A floor joint is an interruption in an otherwise smooth surface. In an industrial floor, the joint needs to be protected from hard wheels. By filling rather than sealing it, you protect the edges of the joint from damage.
Floors must be able to withstand abuse from impact, concentrated loads, and abrasion at the most vulnerable part--the joint. Delayed shrinkage is the other major enemy. Studies show that major slab-on-grade shrinkage can occur long after concrete is placed. To perform well, a joint system must accommodate these late movements.
REQUIREMENTS FOR AN INDUSTRIAL FLOOR JOINT SYSTEM THAT WORKS
A good industrial floor joint system resists hard-wheel loadings and tolerates delayed joint opening. To do this the system must be: invisible, forgiving, durable, and practical.
JOINT PROBLEMS IN INDUSTRIAL FLOORS
Despite heavy educational efforts by ACI, PCA, and others, some floors are still built with joint systems not suited for industrial use. These systems are: left-in-place metal keys; plastic crack-inducing strips; elastomeric joint fillers; and "macho" epoxies.
THE INDUSTRY STANDARD JOINT SYSTEM
Saw-cut joints filled with semi-rigid epoxy best meet requirements for joint performance. The saw cut is narrow. The epoxy has a relatively low strength and a Shore D and A hardness of about 50 and 80, respectively.