Foundation, Concrete and Earthquake Engineering

Specification for Soundness of Fine Aggregates of Concrete (ASTM C33)

Dear reader we have discussed about different tests to determine soundness aggregate for concrete according to both ASTM and BS. In all of these tests, the aggregate are examined to loss of their weight under laboratory disruption conditions done by sodium or magnesium salt solution.

Here we will discuss about ASTM specification for unsound aggregates; our concern is fine aggregates. The weighted average loss of fine aggregate, under five alternative immersions and drying cycles, should not more than 10% when solution used for immersion is sodium sulfate. In case of magnesium sulfate these loss should not more than 15%.

Breaking down of concrete aggregate under freezing-thawing cycles

We have discussed difference between sodium and magnesium solution in testing conditions. We have to know whether we have to reject aggregates failed to pass above requirements. ASTM C33-8.2 and 8.3 provides recommendation in such circumstances as below:

Supplier have to ensure purchasers/specifier, demonstrating that concrete having compatible properties containing similar aggregates essentially from identical sources has provided satisfactory services under identical weathering condition that is expected to be encountered in present work.

When aggregates failed to pass above requirement, i.e. specific weight loss and not have essential services record should be well documented by supplier that it produce satisfactory concrete to sustain and freezing and thawing test according to C666(ASTM).

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