When mixing GFRC (glass fibre reinforced concrete), there is a best procedure that should be followed to give you a nice consistent mix.
Firstly you should batch out all of your materials in to suitably sized mixing buckets. Batching out your entire mix ahead of pour removes an element of the process which is time consuming and can prove to be stressful mid pour. Having your materials weighed out pre pour free’s you up to focus on some of the finer details or unforeseen’s that could need attending too once underway.
When batching out your materials you should start by adding the sand first then cement, Trinic silica fume and additives (TEC-10, Plasticiser, Pigment ect.). Fibre should be weighed out separately, to be added to the mix last. It’s important to add the materials in this order as it will allow for the best blend and shouldn’t leave any unmixed material stuck in the bottom of the bucket.
Add approximately 80-90% of the water and once its in you can start to mix, you want to allow the paddle of the mixer to only drop down through the cement not the sand, this will help to blend the additives, silica fume and cement togeather and also breakdown any lumps in the cement. Make sure you have a trowel on hand to scrape the sides on the mixing bucket to be sure that no material is left unmixed. Once the cement and additives are mixed, approximately a minute or two, you can push the mixer down to the bottom of the bucket and introduce the sand. At this stage you will also add the remaining 10-20% water and continue to mix for a couple of minutes further, making sure there’s no lumps and a nice consistency to the mix.
Lastly add the fibre. This should be done on a low to medium speed and just enough to wet the fibre and mix it through, this technique will avoid excessive fibre breakage that may cause the mix to fluff up or act as a viscosity modifier stoping the mix from flowing.