Quantcast Chapter 13. HEAT-RESISTANT CONCRETE

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UFC 3-270-04
15 March 2001
CHAPTER 13
HEAT-RESISTANT CONCRETE
13.1. Description. Concrete pavement exposed to high temperatures from aircraft jet blast or
from auxiliary power units can suffer damage. If the concrete is wet when the heat is suddenly
applied, the production of steam within the concrete can cause spalling. If the concrete is dry or
the heat is applied slowly, relatively little permanent damage is done with concrete temperatures
up to 400 to 500 degrees Fahrenheit (204 to 260 degrees Celsius). At concrete temperatures above
this, water of hydration is lost, and the concrete strength decreases. At about 1,000 degrees
Fahrenheit (538 degrees Celsius), compressive strength loss can be 55 to 80 percent of the
original strength. At the time of heating, the degree of saturation of the concrete influences the
severity of strength loss, and repetitions of heating and cooling cycles further degrade the
concrete. At a temperature of around 1,060 degrees Fahrenheit (571 degrees Celsius), silica in
the concrete aggregates undergoes a crystal change and expands, and in the range of 1,300 to
1,800 degrees Fahrenheit (704 to 982 degrees Celsius), carbonate aggregates undergo a
chemical change. As the concrete surface is heated, a large temperature gradient develops
between the surface concrete and the cooler slab depths that can lead to separation and spalling.
The behavior of concrete exposed to high temperatures is complex. Typical concrete pavement
damage resulting from high temperatures of jet blast includes spalling, aggregate popouts,
scaling, cracking, and loss of joint sealant. The time that the concrete is exposed to the jet
engine or auxiliary power unit exhaust is critical, since there is considerable thermal lag in
concrete.
Properly designed pavements generally have not suffered heat damage from aircraft. Power
check pads where extensive engine operations occur for maintenance are specially detailed to
minimize the exhaust plume's contact with the pavement surface. Where existing pavements,
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