How much water and fibres do I need for a small concrete pour?

The approx ratio of water is 12-15% to the GFRC Worktop Premix. The ratio of fibres is approx 3% of the weight of dry powder.

So the methodology is as follows;

Weighing Out

1. Preblend your dry mix first to ensure all ingredients are well distributed.
2. Weigh out your desired amount of dry premix ( X amount of Kg)
3. Multiply X by 0.12 = weight of water in Kg
4. Multiply X by 0.06 = weight of fibres in Kg


Gradually add and mechanically mix the water into the premix powder until all lumps have gone. It should be like a thick milkshake. If you’ve used all the water and this consistency has not been reached, add small increments of water mixing thoroughly until you reach this consistency.

Leave the mix to rest for 15 minutes. It will stiffen up.

After fifteen minutes mix the concrete premix again. If it remains stiff, gradually add water again until a thick milkshake consistency has been reached.

Now add the fibres. Blend them into the mix for no longer than 3 minutes so as not to break them up too much.

Now pour!

By Toby Hurst


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