Norlite, LLC
628 S. Saratoga Street Cohoes, NY 12047
(518) 235-0030 (phone) (518) 235-0233 (fax)

Structural Concrete

Fire Resistance

When tested according to the procedures of ASTM E-119, structural lightweight concrete slabs, walls, and beams have demonstrated greater fire endurance periods than equal equivalent-thickness members made from ordinary aggregate. Superior performance is due to a combination of lower thermal conductivity (lower temperature rise on unexposed surfaces), lower coefficient of thermal expansion (lower forces developed under restraint), and the inherent thermal stability developed by aggregates that have already been exposed to temperatures greater than 2000° F during pyroprocessing.

Effect of slab thickness and aggregate type

Fire Resistence

The figure above, (from ACI 216, Guide for Determining the Fire Endurance of Concrete Elements) shows the relationship between slab thickness and fire endurance for structural concretes made with a wide range of aggregates. The curves are for air-entrained concretes fire tested when the concrete was at the standard moisture condition (75 percent relative humidity at mid-depth), made with air-dry aggregates having a nominal maximum size of 3/4 in. (19 mm). On the graph, lightweight aggregates include expanded clay, shale, slate, and fly ash that make concrete having a unit weight of about 95 to 105 pcf (1520 to 1680 kg/m3) without sand replacement. The unit weight of air cooled blast-furnace slag aggregate was found to have little effect on the resulting fire endurance of the normal weight concretes in which it is used.