NASCLA Accredited Commercial General ContractorConcreteMedium
A concrete repair project involves patching spalled concrete on a bridge deck. Before applying the repair material, the existing deteriorated concrete must be thoroughly removed, and the substrate prepared. What is the most critical aspect of substrate preparation for ensuring a durable bond between the existing concrete and the new repair material?
- AApplying a thick layer of cementitious grout as a bond breaker.
- BApplying a high-gloss sealer to the existing concrete surface.
- CLeaving a smooth, troweled finish on the existing concrete.
- DEnsuring the substrate is saturated surface dry (SSD) and free of contaminants.
Show answer & explanationAnswer & explanation
Correct answer: D. Ensuring the substrate is saturated surface dry (SSD) and free of contaminants.
For a strong, durable bond, the substrate must be saturated surface dry (SSD) to prevent it from drawing water out of the repair material prematurely, and it must be free of all contaminants (dust, oil, loose concrete) that could inhibit adhesion.
Why the other options are wrong
- A. A bond breaker is explicitly designed to prevent bonding, which is the opposite of the goal in concrete repair.
- B. A high-gloss sealer would act as a bond breaker, preventing the repair material from adhering to the substrate.
- C. A smooth finish is undesirable; a roughened, textured surface (e.g., CSP 3-6) provides better mechanical interlock for the repair material.
Concrete Repair Substrate Prep
The process of preparing existing concrete surfaces to receive repair materials for optimal bonding.
- Removes deteriorated concrete and contaminants.
- Achieves a rough, sound surface.
- Often requires saturated surface dry (SSD) condition.
Memory trick: Diagnose, Remove, Prepare, Apply, Cure, Protect.