OBJECT: INTRODUCTION TO LABORATORY AND HEALTH, SAFETY & ENVIRONMENT MEASURES (HSE)
PERFORMANCE OBJECTIVE:
Introduction to the laboratory equipment used for different tests and HSE measures.
DISCUSSION:
The road structure is mainly consisting of the following ingredients:
i) Aggregate (Crushed Stones) ii) Binding Material (Bitumen)
1. TESTS ON ROAD AGGREGATES
Aggregates form the major part of the pavement structure and are the prime material used in road construction. The following tests are performed to know the suitability of the aggregate according to the requirement:
S.No | Aggregates Tests | Purpose |
1 | Los Angeles Abrasion Value (% wear) | |
2 | The flakiness and elongation index | |
3 | The aggregate impact value | |
4 | The soundness value | |
5 | Specific gravity and water absorption test |
I. Aggregate Crushing Value Test
The aggregate crushing test is the indirect measure of the crushing strength of the aggregates.
II. Abrasion test
Due to traffic movement, the road stones used in the surfacing course are subjected to wearing action at the top. Resistance to abrasion or hardness is an essential property for road aggregates, especially when wearing a course. Thus, road stones should be hard enough to resist the abrasion due to traffic.
III. Aggregate impact test
The aggregate impact test is considered to be an important test to assess the suitability of aggregate as regards the toughness for use in pavement.
IV. Soundness test
The soundness test is useful to assess the resistance of the aggregate to weathering action.
V. Specific gravity and water absorption test
This test is performed to assess the specific gravity of the road aggregate. As higher the specific gravity of aggregate, the higher its strength.
VI. Shape test
In pavement construction, flaky and elongated particles are to be avoided, particularly in the surface course. If flaky and elongated aggregates are present in appreciable proportions, the strength of the pavement layer would be adversely affected due to the possibility of breaking down under loads.
VII. Stripping value of the road aggregates
Bitumen and tar adhere well to all normal types of road aggregates, provided they are dry and are not exceptionally dusty. The process of binding is controlled largely by the viscosity of the binder. When the viscosity of the binder is high, the coating of aggregate by the binder is slower.
2. TESTS ON BITUMINOUS MATERIALS
The binder used in pavement construction includes both bitumen and tar. The bitumen is brought to sufficient fluidity or viscosity before use in pavement construction.
Generally, the following lab experiments are conducted on bitumen.
I. Penetration test
A penetration test is used to grade the bitumen in terms of hardness.
II. Ductility test
A certain minimum ductility is necessary for a bitumen binder. This is because of the temperature changes in the bitumen mixes and the repeated deformations that occur in flexible pavements due to the traffic loads.
III. Softening point test
The softening point is essentially the temperature at which the bituminous binder becomes softened and has an equal viscosity.
IV. Specific gravity test for bitumen
Specific gravity is useful to identify the source of a bituminous binder. Pure bitumen has a specific gravity in the range of 0.97 to 1.02. In case the bitumen contains mineral impurities, the specific gravity will be higher.
V. Viscosity test
Viscosity is defined as the inverse of fluidity. Viscosity thus defines the fluid property of bituminous material.
VI. Flash and fire point test
Bituminous materials leave out volatiles or flumes at high temperatures depending upon their grade. These volatile vapors catch fire, causing a flash. This condition is very hazardous, and it is, therefore, essential to qualify this temperature for each bitumen grade so that the paving engineers may restrict the mixing or application temperature as well within the limits.
4. TESTS ON BITUMEN MIXES
Bitumen mixes are used in the surface coarse of road and airfield pavements; some types of bituminous mixes are also used in the base and/or binder courses of flexible pavements. The bituminous mixes may be divided into two categories based on the gradation of coarse and fine aggregates in the mix.
Generally, the following lab experiments are conducted.
I. Marshal stability test
II. Hveem Stabilometer and Cohesiometer test
HEALTH, SAFETY, AND ENVIRONMENT PRECAUTIONS AND INSTRUCTIONS
1. The students may not operate any equipment without permission or supervision of the lab technician or lab supervisor.
2. The students have to follow proper guidelines given by the lab technician.
3. The students have to use equipment carefully and clean it before and after performing practicals.
4. The students must be careful while using electrical and temperature-operating equipment.
5. The students must be conscious of the use of the chemicals.
6. The students must know the location of safety equipment and their usage.
7. The students have to use the right and required tools for the job.
8. In case of any accident or mishap, the students must immediately report the teacher or lab technician.
9. The students have to wash their hands properly before and after performing practicals.
10. Loose clothes are prohibited in the laboratory.
11. The students must wear the toe shoe during the practicals; sandals/slippers are not allowed in the laboratory. Keep solids out of the sink.
12. The use of mobile phones is not allowed in the laboratory.
13. The students and to avoid unnecessary talk with each other.
14. The students may not eat, drink, or chew anything in the laboratory.
15. The students have to maintain a pleasant environment in the laboratory
16. Light and SuiGas must be switched off properly when the last person is out of the laboratory.
