Sunday, December 13, 2009

Expansion Joints, filled and cured in (1) hour

Concrete slabs require joints. These joints, in most cases should be filled to prevent edge break-back and bacterial growths.

From: The Concrete Network: Concrete is not a ductile material—it doesn't stretch or bend without breaking. That's both its greatest strength and greatest weakness. Its hardness and high compressive strength is why we use so much of it in construction. But concrete does move—it shrinks, it expands, and different parts of a building move in different ways.

This is where joints come in. Joints allow one concrete element to move independently of other parts of the building or structure. Joints also let concrete shrink as it dries—preventing what's called internal restraint. Internal restraint is created when one part of a slab shrinks more than another, or shrinks in a different direction. Think how bad you feel when part of you wants to do one thing and another part wants to do something else! Concrete feels the same way.

Although many building elements are designed and built with joints, including walls and foundations, we'll limit this discussion to joints in concrete slabs. In slabs, there are three types of joints:

  • Isolation joints (also sometimes functioning as expansion joints)
  • Construction joints (which can also function as contraction joints)
  • Contraction joints (also sometimes called control joints)
The fastest (sets in one hour), cleanest (no mess, promise) and strongest solution is a (2) part urethane based cartridge filler. These cartridges require a specialized gun (not a caulk gun). Once loaded, you shoot the material into the joint. After one hour you level the joint with a razor scraper (optional) and it's done. These urethane fillers will flex enough to stay in place, yet are strong enough to resist fork-truck wheels pushing down on them. Lastly, they may be your only option for cooler and freezer floors as they are not affected by cold temperatures the way epoxy fillers are.

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