Squeeze-flow and phase segregation in mortars: influence of paste viscosity and particle size distribution

• Grant number: 13/27121-2
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: April 01, 2014
• End date: September 30, 2014
• Field of knowledge: Engineering - Civil Engineering - Construction Industry
• Principal Investigator: Rafael Giuliano Pileggi
• Grantee: Fábio Alonso Cardoso
• Supervisor: Mohend Chaouche
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: École Normale Supérieure, Cachan (ENS), France
• Associated to the scholarship: 11/00948-9 - Phase separation in mortars: development of evaluation method and influence on rheological behavior, BP.PD

Abstract

The squeeze-flow is a rheological test based on the compression of a cylindrical sample between two parallel plates and has been used, in addition to rotational rheometry, as a complementary method for characterizing fresh mortars. As a result, the squeeze-flow testing method for rendering and masonry mortars was recently standardized (ABNT NBR 15839:2010). During squeezing-flow of mortars phase separation is likely to occur due to the multiphase nature of the material and the characteristics of the method, therefore it must be measured and considered for an adequate analysis of the rheological behaviour. For this reason, a gravimetric-based methodology was developed for measuring the liquid-solid separation induced by the test and, then, allowed for a substantial progress of the knowledge related to the squeeze-flow of mortars. However, this methodology provides information regarding the water distribution after the test, but not if paste-aggregates separation occurs during flow. This project - for research internship abroad designed for 6 months - aims to determine de influence of paste viscosity and particle size distribution of aggregates on the squeeze-flow behaviour and phase segregation of mortars. It also intends to verify the occurrence of paste-aggregates separation by X-ray tomography associated with gravimetric tests. The mortars (cement + sand) to be studied will differ in paste viscosity (using different water and viscosity modifiers contents), while granular permeability will vary by aggregate particle size distribution and morphology. Rotational and squeeze-flow rheometry methods will be applied for rheological evaluation of pastes and squeeze-flow will be employed for mortars in association with photoelasticity methods to assess the stress fields developed during flow. At last, a model for prediction of phase segregation based on concepts of fluid percolation throughout porous media will be applied and compared to experimental results. The supervisor, Mohend Chaouche, is a Directeur de Recherche - Centre National de la Recherche Scientifique (CNRS, France) and head of the LMT-Cachan research group Rhéologie et formulation des nouveaux matériaux cimentaires. Dr. M. Chaouche has great experience on rheology, squeeze-flow and phase segregation of suspensions, including cement pastes, and has been publishing papers in high-level international journals in the fields of cement-based materials and rheology. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

CARDOSO, FBIO A.; FUJII, ALESSANDRA L.; PILEGGI, RAFAEL G.; CHAOUCHE, MOHEND. Parallel-plate rotational rheometry of cement paste: Influence of the squeeze velocity during gap positioning. CEMENT AND CONCRETE RESEARCH, v. 75, p. 66-74, SEP 2015. (11/00948-9, 12/18952-5, 13/27121-2)