Transcript Chapter 3 Cement 3.2.3 Technical Properties of Portland Cement • Fineness • Setting Time • Soundness of the Portland Cement • Strength • Other properties Compressive strength and bending strength can.

Chapter 3
Cement
3.2.3 Technical Properties of
Portland Cement
• Fineness
• Setting Time
• Soundness of the Portland
Cement
• Strength
• Other properties
Compressive strength and bending strength
can be tested by producing standard specimen
（ 40×40×160） which is made by C:S:W=1:3:0.5
and cured in the standard condition
C:S:W=1:3:0.5
Standard specimen
40 × 40×160
Cured under
the standard
condition
Compressive
strength
Bending strength
Fig.3.2.10 Strength testing instrument
Compressive strength
instrument
bending strength instrument
Fig3.2.10 Strength testing instrument
抗压强度抗折强度
Strength Grades
• According to
– 3 days and 28 days compressive
strength
– 3 days and 28 days bending
strength
• Portland cement can be classified
into 42.5，42.5R, 52.5，52.5R, 62.5,
62.5R grades.
• The strength of every age should not
be lower than the required number
in GB175-99 table.
• The cement of every grade can be
classified into 2 types, high earlystrength(R) ones and normal ones.
42.5
62.5R
42.5R
Strength
Grade
62.5
52.5
52.5R
Technical Properties Analysis
The technical indexes of the
cement before using are the 4
items: fineness, setting time，
strength and soundness.
Fineness, setting time，
strength and soundness must be
qualified. The cement can be
used according to the
requirement of the lower grade,
if only the strength is
unqualified.
If only the strength
is unqualified
Cement of the
lower grade
Other Properties
• Density
– 3.0-3.15g/cm3, commonly 3.1g/cm3
• Bulk Density
– 1000-1600kg/m3
• Density of long-kept cement decreases a little.
Free CaO combines with H2O, CO2 in the air to
form Ca(OH)2 and CaCO3 with low density.
Alkali Content
• Alkali content which is donated by calculated
value of Na2O+0.658K2O avoids alkaliaggregate reaction.
• Alkali content of low alkali cement≯0.6%，
or treat between supply and requisitioning
parties.
Hydration Heat
• Most hydration heat is given out at the initial
period of hydration and its quantity depends on
chemical compound and fineness of cement,
mineral admixture and intrusion aid.
• The higher C3S, C3A, the finer the particle, the
bigger hydration heat, the more advantageous to
the construction in winter, but more harmful for
mass concrete