title: Investigation of damaged interior walls using synchrotron-based XPS and XANES.
abstract: Evidence of internal sulfate attack in field exposure was demonstrated by the damaged interior wall of a three-year-old house situated in Nakhon Ratchasima Province, Thailand. Partial distension of the mortar was clearly observed together with an expansion of a black substance. Removal of the black substance revealed a dense black layer. This layer was only found in the vicinity of the damaged area, suggesting that this black material is possibly involved in the wall cracking. By employing synchrotron-based X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) techniques, the unknown sample was chemically identified. The S 2p and O 1s XPS results mutually indicated the existence of sulfate species in the materials collected from the damaged area. The XANES results indicated the presence of ferrous (II) sulfate, confirming sulfate-induced expansion and cracking. The sulfate attack in the present case appeared to physically affect the structure whereas the chemical integrity at the molecular level of the calcium silicate hydrate phase was retained since there was a lack of spectroscopic evidence for calcium sulfate. It was speculated that internal sulfate probably originated from the contaminated aggregates used during the construction. The current findings would be beneficial for understanding the sulfate-attack mechanism as well as for future prevention against sulfate attack during construction.
authors.affiliation: Synchrotron Light Research Institute, 111 University Avenue, Nakhon Ratchasima 30000, Thailand.
authors.forename: Yingyot
authors.initials: Y
authors.lastname: Poo-arporn
authors.affiliation: Department of Chemistry, Faculty of Science, Kasetsart University, 50 Phahonyothin Road, Bangkok 10903, Thailand.
authors.forename: Surachai
authors.initials: S
authors.lastname: Thachepan
authors.affiliation: Biological Engineering Program, Faculty of Engineering, King Mongkut's University of Technology Thonburi, 126 Pracha Uthit Road, Bangkok 10140, Thailand.
authors.forename: Rungtiva
authors.initials: R
authors.lastname: Palangsuntikul
keywords: XANES; XPS; cement; cement mortar; internal sulfate attack