Technical Specifications - UNDP

Degree of
Workability
20 mm Max. size
aggregate
Slump Compacting
mm Factor
37 mm Max. size
aggregate
Slump Compacting
mm Factor
Low 13-25 0.82-0.88 13-50 0.82-0.88
Medium 25-50 0.88-0.94 50-101 0.88-0.94
High 50-127 0.94-0.97 101-117 0.94-0.97
Use for which Concrete is suitable
Simple reinforced sections with
vibration
Heavily reinforced sections with
vibration
Sections with heavily congested
reinforcement where vibration is
difficult
In case cylinders are used for determination of concrete compressive strength in accordance with
ASTM C 39, the corresponding cube strength shall be obtained by using a multiplication factor of
1.2 .
AGGREGATE/CEMENT RATIO : the term aggregate/cement ratio means the ratio by weight of
aggregate to cement in the mix. For this purpose the aggregate is taken in a saturated surface-dry
condition as for the water/cement ratio above .
FINE/TOTAL AGGREGATE RATIO : the term fine/total aggregate ratio means the ratio by weight
of the fine aggregate to the total aggregate in the mix expressed as a percentage . For this
purpose the aggregate is also taken in a saturated surface-dry condition as for the water/cement ratio
above .
VOLUME OF AIR ENTRAINED : the air content expressed as a percentage by volume of concrete
shall be determined by ASTM C231, 'Air Content of Freshly Mixed Concrete by the Pressure
Method ' . At least one test for each 120 cubic metres of concrete shall be made .
SLUMP : the slump of the freshly mixed concrete shall be determined in accordance with Part 2 of
BS 1881 or ASTM C143 . At least one morning and one afternoon test shall be made and
whenever directed by the Engineer .
STRENGTH OF CONCRETE : Preliminary Test Cubes shall be taken from the trial mixes
designed to select the job mix and shall be made and tested in accordance with Parts 3 and 4 of BS
1881 .
SAMPLING FOR COMPLIANCE TESTING : Works Test Cubes shall be those used for control
during construction and shall be made and tested in accordance with BS 5328 PART 4:1990.
Recommended Miniumn Rates Sampling
Average Rate o Sampling One Sample Maximum quantity of concrete at risk
( 6 cubes) per
under any one decision
10 m3 or 10 batches 40 m3
20 m3 or 20 batches 80 m3
50 m3 or 50 batches 200 m3
18