ACI Concrete Field Testing Technician - Grade I Practice Exam

The standard practice for filling a 4 by 8 inch cylinder mold by vibration involves placing the concrete in two equal layers. This method ensures that the concrete is compacted evenly throughout the mold. By using two layers, each layer can be vibrated adequately to remove air pockets and voids, which helps to achieve a uniform and dense sample. Proper compaction enhances the integrity and strength of the cured concrete, making it essential for accurate testing. Filling a single layer may lead to insufficient compaction and potential segregation of the mix, resulting in inconsistent properties in the concrete specimen. Filling the mold with too many layers could complicate the process as it may lead to difficulty in achieving proper compaction in the lower layers, especially with thicker mixtures. Thus, the established method of using two layers effectively balances workability and compaction, making this approach the correct choice.