D-Cracking at a Joint  freeze_cracking
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D-cracking is cracking in concrete pavements caused by freeze-thaw cycles deteriorating the aggregate in concrete.  Water naturally accumulates at the base and sub-base layers under concrete.  When this water suffers from freeze-thaw cycles it wears on the durability of the concrete and begins to crack in the aggregate at the base of the concrete working its way to the surface.  Since the cracking begins beneath the surface it is hard to detect D-Cracking before it becomes visible on the surface of the pavement [a].  This kind of cracking is more susceptible to occur in concrete on ground level such as foundations, roadways, and sidewalks.

Preventative measures can be taken to help avoid D-Cracking such as air-entraining.  This is the addition of air within concrete to allow water to easily expand and contract during freeze-thaw cycles without adding strain to the aggregate in the concrete.  However, increasing the air volume within concrete decreases the strength creating a limit to which this can be used.  Other options are selecting aggregates to be used that perform better in freeze-thaw cycles or reducing the particle size of the aggregates to strengthen the concrete [a].

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