Reinforced Lightweight Concrete Columns

Forty columns were tested to compare lightweight and normal weight concrete with respect to instantaneous response to load, time-dependent shortening characteristics under sustained load, and ultimate strength and strain. Two compressive strength levels of concrete were used with intermediate grade steel and high strength steel was also included with the higher strength concrete. The percentage of reinforcement was varied from 0 to the 8 percent maximum allowed by the ACI. Both instantaneous and time-dependent shortenings were more directly related to steel percentage than to concrete type. The reinforced lightweight columns had greater initial shortenings, but generally less time-dependent shortenings than did the comparable normal weight columns. Long-time drying shrinkage effects on the non-loaded columns were similar for the two types of concrete. Ultimate strengths were little different for the two types of concrete and the lightweight concrete columns had somewhat greater strain capacity during tests to destruction.