In-situ thermo-mechanical testing of fly ash geopolymer concretes made with quartz and expanded clay aggregates

The mechanical and microstructural properties of geopolymer concretes were assessed before, during and after high temperature exposure in order to better understand the engineering properties of the material. Fly ash based geopolymer concretes with either quartz aggregate or expanded clay aggregate were exposed to various temperatures up to 750 °C using a thermo-mechanical testing apparatus. Microstructural investigations were also undertaken to better understand the measured changes in the mechanical properties. It was found that dehydration of capillary water caused cracking and strength losses at temperatures ≤ 300 °C, an effect that was more severe in the quartz aggregate geopolymer due to its lower permeability. At higher temperatures (T ≥ 500 °C) sintering promoted strength increases which enabled both concrete types to yield significant strength advantages over conventional materials. Stress–mechanical strain curves, which form the basis of the fire design of concrete structures, are reported.

[1]  Daniel Quenard,et al.  Spalling and pore pressure in HPC at high temperatures , 2000 .

[2]  T. Bakharev,et al.  Thermal behaviour of geopolymers prepared using class F fly ash and elevated temperature curing , 2006 .

[3]  Ulrich Schneider,et al.  Concrete at High Temperatures -- A General Review* , 1988 .

[4]  J. Sanjayan,et al.  Effect of transient creep on compressive strength of geopolymer concrete for elevated temperature exposure , 2014 .

[5]  Y. Zaytsev,et al.  Recommendation of RILEM TC 200-HTC: mechanical concrete properties at high temperatures-modelling and aplpications. Part 2: Stress-strain relation , 2007 .

[6]  W. Rickard,et al.  Thermally Induced Microstructural Changes in Fly Ash Geopolymers: Experimental Results and Proposed Model , 2015 .

[7]  P. Michaud,et al.  Silica fume as porogent agent in geo-materials at low temperature , 2010 .

[8]  J. Sanjayan,et al.  Factors influencing softening temperature and hot-strength of geopolymers , 2012 .

[9]  Kristian Dahl Hertz,et al.  Concrete strength for fire safety design , 2005 .

[10]  Grant C. Lukey,et al.  Physical evolution of Na-geopolymer derived from metakaolin up to 1000 °C , 2007 .

[11]  Jean-Marc Franssen,et al.  Consideration of Transient Creep in the Eurocode Constitutive Model for Concrete in the Fire situation , 2010 .

[12]  Jadambaa Temuujin,et al.  Thermal analysis of geopolymer pastes synthesised from five fly ashes of variable composition , 2012 .

[13]  J. Deventer,et al.  Thermal evolution of metakaolin geopolymers: Part 1 – Physical evolution , 2006 .

[14]  Subaer,et al.  Thermo-mechanical and microstructural characterisation of sodium-poly(sialate-siloxo) (Na-PSS) geopolymers , 2007 .

[15]  W. Rickard,et al.  The effect of pre-treatment on the thermal performance of fly ash geopolymers , 2013 .

[16]  Ulrich Schneider,et al.  Recommendation of RILEM TC 200-HTC: Mechanical concrete properties at high temperatures-modelling and applications : Part I. General presentation , 2007 .

[17]  Jay G. Sanjayan,et al.  An investigation of the mechanisms for strength gain or loss of geopolymer mortar after exposure to elevated temperature , 2009 .

[18]  Gabriel Alexander Khoury.  Transient thermal creep of nuclear reactor pressure vessel type concretes , 1983 .

[19]  Kenneth J. D. MacKenzie,et al.  Thermal behaviour of inorganic geopolymers and composites derived from sodium polysialate , 2003 .

[20]  H. Colina,et al.  Transient thermal creep of concrete in accidental conditions at temperatures up to 400°C , 2006 .

[21]  Petr Hlaváček,et al.  Inorganic foams made from alkali-activated fly ash: Mechanical, chemical and physical properties , 2015 .

[22]  K. Pistol.  High Temperature Behaviour of Self-Compacting Concrete with Limestone Powder , 2013 .

[23]  B. Meng,et al.  Transient strain of high strength concrete at elevated temperatures and the impact of polypropylene fibers , 2012 .

[25]  A. Sofianos,et al.  Sodium‐based fire resistant geopolymer for passive fire protection , 2015 .

[26]  W. Rickard,et al.  Strategies to control the high temperature shrinkage of fly ash based geopolymers , 2014 .

[27]  Gabriel A. Khoury,et al.  Transient thermal strain of concrete: literature review, conditions within specimen and behaviour of individual constituents , 1985 .

[28]  Jay G. Sanjayan,et al.  Damage behavior of geopolymer composites exposed to elevated temperatures , 2008 .

[29]  W. Rickard,et al.  Performance of solid and cellular structured fly ash geopolymers exposed to a simulated fire , 2014 .

[30]  Tiesong Lin,et al.  Thermo-mechanical and Microstructural Characterization of Geopolymers with α-Al2O3 Particle Filler , 2009 .

[31]  Jay G. Sanjayan,et al.  Stress–strain behaviour and abrupt loss of stiffness of geopolymer at elevated temperatures , 2010 .