JP4009118B2 - Method for estimating the compressive strength of concrete in structures - Google Patents

Description

【数２】

なお、同式中の「ｋＴ」は浸透係数〔１０ ^-16 ・ｍ ² 〕、「Ｌ」は浸透深さ〔ｍｍ〕、「Ｖｃ」は前記内側チャンバー及び前記ホース内の空気総量〔ｍ ³ 〕、「Ａ」は前記内側チャンバー（コンクリート表面との当接部分）の断面積〔ｍ ² 〕（理論値）、「μ」は空気の動粘度〔Ｎｓ／ｍ ² 〕、εはコンクリートの空隙率〔ｍ ³ ／ｍ ^-3 〕、Ｐａは大気圧〔Ｎ／ｍ ² 〕、ｔは試験時間〔ｓ〕、ｔ ₀ は６０〔ｓ〕、ΔＰｔは圧力上昇値〔Ｎ／ｍ ² 〕、ｌｎは自然対数である。
【０００６】
【０００７】
＜請求項２項記載の発明＞
浸透係数、浸透深さが小さいほど構造物のコンクリートの圧縮強度が大きいと推定する請求項１記載の構造物のコンクリートの圧縮強度推定方法。
【０００８】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
（供試体の作成・養生）
構造物のコンクリート（以下、単に対象コンクリートともいう。）の圧縮強度を推定するにあたっては、まず、それぞれの圧縮強度が異なる少なくとも３種類のコンクリート供試体を作成する。本実施の形態では、その例として、圧縮強度が１５、２０、３０、４５及び６０Ｎ／ｍｍ²となるように５種類の供試体を作成する。
【０００９】
この際、これらの供試体は、対象コンクリートと同一の材料で、しかも実質的に同一の形状となるように作成するのが好ましい。圧縮強度の推定精度を向上させるためである。供試体の形状は、例えば、コンクリート構造物を対象とする場合であれば、角形柱等の場合は、柱部材（例えば、高さ６０×２０×４０ｃｍ、高さ１２０×２０×５０ｃｍなど）とし、床スラブ等の場合は、床部材（例えば、高さ２０×６０×５０ｃｍ、高さ２０×６０×４５ｃｍ、高さ２０×２０×６０ｃｍ、高さ２０×６０×４０ｃｍなど）とすることができる。
【００１０】
このようにして作成した各供試体は、少なくとも対象コンクリートと養生環境を同一にして養生するのが好ましい。例えば、大気中で養生したコンクリートを対象とするのであれば空気中で、水中で養生したコンクリートを対象とするのであれば水中で、養生剤を塗布して養生したコンクリートを対象とするのであれば養生剤を塗布して養生する。養生環境を同一にするのは、養生環境によって、供試体の性状が大きく異なるためである。
【００１１】
各供試体の養生は、その期間を、例えば、１日、２日、３日とすることもできるが、７日以上とするのが好ましく、２８日以上とするのがより好ましい。供試体の性質・状態を安定化させるためである。
【００１２】
（供試体の浸透係数・浸透深さの計測）
次に、以上のようにして作成・養生した各供試体について、その浸透係数及び浸透深さの少なくとも一方を、本実施の形態では双方を計測する。この計測は、以下に示す当接体１を用いて行う。
当接体１は、図１及び図２に示すように、当接本体２の中央部にコンクリートＣ表面側に開口し、減圧ポンプなどからなる図示しない強制減圧手段にホース４を介して連なる内側チャンバー２Ａを有し、この内側チャンバー２Ａの外側に当接本体２をコンクリートＣ表面に密着させる密着手段を有し、この密着手段により当接本体２をコンクリートＣ表面に密着させたとき、内側チャンバー２Ａ内が閉鎖空間Ｉとなる構造とされている。特に、本実施の形態では、かかる密着手段は、内側チャンバー２Ａの外側に形成されたコンクリートＣ表面側に開口する環状の外側チャンバー３を有し、この外側チャンバー３に連なって減圧ポンプなどからなる図示しない密着減圧手段がホース５を介して接続され、密着減圧手段の作動による外側チャンバー３内Ｏの減圧に伴って、当接本体２がコンクリートＣ表面に密着する構造とされている。
【００１３】
浸透係数及び浸透深さを計測するにあたっては、まず、以上のようにしてなる当接体１を、コンクリートＣ表面にあてがい、外側チャンバー３内Ｏを、図示しない密着減圧手段により減圧ホース５を介して減圧する。これにより、コンクリートＣ等をなんら損壊することなく、当接本体２が対象コンクリートＣに対して密着した状態で取り付けられる。
【００１４】
当接本体２をコンクリートＣに取り付けたら、又はこの取り付けと同時に、前記あてがいにより閉鎖空間Ｉとなった内側チャンバー２Ａ内（例えば、１．０１５〜０．９ＭＰａ）を、図示しない強制減圧手段によってホース４を介して、例えば、０．１〜０．０１ＭＰａとなるまで減圧する。これにより、コンクリートＣの浸透係数及び浸透深さの計測が可能となる。
【００１５】
浸透係数及び浸透深さは、次式（１）又は次式（２）から求められる。なお、同式中の「ｋＴ」は浸透係数〔１０^-16・ｍ²〕、「Ｌ」は浸透深さ〔ｍｍ〕、「Ｖｃ」は内側チャンバー２Ａ及びホース４内の空気総量〔ｍ³〕、「Ａ」は内側チャンバー２Ａ（コンクリートＣ表面との当接部分）の断面積〔ｍ²〕（理論値）、「μ」は空気の動粘度〔Ｎｓ／ｍ²〕（通常２．０×１０^-5）、εはコンクリートの空隙率〔ｍ³／ｍ^-3〕（通常０．１５）、Ｐａは大気圧〔Ｎ／ｍ²〕、ｔは試験時間〔ｓ〕、ｔ₀は６０〔ｓ〕、ΔＰｔは圧力上昇値〔Ｎ／ｍ²〕、ｌｎは自然対数である。
【数１】

【数２】

【００１６】
この閉鎖空間Ｉの減圧は、外側チャンバー３内Ｏの圧力と同一となるまで、又は同一となるように行うのが好ましい。これは、外側チャンバー３内Ｏの減圧によって生じるコンクリート部位Ｃ２（コンクリートＣのうちの外側チャンバー３と対面する部位をいう。）における気流が、閉鎖空間Ｉの減圧によって生じるコンクリート部位Ｃ１（コンクリートＣのうちの内側チャンバー２Ａと対面する部位をいう。）における気流に影響を与え、結果、浸透係数及び浸透深さが不正確になるのを防止するためである。
【００１７】
閉鎖空間Ｉの圧力と外側チャンバー３内Ｏの圧力とを同一とするためには、例えば、強制減圧手段と密着減圧手段とを１つの減圧ポンプで構成すればよい。
【００１８】
本実施の形態では、内側チャンバー２Ａ及び外側チャンバー３を、断面略円形状とし、かつ当接本体２を介して一体化したが、これに限る趣旨ではない。断面を略方形状、楕円形状などと適宜変更することができる。また、両者を一体化させずに別体とすることもできる。
【００１９】
（圧縮強度の実測）
以上のようにして浸透係数及び浸透深さを計測した供試体について、次に、その圧縮強度を実測する。この実測は、例えば、円柱供試体の場合は、ＪＩＳ Ａ １１０８「コンクリートの圧縮強度試験方法」によることができ、他の供試体の場合は、コアを切り取って試験を行うＪＩＳ Ａ １１０７「コンクリートからのコア及びはりの切り取り方法並びに強度試験方法」によることができる。
【００２０】
（推定式の確立）
以上のようにして各供試体の圧縮強度を実測したら、先に計測した浸透係数及び浸透深さとで回帰分析し、浸透係数及び浸透深さから圧縮強度を推定するための推定式を求める。
【００２１】
（対象コンクリートの浸透係数・浸透深さの計測）
以上と並行して、又は前後して、対象コンクリートについても、その浸透係数及び浸透深さの少なくとも一方を、本実施の形態では双方を計測する。この計測は、前述した当接体１を用い、前述したのと同様の方法によって行うことができる。
【００２２】
（圧縮強度の推定）
以上のようにして、推定式を確立し、対象コンクリートの浸透係数及び浸透深さを計測したら、この浸透係数及び浸透深さを推定式に代入する。これにより、コンクリートの圧縮強度が推定される。
【００２３】
（その他）
（１） 以上では、供試体の作成・養生、推定式の確立から対象コンクリートの圧縮強度推定までを連続して行う形態を説明したが、これに限る趣旨ではない。あらかじめ推定式を確立しておき、この推定式をもとに対象コンクリートの圧縮強度推定を行うこともできる。この場合は、形状や養生環境などを特定した推定式を複数容易しておくのが好ましい。
【００２４】
（２） また、本発明で適用対象となるコンクリートは、その種類が特に限定されるものではない。一般に用いられている、例えば、普通コンクリート、軽量コンクリート、舗装コンクリートなどの他、粗骨材を欠くコンクリート、すなわちモルタルをも対象とすることができる。
【００２５】
（３） さらに、本発明の適用対象となるコンクリートは、その形状・存在状態が特に限定されるものではない。土木構造物、建築構造物、その他のあらゆる構造物の一部として存在するコンクリートや、コンクリート製品の圧縮強度を推定することも可能である。
【００２６】
（４） 本形態による場合、浸透係数から圧縮強度を推定することも、浸透深さから圧縮強度を推定することも可能であるが、両測定値を総合評価して圧縮強度を推定すると、なお好適である。
【００２７】
【実施例】
以下、実施例に基づいて、浸透係数及び浸透深さと圧縮強度との相関関係を明らかにする。
（供試体の作成・養生）
本実施例では、目標強度、材齢、形状及び養生環境を変化させて供試体を作成した。具体的には、供試体の目標強度を、１５（普通）、２０（普通）、３０（普通）、４５（普通）、６０（普通）、３０（モルタル）Ｎ／ｍｍ²、の６通りとした。また、供試体の材齢は、３、７、８、１４、２８、４０、４８、４９、５６、３６５日の１０通りとした。供試体の形状及び大きさは、円柱供試体（高さ２０×φ１０ｃｍ）、曲げ供試体（高さ１５×１５×５３ｃｍ、高さ１５×１５×６０ｃｍ）、柱部材（高さ６０×２０×４０ｃｍ、高さ１２０×２０×５０ｃｍ）、床部材（高さ２０×６０×５０ｃｍ、高さ２０×６０×４５ｃｍ、高さ２０×２０×６０ｃｍ、高さ２０×６０×４０ｃｍ）の４種類、計９通りとした。養生環境は、水中養生、空気中養生、養生剤塗布養生（塗布量６５ｇ／ｃｍ²又は１３０ｇ／ｃｍ²）、湿潤養生、屋外養生の５通りとした。
【００２８】
（浸透係数・浸透深さの計測）
各供試体について、実施の形態で示した当接体１を用いて、それぞれ浸透係数及び浸透深さを測定した。
なお、「Ｖｃ」は２２２×１０^-6〔ｍ³〕、「Ａ」は１９．６×１０^-4〔ｍ²〕、「μ」は２．０×１０^-5〔Ｎｓ／ｍ²〕、「ε」は０．１５〔ｍ³／ｍ^-3〕であった。
【００２９】
（圧縮強度の実測）
各供試体の圧縮強度の実測は、円柱供試体についてはそのままの状態で、その他の供試体については供試体から切り取ったコア（高さ２０×φ１０ｃｍ）について、それぞれＪＩＳ Ａ １１０８に基づいて行った。コア抜きには、コア抜きドリルを用いた。
【００３０】
（試験結果及び考察）
図３に浸透係数とコアの圧縮強度との関係を、図４に浸透深さとコアの圧縮強度との関係を、次式（３）に図３に関する単回帰式を、次式（４）に図４に関する単回帰式を、図５に次式（３）の精度を、図６に次式（４）の精度を示した。浸透係数、浸透深さが増加するに従って、圧縮強度は低下することがわかる。したがって、浸透係数、浸透深さが小さいほど対象コンクリートの圧縮強度が大きいと推定しうることがわかる。なお、Ｆｃはコアの圧縮強度（Ｎ／ｍｍ²）、Ｋは浸透係数（１０^-16ｍ²）、Ｌは浸透深さ（ｍｍ）である。
【数３】

【数４】

【００３１】
（重回帰分析）
以上の試験で得られたデータを重回帰分析（変数増減法、Ｆ_in＝Ｆ_out＝２．０）した。浸透係数に基づくデータからは次式（５）が、浸透深さに基づくデータからは次式（６）が得られた。この式の精度を、図７及び図８に示した。なお、コアの圧縮強度Ｆｃ（Ｎ／ｍｍ²）を目的変数とし、浸透係数Ｋ（１０^-16ｍ²）、浸透深さＬ（ｍｍ）、養生環境ＹＯ（１：空気中、２：養生剤塗布（６５）、３：養生剤塗布（１３０）、４：湿潤、５：水中）、材齢ＺＡ（日）、形状ＤＡＳ（１：床部材、２：曲げ供試体、３：円柱供試体・柱部材）、測定場所ＳＯ（１：上面、２：側面上部、３：側面中部、４：側面下部、５：下面）を説明変数として採用した（式下段の（ ）内はＴ値、そのさらに下段のＮはデータ数、Ｒは重相関係数、ｅ_sは残差の標準偏差（Ｎ／ｍｍ²）である。）。
【数５】

【数６】

【００３２】
これらの式から、浸透係数及び浸透深さとコアの圧縮強度との間には、高度の相関関係を認めうることがわかる。したがって、浸透係数又は浸透深さに基づくと、コンクリート表面の状態に左右されることなく、比較的簡易に圧縮強度を推定しうることがわかる。また、浸透係数、浸透深さが小さいほど、測定場所が下部ほど、材齢が経過するほど、圧縮強度が大きくなっていることもわかる。
【００３３】
【発明の効果】
以上のとおり、本発明に係る方法によれば、コンクリート表面の状態に左右されることなく、比較的簡易に構造物のコンクリートの圧縮強度を推定することができる。
【図面の簡単な説明】
【図１】 当接体の断面模式図である。
【図２】 当接体の斜視図である。
【図３】 浸透係数とコアの圧縮強度との関係を示した図である。
【図４】 浸透深さとコアの圧縮強度との関係を示した図である。
【図５】 （３）式の実績値と計算値である。
【図６】 （４）式の実績値と計算値である。
【図７】 （５）式の実績値と計算値である。
【図８】 （６）式の実績値と計算値である。
【符号の説明】
１…当接体、２…当接本体、２Ａ…内側チャンバー、３…外側チャンバー、４，５…ホース、Ｃ…コンクリート、Ｉ…閉鎖空間、Ｏ…外側チャンバー内空間。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for estimating the compressive strength of concrete in a structure by nondestructive testing.
[0002]
[Prior art]
One indicator of the concrete durability of a structure is the compressive strength of the concrete. Therefore, various methods for estimating the compressive strength of concrete based on the results of nondestructive tests have been proposed. Above all, the rebound degree method (hammer method), that is, the non-destructive test method in which the concrete surface is hit with a test hammer, the amount of rebound (rebound degree) of this test hammer is measured, and the compressive strength is estimated based on this measured value. However, it is widely used as a useful one.
[0003]
[Problems to be solved by the invention]
However, the amount of rebound of the test hammer is greatly affected by slight differences in conditions such as the condition of the concrete surface. Therefore, the estimation result of the compressive strength by the hammer method has a large variation, and it is difficult to use this as the only index.
[0004]
Then, the main subject of this invention is providing the method which can estimate the compressive strength of the concrete of a structure comparatively easily, without being influenced by the state of concrete surface.
[0005]
[Means for Solving the Problems]
The present invention that has solved the above problems is as follows.
<Invention of Claim 1>
There is an inner chamber that opens on the concrete surface side in the center of the abutment body, and is connected to the forced decompression means via a hose, and an annular outer chamber that opens on the concrete surface side is formed outside this inner chamber , A contact pressure reducing means is connected to the chamber, and has a contact means configured so that the abutting body comes into close contact with the concrete surface in accordance with the pressure reduction in the outer chamber by the operation of the contact pressure reducing means. When the contact body is brought into close contact with the concrete surface by means, the contact body having a structure in which the inside chamber becomes a closed space,
Applying to the concrete surface of the structure, the contact body is brought into close contact with the concrete surface of the structure by the contact means, and the inside of the inner chamber is decompressed by the decompression means, thereby reducing the concrete of the structure. Both of the penetration coefficient and the penetration depth are measured based on the following formula (1) or the following formula (2), and the compressive strength of the concrete of the structure is estimated from the measured value. A method for estimating the compressive strength of concrete.
[Expression 1]

[Expression 2]

In the equation, “kT” is a penetration coefficient [10 ⁻¹⁶ · m ² ], “L” is a penetration depth [mm], and “Vc” is a total air volume [m ³ ] in the inner chamber and the hose. , “A” is the cross-sectional area [m ² ] (theoretical value) of the inner chamber (contact portion with the concrete surface ), “μ” is the kinematic viscosity of air [Ns / m ² ], and ε is the porosity of the concrete. [ M ³ / m ⁻³ ], Pa is the atmospheric pressure [N / m ² ], t is the test time [s], t ₀ is 60 [s], ΔPt is the pressure increase value [N / m ² ], and ln is It is a natural logarithm.
[0006]
[0007]
<Invention of Claim 2 >
The method for estimating the compressive strength of concrete in a structure according to claim 1, wherein it is estimated that the compressive strength of the concrete in the structure is larger as the penetration coefficient and the penetration depth are smaller.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
(Creation and curing of specimens)
In estimating the compressive strength of the concrete of the structure (hereinafter also simply referred to as target concrete), first, at least three types of concrete specimens having different compressive strengths are prepared. In this embodiment, as an example, five types of specimens are prepared so that the compressive strength is 15, 20, 30, 45, and 60 N / mm ² .
[0009]
At this time, it is preferable that these specimens are made of the same material as the target concrete and have substantially the same shape. This is to improve the estimation accuracy of the compression strength. The shape of the specimen is, for example, a concrete structure, and in the case of a rectangular column or the like, a column member (for example, a height of 60 × 20 × 40 cm, a height of 120 × 20 × 50 cm, etc.) is used. In the case of a floor slab or the like, a floor member (for example, height 20 × 60 × 50 cm, height 20 × 60 × 45 cm, height 20 × 20 × 60 cm, height 20 × 60 × 40 cm, etc.) is used. it can.
[0010]
Each specimen prepared in this manner is preferably cured with at least the same concrete and curing environment. For example, if you are targeting concrete cured in the air, in the air if you are targeting concrete cured in water, if you are targeting concrete cured by applying a curing agent in water Apply a curing agent and cure. The reason for making the curing environment the same is that the properties of the specimens vary greatly depending on the curing environment.
[0011]
The period of each specimen can be set to, for example, 1 day, 2 days, or 3 days, preferably 7 days or more, and more preferably 28 days or more. This is to stabilize the properties and state of the specimen.
[0012]
(Measurement of penetration coefficient and penetration depth of specimen)
Next, with respect to each specimen prepared and cured as described above, at least one of the penetration coefficient and the penetration depth is measured in the present embodiment. This measurement is performed using the contact body 1 shown below.
As shown in FIGS. 1 and 2, the abutment body 1 is opened on the concrete C surface side at the center of the abutment body 2 and is connected to a forced decompression means (not shown) such as a decompression pump via a hose 4. A chamber 2A, and a contact means for bringing the contact body 2 into close contact with the concrete C surface outside the inner chamber 2A. When the contact body 2 is brought into close contact with the concrete C surface by the contact means, the inner chamber The interior of 2A is a closed space I. In particular, in the present embodiment, the contact means has an annular outer chamber 3 that opens to the surface side of the concrete C formed outside the inner chamber 2A, and is composed of a decompression pump or the like connected to the outer chamber 3. A contact pressure reducing means (not shown) is connected via a hose 5, and the contact main body 2 is in close contact with the concrete C surface as the inside pressure O in the outer chamber 3 is reduced by the operation of the contact pressure reducing means.
[0013]
In measuring the penetration coefficient and penetration depth, first, the contact body 1 as described above is applied to the surface of the concrete C, and the inside O of the outer chamber 3 is passed through the decompression hose 5 by the contact decompression means (not shown). And depressurize. Thereby, the contact main body 2 is attached in close contact with the target concrete C without damaging the concrete C or the like.
[0014]
When the contact main body 2 is attached to the concrete C or simultaneously with the attachment, the hose is formed in the inner chamber 2A (for example, 1.015 to 0.9 MPa) that has become the closed space I by the above-mentioned application by forced decompression means (not shown). 4, for example, the pressure is reduced to 0.1 to 0.01 MPa. Thereby, the penetration coefficient and penetration depth of concrete C can be measured.
[0015]
The penetration coefficient and the penetration depth are obtained from the following formula (1) or the following formula (2). In this equation, “kT” is the penetration coefficient [10 ⁻¹⁶ · m ² ], “L” is the penetration depth [mm], and “Vc” is the total air volume [m ³ ] in the inner chamber 2A and the hose 4. , “A” is the cross-sectional area [m ² ] (theoretical value) of the inner chamber 2A (contact portion with the concrete C surface), “μ” is the kinematic viscosity of air [Ns / m ² ] (usually 2.0 × 10 ⁻⁵ ), ε is the porosity of concrete [m ³ / m ⁻³ ] (usually 0.15), Pa is atmospheric pressure [N / m ² ], t is the test time [s], and t ₀ is 60 [ s] and ΔPt are pressure increase values [N / m ² ], and ln is a natural logarithm.
[Expression 1]

[Expression 2]

[0016]
The depressurization of the closed space I is preferably performed until it becomes the same as or equal to the pressure in the outer chamber 3. This is because the air flow in the concrete part C2 (referred to as a part facing the outer chamber 3 of the concrete C) generated by the decompression of the O in the outer chamber 3 is caused by the concrete part C1 (the concrete C of the concrete C) generated by the decompression of the closed space I. This is to prevent the infiltration coefficient and infiltration depth from becoming inaccurate.
[0017]
In order to make the pressure in the closed space I and the pressure in the outer chamber 3 O the same, for example, the forced pressure reducing means and the contact pressure reducing means may be configured by one pressure reducing pump.
[0018]
In the present embodiment, the inner chamber 2A and the outer chamber 3 have a substantially circular cross section and are integrated via the contact main body 2. However, the present invention is not limited to this. The cross section can be appropriately changed to a substantially rectangular shape, an elliptical shape, or the like. Moreover, it can also be set as a different body, without integrating both.
[0019]
(Measurement of compressive strength)
Next, the compressive strength is measured about the test body which measured the penetration coefficient and the penetration depth as mentioned above. For example, in the case of a cylindrical specimen, this measurement can be performed according to JIS A 1108 “Concrete compressive strength test method”. Core and beam cutting method and strength test method ".
[0020]
(Establishment of estimation formula)
When the compressive strength of each specimen is actually measured as described above, regression analysis is performed using the previously measured penetration coefficient and penetration depth, and an estimation formula for estimating the compression strength from the penetration coefficient and penetration depth is obtained.
[0021]
(Measurement of penetration coefficient and penetration depth of target concrete)
In parallel with the above or before and after, at least one of the penetration coefficient and the penetration depth of the target concrete is measured in the present embodiment. This measurement can be performed by the same method as described above using the contact body 1 described above.
[0022]
(Estimation of compressive strength)
When the estimation formula is established as described above and the penetration coefficient and penetration depth of the target concrete are measured, the penetration coefficient and penetration depth are substituted into the estimation formula. Thereby, the compressive strength of concrete is estimated.
[0023]
(Other)
(1) In the above description, the form in which the preparation and curing of the test specimen, the establishment of the estimation formula, and the compression strength estimation of the target concrete are continuously performed has been described. However, the present invention is not limited to this. An estimation formula is established in advance, and the compressive strength of the target concrete can be estimated based on this estimation formula. In this case, it is preferable to facilitate a plurality of estimation formulas specifying the shape, curing environment, and the like.
[0024]
(2) Further, the type of the concrete to be applied in the present invention is not particularly limited. In addition to commonly used concrete such as ordinary concrete, lightweight concrete, and paving concrete, concrete lacking coarse aggregate, that is, mortar can also be used.
[0025]
(3) Furthermore, the shape and presence state of the concrete to which the present invention is applied are not particularly limited. It is also possible to estimate the compressive strength of concrete or concrete products that exist as part of civil engineering structures, building structures, or any other structure.
[0026]
(4) According to this embodiment , it is possible to estimate the compressive strength from the penetration coefficient or the compressive strength from the penetration depth. However, if the compression strength is estimated by comprehensively evaluating both measured values, Is preferred.
[0027]
【Example】
Hereinafter, based on an Example, the correlation with a penetration coefficient and penetration depth, and compressive strength is clarified.
(Creation and curing of specimens)
In this example, specimens were created by changing the target strength, age, shape, and curing environment. Specifically, the target strength of the specimen is 15 (normal), 20 (normal), 30 (normal), 45 (normal), 60 (normal), and 30 (mortar) N / mm ² . did. Moreover, the age of the specimens was set to 10 on the 3rd, 7th, 8th, 14th, 28th, 40th, 48th, 49th, 56th and 365th days. The shape and size of the specimens are: cylindrical specimen (height 20 × φ10 cm), bending specimen (height 15 × 15 × 53 cm, height 15 × 15 × 60 cm), column member (height 60 × 20 × 4 types: 40 cm, height 120 × 20 × 50 cm), floor member (height 20 × 60 × 50 cm, height 20 × 60 × 45 cm, height 20 × 20 × 60 cm, height 20 × 60 × 40 cm), There were 9 types in total. There were five curing environments: underwater curing, in-air curing, curing agent coating curing (application amount 65 g / cm ² or 130 g / cm ² ), wet curing, and outdoor curing.
[0028]
(Measurement of penetration coefficient and penetration depth)
About each specimen, the penetration coefficient and the penetration depth were measured using the contact body 1 shown in the embodiment.
“Vc” is 222 × 10 ⁻⁶ [m ³ ], “A” is 19.6 × 10 ⁻⁴ [m ² ], “μ” is 2.0 × 10 ⁻⁵ [Ns / m ² ], “Ε” was 0.15 [m ³ / m ⁻³ ].
[0029]
(Measurement of compressive strength)
The actual measurement of the compressive strength of each specimen was carried out based on JIS A 1108 for the core specimen (height 20 × φ10 cm) cut out from the specimen, with the cylindrical specimen being left as it was. . A core drill was used for core removal.
[0030]
(Test results and discussion)
FIG. 3 shows the relationship between the penetration coefficient and the core compressive strength, FIG. 4 shows the relationship between the penetration depth and the core compressive strength, the following equation (3) shows the single regression equation for FIG. 3, and the following equation (4). The single regression equation for FIG. 4 is shown, the accuracy of the following equation (3) is shown in FIG. 5, and the accuracy of the following equation (4) is shown in FIG. It can be seen that the compressive strength decreases as the penetration coefficient and penetration depth increase. Therefore, it can be estimated that the smaller the penetration coefficient and penetration depth, the higher the compressive strength of the target concrete. Fc is the core compressive strength (N / mm ² ), K is the penetration coefficient (10 ⁻¹⁶ m ² ), and L is the penetration depth (mm).
[Equation 3]

[Expression 4]

[0031]
(Multiple regression analysis)
The data obtained in the above test was subjected to multiple regression analysis (variable increase / decrease method, F _in = F _out = 2.0). The following equation (5) was obtained from the data based on the penetration coefficient, and the following equation (6) was obtained from the data based on the penetration depth. The accuracy of this equation is shown in FIGS. The core compressive strength Fc (N / mm ² ) is an objective variable, and the penetration coefficient K (10 ⁻¹⁶ m ² ), penetration depth L (mm), curing environment YO (1: in air, 2: curing agent Application (65), 3: Curing agent application (130), 4: Wet, 5: Underwater), Age ZA (day), Shape DAS (1: Floor member, 2: Bending specimen, 3: Cylindrical specimen Column member), measurement location SO (1: upper surface, 2: upper side surface, 3: middle side surface, 4: lower side surface, 5: lower surface) are adopted as explanatory variables (the value in parentheses in the lower part of the formula is the T value, and further N in the lower row is the number of data, R is a multiple correlation coefficient, and _es is the standard deviation of the residual (N / mm ² ).
[Equation 5]

[Formula 6]

[0032]
From these equations, it can be seen that a high degree of correlation can be observed between the penetration coefficient and penetration depth and the compressive strength of the core. Therefore, it can be seen that based on the penetration coefficient or penetration depth, the compressive strength can be estimated relatively easily without being influenced by the state of the concrete surface. It can also be seen that the smaller the penetration coefficient and penetration depth, the lower the measurement location, and the higher the age, the greater the compressive strength.
[0033]
【The invention's effect】
As described above, according to the method of the present invention, the compressive strength of concrete in a structure can be estimated relatively easily without being influenced by the state of the concrete surface.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a contact body.
FIG. 2 is a perspective view of a contact body.
FIG. 3 is a graph showing the relationship between the penetration coefficient and the compressive strength of the core.
FIG. 4 is a graph showing the relationship between penetration depth and core compressive strength.
FIG. 5 is a result value and a calculated value of equation (3).
FIG. 6 is a result value and a calculated value of equation (4).
FIG. 7 is a result value and a calculated value of equation (5).
FIG. 8 is a result value and a calculated value of equation (6).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Contact body, 2 ... Contact body, 2A ... Inner chamber, 3 ... Outer chamber, 4,5 ... Hose, C ... Concrete, I ... Closed space, O ... Outer chamber inner space.

Claims (2)

There is an inner chamber that opens on the concrete surface side in the center of the abutment body, and is connected to the forced decompression means via a hose, and an annular outer chamber that opens on the concrete surface side is formed outside this inner chamber , A contact pressure reducing means is connected to the chamber, and has a contact means configured so that the abutting body comes into close contact with the concrete surface in accordance with the pressure reduction in the outer chamber by the operation of the contact pressure reducing means. When the contact body is brought into close contact with the concrete surface by means, the contact body having a structure in which the inside chamber becomes a closed space,
Applying to the concrete surface of the structure, the contact body is brought into close contact with the concrete surface of the structure by the contact means, and the inside of the inner chamber is decompressed by the decompression means, thereby reducing the concrete of the structure. Both of the penetration coefficient and the penetration depth are measured based on the following formula (1) or the following formula (2), and the compressive strength of the concrete of the structure is estimated from the measured value. A method for estimating the compressive strength of concrete.

In the equation, “kT” is a penetration coefficient [10 ⁻¹⁶ · m ² ], “L” is a penetration depth [mm], and “Vc” is a total air volume [m ³ ] in the inner chamber and the hose. , “A” is the cross-sectional area [m ² ] (theoretical value) of the inner chamber (contact portion with the concrete surface ), “μ” is the kinematic viscosity of air [Ns / m ² ], and ε is the porosity of the concrete. [ M ³ / m ⁻³ ], Pa is the atmospheric pressure [N / m ² ], t is the test time [s], t ₀ is 60 [s], ΔPt is the pressure increase value [N / m ² ], and ln is It is a natural logarithm. The method for estimating the compressive strength of concrete in a structure according to claim 1, wherein it is estimated that the compressive strength of the concrete in the structure is larger as the penetration coefficient and the penetration depth are smaller.

Images