Introduction
"Concrete" is a name applied to any of a number of compositions
consisting of sand, gravel, crushed stone, or other coarse material,
bound together with various kinds of cementitious materials, such
as lime or cements. When water is added, the mix undergoes a chemical
reaction and hardens. An extraordinarily versatile building material,
concrete is used for the utilitarian, the ornamental, and the
monumental. While early proponents of modern concrete considered
it to be permanent, it is, like all materials, subject to deterioration.
This Brief surveys the principal problems posed by concrete deterioration,
their likely causes, and approaches to their remedies. In almost
every instance, remedial work should only be undertaken by qualified
professionals. Faulty concrete repair can worsen structural problems
and lead to further damage or safety hazards. Concrete repairs
are not the province of do-it-yourselfers. Consequently, the corrective
measures discussed here are included for general information purposes
only; they do not provide "how to" advice.
The Romans found that the mixture of lime putty with pozzolana,
a fine volcanic ash, would harden under water. The result was
possibly the first hydraulic cement. It became a major feature
of Roman building practice, and was used in many buildings and
engineering projects such as bridges and aqueducts. Concrete technology
was kept alive during the Middle Ages in Spain and Africa, with
the Spanish introducing a form of concrete to the New World in
the first decades of the 16th century. It was used by both the
Spanish and English in coastal areas stretching from Florida to
South Carolina. Called "tapia," or "tabby,"
the substance was a creamy white, monolithic masonry material
composed of lime, sand, and an aggregate of shells, gravel, or
stone mixed with water. This mass of material was placed between
wooden forms, tamped, and allowed to dry, the building arising
in layers, about one foot at a time.
 Milton House, Milton, Wisconsin (1844) is an early example of gravel wall construction with 12-to-15-inch thick monolithic concrete walls coated on the exterior with stucco. Photo: William Coney. |
Despite its early use, concrete was slow in achieving widespread
acceptance as a building material in the United States. In 1853,
the second edition of Orson S. Fowler's A Home for All publicized
the advantages of "gravel wall" construction to a wide
audience, and poured gravel wall buildings appeared across the
United States. Seguin, Texas, 35 miles east of San
Antonio, came to be called "The Mother of Concrete Cities"
for some 90 concrete buildings made from local "lime water"
and gravel. Impressed by the economic advantages
of poured gravel wall or "limegrout" construction, the
Quartermaster General's Office of the War Department embarked
on a campaign to improve the quality of building for frontier
military posts. As a result, lime-grout structures were built at
several western posts, such as the buildings that were constructed
with 12 or 18-inch-thick walls at Fort Laramie, Wyoming between
1872 and 1885. By the 1880s sufficient experience had been gained
with unreinforced concrete to permit construction of much larger
buildings. The Ponce de Leon Hotel in St. Augustine, Florida,
is a notable example from this period.
Reinforced concrete in the United States dates from 1860, when
S.T. Fowler obtained a patent for a reinforced concrete wall.
In the early 1870s William E. Ward built his own house in Port
Chester, New York, using concrete reinforced with iron rods for
all structural elements.
 "Fallingwater," a dramatic reinforced concrete residence by Frank Lloyd Wright, is anchored into bedrock on the hillside. Photo: HABS Collection, NPS. |
Despite these developments, such construction
remained a novelty until after 1880, when innovations introduced
by Ernest L. Ransome made reinforced concrete more practicable.
The invention of the horizontal rotary kiln allowed production
of a cheaper, more uniform and reliable cement, and led to the
greatly increased acceptance of concrete after 1900.
During the early 20th century Ransome in Beverly, Massachusetts,
Albert Kahn in Detroit, and Richard E. Schmidt in Chicago promoted
concrete for utilitarian buildings with their "factory style,"
featuring an exposed concrete skeleton filled with expanses of
glass. Thomas Edison's cast-in-place reinforced concrete homes in
Union Township, New Jersey, proclaimed a similarly functional
emphasis in residential construction. From the 1920s
onward, concrete began to be used with spectacular design results:
in James J. Earley and Louis Bourgeois' exuberant, graceful Baha'i
Temple in Wilmette, Illinois; and in Frank Lloyd Wright's
masterpiece "Fallingwater" near Mill Run, Pennsylvania.
Eero Saarinen's soaring Terminal Building at Dulles
International Airport outside Washington, D.C., exemplifies the
masterful use of concrete achieved in the Modern era.
"Preservation of Historic Concrete" an Historic Preservation Brief
