To control the strain in field-mold

To control the strain in field-molded sealants, manufacturers recommend a reservoir
shape factor (width to depth), and the use of a backer rod as illustrated in Fig. 3.6. The
purpose of the backer rod is to prevent bond at the bottom of the sealant reservoir
where the actual crack in the pavement exists. It is at this crack that the greatest strain
will occur. Typical joint sealants are either asphalt-based or silicone-based