Mass concrete refers to large volumes of concrete where heat generated from cement hydration followed by the temperature rise and volume change must be managed carefully to avoid development of thermal stress and cracking.
According to ACI, mass concrete is defined as “any volume of concrete with dimensions large enough to require that measures be taken to cope with generation of heat from hydration and attendant volume change to minimize cracking.”
Applications of mass concrete generally include large foundations such as mat slabs, retaining walls, thick bridge piers or columns, dams, and heavy footings essentially any structural component whose section size, volume-surface ratio, or geometry could lead to slow heat dissipation and internal heat buildup.
Hence identifying and understanding that a particular pour qualifies as mass concrete is the first step in regulating the thermal behavior, it also signals that standard curing and monitoring methods may not be sufficient to prevent any possible thermal gradient formation, and special measures such as temperature monitoring, cooling pipes, insulation, or staged pours must be necessary implications.
Mass concrete differs from ordinary concrete not because of the mix design, but because of the difference in their thermal behavior over time, which becomes a critical parameter to be regulated when volume is large.
Specifically in mass concrete, the heat generated from cement hydration accumulates internally faster than it can dissipate in the environment due to the large volume and low surface-to-volume ratio.
At the same time the outer surface loses heat to the environment which then creates a temperature gradient (core hotter than surface) that results in thermal stress.
If not quickly and efficiently regulated, such stress can cause severe thermal crack development, and compromise the durability, structural continuity, and long-term performance.
Guidance from ACI’s mass concrete practice (e.g., ACI 207.1R-05) emphasizes that the defining characteristic of mass concrete is this thermal behavior that is the need to manage heat generation and volume change due to hydration.
Special attention must be given to such thermal gradient zones by implementing Mass concrete temperature monitoring Methods to precisely map such zones and implement the necessary preventive measures to avoid compromisations with durability, strength maturity and structural integrity.
