aggregates on site lec 30.ppt

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/


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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.

2


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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

2


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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.

2


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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.

2


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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.

aggregates on site lec 30.ppt

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