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Concrete Characteristics
Historic Interiors
Concrete is composed of fine (sand) and
The expanded use of concrete provided new opportunities to coarse (crushed stone or gravel) aggregates
create dramatic spaces and ornate architectural detail on the and paste made of portland cement and water.
interiors of buildings, at a significant cost savings over traditional The predominant material in terms of bulk is
construction practices. The architectural design of the Berkeley the aggregate. Portland cement is the binder
City Club in Berkeley, California, expressed Moorish and Gothic most commonly used in modern concrete. It
elements in concrete on the interior of the building (Fig. 10). Used is commercially manufactured by blending
as a woman's social club, the building was designed by noted limestone or chalk with clays that contain
California architect Julia Morgan and constructed in 1929. The alumina, silica, lime, iron oxide and magnesia,
vaulted ceilings, columns, and ornamental capitals of the lobby and heating the compounds together to high
and the ornamental arches and beamed ceiling of the "plunge" are temperatures. The hydration process that
all constructed of concrete. occurs between the portland cement and water
results in formation of an alkali paste that
surrounds and binds the aggregate together as
a solid mass.
The quality of the concrete is dependent on
the ratio of water to the binder; binder content;
sound, durable, and well-graded aggregates;
compaction during placement; and proper
curing. The amount of water used in the mix
affects the concrete permeability and strength.
The use of excess water beyond that required
in the hydration process results in more
permeable concrete, which is more susceptible
to weathering and deterioration. Admixtures
Figure 10. The Berkeley City Club has significant interior spaces alld features of
are commonly added to concrete to adjust
concrete construction, including the lobby and pool. Photos: Una Gilmartin (left)
concrete properties such as setting or hardening
and Brian Kehoe (right), Wiss, Janney, Elstner Associates, Illc.
time, requirements for water, workability, and
other characteristics. For example, the advent
The historic character of a building's interior can also be conveyed
of air entraining agents in the 1930s provided
in a more utilitarian manner in terms of concrete features and
enhanced durability for concrete.
finishes (Fig. 11). The exposed concrete structure-columns,
capitals, and drop panels-is an integral part of the character During the twentieth century, there was
of this old commercial building in Minneapolis. In concrete a steady rise in the strength of ordinary
warehouse and factory buildings of the early twentieth century, concrete as chemical processes became better
exposed concrete columns and formboard finish concrete slab understood and quality control measures
ceilings are common features as seen in this warehouse, now improved. In addition, the need to protect
converted for use as a parking garage and shops. embedded reinforcement against corrosion
was acknowledged. Requirements for concrete
cover over reinforcing steel, increased cement
content, decreased water-cement ratio, and air
entrainment all contributed to greater concrete
strength and improved durability.
Mechanisms and Modes of
Deterioration
Causes of Deterioration
Concrete deterioration occurs primarily because
of corrosion of the embedded steel, degradation
of the concrete itself, use of improper techniques
Figure 11. Whether in a circa 1925 office (left) or in a parking garage or materials in construction, or structural
and retail facility (right), exposed concrete structures help characterize problems. The causes of concrete deterioration
these building interiors. Photo: Minnesota Historical Society (left). must be understood in order to select an
appropriate repair and protection system.
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