Large scale concrete structures has brought about a re-examination of the durability characteristics of structural lightweight aggregate concrete. Extensive laboratory freeze-thaw testing programs have demonstrated that structural lightweight aggregates, in combination with high quality pastes containing the proper spacing and amounts of air, and permitted a drying period of at least 14 days prior to first freezing, will produce excellent laboratory tested concrete durability. Investigations of a number of in-service lightweight concrete structures in marine environments for up to 60 years verify the laboratory indications of good weathering resistance and suggest the following criteria for future applications:
- Use high quality structural lightweight aggregate (both coarse and fine) that has a proven record of durable performance in severe weathering exposure.
- Use a minimum cement content of 611 pcy for structures with moderate exposure (building facades, garages) and 748 pcy for concretes with severe exposure (bridge decks, marine environments).
- Use air contents suggested by ACI 201 as a minimum starting point, 6% for 3/4", 7.5% for 3/8" aggregate.
- Place concretes at reasonable slumps (3"), using best recommended practice for compaction, finishing and curing.
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