Reactive transport modeling and characterization of concrete materials with fly ash replacement under carbonation attack - 15477

Conference · Wed Jul 01 00:00:00 EDT 2015

OSTI ID:22824373

Branch, J. L.; Brown, K. G.; Arnold, J. R. ^[1]; Van der Sloot, H. A. ^[2]; Kosson, D. S. ^[1]

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1. Vanderbilt University, Dept. of Civil and Environmental Engineering, Nashville, TN (United States)
2. Hans van der Sloot Consultancy, Langedijk (Netherlands)

There currently lacks sufficient knowledge to accurately characterize structural, hydraulic, and chemical performance of cementitious materials that are required to contain and shield nuclear waste for thousands of years. There are a number of degradation methods that can affect the integrity of these materials over this time frame including carbonation which lowers the alkalinity of the material and can induce cracking in materials with steel reinforcement. The rate and extent of carbonation in these materials is impacted by the addition of fly ash and its composition which can vary depending on the fly ash source. To characterize the carbonation reaction, the changes in the microstructure and elemental distribution as a function of extent of carbonation and fly ash type were evaluated using scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDS). Micro-concretes were prepared with no fly ash (control case) and with fly ash of various calcium compositions. The progression of the carbonation front was observed in the backscattered electron images by the formation of calcium carbonate and depth was confirmed with a phenolphthalein pH indicator test. The migration and deposition of chemical species were observed in carbonated regions from EDS data and were explained based on the changes in material alkalinity and solubility determined from EPA Method 1313 (Liquid-solid partitioning (LSP) as a function of eluate pH). The changes in mass transport properties from carbonation were observed using EPA Method 1315 (Mass transfer rates in monolithic and compacted granular materials using semi-dynamic tank leaching procedures). The carbonation reaction in each material was simulated using LeachXS/ORCHESTRA, a reactive transport modeling tool, which provided further evidence of localized deposition and migration of chemical species due to changes in speciation and solubility. (authors)

• Research Organization: WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
• OSTI ID: 22824373
• Report Number(s): INIS-US-19-WM-15477; TRN: US19V0945069419
• Resource Relation: Conference: WM2015: Annual Waste Management Symposium, Phoenix, AZ (United States), 15-19 Mar 2015; Other Information: Country of input: France; 11 refs.; available online at: http://archive.wmsym.org/2015/index.html
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
ACID NEUTRALIZING CAPACITY
CALCIUM CARBONATES
CARBONIZATION
CONCRETES
CRACKS
DEPOSITION
FLY ASH
GRANULAR MATERIALS
HYDRAULICS
LEACHING
MASS TRANSFER
MICROSTRUCTURE
PH VALUE
PHENOLPHTHALEIN
RADIOACTIVE WASTES
SCANNING ELECTRON MICROSCOPY
SHIELDING MATERIALS
STEELS
TANKS
US EPA
X-RAY SPECTROSCOPY