ASTM C1579 – Standard Test Method for Evaluating Plastic Shrinkage Cracking of Restrained Fiber Reinforced Concrete (Using a Steel Form Insert)
Description:
Significance and Use
5.1 The test method is intended to evaluate the effects of evaporation, settlement, and early autogenous shrinkage on the plastic shrinkage cracking performance of fiber reinforced concrete up to and for some hours beyond the time of final setting (see Terminology C125).
5.2 The measured values obtained from this test may be used to compare the performance of concretes with different mixture proportions, concretes with and without fibers, concretes containing various amounts of different types of fibers, and concretes containing various amounts and types of admixtures. For meaningful comparisons, the evaporative conditions during test shall be sufficient to produce an average crack width of at least 0.5 mm in the control specimens (2, 3) (see Note 2). In addition, the evaporation rate from a free surface of water shall be within ± 5 % for each test.
NOTE 2: To achieve evaporation rates that result in a crack of at least 0.5 mm in the control specimens, it may be necessary to use an evaporation rate higher than that discussed in Note 1.
5.3 This method attempts to control atmospheric variables to quantify the relative performance of a given fresh concrete mixture. Since many other variables such as cement fineness, aggregate gradation, aggregate volume, mixing procedures, slump, air content, concrete temperature and surface finish can also influence potential cracking, attention shall be paid to keep these as consistent as possible from mixture to mixture.
Scope
1.1 This test method compares the surface cracking of fiber reinforced concrete panels with the surface cracking of control concrete panels subjected to prescribed conditions of restraint and moisture loss that are severe enough to produce cracking before final setting of the concrete.
1.2 This test method can be used to compare the plastic shrinkage cracking behavior of different concrete mixtures containing fiber reinforcement.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
ASTM C157