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Webinar Description:
“Air Entrainment” has been our industry’s
standard approach to providing concrete that can resist damage due to
freezing and thawing and deicer salt scaling. The ready mixed concrete
producer whips up about 10 billion microscopically-sized air bubbles into
every cubic yard of concrete. The trick is to get bubbles that are about the
right size and right total volume, and to stabilize those bubbles so they do
not break, or expand, or escape the concrete.
This Webinar focuses on why air entrainment
works, how air entraining admixtures perform their function, and a number of
mix- and concrete-production-related factors that affect the resulting air
content. The topic will explore how mixing, transport, placing,
consolidating, and finishing concrete affect the air bubbles in fresh
concrete and durability of hardened concrete. Requirements and intent of
industry standards will be discussed. This will cover testing air content in
fresh and hardened concrete, including the fundamental uncertainty in
reported values. Key to the discussion is the fundamental question of
testing location: point of discharge, point of placement, or both?
Program Elements Include:
How water, ice, and deicing salts
damage concrete and why introducing air bubbles in fresh bubbles reduces
the risk of such damage.
How air bubbles are formed and why
bubble size matters.
Factors that impact the development of
a proper air void system during production
Factors that increase or decrease air
content between batching and finishing.
How construction operations affect
entrained air and the impact to durability of hardened concrete.
Requirements in industry standards for
air content in fresh and hardened concrete and interpretation of the
results of standard tests.
Introduction to interpreting the results of tests of air in hardened
concrete.
Presenter Bio:
Kenneth
C. Hover is a Professor of Civil & Environmental Engineering and Stephen
Weiss Presidential Fellow at Cornell University in Ithaca, New York. An ACI
Member since 1980, Ken is Past President of the Greater Miami Valley Chapter
of ACI, and a member of ACI Committees 305 (hot weather), 306 (cold
weather), 308 (curing), 318A (concrete and construction) and chair of 301C
(materials and construction). Ken is currently Vice President of the
American Concrete Institute, and will become President in March, 2011.
He served as a Captain in the Army Corps of Engineers (15th Combat Engineer
Battalion), and was Project Engineer and Project Manager for Dugan and
Meyers Construction Co. in Cincinnati, working on buildings, interstate
bridges, and water treatment plants. Joining the structural consulting firm
of THP Ltd in Cincinnati, he became a partner and manager with experience in
project design, specifications writing, design team management, and contract
administration. He holds Bachelors and Masters Degrees in Civil Engineering
from the University of Cincinnati, and earned the Ph.D. in Structural
Engineering from Cornell University.
Ken came to Cornell with the assistance of a grant from the Exxon
Foundation, designed to bring experienced engineers to the faculties of US
Colleges of Engineering, and was among the first winners of an ACI
Scholarship. He joined the faculty in 1984 where he teaches reinforced and
prestressed concrete design, concrete materials, and construction
management. His research focuses on the impact of construction operations
and the construction environment on concrete quality.
Ken is a registered professional engineer in Ohio and New York, and lectures
nationally and internationally on concrete materials and construction. He
holds the Outstanding Educator Award from the American Concrete Pavement
Association, and from ACI he has earned the Kelly Educator’s Award, Philleo
Research Award, Structural Research Award, and Arthur Anderson Award. He
also received the ASCE Materials Division’s Best Basic Research Paper Award.
The Weiss Presidential Fellowship is Cornell University’s highest teaching
award, and in January 2006 at World of Concrete he was named one of the “Ten
Most Influential People in the Concrete Industry.”
