Chemical analysis
Chemical analysis of cement involves testing the material for all the
chemical requirements stated in the relevant international standard,
which would normally involve such tests as general chemical composition.
Conducting the suite of testing ensures that cement supplied does indeed
meet the standard required.
Compressive strength
This test is used to determine whether cement meets the compressive
strength requirements of international standards. The test consists of
casting a number of standard cubic specimens in laboratory conditions,
using standard sands and then testing them for compressive strength
after the required curing period has elapsed, normally 28 days.
Fineness
The fineness of cement has a significant effect in its physical properties
when used in concrete. Generally the finer the cement powder, the more
rapid the concrete will set, as there is an increase in its surface area.
The measure of fineness is usually undertaken by sieving, and the
result assessed against the cement standard for compliance.
Heat of Hydration
The chemical reaction that takes place between cement when
mixed with water is exothermic. The intensity of this reaction is
measured in this test. The value of heat of hydration can be
important where the cement maybe incorporated into concrete,
which will be poured in large volumes. In such cases there can be
a considerable built up of heat as the reaction takes place, which,
if excessive, could caused cracking in the structure.
Loss On Ignition
This test is used to determine the percentage loss of
material in a cement specimen when subjected to high
temperature. It is used as a measure of deleterious material
in the cement, the level of which is normally controlled in cement
manufacturing standards.
Physical Analysis
Physical analysis of cement involves testing the material for all the
physical requirements stated in the relevant international standard,
which would normally involve such tests as compressive strength and
fineness amongst others. Conducting the suite of testing ensures that
cement supplied does indeed meet the standard required.
Setting Time
The time it takes for a cement to stiffen to a standard value after
addition of water is commonly known as the set time. The test involves
mixing cement with water and then measuring its resistance to
penetration of a standard probe at varying intervals of time, until
a certain value is reached.
Soundness
The main purpose of the soundness test is to assess the possible
risk of late expansion due to hydration of uncombined calcium
oxide and/or magnesium oxide. The test uses apparatus known
as Le Chatelier apparatus, which magnifies any expansion during
heating to a value that can be measured.
