Dear reader we have already discussed class designation of aggregate for concretes, subjected to severe weathering exposure. Of these 4S class are expose to abrasion as most application are road, bridge and water-front structures.
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 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.
b. If fine aggregates used in concrete have particles passing No. 200 sieve is less than that specified in ASTM C33, then percentage limit in coarse aggregate can be increased byL=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