JP6740925B2 - Method for predicting compressive strength of high-strength concrete and method for designing mixture - Google Patents
Method for predicting compressive strength of high-strength concrete and method for designing mixture Download PDFInfo
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Description
本発明は、蒸気養生を行う超高強度コンクリートの圧縮強度を精度良く予測する方法に関する。また、本発明は該予測方法に基づいた配合設計方法に関する。本発明によれば、シリカフュームを混合したセメントを用いた超高強度プレキャストコンクリートなどについて、蒸気養生による圧縮強度を精度良く予測することができる。 The present invention relates to a method for accurately predicting the compressive strength of ultra high strength concrete that is steam-cured. The present invention also relates to a blending design method based on the prediction method. According to the present invention, it is possible to accurately predict the compressive strength due to steam curing of an ultra-high-strength precast concrete using cement mixed with silica fume.
早強ポルトランドセメントなどの汎用セメントを用いて促進養生を行うプレキャストコンクリートについては、強度発現性を含めた各種性状が明らかにされており、設計基準強度120N/mm２までのプレキャスト部材は、日本建築学会建築工事標準仕様書・同解説 JASS10 プレキャスト鉄筋コンクリート工事（以下JASS 10）において、調合設計法が定められている。しかし、シリカフュームを混合したセメントを用いた超高強度コンクリートについては体系的なデータが整備されておらず、設計基準強度に対応した調合設計法も確立されていない。 For precast concrete that uses accelerated cement using general-purpose cement such as early strength Portland cement, various properties including strength development have been clarified, and precast members up to the design standard strength of 120 N/mm 2 are Standard specifications/commentary of JSCE construction work JASS10 Precast reinforced concrete work (hereinafter JASS10) defines the mix design method. However, systematic data has not been prepared for ultra-high strength concrete using cement mixed with silica fume, and a mixing design method corresponding to the design standard strength has not been established.
従来、コンクリート強度の推定方法等について、特許文献１、２、３に記載されている技術が知られている。例えば、特許文献１には、コンクリートのモルタル部分の圧縮強度とヤング率、および粗骨材の圧縮強度とヤング率から超高強度コンクリートの圧縮強度を推定する方法が示されている。しかし、蒸気養生を行う超高強度コンクリートの圧縮強度を推定する方法は示されていない。
Conventionally, the techniques described in
特許文献２には、圧縮強度が５０N/mm２程度以下であるコンクリートの加熱養生時における圧縮強度の推定法として、積算温度または有効材齢をパラメータとした圧縮強度予測方法が示されている。しかし、本方法では圧縮強度が１００N/mm２を超えるような高強度域での予測精度が低く実用的ではない。 Patent Document 2 discloses a compressive strength prediction method using cumulative temperature or effective material age as a parameter as a method for estimating the compressive strength during heat curing of concrete having a compressive strength of about 50 N/mm 2 or less. However, this method is not practical because the prediction accuracy is low in the high strength region where the compressive strength exceeds 100 N/mm 2 .
特許文献３には、圧縮強度１３０N/mm２以上の高強度プレキャストコンクリートを製造するため、超低熱型セメントとポゾラン物質とを含む結合材を用いたコンクリートを打設し、６０℃〜９０℃の蒸気養生を３〜９時間保持させることを示しているが、圧縮強度の予測方法は示されていない。 In Patent Document 3, in order to produce a high-strength precast concrete having a compressive strength of 130 N/mm 2 or more, concrete using a binder containing an ultra-low heat type cement and a pozzolanic substance is placed, and the temperature of 60° C. to 90° C. Although it is shown that steam curing is maintained for 3 to 9 hours, a method for predicting compressive strength is not shown.
本発明は、従来のコンクリート強度推定方法等では、蒸気養生を行う超高強度コンクリートの圧縮強度を精度良く予測することができないと云う課題を解決したものであり、シリカフュームを混合したセメント等を用いた超高強度プレキャストコンクリートなどについて、蒸気養生時の圧縮強度を精度良く予測することができる圧縮強度予測方法を提供する。また、本発明は該予測方法に基づいた配合設計によるコンクリート製造方法を提供する。 The present invention solves the problem that the conventional concrete strength estimation method and the like cannot predict the compressive strength of super-high strength concrete that is steam-cured with high accuracy, and uses cement mixed with silica fume or the like. Provided is a compressive strength predicting method capable of accurately predicting compressive strength during steam curing of ultra-high strength precast concrete and the like. The present invention also provides a concrete manufacturing method by mixing design based on the prediction method.
本発明は、以下の構成を有する圧縮強度予測方法である。
（イ）蒸気養生を行う高強度コンクリートの圧縮強度の予測方法であって、蒸気養生を２０℃標準養生に換算した有効材齢ｔ(日)における圧縮強度(ｆｔ)を示す次式において、
ｆｔ = ａ×ｔｂ＋ｃ・・・〔１〕
（式中、ａは強度発現係数、ｔｂは有効材齢に基づく材齢関数、ｂは材齢関数の係数、ｃは骨材の種類に拠り決定される補正係数）
有効材齢５日未満は４５≦ａ≦６５および０.２５≦ｂ≦０.８５、および５≦ｃ≦１５の範囲で、有効材齢５日以上は６５≦ａ≦１５０および０.０１≦ｂ≦０.１５および５≦ｃ≦１５の範囲で係数ａ、ｂ、ｃを定めて圧縮強度(ｆｔ)を予測することを特徴とする高強度コンクリートの圧縮強度予測方法。
The present invention is a compression strength prediction method having the following configuration.
(A) A method for predicting the compressive strength of high-strength concrete that undergoes steam curing, in the following formula showing the compressive strength (ft) at an effective material age t (days) converted from steam curing to standard curing at 20° C.
ft=a×t b +c... [1]
(In the formula, a is a strength expression coefficient, t b is a material age function based on effective material age, b is a material age function coefficient, and c is a correction coefficient determined depending on the type of aggregate)
If the effective material age is less than 5 days, 45≦a≦65 and 0.25≦b≦0.85, and 5≦c≦15. If the effective material age is 5 days or more, 65≦a≦150 and 0.01≦ A method for predicting compressive strength of high-strength concrete, which comprises predicting compressive strength (ft) by defining coefficients a, b, and c within the range of b≦0.15 and 5≦c≦15.
本発明の圧縮強度予測方法は以下の態様を含む。
（ロ）蒸気養生を行う高強度コンクリートについて、
水セメント比（Ｗ/Ｃ）が１５％以上〜２０％未満の範囲では、有効材齢５日未満は４９≦ａ≦６２および０.３５≦ｂ≦０.８５、５≦ｃ≦１５の範囲、有効材齢５日以上は９０≦ａ≦１５０および０.０１≦ｂ≦０.１５、５≦ｃ≦１５の範囲
水セメント比（Ｗ/Ｃ）が２０％以上〜２５未満％の範囲では、有効材齢５日未満は５４≦ａ≦６２および０.２５≦ｂ≦０.４０、５≦ｃ≦１５の範囲、有効材齢５日以上は６５≦ａ≦９５および０.１０≦ｂ≦０.１５、５≦ｃ≦１５の範囲
で係数ａ、ｂ、ｃを定めて圧縮強度(ｆｔ)を予測する高強度コンクリートの圧縮強度予測方法。
（ハ）上記(ロ)において定めた係数ａ、ｂ、ｃの圧縮強度曲線を基準曲線とし、一方、予測対象のコンクリートの水セメント比における有効材齢に対する圧縮強度曲線（予測曲線）を、上記基準曲線に対応して定め、該予測曲線に基づいて目的の有効材齢における圧縮強度を把握する高強度コンクリートの圧縮強度予測方法。
（ニ）水セメント比と共に蒸気養生におけるコンクリートの温度履歴を加味した２０℃標準養生に換算した有効材齢および骨材種類による補正係数を含む配合条件に基づく基準曲線を実測値により定め、予測対象のコンクリートの予測曲線を上記基準曲線に対応して定め、該予測曲線に基づいて目的の有効材齢における圧縮強度を把握する高強度コンクリートの圧縮強度予測方法。
（ホ）高強度コンクリートが低熱セメントとポゾラン物質粉末からなる結合材を含有している高強度コンクリートの圧縮強度予測方法。
The compressive strength prediction method of the present invention includes the following aspects.
(B) Regarding high-strength concrete that undergoes steam curing,
When the water cement ratio (W/C) is in the range of 15% to less than 20%, the effective age is less than 5 days, 49≦a≦62 and 0.35≦b≦0.85, 5≦c≦15. In the range of water cement ratio (W/C) of 20% or more and less than 25%, the range of 90≦a≦150 and 0.01≦b≦0.15, 5≦c≦15 is effective for 5 days or more. The range of 54≦a≦62 and 0.25≦b≦0.40, 5≦c≦15 is effective for less than 5 days, and 65≦a≦95 and 0.10≦b for effective age of 5 days or more. A method for predicting compressive strength of high-strength concrete, which predicts compressive strength (ft) by defining coefficients a, b, and c within a range of ≦0.15, 5≦c≦15.
(C) The compressive strength curve of the coefficients a, b, and c determined in (B) above is used as a reference curve, while the compressive strength curve (predictive curve) for the effective age in the water-cement ratio of the concrete to be predicted is A method for predicting compressive strength of high-strength concrete, which is determined according to a reference curve and grasps the compressive strength at a target effective age based on the predictive curve.
(D) A reference curve based on compounding conditions including effective material age converted to 20°C standard curing, which takes into account the temperature history of concrete during steam curing along with the water-cement ratio, and the correction factor depending on the type of aggregate, is determined by actual measurement values, and is to be predicted A predictive curve for concrete is defined in accordance with the reference curve, and the compressive strength predicting method for high-strength concrete is obtained based on the predictive curve to grasp the compressive strength at the target effective material age.
(E) A method for predicting compressive strength of high-strength concrete in which the high-strength concrete contains a binder composed of low-heat cement and pozzolanic substance powder.
本発明は以下の配合設計方法を含む。
（ヘ）上記(ロ)において定めた係数ａ、ｂ、ｃの圧縮強度曲線を基準曲線とし、一方、予測対象のコンクリートの水セメント比における有効材齢に対する圧縮強度曲線（予測曲線）を、上記基準曲線に対応して定め、該予測曲線に基づいて目的の有効材齢における圧縮強度となるように水セメント比を定める高強度コンクリートの配合設計方法。
（ト）上記(ヘ)の方法において、水セメント比と共に蒸気養生におけるコンクリートの温度履歴を加味した２０℃標準養生に換算した有効材齢および骨材種類による補正係数を含む配合条件に基づく基準曲線を実測値により定め、予測対象のコンクリートの予測曲線を上記基準曲線に対応して定め、該予測曲線に基づいて目的の有効材齢における圧縮強度になるように、配合条件を定める高強度コンクリートの配合設計方法。
The present invention includes the following formulation design method.
(F) The compressive strength curve of the coefficients a, b, and c determined in (b) above is used as a reference curve, while the compressive strength curve (predictive curve) for the effective age in the water-cement ratio of the concrete to be predicted is A method for designing and mixing high-strength concrete, which is determined corresponding to a reference curve, and the water-cement ratio is determined based on the prediction curve so that the compressive strength at the target effective age is obtained.
(G) In the method of (f) above, a standard curve based on a mixing condition including a correction coefficient depending on the effective material age and the type of aggregate, which is converted to 20° C. standard curing in which the water-cement ratio and the temperature history of concrete during steam curing are taken into consideration. Is determined by the actual measurement value, the prediction curve of the concrete to be predicted is determined in correspondence with the above-mentioned reference curve, and the compressive strength at the target effective age based on the prediction curve is determined so that the mixing condition of the high-strength concrete is determined. Formulation design method.
本発明において、蒸気養生を行う高強度コンクリートの圧縮強度は、蒸気養生を２０℃養生に換算した有効材齢ｔ(日)における圧縮強度曲線の係数ａ、ｂの範囲が、有効材齢５日を境にして変わることが見出された。本発明の圧縮強度予測方法はこの知見に基づいている。本発明の予測方法によれば、有効材齢５日を境にして圧縮強度曲線の係数ａ、ｂの範囲を変えることによって、蒸気養生を行う高強度コンクリートの圧縮強度を精度良く把握することができる。 In the present invention, the compressive strength of high-strength concrete subjected to steam curing is such that the range of the coefficients a and b of the compressive strength curve at the effective material age t (days) obtained by converting steam curing to 20° C. is 5 days of effective material age. It has been found that it will change at the border. The compressive strength prediction method of the present invention is based on this finding. According to the prediction method of the present invention, the compressive strength of high-strength concrete subjected to steam curing can be accurately grasped by changing the range of the coefficients a and b of the compressive strength curve at the effective material age of 5 days. it can.
本発明の予測方法は、例えば、水セメント比（Ｗ/Ｃ）が異なるコンクリートについて、圧縮強度曲線の係数ａ、ｂを、有効材齢５日を境にし、かつ水セメント比に応じた範囲で定め、さらに骨材種類に拠り決定される補正係数ｃ定めることによって、蒸気養生を行う高強度コンクリートの圧縮強度をより精度良く把握することができる。
The prediction method of the present invention is, for example, for concretes having different water-cement ratios (W/C), the coefficients a and b of the compressive strength curves are set within a range depending on the
本発明の予測方法は、具体的には、例えば、有効材齢５日を境にして定めた係数ａ、ｂおよび骨材種類に拠り決定される補正係数ｃに基づいて算出される圧縮強度曲線を基準曲線とし、一方、予測対象のコンクリートの水セメント比における有効材齢に対する圧縮強度曲線（予測曲線）を、上記基準曲線に対応して定め、該予測曲線に基づいて目的の有効材齢における圧縮強度を把握することができる。 Specifically, the prediction method of the present invention is, for example, a compressive strength curve calculated on the basis of the coefficients a and b defined at the effective material age of 5 days and the correction coefficient c determined based on the type of aggregate. On the other hand, the compressive strength curve (prediction curve) for the effective age in the water-cement ratio of the concrete to be predicted is determined corresponding to the above-mentioned reference curve, and the effective age of the target in the target curve based on the prediction curve. It is possible to grasp the compressive strength.
また、水セメント比と共に、蒸気養生におけるコンクリートの温度履歴を加味した２０℃標準養生に換算した有効材齢、および骨材種類による補正係数を含む配合条件に基づく圧縮強度予測式によって、水セメント比と同様に目的の有効材齢における圧縮強度を把握することができる。温度履歴としては、前置き温度、前置き時間、最高温度、昇温速度、最高温度保持時間、降温速度、降温時間などが挙げられる。 In addition to the water-cement ratio, the water-cement ratio is calculated by the compressive strength prediction formula based on the compounding condition including the effective age converted to 20° C. standard curing in which the temperature history of concrete during steam curing is added, and the correction coefficient depending on the type of aggregate. Similarly to, it is possible to grasp the compressive strength at the intended effective material age. Examples of the temperature history include pre-placement temperature, pre-placement time, maximum temperature, rate of temperature rise, maximum temperature retention time, rate of temperature decrease, time of temperature decrease.
さらに、本発明は、蒸気養生を行う高強度コンクリートについて、上記圧縮強度予測方法に基づいた配合設計方法を含む。上記圧縮強度予測方法によって把握される圧縮強度になるように配合設計することによって、目的の圧縮強度を有する高強度コンクリートを蒸気養生によって製造することができる。 Furthermore, the present invention includes a mixture design method based on the above-mentioned compressive strength prediction method for high-strength concrete that is steam-cured. A high strength concrete having a desired compressive strength can be produced by steam curing by designing a composition so that the compressive strength obtained by the above compressive strength prediction method is obtained.
本発明の予測方法は、低熱セメントとポゾラン物質粉末からなる結合材を含有している高強度コンクリートなど、例えば、シリカフュームを混合したセメントを用いた超高強度プレキャストコンクリートなどについて、蒸気養生による圧縮強度を精度良く予測することができる。 The prediction method of the present invention is a high-strength concrete containing a binder made of low-heat cement and pozzolanic substance powder, for example, for super-high-strength precast concrete using cement mixed with silica fume, compressive strength by steam curing. Can be accurately predicted.
〔具体的な説明〕
以下、本発明の圧縮強度予測方法を具体的に説明する。
本発明の圧縮強度予測方法は、蒸気養生を行う高強度コンクリートの圧縮強度の予測方法であって、蒸気養生を２０℃養生に換算した有効材齢ｔ(日)における圧縮強度(ｆｔ)を示す次式〔１〕において、
ｆｔ = ａ×ｔｂ＋ｃ・・・〔１〕
（式中、ａは強度発現係数、ｔｂは有効材齢に基づく材齢関数、ｂは材齢関数の係数、ｃは骨材の種類に拠り決定される補正係数）
有効材齢５日未満は４５≦ａ≦６５および０.２５≦ｂ≦０.８５、有効材齢５日以上は６５≦ａ≦１５０および０.０１≦ｂ≦０.１５、５≦ｃ≦１５の範囲で係数ａ、ｂ、ｃを定めて圧縮強度(ｆｔ)を予測することを特徴とする高強度コンクリートの圧縮強度予測方法である。
[Specific explanation]
The compression strength prediction method of the present invention will be specifically described below.
The compressive strength prediction method of the present invention is a method for predicting the compressive strength of high-strength concrete that undergoes steam curing, and shows the compressive strength (ft) at an effective material age t (days) converted from steam curing to 20°C. In the following formula [1],
ft=a×t b +c... [1]
(In the formula, a is a strength expression coefficient, t b is a material age function based on effective material age, b is a material age function coefficient, and c is a correction coefficient determined depending on the type of aggregate)
45 ≤ a ≤ 65 and 0.25 ≤ b ≤ 0.85 when the effective age is less than 5 days, and 65 ≤ a ≤ 150 and 0.01 ≤ b ≤ 0.15, 5 ≤ c ≤ when the effective age is 5 days or more. A method for predicting compressive strength of high-strength concrete, characterized in that coefficients a, b, and c are determined within a range of 15 to predict compressive strength (ft).
コンクリートの有効材齢(ｔ日)における圧縮強度ｆｔは、次式〔１〕によって示されることが知られている。
ｆｔ = ａ×ｔｂ＋ｃ・・・〔１〕
式中、ａは強度発現係数、ｔｂは有効材齢に基づく材齢関数、ｂは材齢関数の係数、ｃは骨材の種類に基づく補正係数である。
It is known that the compressive strength ft of concrete at the effective material age (t days) is represented by the following formula [1].
ft=a×t b +c... [1]
In the formula, a is a strength expression coefficient, t b is an age function based on the effective age, b is a coefficient of the age function, and c is a correction coefficient based on the type of aggregate.
式〔１〕について、蒸気養生を行う高強度コンクリートの圧縮強度は、有効材齢５日を境にして、係数ａ、ｂの範囲が変わることが見出された。この試験を以下に示す。 Regarding the formula [1], it was found that the compressive strength of the high-strength concrete subjected to steam curing changes in the range of the coefficients a and b when the effective material age is 5 days. This test is shown below.
表１に示す材料を用い、表２に示す配合条件に従って、水セメント比１５％、２０％、２５％の生コンクリートを製造した。この生コンクリートをおのおの表３に示す養生条件で蒸気養生を行った。養生したコンクリートについて圧縮強度を測定した。この測定値に基づき、蒸気養生を２０℃養生に換算した有効材齢ｔ(日)における圧縮強度曲線（ｆｔ）のグラフを図１（Ｗ/Ｃ＝１５％）、図２（Ｗ/Ｃ＝２０％）、図３（Ｗ/Ｃ＝２５％）に示した。 Using the materials shown in Table 1, according to the mixing conditions shown in Table 2, green concrete with a water cement ratio of 15%, 20% and 25% was produced. This green concrete was steam-cured under the curing conditions shown in Table 3, respectively. The compressive strength of the cured concrete was measured. Based on this measurement value, a graph of the compressive strength curve (ft) at the effective material age t (day) in which steam curing is converted to 20° C. is shown in FIG. 1 (W/C=15%) and FIG. 2 (W/C= 20%) and FIG. 3 (W/C=25%).
図１〜図３に示すように、有効材齢(ｔ)に対する圧縮強度曲線は、式ｆｔ = ａ×ｔｂ＋ｃによって表される。式ｆｔの係数ａ、ｂは有効材齢５日を境にして、その範囲が変わっている。図１〜図３において、区間Ａは有効材齢５日未満、区間Ｂは有効材齢５日以上である。
図１〜図３の圧縮強度曲線について、式ｆｔ = ａ×ｔｂ＋ｃによる近似式を表４に示す。この近似式から、圧縮強度の予測式の係数ａ、ｂは概ね以下の範囲であることがわかる。
（イ）有効材齢５日未満は、概ね４５≦ａ≦６５、概ね０.２５≦ｂ≦０.８５、概ね５≦ｃ≦１５の範囲
（ロ）有効材齢５日以上は、概ね６５≦ａ≦１５０、概ね０.０１≦ｂ≦０.１５、概ね５≦ｃ≦１５の範囲
As shown in FIGS. 1 to 3, the compressive strength curve with respect to the effective material age (t) is represented by the formula ft=a×t b +c. The ranges of the coefficients a and b of the formula ft are changed when the effective material age is 5 days. 1 to 3, the section A has an effective material age of less than 5 days, and the section B has an effective material age of 5 days or more.
Table 4 shows an approximation formula based on the formula ft=a×t b +c for the compression strength curves of FIGS. 1 to 3. From this approximation formula, it is understood that the coefficients a and b of the compression strength prediction formula are in the following ranges.
(B) Effective material age less than 5 days is approximately 45≦a≦65, approximately 0.25≦b≦0.85, approximately 5≦c≦15 (b)
また、表４に示す近似式から、コンクリートの水セメント比の範囲による予測式の係数ａ、ｂの範囲は以下のとおりである。
（１）水セメント比（Ｗ/Ｃ）が１５％以上〜２０％未満の範囲
有効材齢５日未満は、４９≦ａ≦６２、０.３５≦ｂ≦０.８５、５≦ｃ≦１５の範囲
有効材齢５日以上は、９０≦ａ≦１５０、０.０１≦ｂ≦０.１５、５≦ｃ≦１５の範囲
（２）
水セメント比（Ｗ/Ｃ）が２０％以上〜２５未満％の範囲
有効材齢５日未満は、５４≦ａ≦６２、０.２５≦ｂ≦０.４０、５≦ｃ≦１５の範囲
有効材齢５日以上は、６５≦ａ≦９５、０.１０≦ｂ≦０.１５、５≦ｃ≦１５の範囲
Further, from the approximation formula shown in Table 4, the range of the coefficients a and b of the prediction formula according to the range of the water-cement ratio of concrete is as follows.
(1) Water-cement ratio (W/C) is in the range of 15% or more and less than 20%. Effective age is less than 5 days, 49≦a≦62, 0.35≦b≦0.85, 5≦c≦15. Range of
Water cement ratio (W/C) is in the range of 20% to less than 25%. Effective age is less than 5 days, 54≦a≦62, 0.25≦b≦0.40, 5≦c≦15 is effective. In the age of 5 days or more, the range of 65≦a≦95, 0.10≦b≦0.15, 5≦c≦15
本発明の予測式を用いて、以下のようにして水セメント比Ｘ％の圧縮強度を予測することができる。まず、図１〜図３に示す圧縮強度曲線を基準曲線とし、一方、予測対象の水セメント比Ｘ％のコンクリートについて、有効材齢に対する圧縮強度曲線（予測曲線）を、上記基準曲線に対応して定める。例えば、水セメント比が１５％以上〜２０％未満の範囲のＸ％であるときには、水セメント比１５％の予測式ｆ(15%)の基準曲線Ａと、水セメント比２０％の予測式ｆ(20%)の基準曲線Ｂの間に、水セメント比Ｘ％の予測式ｆ(Ｘ%)の予測曲線Ｄを、水セメント比の割合に応じ、基準曲線Ａ、Ｂに対応して想定する。この予測曲線Ｄに基づいて有効材齢の圧縮強度を把握することができる。 Using the prediction formula of the present invention, the compressive strength of the water cement ratio X% can be predicted as follows. First, the compressive strength curve shown in FIGS. 1 to 3 is used as a reference curve, and the compressive strength curve (prediction curve) with respect to the effective age of the concrete of the water cement ratio X% to be predicted corresponds to the above reference curve. To determine. For example, when the water cement ratio is X% in the range of 15% or more and less than 20%, the reference curve A of the prediction formula f (15%) of the water cement ratio of 15% and the prediction formula f of the water cement ratio of 20%. Between the reference curve B of (20%), the prediction curve D of the prediction formula f(X%) of the water cement ratio X% is assumed corresponding to the ratios of the water cement ratio and corresponding to the reference curves A and B. .. Based on this prediction curve D, it is possible to grasp the compressive strength of the effective material age.
本発明の予測式を用いて、コンクリートの配合設計において、目的の有効材齢における圧縮強度となるように水セメント比を定めることができる。例えば、水セメント比Ｘ％の予測式ｆ(Ｘ%)の予測曲線Ｄに基づいて、特定の有効材齢における圧縮強度を把握し、この圧縮強度が目的の値になるように水セメント比を定めることができる。 By using the prediction formula of the present invention, the water-cement ratio can be determined so that the compressive strength at the target effective age is obtained in the concrete mix design. For example, based on the prediction curve D of the prediction formula f(X%) for the water-cement ratio X%, the compressive strength at a specific effective material age is grasped, and the water-cement ratio is adjusted so that this compressive strength becomes a target value. Can be set.
また、水セメント比と共に蒸気養生におけるコンクリートの温度履歴を加味した２０℃標準養生に換算した有効材齢および骨材種類による補正係数を含む配合条件に基づく基準曲線を実測値により定め、予測対象のコンクリートの予測曲線を上記基準曲線に対応して定め、該予測曲線に基づいて目的の有効材齢における圧縮強度になるように、配合条件を定めることができる。温度履歴としては、前置き温度、前置き時間、最高温度、昇温速度、最高温度保持時間、降温速度、降温時間などが挙げられる。 In addition, a reference curve based on the compounding conditions including effective material age converted to 20° C. standard curing that takes into account the temperature history of concrete during steam curing along with the water-cement ratio and the correction coefficient depending on the type of aggregate is set by actual measurement values, and A predictive curve of concrete can be determined corresponding to the above-mentioned reference curve, and the compounding conditions can be determined based on the predictive curve so that the compressive strength at the target effective age is obtained. Examples of the temperature history include pre-placement temperature, pre-placement time, maximum temperature, rate of temperature rise, maximum temperature retention time, rate of temperature decrease, time of temperature decrease.
本発明によれば、超高強度プレキャストコンクリートなどの蒸気養生時の圧縮強度が予測できるので、蒸気養生条件を効率的に最適化することができる。また、早期に効率的に所要の圧縮強度を得ることができるので、型枠回転率が向上し、より多くのコンクリートが製造可能になる。さらに、材料コストや製造のためのエネルギーコスト等含めた総コストを最小とする製造サイクルの設計が可能になり、過大設計を防ぎ、経済的にも有効である。 According to the present invention, the compressive strength of a super-high-strength precast concrete during steam curing can be predicted, so that steam curing conditions can be efficiently optimized. Further, since the required compressive strength can be obtained efficiently at an early stage, the mold rotation rate is improved, and more concrete can be manufactured. Further, it becomes possible to design a manufacturing cycle that minimizes the total cost including material cost and energy cost for manufacturing, prevents excessive design, and is economically effective.
〔実施例１〕
表１に示す材料を用いた。シリカフュームを混合したセメントの一例として、三菱マテリアル社製のシリカフュームセメント（SFC）を使用した。表２に示す配合条件に従って、水セメント比１５％、２０％、２５％の生コンクリートを製造した。この生コンクリートをおのおの表３に示す養生条件で蒸気養生を行った。養生したコンクリートについて圧縮強度を測定した。この測定値に基づき、蒸気養生を２０℃養生に換算した有効材齢ｔ(日)における圧縮強度曲線（ｆｔ）のグラフを図１（Ｗ/Ｃ＝１５％）、図２（Ｗ/Ｃ＝２０％）、図３（Ｗ/Ｃ＝２５％）に示した。また、図１〜図３の圧縮強度曲線について、式ｆｔ = ａ×ｔｂ＋ｃによる近似式を表４に示す。
[Example 1]
The materials shown in Table 1 were used. As an example of cement mixed with silica fume, silica fume cement (SFC) manufactured by Mitsubishi Materials Corporation was used. According to the blending conditions shown in Table 2, ready-mixed concrete having a water cement ratio of 15%, 20% and 25% was produced. This green concrete was steam-cured under the curing conditions shown in Table 3, respectively. The compressive strength of the cured concrete was measured. Based on this measurement value, a graph of the compressive strength curve (ft) at the effective material age t (day) in which steam curing is converted to 20° C. is shown in FIG. 1 (W/C=15%) and FIG. 2 (W/C= 20%) and FIG. 3 (W/C=25%). Further, with respect to the compression strength curves of FIGS. 1 to 3, Table 4 shows an approximate expression by the expression ft=a×t b +c.
〔実施例２〕
図１〜図３に示す圧縮強度曲線を基準曲線Ａ、Ｂ、Ｃとし、一方、予測対象の水セメント比Ｘ％のコンクリートについて、有効材齢に対する圧縮強度曲線（予測曲線）を、上記基準曲線に対応して定める。基準曲線Ａは水セメント比１５％の予測式ｆ(15%)の曲線、基準曲線Ｂは水セメント比２０％の予測式ｆ(20%)の曲線、基準曲線Ｃは水セメント比２５％の予測式ｆ(20%)の曲線である。
水セメント比がＸ％（１５％以上〜２０％未満の範囲）のコンクリートについての予測曲線Ｄ、水セメント比がＹ％（２０％以上〜２５％未満の範囲）のコンクリートについての予測曲線Ｅをおのおの水セメント比の割合に応じ、基準曲線Ａ、Ｂ、Ｃに対応して想定する。図４に予測曲線Ｄ、Ｅを示す。この予測曲線Ｄ、Ｅに基づいて有効材齢の圧縮強度を把握することができる。
[Example 2]
The compression strength curves shown in FIGS. 1 to 3 are referred to as reference curves A, B, and C, while the compression strength curve (prediction curve) with respect to the effective age of the concrete of the water cement ratio X% to be predicted is the above reference curve. It is determined according to. The reference curve A is a curve of a prediction formula f (15%) with a water cement ratio of 15%, the reference curve B is a curve of a prediction formula f (20%) with a water cement ratio of 20%, and the reference curve C is a curve of a water cement ratio of 25%. It is a curve of the prediction formula f (20%).
A prediction curve D for concrete having a water-cement ratio of X% (15% or more and less than 20%) and a prediction curve E for concrete having a water-cement ratio of Y% (20% or more and less than 25%) It is assumed that the reference curves A, B, and C are used according to the ratio of the water-cement ratio. Prediction curves D and E are shown in FIG. Based on these prediction curves D and E, the compressive strength of the effective material age can be grasped.
Claims (7)
ｆｔ = ａ×ｔｂ＋ｃ・・・〔１〕
（式中、ａは強度発現係数、ｔｂは有効材齢に基づく材齢関数、ｂは材齢関数の係数、ｃは骨材種類に拠り決定される補正係数）
有効材齢５日未満は４５≦ａ≦６５および０.２５≦ｂ≦０.８５、有効材齢５日以上は６５≦ａ≦１５０および０.０１≦ｂ≦０.１５の範囲で係数ａ、ｂを定めて圧縮強度(ｆｔ)を予測することを特徴とする高強度コンクリートの圧縮強度予測方法。 A method for predicting the compressive strength of high-strength concrete that undergoes steam curing, in the following formula showing the compressive strength (ft) at effective material age t (days) converted from steam curing to 20°C standard curing,
ft=a×t b +c... [1]
(In the formula, a is a strength expression coefficient, t b is a material age function based on effective material age, b is a material age function coefficient, and c is a correction coefficient determined based on the type of aggregate)
If the effective material age is less than 5 days, 45 ≤ a ≤ 65 and 0.25 ≤ b ≤ 0.85, and if the effective material age is 5 days or more, the coefficient a is in the range of 65 ≤ a ≤ 150 and 0.01 ≤ b ≤ 0.15. , B are set to predict the compressive strength (ft), and the compressive strength predicting method for high-strength concrete is characterized.
水セメント比（Ｗ/Ｃ）が１５％以上〜２０％未満の範囲では、有効材齢５日未満は４９≦ａ≦６２および０.３５≦ｂ≦０.８５、５≦ｃ≦１５の範囲、有効材齢５日以上は９０≦ａ≦１５０および０.０１≦ｂ≦０.１５、５≦ｃ≦１５の範囲、
水セメント比（Ｗ/Ｃ）が２０％以上〜２５未満％の範囲では、有効材齢５日未満は５４≦ａ≦６２および０.２５≦ｂ≦０.４０、５≦ｃ≦１５の範囲、有効材齢５日以上は６５≦ａ≦９５および０.１０≦ｂ≦０.１５の範囲、５≦ｃ≦１５の範囲、
で係数ａ、ｂを定めて圧縮強度(ｆｔ)を予測する請求項１に記載する高強度コンクリートの圧縮強度予測方法。 Regarding high-strength concrete that undergoes steam curing,
When the water cement ratio (W/C) is in the range of 15% to less than 20%, the effective age is less than 5 days, 49≦a≦62 and 0.35≦b≦0.85, 5≦c≦15. , The range of 90≦a≦150 and 0.01≦b≦0.15, 5≦c≦15 when the effective material age is 5 days or more,
When the water cement ratio (W/C) is in the range of 20% to less than 25%, the effective age is less than 5 days, 54≦a≦62 and 0.25≦b≦0.40, 5≦c≦15. , Effective material age 5 days or more, 65≦a≦95 and 0.10≦b≦0.15 range, 5≦c≦15 range,
The method for predicting compressive strength of high-strength concrete according to claim 1, wherein the compressive strength (ft) is predicted by determining the coefficients a and b.
In the method according to claim 6, a reference curve based on a mixing condition including a correction coefficient according to an effective material age and an aggregate type, which is converted into 20° C. standard curing that takes into consideration the temperature history of concrete during steam curing together with a water-cement ratio, is measured. A method for designing a mix of high-strength concrete, wherein a predictive curve of concrete to be predicted is determined in correspondence with the reference curve, and mix conditions are determined based on the predictive curve so that the compressive strength at a target effective age is obtained.
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