Residual mechanical properties of steel fiber reinforced concrete damaged by alkali silica reaction and subsequent sodium chloride exposure

Abstract

Infrastructures treated with de-icing salts and those which are in direct contact with sea water are subjected to degradation by chloride ingress. Concrete composed of reactive sources of silica and used near such regions can suffer from both, alkali silica reaction (ASR) and chloride ingress subsequently. This research aims at empirically investigating the residual mechanical properties of plain and steel fiber reinforced concrete damaged by alkali silica reaction (ASR) and subsequent chloride ion ingress. Accelerated degradation tests on three concrete mixes such as plain concrete (PC,control), steel fiber reinforced concrete (SFRC) and high strength fiber reinforced concrete (HSFRC) were done. Specimens were initially damaged by ASR, and then submerged in chloride solution at temperature ranges of 5 o C, 25 o C and 40 o C. 1 mol/L NaOH solution and 3% NaCl solution were used for a period of 20 and 40 weeks. Steel fibers were found to be effective in reducing surface crack widths at 5 o C and 25 o C. Accelerated mortar bar test showed that steel fibers were able to reduce expansion by 31.5% and 65.3% using single and double hooked fibers. By examining the residual compressive and flexure strengths, it was found that exposure to chloride environment aided in hydration reaction which counter-balanced the damage due to ASR. Fiber-matrix bonding developed over time inducing friction which led to higher ductility and less damage in flexure strength in steel fiber reinforced concrete prisms.