A numerical study of the flow after impulsive load of a plane material surface is carried out. It is shown that the flow is asymptotically self-similar provided one can neglect the cold components in the equation of state. In this case the effective exponent s(r) = d ln(Xs)/d ln(r), derived from the shock trajectory X s (t) does not depend on the initial pressure pulse and approaches the exponent a of the self-similar problem for time t-* oo. For equations of state containing a cold pressure term, s (r) is larger than a and changes non-monotonically with time. Some features of the flow related to the presence of cold components in pressure and internal energy are discussed.