Blast Mitigation Coatings
Blast mitigation coatings are spray-applied elastomers used to help reduce fragmentation and debris from walls and structures exposed to explosions. Their use depends on engineering design and testing.
Blast mitigation coatings, also called blast-resistant coatings or explosive-resistant elastomeric retrofits, are spray-applied elastomeric coatings, usually polyurea or polyurea hybrids, applied to walls and structures to help reduce the hazard from fragmentation and flying debris during an explosion. When a blast wave strikes an unreinforced masonry or concrete wall, the wall can break into fragments that travel at high speed into occupied space. A tough, highly elongating coating bonded to the wall can help contain some of that debris. These coatings are one tool within broader blast protection design, which also considers standoff distance, structural strengthening, glazing and building layout.
How they work
The concept relies on the mechanical properties of elastomers (see elastomeric coatings):
- High elongation. The coating stretches significantly before tearing, allowing it to deform with the wall.
- Tensile strength. It resists tearing under rapid loading (see tensile strength and elongation of coating free films).
- Adhesion. Bonding to the wall helps the coating hold fragments together.
- Strain-rate behavior. Many elastomers become stiffer and stronger at very high strain rates, which affects how they respond to blast loads.
The coating acts somewhat like a catcher membrane. Its effectiveness depends on the wall type, blast load, coating thickness, attachment at edges and other design factors.
Typical applications
- Unreinforced masonry walls in military and government buildings.
- Concrete block walls in facilities with explosion risks.
- Industrial facilities handling explosive or flammable materials.
- Critical infrastructure such as utility buildings and control rooms.
- Retrofit projects where structural replacement is impractical.
Coatings may be applied to the interior face of walls (the side facing occupants), the exterior, or both, according to the design.
Materials
Pure polyurea and polyurea hybrids are commonly evaluated for blast mitigation because of their fast cure, toughness and elongation (see polyurea coatings and hybrid polyurea coatings). Formulation matters: properties such as elongation, tensile strength and tear strength vary widely between products (see tear strength of elastomeric coatings). Some manufacturers offer products designated for this use. ArmorThane’s UltraBlast, a polyurea hybrid, is one example positioned for blast mitigation work. Selection should be based on engineering analysis and available test evidence for the specific product.
Some systems combine coatings with fabric reinforcement, mechanical anchoring at edges or other layers.
Testing and design
Blast mitigation performance cannot be inferred from ordinary coating tests. Typical evaluation includes:
- Arena or shock tube tests in which coated wall panels are exposed to controlled explosive loads or simulated blast waves, and damage and debris are measured.
- High strain-rate material testing to obtain properties for analysis.
- Engineering models that predict structural response.
Government agencies and engineering bodies publish criteria and guidance for protective design. Projects typically involve a structural engineer with blast experience who specifies the threat, performance level, coating properties, thickness and attachment details.
Design considerations
- Threat level. The expected charge size and standoff distance.
- Wall type and condition. Masonry, concrete, cracks and existing finishes.
- Coating thickness and coverage, set by design.
- Edge attachment. How the coating is anchored at floors, ceilings, columns and openings. Membranes that are not anchored may peel off as a sheet.
- Openings. Windows and doors often need separate treatment.
- Fire performance. Interior coatings must meet applicable fire code requirements, which may require thermal barriers or fire-rated coverings (see ASTM E84 flame spread testing).
- Finish. Coated walls may be covered with drywall or other finishes.
Surface preparation and application
- Clean the wall to remove dust, efflorescence, oils and loose material (see coating masonry and block).
- Repair large cracks and voids as specified.
- Prime if the system requires.
- Install anchoring hardware or edge details.
- Spray the coating to the specified thickness in multiple passes with suitable plural-component spray equipment.
- Verify thickness, continuity and adhesion.
Quality control
- Thickness checks with gauges or core samples.
- Adhesion testing (see adhesion testing).
- Documentation of batch numbers, equipment settings and conditions.
- Third-party inspection where required.
Because performance depends on correct thickness and attachment, quality control is especially important.
Limitations
- Coatings do not make a building “blast-proof.”
- Results depend on threat, wall and design; performance from one test does not transfer automatically to other conditions.
- Coatings do not replace structural strengthening where it is needed.
- Fire and smoke requirements can limit interior use without protective coverings.
Key terms
- Blast mitigation. Reduction of injury and damage from explosive blast, mainly by holding wall fragments together.
- Fragmentation. Breaking of a wall or structure into flying pieces.
- Elongation. How far a coating stretches before breaking, a key property for this use.
- Retrofit. Adding protection to an existing building.
- Blast testing. Live or simulated blast testing used to validate a system.
Frequently asked questions
Will any polyurea work for blast mitigation?
No. Products vary widely, and design should be based on tested materials and engineering analysis.
Does the coating go on the inside or outside?
It depends on the design. Many retrofits coat the interior face to catch debris, but some coat both sides.
Do blast coatings need to be covered?
Interior applications often need a thermal barrier or finish to meet fire codes.
Related entries
- Polyurea coatings
- Coating masonry and block
- Tensile strength and elongation of coating free films
- Elastomeric coatings
- Hybrid polyurea coatings (new)
- Tear strength of elastomeric coatings (new)
Educational reference. Coating performance varies by formulation. Always follow the manufacturer’s product data sheet, safety data sheet and your project specification.
