Volume-IF - JantERmantER

3.8 Workability
DCPL-K4A02
Whenever the water-cement ratio dictated by durability consideration is
lower than that required from strength criterion, the former shall be
adopted.
In general the water cement ratio between 0.4 and 0.45 will be desirable to
satisfy the durability requirement and from the consideration of
impermeability of conrete. The contractor may propose lower water
cement ratio as mentioned above by addition of a suitable plasticizer /
super-plasticizer. However the contractor has to propose specifically
along with field trials in the event of lower cement content if found suitable
along with a plasticizer. It will be preferable to use Melamine based
plasticizer.
The degree of workability necessary to allow the concrete to be well
consolidated and to be worked into the corners of formwork and around
the reinforcement and embedments and to give the required surface finish
shall depend on the type and nature of structure and shall be based on
experience and tests. The usual limits of consistency for various types of
structures are given below :
TABLE - III
LIMITS OF CONSISTENCY
Degree of
workability
Slump in mm with
Standard Cone as
per IS:1199
Min. Max.
Use for which concrete
is suitable.
Very low 0 25 Large Mass concrete
structure with heavy
compaction equipment,
roads and like.
Low 25 50 Uncongested wide and
shallow R.C.C. structures.
Medium 50 100 Deep but wide R.C.C.
structures with congestion
or reinforcement and
inserts.
High 100 150 Very narrow and deep
R.C.C. structures with
congestion due to
reinforcement and inserts.
(NOTE : Notwithstanding anything mentioned above, the slump to
be obtained for work in progress shall be as per direction of
the Engineer)
(PCA.774.S034sca2) V.II-D2/S-III : 16