Title: Effects of Withholding Mixing Water and Retempering on Properties of Concrete

Author(s): Scott M. Anderson and Ramon L. Carrasquillo

Publication: Materials Journal

Volume: 92

Issue: 5

Appears on pages(s): 497-506

Keywords: abrasion resistance; air content; compressive strength; concretes; durability; flexural strength; freeze-thaw durability; retempering; slump tests; water-cement ratio; workability; Materials Research

DOI: 10.14359/888

Date: 9/1/1993

Abstract:
The effect of withholding mixing water at initial batching, followed by retempering of the mix at the job site on the properties of concrete, was examined in an experimental program. The effect of redosage with water, in addition to the amount called for in the specified mix design, was also examined. Tests were performed to determine the effects of the amount of water withheld, the age of concrete when retempered, and the cement content on the slump, air content, unit weight, compressive strength, flexural strength, abrasion resistance, and freeze/thaw resistance of concrete. The results of the study show that significant detrimental effects occur when mixing water is withheld and concrete is retempered at a later time. Slump, air content, abrasion resistance, and freeze/thaw resistance are adversely affected. The effects were found to be dependent on variations in both withholding time and cement content. Strength was not affected when water was withheld and the concrete was retempered using the withheld water, but a reduction in strength did accompany an increase in water-cement ratio above design values, resulting in reduced quality and questionable performance.