What are shrinkage-compensating expansive cement and concrete?

Q. What are shrinkage-compensating expansive cement and concrete?

A. Shrinkage-compensating expansive cement (ASTM C845) is used to make shrinkage-compensating concrete that minimizes cracking tendencies caused by drying shrinkage in concrete slabs, pavements, and structures (ACI 223). When subgrade friction, reinforcement, or other portions of the structure restrain a pavement, floor slab, or structural member during drying shrinkage, tensile stresses develop. Shrinkage- compensating concrete is proportioned so the concrete will increase in volume after setting and during early age hardening. When properly restrained by reinforcement, expansion will induce tension in the reinforcement and compression in the concrete. On subsequent drying, instead of causing a tensile stress that might result in cracking, the shrinkage merely reduces or relieves the compressive strain caused by the initial expansion of the shrinkage-compensating concrete.

References: SP-1(02); E3-13; SP-307; ACI PRC 223-21; ASTM C845

Topics in Concrete: Cementitious Material in Concrete; Durability of Concrete; Materials in Concrete; Shrinkage-Compensating Concrete