Thermal performance of steel fibrous lightweight aggregate concrete short columns

Abstract

The thermal performance of fibrous lightweight aggregate concrete short columns was investigated in terms of compressive mechanical response and thermal and load cracking patterns and characteristics. Seventy-two scaled column specimens (120 × 120 × 400 mm) having varying lateral steel confinements were cast without and with hooked steel fiber reinforcement, before cured for 28 days and exposed to high temperatures (from 300 to 700℃) in an electric oven followed by slow cooling in laboratory air. The results indicated a marked reduction in their compressive load capacity and rigidity, and an increase in their strain at peak stress and compressive toughness as exposure temperatures exceeded 400℃. An enhancement in mechanical properties under high temperatures was noticed at moderate confinement levels. The benefit of using hooked-steel fibers in preserving post-heating mechanical properties of short columns was more pronounced in unconfined rather than in confined lightweight aggregate concrete specimens. Thermal cracking was proportional to exposure temperature with its extent reduced upon use of steel fibers or steel confinement. Failure modes of column specimens varied from brittle to semi-ductile fracture with longitudinal steel buckling noticed for those treated at 700℃.