Eur. Phys. J. E (2012) 35: 45
https://doi.org/10.1140/epje/i2012-12045-6

Regular Article

Tackiness and cohesive failure of granular pastes: Mechanistic aspects

¹ College of Sciences and Arts, Al Jouf University, P.O. Box 756, Al-Qurayat, Saudi Arabia
² Laboratoire de Mécanique et Technologie, Ecole Normale Supérieure de Cachan/CNRS-UMR 8535, 61 Avenue du Président Wilson, F-94235, Cachan Cedex, France
³ Lafarge Centre de Recherche, rue du Montmurier, 38291, Saint Quentin Fallavier, France
⁴ LPMCN, UMR 5586, Université Claude Bernard, Lyon I, 43 Boulevard du 11 novembre 1918, 69622, Villeurbanne Cedex, France
⁵ DAMTP, University of Cambridge, Wilberforce Road, CB3 0WA, Cambridge, UK
⁶ ESPCI-ParisTech, 10 rue Vauquelin, 75231, Paris cedex 05, France
⁷ Université Paris Est, IFSTTAR, 58 boulevard Lefebre, 75732, Paris Cedex 15, France

^* e-mail: my.abdelhaye@ju.edu.sa
^** e-mail: henri.van-damme@ifsttar.fr

Received: 3 October 2011
Accepted: 18 May 2012
Published online: 14 June 2012

Abstract

Granular pastes are dense dispersions of non-colloidal grains in a simple or a complex fluid. Typical examples are the coating, gluing or sealing mortars used in building applications. We study the rupture of a thick layer of mortar paste in a simple pulling test where the paste is confined between two flat surfaces. It is shown that, depending on the rheological properties of the paste and the plate separation velocity, two main failure modes are obtained. The first mode is the inwards shear flow of the paste with viscous fingering instabilities, similarly to what has been observed with Newtonian fluids and with non-Newtonian colloidal suspensions or polymer solutions. The second failure mode is stemming from the expansion of bubbles, similarly to what has been observed in soft adhesive polymer layers and, more recently, in highly viscous fluids. It is shown that the crossover between the two failure modes is determined by the conditions required to generate a pressure drop able to trigger the growth of pre-existing micro-bubbles smaller than the inter-granular distance.