JP3683077B2 - Degradation diagnosis method for cured product - Google Patents
Degradation diagnosis method for cured product Download PDFInfo
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- JP3683077B2 JP3683077B2 JP20787297A JP20787297A JP3683077B2 JP 3683077 B2 JP3683077 B2 JP 3683077B2 JP 20787297 A JP20787297 A JP 20787297A JP 20787297 A JP20787297 A JP 20787297A JP 3683077 B2 JP3683077 B2 JP 3683077B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、水硬性材料と導電性材料とを含有する水硬性組成物を硬化させてなる硬化体の劣化診断方法に関するものである。
なお、本発明でいうセメントコンクリートとは、セメントペースト、モルタル、及びコンクリートを総称するものである。
【０００２】
【従来の技術とその課題】
コンクリートで代表される水硬性材料を硬化させてなる硬化体は、長期間の使用により、例えば、温度変化、乾燥、炭酸ガス等のガス、酸性雨中の硫酸イオンや硝酸イオン、海水からの塩分などの化学成分、薬品、並びに、凍結融解等の外的な要因によって、その機能や物性が低下して劣化することが知られている。
これらの劣化は、アルカリ骨材反応、塩害、中性化、乾燥収縮、クリープ、及び凍害等となって現れ、コンクリートの耐久性が低下し、ひび割れや破壊が生じやすくなっている。
【０００３】
従来からこれらの劣化によって生じるひび割れについては、目視で硬化体表面を観察するか、歪みセンサー等を硬化体表面部分に取り付けて検出している。
しかしながら、コンクリート構造物のように大型のものでは、目視による観察は熟練を要する作業の上、人手と手間がかかり、歪みセンサーなどで検出する方法では、その設置に多大な費用を要し、さらにセンサーを埋め込むとその箇所がひび割れや破壊の元になってしまう危険性があるなどの課題があった。
また、いずれの方法においてもコンクリート構造物の表面部分しか調べることができないという課題があった。
【０００４】
一方、従来からセメント等の水硬性材料に対して、炭素繊維等の導電性繊維やカーボンブラック等の導電性粉末を添加して導電性を付与する技術が知られている（特開昭54−113057号公報、特開昭55−9350号公報、及び特開平 1−234347号公報）。
しかしながら、これらの技術はセメント等の水硬性材料に導電性を付与することによる新しい機能の発現を目的としたもので、長期間使用することによる硬化体の変化や劣化に関してはなんら関与するものではなかった。
【０００５】
本発明者は、前記課題を解決すべく、種々検討した結果、特定の材料を配合した硬化体において、特定の検知方法によって、前記課題が解決する知見を得て本発明を完成するに至った。
【０００６】
【課題を解決するための手段】
即ち、本発明は、水硬性材料と、導電性繊維と鉄分を 25 容積％以上含有する粒子からなる導電性材料とを含有する水硬性組成物を硬化させてなり、該導電性材料が硬化体中で連続相を形成し、該硬化体の導電率の減少から硬化体のひび割れによる劣化を診断する硬化体の劣化診断方法であり、水硬性材料と、連続相を形成するしきい値以上でしきい値の５倍以下の量の導電性材料とを含有する水硬性組成物を硬化させてなる硬化体の劣化診断方法であり、該水硬性材料がセメントコンクリートである。
【０００７】
以下、本発明について詳しく説明する。
【０００８】
本発明で使用する水硬性材料としては、セメントを主成分とするもの、水ガラスを主成分とするもの、有機ポリマーを主成分とするもの、カルシウムアルミネートを主成分とするもの、カルシウムアルミネートとセッコウを主成分とするもの、カルシウムアルミネートと同一組成を有する非晶質、並びに、該非晶質とセッコウとを主成分とするもの等が挙げられ、これらの水硬性材料を単独で使用してもよいし、併用してもよく、さらに、骨材等を併用することも可能である。
【０００９】
本発明で使用する導電性材料としては、導電性繊維、及び鉄分を25容積％以上含有する粒子からなるものであり、少ない使用量で導電性が得られる面から導電性繊維の使用が好ましく、安価で強度の向上が得られる面から、また、その使用量が幅広い範囲で本発明の効果が得られる面から鉄分を25容積％以上含有する粒子の使用が好ましい。
【００１０】
導電性繊維としては、ピッチ系やポリアクリロニトリル（ＰＡＮ）系の炭素繊維、これら炭素繊維の原料を高温処理して得られる黒鉛質繊維、及び鋼繊維や黄銅繊維などの金属繊維が挙げられる。
導電性繊維の形状は特に限定されるものではないが、長さ１〜50mm、直径５〜 1,000μｍが作業性の面から好ましい。これよりも、極端に長いか、あるいは短い場合は、繊維の分散不良や導電性能の低下が認められ、好ましくない。
【００１１】
【００１２】
鉄分を25容積％以上含有する粒子（以下導電性粒子という）とは、骨材として使用できるもので、鉄分の含有量が25容積％以上であれば特に制限されるものではない。鉄分の含有量が25容積％未満の粒子では、所定の導電性を得ることが困難となるおそれがある。
ここで、鉄分とは、金属鉄や、マグネタイト等の酸化鉄のような導電性を有するものをいい、導電性粒子とは、鉄分の含有量が金属鉄換算で25容積％以上含有する粒子をいう。
導電性粒子の粒度は特に限定されるものではなく、粒度に応じて使用量を調整することが可能である。
【００１３】
本発明において、導電性材料を併用して、水硬性材料に導電性を付与するためには、導電性材料同士がつながりを有し、導電性材料が硬化体の中で連続相を形成する、いわゆるパーコレーション構造を形成する必要がある。
導電性材料の使用量は、このパーコレーション構造を形成するのに必要最小限の使用量、即ち、しきい値以上で、このしきい値の５倍以下が好ましい。
導電性材料を使用しない硬化体の電気抵抗は、材料によって異なるが概ね10５ Ωcm以上であるが、導電性材料を併用してパーコレーション構造を形成すると、電気抵抗は急激に低下して１〜10２ Ωcmとなる。このときの導電性材料の使用量がしきい値である。
また、本発明は硬化体の一部にひび割れなどの硬化体の劣化が生じたときにパーコレーション構造の割合が減り、導電率が低下する現象を電気抵抗を測定して検出するものであるが、導電性材料のしきい値の５倍を越えると、硬化体の一部に生じるひび割れによるパーコレーション構造の減少する割合が少なく、導電率の低下が少なく、検出が困難になる。従って、導電性材料の使用量はしきい値以上で、しきい値の５倍以下が好ましく、しきい値付近がより好ましい。
導電性材料として導電性繊維を用いる場合、導電性繊維の使用量は、その形状に大きく左右される。例えば、直径0.05mm、長さ10mmのカーボン繊維の使用量は、水硬性材料 100容積部に対して、ほぼ２容積部でパーコレーション構造を形成するため、２〜10容積部が好ましい。
さらに、導電性材料としての導電性粒子を用いる場合、例えば、全鉄分25容積％、粒径 0.3mm以下の電気炉スラグは、水硬性材料 100容積部に対して、100 容積部（全鉄分で換算すると25容積％）でパーコレーション構造を形成するため、本発明の水硬性材料と導電性材料とを含有する水硬性組成物を硬化させてなる硬化体（以下本硬化体という）を作製する場合の導電性粒子の使用量は、水硬性材料 100容積部に対して、 100〜500 容積部が好ましい。
二種類以上の導電性材料を使用する場合は、使用する導電性材料の存在比に比例する使用量で目的とする硬化体が得られる。
【００１４】
本発明では、さらに、必要に応じて骨材を使用することが可能である。
骨材は特に限定されるものでなく、各種砂や砂利を用いることができる。
【００１５】
本発明の導電性材料を含有する水硬性組成物には、さらに、炭酸カルシウム、石英、アルミナ、タルク、シリカフューム、及びパーライト等の充填材、ＡＥ減水剤、高性能減水剤、硬化促進剤、並びに、遅延剤等の混和材料を本発明の目的を阻害しない範囲で添加することが可能である。
【００１６】
本硬化体は、以上の水硬性材料、導電性材料、及び必要に応じて骨材を混合機により混合し、その後水を添加し、水硬させることにより得られる。
その混合に際しては、既存の各種混合機、例えば、傾胴ミキサー、Ｖ型ミキサー、ヘンシェルミキサー、ナウタミキサー、オムニミキサー、及びボールミル等を使用することができる。
【００１７】
さらに、養生方法も特に限定されるものではなく、一般に行われている養生方法が適用可能である。
【００１８】
本硬化体の導電率の減少から硬化体の劣化を診断する方法とは、本硬化体の診断を必要とする箇所に端子を設置し端子間の電気抵抗を測定する方法である。
端子は予め本硬化体中に一部埋め込んで設置しても良いし、本硬化体の表面に接着する形で設置しても良い。
端子に用いる材料は特に限定されるものでなく、本硬化体の導電率を減少するもの以外の材料であれば使用することが可能である。
【００１９】
本発明で測定する電気特性は、直流電気抵抗や交流電気抵抗などであり、測定の簡便さから直流の電気抵抗の測定が好ましく、例えば、市販のデジタルボルトメーターなどが使用可能である。
【００２０】
本発明では、水硬性材料の中性化や凍害などにより、硬化体が劣化し、強度低下がもとで生じるひび割れを診断し、検出するものであり、ひび割れによって本硬化体のパーコレーション構造の割合が減少し、本硬化体の導電率が低下する現象を測定することにより可能である。
本発明の効果を確認する方法として、本硬化体に曲げ応力を負荷することによって生じるひび割れを検出する方法が採用できる。また、破壊には至らない程度の小さい曲げ応力を長時間、繰り返し負荷することにより本硬化体の疲労によって生じるひび割れの検出も可能である。
特に、本硬化体に曲げ応力を負荷することにより、本硬化体に微細なクラックが発生し、導電性材料で形成された本硬化体のパーコレーション構造の割合が減り、電気抵抗が増加することから、本硬化体の劣化を電気抵抗値の増加現象で捉えることが可能である。
また、繰り返し曲げ応力を負荷することにより、長時間にわたって生じる硬化体の劣化を短時間で、しかも実験室で評価することが可能である。
【００２１】
【実施例】
以下、実施例にて本発明を詳細に説明する。
【００２２】
実施例１
セメント675g、表１に示す導電性材料、及び骨材1,350gを市販のモルタルミキサーで10分間混合して水硬性組成物を調製した。
20℃、相対湿度80％の条件下でモルタルミキサーに原料と水 338mlを加え、３分間低速で回転して水硬性組成物のモルタルを作製した。
作製したモルタルを４×４×16cmの型枠に流し込み、そのまま１日養生し、その後、硬化体を型枠から外し、20℃水中で６日間養生し、さらに20℃、相対湿度60％の条件下で７日間養生した硬化体を評価した。結果を表１に示す。
【００２３】
＜使用材料＞
セメント ：市販の普通ポルトランドセメント
導電性材料Ａ：導電性繊維、カーボン繊維、ピッチ系、10mm×φ0.05mm
導電性材料Ｂ：導電性粉末、市販アセチレンブラック、平均粒径40nm
導電性材料Ｃ：導電性粒子、電炉スラグ、全鉄分量25容積％、粒径 0.3mm以下
骨材 ：セメント協会ＩＳＯ 標準砂
【００２４】
＜測定方法＞
電気抵抗 ：作製した４×４×16cmの硬化体の４×４cmの両方の面にアルミ箔を 張り付けて端子とし、スパン10cmの３点曲げ応力を負荷し、短時間で硬化体を 変形させながらその電気抵抗を測定した。
【００２５】
【表１】
実施例２
実施例１と同様に作製した表２に示す硬化体の曲げ強度の50％の曲げ応力を繰り返し負荷し、破壊するまでの繰り返し回数と破壊するまでの電気抵抗の変化を測定した。結果を表２に併記する。
【００２７】
【表２】
【発明の効果】
本発明の水硬性組成物からなる硬化体の電気抵抗を測定し、その変化を調べることにより、容易に水硬性組成物の劣化が原因で生じる硬化体の劣化を診断することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for diagnosing deterioration of a cured product obtained by curing a hydraulic composition containing a hydraulic material and a conductive material.
In addition, the cement concrete as used in this invention is a general term for cement paste, mortar, and concrete.
[0002]
[Prior art and its problems]
Cured bodies made by curing hydraulic materials typified by concrete can be used for a long period of time, for example, temperature changes, drying, gas such as carbon dioxide, sulfate ions and nitrate ions in acid rain, salinity from seawater, etc. It is known that its functions and physical properties are degraded and deteriorated due to external factors such as chemical components, chemicals, and freeze-thaw.
Such deterioration appears as alkali aggregate reaction, salt damage, neutralization, drying shrinkage, creep, frost damage, and the like, and the durability of the concrete is lowered, and cracking and breakage are likely to occur.
[0003]
Conventionally, cracks caused by such deterioration are detected by visually observing the surface of the cured body or attaching a strain sensor or the like to the surface of the cured body.
However, in the case of a large structure such as a concrete structure, visual observation is labor-intensive and labor-intensive, and the method of detecting with a strain sensor or the like requires a great deal of cost for installation. When the sensor was embedded, there were problems such as the risk that the location would be a source of cracks and destruction.
In addition, in any of the methods, there is a problem that only the surface portion of the concrete structure can be examined.
[0004]
On the other hand, a technique for imparting conductivity to hydraulic materials such as cement by adding conductive fibers such as carbon fibers or conductive powder such as carbon black has been known (Japanese Patent Laid-Open No. Sho 54-54). No. 113057, JP-A 55-9350 and JP-A 1-234347).
However, these technologies are intended to develop new functions by imparting electrical conductivity to hydraulic materials such as cement, and are not involved in any change or deterioration of the cured body after long-term use. There wasn't.
[0005]
As a result of various studies to solve the above problems, the present inventor has obtained knowledge that the above problems can be solved by a specific detection method in a cured product containing a specific material, and has completed the present invention. .
[0006]
[Means for Solving the Problems]
That is, the present invention cures a hydraulic composition containing a hydraulic material, a conductive material composed of conductive fibers and particles containing 25 % by volume or more of iron, and the conductive material is cured. Is a method for diagnosing deterioration due to cracking of a cured body from a decrease in electrical conductivity of the cured body, and is a method for diagnosing degradation due to cracking of the cured body, and is above a threshold value for forming a continuous phase with a hydraulic material This is a method for diagnosing deterioration of a cured product obtained by curing a hydraulic composition containing a conductive material in an amount of 5 times or less of a threshold value, and the hydraulic material is cement concrete .
[0007]
The present invention will be described in detail below.
[0008]
Examples of the hydraulic material used in the present invention include those containing cement as the main component, those containing water glass as the main component, those containing organic polymer as the main component, those containing calcium aluminate as the main component, calcium aluminate. And gypsum as a main component, amorphous having the same composition as calcium aluminate, and those having the amorphous and gypsum as main components, and these hydraulic materials are used alone. It may be used in combination, or aggregates may be used in combination.
[0009]
As the conductive material used in the present invention, conductive fibers, which become the 及 beauty iron from particles containing at least 25 volume%, the use of conductive fibers from the surface conductivity is achieved with a small amount preferably From the viewpoint of being inexpensive and improving the strength, and from the viewpoint of obtaining the effects of the present invention within a wide range of use amount, it is preferable to use particles containing 25% by volume or more of iron.
[0010]
Examples of the conductive fibers include pitch-based and polyacrylonitrile (PAN) -based carbon fibers, graphite fibers obtained by high-temperature treatment of these carbon fiber raw materials, and metal fibers such as steel fibers and brass fibers.
The shape of the conductive fiber is not particularly limited, but a length of 1 to 50 mm and a diameter of 5 to 1,000 μm are preferable from the viewpoint of workability. If it is extremely longer or shorter than this, poor dispersion of the fibers and a decrease in the conductive performance are recognized, which is not preferable.
[0011]
[0012]
The particles containing 25% by volume or more of iron (hereinafter referred to as conductive particles) can be used as aggregates, and are not particularly limited as long as the iron content is 25% by volume or more. If the iron content is less than 25% by volume, it may be difficult to obtain predetermined conductivity.
Here, the iron content refers to a material having conductivity such as metallic iron or iron oxide such as magnetite, and the conductive particle refers to a particle whose iron content is 25% by volume or more in terms of metallic iron. Say.
The particle size of the conductive particles is not particularly limited, and the amount used can be adjusted according to the particle size.
[0013]
In the present invention, in order to impart conductivity to the hydraulic material in combination with the conductive material, the conductive materials are connected to each other, and the conductive material forms a continuous phase in the cured body. It is necessary to form a so-called percolation structure.
The amount of the conductive material used is preferably the minimum amount necessary for forming the percolation structure, that is, not less than the threshold value and not more than 5 times the threshold value.
The electric resistance of the cured body not using the conductive material is approximately 10 5 Ωcm or more, although it varies depending on the material. However, when the percolation structure is formed by using the conductive material together, the electric resistance rapidly decreases to 1-10. 2 Ωcm. The amount of the conductive material used at this time is a threshold value.
In addition, the present invention detects the phenomenon that the ratio of the percolation structure decreases when the cured body deteriorates, such as cracks, in a part of the cured body, and the electrical conductivity is measured by measuring the electrical resistance. If it exceeds 5 times the threshold value of the conductive material, the rate of reduction of the percolation structure due to cracks occurring in a part of the cured body is small, the decrease in conductivity is small, and detection becomes difficult. Therefore, the amount of the conductive material used is not less than the threshold value, preferably not more than 5 times the threshold value, and more preferably in the vicinity of the threshold value.
When conductive fibers are used as the conductive material, the amount of conductive fibers used depends greatly on the shape. For example, the amount of carbon fiber having a diameter of 0.05 mm and a length of 10 mm is preferably 2 to 10 parts by volume since the percolation structure is formed by about 2 parts by volume with respect to 100 parts by volume of the hydraulic material.
Furthermore, when using conductive particles as a conductive material, for example, an electric furnace slag having a total iron content of 25% by volume and a particle size of 0.3 mm or less is 100 parts by volume (100% by volume of total iron). In order to form a percolation structure in terms of 25% by volume), when producing a cured body (hereinafter referred to as the main cured body) obtained by curing the hydraulic composition containing the hydraulic material and conductive material of the present invention The amount of the conductive particles used is preferably 100 to 500 parts by volume with respect to 100 parts by volume of the hydraulic material.
When two or more kinds of conductive materials are used, the desired cured product is obtained with a use amount proportional to the abundance ratio of the conductive materials used.
[0014]
In the present invention, an aggregate can be further used as necessary.
The aggregate is not particularly limited, and various types of sand and gravel can be used.
[0015]
The hydraulic composition containing the conductive material of the present invention further includes fillers such as calcium carbonate, quartz, alumina, talc, silica fume and pearlite, AE water reducing agent, high performance water reducing agent, curing accelerator, and It is possible to add an admixing material such as a retarder as long as the object of the present invention is not impaired.
[0016]
This hardened | cured material is obtained by mixing the above hydraulic material, electroconductive material, and aggregate as needed with a mixer, and then adding water and making it hydraulic.
For the mixing, various existing mixers such as a tilt cylinder mixer, a V-type mixer, a Henschel mixer, a Nauta mixer, an omni mixer, a ball mill, and the like can be used.
[0017]
Furthermore, the curing method is not particularly limited, and a generally-used curing method can be applied.
[0018]
The method of diagnosing deterioration of the cured body from the decrease in the conductivity of the cured body is a method of measuring the electrical resistance between the terminals by installing terminals at locations where diagnosis of the cured body is required.
The terminal may be installed by being partially embedded in the main cured body in advance, or may be installed in a form that adheres to the surface of the main cured body.
The material used for the terminal is not particularly limited, and any material can be used as long as it is a material other than the material that decreases the conductivity of the cured body.
[0019]
The electrical characteristics measured in the present invention are DC electrical resistance, AC electrical resistance, etc., and measurement of DC electrical resistance is preferred for ease of measurement. For example, a commercially available digital voltmeter can be used.
[0020]
In the present invention, the cured body is deteriorated due to neutralization or frost damage due to the neutralization of the hydraulic material, and cracks caused by a decrease in strength are diagnosed and detected. Percentage of the percolation structure of the cured body due to the cracks This is possible by measuring the phenomenon that the electrical conductivity of the cured product is reduced.
As a method for confirming the effect of the present invention, a method for detecting a crack generated by applying a bending stress to the cured body can be employed. In addition, it is possible to detect cracks caused by fatigue of the hardened body by repeatedly applying a bending stress small enough not to break down for a long time.
In particular, when a bending stress is applied to the cured body, fine cracks are generated in the cured body, the ratio of the percolation structure of the cured body formed of a conductive material is reduced, and the electrical resistance is increased. The deterioration of the cured product can be grasped by an increase in electric resistance value.
Further, by repeatedly applying a bending stress, it is possible to evaluate the deterioration of the cured body over a long period of time in a laboratory.
[0021]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
[0022]
Example 1
A hydraulic composition was prepared by mixing 675 g of cement, the conductive material shown in Table 1, and 1,350 g of aggregate with a commercially available mortar mixer for 10 minutes.
A raw material and 338 ml of water were added to a mortar mixer at 20 ° C. and a relative humidity of 80%, and the mixture was rotated at a low speed for 3 minutes to prepare a mortar of a hydraulic composition.
The prepared mortar is poured into a 4 × 4 × 16 cm mold and cured for one day, after which the cured product is removed from the mold and cured in water at 20 ° C. for 6 days, and further at 20 ° C. and 60% relative humidity. The cured body cured under 7 days was evaluated. The results are shown in Table 1.
[0023]
<Materials used>
Cement: Commercially available ordinary Portland cement conductive material A: Conductive fiber, carbon fiber, pitch system, 10mm × φ0.05mm
Conductive material B: conductive powder, commercially available acetylene black, average particle size of 40 nm
Conductive material C: Conductive particles, electric furnace slag, total iron content 25% by volume, particle size 0.3mm or less Aggregate: ISO standard sand of the Cement Association [0024]
<Measurement method>
Electrical resistance: Affixed with aluminum foil on both sides of 4x4x16cm of the produced 4x4x16cm hardened body as a terminal, loaded with 3-point bending stress of 10cm span, while deforming the hardened body in a short time The electrical resistance was measured.
[0025]
[Table 1]
Example 2
A bending stress of 50% of the bending strength of the cured body shown in Table 2 produced in the same manner as in Example 1 was repeatedly applied, and the number of repetitions until failure and the change in electrical resistance until failure were measured. The results are also shown in Table 2.
[0027]
[Table 2]
【The invention's effect】
By measuring the electrical resistance of the cured body made of the hydraulic composition of the present invention and examining the change, it is possible to easily diagnose the degradation of the cured body caused by the degradation of the hydraulic composition.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20787297A JP3683077B2 (en) | 1997-08-01 | 1997-08-01 | Degradation diagnosis method for cured product |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20787297A JP3683077B2 (en) | 1997-08-01 | 1997-08-01 | Degradation diagnosis method for cured product |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1151889A JPH1151889A (en) | 1999-02-26 |
| JP3683077B2 true JP3683077B2 (en) | 2005-08-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP20787297A Expired - Lifetime JP3683077B2 (en) | 1997-08-01 | 1997-08-01 | Degradation diagnosis method for cured product |
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| EP3325951B1 (en) * | 2015-07-13 | 2022-04-06 | University of Houston System | Chemo-thermo-piezoresistive highly sensing smart cement with integrated real-time monitoring system |
| JP6673686B2 (en) * | 2015-12-15 | 2020-03-25 | デンカ株式会社 | Mortar panel for salt damage diagnosis of concrete structure and salt damage diagnosis method using the same |
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- 1997-08-01 JP JP20787297A patent/JP3683077B2/en not_active Expired - Lifetime
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| Publication number | Publication date |
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| JPH1151889A (en) | 1999-02-26 |
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