• Author / Uploaded
• Khairunnisa Zakiri

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Title: Bulk Density for Course Aggregate Introduction Bulk density of aggregates is the mass of aggregates required to fill the container of a unit volume after aggregate are batch based on volume. Compacted bulk density can be determined by filling the container in three layers and tamped each layer. Loose bulk density can be determined by filling the container with dried aggregates until it overflows from the container. Objectives To determine of unit weight of bulk density and voids of coarse aggregate. Apparatus  Weighing balance  Weight box (metric)  Cylinder container (3 litres capacity)  Shovel  Tamping rod (16mm long rounded at one end). Procedure A. Compacted Bulk Density 1. The aggregate have been filled in the container in three layers with each layer were being tamped with 25 strokes of rounded end of tamping rod, distributing the strokes evenly over the surface. The container was finally filled to overflowing. 2. Strike off the surplus aggregates have been straight edge by using tamping rod. 3. The container full of aggregates have been weight and the weight, W was recorded in kg. 4. Calculate: Compacted unit weight (bulk density) = W /V Where, W = Weight of compacted aggregate in cylindrical container, kg V = Volume of cylinder container, litre 5. Calculate: The percentage of voids is calculated as follows Percentage of voids = [(Gs – Y )/Gs ]∗100 Where, Gs = Specific gravity of the aggregate

Y = Bulk density in kg/litre B. Loose Bulk Density 1. The aggregate have been filled in the container until overflowing by means of a shovel or scoop, the aggregate was discharged from a height not exceeding 5cm above the top of the measure. 2. The weight if the aggregate have been determined in the measure and the weight, W inkg was recorded. 3. Calculate: Loose unit weight (bulk density) = W /V Where, W = Weight of loose aggregate in cylinder container, kg V = Volume of cylinder container, litre 4. Calculate: The percentage of voids is calculated as follows Percentage of voids = [(Gs – Y )/Gs ]∗100 Where, Gs = Specific gravity of the aggregate Y = Bulk density in kg/litre

Data Acquisition Unit Weight of empty cylinder container

kg

Compacted Weight 3.10

Weight of cylinder container with aggregate Weight of aggregate, W

kg

10.90

10.40

kg

7.80

7.30

litre

3.0

3.0

2.60

2.43

2.26

8.65

Volume of cylinder container, V Bulk density of aggregate, Y Percentage of voids Take Gs : Limestone = 2.66 Bulk density of aggregate, Y:

kg /litre %

Loose Weight 3.10

Compacted unit weight (bulk density) =

=

7.80 kg 3.0 litre

= 2.60 kg /l

Weight of loose aggregate∈cylinder container Volume of cylinder container

Loose unit weight (bulk density) =

=

Weight of loose aggregate∈cylinder container Volume of cylinder container

7.30 kg 3.0 litre

= 2.43 kg /l

Percentage of voids (%): Percentage of voids =

[( Specific gravity of the aggregate – Bulk density )] X 100 Specific gravity of the aggregate

Compacted weight, Percentage of voids ¿

[(2.66 – 2.60)] X 100 2.66

= 2.26% Loose weight, Percentage of voids =

[(2.66 – 2.43)] 2.66

X 100

= 8.65% Discussion From the result above, we have found that the bulk density of aggregate from compacted weight is 2.60kg/l and the loose weight is 2.43kg/l while the percentage of voids from compacted weight is 2.26% and the loose weight is 8.65%. Bulk density is the mass of a unit volume of material in its natural state with pore and voids. Bulk density of aggregate depends upon their packing, the particles shape and size, the grading and the moisture content. Meanwhile, the percentage of voids is the percentage of superficial area which is lost by holes, perforations and cores. From what we can see from the result, we have found that

the bulk density is inversely proportional to the percentage of voids. It is means, when the bulk density is higher, the percentage of voids is decrease.

Conclusion In conclusion, we know the highest bulk density is 2.60kg/l and the void of course aggregate is 2.26%. The higher bulk density, the higher weight of coarse aggregate and less pore space. When the bulk density of coarse aggregate is higher it is means a few of the voids of coarse aggregate can be filled by using fine aggregate and cement.