Technological University of the Philippines Ayala Boulevard, Ermita, Ermita, Manila
College of Engineering Department of Civil Engineering
CE 49L – 49L – 4A 4A Construction Materials and Testing, Lab.
Experiment No. 2
UNIT WEIGHT OF AGGREGATES
Fesalbon, Mayson R. 10-205-041
Date of Submission: August 15, 2013
Engr. Reynaldo O. Baarde Instructor
EXPERIMENT NO.2 UNIT WEIGHT OF AGGREGATES
I.
OBJECTIVE To determine the unit weight of aggregates
II.
MAIN PRINCIPLE 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 particles and the voids between them. The unit weight of fine and coarse aggregates within the ASTM grading limits are generally in the range of 1450 – 1750 kg/cu.m. The unit weight values are used in designing concrete mixtures. Voids in between aggregate particles that can be filled by the mortar can also be calculated.
III.
CALIBRATION OF THE MEASURE 1. 2. 3. 4. 5. 6.
Weigh the measure (Wm) Fill the measure with water to the brim. Cover it with a piece of glass plate in such a way as to eliminate bubbles and excess water. Weigh the water and measure (Ww) Take the temperature of the water and determines its density (Dw), interpolating if necessary. Calculate the volume of the measure (Vm) =
IV.
TEST PROCEDURE A.
R o d d i n g P r o c e d u r e (F o r a g g r eg a t e s h a v i n g a m a x i m u m s i z e o f 4 0 m m o r l e s s )
1. 2. 3. 4. 5.
6. 7.
Fill the measure to one-third its capacity. Tamp the layer of aggregate 25 times with a rod. Fill the measure two-thirds full, and do as above. Fill the measure to overflowing, and do as above. Level the surface of the aggregate. a. For fine aggregate, use a straight edge. b. For coarse aggregates, use your fingers or a straight edge such that any slight projection of the large particles will balance the voids in the surface below the top of the measure. Weigh the measure with the aggregate (Wi) Calculate the unit weight.
B.
J i g g i n g P r o c e d u r e ( Fo r a g g r e g at e s h av i n g a m a x i m u m s i z e f r o m 4 0m m t o 1 0 0m m )
1. 2. 3. 4. 5. 6. 7.
V.
Fill the measure one-third full. Place the measure on a firm base and raise the opposite sides alternately about 50mm and allow the measure to drop freely. Repeat for 50 times, 25 times for each side. Fill the measure two-thirds full and do as above. Fill the measure to overflowing and do as above. Level the surface of the aggregate. Weigh the measure with the aggregate. (Wi) Calculate the unit weight.
CALCULATIONS =
−
Where: Qi Wi Wm Vm
VI.
= unit weight of aggregate (kg/cu.m) = weight of aggregate and measure (kg) = weight of measure (kg) = volume of measure (cu.m)
DATA AND COMPUTATIONS
Test Procedure
Rodding
Jigging
Trial 1
4.26
21.34
Weight of aggregate
Trial 2
4.28
21.11
and measure
Trial 3
4.30
21.24
Average (Wi)
4.28
21.23
Weight of measure (Wm), kg
1.03
3.57
Weight of water and measure (W w), kg
3.05
13.78
23.00
23.00
1 000.00
1000.00
2.025 x 10-3
10.225 x 10-3
1 605.93
1 727.14
Temperature of water, oC Density of water (D w), kg/m3 Volume of measure (V m), m3
Unit Weight of Aggregate (Q i), kg/m3
VII.
SAMPLE COMPUTATIONS Rodding Procedure
= = =
4.260+4.275+4.295 3 − −
= =
= .
3.050−1.025
= . × −
1000.00 4.277−1.025 2.025×10
= . /
Jigging Procedure
= = =
VII.
21.34+21.11+21.24 3 − −
= =
= .
13.795−3.57 1000.00
= . × −
21.23−3.57 10.225×10
= . /
DISCUSSION AND OBSERVATION A.
Discussion
One property of a soil is its unit weight which is defined as the weight of a soil mass per unit volume occupied. In this experiment, the determination of this property was made possible for two soil grading: fine-grained and coarse-grained soils in which it undergoes two different methods namely as rodding and jigging respectively. Calibration. In calibration, determining the weights necessary for this experiment is not as challenging as the determining the volume of the container. Since the shape of the container is irregular, water-displacement method can be used. Given the density of water and the mass of the container and the mass of water in the container, the volume can be determined. The use of glass plate is important first to avoid the water to spill from the container when transferring it to another location and second to ensure that only water was in the container. If bubbles was seen, it only gives us a hint that a fraction of the total volume of the container was occupied by air. Presence of air bubbles can be eliminated (reduced if not possible to eliminate) by sliding the glass plate into the brim of the container. Presence of very small air bubbles can be considered as negligible since in will only occupy a very small percentage of the container’s total volume and will not greatly affect the result of the experiment. Rodding. Its main purpose is to compact the soil sample in such a way that it will attain its more probable densest state to which it will occupy the container. Since a soil cannot be compacted singly, three layers of the soil sample were made to compact in the same number of blows and kind of rod. Rodding was made to free fall so that there would be a uniform compaction effort for every layer. If we’re to apply a force in every layer, there would be
varying compaction effort which can be a source of error in the experiment. Rodding was also made in a regular pattern in such a way that almost all the top layer o f the soil sample was hit by the rod. It is made to attain uniformity and consistency of the procedure. Jigging. As compared to rodding, the soil sample used in jigging was coarse-grained soils. Therefore, rodding is not an option. But using the same principle in rodding, jigging is a method so that coarse-grained soils will attain its densest state to which it will almost occupy the container. Since it is impossible for the coarse-grained soil to occupy spaces in the container, the last procedure for jigging to is to arrange the topmost part of the soil sample lessen the void spaces. B. Observations
During the experiment, the following was observed: 1. 2. 3. 4. 5.
IX.
The soil used in tampering is a fine-grained soil with an almost same consistency of an iron filling. When the soil is rodded, the soil mass compresses and arranges to a denser state. The soil used in jigging are white gravel it an average length of 2cm. When the soil (gravel) was jigged, the gravel changes its arrangement into a denser state. Void spaces are more evident in jigging. Not all of the volume of the container was occupied by the coarse-grained soils
CONCLUSION The unit weight of an aggregate can be determined as a ratio of the weight of the aggregate per unit volume occupied by the aggregate. In a laboratory test, it can be simply determined as shown below. =
−
Where: Qi Wi Wm Vm
= unit weight of aggregate (kg/cu.m) = weight of aggregate and measure (kg) = weight of measure (kg) = volume of measure (cu.m)
