AirSprayTech Academy Certificate Program
Water and Wastewater Protective Coating Systems | Article 19 of 24
Cracks, Joints, Penetrations, Terminations, Edges, and Transitions
Protective systems commonly fail where surfaces move, change direction, meet another material, surround an opening, or come to an end. These locations require designed details—not improvised extra coating.
Details Determine Whether the Barrier Remains Continuous
Broad wall and floor areas are usually easier to prepare, coat, and inspect than corners, joints, penetrations, edges, and terminations. At these details, coating thickness changes, movement becomes concentrated, moisture can enter from behind, and dissimilar materials respond differently to temperature and load.
The lining schedule should include written and drawn details showing exactly how the system continues through or terminates at each condition.
Do Not Treat Every Crack the Same Way
A crack is evidence of movement or stress within the concrete. Before selecting a repair, determine why the crack formed, whether it affects structural performance, whether it leaks, and whether it is still moving.
Filling an active crack with a rigid material can move the failure into the adjacent concrete or tear the lining directly over the repair.
Crack Evaluation
Record and evaluate:
- Crack location, length, width, depth, direction, and pattern
- Whether it extends through the concrete section
- Whether it is dry, damp, actively leaking, or carrying contamination
- Whether one side is vertically or horizontally displaced
- Evidence of reinforcing-steel corrosion
- Relationship to joints, penetrations, corners, supports, and loads
- Changes during temperature, filling, draining, or operating cycles
- Previous repairs and evidence of recurring movement
- Structural significance and need for engineering evaluation
Dormant and Active Cracks
A dormant crack is not expected to experience significant continuing movement after its cause has been corrected or stabilized. It may be suitable for rigid repair when directed by the repair design.
An active crack continues to change in width or position because of thermal movement, loading, settlement, shrinkage, vibration, pressure, or another continuing cause.
Determining whether a crack is active may require monitoring over time and through representative operating or temperature conditions. A crack that appears closed during one inspection may open later.
Structural Cracks Require Professional Evaluation
Cracks associated with displacement, settlement, overload, reinforcement corrosion, loss of section, structural movement, or recurring leakage should be evaluated by the responsible design professional.
A coating contractor should document the condition and perform the approved repair—not independently decide that a structural crack can be corrected with sealant, filler, injection resin, or additional lining thickness.
Epoxy Injection
Epoxy injection may be specified to bond suitable cracks and restore continuity in concrete. It is generally associated with cracks that are sufficiently stable for a rigid repair.
The repair procedure should address:
- Crack suitability and structural purpose
- Moisture and contamination within the crack
- Resin viscosity and pot life
- Port spacing and installation
- Surface sealing and injection sequence
- Injection pressure and evidence of complete filling
- Removal of surface seal and final preparation
- Quality-control verification
Epoxy injection should not be used merely because a crack is visible. Active movement, water flow, contamination, and access limitations can make another repair approach necessary.
Flexible Injection and Water-Control Materials
Polyurethane and other flexible or water-reactive injection grouts may be used to control leakage or fill certain cracks and voids. These products can expand, foam, remain flexible, or react with water depending on formulation.
Stopping visible water does not prove that the crack has been structurally repaired. Injection grout may serve as a water-control component while another material or detail provides structural repair and lining continuity.
Confirm product compatibility with the final lining. Remove surface residue and prepare the repaired area according to the approved procedure.
Routing and Sealing
Routing creates a controlled recess along the crack that can receive an approved sealant or repair material. This method may be used for selected nonstructural cracks, surface sealing, or limited movement accommodation.
The detail should define the recess dimensions, cleaning, primer, backer material, bond breaker, sealant geometry, cure, and transition to the lining.
Smearing sealant over the surface without proper geometry can produce three-sided adhesion, inadequate movement capability, thin edges, and early separation.
Reinforced Membrane Crack Details
A flexible membrane reinforced with fabric, scrim, tape, or fleece may be specified over selected cracks to distribute strain across a wider area.
The detail should establish:
- Crack preparation and underlying repair
- Primer and base material
- Reinforcement type, width, overlap, and orientation
- Complete embedment and saturation
- Required membrane thickness
- Feathering or transition into the field lining
- Expected movement capability and inspection procedure
Know the Type of Joint
Construction and Cold Joints
These occur where concrete placements meet. They may be watertight and stable, or they may leak and move depending on design, waterstop condition, preparation, and construction quality.
Control or Contraction Joints
These are intended to create a planned location for shrinkage movement or cracking. Filling them rigidly and coating continuously can defeat their intended function.
Expansion and Movement Joints
These accommodate movement between structural elements. They normally require a flexible joint system, waterstop, sealant, cover, or engineered membrane detail.
Isolation Joints
These separate slabs, walls, columns, equipment bases, or other components so they can move independently. The lining detail must preserve the required separation.
Do Not Coat Continuously Across a Moving Joint Without an Approved Detail
A rigid coating carried directly across a movement joint will often crack or tear. A flexible coating may also fail if the movement exceeds its installed capability or if the joint concentrates strain into a narrow area.
Use the approved joint detail. If none is provided, stop and request one before continuing.
Sealant-Joint Geometry
Sealant movement depends on proper joint width, depth, adhesion surfaces, backing, and profile. Backer rod or another bond breaker can control depth and prevent adhesion to the bottom of the joint.
Three-sided adhesion restricts the sealant and can cause tearing or bond failure. The joint detail should define the correct width-to-depth relationship and whether the lining terminates at, overlaps, or integrates with the sealant.
Confirm chemical resistance, immersion suitability, primer, cure, movement rating, and compatibility between the sealant and adjacent lining materials.
Waterstops
Embedded waterstops are intended to restrict water passage through joints. A leaking joint may indicate a discontinuous, damaged, displaced, or inadequately embedded waterstop.
Surface coating alone may not correct waterstop failure or hydrostatic leakage. Investigation and repair may require injection, external water control, joint reconstruction, or another engineered procedure.
Pipe and Equipment Penetrations
Penetrations combine several failure risks: different materials, restricted access, sharp angles, movement, leakage paths, corrosion, incomplete consolidation, and difficult film-thickness control.
Evaluate:
- The penetration material and its condition
- Movement, vibration, temperature change, and pressure
- Annular gaps, sleeves, seals, puddle flanges, and waterstops
- Corrosion at steel-to-concrete interfaces
- Existing sealants or incompatible materials
- Required cove, fillet, reinforcement, or flexible transition
- Access for inspection, holiday testing, repair, and future maintenance
Dissimilar-Material Transitions
Steel, concrete, masonry, fiberglass, stainless steel, plastic, grout, sealant, and repair mortar have different surface characteristics and movement. A lining that bonds well to concrete may require different preparation or primer on steel or plastic.
The transition detail should identify:
- Preparation for each material
- Primer or tie-coat for each substrate
- Required overlap onto each surface
- Reinforcement or flexible transition material
- Expected differential movement
- Termination and inspection procedure
Inside Corners
Tight inside corners are difficult to prepare, coat, and inspect. They can trap contamination and create localized stress in a rigid lining.
A specified cove or fillet can create a smooth transition between surfaces, improve application access, reduce stress concentration, and support continuous film thickness. Cove material, radius, preparation, primer, and reinforcement should be defined by the approved detail.
Outside Corners and Edges
Liquid coating tends to pull away from sharp outside edges, producing reduced film thickness. Abrasive preparation can also leave sharp aggregate, fins, or projections that are difficult to cover.
Round, ease, grind, repair, or stripe-coat edges as required. The specified radius and preparation should be established before lining application rather than corrected after holiday testing reveals repeated defects.
Lining Terminations
A lining termination is the location where the protective system ends. Poor terminations permit water, chemicals, or cleaning forces to reach the edge and migrate behind the lining.
Termination methods may include:
- Recessed termination grooves in concrete
- Mechanical termination bars or clamping systems
- Termination beneath flanges, rings, or other protected details
- Reinforced membrane transitions
- Compatible sealant details
- Transitions above the highest expected liquid, splash, or condensation exposure
The termination should be accessible for preparation, application, inspection, and future maintenance whenever practical.
Never Terminate the Lining in the Worst Exposure Zone
A termination placed at the normal liquid line, in a splash zone, beneath a leaking joint, or where condensation collects is exposed to repeated wetting and aggressive service.
Where the design permits, extend the system beyond the severe exposure and terminate it on a sound, accessible surface using an approved detail.
Drains and Flow Channels
Drains, troughs, channels, weirs, and sumps experience concentrated flow, abrasion, ponding, cleaning, and changes in direction. The lining should continue into or terminate at these features according to an approved detail.
Verify slope, cove geometry, drain-ring attachment, clamping, sealant compatibility, lining thickness, and access for inspection. Ponding at a termination can shorten service life.
Create a Detail Schedule
Before mobilization, list every recurring and unique detail:
- Static cracks
- Active cracks
- Construction and cold joints
- Expansion, control, and isolation joints
- Wall-to-floor and wall-to-wall corners
- Pipe, conduit, anchor, and equipment penetrations
- Drains, channels, sumps, and weirs
- Steel-to-concrete and other dissimilar-material transitions
- Lining terminations
- Repairs required when a detail fails inspection
Use a Detail Mockup
A field mockup can demonstrate preparation, primer, crack treatment, reinforcement, cove construction, film thickness, termination, cure, appearance, and inspection.
The accepted mockup gives the applicator and inspector a common reference. Preserve it when practical or document it thoroughly before production work begins.
Inspect Details Before They Are Concealed
Establish hold points for:
- Crack and joint preparation
- Leak-control and injection work
- Backer rod, bond breaker, primer, and sealant installation
- Coves and transition mortars
- Reinforcement before cover coats
- Prepared penetrations and dissimilar materials
- Termination grooves or mechanical attachments
- Completed details before return to service
Contractor’s Field Checklist
- Have all cracks and joints been mapped and classified?
- Has the cause of each significant crack been evaluated?
- Are structural and active cracks supported by approved details?
- Are leaking cracks and failed waterstops properly addressed?
- Is sealant geometry and compatibility defined?
- Are movement joints being preserved?
- Are penetrations cleaned, repaired, and detailed?
- Are dissimilar materials receiving the correct preparation and primer?
- Are inside corners coved and outside edges treated as specified?
- Are terminations located outside the severe exposure where practical?
- Were reinforced details inspected before being concealed?
- Have completed details been tested, repaired, and documented?
Knowledge Check
1. Why should the cause of a crack be identified before repair?
The cause determines whether movement or deterioration will continue and whether the repair should be rigid, flexible, structural, water controlling, or supported by another engineered detail.
2. Should a rigid coating be applied continuously across a movement joint?
Not without an approved detail. Joint movement can crack the coating, damage the adjacent substrate, or tear an improperly designed membrane.
3. Why are penetration details especially vulnerable?
They combine dissimilar materials, restricted access, movement, sharp geometry, possible leakage, corrosion, and difficulty maintaining continuous film thickness.
4. Why should a lining termination be located outside the severe exposure when practical?
Liquid, splash, condensation, chemicals, and cleaning forces can attack the lining edge and migrate behind the system.
Technical References and Further Study
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ACI 224.1R-07, Causes, Evaluation, and Repair of Cracks in Concrete Structures. This guide addresses causes, evaluation, and principal methods used to repair concrete cracking.
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ACI SPEC-548.15-20, Specification for Crack Repair by Epoxy Injection. This specification covers pressure injection of epoxy into concrete cracks that intersect at least one accessible surface.
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ACI RAP-1, Structural Crack Repair by Epoxy Injection. This field-oriented procedure discusses crack suitability, preparation, injection, and evaluation.
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ICRI Guideline No. 210.1R-2016, Guideline for Verifying Field Performance of Epoxy Injection of Concrete Cracks.
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ACI CODE-562-25, Assessment, Repair, and Rehabilitation of Existing Concrete Structures—Code Requirements and Commentary.
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NACE SP0178-2007, Design, Fabrication, and Surface Finish Practices for Tanks and Vessels to Be Lined for Immersion Service. This standard addresses fabrication and surface-finish details relevant to successful lining installation.
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The lining, injection-grout, repair-material, sealant, and joint-system manufacturers’ current technical data sheets, safety data sheets, detail drawings, compatibility statements, cure requirements, and written repair procedures.
Standards, product formulations, and manufacturer requirements may be revised. Confirm current documents and obtain approved details for every crack, joint, penetration, edge, transition, and termination before beginning the work.
Professional responsibility:
This article provides foundational education and does not replace structural evaluation, movement analysis, engineered crack and joint details, manufacturer instructions, or project-specific quality control. When the condition or movement differs from the approved detail, stop work and obtain written direction before concealing it.
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