Soundness of Aggregates by use of Sodium Sulphate OR Magnesium Sulphate

Test Specifications

ASTM C 88-99a

Apparatus

1. Sieves
2.  Containers
3. Weighing Balance
4.  Oven

Related Theory

This test method covers the testing of aggregates to estimate their soundness when subjected to weathering action in concrete or other applications. This is accomplished by repeated immersion in saturated solutions of sodium or magnesium sulfate followed by oven drying to partially or completely dehydrate the salt precipitated in permeable pore spaces. The internal expansive force derived from the rehydration of the salt upon re-immersion simulates the expansion of water on freezing.

Procedure

1. Immerse the sample in the prepared solution of sodium sulfate or magnesium sulfate for not less than 16 h nor more than 18 h in such that solution covers them to a depth of at least 0.5 in.
2.  Cover the container to protect from external substances and extra evaporation.
3.  Maintain temperature between 21 ± 1 ^oC
4. After submersion of 16h let the sample drain for 15 min and the keep in oven for drying at temperature 110 ± 5 ^oC
5. Let the sample dry until constant weight has been achieved. Constant weight will be considered to have been achieved when weight loss is less than 0.1 % of sample weight in 4 h of drying.
6. Repeat above steps for number of times.
7. After completion of final cycle wash the sample and Sieve the fine aggregate over the same sieve on which it was retained before the test Weigh the material retained on each sieve and record each amount. The difference between each of these amounts and the initial weight of the fraction of the sample tested is the loss in the test and is to be expressed as a percentage of the initial weight for use in Table.

Observations and Calculations

Comments:

Los Angeles abrasion test on aggregate

Test Specifications

AASHTO: T 96-02 ASTM C-131 ASTM C-535

Apparatus

1. Los Angeles abrasion machine,
2. Sieves conforming to ASTM standards.
3. Balance.
4. Abrasive charge i.e. steel spheres  inches in diameter and each weighing 390-445 gram.

Related Theory

This test is used to assess the hardness of aggregate used in road construction. The road aggregate is subjected to wearing action by the moving traffic and therefore resistance to wear or hardness is an essential property of the aggregate should be hard enough to resist abrasion due to traffic.

Los Angeles abrasion test is used to find out percentage wear due to relative rubbing action between aggregates and steel balls used as abrasive charges. Pounding action of these balls also exits while conducting the test. The test is considered more dependable as rubbing and pounding action simulate field conditions.

The test has been standardized by ASTM and AASHTO. FHWA recommendations are that coarse aggregate for dense graded mixes have a percent wear of 50% or less. For open graded mixes or where requirements are more exacting, the requirement is of 40% or less.

Procedure

The sample taken should be representative and conforming to any of the grading given in the table attached.

The sample is placed in the cylinder along with the abrasive charges and the machine is rotated for required number of revolutions (500-1000). After the required number of revolutions the material is discharged from the machine and sieved through # 12 US sieve. Wash the material coarser than # 12 sieves, oven dry and weigh.

Los Angeles Abrasion Value =  x100

Table 4.1:       Grading of Test Samples

Sieve size	Weight of test sample in (gm)
Passing (mm)	Retained on (mm)	A	B	C	D
40	25	1250
25	20	1250
20	12.5	1250	2500
12.5	10	1250	2500
10	6.3			2500
6.3	4.75			2500
4.75	2.36				5000

Table 4.1:       Selection of Abrasive Charge

Grading	No of Steel Balls	Weight of Charge (gm)
A	12	5000 ± 25
B	11	4584 ±25
C	8	3330 ± 20
D	6	2500 ± 15

Observations and Calculations

Grading used for the test                                            =                     

Material taken for the test:

                                                                                    =                     

                                                                                    =                     

Number of abrasive charges used                               =                     

Original weight of the test sample, W₁                       =                     

Final weight after test (retained on # 12), W₂            =                     

Los Angeles Abrasion value,                                      =                     

Results

Los Angeles Abrasion value                                       =         

Comments: