# Compressive Strength

PCC is most often known by its compressive strength. This is because PCC is much stronger in compression than it is in tension and thus, is often used in compression. The ACI Concrete Code gives some rough rules-of-thumb for converting compressive strength to tensile and flexural strength:

## Description

Compressive strength is most often measured by forming 150 mm diameter, 300 mm long (6 inch diameter, 12 inches long) test cylinders and then breaking them at a specified age (typically 28 days) although it can also be performed on specimens of different sizes and origins (such as field cores or the remnants of a flexural test).

Some state agencies use compressive strength as a field quality assurance measurement of a flexural strength specification. Flexural strength is first correlated to compressive strength based on mix design test results. Then, using this correlation, quality assurance field tests can use the easier and more widely known compressive strength test, which can be converted back to flexural strength through the previously determined correlations.

Most pavement PCC has a compressive strength between 20.68 and 34.47 MPa (3000 and 5000 psi) (ACPA, 2001). High-strength PCC (usually defined as PCC with a compressive strength of at least 41.37 MPa (6000 psi)) has been designed for compressive strengths of over 137.90 MPa (20,000 psi) for use in building applications.

## Test Procedures

The standard compression tests are:

• AASHTO T 22 and ASTM C 39: Compressive Strength of Cylindrical Concrete Specimens
• AASHTO T 140 and ASTM C 116: Compressive Strength of Concrete Using Portions of Beams Broken in Flexure