Without proper surface preparation, a concrete repair will be seriously compromised and the possibility of an immediate or long-term failure will be greatly increased.
The International Concrete Repair Institute (ICRI) has published Technical Guideline No. 310.3, “Guide for the Preparation of Concrete Surfaces for Repair Using Hydrodemolition Methods.”
While surface preparation techniques are discussed in the earlier ICRI Technical Guideline No. 310.2 “Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, Polymer Overlays, and Concrete Repair”, this new guideline focuses specifically on the use of hydrodemolition for concrete removal and surface preparation.
Hydrodemolition is the only non-mechanical method of removing deteriorated concrete in preparation for a repair material or overlay, and has been in use in the US for over twenty years, and has been widely accepted for over fifteen years.
Engineers and many State Departments of Transportation specify hydrodemolition for concrete removal because they recognize the significant improvement in bond strength over impact methods of removal.
The quality of the surface preparation insures the long-term success and durability of the concrete repair.
Mechanical removal equipment, such as jackhammers and rotomills, impact the repair surface causing micro-fractures, which can extend ¼-inch to ½-inch into the surface. Those fractures damage the substrate thereby weakening it and reducing the bond strength. In fact, direct tensile bond tests show bond failure with tensile strengths only a fraction (10% – 50%) of the tensile strength of either the substrate or the repair material.
Hydrodemolition does not fracture the substrate. The coarse aggregate is exposed yet unharmed. For partial-depth removal and scarification, the surface texture is rough and the partially-exposed aggregate protrudes to create excellent bond with the repair material. Direct tensile tests typically show failure deep within the existing substrate, which is often the weaker of the two materials, and not at the bond line.
ICRI’s Technical Guideline No. 310.3 contains information on the entire hydrodemolition process, including:
- Benefits and limitations;
- The system and how it works;
- Issues to consider when using hydrodemolition;
- Wastewater control;
- Debris cleanup and disposal;
- Test areas and methods of measuring the removal.
The new guideline explores other benefits of hydrodemolition, such as:
- Deteriorated concrete is selectively removed;
- Reinforcement is cleaned and undamaged;
- Structural vibration is minimal;
- Dust (silicosis) is minimized;
- The construction time can be accelerated;
- Robotic equipment reduces job site injuries.
As ICRI and the concrete repair industry look to the future, the technical guideline illustrates how hydrodemolition improves the quality of the repair, is less labor intensive, and improves the work environment. That’s why Rampart Hydro recommends Technical Guideline No. 310.3 as an excellent source of information about the hydrodemolition process and how it improves the quality and durability of reinforced concrete repairs.