Foundation, Concrete and Earthquake Engineering

Required Properties of Concrete Aggregate in Negligible Weathering Region; ASTM C33

A region can be said to be under negligible weathering, where concrete hardly exposed to detrimental effect of freezing under presence of moisture. Here we will include limits of deleterious substances and also expected physical properties of aggregate to be used in such weathering regions. Dear reader we have already discussed about deleterious substances that are found in aggregates. Aggregates are classified as 1N and 2N. ‘N’ stands for negligible weather condition, we can easily gaze this.

ASTM do not specified limits of chart having specific gravity less than 2.4 and no information about soundness (tested under magnesium sulfate for 5 cycles). We have discussed many posts about soundness of aggregate; you can read this for more information. We are providing a table to specify the limits and properties:
Concrete aggregate properties for negligible weathering region
1N- in this class designation the concrete location or types includes:

    Lignite and coal in concrete aggregate
  • Concrete slabs that are subjected to abrasion due to traffic

  • Bridge floor

  • Bridge deck and side walk

  • Pavements

2N-includes all other concrete; types or location other than for 1N.

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.
Weak concrete having aggregates containing fine particles
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.

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 by
Increased percentage limit in concrete coarse aggregate

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 

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