Performance of amine cured epoxy and silica fume modified cement mortar under military airbase operating conditions

Abstract

Conventional concrete at military airbase is reported to experience premature scaling damage due to repeated exposures to hydrocarbon fluids (HFs), rainwater and high thermal shocks simultaneously. The present study examines the performance of amine cured epoxy and reactive silica fume (SF) modified Portland cement (PC) mortar and unmodified PC mortar under laboratory simulated military airbase operating conditions, which simultaneously applied HFs, water and high temperature on the surfaces of the considered mortar specimens repeatedly. Unmodified PC mortar was observed to experience saponification, thermal cracks and scaling when exposed to the combined actions of HFs and thermal cycles; however, the modified PC mortar sustained those adverse conditions. After 80 cycles of exposure to the simultaneous actions of HFs and high temperature, the unmodified plain mortar lost 80.48% of the compressive strength. Whereas, the 3-day and 28-day old epoxy and SF modified PC mortar lost 41.70% and 36.15% of the compressive strength showing considerable resilience against the military airbase working conditions, respectively. Epoxy and SF modified PC mortar retained more than the required minimum compressive strength for military airbase even after 80 cycles of exposure, however, the unmodified PC mortar failed to do so. FTIR and XRD analyses, showed that compounds created by interactions amongst epoxy, SF and PC did not react with HFs even at high temperature. Epoxy notably protected crystalline mineral compounds such as ettringite, portlandite, quartz, alite, belite mullite and calcite in PC from hydrocarbon attacks but failed to prevent their thermal decomposition, as epoxy in mortar was observed to deform, swell and plasticized after thermal exposures. Mass loss characteristics, depths of HFs attack, effect of epoxy to cement (E/C) ratio on the durability, residual compressive strength and microstructures after the considered exposures are also reported.