title: Volcanic sintering: Timescales of viscous densification and strength recovery.
abstract: [1] Sintering and densification are ubiquitous processes influencing the emplacement of both effusive and explosive products of volcanic eruptions. Here we sinter ash-size fragments of a synthetic National Institute of Standards and Technology viscosity standard glass at temperatures at which the resultant melt has a viscosity of ∼108-109Pa.s at 1bar to assess sintering dynamics under near-surface volcanic conditions. We track the strength recovery via uniaxial compressive tests. We observe that volcanic ash sintering is dominantly time dependent, temperature dependent, and grain size dependent and may thus be interpreted to be controlled by melt viscosity and surface tension. Sintering evolves from particle agglutination to viscous pore collapse and is accompanied by a reduction in connected porosity and an increase in isolated pores. Sintering and densification result in a nonlinear increase in strength. Micromechanical modeling shows that the pore-emanated crack model explains the strength of porous lava as a function of pore fraction and size.
authors.affiliation: Department of Earth and Environmental Sciences, Ludwig Maximilians University Munich, Germany.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Vasseur
authors.affiliation: Department of Earth and Environmental Sciences, Ludwig Maximilians University Munich, Germany.
authors.forename: Fabian B
authors.initials: FB
authors.lastname: Wadsworth
authors.affiliation: Department of Earth, Ocean and Ecological Sciences, University of Liverpool Liverpool, UK.
authors.forename: Yan
authors.initials: Y
authors.lastname: Lavallée
authors.affiliation: Department of Earth and Environmental Sciences, Ludwig Maximilians University Munich, Germany.
authors.forename: Kai-Uwe
authors.initials: KU
authors.lastname: Hess
authors.affiliation: Department of Earth and Environmental Sciences, Ludwig Maximilians University Munich, Germany.
authors.forename: Donald B
authors.initials: DB
authors.lastname: Dingwell
keywords: brittle; pore-emanated crack model; porosity; tuffisite; ultrasonic velocity; volcanic ash
references.citation: Rev Sci Instrum. 2007 Jul;78(7):075102
references.pmid: 17672788