Soutenance de Justine Henry

The jury will be composed of:

- Emanuela Del Gado, Professor, I(SM)² - Georgetown University, Reviewer 

- Dimitris Vlassopoulos, Professor, FORTH - University of Crete, Reviewer

- Elodie Bourgeat-Lami, CNRS Research Director, CP2M - CPE Lyon and University Lyon 1, Examiner 

- Michael Haist, Professor, Materials Testing Institute - Stuttgart University, Examiner 

- Clara Paillard, Industrial Supervisor, Saint-Gobain Research Paris, Examiner 

- Nicolas Sanson, Associate Professor, SIMM - ESPCI, Examiner

- Thibaut Divoux, CNRS Research Director, Physics Laboratory - ENS Lyon, PhD supervisor 
 

Abstract:

Cementitious tile adhesives (CTA) are commonly modified with small amounts of polymer additives to enhance their flexibility and adhesion performance. Among these additives, redispersible polymer powders (RDP) – composed of stabilized polymer colloids – often referred to as "latex" particles, play a central role: once incorporated to cement paste, they can coalesce and gradually form films around cement grains and hydration products. However, the coupling between cement hydration and latex film formation mechanisms, and how this interplay controls the mechanical properties of CTA remains insufficiently understood. This thesis aims to clarify how latex particles organize within the cement matrix, how their viscoelastic properties evolve during film formation, and how they impact the mechanical properties of polymer-modified cement (PMC) pastes, especially at low RDP contents where no continuous polymer film can form.

The first part examines the evolution of viscoelastic properties in dense latex suspensions of commercial RDP during film formation using time-resolved mechanical spectroscopy. This technique reveals a robust time-aging superposition principle across temperatures, RDP chemistries, and ionic content, and highlights the key role of stabilizing agents. As polymer films age, a ductile-to-brittle transition at yielding is also observed. The second part investigates how chlorine-marked latex particles are distributed within hardened PMC. We show that a low RDP contents, latex particles do not form a continuous network, but instead assemble into local latex clusters. The final part characterizes the micro-mechanical properties of PMC pastes with varying RDP nature, content, and curing conditions using micro-scratch and grid micro-indentation. We show that higher latex contents lead to a lower creep modulus, meaning that latex particles allow the cementitious matrix to undergo more time-dependent deformation. This enhanced creep capacity helps the material accommodate stresses rather than abruptly failing in a brittle fashion.