Master's Degree Project: Recycled Aggregate in Concrete

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  • Mixing experimental concrete: "how do we know when it's ready?"

    This is my Master's research on recycled polystyrene used as an aggregate in concrete.  The experiment include four mixes: control, 7.5% experimental aggregate, 12.5% experimental aggregate, and 17.5% experimental aggregate by volume.  After mixing, the samples are left to cure and are weighed and compression tested at 14, 28, 56 and 70 days.
  • Mixing in action: video of the concrete mixing taking place!
  • Some images from mix day and testing days...
  • Mix Day: measuring out the concrete components
  • The three experimental mixes in increasing order of polystyrene beads.  The polystyrene replaced gravel aggregate as it is similar in size but possibly provides increased lateral flexibility.  From top: 7.5% volumetric mix, 12.5%, and 17.5%.
  • My 32 experimental and control samples curing in the SFSU basement.
  • Where all the concrete samples will eventually end up: being compression tested until failure (cracking/breaking apart) in the Soiltest machine.
  • Day 56: Great example from the 7.5% experimental aggregate mix showing evenly distributed particulate and breaking shape.
  • "Double, double toil and trouble" - too much polystyrene aggregate floated to the top of a sample of the 17.5% mix, resulting in low compression strength particularly in that region.
  • Day 56: Crushed sample close-up of internal aggregate with Vernier calipers for measurement.