Specific Gravity and Absorption of Coarse and Fine Aggregates
Objectives:
To determine and calculate various types of specific gravity and absorption of fine and coarse aggregates used in concrete and bituminous construction. Properties of fine and coarse aggregates to be determined: Bulk Specific Gravity Bulk Specific Gravity for Saturated Surface-Dry aggregates Apparent Specific Gravity Absorption
Theory:
According to AASHTO T85, Bulk T85, Bulk Specific Gravity is Gravity is the ratio of the weight in air of a unit volume of aggregate ag gregate at a stated temperature to the weight in air of an equal volume of gas-free distilled water at the stated temperature. The difference between bulk specific gravity and apparent specific gravity consists in the fact that Apparent that Apparent Specific Gravity accounts Gravity accounts only for the impermeable portion of the aggregate and does not include the permeable pores. Bulk pores. Bulk Saturated Surface-Dry Specific Gravity does include the weight of water from the permeable voids of the aggregate that has ha s been soaked in water. It is important to notice that for the Saturated Surface-Dry condition the aggregate is saturated after it absorbs the water to fill the void spaces but the excess water from the surface must be removed. The specific gravity and absorption values are critical in determining air voids and the amounts amou nts of moisture that can be absorbed. The numbers obtained in an experiment might seem small, but if applied to projects with high volumes of aggregate, these numbers can become very significant. Specific Gravities for coarse materials can be calculated from the following equations: Factors: A=Oven-dry sample in air, g B=Saturated surface-dry weight in air, g C=Weight of aggregate in water, g Equations:
Bulk SG =
(1)
Bulk (SSD) SG =
Apparent SG =
(2)
(3)
Absorption (%) =
(4)
For the fine grained materials following factors and equations (5) to (7) can be used. Factors: A = Weight of the saturated surface-dry materials in air, g. C = Weight of the flask with materials, water and plate, g. D = Weight of the flask, water and plate, g. E = Weight of the immersed materials, g. (C-D) G = Weight of the pan with the sample, g. H = Tare weight of the pan, g. I = Dry weight of the sample, g. (G-H) Equations: Bulk SG =
(5)
Apparent SG =
Absorption (%) =
(7)
(6)
The acceptable range of test results among samples is as follows: Coarse: Bulk SG (Dry) = 0.025 Apparent SG = 0.020 % Absorption = 0.25
Fine: Bulk SG (Dry) = 0.032 Apparent SG = 0.027 % Absorption = 0.31
During the experiment it is necessary to run at least two samples. A third sample may be run and used as backup. Two individual samples must fall within the acceptable ranges. If they do not agree with the range, the tests must be re-run.
Apparatus:
For Fine Grained: Balance – readability and sensitivity of 0.1g Erlenmeyer flask – 500 ml capacity
Glass Plate – must be flat and level Mold – if the form of a frustum of a cone Tamper – metal tamper (conforming with AASHTO T85) Drying Apparatus – in this experiment we used hair dryers Pyrex pan
For Coarse Grained: Balance – readability and sensitivity of 0.1g Sample container – a wire basket that prevents water to be trapped Absorbent Toweling – terry cloth or a towels Water Tank – large enough to allow the sample be completely submerged
Procedure:
Specific Gravity and Absorption of Coarse Aggregate: 1. The aggregate was soaked in clear water for approximately 24 hours. 2. A necessary amount of aggregate was taken from the soaking container and surface-dried using towels and cloth. The saturated surface-dry (SSD) state was reached when the samples appeared damp but did not shine and did not have any excess water on the surface. 3. The sample was immediately weighed and the SSD weight was recorded. 4. The wire basket was suspended from the scale, fully immersed in water and tared. It is important to ensure that no air bubbles were trapped, that the container does not touch the sides of the tank and is completely immersed including the handle. 5. The sample was placed in the tared container, submerged in water and the immersed weight measurement was taken. 6. The sample was dried and allowed to cool to room temperature. It was then weighed and the oven-dry weight was recorded.
Specific Gravity and Absorption of Fine Material:
1. The material has been soaked in clear water for approximately 24 hours. 2. A sample of about 500g was removed from soaking and placed into a pan for drying. In order to speed up the process, a hair dryer was used as apparatus. The sample was dried to the SSD condition. 3. To ensure that the material has reached the SSD state, it was placed in the mold and lightly compressed using the tamper. A total of 25 drops, each from 0.2” above the top of the sample, were evenly distributed other the sample’s surface. After removing the mold, if the material slumps only slightly, it has reached the S SD condition. 4. The surface-dry material was placed in an Erlenmeyer flask and filled with water. All air bubbles were removed and the flask with the material, water and plate was weighed.
5. The sample was poured out into a pan and set in an oven for drying. It is necessary to ensure that all particles from the flask were moved to the pan. 6. After the sample had dried for about 24 hours, it was removed from the oven and the oven-dry weight was measured.
All measured data was recorded on a worksheet and further analyzed as described in Data Analysis section.
Data Analysis: SPECIFIC GRAVITY: FINE A GGREGATE Menards Play Sand Descripton A. SSD wt, g B. Flask ID# C. Flask, Water, Sand, Plate wt, g D. Flask, Water, Plate wt, g E. Immersed Sand wt, g F. Pan ID# G. Dry Pan, Sand wt, g H. Pan wt, g I. Dry Sand wt, g Adsorption wt, g A-I P erce nt A dso rb ti on ( A- I) /I *100 Bulk Dry SG I/(A-E) Apparent Dry SG I/(I-E)
1
Quartz Manufactured Sand
2
3
4
2.620 2.740
2.634 2.728
2.610 2.652
2
3
4
2.664 2.789
2.670 2.786
2.680 2.797
Limestone Sand
Average
1
2
3
2.623
2.718
2.590 2.646
2.596 2.648
2.601 2.658
Average
1
2
3
2.596
2.651
2.498 2.742
2.627 2.799
2.647 2.801
Average
502.3 1200.2 887.5 312.7 #3 643.7 145.6 498.1 4.2 0. 85 2.627 2.687
2.637
2.800
SPECIFIC GRAVITY: COARSE AGGREGATE Hard Limestone Gravel Description A. SSD wt, g B. Immersed Gravel wt, g C. Pan ID# D. Dry Pan, Gravel wt, g E. Pan wt, g F. Dry Gravel wt, g Adsorption A-F Percent Adsorption (A-F)/ F*100 Bulk Dry SG F/(A-B) Apparent SG F/(F-B)
1
Soft Limestone Gravel
Granite Gravel
Average
1
2
3
2.671
2.791
2.480 2.760
2.501 2.746
2.498 2.742
Average
1
2
2.493
2.749
2.655 2.698
2.677 2.700
Average
1786.9 1800.9
2.666
2.699
PRECISION ANALYSIS Bulk Dry Specific Gravity Mat eri al Menards Play Sand Quartz Manufactured Sand Limestone Sand Hard Limestone Gravel Soft Limestone Gravel Granite Gravel
A cce pt ab le Ra nge 0.025 0.025 0.025 0.032 0.032 0.032
LEGEND 2. XX
Apparent Specific Gravity
Ex pe ri me nt al Ran ge A cce ptab le Ran ge 0.024 0.011 0.02 0.016 0.021 0.022
0.02 0.02 0.02 0.027 0.027 0.027
Percent Absorption
Ex pe ri me ntal Ran ge A cce pt ab le Ran ge 0.012 0.012 0.002 0.011 0.018 0.002
0.25 0.25 0.25 0.31 0.31 0.31
Ex pe ri me nt al Ran ge N/A N/A N/A N/A N/A N/A
: Re je ct ed D ata ( out li ers )
Summary:
Material Menards Play Sand Quartz Manufactured Sand Limestone Sand Hard Limestone Gravel Soft Limestone Gravel Granite Gravel
Bulk Dry Specific Gravity 2.623 2.596 2.637 2.671 2.493 2.666
Apparent Specific Gravity 2.718 2.651 2.800 2.791 2.749 2.699
The data analysis portion of the experiment yields bulk dry specific gravity and apparent specific gravity. Experimental data gathered can also be analyzed to calculate bulk saturated surface dry (SSD) specific gravity and percent absorption. These quantities are used along with additional soil properties to calculate various useful characteristics of a given soil. In this case, not enough information has been gathered for the multiple experimental trials to accurately calculate bulk SSD specific gravity or percent absorption. These quantities have
Summary:
Material Menards Play Sand Quartz Manufactured Sand Limestone Sand Hard Limestone Gravel Soft Limestone Gravel Granite Gravel
Bulk Dry Specific Gravity 2.623 2.596 2.637 2.671 2.493 2.666
Apparent Specific Gravity 2.718 2.651 2.800 2.791 2.749 2.699
The data analysis portion of the experiment yields bulk dry specific gravity and apparent specific gravity. Experimental data gathered can also be analyzed to calculate bulk saturated surface dry (SSD) specific gravity and percent absorption. These quantities are used along with additional soil properties to calculate various useful characteristics of a given soil. In this case, not enough information has been gathered for the multiple experimental trials to accurately calculate bulk SSD specific gravity or percent absorption. These quantities have therefore been omitted from the analysis. Data analysis has however been performed for bulk dry specific gravity and apparent specific gravity.
Bulk Dry Specific Gravity The ratio of the unit weight of a given soil including air voids to the unit weight of water Bulk SSD Specific Gravity The ratio of the unit weight of a given soil including voids saturated with water to the unit weight of water Apparent Specific Gravity The ratio of the unit weight of only the impermeable solids portion of a given soil to the unit weight of water Percent Absorption The increase in weight of a soil sample due to the infiltration of water into the pore spaces expressed as a percent of the weight of the sample after infiltration
