One of the longest and ongoing debates in the concrete repair industry is which type of material should be used to repair cracks in concrete. The number of choices are numerous ranging from cementitious products, mortars with polymer base, methacrylate, epoxies, asphalt based, etc, etc.
Understanding the type of cracking and the cause of cracking is crucial in a successful repair of concrete.
For instance: if a control joint is designed, you must honor the control joint as such. In this case you will likely choose a high elongation material. One common misconception is that all cracks are moving, so we should allow for that movement. This of course is only half right. All cracks do move because they are allowed to move, but not necessarily because they need to move for concrete to function as designed.
The behavior of material in cracks and .004 is initially the same whether material is high modulus or low modulus. (see A.C.I. Cracks Evaluation and Repair)
Whether you allow for a given movement or structurally bond, the biggest enemy is too much movement or movement that compounds and fatigues repair material. Hundreds of material companies now manufacture 1 and 2 component injection systems epoxy based, polyurethane grout, etc. Yet they all depend on a single plane and are subject to many different forces.
The use of cross-stitching or stitching dogs always made sense allowing the transference of load from crack and crack material. However it was not widely used unless an engineer specified it in on large structural cracks.
Repairing a crack in concrete and not reinforcing for tensile capacity is the same as pouring residential foundations without steel. The steel gives the foundation tensile that the concrete lacks. Let's examine: concrete cracks due to lack of tensile and we will fix it without adding tensile strength. What will happen?
I believe that several factors discouraged adding stitching dogs or steel staple rods. Primarily time, labor costs and lack of commercial availability of stitching products. A contractor could purchase injection epoxy, ports, surface seal and injection gun but would have to hunt down steel and cutting tools to install stitches.
The Lack of Stitching and Staples are now a thing of the past
|
