The control of cracking is a problem that concerns those who design and build with concrete. But there hasn't been any standard test that evaluates quantitatively what the effect is on drying shrinkage cracking in the field when one material or condition is changed. Now a test is being developed that has been introduced for consideration by the American Society for Testing and Materials. The test sets up adverse conditions that incorporate the major causes of cracking. The first numerical results of the test can become available within a matter of hours and complete results are normally available within 24 hours.
Unfortunately, many people equate the cracking potential of concrete with its drying shrinkage characteristics. Drying shrinkage is usually measured according to ASTM C 157, "Standard Test Method for Length Change of Hardened Cement Mortar and Concrete." Using this test to control drying shrinkage cracking, however, has had questionable success and may mislead those who try to use it for this purpose. The test described here, however, is not a measure of drying shrinkage, but rather of cracking potential.