When concrete has deteriorated, delaminated or its chloride content is sufficient to cause corrosion, it should be removed and replaced.
Rather than removing the entire slab, one alternative is partial depth removal, which is defined as exposing a minimum of three-quarters (¾) of an inch of the steel reinforcement.
Generally, contractors have two alternatives when partial concrete removal is specified: hydrodemolition and traditional impact methods using rotomillers and then jackhammers.
While rotomillers and jackhammers have incredible destructive power, that power is difficult to control; so, mistakes happen that can damage both the reinforcing steel and adjacent–and otherwise structurally-sound–concrete. In addition, the vibrations from the equipment can weaken surrounding concrete.
As the diagrams below (mouse-over) illustrate, removing concrete beneath the reinforcing steel can be tricky with impact methods, which do not differentiate between concrete and steel or between sound concrete that should not be removed and deteriorated concrete.
Through its mechanical properties and the differences between concrete and steel, hydrodemolition does treat those materials differently.
That means that Rampart removes concrete from embedded, reinforcing metal without damaging the steel and without accidentally damaging sound concrete. In fact, because the ultra high pressure water jet will remove delaminations and weaknesses beneath the prescribed removal depth, hydrodemolition provides a stronger foundation for repairs thereby increasing the useful life of the road, bridge, or structure.
In additional, partial depth removal via hydrodemolition leaves the surface clean and ready for repair. In many cases, contractors can follow Rampart and immediately install the new surface rather than waiting for old-fashioned mechanical brush cleaning and washing.
Eliminating Delaminations and Shadows
Our powerful hydro jets reach all damaged material, ensuring that no weaknesses or delaminations remain that would otherwise shorten the life of the new surface. (Weak areas cannot withstand the power of Rampart’s ultra high pressure, high-velocity water jets.)
Thus, weak concrete adjacent to and below the specified depth is removed, but the repaired road, bridge or other structure has much more integrity and a longer useful life.
A shadow is the area or volume of concrete that remains under exposed rebar after the initial demolition attempt. It is difficult to remove with traditional, impact methods without damaging the rebar.
As the diagram below shows, shadows are removed during the normal course of hydrodemolition. The angled, yet powerful, water spray does the job, while cleaning, not harming the rebar.
After waterblasting(10,00psi) and vacuuming with a TracVac or other equipment, the rebar remains unharmed, the bonding surface is maximized, and the site is usually ready to be poured.
The photos below are from actual projects. Partial-depth hydrodemolition works on vertical surfaces, too, but regardless of the application or the treatment area–the width and the height–hydrodemolition methods can be precisely controlled thereby minimizing collateral damage–to either good concrete or good rebar.