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7/27/2019 aggregates on site lec 30.PPT
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STORING OF AGGREGATE
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No.
Types of concrete Slump
1 Concrete for road construction 20 to 40 mm
2 Concrete for tops of curbs,
parapets, piers, slabsand wall
40 to 50 mm
3 Concrete for canal lining 70 to 80 mm
4 Normal RCC work 80 to 150mm
5 Mass concrete 20 to 50 mm
6 Concrete to be vibrated 10 to 25 mm
Recommended Values of Slump for Various Purpose
http://theconstructor.org/concrete/types-of-concrete/966/http://theconstructor.org/category/structural-engg/slab/http://theconstructor.org/category/structural-engg/wall/http://theconstructor.org/category/structural-engg/wall/http://theconstructor.org/category/structural-engg/slab/http://theconstructor.org/concrete/types-of-concrete/966/7/27/2019 aggregates on site lec 30.PPT
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QUALITY CONTROL For uniform quality of concrete, the ingredients preferably
be used from single source.
When aggregate from different sources are used, the
strength and other characteristics of materials are likely to
change and therefore should only be used after properevaluation and testing.
Such is the case of cement also, when cement from different
sources are used, it will effect certain characteristics of the
concrete which then likely change the compressive strength
of the concrete. Thus cement should be tested after every
three months of storage. Set cement with hard lumps is to
be rejected.
2A
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AggregatesSources of variability in the aggregates
Grading
Maximum size
Shape
Moisture Content.
Aggregate should be separately stock piled in single sizes. The
graded aggregate should not be allowed to segregate.
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AGGREGATE SIMPLE RULE OF GRADING For FINE AGGREGATE, long continuous grading
are preferred and their should be minimum material
passing throughout 300 microns and 150 micron IS
sieves.
For FINE AGGREGATE, the grading that are at the
coarser end of the range are more suitable for rich
mixes and those at the fine end of range should be
suitable for lean mixes.
A COARSER AGGREGATE consistent with the size
of the member and the spacing of the reinforcement
is more suitable.
The aggregate sizes should be so selected that onesize fits into the voids left by the next higher size
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AGGREGATE The aggregate should be free from impurities and
deleterious materials, SINCE FOR EVERY 1% OF CLAY
IN THE SAND, THERE COULD BE AS MUCH AS 5%
REDUCTION IN THE STRENGTH OF THE
CONCRETE. THE MOISTURE CONTENT OF THE AGGREGATE
SHOULD BE TSKEN IN ACCOUNT WHILECALCULATING THE QUANTITY OF MIXING WATER
BULKING OF SAND is important in several ways, when
volume batching is adopted, it gives erroneous results,
besides increasing the W/C ratio which, in turn, enhances
the workability thereby REDUCING THE STRENGTH
OF THE CONCRETE
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AGGREGATE TESTING METHODOLOGY The aggregate should be tested once initially at the
time of arrival to the site of each sources of supply.
Subsequent tests of aggregate should be conducted
daily at the site for grading and moisture content.
Quality control and acceptance inspection should
be adopted at the site.
Tests should be done in the case the plant forbatching has to be installed. Once the batching
plant is installed, then frequent tests has to be done
to ensure the desired strength of the concrete.
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Suitable way
of storing of
AGGREGATEon Site
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Fineness of cement affect strengthgain?
Fineness defines the surface area of cement particles
present in per unit weight, which implies that more
fineness means more particles in unit weight. This
enhances the reaction rate which in turn will result in
faster gain of strength at earlier stages.
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Any Questions????
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Before we ENDS
Various tests possible for the aggregates
Possible tests done on the site.
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