The unit weight of a material can be defined as the weight of a given volume of graded aggregate. It effectively measures the volume that the graded aggregate will occupy and includes both solid pa...
Laboratory Activity in Geotechnical engineering
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EXPERIMENTEXPERIMENT- DETERMINA DETER MINATION TION 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: APPARA TUS: Balance, cylinder Meta measure, a piece p iece 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 measure completely full with water and determine 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 volume of the container V = Ww /
γw
Where Ww is the weight of water used to fill the container and u nit weight of water. water. w is the unit Compact mass determination 1) Determine weight of dry measure. 1) Fill the measure measure one third full full and level the surface surface with the fingers. 2) Rod the layer of aggregate aggregate with 25 strokes 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 strokes of the tamping rod. 4) Finally, add additional aggregate to overflowing overflowing and rod again using 25 strokes of the tamping rod. 5) Level the surface of the the aggregate with with a straightedge.
EXPERIMENTEXPERIMENT- DETERMINA DETER MINATION TION OF UNIT WEIGHT AND VOIDS OF AGGREGARES
6) Determine the weight of the measure plus content. Loose mass determination: 1. Empty the cylinder cylinder measure. measure. 2. Fill the measure measure to overflowi overflowing ng 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 the surface of the aggregate aggregate with with a straightedge. straightedge. 4. Determine Determine the weight weight of the measure measure plus content, content, and the weight of the measure alone, recording values to the nearest (0.05 kg). 5. Calculate Calculate the bulk density density in compacted compacted or loose condition 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 d ry loose coarse aggregate agg regate = 30700 gm .·. Weight of loose coarse aggregate aggregate = (30700-10400) (30700-10400) gm = 20300 gm = 20.3 kg Weight of cylinder + tamped coarse aggregate = 35000 gm .·. Weight of compact coarse aggregate aggregate = (35000-10400) (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
EXPERIMENTEXPERIMENT- DETERMINA DETER MINATION TION OF UNIT WEIGHT AND VOIDS OF AGGREGARES Loose density = (20.3)/ 14.7×10¯³ 14.7×10¯³ kg/m³ kg/m³ = 1.38×10³ 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 d ry loose coarse aggregate agg regate = 3100 gm .·. Weight of loose coarse aggregate aggregate = (31100-10400) (31100-10400) gm = 20.7 kg Weight of cylinder + tamped coarse aggregate = 32700 gm .·. Weight of compact coarse aggregate aggregate = (32700-10400) (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 de nsity = 22.3/14.7×10¯³ = 1.5×10³ kg/m³
Bulk Density or Unit Weight: •
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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:
EXPERIMENTEXPERIMENT- DETERMINA DETER MINATION TION OF UNIT WEIGHT AND VOIDS OF AGGREGARES •
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Void content affects mortar requirements in mix design; water and mortar requirement tend to increase as aggregate void content increases. Void content between b etween 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
EXPERIMENTEXPERIMENT- DETERMINA DETER MINATION TION OF UNIT WEIGHT AND VOIDS OF AGGREGARES
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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.
