JP4057188B2 - Method for evaluating quality of concrete using ultrasonic waves - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、コンクリートの品質評価方法に関し、さらに詳細には、超音波を用いて既存硬化コンクリートの品質を評価する指標として、水セメント比と細孔量とを求める方法に関する。
【０００２】
【従来の技術】
近年、コンクリート構造物の性能設計に関心が向けられ、コンクリートの劣化予測を精度良く行うことが課題になってきた。そして、コンクリートの品質を評価する方法として、従来、コンクリート打設前のスランプや空気量の測定、およびコンクリート供試体の圧縮強度試験等が用いられているが、これらはフレッシュコンクリートを対象にした評価方法であって、既存構造物のコンクリートには適用することができない。 また硬化後のコンクリートの品質評価方法として、多くの非破壊試験と共に超音波を用いた方法も提案されているものの、超音波を用いた従来方法では、骨材の影響により測定値のばらつきが大きくなり、定性的な評価に留まり、定量的な評価として利用することはできなかった。
【０００３】
【発明が解決しようとする課題】
本発明は上記従来技術の問題点に着目し、これを解決せんとしたものであり、その課題は、既存構造物のコンクリートの品質を、簡単に、しかもコンクリート中の骨材の影響を受けることなく評価する方法を提供することにある。
【０００４】
また別の課題は、既存構造物のコンクリートの超音波伝播速度を計測することにより、コンクリートの品質を示す指標としての有効細孔量、すなわち、骨材以外のコンクリート成分中の細孔量を簡易に求める方法を提供することにある。
【０００５】
さらに別の課題は、既存構造物のコンクリートの超音波伝播速度を計測することにより、コンクリートの品質を示す指標としての水セメント比を求める方法を提供することにある。
【０００６】
【課題を解決するための手段】
上記課題を解決するために、本発明では、セメントペースト、モルタル及びコンクリートからそれぞれ形成された複数の供試体を用いて骨材の影響を除去した修正超音波伝播速度を求めると共に、当該複数の供試体における骨材以外の成分中の細孔量を有効細孔量として求めることにより、前記修正超音波伝播速度と前記有効細孔量の関係式を予め求め、測定対象である既存構造物のコンクリートにおける超音波伝播速度を計測すると共に、該コンクリート中の骨材量と該骨材の超音波伝播速度を求め、前記既存構造物のコンクリートの超音波伝播速度と、該骨材量と、該骨材の超音波伝播速度とを用いて、該コンクリートにおける骨材の影響を取り除いた修正超音波伝播速度の算出値を演算により求め、該修正超音波伝播速度の算出値から、前記関係式を用いて前記既存構造物のコンクリートにおける有効細孔量を求めることを特徴とするコンクリートの品質評価方法を提供する。
【０００７】
ここで、前記細孔量は、セメントペースト、モルタル及びコンクリートにおける単位質量あたりの細孔容量の比であり、セメントペースト、モルタル及びコンクリートの耐久性に大きな影響を及ぼすものである。そして、骨材以外のコンクリート成分中の細孔量、いわゆる有効細孔量が大きいとコンクリートの耐久性は低く、一方、有効細孔量が小さいとコンクリートの耐久性は高いとされており、有効細孔量は０．２５cc／ｇ程度以下が好ましい。
【０００８】
また前記セメント硬化物とは、セメントペースト、モルタル及びコンクリート等のセメントを含む硬化物であって、前記演算式は、例えば、複数の配合でセメント硬化物の供試体を作成し、それぞれの供試体について前記修正超音波伝播速度と前記細孔量とを求めて、この両データから求めても良い。
【０００９】
本発明では、セメントペースト、モルタル及びコンクリートからそれぞれ形成された複数の供試体を用いて骨材の影響を除去した修正超音波伝播速度を求めると共に、当該複数の供試体における水セメント比を求めることにより、前記修正超音波伝播速度と前記水セメント比の関係式を予め求め、測定対象である既存構造物のコンクリートにおける超音波伝播速度を計測すると共に、該コンクリート中の骨材量と該骨材の超音波伝播速度を求め、前記既存構造物のコンクリートの超音波伝播速度と、該骨材量と、該骨材の超音波伝播速度とを用いて、該コンクリートにおける骨材の影響を取り除いた修正超音波伝播速度の算出値を演算により求め、該修正超音波伝播速度の算出値から、前記関係式を用いて前記既存構造物のコンクリートにおける水セメント比を求めることを特徴とするコンクリートの品質評価方法が提供される。
【００１０】
ここで、水セメント比は、コンクリートに含まれるセメントペースト中のセメントに対する水の重量百分率であって、コンクリート強度との間に一定の関係がある。すなわち、水セメント比が小さいとコンクリート強度は大きくなり、一方、水セメント比が大きいとコンクリート強度は小さくなる。また水セメント比と耐久性とは、一般的に密接な関係が有り、海岸など塩分の影響が大きな所では、水セメント比を４５％以下に規定している場合がある。
【００１１】
また、セメント硬化物の修正超音波伝播速度から水セメント比を求める前記演算式は、例えば、複数の配合でセメント硬化物の供試体を作成し、それぞれの供試体について前記修正超音波伝播速度と前記水セメント比とを求めて、この両データから求めても良い。
【００１２】
本発明において、コンクリート中の骨材量は、例えば、該コンクリートの施工時における配合表がある場合には、該配合表から求めることができる。またコンクリート中の骨材量を求める他の方法としては、例えば、既存コンクリート構造物の複数箇所から試料を削り取り、該試料を希塩酸中に浸漬し、残留した骨材を測定することにより求めることもできる。
【００１３】
また本発明において、コンクリート中の骨材の超音波伝播速度は、例えば、該コンクリートの施工時における配合表から施工時に用いた骨材の種類を調べるか、あるいは、既存コンクリート構造物の複数箇所から削り取った試料により骨材の種類を調べる。そして、既存コンクリート構造物に使用されている骨材と同じ種類の岩石から、例えば、直径５０ｍｍ、高さ１００ｍｍ程度の供試体を抜き取って、該供試体を測定して超音波伝播速度を求め、これを以て骨材の超音波伝播速度とすることができる。
【００１４】
【実施例】
以下、実施例を説明するが、本発明はこれに限定されるものではない。
本発明の実施例では、図１に示した手順で既存構造物のコンクリート有効細孔量および水セメント比を求めて、これにより既存構造物のコンクリートの品質を評価する。
〈有効細孔量を算出するための演算式Ａを求める〉
演算式Ａを求めるために、図２に示したような配合で供試体を作成した。図２において、Ｐはセメントペースト、Ｍはモルタル、Ｃはコンクリートから作成された供試体を示し、ＰＡ、ＭＡ及びＣＡはＡＥ剤が混入されたそれぞれの供試体を示す。またＷ／Ｃは水セメント比、Ｗは水の単位量、Ｃはセメントの単位量、Ｓは細骨材の単位量及び、Ｇは粗骨材の単位量を示し、骨材の影響を明瞭にするためにモルタルとコンクリートの骨材量は一定とした。セメントペースト及びモルタルの供試体は直径５０ｍｍ、高さ１００ｍｍの円柱形状に形成し、またコンクリートの供試体は直径１００ｍｍ、高さ２００ｍｍの円柱形状に形成し、各供試体の材齢２８日における超音波伝播速度と細孔量とを測定した。
【００１５】
ここで、超音波センサーは、周波数７５ＫＨｚ、２００ＫＨｚおよび２０ＭＨｚの３種類のものを使用し、供試体長手方向を測定して超音波伝播速度を求め、さらに、モルタルとコンクリートの供試体に関しては、下記の▲１▼式により修正超音波伝播速度を算出した。この修正超音波伝播速度は、超音波伝播速度の測定値から骨材の伝播速度を差し引いて、セメントペーストのみの超音波伝播速度である修正超音波伝播速度を求めたものである。なお、セメントペースト供試体に関しては、超音波伝播速度すなわち修正超音波伝播速度であるため、▲１▼式による算出は行わない。
【００１６】
Ｓｒ＝｛Ｓ−（Ｖａ×Ｓａ）｝／Ｖｐ・・・・・▲１▼式
Ｓｒ：修正超音波伝播速度
Ｓ ：超音波伝播速度の測定値
Ｖａ：骨材の体積比
Ｓａ：骨材における超音波伝播速度の測定値
Ｖｐ：セメントペースト体積比
【００１７】
また細孔量は、セメントペースト、モルタル及びコンクリートにおける単位質量あたりの細孔容量の比であり、水銀圧入法によって求めた。そして、モルタルとコンクリートの供試体に関しては、下記の▲２▼式により有効細孔量を算出した。この有効細孔量は、細孔量を測定した供試体から骨材の質量を取り除いて、セメントペーストのみの細孔量に換算したものであるが、ここでは、測定に用いた供試体のセメントペーストを希塩酸で取り除くことにより、骨材の質量を求めて算定したものである。なお、セメントペースト供試体に関しては、細孔量すなわち有効細孔量であるため、▲２▼式による算出は行わない。
【００１８】
Ｖｅ＝Ｖ0／（１−Ｖａ）・・・・・▲２▼式
Ｖｅ：有効細孔量
Ｖ0 ：細孔量の測定値
Ｖａ：骨材の体積占有率
【００１９】
図３は、以上のように求めたセメントペースト、モルタル、コンクリートの全供試体の修正超音波伝播速度と有効細孔量から作成したグラフである。このグラフからは、有効細孔量が増加するにしたがって、修正超音波伝播速度は低下する傾向にあり、修正超音波伝播速度と有効細孔量とは良好な相関関係にあることが判った。そして、修正超音波伝播速度と有効細孔量に関して、セメントペースト、モルタル、コンクリートの全てに共通する下記の回帰式、すなわち、有効細孔量を算出するための演算式Ａを求めた。
【００２０】
ｙ＝−５６０７1.８ｘ＋４５３１.１・・・・・演算式Ａ
ｙ：修正超音波伝播速度（ｍ／秒）
ｘ：有効細孔量（ｃｃ／ｇ）
【００２１】
〈水セメント比を算出するための演算式Ｂを求める〉
図４は、演算式Ａを求める過程で得られた有効細孔量と、各供試体の水セメント比とから作成したグラフである。このグラフからは、水セメント比が増加するにしたがって、全ての供試体で有効細孔量が増加する傾向にあることが判るが、セメントペースト、モルタル、コンクリートのそれぞれの供試体ごとに得られる回帰式も異なることも判る。図４には、ＡＥ剤が混入されたコンクリート供試体における有効細孔量と水セメント比との回帰式、すなわち、ＡＥ剤混入コンクリートにおいて水セメント比を算出するための演算式Ｂを例示した。
【００２２】
ｙ＝−０.０００２ｘ2＋０.０２３２ｘ−０.４５８５・・・・・演算式Ｂ
ｙ：有効細孔量（ｃｃ／ｇ）
ｘ：水セメント比（％）
なお、演算式Ｂは、コンクリート、ＡＥコンクリート等それぞれの種類に応じて適宜求める。
【００２３】
〈硬化コンクリートの超音波伝播速度を測定する〉
測定対象の既存構造物において、硬化コンクリートの超音波伝播速度を複数箇所で測定する。
【００２４】
〈硬化コンクリートの骨材量を求める〉
次に、測定対象の既存構造物におけるコンクリートの骨材量を、コンクリートの施工時の配合表から求める。ただし、配合表が無い場合には、既存コンクリート構造物の複数箇所から試料を削り取り、この試料のセメントペースト部分を希塩酸で溶かして、残留した骨材の体積を測定することにより、コンクリートにおける骨材の体積比を求めると共に、試料から骨材の体積を差し引いてセメントペーストの体積比を求める。
【００２５】
〈硬化コンクリート中の骨材の超音波伝播速度を算出する〉
また測定対象の既存構造物におけるコンクリート中の骨材の超音波伝播速度を求める。すなわち、コンクリートの施工時の配合表から骨材の種類を調べて、この骨材と同じ種類の岩石から直径５０ｍｍ、高さ１００ｍｍ程度の供試体を抜き取り、超音波伝播速度を測定する。
【００２６】
〈硬化コンクリートの修正超音波伝播速度を算出する〉
以上で求めた、既存構造物における硬化コンクリートの超音波伝播速度の測定値と、骨材の体積比と、骨材の超音波伝播速度の測定値と、セメントペーストの体積比とを、▲１▼式、Ｓｒ＝｛Ｓ−（Ｖａ×Ｓａ）｝／Ｖｐに代入して、硬化コンクリートの修正超音波伝播速度を算出する。
【００２７】
〈演算式Ａから有効細孔量を算出する〉
演算式Ａ、すなわちｙ＝−５６０７1.８ｘ＋４５３１.１における変数ｙに、▲１▼式で算出された硬化コンクリートの修正超音波伝播速度Ｓｒを代入すれば、変数ｘすなわち有効細孔量を算出することができる。
【００２８】
〈演算式Ｂから水セメント比を算出する〉
さらに、演算式Ｂ、例えば、ｙ＝−０.０００２ｘ2＋０.０２３２ｘ−０.４５８５における変数ｙに、演算式Ａで算出された有効細孔量を代入すれば、変数ｘすなわち水セメント比を算出することができる。
【００２９】
なお、水セメント比を算出するためには、演算式Ａと演算式Ｂとの共通変数、すなわち有効細孔量を削除するように、両演算式Ａ,Ｂを予め組み合わせて、修正超音波伝播速度と水セメント比とからなる新たな演算式Ｃを求めて、この演算式Ｃから水セメント比を算出しても良い。
【００３０】
〈コンクリートの品質を評価する〉
最後に、以上のように算出した有効細孔量と水セメント比とから、既存構造物のコンクリートの耐久性や強度を評価する。
【００３１】
なお、本実施例において、演算式Ａ，Ｂは、限定された数量の供試体における修正超音波伝播速度、有効細孔量及び水セメント比のデータから求めたものであるため、多少の誤差を含むものであるが、供試体の配合の種類を増やして、上記方法で演算式Ａ，Ｂを求めれば、この演算式Ａ，Ｂのみならず、既存構造物のコンクリートの評価の精度も更に向上させることができる。
【００３２】
【発明の効果】
本発明では、既存構造物における硬化コンクリートの超音波伝播速度を計測し、硬化コンクリート中の骨材量を求めると共に、この骨材の超音波伝播速度を測定するだけで、予め求めた演算式を用いて、硬化コンクリート中の有効細孔量と水セメント比を算出することができる。したがって、この算出された有効細孔量と水セメント比とから既存構造物のコンクリートの耐久性や強度を簡単に評価することができる。
【００３３】
また本発明では、既存構造物における硬化コンクリート中の骨材量と、この骨材の超音波伝播速度とを求め、これらを用いて、硬化コンクリートの超音波伝播速度の実測値から修正超音波伝播速度を算出するので、骨材の影響による超音波伝播速度のばらつきを低減することが可能になり、したがって、この修正超音波伝播速度から算出した有効細孔量と水セメント比の信頼性の向上も図ることができる。
【図面の簡単な説明】
【図１】既存構造物のコンクリートの有効細孔量および水セメント比を求めるための一実施例のフローチャートである。
【図２】水セメント比と有効細孔量を算出する演算式を求めるために行った実験における供試体の配合表である。
【図３】有効細孔量と修正超音波伝播速度との関係を示すグラフである。
【図４】水セメント比と有効細孔量との関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a concrete quality evaluation method, and more particularly, to a method for determining a water cement ratio and a pore amount as an index for evaluating the quality of an existing hardened concrete using ultrasonic waves.
[0002]
[Prior art]
In recent years, attention has been directed to the performance design of concrete structures, and it has become an issue to accurately predict deterioration of concrete. And, as a method for evaluating the quality of concrete, conventionally, slump before concrete placement, measurement of air volume, compressive strength test of concrete specimen, etc. are used, but these are evaluations for fresh concrete This method is not applicable to concrete in existing structures. In addition, many non-destructive tests and methods using ultrasonic waves have been proposed as methods for evaluating the quality of concrete after hardening, but in conventional methods using ultrasonic waves, the measurement values vary greatly due to the influence of aggregates. Therefore, it was limited to qualitative evaluation and could not be used as quantitative evaluation.
[0003]
[Problems to be solved by the invention]
The present invention focuses on the above-mentioned problems of the prior art and solves this problem. The problem is that the quality of the concrete of the existing structure is easily affected by the aggregate in the concrete. It is to provide a method for evaluation without any problems.
[0004]
Another problem is that by measuring the ultrasonic propagation velocity of concrete in existing structures, it is possible to simplify the effective pore volume as an indicator of concrete quality, that is, the pore volume in concrete components other than aggregates. It is to provide a method to ask for.
[0005]
Yet another object is to provide a method for obtaining a water cement ratio as an index indicating the quality of concrete by measuring the ultrasonic propagation velocity of concrete of an existing structure.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention obtains a corrected ultrasonic wave propagation velocity from which the influence of aggregate has been removed using a plurality of specimens each formed from cement paste, mortar and concrete, and the plurality of specimens. By calculating the amount of pores in the component other than the aggregate in the specimen as the effective pore amount, the relational expression between the corrected ultrasonic wave propagation velocity and the effective pore amount is obtained in advance, and the concrete of the existing structure to be measured The ultrasonic propagation speed in the concrete is measured, the amount of aggregate in the concrete and the ultrasonic propagation speed of the aggregate are obtained, the ultrasonic propagation speed of the concrete in the existing structure, the amount of aggregate, and the bone Using the ultrasonic propagation velocity of the material, the calculated value of the corrected ultrasonic propagation velocity is calculated by removing the influence of the aggregate in the concrete, and from the calculated value of the corrected ultrasonic propagation velocity. It provides a quality evaluation method of the concrete, characterized in that to determine the effective pore volume in the concrete of the existing structure by using the relational expression.
[0007]
Here, the amount of pores is a ratio of pore volume per unit mass in cement paste, mortar and concrete, and has a great influence on the durability of cement paste, mortar and concrete. And if the amount of pores in the concrete components other than aggregate, so-called effective pore amount is large, the durability of concrete is low, while if the effective pore amount is small, the durability of concrete is considered high and effective. The amount of pores is preferably about 0.25 cc / g or less.
[0008]
The hardened cement material is a hardened material containing cement such as cement paste, mortar, and concrete, and the calculation formula includes, for example, a specimen of a hardened cement material with a plurality of blends. The corrected ultrasonic wave propagation velocity and the amount of pores may be obtained from the two data.
[0009]
In the present invention, a corrected ultrasonic propagation velocity is obtained by removing the influence of aggregate using a plurality of specimens each formed from cement paste, mortar and concrete, and a water cement ratio in the plurality of specimens is obtained. Thus, a relational expression between the corrected ultrasonic propagation velocity and the water cement ratio is obtained in advance, and the ultrasonic propagation velocity in the concrete of the existing structure to be measured is measured, and the amount of aggregate in the concrete and the aggregate The ultrasonic propagation speed of the concrete was determined, and the influence of the aggregate in the concrete was removed using the ultrasonic propagation speed of the concrete of the existing structure, the aggregate amount, and the ultrasonic propagation speed of the aggregate. modify determined by calculation calculated value of ultrasonic propagation velocity, Available from calculated values of the corrected ultrasonic propagation velocity, the concrete of the existing structure by using the equation That quality evaluation method of concrete and obtaining the water-cement ratio is provided.
[0010]
Here, the water-cement ratio is a weight percentage of water with respect to the cement in the cement paste contained in the concrete, and has a certain relationship with the concrete strength. That is, when the water cement ratio is small, the concrete strength is increased, whereas when the water cement ratio is large, the concrete strength is decreased. The water-cement ratio and durability are generally closely related, and the water-cement ratio may be regulated to 45% or less in places where the influence of salinity is large such as on the beach.
[0011]
The calculation formula for obtaining the water cement ratio from the corrected ultrasonic propagation speed of the hardened cement material is, for example, creating a specimen of the hardened cement material with a plurality of blends, and the corrected ultrasonic propagation speed and each specimen You may obtain | require the said water cement ratio, and may obtain | require from these both data.
[0012]
In the present invention, the amount of aggregate in the concrete can be obtained from the blending table, for example, when there is a blending table at the time of the concrete construction. In addition, as another method for obtaining the amount of aggregate in concrete, for example, it is also possible to obtain by measuring a residual aggregate by scraping a sample from a plurality of locations of an existing concrete structure, immersing the sample in dilute hydrochloric acid. it can.
[0013]
In the present invention, the ultrasonic propagation speed of the aggregate in the concrete is, for example, by examining the type of aggregate used at the time of construction from the blending table at the time of construction of the concrete, or from a plurality of locations of the existing concrete structure. The type of aggregate is examined using the scraped sample. And, from the same type of rock as the aggregate used in the existing concrete structure, for example, a specimen having a diameter of 50 mm and a height of about 100 mm is extracted, and the ultrasonic propagation velocity is obtained by measuring the specimen. This can be used as the ultrasonic wave propagation speed of the aggregate.
[0014]
【Example】
Hereinafter, although an Example is described, this invention is not limited to this.
In the embodiment of the present invention, the concrete effective pore volume and the water cement ratio of the existing structure are obtained by the procedure shown in FIG. 1, thereby evaluating the quality of the concrete of the existing structure.
<Determining Formula A for Calculating Effective Pore Amount>
In order to obtain the arithmetic expression A, a specimen was prepared with a formulation as shown in FIG. In FIG. 2, P is a cement paste, M is a mortar, C is a specimen prepared from concrete, and PA, MA, and CA are specimens mixed with an AE agent. Also, W / C is the water cement ratio, W is the unit amount of water, C is the unit amount of cement, S is the unit amount of fine aggregate, and G is the unit amount of coarse aggregate. Therefore, the aggregate amount of mortar and concrete was constant. Cement paste and mortar specimens were formed into a cylindrical shape with a diameter of 50 mm and a height of 100 mm, and concrete specimens were formed into a cylindrical shape with a diameter of 100 mm and a height of 200 mm. The speed of sound wave propagation and the amount of pores were measured.
[0015]
Here, the ultrasonic sensor uses three types of frequencies of 75 KHz, 200 KHz and 20 MHz, and measures the longitudinal direction of the specimen to determine the ultrasonic propagation velocity. Further, regarding the specimen of mortar and concrete, The corrected ultrasonic propagation velocity was calculated by the following formula (1). The corrected ultrasonic propagation velocity is obtained by subtracting the aggregate propagation velocity from the measured value of the ultrasonic propagation velocity to obtain a corrected ultrasonic propagation velocity that is an ultrasonic propagation velocity of only the cement paste. Since the cement paste specimen has an ultrasonic wave propagation speed, that is, a corrected ultrasonic wave propagation speed, calculation according to the equation (1) is not performed.
[0016]
Sr = {S− (Va × Sa)} / Vp (1) Formula Sr: Modified ultrasonic propagation speed S: Measurement value of ultrasonic propagation speed Va: Aggregate volume ratio Sa: In aggregate Measured value of ultrasonic propagation velocity Vp: Cement paste volume ratio
The amount of pores is a ratio of pore volume per unit mass in cement paste, mortar and concrete, and was determined by mercury porosimetry. For the mortar and concrete specimens, the effective pore amount was calculated by the following formula (2). This effective pore volume is calculated by removing the mass of the aggregate from the specimen for which the pore volume was measured, and converting it to the pore volume of only the cement paste. Here, the cement of the specimen used for the measurement is used. It is calculated by calculating the mass of aggregate by removing the paste with dilute hydrochloric acid. Since the cement paste specimen is the amount of pores, that is, the amount of effective pores, the calculation by the formula (2) is not performed.
[0018]
Ve = V 0 / (1−Va) (2) Formula Ve: Effective pore volume V 0 : Measurement value of pore volume Va: Volume occupancy rate of aggregate
FIG. 3 is a graph created from the corrected ultrasonic propagation velocity and effective pore volume of all the cement paste, mortar, and concrete specimens obtained as described above. From this graph, it was found that the corrected ultrasonic propagation velocity tends to decrease as the effective pore amount increases, and the corrected ultrasonic propagation velocity and the effective pore amount are in a good correlation. Then, regarding the corrected ultrasonic wave propagation speed and the effective pore amount, the following regression equation common to all cement paste, mortar, and concrete, that is, the arithmetic expression A for calculating the effective pore amount was obtained.
[0020]
y = −56071.8x + 4531.1... Expression A
y: Modified ultrasonic wave velocity (m / sec)
x: Effective pore volume (cc / g)
[0021]
<Obtaining the calculation formula B for calculating the water-cement ratio>
FIG. 4 is a graph created from the effective pore amount obtained in the process of obtaining the arithmetic expression A and the water cement ratio of each specimen. From this graph, it can be seen that the effective pore volume tends to increase in all specimens as the water-cement ratio increases, but the regression obtained for each specimen of cement paste, mortar, and concrete. It can be seen that the formulas are also different. FIG. 4 illustrates a regression equation between the effective pore amount and the water cement ratio in the concrete specimen mixed with the AE agent, that is, an arithmetic expression B for calculating the water cement ratio in the AE agent mixed concrete.
[0022]
y = −0.00002x 2 + 0.0232x−0.4585... Equation B
y: Effective pore volume (cc / g)
x: Water cement ratio (%)
The arithmetic expression B is appropriately determined according to the type of concrete, AE concrete, or the like.
[0023]
<Measure ultrasonic propagation velocity of hardened concrete>
In the existing structure to be measured, the ultrasonic propagation velocity of hardened concrete is measured at multiple locations.
[0024]
<Determining the aggregate amount of hardened concrete>
Next, the aggregate amount of the concrete in the existing structure to be measured is obtained from the composition table at the time of concrete construction. However, if there is no blending table, scrape the sample from multiple locations of the existing concrete structure, dissolve the cement paste part of this sample with dilute hydrochloric acid, and measure the volume of the remaining aggregate. The volume ratio of cement paste is obtained by subtracting the volume of aggregate from the sample.
[0025]
<Calculate the ultrasonic propagation velocity of aggregate in hardened concrete>
In addition, the ultrasonic propagation velocity of aggregate in concrete in the existing structure to be measured is obtained. That is, the type of aggregate is examined from the composition table at the time of concrete construction, a specimen having a diameter of about 50 mm and a height of about 100 mm is extracted from the same type of rock as this aggregate, and the ultrasonic propagation velocity is measured.
[0026]
<Calculate the corrected ultrasonic propagation velocity of hardened concrete>
The measured value of ultrasonic propagation speed of hardened concrete in the existing structure, the volume ratio of aggregate, the measured value of ultrasonic propagation speed of aggregate, and the volume ratio of cement paste are as follows: Substitute into the formula, Sr = {S− (Va × Sa)} / Vp to calculate the corrected ultrasonic propagation velocity of the hardened concrete.
[0027]
<Calculating effective pore volume from equation A>
Substituting the modified ultrasonic wave propagation velocity Sr of the hardened concrete calculated by the equation (1) into the variable y in the arithmetic expression A, that is, y = −56071.8x + 4531.1, the variable x, that is, the effective pore amount is calculated. be able to.
[0028]
<Calculate water cement ratio from equation B>
Further, if the effective pore amount calculated by the arithmetic expression A is substituted for the variable y in the arithmetic expression B, for example, y = −0.00002x 2 + 0.0232x−0.4585, the variable x, that is, the water cement ratio is obtained. Can be calculated.
[0029]
In order to calculate the water cement ratio, the modified ultrasonic wave propagation is performed by combining both the arithmetic expressions A and B in advance so as to delete the common variable of the arithmetic expressions A and B, that is, the effective pore amount. A new arithmetic expression C composed of the speed and the water cement ratio may be obtained, and the water cement ratio may be calculated from the arithmetic expression C.
[0030]
<Evaluating the quality of concrete>
Finally, the durability and strength of the concrete of the existing structure are evaluated from the amount of effective pores calculated as described above and the water cement ratio.
[0031]
In this example, since the arithmetic expressions A and B are obtained from the data of the corrected ultrasonic propagation velocity, the effective pore amount, and the water cement ratio in a limited number of specimens, some errors are caused. Although it is included, if the types of specimens are increased and the calculation formulas A and B are obtained by the above method, not only the calculation formulas A and B but also the accuracy of evaluation of the concrete of the existing structure can be further improved. Can do.
[0032]
【The invention's effect】
In the present invention, the ultrasonic propagation speed of the hardened concrete in the existing structure is measured, the amount of aggregate in the hardened concrete is obtained, and only the ultrasonic propagation speed of this aggregate is measured. It is possible to calculate the effective pore amount and water cement ratio in the hardened concrete. Therefore, the durability and strength of the concrete of the existing structure can be easily evaluated from the calculated effective pore amount and the water cement ratio.
[0033]
Further, in the present invention, the amount of aggregate in the hardened concrete in the existing structure and the ultrasonic propagation speed of the aggregate are obtained, and using these, the corrected ultrasonic propagation is measured from the actual measurement value of the ultrasonic propagation speed of the hardened concrete. Since the velocity is calculated, it is possible to reduce the variation in the ultrasonic propagation velocity due to the influence of the aggregate. Therefore, the reliability of the effective pore volume and the water cement ratio calculated from this modified ultrasonic propagation velocity is improved. Can also be planned.
[Brief description of the drawings]
FIG. 1 is a flowchart of an embodiment for obtaining an effective pore amount and a water cement ratio of concrete of an existing structure.
FIG. 2 is a blending table of specimens in an experiment conducted to obtain an arithmetic expression for calculating a water cement ratio and an effective pore amount.
FIG. 3 is a graph showing the relationship between the effective pore amount and the corrected ultrasonic wave propagation speed.
FIG. 4 is a graph showing the relationship between the water cement ratio and the effective pore amount.
Claims (2)
測定対象である既存構造物のコンクリートにおける超音波伝播速度を計測すると共に、該コンクリート中の骨材量と該骨材の超音波伝播速度を求め、
前記既存構造物のコンクリートの超音波伝播速度と、該骨材量と、該骨材の超音波伝播速度とを用いて、該コンクリートにおける骨材の影響を取り除いた修正超音波伝播速度の算出値を演算により求め、
該修正超音波伝播速度の算出値から、前記関係式を用いて前記既存構造物のコンクリートにおける有効細孔量を求めることを特徴とするコンクリートの品質評価方法。 Obtain the corrected ultrasonic wave propagation velocity that eliminates the influence of aggregate using multiple specimens each formed from cement paste, mortar and concrete, and the amount of pores in components other than aggregate in the multiple specimens Is determined in advance as an effective pore amount, and a relational expression between the corrected ultrasonic propagation velocity and the effective pore amount is obtained in advance
While measuring the ultrasonic propagation velocity in the concrete of the existing structure to be measured, obtain the amount of aggregate in the concrete and the ultrasonic propagation velocity of the aggregate,
Using the ultrasonic propagation velocity of the concrete of the existing structure, the amount of aggregate, and the ultrasonic propagation velocity of the aggregate, the calculated value of the corrected ultrasonic propagation velocity with the influence of the aggregate removed from the concrete is removed. Is obtained by calculation,
A method for evaluating the quality of concrete, characterized in that an effective pore amount in the concrete of the existing structure is obtained from the calculated value of the corrected ultrasonic propagation velocity using the relational expression.
測定対象である既存構造物のコンクリートにおける超音波伝播速度を計測すると共に、該コンクリート中の骨材量と該骨材の超音波伝播速度を求め、
前記既存構造物のコンクリートの超音波伝播速度と、該骨材量と、該骨材の超音波伝播速度とを用いて、該コンクリートにおける骨材の影響を取り除いた修正超音波伝播速度の算出値を演算により求め、
該修正超音波伝播速度の算出値から、前記関係式を用いて前記既存構造物のコンクリートにおける水セメント比を求めることを特徴とするコンクリートの品質評価方法。 The modified ultrasonic wave velocity is obtained by removing the influence of the aggregate using a plurality of specimens each formed from cement paste, mortar, and concrete, and the correction is performed by obtaining the water cement ratio in the plurality of specimens. Obtain a relational expression between the ultrasonic propagation speed and the water cement ratio in advance,
While measuring the ultrasonic propagation velocity in the concrete of the existing structure to be measured, obtain the amount of aggregate in the concrete and the ultrasonic propagation velocity of the aggregate,
Using the ultrasonic propagation velocity of the concrete of the existing structure, the amount of aggregate, and the ultrasonic propagation velocity of the aggregate, the calculated value of the corrected ultrasonic propagation velocity with the influence of the aggregate removed from the concrete is removed. Is obtained by calculation,
A method for evaluating the quality of concrete, wherein a water cement ratio in the concrete of the existing structure is obtained from the calculated value of the corrected ultrasonic propagation velocity using the relational expression.
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