Environmental Engineering Reference
In-Depth Information
made with a cement mixture of lime and pozzolana, a volcanic ash. After
the fall of Rome, knowledge of concrete construction was apparently lost
until late in the eighteenth century. In 1824, an English mason, Joseph
Aspen, patented Portland cement, named after a fine building stone quar-
ried on the Isle of Portland, off the coast of England.This cement was made
from limestone, chalk, and shale, which were combined at extremely high
temperatures in an industrial kiln.
Modern commercial concrete is made from Portland cement, water, and
aggregates.To generate the 2,700˚F temperatures needed to form Portland
cement, high-energy wastes such as scrap tires and waste petroleum prod-
ucts (used motor oil, printing inks, solvents, and paints) can be burned
instead of new fossil fuel.The intense heat entirely consumes the toxic sub-
stances. Thus the very manufacture of cement offers a means of reducing
hazardous waste and landfill. Moreover, concrete normally is made from
locally available natural substances on an as-needed basis and does not have
to be transported to the building site.
Concrete also offers other advantages for building. It is naturally water-
proof and fire resistant. It has great compression strength. Because it can
store and re-radiate heat, it requires 70 percent less energy than wood to
maintain comfortable indoor temperatures in a completed building.
Chemically inert, it does not require any sealers, coatings, or preserva-
tives. It can be colored in its raw state by the addition of natural pig-
ments or other agents. It can also be molded into nearly any desired
form, and the addition of aggregates offers an enormous range of textural
possibilities.
In his experimentation with concrete, Hertz was in distinguished com-
pany. The use of concrete in architecture and even in furniture had been
explored early in the twentieth century by the great inventor Thomas Edi-
son as well as by Schindler and other architects. Edison, in fact, established
a company to produce Portland cement, devised a new kind of industrial
kiln, and made other improvements in the production process. Believing
that low-cost cement housing offered a technical solution to problems of
poverty, Edison patented a system for casting concrete houses from molds,
but his plan for a city of such houses was never carried out.
As a material for furniture, however, Hertz found concrete too heavy.
Searching for lighter alternatives, he began to devise his own mixtures.This
was “almost more alchemy than chemistry at the beginning,” he recalls. “I
didn't want to work with synthetics to make the material so different from
