CONCRETE MAKING MATERIALS –II: AGGREGATE. CLASSIFICATION OF AGGREGATES ACCORDING TO GEOLOGICAL ORIGIN – NATURAL AGGREGATE – ARTIFICIAL AGGREGATE ACCORDING.

CONCRETE MAKING MATERIALS –II: AGGREGATE

CLASSIFICATION OF AGGREGATES• ACCORDING TO GEOLOGICAL ORIGIN– NATURAL AGGREGATE– ARTIFICIAL AGGREGATE

• ACCORDING TO SIZE– FINE AGGREGATE– COARSE AGGREGATE– ALL-IN-AGGREGATE– SINGLE-SIZE-AGGREGATE

• ACCORDING TO SHAPE – ROUNDED AGGREGATE– IRREGULAR AGGREGATES– ANGULAR AGGREGATE– FLAKY AND ELONGATED AGGREGATE

• BASED ON UNIT WEIGHT– NORMAL-WEIGHT AGGREGATE– HEAVY-WEIGHT OR HIGH-DENSITY AGGREGATE– LIGHT-WEIGHT AGGREGATE

CHARACTERISTICS OF AGGREGATES

• STRENGTH OF AGGREGATE• PARTICLE SHAPE AND TEXTURE• SPECIFIC GRAVITY• BULK DENSITY• POROSITY AND ABSORPTION OF AGGREGATES• MOISTURE CONTENT OF AGGREGATE• BULKING OF FINE AGGREGATE

Percentage of Bulking of Sand with Moisture Content

DETERMINATION OF PERCENTAGE OF BULKING BY FIELD TEST

• Fill a sample of moist fine aggregate (sand) into a measuring cylinder in the normal manner. Note down the level, say h1.

• Pour water into a measuring cylinder and completely cover the sand with water and shake it. Since the volume of the saturated sand is the same as that of the dry sand, the saturated sand completely offsets the bulking effect. Note down the level of sand, say h2.

• Subtract the final level h2 from initial level h1 (i.e. h1-h2), which shows the bulking of sand under test.

• Calculate percentage of bulking using formula given below.

• Percentage of bulking = [(h1-h2)/h2]*100

DELETRIOUS SUBSTANCES IN AGGREGATES

Deleterious Materials – Aggregates shall not contain any harmful material, such as pyrites, coal, lignite, mica, shale or similar laminated material, clay, alkali, soft fragments, sea shells and organic impurities in such quantity as to affect the strength or durability of the concrete. Aggregates to be used for reinforced concrete shall not contain any material liable to attack the steel reinforcement. Aggregates which are chemically reactive with alkalis of cement are harmful as cracking of concrete may take place

SOUNDNESS OF AGGREGATE• The ability of the aggregate to resist excessive

changes in volume due to changes in environmental conditions.

ALKALI-AGGREGATE REACTION (AAR)OR

ALKALI-SILICA REACTIVITY (ASR)

• REACTIVITY OF AGGREGATE• ALKALI CONTENT IN CEMENT• AVAILABILTY OF MOISTURE• TEMPERATURE CONDITIONS• ALKALI-AGGREGATE REACTION MECHANISM• CONTROL OF ALKALI-AGGREGATE REACTION

FINENESS MODULUS

GRADING AND SURFACE AREA OF AGGREGATE

• GAP-GRADED AGGREGATE• GRADING LIMITS• CRUSHED SAND

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Sieve Size

Percentage of Passing For

GradingZone-I

GradingZone-II

GradingZone-III

GradingZone-IV

10 mm 100 100 100 100

4.75 mm 90 – 100 90 – 100 90 – 100 95 – 100

2.36 mm 60 – 95 75 – 100 85 – 100 95 – 100

1.18 mm 30 – 70 55 – 90 75 – 100 90 – 1000

600 micron 15 – 34 35 – 59 60 – 79 80 – 100

300 micron 5 – 20 8 – 30 12 – 40 15 – 50

150 micron 0 – 10 0 – 10 0 – 10 0 – 15

GRADING LIMITS FOR FINE AGGREGATES IS: 383-1970

Sieve Size (mm)

63 mm 40 mm 20 mm 16 mm 12.5 mm 10 mm

(Percentage of Passing)

80 100 – – – – –

63 85 to 100 100 – – – –

40 0 to 30 85 to 100 100 – – –

20 0 to 5 0 to 20 85 to 100 100 – –

16 – – – 85 to 100 100 –

12.5 – – – – 85 to 100 100

10 0 to 5 0 to 5 0 to 20 0 to 30 0 to 45 85 to 100

4.75 – – 0 to 5 0 to 5 0 to 10 0 to 20

2.36 – – – – – 0 to 5

GRADING LIMITS FOR SINGLE-SIZED COARSE AGGREGATE OF NOMINAL SIZE

Sieve Size (mm)

40 mm 20 mm 16 mm 12.5 mm

(Percentage of Passing for graded aggregate of nominal size, mm)

80 100 – – –

63 – – – –

40 95 to 100 100 – –

20 30 to 70 95 to 100 100 100

16 – – 90 to 100 –

12.5 – – – 90 to 100

10 10 to 35 25 to 55 30 to 70 40 to 85

4.75 0 to 5 0 to 10 0 to 10 0 to 10

2.36 – – – –

GRADING LIMITS FOR COARSE AGGREGATE

GRADING LIMIT OF ALL IN AGGREGATE

Sieve Size

Percentage of Passing For All-in-Aggregate

40 mm Nominal Size 20 mm Nominal Size

80 mm 100 –

40 mm 95 – 100 100

20 mm 45 – 75 95 – 100

4.75 mm 25 – 45 30 – 50

600 micron 8 – 30 10 – 35

150 micron 0 – 6 0 – 6