Field_Lab_Manual
1. AGGREGATE CRUSHING VALUE TEST
AIM
(i) to determine crushing value of given road aggregates;
(ii) to assess suitability of aggregates for use in different types of road pavements.
APPARATUS
The apparatus as per IS: 2386-1963 (part IV) consists of the following:
(i) The test mould-a 15.2 cm diameter open ended steel cylinder with square base plate; plunger having a piston of diameter 15cm, with a hole provided across the stem of the plunger so that a rod could be inserted for lifting or placing the plunger in the cylinder. (ii) A straight metal tamping rod of circular cross-section 16mm in diameter and and 45 to 60 cm long, rounded at one end. (iii) A balance of capacity 5 kg, readable and accurate up to 1 gm. (iv) IS sieves of sizes 25mm, 20mm and 4.75mm. (v) A compression testing machine capable of applying load up to 40 tonnes at a uniform rate of 4 tonnes per minute. (vi) A cylindrical measure having internal diameter 11.5cm and height 18cm.
THEORY
The 'Aggregate crushing value' gives a relative measure of the resistance of an aggregate to crushing under a gradually applied compressive load. It is the percentage by weight of the crushed (or finer) material obtained when the test aggregates are subjected to a specified load under standardized conditions, and is a numerical index of the strength of the aggregate used in road construction. Aggregates with lower crushing value indicate a lower crushed fraction under load and would give a longer service life to the road and hence a more economical performance. Weaker aggregates if used would get crushed under traffic loads, would produce smaller pieces not coated with binder and these would be easily displaced or loosened out resulting in loss of the surface/layer. In short, the aggregates used in road construction must be strong enough to withstand crushing under traffic.
PROCEDURE
The Aggregate Sample: The material for the standard test
AIM
(i) to determine crushing value of given road aggregates;
(ii) to assess suitability of aggregates for use in different types of road pavements.
APPARATUS
The apparatus as per IS: 2386-1963 (part IV) consists of the following:
(i) The test mould-a 15.2 cm diameter open ended steel cylinder with square base plate; plunger having a piston of diameter 15cm, with a hole provided across the stem of the plunger so that a rod could be inserted for lifting or placing the plunger in the cylinder. (ii) A straight metal tamping rod of circular cross-section 16mm in diameter and and 45 to 60 cm long, rounded at one end. (iii) A balance of capacity 5 kg, readable and accurate up to 1 gm. (iv) IS sieves of sizes 25mm, 20mm and 4.75mm. (v) A compression testing machine capable of applying load up to 40 tonnes at a uniform rate of 4 tonnes per minute. (vi) A cylindrical measure having internal diameter 11.5cm and height 18cm.
THEORY
The 'Aggregate crushing value' gives a relative measure of the resistance of an aggregate to crushing under a gradually applied compressive load. It is the percentage by weight of the crushed (or finer) material obtained when the test aggregates are subjected to a specified load under standardized conditions, and is a numerical index of the strength of the aggregate used in road construction. Aggregates with lower crushing value indicate a lower crushed fraction under load and would give a longer service life to the road and hence a more economical performance. Weaker aggregates if used would get crushed under traffic loads, would produce smaller pieces not coated with binder and these would be easily displaced or loosened out resulting in loss of the surface/layer. In short, the aggregates used in road construction must be strong enough to withstand crushing under traffic.
PROCEDURE
The Aggregate Sample: The material for the standard test