Impact of Addition of Fly Ash (as Sand Replacement) and Polypropylene Fibers on Energy Absorption Characteristics of Foam Concrete

Abstract

Foam concrete has recently piqued the interest of defense engineering because of its innovative properties of absorbing energy, softening impact, exhausting oscillation, and lowering stress amplitude behavior. However, only a few investigations on foam concrete’s mechanistic behavior and energy absorption properties have been published. This study examines the effects of adding fly ash (sand replacement) and polypropylene fibers to foam concrete with design densities of 1,000 and 1,500 kg/m3 on fresh state features (stability and consistency), mechanical properties, and energy absorption capacities. The consistency of foam concrete increases with the addition of foam and fly ash, but the inclusion of fibers has a significant impact. Though the addition of fibers reduced the compressive strength of foam concrete, the bonding of fibers with the matrix is strengthened in fly ash–based mixes, resulting in increased strength, showing the synergistic effect. An improvised low-velocity drop-weight impact test is carried out on foam concrete target slabs produced with various mix compositions to investigate the impact mitigation properties of foam concrete under impact loading. The energy absorption capacity of different mixtures of foam concrete specimens is found to vary between 0.3 and 1.18 J using the conservation of energy law and assuming no energy losses. Because of the availability of sufficient bubble space for crushed debris and the better impact resistance provided by the fibers, mixes with more air and fibers displayed relatively more energy absorption. To examine the mixes based on the local area effect of impact loading, observations on both energy absorption and failure mechanism are carried out.