Mechanical Properties of Structural Lightweight Aggregate Concrete Containing Low Volume Steel Fiber

The use of steel fibers is a good solution for compensating lower mechanical properties of lightweight concrete. However, due to the high specific gravity, the addition of steel fiber increases the density of lightweight concrete. Therefore, there is some reluctance regarding the use of this fiber in lightweight concrete. In this study, to prevent a significant increase in density, low volume fractions of steel fiber ( ≤ 1 %) were used to produce grade 20 structural lightweight aggregate concrete with a dry density of 1,650 kg/m 3 . Effect of low volume steel fiber on the compressive strength in different curing environments, splitting tensile strength and flexural strength was studied. The test results show that the addition of steel fiber in volume fractions of 0, 0.25, 0.5, 0.75 and 1 % increased its 28-day compressive strength between 14 and 32 %, splitting tensile strength between 21 and 77 % and flexural strength between 6 and 69 %. The effectiveness of steel fiber to increase the compressive strength was more pronounced at later ages than at early age. It was observed that 3 days moist curing is sufficient to gain equivalent compressive strength under standard curing. Adding even a small amount of steel fiber (i.e. 1 % volume fraction) increased the density; however, it was still within the ACI structural lightweight concrete specification. The flexural crack patternsin steel fiber-reinforced concrete beams showed excellent performance of low volume steel fibers in arresting the propagation of cracks.