Civil Engineering Reference
In-Depth Information
Fig. 2-21. Masonry cement and plastic cement are used to make plaster or stucco for commercial, institutional, and residential
buildings. Shown are a church and home with stucco exteriors. Inset shows a typical stucco texture. (69389, 67878, 68805)
The increased use of masonry in demanding structural
applications, such as high seismic areas, resulted in the re-
cent development of mortar cement. Mortar cement is simi-
lar to masonry cement in that it is a factory-prepared
cement primarily used to produce masonry mortar.
However, ASTM C 1329 places lower maximum air content
limits on mortar cement than permitted for masonry
cements; also, ASTM C 1329 is the only ASTM masonry
material specification that includes bond strength perform-
ance criteria.
The workability, strength, and color of masonry
cements and mortar cements stay at a high level of unifor-
mity because of manufacturing controls. In addition to
mortar for masonry construction, masonry cements and
mortar cements are used for parging. Masonry cements are
also used in portland-cement based plaster or stucco (Fig.
2-21) construction (see ASTM C 926). Masonry cement and
mortar cement should not be used for making concrete.
based plaster or stucco (ASTM C 926), usually in the south-
west and west coast of the United States (Fig. 2-21). Plastic
cements consist of a mixture of portland and blended
hydraulic cement and plasticizing materials (such as lime-
stone, hydrated or hydraulic lime), together with materials
introduced to enhance one or more properties such as
setting time, workability, water retention, and durability.
ASTM C 1328 defines separate requirements for a Type
M and a Type S plastic cement with Type M having higher
strength requirements. The Uniform Building Code (UBC)
25-1 does not classify plastic cement into different types,
but defines just one set of requirements which correspond
to those of an ASTM C 1328 Type M plastic cement. When
plastic cement is used, no lime or other plasticizer may be
added to the plaster at the time of mixing.
The term “plastic” in plastic cement does not refer to
the inclusion of any organic compounds in the cement;
rather, “plastic” refers to the ability of the cement to impart
to the plaster a high degree of
plasticity
or workability.
Plaster made from this cement must remain workable for a
long enough time for it to be reworked to obtain the desired
densification and texture. Plastic cement should not be used
to make concrete. For more information on the use of plas-
tic cement and plaster, see
Melander and Isberner (1996)
.
Plastic Cements
Plastic cement is a hydraulic cement that meets the require-
ments of ASTM C 1328. It is used to make portland cement-
Finely-Ground Cements
(Ultrafine Cements)
Finely-ground cements, also called
ultrafine cements, are hydraulic ce-
ments that are ground very fine for use
in grouting into fine soil or thin rock
fissures (Fig. 2-22). The cement parti-
cles are less than 10 micrometers in
diameter with 50% of particles less
than 5 micrometers. Blaine fineness
often exceeds 800 m
2
/kg. These very
fine cements consist of portland ce-
ment, ground granulated blast-furnace
slag, and other mineral additives.
Fig. 2-22. (left) A slurry of finely ground cement and water can be injected into the
ground, as shown here, to stabilize in-place materials, to provide strength for
foundations, or to chemically retain contaminants in soil. (68810) Illustration (right) of
grout penetration in soil.
