Bonding in cementitious materials with asphalt-coated particles: Part I – The interfacial transition zone. (15th January 2017)

• Record Type: Journal Article
• Authors: Brand, Alexander S.; Roesler, Jeffery R.
• Is Part Of: Construction & building materials. Volume 130(2017)
• Page Start: 171
• Page End: 181
• Publication Date: 2017-01-15
• Subjects: Reclaimed asphalt pavement -- Concrete -- Interfacial transition zone -- Backscattered electron microscopy -- Image analysis -- Calcium hydroxide; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2016.10.019
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Backscattered electron microscopy used to study ITZ of mortar with RAP aggregates. Larger, more porous ITZ forms from RAP aggregates compared to dolomite. Less CH and C-S-H are present in ITZ near the RAP interface. Silica fume does not significantly improve ITZ properties in mortar with RAP. Abstract: Reclaimed asphalt pavement (RAP), when used as a coarse aggregate, has been shown to reduce bulk concrete strength and modulus. Part I of this study quantifies and compares the interfacial transition zone (ITZ) for mortar with RAP aggregates relative to dolomite aggregates through image analysis of backscattered electron micrographs. The ITZ with RAP aggregates was larger and more porous with less calcium silicate hydrate (C-S-H) and calcium hydroxide (CH) at the asphalt interface compared with dolomite aggregates. The CH morphology was not significantly affected, although the presence of the asphalt layer may be affecting the CH growth. The addition of silica fume reduced the porosity and size of CH particles in the ITZ with RAP, but not sufficiently to be similar to the ITZ of the dolomite mortar. The microstructural changes caused by RAP aggregates, primarily the larger, more porous ITZ, provide strong evidence for the observed reduction in concrete strength and modulus.