Figure 4-6. Concrete placing techniques.
Try to place concrete in even horizontal layers; do not puddle or vibrate it into the form. Place each layer in one
operation and consolidate it before placing the next one to prevent honeycombing or voids, particularly in wall
forms containing considerable reinforcement. Use a mechanical vibrator or a hand spading tool for consolidation.
Take care not to over vibrate because segregation and a weak surface can result. Do not allow the first layer to
take its initial set before adding the next layer. Layer thickness depends on the type of construction, the width of
the space between forms, and the amount of reinforcement. When depositing from buckets in mass concrete
work, the layers should be from 15 to 20 inches thick. For reinforced-concrete members, the layers should be
from 6 to 20 inches thick.
First, place concrete into its final position as nearly as possible. Then work the concrete thoroughly around
reinforcement and embedded fixtures, into the corners, and against the sides of the forms. Because paste tends to
flow ahead of aggregate, avoid horizontal movements that result in segregation.