aggregrates Flashcards
are granular materials which are mixed with binding materials such as cement or lime for manufacturing of mortar or concrete
aggregates
serves as a helping material to make concrete mixes more compact. It also decreases the consumption of cement and water and contribute to the mechanical strength of the concrete, making them an essential ingredient in the construction and maintenance of rigid structures.
aggregate
When the aggregate size is less than 4.75mm
COARSE
AGGREGATES
When the aggregate
size is greater than
4.75mm
FINE AGGREGATES
When the aggregate size is greater than 4.75mm
COARSE AGGREGATES
To determine the particle size distribution of fine and
coarse aggregates by sieving
sieve analysis
To determine the water absorption of aggregates
Water absorption
To determine the abrasion value of aggregates
Aggregate abrasion value
To determine the impact value of aggregates
Aggregate impact value
To determine the crushing value of aggregates
Aggregate crushing value
FOUR PRIMARY LOCATION FOR AGGREGATES SAMPLING COLLECTION
Flowing Aggregate Stream
Converyor Belt
Stockpiles
Roadways
commonly known as gradation test
sieve analysis
the distribution of aggregate particles, by size, within a given sample.
gradation
it is a measure of how well distributed the sizes of the particles in an aggregate are
aggregate grading
CHARACTERISTICS OF A WELL- GRADED AGGREGATE
Good Workability
Reasonable Mix
Good Compaction
Better Resistance
Low Strength and Shrinkage
The sample for sieving should be prepared
from the larger sample either by
quartering or by means of a sample divider
sieve analysis apparatus
set of sieves of diff. sizes
balance or scale
mechanical sieve shaker
sieve analysis procedure
The test sample is dried to a constant weight at a temperature of 110 + 5oC and weighed.
The sample is sieved by using a set of IS Sieves. Nest the sieves in order of decreasing size from top to bottom and begin agitating and shaking the sample for a sufficient amount of time.
After the material has been sieved, remove each tray, weigh each size, and record each weight to the nearest 0.1 g.
sieve analysis reporting of results
The results should be calculated and reported as:
- the cumulative percentage by weight of the total sample
- the percentage by weight of the total sample passing through one sieve and retained on the next smaller sieve, to the nearest 0.1 percent.
water absorption apparatus
Wire basket - of not more than 6.3mm mesh or a perforated container of convenient size with thin wire hangers for suspending it from the balance.
Setup of Water Absorption Test The setup consists of container for filling water and suspending the wire basket in it and an airtight container of capacity similar to that of basket, a shallow tray and two dry absorbent clothes.
water absorption procedure
About 2 kg of aggregate sample is taken, washed to remove fines and then placed in the wire basket. The wire basket is then immersed in water, which is at a temperature of 220C to 320C.
Immediately after immersion the entrapped air is removed from the sample by lifting the basket 25 mm above the base of the tank and allowing it to drop, 25 times at a rate of about one drop per second
The basket, with aggregate are kept completely immersed in water for a period of 24 ± 0.5 hour.
The basket and aggregate are weighed while suspended in water, which is at a temperature of 220C to 320C.
The basket and aggregates are removed from water and dried with dry absorbent cloth.
The surface dried aggregates are also weighed. (M1)
The aggregate is placed in a shallow tray and heated to 100 to 1100C in the oven for 24 ± 0.5 hours.
Later, it is cooled in an airtight container and weighed. (M2)
is the value that determine aggregate toughness and abrasion resistance
aggregate abrasion value
this test is carried out by AASHTO T 96 or ASTM C 131 : Resistance to Degradation of Small - Size Coarse Aggregate by Abrasion and Impact
los angeles abrasion test
los angeles abrasion test apparatus
los angeles abrasion testing machine
1.7mm sieve
oven
Abrasive charge - 12 nos. cast iron or steel spheres approximately 48 mm diameter and each weighing between 390 and 445g ensuring that the total weight of charge is 5000 + 25g
abrasion test procedure
Place the test sample and the abrasive charge should be placed in the Los Angeles abrasion testing machine. Set the machine to rotate at a speed of 20 to 33 revolutions/minute for 1000 revolutions.
At the completion of the test, the material should be discharged and sieved through 1.70mm IS Sieve.
