The Story of Pittsburgh 
CEMENT anD CONCRETE 
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HILE it is strictly true that the present time is a 
“concrete age,” it is also true that concrete is by 
no means a modern discovery. The present 
extensive use is, however, a quite modern development. 
The word ‘‘concrete” comes from the Latin concretus, 
meaning “that which is grown together,” and artificial 
stone, similar to our concrete, was in use by the Babylon- 
ians and early Egyptians, as well as by the Greeks and the 
Romans. Pliny says the columns which adorn the peristyle 
of the Egyptian labyrinth were made of this material. 
“Puzzolana,” a volcanic earth, was used as a natural 
hydraulic cement by the Romans, who used it in building 
aqueducts, walls and roads. The pyramid of Ninus in 
the Eternal City was formed of a single block of this mate- 
rial. So also was the tomb of Porsena. which was 30 feet 
wide by 5 feet in height. 
While there are many ancient examples of the use of 
factitious stone, it is nevertheless, true in a very exact 
sense, that this is really the “concrete age.” 
Roads, bridges, houses, industrial buildings, railroad and 
mine construction, water-power developments, a variety of 
products such as drain tile, roofing tile, sewer pipe, building 
block and much ornamental work are of concrete. It is 
almost the only material used for sidewalks and for founda- 
tions of all structures including permanent pavements. 
Concrete is made of (a) sand or screenings, and (b) stone, 
pebbles or slag bound together into a hard, strong mass 
with (¢) portland cement, the strongest binder of such 
materials in commercial use. Concrete utilizes a variety 
of sands, slag, pebbles, crushed stones and other materials 
for construction work, provides an economical, permanent.