Fly Ash and Slag Jet-Blast Resistant Concretes


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Title: Fly Ash and Slag Jet-Blast Resistant Concretes

Author(s): P. J. Robins and S. A. Austin

Publication: Special Publication

Volume: 153


Appears on pages(s): 1141-1164

Keywords: airports; fly ash; jet blasts; lightweight aggregates; pavements; slags; spalling; temperature; Materials Research

Date: 6/1/1995

Conventional limestone concrete airfield pavements are prone to spalling as a result of jet blast from vertical take-off and landing aircraft. This paper describes a research program to develop jet blast resistant pavement quality controls containing alternative cementitious materials and aggregates. The concretes were evaluated by subjecting slabs to simulated Harrier jet engine blast, using thermal imaging and video cameras to record surface temperatures, spall times, and spalled areas. Slag and fly ash as partial cement replacement materials produced moderate increases in the surface temperature and exposure time at which spalling initiated. Fly ash aggregates produced substantial improvements in spalling resistance under simulated Harrier conditions, particularly when used to replace both the fine and coarse natural aggregates. The spalling mechanism was associated with differential thermal expansion, as opposed to the release of water vapor and the dehydration of cementitious compounds. Spalling observed during field exposure was attributed to laitance and brushing of the surface, which also suffered from drying shrinkage cracking.