Title:
Evaluation of a Modified ASTM C157 for Early-Age Volume Change in Concrete
Author(s):
Matthew O'Reilly
Publication:
Web Session
Volume:
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
10/25/2020
Abstract:
A potential shortcoming of ASTM C157, Standard Test Method for Length Change of Hardened Hydraulic-Cement Mortar and Concrete, is the inability to observe behavior between the time of final set of concrete and the first 24 hours after casting. A modified version of ASTM C157, where length-change measurements begin approximately 5 to 5½ hours after casting was developed by University of Kansas Researchers to evaluate the effects of expansive admixtures on free shrinkage, where much of the early-age expansion would otherwise be missed. Results show that combinations of supplementary cementitious materials, internal curing via pre-wetted lightweight aggregates, shrinkage-reducing admixtures, and/or shrinkage-compensating admixtures in concrete produce significantly more swelling within the first 24 hours after casting than ordinary portland cement mixtures, a majority of which is not observed when using the standard test method. Furthermore, the test results for mixtures tested in accordance with both procedures show that the amount of drying shrinkage (length change from the end of curing through one year of drying) is virtually unaffected by the difference in test procedures. Apart from the reduction in shrinkage provided by the technologies listed above, the additional swelling further mitigates the potential for cracking in concrete.