ABSTRACT
Compared to other ingredients, there are several sources (with potential errors) by which mixing water is incorporated in a concrete mixture. ASTM C94 and ACI 117 state that the total mixing water should be within ±3% of the quantity required by the mix design. This mixing water includes water added to the batch, ice added to the batch, water occurring as surface moisture on the aggregates, water introduced in the form of admixtures, and any washwater retained in the truck drum. In addition, mixing water may also be added at the slump rack and at the job site. The primary sources of mixing-water variations and methods by which they can be controlled to be within a tight tolerance are discussed next.
