For joints in concrete, makers list polyurethane, silicone and self-leveling sealants. DAP’s Concrete & Mortar crack filler says not for expansion joints, and a deep joint takes backer rod first.
Where
Painting over it?
What to use
6 products’ makers list this place.
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Crack or joint?
A crack filler and a joint sealant aren’t the same product. DAP’s Concrete & Mortar filler is for cracks and says not for expansion joints. For level joints in driveways and walks, Sika makes Sikaflex + Self Leveling and DAP its AMP Self-Leveling, which DAP says is for horizontal surfaces only.
| Product | Type | Water or rain | Paint |
|---|---|---|---|
| GE Concrete Silicone 2 | 100% silicone | Rain ready in 30 minutes under GE’s conditions, otherwise 8 hours | Not paintable |
| DAP AMP Self-Leveling Concrete | Hybrid sealant | Water ready in 1 hour | Paintable in 1 hour with latex paint |
| DAP Concrete & Mortar Filler & Sealant | Latex caulk | Water ready in 24 hours | Paintable in 2 hours |
| Red Devil PU-970 | Polyurethane sealant | No water-ready time given, full cure in 24 to 48 hours with a 3/16 inch bead | Paintability 2 hours on its data sheet, which also says to paint with premium latex once fully cured |
| Sikaflex + Self Leveling | Polyurethane sealant | 1 week before it sits under water | Paintable after a week’s cure |
| Sikaflex + Construction | Polyurethane sealant | 7 days before it goes under water | Paintable after 7 days |
Each product’s own figures, from its maker’s page or data sheet. Times depend on bead size, temperature and humidity.
Backer rod and wide joints
- Sashco says backer rod goes into joints 1/4 inch wide and 1/2 inch deep or larger, so the sealant can stretch properly.
- Sashco’s Slab takes joints up to 2 inches wide, needs 1 to 3 days before direct rain, and isn’t self-leveling. If you need to drive on it, Sashco suggests covering it with plywood.
Not every caulk goes on concrete. DAP rules out cementitious surfaces for its 100% Silicone Kitchen, Bath & Plumbing and Window, Door & Siding sealants, GE rules out porous concrete for Tub & Tile Silicone 1, and Sashco says Big Stretch isn’t for walking or driving surfaces.
Sika’s safety data sheet for Sikaflex + Construction Sealant carries the signal word “Danger.” It says the sealant “May cause an allergic skin reaction,” “May cause allergy or asthma symptoms or breathing difficulties if inhaled” and “May cause cancer by inhalation.” It notes that its quartz classification applies to quartz dust, including cured sealant that is sanded, ground or cut.
Sika’s safety data sheet for Sikaflex + Self-Leveling Sealant (revised March 2026) also carries the signal word “Danger,” with the same three lines: “May cause an allergic skin reaction,” “May cause allergy or asthma symptoms or breathing difficulties if inhaled” and “May cause cancer by inhalation.” It says to wear protective gloves, eye protection and respiratory protection.
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