JP3865648B2 - Outside waterproofing method - Google Patents

Description

【００１２】
外防水層２として採用しているポリウレタン系の塗膜防水層は、主剤：硬化剤が重量比１００：７３のポリウレタン系の速硬型吹き付け防水材を、エアーレスポンプ式の吹き付け機により吹き付けることのみで１５〜２０秒程度で硬化して継ぎ目のない塗膜が形成されるものであり、硬化後の引張強度は１０８０Ｎ／ｃｍ²程度、伸び率は６６０％程度（いずれも２０°Ｃの場合）という優れた強度と弾性を有し、３〜５ｍｍ程度の厚さで優れた防水性能を有するものである。
【００１３】
下地層６として採用しているプライマー層は、表１に示すように、第１プライマー、硅砂、第２プライマーからなる。第１プライマーはエポキシ樹脂系のものを採用するが、コンクリート表面が乾燥面（たとえば含水率が８％未満）である場合と湿潤面（同、８％以上）である場合とで主剤と硬化剤の配合比が異なるものを用い、乾燥面用としては主剤：硬化剤を重量比１００：４５の配合とし、湿潤面用としては同１００：１２の配合のものを用いる。硅砂としては５合硅砂を使用し、第２プライマーとしてはポリウレタン系の一成分型のものを用いる。
【００１４】
外防水層２の形成は以下の工程による。
（１）脱型後にＰコン孔埋め、表面のケレン等の下地処理を行う。ＰコンがＡＢＳ樹脂製の場合にはその表面にアセトンを塗布することで第１プライマーに対して良好な付着性が得られる。
（２）コンクリート面の含水率に応じて第１プライマーとして乾燥面用もしくは湿潤面用のいずれかを選択し、コンクリート表面に０．３〜０．５ｋｇ／ｍ^２程度をローラにより塗布する。なお、コンクリート表面に気泡等により凹凸が生じているような場合において必要であれば、第１プライマーを塗布した後、あるいは第１プライマーとしてのエポキシ系パテ材をコンクリート表面にしごいて表面を平滑にすると良い。
（３）第１プライマー上に硅砂を０．７〜１．０ｋｇ／ｍ^２程度散布する。
（４）第２プライマーを０．０８〜０．１ｋｇ／ｍ^２程度、吹き付けにより塗布する。
（５）ポリウレタン系防水材を３．５〜６．０ｋｇ／ｍ^２程度吹き付けガンにより吹き付け、３〜５ｍｍ程度の厚さの塗膜防水層を形成する。施工済み部とのラップ幅は１００ｍｍ以上とする。膜厚の管理は単位面積当たりの吹き付け量あるいは吹き付け時間を管理することで行う。
【００１５】
上記の外防水層２は、優れた防水性能を有することはもとより、コンクリート表面に対する優れた付着強度（１．５Ｎ／ｍｍ²以上）と、優れた耐摩耗性、耐引っ掻き性能、耐衝撃性を有するものであり、ケーソン１の表面に露出状態で形成しても沈設時に受ける周面摩擦力Ｕｆによって剥離したり大きく損傷を受けるようなことがなく、したがって従来においては不可能とされていたケーソン工法への外防水工法の適用を実現し得るものである。しかも上記の外防水層２の形成工程では従来の各種防水層を形成する場合に比べて数倍から十倍程度の施工効率（１２０ｍ²／時間程度）が得られるし、特に第１プライマーとして湿潤面用のものを用いれば気乾養生期間が１日程度の弱齢コンクリートの表面に対しても十分な接着強度を確保することができ、したがってケーソン製作のためのコンクリート打設後に早期に脱型して直ちに外防水層２の施工に着手できるので、ケーソン製作とその沈設工程のサイクルタイムを短縮でき、全体工程の短縮を図ることができる。
【００１６】
上記の外防水層２のコンクリートに対する接着強度、およびケーソン沈設時を想定した耐引っ掻き性を確認するべく、表２に示すような試験を行った。
【００１７】
【表２】

【００１８】
（１）接着強度試験
・試験体
水セメント比５３％、スランプ１０ｃｍのコンクリートを、図２に示すように４６０ｍｍ×５３０ｍｍ×１５０ｍｍの寸法に成型し、打設翌日に脱型した。気乾養生期間を１日、３日、５日とした３種類のコンクリートの両面に、それぞれ表１に示したプライマー層および塗膜防水層からなる防水層を第１プライマーのみを変えて厚さ３ｍｍにて形成し、試験体１１を製作した。
【００１９】
・試験方法
防水層を形成した２日後に、建研式接着力試験器による接着強度試験を次の要領で実施した。
▲１▼ＪＩＳ Ｒ ６２５２−１９７６「研磨紙」に規定する＃１５０を用いて、防水層の表面を目荒らしして清掃する。
▲２▼防水層の表面に、速硬性エポキシ樹脂系接着剤を用いて４ｃｍ×４ｃｍの鋼製アタッチメントを５カ所に貼り付ける。
▲３▼接着剤が硬化した後、ハンドカッターを用いて鋼製アタッチメントに沿ってコンクリートに達するまで切り込みを入れる。
▲４▼建研式接着力試験器を用いて接着強度試験を行い、破壊が生じるまでの最大荷重を測定し、これを接着面積で除して接着強度を算出する。
【００２０】
・試験結果
試験結果を表３に示す。
【表３】

【００２１】
以上の接着強度試験により、以下の事項が確認できた。
▲１▼全ての試験体において接着強度は１．５Ｎ／ｍｍ²と十分に大きく、破壊状態も防水層の破壊とコンクリートの破壊が混在するモードであり、含水率の高い弱齢コンクリートに対しても十分な接着強度が確保されている。
▲２▼図３に示すように、第１プライマーを塗布するまでのコンクリートの気乾養生期間が長くなるに従い、接着強度が若干増加する傾向が認められる。
▲３▼同じく図３に示すように、第１プライマーとして湿潤面用のものを用いた場合、乾燥面用のものの場合よりも接着強度が２０％程度高くなる。
▲４▼破断箇所についてはいずれもコンクリートの破壊が混在するモードであり、試験条件の相異による明確な傾向はない。
【００２２】
（２）耐引っ掻き性試験
・試験体
図４に示すように、接着強度試験に用いた試験体１１と同寸法、同仕様のコンクリートの片面に、乾燥面用プライマーを用いた防水層を形成し、その一部に（ｃ）に示すように端欠け込み処理を施した。防水層の厚さは３ｍｍと５ｍｍの２種類とした。また、一側面に牽引用のフックおよびカバーを取り付けて試験体１２を製作した。
【００２３】
・試験方法
図５および図６に示すように、砂礫層に見立てて握り拳大の石を埋め込んだ人工の試験路盤１６を用意し、その試験路盤１６に防水層が接するように下向きに試験体１２を載せ、試験体１２上に錘１３を載荷して牽引車１４にて横方向に牽引することで防水層に作用する周面摩擦力を再現した。牽引荷重をバネ秤１５で測定して試験体に作用する周面摩擦力とし、それから単位面積当たりの周面摩擦力を求め、その状態での防水層の損傷程度を目視観測した。試験体に載荷する荷重としては、２５０ｋｇ（深度４０ｍの粘性土層における周面摩擦力に相当）、５００ｋｇ（深度２５ｍの砂質土層における周面摩擦力に相当）、７５０ｋｇ（深度４０ｍの砂質土層もしくは深度２５ｍの砂礫層における周面摩擦力に相当）の３段階を設定した。
【００２４】
・試験結果
試験結果を表４に示す。
【表４】

【００２５】
以上の耐引っ掻き性試験により、以下の事項が確認できた。
▲１▼全ての試験体において、プライマー層が露出するような防水層の損傷は引っ張り方向の先端付近において発生している。
▲２▼引っ張り方向の中央部では、最大で幅２．５ｃｍ、長さ５ｃｍ程度に防水層の表面が削り取られ、荒れた状態となってはいるが、プライマー層にまで達する損傷は認められない。
▲３▼全ての試験体において防水層の剥離は生じておらず、接着強度は十分に確保されていると考えられる。
▲４▼防水層の厚さの相異による耐引っ掻き性の相異は認められず、厚さ３ｍｍでも十分な耐引っ掻き性が確保されている。
▲５▼気乾養生期間の相異は耐引っ掻き性に影響を及ぼさず、養生期間１日の弱齢コンクリートの場合であっても十分な耐引っ掻き性が確保されている。
▲６▼本試験では防水層に作用する荷重は実質的に点荷重であるが、実施工では面荷重として作用すると考えられるため、本試験は実施工に比較してより厳しい条件である。以上のことから、上記の接着強度試験との結果も併せて総合的に判断すれば、本外防水工法は少なくとも深度４０ｍ程度までのケーソン工法には支障なく適用することが可能である。
【００２６】
以上、本発明の外防水工法をトンネル施工に際してのニューマチックケーソン工法に適用する場合の実施形態を説明したが、本発明は上記実施形態に限らず、ケーソン工法により様々な建築・土木構造物を施工する際に広く適用できることはいうまでもない。
【００２７】
【発明の効果】
請求項１の発明は、地上部において製作したコンクリート造のケーソンを地盤中に沈設していくケーソン工法に適用される外防水工法であって、ケーソンを沈設していくに先立ち、その外表面にエポキシ樹脂系の第１プライマー、ポリウレタン系の第２プライマーからなるプライマー層を下地層として形成し、その上にポリウレタン系の防水材を吹き付けにより塗布して塗膜防水層を形成するので、ケーソンの外表面に防水性能および信頼性に優れる外防水層を効率的に形成できることはもとより、コンクリートに対する塗膜防水層の接着強度が極めて高く、したがって外防水層がケーソン沈設の際に剥離したり大きな損傷を受けることがなく、その結果、従来においては不可能とされていたケーソン工法への外防水工法の適用が可能である。
【００２８】
請求項２の発明は第１プライマーと第２プライマーの間に硅砂を散布し、請求項３の発明はプライマーとして湿潤面用のプライマーを採用し、ケーソンの外表面が未だ湿潤状態の弱齢コンクリートの段階においてプライマー層を形成し、その上に塗膜防水層を形成するので、含水率の高い弱齢コンクリートに対しても優れた接着強度を確保できるとともに、施工性に優れ工期短縮を図ることができる。
【図面の簡単な説明】
【図１】 本発明をトンネル施工に際してのニューマチックケーソン工法に適用した場合の実施形態を示す概要図である。
【図２】 同、接着強度試験のための試験体を示す図である。
【図３】 同、接着強度と気乾養生期間の関係を示すグラフである。
【図４】 同、耐引っ掻き性試験のための試験体を示す図である。
【図５】 同、耐引っ掻き性試験の概要を示す図である。
【図６】 同、耐引っ掻き性試験の概要を示す図である。
【符号の説明】
１ ケーソン
２ 外防水層（塗膜防水層）
６ 下地層（プライマー層）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an outer waterproof method for forming a waterproof layer on the outer surface of a concrete underground structure during construction of a building / civil engineering structure, and more particularly to an outer waterproof method suitable for application to a caisson method.
[0002]
[Prior art]
As is well known, when waterproofing the underground enclosure, it is more advantageous to secure the waterproof performance by providing the waterproof layer on the outer side than on the inner side. When such an external waterproofing method is applied to the underground outer wall of a normal building, after excavating the ground and constructing the concrete underground outer wall, a waterproof layer is formed on the outer surface of the underground outer wall, and then the surrounding ground The procedure is to backfill.
[0003]
However, in the conventional general waterproofing method as described above, it is indispensable to protect the outer waterproof layer by covering it with a protective layer. That is, if the outer waterproof layer remains exposed without providing a protective layer, there is a concern about damage to the waterproof layer due to stones in the soil during backfilling, and when subsidence occurs after completion It is also assumed that the subsidence force acts as a large scratching force on the outer waterproof layer to cause peeling or damage. And once the outer waterproof layer is damaged, its repair is virtually impossible, so it is indispensable to cover the outer waterproof layer with a strong protective layer in order to prevent such a situation in advance, The provision of such a protective layer requires considerable labor and expense.
[0004]
In addition, the caisson method of constructing a concrete caisson (submersible) manufactured on the ground without substituting the ground is widely used as a construction method for the underground structure. Of course, in the caisson method, it is impossible to form an outer waterproof layer after settling, and even if an outer waterproof layer is formed on the outer surface of the caisson before settling, peeling or breakage will occur when set. For this reason, the external waterproofing method was not applicable to the caisson method.
[0005]
[Problems to be solved by the invention]
In view of the above circumstances, the present invention can eliminate the need for a protective layer for the outer waterproof layer by forming a strong outer waterproof layer on the outer surface of the underground enclosure that is not easily peeled off or damaged. An object of the present invention is to provide an effective waterproofing method that can be applied to the caisson method.
[0006]
[Means for Solving the Problems]
The invention of claim 1 is an external waterproofing method applied to a caisson method in which a concrete caisson manufactured on the ground is submerged in the ground, and before the caisson is submerged, A primer layer comprising an epoxy resin-based first primer and a polyurethane-based second primer is formed as a base layer, and a polyurethane-based waterproofing material is sprayed thereon to form a waterproof coating layer. To do.
The invention of claim 2 is characterized in that, in the outer waterproofing method of the invention of claim 1, dredged sand is sprayed between the first primer and the second primer.
[0007]
The invention of claim 3 is the outer waterproof method of the invention of claim 1 or 2 , wherein the primer for the wet surface is adopted as the primer, and the primer layer is formed at the stage of the aged concrete where the outer surface of the caisson is still wet. And a waterproof coating layer is formed thereon.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment when the outer waterproofing method of the present invention is applied to a pneumatic caisson method will be described. This embodiment is an application example in the case where a concrete caisson 1 as shown in FIG. 1 is sunk during tunnel construction. When the caisson 1 is manufactured on the ground, an outer waterproof layer 2 is formed on the outer surface in advance. The caisson 1 is set in an exposed state without covering the outer waterproof layer 2 with a special protective layer.
[0009]
As shown in FIG. 1, the caisson 1 has a total ground in which the total weight, which is the sum of the outfit load Wo, the water load Ww, and the casing weight Wc, is the sum of the lift pressure Ua, the blade edge resistance force Uc, and the circumferential frictional force Uf Since subsidence occurs when the resistance force is exceeded, the caisson 1 is submerged to a predetermined depth while controlling the balance in this embodiment. Reference numeral 3 in FIG. 1 is a blade edge, 4 is a blade metal fitting, 5 is a thick steel material (flat bar) attached to the leading edge of the blade edge 3 to protect the outer waterproof layer 2 from peeling as required. ).
[0010]
In the present embodiment, the outer waterproof layer 2 provided in an exposed state on the outer peripheral surface of the caisson 1 directly receives the peripheral frictional force Uf from the ground when the caisson 1 is set. Therefore, it is necessary to be firmly bonded to the surface of the caisson 1 and have sufficient scratch resistance so that the peripheral surface frictional force Uf is not peeled off or scraped off. In this embodiment, as the outer waterproof layer 2, a polyurethane-based waterproof coating layer is employed, and as the underlying layer 6, a primer layer mainly composed of an epoxy resin-based primer is employed. Table 1 shows the configuration of the waterproof coating layer as the outer waterproof layer 2 and the primer layer as the foundation layer 6 in the present embodiment.
[0011]
[Table 1]

[0012]
The polyurethane-based coating waterproof layer used as the outer waterproof layer 2 is a polyurethane-based quick-hardening spray waterproofing material having a weight ratio of 100: 73 as a main agent: curing agent is sprayed by an airless pump type spraying machine. Is cured in about 15 to 20 seconds, and a seamless coating film is formed. The tensile strength after curing is about 1080 N / cm ² and the elongation is about 660% (both at 20 ° C.) ) Having excellent strength and elasticity, and having excellent waterproof performance at a thickness of about 3 to 5 mm.
[0013]
As shown in Table 1, the primer layer employed as the underlayer 6 is composed of a first primer, cinnabar sand, and a second primer. The first primer is an epoxy resin type, and the main agent and the curing agent are used when the concrete surface is a dry surface (for example, a moisture content of less than 8%) or a wet surface (8% or more). In the case of a dry surface, the main agent: curing agent is blended at a weight ratio of 100: 45, and for the wet surface, a blend of 100: 12 is used. As the dredged sand, 5 go sand is used, and as the second primer, a polyurethane one-component type is used.
[0014]
The outer waterproof layer 2 is formed by the following steps.
(1) After demolding, P-con hole filling and surface treatment such as kelen on the surface is performed. When Pcon is made of ABS resin, good adhesion to the first primer can be obtained by applying acetone to the surface.
(2) Either a dry surface or a wet surface is selected as the first primer according to the moisture content of the concrete surface, and about 0.3 to 0.5 kg / m ² is applied to the concrete surface with a roller. If there is unevenness on the concrete surface due to air bubbles, etc., if necessary, smooth the surface after applying the first primer or squeezing the epoxy putty material as the first primer on the concrete surface. Good.
(3) Sprinkle sand on the first primer at about 0.7 to 1.0 kg / m ² .
(4) Apply the second primer at about 0.08 to 0.1 kg / m ² by spraying.
(5) A polyurethane waterproof material is sprayed with a spray gun of about 3.5 to 6.0 kg / m ² to form a waterproof coating layer having a thickness of about 3 to 5 mm. The width of the lap with the applied part is 100 mm or more. The film thickness is managed by managing the spraying amount or spraying time per unit area.
[0015]
The outer waterproof layer 2 has not only excellent waterproof performance but also excellent adhesion strength (1.5 N / mm ² or more) to the concrete surface, excellent wear resistance, scratch resistance, and impact resistance. Even if formed on the surface of the caisson 1 in an exposed state, the caisson is not peeled off or greatly damaged by the peripheral frictional force Uf received at the time of setting. Application of the outer waterproofing method to the construction method can be realized. In addition, the process of forming the outer waterproof layer 2 can provide several times to ten times the construction efficiency (about 120 m ² / hour) as compared with the case where various conventional waterproof layers are formed, and is particularly wet as the first primer. If the surface-use material is used, sufficient adhesion strength can be secured even on the surface of aged concrete with an air-drying curing period of about one day. Therefore, demolding is early after placing concrete for caisson production. Then, since the construction of the outer waterproof layer 2 can be started immediately, the cycle time of the caisson manufacture and its setting process can be shortened, and the entire process can be shortened.
[0016]
In order to confirm the adhesion strength of the outer waterproof layer 2 to the concrete and the scratch resistance assuming caisson deposition, tests as shown in Table 2 were performed.
[0017]
[Table 2]

[0018]
(1) Adhesive strength test / test body Concrete with a water cement ratio of 53% and a slump of 10 cm was molded into a size of 460 mm × 530 mm × 150 mm as shown in FIG. Change the thickness of the waterproof layer consisting of the primer layer and the waterproof coating layer shown in Table 1 on both sides of the three types of concrete with an air-drying curing period of 1 day, 3 days, and 5 days. A test body 11 was manufactured by forming the test body at 3 mm.
[0019]
Test Method Two days after the waterproof layer was formed, an adhesive strength test using a Kenken-type adhesive strength tester was performed as follows.
(1) Clean and clean the surface of the waterproof layer using # 150 defined in JIS R 6252-1976 “Abrasive Paper”.
{Circle around (2)} A 4 cm × 4 cm steel attachment is affixed to five locations on the surface of the waterproof layer using a fast-curing epoxy resin adhesive.
(3) After the adhesive is cured, use a hand cutter to cut along the steel attachment until it reaches the concrete.
(4) An adhesion strength test is performed using a Kenken-type adhesive strength tester, the maximum load until fracture occurs is measured, and this is divided by the adhesion area to calculate the adhesion strength.
[0020]
Test results The test results are shown in Table 3.
[Table 3]

[0021]
The following items could be confirmed by the above adhesive strength test.
(1) Adhesive strength is 1.5N / mm ² in all specimens, and the destruction state is a mode in which the destruction of the waterproof layer and the destruction of the concrete are mixed. In addition, sufficient adhesive strength is ensured.
{Circle around (2)} As shown in FIG. 3, it is recognized that the adhesive strength tends to slightly increase as the air-drying curing period of the concrete before applying the first primer becomes longer.
(3) Similarly, as shown in FIG. 3, when a wet primer is used as the first primer, the adhesive strength is about 20% higher than that of a dry primer.
{Circle around (4)} All the fractured parts are in a mode in which concrete fractures coexist, and there is no clear tendency due to differences in test conditions.
[0022]
(2) Scratch resistance test / test body As shown in FIG. 4, a waterproof layer using a dry surface primer is formed on one side of concrete having the same dimensions and specifications as those of the test body 11 used in the adhesive strength test. Then, an edge notching treatment was applied to a part thereof as shown in (c). The thickness of the waterproof layer was 2 types, 3 mm and 5 mm. In addition, a test body 12 was manufactured by attaching a tow hook and cover to one side surface.
[0023]
Test Method As shown in FIGS. 5 and 6, an artificial test roadbed 16 in which a fist-sized stone is embedded as a gravel layer is prepared, and the test body 12 faces downward so that the waterproof layer is in contact with the test roadbed 16. The weight friction 13 acting on the waterproof layer was reproduced by loading the weight 13 on the test body 12 and pulling the weight 13 laterally by the towing vehicle 14. The traction load was measured with the spring balance 15 to obtain the peripheral friction force acting on the test specimen, and the peripheral friction force per unit area was obtained therefrom, and the degree of damage to the waterproof layer in that state was visually observed. The load to be loaded on the test specimen is 250 kg (corresponding to the peripheral friction force in a 40 m deep viscous soil layer), 500 kg (corresponding to the peripheral friction force in a 25 m deep sandy soil layer), 750 kg (40 m deep sand). 3 steps) (corresponding to the peripheral frictional force in the soil layer or the gravel layer with a depth of 25 m).
[0024]
Test results The test results are shown in Table 4.
[Table 4]

[0025]
The following items could be confirmed by the above scratch resistance test.
(1) In all the test specimens, damage to the waterproof layer such that the primer layer is exposed occurs near the tip in the pulling direction.
(2) At the center of the pulling direction, the surface of the waterproof layer is scraped to a maximum of 2.5 cm in width and 5 cm in length, and it is in a rough state, but no damage reaching the primer layer is observed. .
(3) No peeling of the waterproof layer occurred in all the test specimens, and it is considered that the adhesive strength is sufficiently secured.
(4) No difference in scratch resistance due to the difference in the thickness of the waterproof layer is observed, and sufficient scratch resistance is secured even at a thickness of 3 mm.
(5) The difference in the air-drying curing period does not affect the scratch resistance. Sufficient scratch resistance is ensured even in the case of aged concrete with a curing period of one day.
(6) In this test, the load acting on the waterproof layer is substantially a point load, but in the construction work, it is considered to act as a surface load, so this test is a more severe condition than the construction work. From the above, if the results of the above adhesive strength test are also comprehensively judged, the outer waterproofing method can be applied to the caisson method with a depth of at least about 40 m without any problem.
[0026]
As mentioned above, although the embodiment in the case of applying the outer waterproofing method of the present invention to the pneumatic caisson method at the time of tunnel construction has been described, the present invention is not limited to the above embodiment, and various construction and civil engineering structures can be obtained by the caisson method. Needless to say, it can be widely applied during construction.
[0027]
【The invention's effect】
The invention of claim 1 is an external waterproofing method applied to a caisson method in which a concrete caisson manufactured on the ground is submerged in the ground, and before the caisson is submerged, A primer layer consisting of an epoxy resin-based first primer and a polyurethane-based second primer is formed as a base layer, and a polyurethane-based waterproofing material is sprayed thereon to form a waterproof coating layer. In addition to being able to efficiently form an outer waterproof layer with excellent waterproof performance and reliability on the outer surface, the adhesive strength of the coating waterproof layer to concrete is extremely high, so the outer waterproof layer peels off when caisson is laid or is severely damaged As a result, it is possible to apply the outer waterproofing method to the caisson method that was previously impossible.
[0028]
The invention of claim 2 sprays dredged sand between the first primer and the second primer, and the invention of claim 3 employs a primer for a wet surface as a primer, and the caisson outer surface is still wet concrete. In this stage, a primer layer is formed, and a waterproof coating layer is formed on the primer layer. Therefore, it is possible to secure excellent adhesive strength even for aged concrete with a high moisture content, and to improve workability and shorten the construction period. Can do.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an embodiment when the present invention is applied to a pneumatic caisson method for tunnel construction.
FIG. 2 is a view showing a test body for an adhesive strength test.
FIG. 3 is a graph showing the relationship between the adhesive strength and the air-drying curing period.
FIG. 4 is a view showing a specimen for a scratch resistance test.
FIG. 5 is a diagram showing an outline of the scratch resistance test.
FIG. 6 is a diagram showing an outline of a scratch resistance test.
[Explanation of symbols]
1 Caisson 2 Outside waterproofing layer (waterproofing layer)
6 Underlayer (primer layer)

Claims (3)

This is an external waterproofing method applied to the caisson method in which a concrete caisson manufactured in the ground is submerged in the ground, and before the caisson is submerged, an epoxy resin-based first primer on the outer surface An external waterproofing method comprising forming a primer layer comprising a polyurethane-based second primer as a base layer, and spraying a polyurethane-based waterproofing material thereon to form a waterproof coating layer. 2. The outer waterproofing method according to claim 1, wherein dredged sand is sprayed between the first primer and the second primer. 3. The outer waterproofing method according to claim 1 or 2, wherein a primer for a wet surface is used as a primer, a primer layer is formed at a stage of aged concrete where the outer surface of the caisson is still wet, and a waterproof coating is formed thereon. An outer waterproof method characterized by forming a layer.

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