Right now, silica fumes, a common cement additive long known to strengthen concrete, has been proven to increase the density of cement, and thus the longevity of concrete. However, silica fumes only increase the density of cement by 87 percent. In the paper, the researchers mathematically calculated that the creep could potentially be slowed by as much as two and a half times. At that reduced rate of deformation, concrete currently estimated to last 100 years could last up to 16,000 years. One obvious use for such a long-lasting material would be building structures for containment of nuclear waste; the half-life of plutonium-239 is 24,000 years.