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Dowel Bar

Smooth steel bars placed across joints to transfer loads while allowing horizontal movement

Dowel bars are smooth steel bars placed across joints to transfer loads while allowing horizontal movement. Unlike rebar, dowels are smooth (not deformed) and coated with bond-breaker so concrete doesn't grip them. This allows slabs to expand, contract, and move horizontally while still transferring vertical loads across the joint.

Why It Matters

Pavement joints need to move—thermal expansion/contraction can't be stopped. But joints also need to transfer loads from one slab to the next to prevent faulting (one slab settling lower than its neighbor). Dowel bars solve this by transferring vertical loads while permitting horizontal movement.

For residential driveways meeting garage floors, dowels prevent the common problem of one side settling while the other stays level. The smooth bars let slabs move independently horizontally but link them vertically to share loads and prevent differential settlement.

Technical Details

Standard dowel specifications:

  • Size: 1/2 inch to 1-1/4 inch diameter depending on slab thickness and loading
  • Length: Typically 18 inches (half on each side of joint)
  • Spacing: 12 inches on center for residential work, closer spacing for heavy loads
  • Material: Smooth steel bar with epoxy coating or grease/sleeve for bond break
  • Positioning: At slab mid-depth, parallel to slab surface and perpendicular to joint

One end of each dowel is anchored firmly in concrete. The other end has a bond-breaker (plastic sleeve, grease, or coating) allowing it to slide freely as the slab moves. This sliding prevents the dowels from locking adjacent slabs together.

For construction joints where slabs pour on different days, dowel baskets position bars precisely. Basket spacing aligns with joint location—critical for proper load transfer. Misaligned dowels can prevent joint movement, causing cracking.

High-strength concrete or heavy traffic may require larger or closer-spaced dowels. Engineering design ensures adequate load transfer without restricting movement.

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