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The effect of pre-treatment on the thermal performance of fly ash geopolymers
Rickard, W.D.A.,Borstel, C.D.,van Riessen, A. Elsevier 2013 Thermochimica acta Vol.573 No.-
This paper presents a study on the thermal behaviour of fly ash geopolymers that have been pre-treated prior to thermal exposure. Thermal and mechanical analysis was conducted on geopolymers that were leached in water and gradually dried and the results were compared to untreated samples. The aim of the pre-treatment was to remove the water and the excess alkali without damaging the structure prior to high temperature exposure. Fast dehydrating water is known to damage geopolymers by inducing cracks. Alkalis are known to be network modifiers and as such, where in excess, reduce the melting point of aluminosilicate glasses. It was found that the pre-treatment produced samples with negligible thermal expansion up to 700<SUP>o</SUP>C and less damage associated with dehydration which increased their post firing compressive strength. The pre-treated geopolymer panel had a marginally shorter fire rating than the as-cured sample though it exhibited greater resistance to cracking and slower post dehydration temperature increases.
Performance of fibre reinforced, low density metakaolin geopolymers under simulated fire conditions
Rickard, W.D.A.,Vickers, L.,van Riessen, A. Elsevier 2013 Applied clay science Vol.73 No.-
This paper presents a study on the thermal behaviour of metakaolin based geopolymers that have been foamed and fibre reinforced in order t1o assess their suitability for high temperature applications such as thermal barriers and fire resistant panels. An international standard fire curve (ISO 834, 1999) was used to simulate the heating conditions of a fire. Fire testing was conducted on 50mm thick panels with an exposure size of 200mmx200mm. Fire ratings of more than one hour were achieved for all samples.
The onset of extreme fire behaviour in a mine drift
Rickard Hansen 한국자원공학회 2018 Geosystem engineering Vol.21 No.5
The onset of extreme fire behaviour in a mine drift with longitudinal ventilation was analysed. A fire in a mine drift with continuous fuel load, involving several separate fires may lead to flames tilted horizontally and filling up the entire cross section. This will lead to earlier ignition, higher fire growth rate, higher fire spread rate and a severe fire behaviour. The focus has been on what changes take place at the onset and signs of the impending phenomenon. It was found that the fire gas temperature at the ceiling level provided a poor indicator. At the downstream far-field region of the fire, the sudden temperature increase at the lowest levels of the cross section and the sudden increase in flow velocities would provide signs of extreme fire behaviour. The corresponding full-scale heat release rates of the experiments at the onset of extreme fire behaviour were found to be very high for mining applications but not necessarily for tunnel fires. The heat release rate threshold for a mine drift with smaller cross-sectional dimensions would decrease considerably, increasing the likelihood of occurrence. The distance between the fuel items will play an important role during the initiation of horizontal flames.
Thermal analysis of geopolymer pastes synthesised from five fly ashes of variable composition
Rickard, William D.A.,Temuujin, Jadambaa,van Riessen, Arie Elsevier 2012 Journal of non-crystalline solids Vol.358 No.15
<P><B>Abstract</B></P><P>This paper presents a study on the thermal properties of a range of geopolymers in order to assess their suitability for high temperature applications such as thermal barriers, refractories and fire resistant structural members. Geopolymers were synthesised from five different fly ashes using sodium silicate and sodium aluminate solutions to achieve a set range of Si:Al compositional ratios. The thermo-physical, mechanical and microstructural properties of the geopolymers are presented and the effect of the source fly ash characteristics on the hardened product is discussed, as well as implications for high temperature applications. The amount and composition of the amorphous component (glass) of each of the fly ashes was determined by combining XRD and XRF results. It was found that the Si:Al ratio in the glass of the fly ashes strongly influenced the thermal performance of the geopolymers. Geopolymers synthesised from fly ashes with a high Si:Al (≥5) in the glass exhibited compressive strength gains and greater dimensional stability upon exposure to 1000°C, whereas geopolymers synthesised from fly ashes with low Si:Al (<2) in the glass exhibited strength losses and reduced dimensional stability upon high temperature exposure.</P> <P><B>Highlights</B></P><P>► Quantification of the crystalline and amorphous phases of five different fly ashes. ► Si:Al ratio in the glass of the fly ash influences the thermal performance. ► Compressive strength of geopolymers can increase by up to 5 fold after firing. ► Sodium aluminate activated geopolymers exhibit thermal stability up to 800°C. ► Sintering during thermal exposure improved inter-particle bonding.</P>
Modelling temperature distributions and flow conditions of fires in an underground mine drift
Rickard Hansen 한국자원공학회 2020 Geosystem engineering Vol.23 No.6
An analysis on the modelling of fire gas temperatures and fire gas velocities in a mine drift with longitudinal ventilation is conducted. A computational fluid dynamics (CFD) model and a number of empirical correlations are validated against the results from two full-scale fire experiments in a mine drift. During the analysis it is found that the upper level (ceiling) fire gas temperature at 35 and 50 m from the fire is well fitted when comparing the results from the CFD modelling with the experimental results. The fire gas temperatures at the lower level are found to be over predicted by the CFD model. The ceiling fire gas temperatures directly above the vehicles are over predicted in one case and under predicted in the other case by the CFD model. The empirical models are found to over predict the average fire gas temperature during extensive parts of the fires. The fire gas velocities at the higher section are found to be under predicted and the fire gas velocities at the lower section are over predicted by the CFD model. Future studies should be aimed at developing empirical models for mining applications as well as validating developed CFD models.