Porosity generation arising from steel fibre in concrete

Abstract

The present study concerns a measurement of porosity at the steel fibre interface in mortar. Mortar cast with a centrally located steel fibre (00.39 x 15.0 mm) was segmented for microscopic observation at a backscattered electron (BSE) image. In the BSE image, the interfacial zone was defined as long as 270 mu m from the surface of steel fibre, where the porosity was measured by counting pixels after binarising the image for porosity. As a result, it was found that the pores generated in the vicinity of the steel fibre ranged from 5.40% to 11.45%, equivalent to 0.51-1.08% of air void in a bulk concrete. The high porosity at the interface may impose a reduction of concrete strength (i.e. up to a debondment with cement paste) and a potential risk of further supply of aggressive ions through the pores, leading to a lower durability against chemically severe environments. (C) 2015 Elsevier Ltd. All rights reserved.