What is cement?

Answer 1

Cement is a building material made by grinding calcined limestone and traces of clay and gypsum. Its key use is as an ingredient for concrete or mortar.

• Cement is a heterogeneous mixture.
• Cement is used as a binding material for sand/aggregate.
• Cement is hardened by adding an appropriate quantity of water.

Cement is a powder that is made of calcined lime and clay. Cement is mixed with sand, gravel and water to form concrete. The cement has a chemical reaction with water, and hardens.

Answer 2

More than half of ready-mixed concrete

contains fly ash, slag cement, silica fume,

metakaolin, or other pozzolanic materials.

These materials are collectively referred to

as supplementary cementitious materials

(SCMs).

SCMs can be included in concrete, either as

an ingredient added at batching, or as a

component of a blended cement, or both

(Figure 1). SCMs can be added during

batching along with portland cement. SCMs

can also be added to concretes made with

blended cements. SCMs added directly to

concrete are governed by ASTM C618 (fly

ash and natural pozzolans), C989 (slag), or

C1240 (silica fume), while blended cements

are governed by ASTM C595 or C1157.

Since the benefits of SCMs arise from their

physical and chemical characteristics, it

might be assumed that similar performance

in concrete is achieved, for example, by

adding a fly ash at a ready-mixed concrete

batch plant or through use of a blended

cement made with fly ash. Although good

concrete performance can be achieved

through both techniques, blended cements

provide an advantage in that they can be

produced with the same quality control

techniques as portland cements, including

control of fineness and optimization of

sulfate content. Sulfate optimization can be

particularly important for some fly ashes

with high aluminate contents. Although a

rare occurrence, some fly ashes can throw

off the sulfate balance in fresh concrete,

leading to problems with workability and

setting. The quality control of blended

cements takes one variable out of the

concrete batching process.

Answer 3

Cementation is where water and other minerals glue larger sediments together.

Answer 4

the gum of the root is covered by a thin layer called cementum rather that enamel.