concrete experiment 2

8/2/2019 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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concrete experiment 2

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