Email Address is required Invalid Email Address
In today’s market, it is imperative to be knowledgeable and have an edge over the competition. ACI members have it…they are engaged, informed, and stay up to date by taking advantage of benefits that ACI membership provides them.
Read more about membership
Learn More
Become an ACI Member
Founded in 1904 and headquartered in Farmington Hills, Michigan, USA, the American Concrete Institute is a leading authority and resource worldwide for the development, dissemination, and adoption of its consensus-based standards, technical resources, educational programs, and proven expertise for individuals and organizations involved in concrete design, construction, and materials, who share a commitment to pursuing the best use of concrete.
Staff Directory
ACI World Headquarters 38800 Country Club Dr. Farmington Hills, MI 48331-3439 USA Phone: 1.248.848.3800 Fax: 1.248.848.3701
ACI Middle East Regional Office Second Floor, Office #207 The Offices 2 Building, One Central Dubai World Trade Center Complex Dubai, UAE Phone: +971.4.516.3208 & 3209
ACI Resource Center Southern California Midwest Mid Atlantic
Feedback via Email Phone: 1.248.848.3800
Home > Tools > Frequently Asked Questions
Q. How can the surface or free water carried by the aggregates be determined? A. Free water is simply the difference between the mass of a sample of wet-saturated aggregate and the mass of the same sample in the saturated-surface-dry condition. Standard test methods for surface moisture in fine aggregate are available (ASTM C70). If the absorption capacity of the aggregate is known, a more common method for determining surface moisture is by drying the aggregate (ASTM C566). Water within the aggregate particles does not affect the mixture or the w/cm. Allowance should be made for water that will be absorbed by dry aggregate, however, and may be as much as 95% of its total absorption capacity during the mixing period. Many concrete plants have calibrated moisture meters (based on electrical resistance or microwave technology) that continuously monitor free moisture on the aggregates and have the capability to automatically adjust the added water to maintain the mixing water content within the specified limits. References: SP-1(02); E-1(16); ACI 221R-96; ASTM C70; ASTM C566 Topics in Concrete: Aggregate; Concrete Fundamentals; Testing of Concrete
Q. How can the surface or free water carried by the aggregates be determined?
A. Free water is simply the difference between the mass of a sample of wet-saturated aggregate and the mass of the same sample in the saturated-surface-dry condition. Standard test methods for surface moisture in fine aggregate are available (ASTM C70). If the absorption capacity of the aggregate is known, a more common method for determining surface moisture is by drying the aggregate (ASTM C566). Water within the aggregate particles does not affect the mixture or the w/cm. Allowance should be made for water that will be absorbed by dry aggregate, however, and may be as much as 95% of its total absorption capacity during the mixing period. Many concrete plants have calibrated moisture meters (based on electrical resistance or microwave technology) that continuously monitor free moisture on the aggregates and have the capability to automatically adjust the added water to maintain the mixing water content within the specified limits.
References: SP-1(02); E-1(16); ACI 221R-96; ASTM C70; ASTM C566
Topics in Concrete: Aggregate; Concrete Fundamentals; Testing of Concrete
Search other resources on the ACI website for answers to technical questions