What is the purpose of a bonding agent on existing concrete before a new pour?

The purpose of a bonding agent applied to existing concrete before a new pour is to enhance adhesion between the old and new concrete layers. When concrete is poured over an existing surface, without an adequate bonding agent, there is a risk of poor adhesion, which can lead to delamination—the separation of the new concrete from the old.

A bonding agent creates a better cohesive bond, which is crucial for ensuring structural integrity and preventing cracks or failures in the newly poured concrete. This is especially important in applications where the new concrete is intended to act as a continuous structural element with the existing concrete. The bonding agent helps to fill in the pores and surface irregularities of the existing concrete, providing a rougher texture that improves the mechanical interlock between the layers.

While it might seem that preventing delamination is a relevant outcome of the bonding process, the primary function is to improve adhesion, which is the mechanism through which delamination can be avoided. The other options, such as increasing curing time or improving color uniformity, are not directly related to the primary functionality of bonding agents in concrete work.