What should be done to the measure after rodding each layer before adding another layer of concrete?

After rodding each layer of concrete, tapping the sides smartly with a mallet is essential to ensure proper compaction. This action helps to eliminate air pockets and allows the concrete to settle uniformly, which leads to a denser and more robust final product. If air bubbles are trapped within the mixture, they can create weak spots, leading to issues with strength and durability once the concrete sets.

This tapping process allows the concrete to flow better and fill in any voids around the aggregate particles. It also aids in achieving the desired consistency and workability of the concrete before adding subsequent layers. Ensuring that each layer is well-compacted is vital for the structural integrity of the concrete in the end, making this step critical in the concrete pouring process.

The other options do not contribute positively to the quality of the concrete placement. Simply leaving it as is could result in uneven settling. Filling it with water would not only be counterproductive but could also negatively affect the concrete's properties. Covering it tightly does not address compaction and may lead to issues like trapping moisture or creating an uneven surface.