Experiment- Determination Of Unit Weight And Voids Of Aggregares 2

EXPERIMENT- DETERMINATION OF UNIT WEIGHT AND VOIDS OF AGGREGARES OBJECT: TO determine the unit weight (bulk density) and voids of aggregate in compacted and loose condition. APPARATUS: Balance, cylinder Meta measure, a piece of glass plate, tamping rod (16mm diameter, 600mm long rounded at one end). Procedure: Volume determination of the cylindrical measure 1) Determine weight of dry measure. 2) Fill the measure completely full with water and determine the weight of measure plus water. 3) Calculate the weight of water by taking the difference between the measurements obtained in (1) and (2) above. 4) Calculate the volume of the container V = Ww /

γw

Where Ww is the weight of water used to fill the container and w is the unit weight of water. Compact mass determination 1) Determine weight of dry measure. 1) Fill the measure one third full and level the surface with the fingers. 2) Rod the layer of aggregate with 25 strokes of the tamping rod evenly distributed over the surface. 3) Add additional aggregate to the measure to the two thirds full level, level with the fingers, and rod again with 25 strokes of the tamping rod. 4) Finally, add additional aggregate to overflowing and rod again using 25 strokes of the tamping rod. 5) Level the surface of the aggregate with a straightedge.

EXPERIMENT- DETERMINATION OF UNIT WEIGHT AND VOIDS OF AGGREGARES

6) Determine the weight of the measure plus content. Loose mass determination: 1. Empty the cylinder measure. 2. Fill the measure to overflowing by means of a scoop, discharging the aggregate from a height not to exceed 2 in. (50 mm) above the top of the measure. 3. Level the surface of the aggregate with a straightedge. 4. Determine the weight of the measure plus content, and the weight of the measure alone, recording values to the nearest (0.05 kg). 5. Calculate the bulk density in compacted or loose condition by dividing the net mass of aggregates in compact or loose condition in the measure by the volume of measure. CALCULATIONS: Case -1 Weight of empty cylinder = 10400 gm Weight of cylinder + dry loose coarse aggregate = 30700 gm .·. Weight of loose coarse aggregate = (30700-10400) gm = 20300 gm = 20.3 kg Weight of cylinder + tamped coarse aggregate = 35000 gm .·. Weight of compact coarse aggregate = (35000-10400) gm = 24600 gm =24.6 kg Diameter of cylinder = 25 cm Height of cylinder = 30.1 cm Volume of cylinder

=πr2h=

14.7×10³cm³

= 14.7×10¯³m³

EXPERIMENT- DETERMINATION OF UNIT WEIGHT AND VOIDS OF AGGREGARES Loose density = (20.3)/ 14.7×10¯³ kg/m³ = 1.38×10³ kg/m³ Compact density = (24.6)/ 14.7×10¯³ kg/m³ = 1.67×10³ kg/m³ Case-2 Weight of empty cylinder = 10400 gm Weight of cylinder + dry loose coarse aggregate = 3100 gm .·. Weight of loose coarse aggregate = (31100-10400) gm = 20.7 kg Weight of cylinder + tamped coarse aggregate = 32700 gm .·. Weight of compact coarse aggregate = (32700-10400) gm =22.3 kg Hence loose bulk density = (20.7)/ 14.7×10¯³ =1.4×10³ kg/m³ And compact bulk density = 22.3/14.7×10¯³ = 1.5×10³ kg/m³

Bulk Density or Unit Weight: • Bulk density is a measure of the weight of the soil per unit volume usually given on an oven-dry (110° C) basis • Bulk density is not an intrinsic property of a material; it can change depending on how the material is handled. • The bulk density of sand is inversely related to the porosity of the same sand. The more pore space in a soil the lower the value for bulk density. • Bulk density or unit weight depends on Volume is occupied by both the aggregates and the voids between the aggregate particles. Voids:

EXPERIMENT- DETERMINATION OF UNIT WEIGHT AND VOIDS OF AGGREGARES • Void content affects mortar requirements in mix design; water and mortar requirement tend to increase as aggregate void content increases. • Void content between aggregate particles increases with increasing aggregate angularity. • Void contents range from 30-45% for coarse aggregates to about 40-50% for fine aggregates.

Measure

Significance and Use of test: • This test method covers the determination of bulk density ("unit weight") of aggregate in a compacted or loose

EXPERIMENT- DETERMINATION OF UNIT WEIGHT AND VOIDS OF AGGREGARES

condition, and calculated voids between particles in fine, coarse, or mixed aggregates based on the same determination. This test method is applicable to aggregates not exceeding 125 mm [5 in.] in nominal maximum size. • This test method is often used to determine bulk density values that are necessary for use for many methods of selecting proportions for concrete mixtures.