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The recrystallization of ettringite in the hardened concrete, due to the moisture
changes and accumulation of reactants, may lead to damages because of the
crystallization pressure and the increase in volume. According to this theory, not all the
ettringite formed causes expansion, since a portion of the ettringite will be deposited in
available voids and cracks, so only the excess will cause expansion. However, there are
two different arguments regarding this theory (1). The first argument indicates that for an
expansion pressure to occur, supersaturation must be achieved and this does not happen
in hydrated cement solution. Another argument points out that this theory does not take
into account the nature of concrete being a semi-brittle material and a partial saturation
might be enough to exert pressure above the concrete tensile strength. A tensile stress
applied at the tip of a crack might be magnified depending on the length and the
geometry of the crack.