Air Entrainment and the Fabrication of Concrete Railroad Ties

Handling and vibration can affect the air content of prestressed concrete railroad ties. The amount and variation in vibration experienced in concrete railroad ties were investigated to determine the concrete fabrication conditions typically used. Two methods of fabrication were investigated by measuring the concrete properties and vibration exposure during placement at two concrete tie manufacturing plants. In addition to measuring the vibration distribution in concrete railroad ties, a pair of ties were selected for hardened-air void analyses to determine any variation of air content in relation to the height of the ties. The vibration results indicate the existence of constructive and destructive wave-interferences in tie cavities. These interferences may contribute to large variations in the vibration acceleration throughout the length, depth, and width of concrete crossties during fabrication. This may account for the air-loss across the depth of the ties.