Rheological behavior of mortars: comparison between rotational and squeeze-flow techniques

Fabio Cardoso, Vanderley John, Rafael Pileggi, Phillip Frank Gower Banfill

Research output: Contribution to conferencePaper

Abstract

Rotational rheometry is widely used to overcoming the limitations of the tradi-tional single-point methods, by evaluating concretes and mortars under a con-siderable range of shear rates. The development / evolution of methods for these materials generally seeks more adequate experimental conditions through the use of specific devices / geometries and testing routines aiming to fulfil the basic physical requirements of no slip or segregation for the proper application of rheological models and/or to simulate flow situations of scientific and tech-nological interest. In this sense, squeeze-flow testing – i.e. compression of a cy-lindrical sample between parallel plates – has been applied as an alternative / complementary technique to assess the flow behaviour of building materials. Its geometry change during gap reduction makes the method particularly interest-ing, as it creates flow conditions similar to those involved in processing and ap-plication of pastes and mortars. Therefore, this work focus on the experimental comparison between squeeze-flow and rotational shear for evaluating the rheo-logical behaviour of mortars. Several Brazilian and European rendering prod-ucts showed a wide range of workability behaviour in both testing modes. The flow curves and hysteresis effects during the shear cycle varied significantly, since the mortar’s composition affects structural breakdown, interfacial slip and phase separation. The latter plays a critical role during squeeze-flow and is the main reason for the higher loads required to deform the samples at lower rates. For some mortars showing low phase separation it was possible to compare shear and extensional viscosities, hence Trouton ratios between 20 and 40 were obtained.
Original languageEnglish
Number of pages16
Publication statusPublished - 3 Mar 2016
EventConference on Rheology of building materials - Ostbayerische Technische Hochschule, Regensburg, Germany
Duration: 2 Mar 20163 Mar 2016
Conference number: 25

Conference

ConferenceConference on Rheology of building materials
CountryGermany
CityRegensburg
Period2/03/163/03/16

Keywords

  • Mortar
  • Rheology
  • Squeeze-flow

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