Dear reader we have provided some limits and physical properties of coarse aggregates of concrete in previous post, where some limitation and modification required that will be discussed here.
In case of abrasion requirements, crushed and air-cooled BFS (Blast furnace slag) is not included. The rodded bulk density or unit weight of this material should not be less than 70 lb/ft3. While determining bulk density the grading of it should identical to grading of aggregates to be used in concrete.
In case of determining abrasion loss of crushed stone, crushed gravel or gravel, the grading of sample aggregates and also sizes of sample aggregates should be similar to or nearly similar to corresponding aggregates to be used in concrete.
When aggregates are composed of different grading, the abrasion limit provided should be applied to each.
While determining material finer than passing No.200 sieve, expressed as percentage, following conditions are considered:
a. This value may be increased 1.5 times when the material is free from shales or clay.
L=percentage limit in coarse aggregate can be increased
P=percentage of sand in concrete over total aggregate
T=allowable limit of fine particles in fine aggregate
i.e. 3% for concrete that subjected to abrasion
5% for all other concrete
A=actual quantity in fine aggregate