Aim
To determine the bulk density and percentage voids of aggregate .
Apparatus
(I)Balance -A balance sensitive to 0.5% of the weight of the sample to be weighed .
(ii) Cylindrical Metal Measure- The measure shall be of 3,15 or 30 liters capacity and shall comply with the requirements given below.
.
.
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Size of largest particle | Nominal capacity |
4.75mm and under | 3 liters |
Over 4.75 mm to 40mm | 15 liters |
Over 40mm | 30 liters |
4. Tamping Rod– A straight metal tamping rod of cylindrical cross section 16 mm in diameters 60 cm long , rounded at one end .
Calibration
The measure shall be calibrated by determine the weight of water at 27oC required to fill it such that no meniscus is present above the rim of the container. The capacity in liters shall be obtained by dividing the weight of water in kg required to fill the container at 27 oC by the weight of water in one liter at 27oC which is 0.1 kg.
Procedure
Take the weight of empty measure (W)
(ii) Fill the measure with aggregates sample for about one third height and tam evenly with 25 strokes of the rounded end of the tamping rod
(iii) Add a similar quantity of aggregate as second layer and tamp it evenly with 25 strokes.
(iv) Fill the measure with a third layer of aggregate up to over following and tamp it with 25 strokes
(v) Strike off the surplus aggregate using the tamping rod as a straight edge.
(vi) Take the weight (w1)
(vii) Empty the measure and fill it again to over flowing by means of a shovel, the aggregate being discharged from a height not exceeding 5 cm above the top of the measure.
(viii)Level the surface of the measure and weight it (w2).
Note
The experiment should be done for coarse and fine aggregates
CALCULATIONS
Coarse AGGREGATE
Diameter of metal measure =
Volume of metal measure (v) =
(W1-W )
Bulk density of compacted coarse aggregates = ——————–
V
Bulk density of loosely packed aggregates= (W2-W)/V
Percentage of voids =100x (Gs-r)/ Gs
Where Gs = Specific gravity of aggregate
r = Bulk density of aggregate in kg / liter.
FINE AGGREGATE
Diameter of metal measure =
Volume of Metal measure (v) =
Bulk density of compacted coarse aggregate = ( W1-W )/V
Bulk density of loosely packed aggregates= (W2-W)/V
Percentage of voids= (Gs-r)x100/ Gs
Where Gs = Specific gravity of aggregate
r = Bulk density of aggregate in kg / liter.
Results
Bulk density of compacted coarse aggregate =
Bulk density of loosely packed coarse aggregates =
Bulk density of compacted fine aggregate =
Bulk density of loosely packed fine aggregates =
Percentage of voids of coarse aggregate =
Percentage of voids of fine aggregate =