While grey industrial style concrete is very popular, there are many homes and businesses that want greater visual impact from their floor. Adding colour, integrally or via stains, is one option to achieve this. Another popular option is to add special decorative elements. Coloured glass aggregates are the most popular of these, and can be added to concrete floors as they are placed. The glass reflects light and colour and adds a unique visual component to the floor.

Decorative glass aggregates are available in a wide range of colours, shapes and sizes. Glass will not colour the concrete and usually looks best when used with integrally coloured concrete. While dyes or stains can colour the floor, glass risks complicating the process and may cause the dye to pool. Glass aggregates can overwhelm a room, so some experimentation in the design phase is advisable. Some of the most attractive concrete floors combine integral colour, decorative aggregates and a smaller number of glass aggregates to add visual interest.

Unlike a normal aggregate, decorative aggregates should only sit in the surface layer of the floor. They are significantly more expensive than traditional stone aggregates, so they need to be applied with care. It is essential to mix a small batch of the mix, as a sample to see how the final floor will look. Without the light passing through it, the appearance of glass will change. It will retain translucency when set in the concrete, but because only one surface will receive light it becomes less apparent. Take the mix design samples and look at them under lighting similar to that the floor will be placed under. This is the best way to understand how the finished floor will look.

How to Use Glass Aggregates

Placing glass or decorative aggregates requires care and precision. Adding it into a standard concrete mix would be expensive and pointless as the aggregates would sink to the bottom of the mix. They can be mixed with an overlay, however. If this is the selected method, it is best to use smaller sizes of glass. Larger pieces run the risk of sinking to the bottom, leaving little exposure even after grinding. Normally a 50% load is advised for this kind of mix. It is important not to use a spiked roller on the floor as it will push the aggregates down into the paste.

The second method for applying glass aggregates is known as “broadcasting” and involves adding the glass at a later stage. The aggregates are scattered onto the surface of the floor after the floor has been placed. There is a delicate balance to be reached. If the glass is broadcast across the floor too soon it may sink to deeply into the concrete. If left too  late, aggregates may protrude too far out and pull-out when the floor is being polished. Larger pieces should be broadcast later in the process than smaller pieces are. Either way there almost certainly will be pull outs which will require filling.

  • The normal process for broadcasting is as follows:
  • Prepare and place the concrete floor, using the tools and methods normally followed.
  • Use a bull float to smooth the surface, but do not rough trowel or finish trowel the surface.
  • Scatter the glass aggregates across the floor in the agreed colour and pattern.
  • Gently trowel the dispersed glass into the surface, being careful not to push the glass in too deeply.
  • Allow around seven days of curing time, dependent on surrounding conditions.
  • Grind the concrete starting at 50 grit and moving up through grit sizes. There is no need to polish wet, the glass grinds uniformly.
  • Densify the floor and then move on to the polishing stages.
  • Clean the floor of all dust and debris, then seal.


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