Concrete Experiment 2
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Transcript of Concrete Experiment 2
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PRESENTED BY: NABEELKHAN
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TO DETERMINE THE
WORKABILITY OF CONCRETE
AT VARIOUS WATERCONTENTS WITH THE HELPOF COMPACTION FACTOR
TEST
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IS:6461defines workability as that propertyof freshly mixed concrete or mortar whichdetermines the ease and homogeneity withwhich it can be mixed, placed compacted
and finished Workability depends on water content,
aggregate (shape and size distribution) andcan be modified by adding chemicaladmixtures. Raising the water content up toa certain limit or adding chemicaladmixtures will increase concreteworkability
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Compacting factor of fresh concrete isdone to determine the workability of freshconcrete by compacting factor test.
Compacting factor test gives the behaviourof fresh concrete under the action ofexternal forces.
It measures the compact ability of concrete
which is an important aspect of workability,by measuring the amount of compactionachieved for a given amount of work.
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Compacting factor =
(Weight of partially compactedconcrete)/(Weight of fully compacted
concrete)
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The concrete mixture is prepared by mixing cement and water in the ratio 0.6 andaggregates in the ratio 1:3:5
The sample of concrete is placed in the upper hopper up to the brim The trap door is opened so that concrete falls into the lower hopper The trap door of the lower hopper is opened and the concrete is allowed to fall into the
cylinder
The excess concrete above the top level is removed The concrete in the cylinder is then weighed, this is known as weight of partiallycompacted
concrete Another sample of the same concrete is filled into the cylinder and it is compacted with
the rod at suitable intervals to obtain fully compacted concrete The concrete in the cylinder is weighed, this weight is known as weight of fully
compacted concrete The experiment is then repeated taking different water cement ratios as 0.7 and 0.8
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S.No. W/C RATIO WEIGHT OFPARTIALLYCOMPACTEDCONCRETE
WEIGHTOFFULLYCOMPACTEDCONCRETE
COMPACTIONFACTOR
1 0.6 19.2 20.5 0.936
2 0.7 19.8 20.95 0.947
3 0.8 20.25 21.15 0.957
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Compacting factor = (Weight ofpartially compacted concrete)/(Weightof fully compacted concrete)
Compaction factor for 0.6 w/c ratio =19.20/20.50 = 0.936
Compaction factor for 0.7 w/c
ratio=19.80/20.95 = 0.947 Compaction factor for 0.8 w/c ratio =
20.25/21.15 = 0.957
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The compaction factor of the givensample of concrete for w/c ratio 0.6 is0.936, for w/c ratio 0.7 is 0.947 and for
w/c ratio 0.8 is 0.957.
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COMPA
CTION
FACTOR
W/C RATIO
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The results for compacting factor test for theconcrete for different water cement ratiosdepicts that compaction factor increases withthe increase in the water cement ratios of theconcrete mixes and thus the workability of theconcrete increases with the increase in watercement ratio.
Thus to obtain a good workable concrete weshould increase the water cement ratio.
But this increase should be up to a certaindegree otherwise a large water cement ratiocan also affect the strength of concrete.
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The water cement ratios to be used for a
certain grade of concrete to obtainoptimum workability can be determined
using compaction factor test. a concrete may not be workable when
compacted by hand but may be
satisfactory when vibration are used.Therefore workability of fresh concreteneeds to be determined every timebefore it is used.
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