本指引提供混凝土修補所需之相關資訊，包括修補前準備、選擇材料與工法。
相較於前述之 ACI 563-18，該指引提供較詳細的修補法，隨附許多圖說與照片以 利了解。
混凝土結構的修補方法包括結構評估、修補設計、準備施工文件、投標與溝 通過程及進行修補施工，如圖2- 11 所示。首先就表面混凝土移除而言，此為確 保修補年限的最重要因素，過程中不可破壞鄰近混凝土或影響新修補材的握裹，
尤其留意預力鋼筋附近的混凝土。一般移除的方式包括鋸切、衝擊與高壓水柱，
如表2- 39 所示。混凝土移除後，接下來最重要的步驟即為表面處理，只有好的 表面處理下才有好的修補，與移除混凝土的程序及修補材的類型有關，處理的技 術通常包括噴砂(abrasive blasting)、珠粒噴擊(shot-blasting)、噴水(water blasting) 及清潔(cleaning)，如表 2- 40 所示。
本指引介紹數類混凝土修補或修復材料的性質、優缺點、限制、典型用途及 適用規範與參考文獻。其中就本研究所選用的材料而言，傳統砂漿的優點在於其 性質與原混凝土接近，具經濟性，易澆置、粉飾與養護，特別適合局部修補，但 其乾縮量大。高分子改質水泥砂漿(PPCC，polymer-portland-cement concrete)具有 優良的長期性能表現，能抵抗凍融，長時間後較不會發生握裹破壞，亦具低滲透 性。然而其必須於 7-30 °C 間澆置與養護，30 分鐘內完成澆置與粉飾，於現地使 用可能具較高的塑性乾縮。此外，因為其彈性模數較混凝土低，因此用於垂直或 軸向荷重的構材時須特別留意。高分子混凝土與砂漿(polymer concrete and mortar) 係指粒料非由水泥漿而是由高分子材料所膠結。環氧樹脂即為其中之一材料，雖 然貴，但具低乾縮、快速養護、高抗拉、高抗彎及高抗壓強度，與多數的表面具 高黏結，抗凍融，低滲水，適合用於較薄層修補(小於 20 mm)。然而，高溫造成 高分子混凝土與砂漿軟化，須考慮其抗火能力。
修補材料的選擇主要考慮黏結性及抗壓強度，亦包括熱膨脹係數、乾縮、滲 透性、彈性模數、化性、導電性、施工難易、成本、勞工技術、設備及顏色與紋 理。
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圖
2- 11 修補方法
(資料來源：美國混凝土學會，2014)
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表
2- 39 混凝土移除法的特色、考量與限制
Category Features Considerations/limitations
Water-jet cutting (uses perimeter cuts to remove large pieces of concrete)
a) High-pressure water jet without abrasives
b) Applicable for making cutouts through slabs, decks, and other thin concrete members
c) Cuts irregular and curved shapes
d) Makes cutouts without overcutting corners
e) Cuts flush with intersecting surfaces
f) No heat, vibration, or dust is produced
g) Handling of debris is efficient because bulk of
concrete is removed in large pieces
a) Cutouts for removal limited to thin sections
b) Cutting is typically slower and more costly than diamond blade sawing
c) Moderate levels of noise may be produced
d) Controlling flow of waste water may be required
e) Additional safety precautions are required due to the high water pressure produced by the system
f) Does not cut reinforcing steel
Saw cutting (applicable for making cutouts through slabs, decks, and other thin concrete members)
a) Makes precision cuts
b) No vibration is produced
c) Handling of debris is efficient because bulk of
concrete is removed in large pieces
a) Cutouts for removal limited to thin sections
b) Performance is affected by type of diamonds and the
diamond-to-metal bond in blade segments (segment selection is based on aggregate hardness) c) The higher the percentage of steel reinforcement in cuts, the slower and more costly the cutting d) The harder the aggregate, the slower and more costly the cutting
e) Controlling flow of waste water may be required
Diamond wire cutting (applicable for cutting large, thick pieces of concrete)
a) The diamond wire chain can be any length
b) No dust or vibration is produced
c) Large blocks of concrete can be lifted out by a crane or other mechanical methods
d) The cutting operation can be efficient in any direction
a) The cutting chain must be continuous
b) Access to drill holes through the concrete must be available or access around the full section of the structure if the full section is to be cut
c) Water must be available to the chain
d) Controlling the flow of waste water may be required
e) The harder the aggregate or concrete, and the higher the percentage of steel, the slower and more costly the cutting f) Performance is affected by the quality, type, and number of diamonds as well as the diamond-to-metal bond in the chain.
Mechanical shearing (applicable for making cutouts through slabs, decks, and other thin concrete members)
a) Steel reinforcement can be cut
b) Limited noise and vibration are produced
c) Handling of debris is efficient because bulk of concrete is removed in large pieces
a) Limited to thin sections where an edge is available or a hole can be made to start the cut b) Exposed reinforcing steel is damaged beyond reuse c) Remaining concrete is
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Category Features Considerations/limitations
damaged
d) Extremely rugged profile is produced at the cut edge e) Ragged feather edges remain after removal
Stitch drilling
(applicable for making cutouts through concrete members where access to only one face is feasible)
a) Handling of debris is more efficient because bulk of concrete is removed in large pieces
a) Rotary-percussion drilling is more expedient and economical than diamond core drilling;
however, it may result in more damage to the concrete that remains, especially at the point of exit from the concrete
b) Depth of cuts is dependent on accuracy of drilling equipment in maintaining overlap between holes with depth and
diameter of the boreholes drilled.
The deeper the cut, the greater borehole diameter required to maintain overlap between
adjacent holes and the greater the cost
c) Uncut portions between adjacent boreholes will hamper or prevent the removal
d) Cutting reinforced concrete increases the cutting time and increases the cost. Aggregate toughness for percussion drilling and aggregate hardness for diamond coring will affect cutting cost and rate.
e) Personnel must wear hearing protection due to high noise levels.
Impacting (uses repeated striking of the surface with a mass to fracture and spall the concrete)
a) Hand-held breakers
b) Applicable for limited volumes of concrete removal
c) Applicable where blow energy must be limited
d) Widely available commercially
e) Can be used in areas of limited work space
f) Produces relatively small and easily handled debris
a) Performance is a function of concrete soundness and aggregate toughness
b) Significant loss of productivity occurs when breaking action is other than downward
c) Removal boundaries will likely require saw cutting to avoid feathered edges
d) Concrete that remains may be damaged (micro cracking) e) Produces high levels of noise, dust, and vibration
Boom-mounted breakers (appli- cable for full-depth removal of slabs, decks, and other thin concrete members and for surface removal from more massive concrete structures)
a) Can be used for vertical and overhead surfaces
b) Widely available commercially
c) Produces easily handled debris
a) Blow energy delivered to the concrete may have to
be limited to protect the structure being repaired and the
surrounding structures from damage
b) Performance is a function of concrete soundness and aggregate toughness
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Category Features Considerations/limitations
c) Damages remaining concrete d) Damages reinforcing steel e) Produces feathered edges f) Produces high level of noise and dust
(資料來源：美國混凝土學會，2014)
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表
2- 40 表面處理的特色、考量與限制
Category Features Considerations/limitations
Abrasive blasting-Sandblasting (dry/wet)
(uses equipment that propels an abra-size medium at high velocity at the concrete to abrade the surface)
a) Efficient method for roughening the surface and exposing aggregate
b) Cleans reinforcing steel c) Removes surface contamination
a) Dry sandblasting procedure produces large volumes of dust
b) Wet sandblasting is slow
Low-pressure water blasting
(with abrasives)
a) Selectively removes defective concrete
b) Precise control of removal process c) Cleans reinforcing steel while removing concrete
d) Produces minimal damage to remaining concrete
e) Produces no heat or dust f) Abrasives enable jet to cut steel reinforcement and hard aggregates
a) High initial investment b) Additional protection and safety procedures may be required due to water pressure c) Controlling flow of
contaminated waste water may be required
Abrasive blasting-Shot Blasting
a) Efficient method for roughening the surface and exposing aggregate b) Low dust emissions
c) Removes surface contaminants d) Controlled depth of concrete removal
e) Readily available commercially
a) Large units may produce high noise levels
b) High voltage power requirements
Chemical cleaning a) Application of chemicals to remove dirt and contaminants from surface
b) Additional surface preparation may be neces-sary to remove cleaning chemical residue c) Follow cleaning chemical manufacturer's recommendations d) Follow coating manufacturer's instructions
a) Additional surface
preparation may be necessary b) May not be effective in removing all contaminants C) May have strong chemical odor
d) Protection of adjacent area necessary
Acid etching a) Effective in removing cement-based materials
b) Increases porosity of concrete surface
a) Protective clothing is necessary
b) Large amounts of water necessary
c) May permanently stain concrete
d) Protection of adjacent area necessary
e) May contaminate and damage remaining concrete surface
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Category Features Considerations/limitations
Low-pressure water cleaning (without abrasives)
a) Effectively removes surface contaminants without chemical residue
b) Minimal protection of adjacent areas necessary
a) Control of large amounts of water
b) Removal of small amounts of concrete may be noticeable
(資料來源：美國混凝土學會，2014)