Microstructural and permeability changes due to accelerated Ca leaching in ammonium nitrate solution

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Abstract

Although Ca leaching in cement-based materials is an extremely slow process, this process is relevant for long-term assessments of the evolution of concrete used in radioactive waste disposal systems. In the present work, an ammonium nitrate solution of 6 mol/l was used to accelerate the leaching kinetics of cement paste. The change of sample mass over time was monitored by weighing, whereas the amount of calcium ion leached out during the test was followed by ion chromatography. A variety of post-analysis techniques like XRD, MIP and BET were used to characterize the microstructural changes and portlandite content, while the degraded front was determined by phenolphthalein spraying. The effect of accelerated leaching on transport properties was studied by measuring changes in water permeability. Results showed that (i) the porosity of the leached samples increased significantly, (ii) the critical pore size was shifted to larger radius and (iii) the BET specific surface area of the leached sample was also significantly increased. These changes resulted in a one to two order increase in water permeability depending on the immersed time.

Details

Original languageEnglish
Title of host publicationConcrete Solutions
Place of PublicationUnited Kingdom
Pages431-438
Publication statusPublished - Sep 2014
EventConcrete Solutions 2014 - The Concrete Society, Belfast, United Kingdom
Duration: 1 Sep 20143 Sep 2014

Conference

ConferenceConcrete Solutions 2014
Country/TerritoryUnited Kingdom
CityBelfast
Period2014-09-012014-09-03

Keywords

  • Ca leaching, cement, concrete, radioactive waste disposal, porosity

ID: 363299