Results 301 to 310 of about 147,317 (357)

Air void morphology in fresh cement pastes

Cement and Concrete Research, 2002
Abstract Two different procedures are used in conjunction with low-temperature scanning electron microscopy to image the air voids in cement pastes at very early ages. The first procedure isolates the air voids from cement paste after less than 30 min of hydration, and allows them to be imaged apart from the paste.
D.J Corr, J Lebourgeois, P.J.M Monteiro, S.J Bastacky, E.M Gartner   +4 more
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Polyurethane foam growth in Air Void Analyzer

Materials Research Innovations, 2016
The authors have used an Air Void Analyzer (AVA) designed for concretes and applied it to polymeric foams. Similarly as with air voids in concretes, there is a kinetic process of foam cell formation and growth. Good results have been obtained for polyurethane foams. There seems to be no limitation in using AVA for other polymeric foams formation.
W. Brostow, G. Granowski, N. Hnatchuk
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Air Voids at Downshaft‐tunnel Bends

Journal of Hydraulic Engineering, 1983
In closed conduit water flows containing a small amount of free air, an air void can form at a bend which connects a vertical shaft to a horizontal tunnel. A sudden reduction in the water flow rate can cause this void to vent back up the shaft. Tests were conducted on eight perspex pipe bends whose center‐line radius varied from 0.5 times–1.5 times the
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Air-Void Stability, Part IV: Retempering

ACI Materials Journal, 1990
Eight laboratory mixes and eight field mixes were prepared to study the influence of retempering by adding water to the characteristics of the air-void system, and to study air entrainment when an air-entraining admixture is added significantly after the initial mixing period.
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Air-void parameters measurement of fresh concrete

Journal of Wuhan University of Technology-Mater. Sci. Ed., 2013
To explore the method to evaluate air-void parameters of fresh concrete rapidly, the spacing factor and specific surface of freshly mixed concrete of different air contents, different slumps and different mineral admixtures (fly ash, fly ash-slag, fly ash-slag-silica fume composite) are studied by air-void analyzer (AVA), and the correlation between ...
Huajian Li, Lu Yang, Yongjiang Xie
openaire   +1 more source

Soil Air Voids Method for Compaction Control

2005
This research project was structured to evaluate the air voids method as a means of assessing the quality of a compacted layer of soil. A literature review was conducted to examine existing published information on the air voids method and to explore how extensively Tech Reports have used the method.
Mokwa, Robert L, Fridleifsson, Stefan, Montana State University: Department of Civil Engineering   +2 more
openaire   +1 more source

Earthwork compaction evaluation using soil air voids

Canadian Geotechnical Journal, 2007
The soil air voids method represents an alternate approach to the traditional Proctor method of field compaction control. The air voids evaluation procedure is based on the premise that the future performance of a compacted layer of soil can be evaluated by comparing the measured air voids with a predetermined limiting value.
Robert L Mokwa, Stefan Fridleifsson
openaire   +1 more source

Microstructure of entrained air voids in concrete, Part II

Journal of Materials Research, 1991
The microstructure of air voids in both air-entrained and non air-entrained paste, mortar, and concrete containing silica fume has been studied at different ages (5 min to 60 days) in order to understand how air-entrained voids form in portland cement–silica fume systems. Scanning electron micrographs of air voids are presented for many different ages.
Ahmed I. Rashed, Robert Brady Williamson
openaire   +1 more source

Development of Precision Statement for Determining Air Void Characteristics of Fresh Concrete with Use of Air Void Analyzer

Transportation Research Record: Journal of the Transportation Research Board, 2007
The presence of an adequate air void system is widely regarded as one of the key elements to producing durable, long-lasting concrete. Until recently, the air void system was monitored in the fresh state by a measure of the total air, and an indication of the air void characteristics, namely, the spacing factor and specific surface, was not possible ...
Jennifer A. Distlehorst, Geoffrey J. Kurgan   +1 more
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Super Air Meter for Assessing Air-Void System of Fresh Concrete

Advances in Civil Engineering Materials, 2016
Abstract A key factor for freeze-thaw durability of concrete is the air void system; nevertheless, the current test methods for fresh concrete only allow for determination of total air content. There is a need for a fresh concrete test method capable of indicating that air void size and distribution are adequate. In an attempt to address
J. Tanesi, H. Kim, M. Beyene, A. Ardani
openaire   +1 more source