Transcript Slide 1

CEMENT DEFINITION
Cement is often confused with concrete. Cement is a finely ground,
usually grey colored mineral powder. When mixed with water, cement
acts as a glue to bind together the sand, gravel and crushed stone to
form concrete, the most widely used construction material in the world.
TYPES OF CEMENTS
Ordinary cement
This type of cement is used a lot today, and is still known as OPC (ordinary
Portland cement) ... It is ground up into a powder to form ordinary OPC
Rapid heat cement
They generate more heat in the early stages and can be useful in cold weather
concreting. ... as either rapid-setting or extra rapid hardening may be
Low heat cement
Low Heat Cement complies with AS 3972, Special Purpose Type LH/SR. It is
manufactured from the ingredients of specially selected cement clinker and
ground granulated blast furnace slag, that result in significantly lower heat
generation during the process of hydration than the comparable Portland
Cement.
Portland blast furnace cement
The granulated slag made by the rapid chilling of suitable molten slags from
blast furnaces forms the basis of another group of constructional cements. A
mixture of portland cement and granulated slag, containing up to 65 percent
slag, is known in the English-speaking countries as portland blast-furnace
(slag) cement.
High alumina cement
of High Alumina Cement, Alumina Cement, Refractory Cement, Refractory
Materails, ... Density Corundum Bricks, high alumine cement ca50-G5, G7, G9,
fused, ca70, ca80
Expanding cement
Expanding and nonshrinking cements expand slightly on hydration, thus
offsetting the small contraction that occurs when fresh concrete dries for the
first time. Expanding cements were first produced.
Quick setting cement
Rapid cure allows for quick access to repaired areas. Garonite anchoring
cement sets and e-x-p-a-n-d-s rapidly, curing twice as strong as concrete in
one hour. Use indoors or out Air & trading cement
Hydrophobic cement
Cement is a hydraulic bonding agent used in building construction and civil
engineering. It is a fine powder obtained by grinding the clinker of a clay and
limestone mixture calcined at high temperatures. When water is added to
cement it becomes a slurry that gradually hardens to a stone-like consistency.
It can be mixed with sand and gravel (coarse aggregates) to form mortar and
concrete.
White cement
White portland cement is readily available throughout North America. It has
essentially the same properties as gray cement, except for color, which is a very
important quality control issue in the industry.
The color of white cement depends on raw materials and the manufacturing
process. It is the metal oxides (primarily iron and manganese) that influence the
whiteness and undertone of the material. White cement is manufactured to
conform to ASTM C 150, Specification for Portland Cement. Although Types I, II,
III, and V white cements are produced, Types I and III are the most common.
White cements produce clean, bright colors, especially for light pastels. Many
different colors can be created by adding pigments to concrete made with white
portland cement. Two or more pigments can be combined to achieve a wide
range of colors. White cement (or a mixture of white and gray cement) can be
specified to provide a consistent color of choice. An even greater variety of
decorative looks can be achieved by using colored aggregates and varying the
surface finish treatment or texture.
STRENGTH OF CEMENT
The mechanical strength of hardened cement is the property of the material that
is perhaps most obviously required for structural use.
The strength of the mortar or concrete depends on the cohesion of the cement
paste, on its adhesion to the aggregate particle and other.
Strength test:
Compression is the most common measure of strength. A 2-in. mortar cube
using a 2.75:1 sand/cement ratio with a water/cement ratio of 0.485 - 0.460 is
tested. After a certain procedure is followed the specimens are failed. Tensile
strength is determined by a direct tensile test. The results are not of much value.
Flexural strength is determined by a flexural test of a small rectangular-shaped
prism on simple supports with a center load. The flexural strength is directly
calculated. This mortar strength does not necessary relate to concrete strength
using the same cement; used for quality control.
The composition of Portland cements falls within the range of:
60 to 67 percent lime,
17 to 25 percent silica,
2 to 8 percent alumina, and
0 to 6 percent iron oxide together with 1 to 7 percent sulphur trioxide,
derived mainly from the added gypsum, 0.1 to 5 percent magnesia, and 0.1 to
1.5 percent alkalis.
TYPES OF PORTLAND CEMENT
Five types of Portland cement are standardized in the U.S. (Standard
Specification for Portland Cement C 150 - 97):
Ordinary (Type I) - - most common, no special properties
Modified (Type II) - - good strength with lower heat of hydration
High-early-strength (Type III) - - rapid setting; used in precast work or at low
temperatures -- possible tensile cracking due to thermal stress if sections are
large.
Low-heat (Type IV) - - Used in mass concrete applications-low heat of
hydration
Sulphate-resisting (Type V) - - provides protection from damage due to
exposure to sulfates (seawater, some groundwater supplies, and particularly
wetting and drying processes).
In other countries Type II is omitted, and Type III is called rapid hardening.
Type V is known in some European countries as Ferrari cement.
END OF SESSION