Specific Gravity of Coarse Aggregate
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Experiment No. 3: Specifc Gravity and Water Absorption o Coarse Aggregate Ob ective: To pursue further the Objective of Part A, particularly on the process of determin the bulk and apparent specic gravity (saturated surface-dry, !" and #a absorption of coarse aggregate$ !"eory: pecic gravity is the ratio of the mass or #eight in the air of a unit volume of a material to the mass of the same volume of the #ater at a given temperature$ %t is dimensionless value and, as such, can be e&pressed as bulk specic gravity, bulk specic gravity ( !" or apparent specic gravity ( !" and #ater absorpti These are all based on aggregate that has been soaked in #ater for ' hours$ )ulk specic gravity is the ratio of the #eight in air of a unit volume of aggregat includes the permeable and impermeable voids in the particles but e&cluding the voids bet#een the particles, at a stated temperature to the #eight in air of an e*u volume of gas-free distilled #ater at a stated temperature$ This value is used for calculation of the volume occupied by the aggregate in various mi&tures$ %t is also used if the aggregate is #et, provided that the absorption has been satised$ +onversely, the specic gravity (oven-dry" is used for the computation #hen the aggregate is dry or assumed to be dy$ )ulk pecic gravity ( !" is the ratio of the #eight in air of a unit volume of the aggregate, including the #eight in air of a u volume of the aggregate, including the #eight of #ater #ithin the voids lled to th e&tent achieved by submerging in #ater for appro&imately ' hours at a stated temperature, compared to the #eight in air of e*ual gas-free distilled #ater at a stated temperature$ Apparent specic gravity is the ratio of a unit volume of the impermeable portion o the aggregate at a stated temperature to the #eight in air of an e*ual volume of gas-free distilled #ater at a stated temperature$ %t is the relative density of the material making up the constituent particles, e&cluding the pore space #ithin the particles #hich is accessible to #ater$ Absorption is the increase in the #eight of the aggregate due to the #ater in the pores of the material$ This e&cludes #ater adhering to the outside surface of the particles hence, this is e&pressed as a percentage of the dry #eight$ The aggrega is considered dry #hen it has maintained at a temperature of '' .+/ .+ su0cient time to remove all unconned #ater$ Absorption values are used calculate the change in #eight of an aggregate due to #ater absorbed in the pure spaces #ithin the constituent particles compared to the dry condition, #hen it is deemed that the aggregate has been in contact #ith #ater long enough to satisfy most of the absorption potential$ The laboratory standard for absorption is obtaine
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pecific-Gravity-of-Coarse-Aggregate
Transcript of Specific Gravity of Coarse Aggregate
Experiment No. 3: Specific Gravity and Water Absorption of Coarse Aggregate
Objective: To pursue further the Objective of Part A, particularly on the process of determining the bulk and apparent specific gravity (saturated surface-dry, SSD) and water absorption of coarse aggregate.
Theory:Specific gravity is the ratio of the mass or weight in the air of a unit volume of a material to the mass of the same volume of the water at a given temperature. It is a dimensionless value and, as such, can be expressed as bulk specific gravity, bulk specific gravity (SSD) or apparent specific gravity (SSD) and water absorption. These are all based on aggregate that has been soaked in water for 15 hours.Bulk specific gravity is the ratio of the weight in air of a unit volume of aggregate. It includes the permeable and impermeable voids in the particles but excluding the voids between the particles, at a stated temperature to the weight in air of an equal volume of gas-free distilled water at a stated temperature. This value is used for calculation of the volume occupied by the aggregate in various mixtures. It is also used if the aggregate is wet, provided that the absorption has been satisfied.Conversely, the specific gravity (oven-dry) is used for the computation when the aggregate is dry or assumed to be dy. Bulk Specific gravity (SSD) is the ratio of the weight in air of a unit volume of the aggregate, including the weight in air of a unit volume of the aggregate, including the weight of water within the voids filled to the extent achieved by submerging in water for approximately 15 hours at a stated temperature, compared to the weight in air of equal gas-free distilled water at a stated temperature. Apparent specific gravity is the ratio of a unit volume of the impermeable portion of the aggregate at a stated temperature to the weight in air of an equal volume of gas-free distilled water at a stated temperature. It is the relative density of the solid material making up the constituent particles, excluding the pore space within the particles which is accessible to water.Absorption is the increase in the weight of the aggregate due to the water in the pores of the material. This excludes water adhering to the outside surface of the particles; hence, this is expressed as a percentage of the dry weight. The aggregate is considered dry when it has maintained at a temperature of 110C5C for sufficient time to remove all unconfined water. Absorption values are used to calculate the change in weight of an aggregate due to water absorbed in the pure spaces within the constituent particles compared to the dry condition, when it is deemed that the aggregate has been in contact with water long enough to satisfy most of the absorption potential. The laboratory standard for absorption is obtained after submerging the dry aggregate for approximately 15 hours in water. An aggregate mined from below the water table may have a higher absorption when used. Conversely, some aggregates when used may contain an amount of absorbed moisture less than the 15 hours soaked condition for an aggregate that has been in contact with water and that has free moisture on the particle surfaces, the percentage of free moisture can be determined by deducting the absorption from the total moisture content determination.Apparatus:Balance (sensitivity of 1g)Wire basket (3.35mm (No.6) or finer mesh)Watertight tankSieve #4 (4.75mm)
Preparation of Sample Specimen:1. Thoroughly mix and reduce to the approximate quantity of the needed sample aggregate.2. Thoroughly apply dry sieving and washing to reject all materials passing through the No.4 sieve(4.75mm)3. Refer to the following table for the minimum weight of the test sample to be used.
Max size of sieve (in.)Min. weight of test sample (kg)
2
3
14
1 5
28
2 12
316
3 25
440
4 50
575
6125
Procedure:1. Dry the test sample at a temperature of 110C 5C until a constant weight is achieved.2. At room temperature, cool the aggregate in air for 1 to 3 hours, subsequently immersing it in water.3. Remove the test sample from the water and roll it in a large absorbent cloth to remove all visible films of water. Individually wipe the larger particles. This drying operation may be conducted with the aid of a moving stream of air, although care should be taken to avoid evaporation of water from the aggregate pores.4. Weight the test sample in a saturated surface-dry condition. As with all the subsequent weights to be obtained, record the values to the nearest 1.0g.5. After the weighing, immediately place the saturated surface-dry test sample in the basket-wire and determine its weight in water. Care should be taken to ensure that all entrapped air is removed.6. Take care to remove all entrapped air before weighing by shaking the container while immersed.7. Dry the test sample to constant weight at a temperature of 110C 5C. Cool in air at room temperature 1 to 3 hours or until the aggregate has cooled to a temperature that is comfortable to hand and weigh.
Formulas:1. Bulk sp. Gr. =
2. Bulk sp. Gr. (SSD) =
3. Apparent sp. Gr. =
4. Absorption. % =
Where:A = weight of the dry test sample in air, g.B = weight of the saturated surface dry test sample in air, g.C= weight of the saturated test sample in water, g.
Experiment No. 3: Worksheet ReportSpecific Gravity and Water Absorption of Coarse Aggregate
Project Name: ____________________________________________________________________________________________________________________________________________________________
Tested By: _____________________________________________________________________
Date: ___________________
No. of Trials12
Wt. of sample (SSD), B, g.
Wt. of bucket + sample in water, C, g.
Wt. of dry aggregate, A, g.
Bulk sp. Gr =
Bulk sp. Gr (SSD) =
Apparent sp. Gr. =
Absorption, % =
Average Bulk Specific Gravity = _____________________________________________________Average Bulk Specific Gravity (SSD) = ________________________________________________Average Apparent Specific Gravity = _________________________________________________Average Absorption, % = __________________________________________________________
