Master Thesis: Production and characterization of foam glass from container glass waste

logo_smallThis master thesis, written by Dina Mohamed Abdel Alim at “The American University in Cairo, The School of Sciences and Engineering” is a nice introduction to cellular glass. I copy the abstract hereunder:

Foam glass with excellent properties was produced from container glass waste. The
processing technique depended on the powder sintering approach using sodium
silicate solution as a foaming agent. The morphology, density and compressive
strength were studied in relation to different processing parameters: sintering
temperature, amount of foaming agent, soaking time, powder particle size and glass
powder color. Foam glass was sintered in the range (750-900C) for 30 minutes with
the incorporation of 12 and 19 wt. % sodium silicate solution. At lower sintering
temperature (750-800C), the foam has denser structure (bulk density ranged from
0.37-0.61 g/cm³) along with high compressive strength (ranged from 2.29-18.68
MPa). As the sintering temperature increased, higher levels of porosity were achieved.
At 850C with 12 wt. % sodium silicate solution, lightweight (bulk density = 0.25
g/cm³), highly porous (% of porosity = 90 %) foam glass was achieved. It had
relatively high compressive strength (1.62 MPa), compared to other insulating foams,
along with low thermal conductivity (0.078 W/mK) and the most homogeneous pore
morphology. Significant change in foam glass properties took place with changing the
amount of foaming agent. As the amount of foaming agent increased, the density of
the foam decreased till it reached a minimum of (0.25 g/cm³) that corresponded to 12
wt. % sodium silicate solution. Further addition of foaming agent caused the density
to re-increase and the pore morphology to coarsen. Sintering foam for different
soaking times had a slight effect on changing the foam glass properties. The
morphology of all the foam glass produced at different soaking times was
comparatively homogeneous. The compressive strength of the produced foam was
relatively high (1.6 MPa at 40 min and 3.13 MPa at 10 min). The powder particle size
had a major effect on foam glass properties. As the particle size increased, the bulk
density of the the foam increased and the morphology became less homogenuous.
Increasing the sintering temperature for the larger particle size did not succeed in
increasing the foam structure homogeneity. The glass color also had an effect on the
foam glass properties. The properties and the morphology of the green and brown
glass samples were approximately the same (bulk density = 0.38, 0.37 MPa and
compressive strength = 2.05, 1.97 MPa respectively). However, they differed from the
morphology and properties of the white glass (bulk density = 0.25 g/cm³) and
compressive strength = 1.62 MPa). The specific compressive strength of the white
glass foam (6.48*10-3 MPa m³/Kg) was higher than that of green and brown glass
(5.39*10-3, 5.32*10-3 MPa m³/Kg respectively). EDX analysis was performed for the
white, green and brown powder. It showed that they had more or less the same
compositions (except the presence of chromium element in green glass and titanium in
brown glass which are coloring additives). They had the same main elements but with
different weight percentages.
The optimum processing parameters for producing foam glass for thermal
insulation was to use sintering temperature 850 C, amount of foaming agent 12 wt.
%, soaking time 30 min and glass powder particle size 75 μm.

I don´t like to see a specific compressive strength because this property does not depend linear on the density. But further, we observe

  • a good introduction to glass
  • a nice transition to waste glass and its recycling problems and further to
  • to cellular glass: current production method and applications as thermal insulation
  • and a benchmarking between alternative thermal insulation materials with focus on life time
  • applications in building and industrial insulations and alternative applications
  • the use of foamed glass gravel
  • theoretical study of cellular structures
  • open and closed cell recipes
  • sodium silicate as a foaming agent
  • thermal analysis of this recipe
  • very interesting thermal imaging of the foaming
  • annealing of the foam (without mentioning the thickness)
  • different glass compositions to foam
  • mechanical properties
  • designed experiments to investigate the different parameters
  • the effect of the color of the cullet on the foam quality

This master thesis could also have a been a PhD thesis, it is really a nice piece of work.

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