Concrete cover to the steel bars inside a concrete pour is critical to the durability of reinforcement for the structure. Once the Engineer is in doubt, it may require to conduct a Cover Metre Test to verify the as-cast concrete cover to the reinforcement to see whether the condition is acceptable. During casting, the concrete cover is usually maintained by the insertion of cover blocks ( usually made of concrete, epoxy or plastic ) between the formwork and steel bars. However, owing to some cases occurring, the cover of steel bars might be found less than the specified limit during or after the concrete pour. The situations are usually as follows: –
1. The space between the formwork and steel bar is less than the size of the cover block such that the cover block is sheared after force insertion.
2. The cover blocks are disturbed by the internal vibrator, that works too close and displaces the blocks from their original position.
3. The movement of the reinforcement cage might occur during concreting.