Concrete is an ancient material of construction, ﬁrst used during the Roman Empire, which extended
from about 20 B.C. to 200 A.D. The word concrete is derived from the Roman concretus, meaning to
grow together. Although this early mixture was made with lime, cement, and a volcanic ash material
called pozzolana, concrete today is a sophisticated material to which exotic constitutents can be
added and, with computer-controlled batching, can produce a product capable of achieving 50,000
psi compressive strength....