Joint deterioration mechanism and prevention

Q. Some of the saw-cut joints in concrete pavements in my city seem to be spalling after about 10 years in service. What causes this deterioration, and how can it be prevented?

A. Joint deterioration often occurs because of freezing and thawing of saturated concrete and/or the formation of calcium oxychloride compounds in the cement paste due to a reaction with some deicing salts.

Freezing-and-thawing distress can be avoided by preventing saturation of the concrete. The permeability of the paste must be minimized, and the joints should be constructed with effective drainage to avoid the continuous exposure to fluids. Inclusion of sufficient entrained air will reduce the time taken for the paste to become saturated.

Prevention of the formation of calcium oxychloride is most easily achieved by including 25 to 35% supplementary cementitious materials to reduce the amount of calcium hydroxide hydration product in the system. Research also suggests that applications of penetrating sealers to the joints will help to reduce the penetration of aggressive solutions into the faces of the joints.

References: ACI 201.2R-16; ACI 224.3R-95

Topics in Concrete:  Joints, Movement; Pavement; Durability