Most carbonate particles and grains are biologically precipitated; this can
easily be tested for most limestone by examining the microscopic structure
of the particles. Also, carbonates are usually fossiliferous, which
eliminates them from pre-creation in most current young-earth models.
Thus, the fact that they are particles or grains does not get around the
initial precipitation.
In addition to the heat generated by precipitation of carbonates, there are
myriad other sources of heat that would have to be dealt with if any
significant portion of the geologic column is assigned to a brief time
period (motion of tectonic plates, cooling of magma and lava, radioactive
decay, precipitation of evaporites, freezing of glaciers, ...). Several
possible sources of enough water to flood the globe also involve excessive
heat.
David C.