Transcript 5.3.2 Water Retentivity

Chapter 5
Construction Mortar
Chapter 5
§5. 3 Technical Properties
Mobility (consistency)
Water retentivity
Strength
Durability
Water retentivity
Definition
• Water retentivity is the ability of keeping
water, or the inseparability of the composites
of flesh mortar.
• Mortar with poor water retentivity can easily
bleed, laminate, and segregate, resulting in
bonding improperly and influencing the
normal hardening, as well as decreasing the
strength of mortar.
Water retentivity
Influencing factors
• Type and quantity of cementitious
material
• Property of aggregate
• Water quantity
• Admixtures
Water retentivity
Testing
Index: layering
degree
Apparatus:
apparatus of
mortar layering
degree
Method and Process
Put fresh mortar in
layering degree cylinder
Stew 30min
Get rid of top 2/3 mortar
Gauge the sinking
degree of surplus mortar
Layering degree= the sinking degree 1- the sinking degree 2
Evaluation of Water Retentivity
Water retentivity can be evaluated according to Table 5.3.1 .
Table 5.3.2
Evaluation of Water Retentivity
Layering degree
(mm)
Water retentivity
<10
Rich water retentivity, excess of binding
material, extra-fine sand, great shrinkage,
useless
>30
Poor water retentivity, easy segregation,
useless
10～20
Good