PORTLAND CEMENT Flashcards
made from silica (sand),
alumina (aluminum oxide), lime, iron oxide and
magnesia (magnesium oxide).
PORTLAND CEMENT
refers to materials which act as
adhesives.
CEMENT
Production of Portland cement
starts with two
basic raw ingredients: a calcareous material and
an argillaceous material.
a calcium oxide, such as limestone, chalk, or
oyster shells.
CALCAREOUS MATERIAL
combination of silica and alumina that can be
obtained from clay, shale, and blast furnace slag.
ARGILLACEOUS MATERIAL
e an important
property that must be carefully controlled. Since
hydration starts at the surface of cement
particles, the finer the cement particles, the
larger the surface area and the faster the
hydration.
FINENESS OF PORTLAND CEMENT
Fineness of Portland Cement
finer material results in
faster strength development and a greater initial
heat of hydration. Increasing fineness beyond the
requirements for a type of cement increases
production costs and can be detrimental to the
quality of the concrete.
Properties of the hydrated cement are
evaluated with either cement paste (water and
cement) or mortar (paste and sand).
Properties of Hydrated Cement
Abrams found that the ratio of the
weight of water to the weight of cement, water–
cement ratio, influences all the desirable
qualities of concrete.
WATER CEMENT RATIO
General concrete work when the special properties of other types are not needed. Suitable for floors, reinforced concrete structures, pavements, etc.
NORMAL
Protection against moderate sulfate exposure, 0.1-0.2% weight water-soluble sulfate in soil or 150-1500 ppm sulfate in water(Seawater). Can be specified with a moderate heat of hydration, making it suitable for large piers, heavy abutments, and retaining walls. The moderate heat of hydration is also beneficial when placing concrete in warm weather
MODERATE SULFATE RESISTANCE
Used for fast track construction when forms need to be removed as soon as possible or structure needs to be put in service as soon as possible. In cold weather, reduces time required for controlled curing.
HIGH EARLY STRENGTH
Used when mass of structure, such as large dams, requires careful control of the heat of hydration
LOW HEAT OF HYDRATION
Protection from severe sulfate exposure, 0.2-2.0% weight water-soluble sulfate in soils or 1500-10800 ppm sulfate in water
HIGH SULFATE RESISTANCE
Other than the five standard types of Portland cement,
several hydraulic cements are manufactured in the
United States, including:
WHITE PORTLAND CEMENT
BLENDED HYDRAULIC CEMENT
HYDRAULIC CEMENTS
MASONRY AND MORTAR CEMENTS
PLASTIC CEMENTS
FINELY GROUND CEMENTS (ULTRAFINE CEMENTS)
EXPANSIVE CEMENTS
SPECIALTY CEMENTS
Hydraulic cements
Type GU (General use)
Type HE (High early strength)
Type MS (Moderate sulfate resistance)
Type HS (High sulfate resistance)
Type MH (Moderate heat of hydration)
Type LH (Low heat of hydration)
Any potable water is suitable for making
concrete. However, some non-potable water
may also be suitable. Sometimes, concrete
suppliers will use unprocessed surface or well
water if it can be obtained at a lower cost than
processed water. However, impurities in the
mixing water can affect concrete set time,
strength, and long-term durability.
MIXING WATER
Cement paste setting time is affected by a number of
items including:
CEMENT FINENESS
WATER CEMENT RATIO
CHEMICAL CONTENT (GYPSUM CONTENT)
ADMIXTURES
used to characterize how a
particular cement paste sets. For construction purposes,
the initial set must not be too soon, and the final set must
not be too late.
SETTING TESTS
Occurs when the paste begins to
stiffen considerably.
INITIAL SET
Occurs when the cement has hardened
to the point at which it can sustain some load.
FINAL SET
