When filling a standard 4 by 8 inch cylinder mold, how many equal layers should it be filled in?

When filling a standard 4 by 8 inch cylinder mold, it is generally recommended to fill it in two equal layers. This method ensures that the concrete is properly compacted, reducing the risk of voids and improving the strength and durability of the final product.

Filling the mold in two layers allows for better workability as it provides an opportunity to adequately consolidate the concrete in each layer, ensuring that any air bubbles are released. After placing the first layer, it's important to use a tool, such as a tamping rod, to consolidate the concrete and eliminate any trapped air before adding the second layer. This technique leads to a uniformly dense sample, which is critical for accurate testing.

While filling the mold in one layer could be simpler, it may lead to difficulties in achieving proper consolidation throughout the entire volume, increasing the chances of imperfections. More layers than two would generally not be necessary for a mold of this size, as additional layering could complicate the filling process without providing significant benefits for consolidation.