated as concrete strength.
(A) After kneading ultra-high-strength concrete in an environment of 20 ± 3 ° C., the concrete is driven into a mold and sealed in a sealed state covering the concrete surface in contact with the atmosphere. Pre-curing process for curing ultra-high-strength concrete until one day of age (B) When the age of one day has passed, the temperature around the formwork in which the ultra-high-strength concrete has been poured is 80 to 12 hours. The temperature raising step of raising the temperature to 85 ° C. (C) After reaching the temperature, the temperature around the formwork in which the ultra-high strength concrete is poured is maintained at 80 to 85 ° C. for 12 hours, Incubation process of ultra high strength concrete until 2 days of age (D) When the age of 2 days has passed, the temperature around the formwork in which the ultra high strength concrete has been poured is 20 ± over 5 days. Decreasing temperature to 3 ℃ Ultra high strength according to extent [2] Compressive strength at the age of 28 days in the case of standard cured in water is an ultra high strength concrete is 100 N / mm 2 or more, the target concrete of the early estimation, wherein [1] An early estimation method for structural concrete strength using concrete.
本発明の超高強度コンクリートの圧縮強度の早期推定方法によれば、材齢７日の圧縮強度に基づき材齢９１日における構造体コンクリート強度を簡単かつ精度よく推定できる。
したがって、室内試験による配合選定が短期間で可能である。また、実機試験時に作製した模擬構造体の強度発現性を短期間で推定できるため、実機試験における不具合や問題点を早期に発見・認識して、改良することができる。
According to the method for early estimation of the compressive strength of ultra-high-strength concrete of the present invention, the structure concrete strength at age 91 days can be estimated easily and accurately based on the compressive strength at
Therefore, blending selection through laboratory tests is possible in a short period of time. In addition, since the strength expression of the simulated structure produced during the actual machine test can be estimated in a short period of time, defects and problems in the actual machine test can be discovered and recognized at an early stage and improved.
本発明は、前記（Ａ）〜（Ｄ）の養生工程（以下「温度履歴養生」という。）を経た材齢７日の超高強度コンクリート供試体の圧縮強度を、同一の材料および配合を有する超高強度コンクリートの材齢９１日における構造体コンクリート強度とみなして推定する、超高強度コンクリートを使用した構造体コンクリート強度の早期推定方法である。
以下、前記（Ａ）〜（Ｄ）工程等に分けて詳細に説明する。
（Ａ）前養生工程
該工程は、２０±３℃の環境下で、超高強度コンクリートを混練した後、該コンクリートを型枠に打ち込み、大気に接するコンクリート面をカバーした封かん状態で、２０±３℃の環境下で材齢１日まで超高強度コンクリートを養生する工程である。
前記超高強度コンクリートは、好ましくは、標準水中養生した場合における材齢２８日の圧縮強度が１００Ｎ／ｍｍ２以上であるコンクリートである。
前記型枠の大きさ、および形状は、内径１０ｃｍ、高さ２０ｃｍの円柱供試体用の型枠を使用する。なお、型枠の材質は特に制限されず、例えば、鋼製、ブリキ製、合成樹脂製、および紙製等のいずれも使用できる。
また、前記カバーを行うための材料は、フィルム、ラップ、シート、およびビニール袋等が使用できる。
The present invention has the same material and composition as the compressive strength of the 7-day-old ultra-high-strength concrete specimen that has undergone the curing steps (A) to (D) (hereinafter referred to as “temperature history curing”). This is an early estimation method for structural concrete strength using ultra-high strength concrete, which is estimated by assuming that the strength of the structural concrete is 91 days old.
Hereinafter, the steps (A) to (D) will be described in detail.
(A) Pre-curing step In this step, after mixing ultra-high-strength concrete in an environment of 20 ± 3 ° C., the concrete is driven into a mold and sealed in a sealed state covering the concrete surface in contact with the atmosphere. It is a process of curing ultra-high strength concrete in an environment of 3 ° C until the age of 1 day.
The ultra-high-strength concrete is preferably a concrete having a compressive strength of 28 days of age when it is cured in standard water and is 100 N / mm 2 or more.
As the size and shape of the mold, a mold for a cylindrical specimen having an inner diameter of 10 cm and a height of 20 cm is used. In addition, the material of the formwork is not particularly limited, and for example, any of steel, tinplate, synthetic resin, and paper can be used.
Moreover, a film, a wrap, a sheet | seat, a plastic bag, etc. can be used for the material for performing the said cover.
（Ｂ）昇温工程
該工程は、材齢１日が経過した時点で、前記超高強度コンクリートを打ち込んだ型枠の周辺の温度を、１２時間かけて８０〜８５℃まで昇温する工程である。
前記昇温をするための装置として、昇温が可能な恒温槽や恒温恒湿槽等の汎用の装置が挙げられる。
なお、図１に示すように、本発明においては、水セメント比（Ｗ／Ｃ）が２０％未満のコンクリートは８５℃まで、水セメント比が２０％以上のコンクリートは８０℃まで昇温することが好ましい。
(B) Temperature raising step This step is a step of raising the temperature around the formwork in which the ultra-high-strength concrete is driven up to 80 to 85 ° C. over 12 hours when the age of one day has passed. is there.
Examples of the device for raising the temperature include general-purpose devices such as a thermostatic chamber and a constant temperature and humidity chamber capable of raising the temperature.
As shown in FIG. 1, in the present invention, concrete having a water cement ratio (W / C) of less than 20% is heated to 85 ° C., and concrete having a water cement ratio of 20% or more is heated to 80 ° C. Is preferred.
（Ｃ）保温養生工程
該工程は、前記温度に達した後、さらに１２時間にわたり、前記超高強度コンクリートを打ち込んだ型枠の周辺の温度を８０〜８５℃に保持して、材齢２日まで超高強度コンクリートを養生する工程である。
前記保温をするための装置として、前記と同様に、恒温槽や恒温恒湿槽等の汎用の装置を使用することができる。
(C) Thermal Incubation Step This step is to maintain the temperature around the formwork in which the ultra-high strength concrete has been placed at 80 to 85 ° C. for 12 hours after reaching the temperature, and the material age is 2 days. It is a process of curing ultra-high strength concrete.
As the device for maintaining the temperature, a general-purpose device such as a thermostatic chamber or a thermostatic chamber can be used as described above.
（Ｄ）降温工程
該工程は、材齢２日が経過した時点で、前記超高強度コンクリートを打ち込んだ型枠の周辺の温度を、５日間かけて２０±３℃に降温する工程である。
そして、前記降温後、速やかに脱型して、超高強度コンクリートの供試体を取り出し、ＪＩＳ Ａ １１０８「コンクリートの圧縮強度試験方法」に準じて該コンクリートの材齢７日の圧縮強度を測定する。
(D) Temperature-falling step This step is a step of lowering the temperature around the formwork in which the ultra-high-strength concrete is cast to 20 ± 3 ° C. over 5 days when the age of 2 days has passed.
Then, after the temperature is lowered, the mold is quickly removed, and a specimen of ultra-high-strength concrete is taken out, and the compressive strength of the concrete at the age of 7 days is measured according to JIS A 1108 “Concrete compressive strength test method”. .
〔本発明の方法の推定精度が高い理由について〕
以上のように、本発明の推定方法は極めて簡単な方法であるが、その推定精度は、図２の（ａ）に示すように極めて高い。この推定精度が高い理由について以下に考察する。
（i）一般に、材齢初期に自らの水和熱によって高温の履歴を受けたコンクリート（模擬構造体を含む。）は、材齢の経過に伴う強度増進が少なく、例えば、材齢９１日等の長期材齢では、標準水中養生よりも強度が低下する傾向があることが知られている。
（ii）しかし、圧縮強度が１００Ｎ／ｍｍ２以上となる超高強度コンクリートでは水和熱も高いため、例えば、柱部材等のマッシブな構造体は水和熱による高い温度履歴を受けて、圧縮強度が著しく増進し、標準水中養生した長期材齢のコンクリートを上回る程の、高い強度を示すことがある。この場合、従来の標準水中養生ではこの水和発熱を再現できず、標準水中養生した供試体と、現場の構造体からコア抜きして得た供試体とでは、図２の（ｂ）に示すように強度が乖離し、この乖離は強度レベルが高いほど大きくなる。
（iii）これに対し、本発明の方法において実施する温度履歴養生の温度履歴パターン（例えば図１）は、構造体の水和熱による温度履歴を精度よく再現する結果、本発明の方法の推定精度は高いと推測する。
[Reason for high estimation accuracy of the method of the present invention]
As described above, the estimation method of the present invention is a very simple method, but its estimation accuracy is extremely high as shown in FIG. The reason why this estimation accuracy is high will be discussed below.
(I) In general, concrete (including a simulated structure) that has received a high temperature history due to its own heat of hydration in the early age of age is less likely to increase in strength with age, such as 91 days of age. It is known that the strength tends to be lower than that of standard underwater curing at long-term ages.
(Ii) However, since ultra-high strength concrete with a compressive strength of 100 N / mm 2 or higher also has a high heat of hydration, for example, massive structures such as column members are subjected to a high temperature history due to the heat of hydration and compressed. The strength is remarkably increased, and the strength may be higher than the long-term concrete cured under standard water. In this case, the conventional standard water curing cannot reproduce this hydration exotherm, and the specimen obtained by curing the standard water and the specimen obtained by removing the core from the field structure are shown in FIG. In this way, the intensity is deviated, and this deviation increases as the intensity level increases.
(Iii) On the other hand, the temperature history pattern (for example, FIG. 1) of the temperature history curing carried out in the method of the present invention accurately reproduces the temperature history due to the heat of hydration of the structure. I guess the accuracy is high.
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．使用材料
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ＳＦＰＣ（登録商標）、密度３．０４（太平洋セメント社製）
（２）山砂（Ｓ１）
Ａ工場で用いた山砂は千葉県市原市産、密度２．５８
Ｂ工場で用いた山砂は千葉県富津市産、密度２．６０
（３）砕砂（Ｓ２）
Ａ工場で用いた砕砂は山梨県大月市産、密度２．６２
Ｂ工場で用いた砕砂は東京都青梅市産、密度２．６２
（４）砕石２００５（Ｇ）
Ａ工場で用いた砕石は山梨県大月市産、密度２．６４、実積率６０．０％
Ｂ工場で用いた砕石は東京都青梅市産、密度２．６４、実積率６１．０％
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
1. Materials used (1) Silica fume premix cement (C)
SFPC (registered trademark), density 3.04 (manufactured by Taiheiyo Cement)
(2) Mountain sand (S1)
The mountain sand used at Factory A is from Ichihara City, Chiba Prefecture, with a density of 2.58.
The mountain sand used at factory B is from Futtsu City, Chiba, with a density of 2.60.
(3) Crushed sand (S2)
The crushed sand used at Factory A is from Otsuki City, Yamanashi Prefecture, with a density of 2.62.
The crushed sand used at Factory B is from Ome City, Tokyo, with a density of 2.62.
(4) Crushed stone 2005 (G)
The crushed stone used at Factory A is from Otsuki City, Yamanashi Prefecture, density 2.64, actual volume ratio 60.0%
The crushed stone used at Factory B is from Ome City, Tokyo, density 2.64, actual volume ratio 61.0%.
２．試験方法
（１）超高強度コンクリートの混練
Ａ工場とＢ工場において、表１に示す配合に従い前記材料を用いて、２０℃の環境下で超高強度コンクリートを混練した。該コンクリートは、以下の模擬体、温度履歴養生用の供試体、および標準水中養生用の供試体の作製に供した。
2. Test method (1) Kneading of ultra-high strength concrete Ultra-high-strength concrete was kneaded in an environment of 20 ° C. in the A factory and the B factory using the materials according to the formulation shown in Table 1. The concrete was used for the preparation of the following simulated body, a specimen for temperature history curing, and a specimen for standard water curing.
（２）模擬体の作製と養生
前記コンクリートの一部は、柱の中央部を想定して上下２面を発泡スチロール等の断熱材で挟んだ縦１ｍ、横１ｍ、高さ１ｍの型枠に打ち込んで模擬体を成形し、型枠のまま現場で養生した後、材齢９１日の直前に模擬体からコア抜きして、コア供試体を採取した。
(2) Manufacture and curing of simulated body Part of the concrete is driven into a 1m vertical, 1m wide, 1m high mold frame with two upper and lower surfaces sandwiched by heat insulating materials such as polystyrene, assuming the center of the column. After the mock-up was molded and cured on-site in the form, the core was removed from the mock-up just before the age of 91 days, and a core specimen was collected.
（３）温度履歴養生用供試体の作製と養生
前記コンクリートの一部は、内径１０ｃｍ、高さ２０ｃｍの型枠に打ち込み、大気に接するコンクリート面をラップで覆い、ビニールテープで封をして封かん状態とし、２０℃の環境下で材齢１日まで養生した。
材齢１日が経過した時点で、前記超高強度コンクリートの入った型枠を、加熱装置を備えた恒温恒湿槽内に載置し、１２時間かけて槽内を、水セメント比（Ｗ／Ｃ）が２０％未満のコンクリートでは８５℃まで、また、水セメント比が２０％以上のコンクリートでは８０℃まで昇温した。
該温度に達した後、さらに１２時間にわたり、槽内の温度を前記温度に保持して、材齢２日まで養生した。材齢２日が経過した時点で、前記超高強度コンクリートの入った型枠の周辺の温度を、５日間かけて２０℃に降温して、材齢７日まで温度履歴養生を行った。図１に、以上の温度履歴パターンを示す。
(3) Preparation and curing of specimen for temperature history curing Part of the concrete is driven into a mold with an inner diameter of 10 cm and a height of 20 cm, and the concrete surface in contact with the air is covered with wrap and sealed with vinyl tape. It was made into a state and was cured until the age of one day in an environment of 20 ° C.
When the age of one day has passed, the mold containing the ultra-high-strength concrete is placed in a thermo-hygrostat equipped with a heating device, and the water-cement ratio (W / C) was raised to 85 ° C. for concrete with less than 20%, and up to 80 ° C. for concrete with a water-cement ratio of 20% or more.
After reaching this temperature, the temperature in the tank was maintained at the above temperature for another 12 hours, and was cured until the age of 2 days. When the age of 2 days passed, the temperature around the formwork containing the ultra high strength concrete was lowered to 20 ° C. over 5 days, and the temperature history curing was performed until the age of 7 days. FIG. 1 shows the above temperature history pattern.
（４）標準水中養生用供試体の作製と養生
比較のため、前記コンクリートを用いて、前記ＪＩＳに準拠して標準水中養生供試体を作製し、材齢２８日まで標準水中養生した。
(4) Preparation and curing of specimen for standard underwater curing For comparison, a standard underwater curing specimen was prepared using the concrete according to the JIS, and was cured under standard water until the age of 28 days.
（５）圧縮強度の測定
前記コア供試体、温度履歴養生供試体、および標準水中養生供試体を用いて、ＪＩＳ Ａ １１０８に準じて圧縮強度を測定した。コア供試体の強度と温度履歴養生供試体の強度の相関を図２の（ａ）に、コア供試体の強度と標準水中養生供試体の強度の相関を図２の（ｂ）に示す。
図２の（ａ）に示すように、材齢９１日のコア供試体の強度と、材齢７日の温度履歴養生供試体の強度は一致している。これに対し、図２の（ｂ）に示すように、材齢９１日のコア供試体の強度と、従来の方法である材齢２８日の標準水中養生供試体の強度の相関は悪く、特に、前記のとおり、強度が高くなるほど両者の強度の不一致は大きくなる。
したがって、本発明の超高強度コンクリートを使用した構造体コンクリート強度の早期推定方法によれば、材齢７日の圧縮強度に基づき、材齢９１日における構造体コンクリート強度を簡単かつ精度よく推定できる。
(5) Measurement of compressive strength The compressive strength was measured according to JIS A 1108 using the core specimen, the temperature history curing specimen, and the standard water curing specimen. FIG. 2 (a) shows the correlation between the strength of the core specimen and the strength of the temperature history curing specimen, and FIG. 2 (b) shows the correlation between the strength of the core specimen and the standard water curing specimen.
As shown to (a) of FIG. 2, the intensity | strength of the 91-day-old core specimen and the intensity | strength of the 7-day-old temperature history curing specimen correspond. On the other hand, as shown in FIG. 2 (b), the correlation between the strength of the 91-year-old core specimen and the strength of the conventional underwater curing specimen of 28-year-old standard method is poor, As described above, the higher the strength, the greater the mismatch between the strengths of the two.
Therefore, according to the early estimation method of the structure concrete strength using the ultra high strength concrete of the present invention, the structure concrete strength at the age of 91 days can be estimated easily and accurately based on the compressive strength at the age of 7 days. .
Claims (2)
（Ａ）２０±３℃の環境下で、超高強度コンクリートを混練した後、該コンクリートを型枠に打ち込み、大気に接するコンクリート面をカバーした封かん状態で、２０±３℃の環境下で材齢１日まで超高強度コンクリートを養生する、前養生工程
（Ｂ）材齢１日が経過した時点で、前記超高強度コンクリートを打ち込んだ型枠の周辺の温度を、１２時間かけて８０〜８５℃まで昇温する、昇温工程
（Ｃ）前記温度に達した後、さらに１２時間にわたり、前記超高強度コンクリートを打ち込んだ型枠の周辺の温度を８０〜８５℃に保持して、材齢２日まで超高強度コンクリートを養生する、保温養生工程
（Ｄ）材齢２日が経過した時点で、前記超高強度コンクリートを打ち込んだ型枠の周辺の温度を、５日間かけて２０±３℃に降温する、降温工程 Considering the compressive strength of the super high strength concrete of the age 7 days after the following steps (A) to (D) as the structural concrete strength at the age of 91 days of the super high strength concrete having the same material and composition An early estimation method for structural concrete strength using ultra-high strength concrete.
(A) After kneading ultra-high-strength concrete in an environment of 20 ± 3 ° C., the concrete is driven into a mold and sealed in a sealed state covering the concrete surface in contact with the atmosphere. Pre-curing process for curing ultra-high-strength concrete until one day of age (B) When the age of one day has passed, the temperature around the formwork in which the ultra-high-strength concrete has been poured is 80 to 12 hours. The temperature raising step of raising the temperature to 85 ° C. (C) After reaching the temperature, the temperature around the formwork in which the ultra-high strength concrete is poured is maintained at 80 to 85 ° C. for 12 hours, Incubation process of ultra high strength concrete until 2 days of age (D) When the age of 2 days has passed, the temperature around the formwork in which the ultra high strength concrete has been poured is 20 ± over 5 days. Decreasing temperature to 3 ℃ Degree
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