Master GFRC Mixing: Step-By-Step Guide & Tips!

Optimised GFRC Mixing Guide: How to Mix Glass Fibre Reinforced Concrete (GFRC) for Quality Results

When working with GFRC, it is crucial to follow the right mixing process to achieve durable and beautiful concrete products. In this guide, we will walk you through the steps for MACt GFRC mixing products, provide you with some helpful tips, and discuss the different types of mixes and demoulding times.

Remember, safety comes first. Always work in a well-ventilated area and wear personal protective equipment (PPE), such as gloves, safety glasses, and a mask, to protect yourself from dust.

Step-by-Step GFRC Mixing Process:

  1. Prepare Your Ingredients: Before mixing, ensure that you have all your ingredients weighed out. You will need water, premix, colour, plasticizer, and fibres for a pourable mix. The exact amounts depend on the mix type, as specified in the guide below.
  2. Pre-mix Premix, Colour, and Plasticizer: To prevent clumping and ensure even colour distribution, dry mix the premix, colour, and plasticizer in a separate bucket before adding them to the water.
  3. Combine 80% of Premix Mixture with Water: Pour the premix mixture into the water (not the other way around) to reduce clumping and ensure proper mixing. Blend the mixture until it has a smooth and consistent texture using a mixer.
  4. Add Remaining 20% of Premix Mixture: Continue mixing after adding the remaining premix mixture to the water, ensuring a homogeneous mix. Scrape the sides and bottom of the bucket to mix all the materials thoroughly.
  5. Adjust Consistency if Needed: If the mix is too thick to pour, add more plasticizer, not water, to make it flowable without reducing strength. Adding water will change the colour and make matching colours impossible.
  6. Incorporate Fibres: Add the fibres to the mix once the desired consistency is achieved and mix until homogeneous. Thoroughly mixed fibres ensure strength and durability in the final product.

Tips for Successful GFRC Mixing:

  • Invest in Quality Mixing Gear: High-quality mixers and equipment help ensure proper blending and reduce errors and inconsistencies.
  • Adjust for Temperature: In cold weather, use cold water for a more flowable mix, but don’t dry mix plasticizer. In hot weather, cool down the mix by replacing some water with ice (1kg ice and 2kg water is recommended).
  • Pour at the Right Time: In hot temperatures, pour during cooler times of the day to extend the work time before initial setting, ensuring proper mix setting and preventing premature drying.


With practice, you will master GFRC mixing and create stunning, durable concrete products. Experiment with different fibres and additives to achieve unique textures, colours, and finishes.

GFRC Mix Designs:

  • Flowable Mix: 20kg MACt Premix, 3L Water, 20g MACt Plasticiser, 40g 3mm HD Fibres, 500g 13mm Bundled Fibres, Colour
  • Sprayable Mix: 20kg MACt Premix, 2.9L Water, 10g MACt Plasticiser, 40g 3mm HD Fibres, Colour
  • Hand Packed: 20kg MACt Premix, 2.5L water, 40g 3mm HD Fibres, 400g 13mm Bundled Fibres, Colour

Demoulding Times for GFRC:

Properly monitor and evaluate the curing process to determine the right time to demould your GFRC piece. Demoulding too early may cause cracking or breaking, while demoulding too late can make it difficult to remove the piece from the mould. Here are some ways to assess if the GFRC piece is ready to be demoulded:

  • Tap Test: Tap the GFRC surface with a metal rod or another hard object and listen to the sound it produces. A dull thud indicates it is still wet and not fully cured. When the sound becomes crisp and metallic, the GFRC piece is ready to be demoulded.
  • Surface Moisture Level: Check for visible moisture on the GFRC surface. When the surface is no longer visibly moist and has a matte finish, it is a sign that the GFRC is ready to be demoulded.

Curing time varies based on mix design, environmental conditions, and the size and complexity of the GFRC piece. Generally, allow GFRC to cure for at least 24 hours before attempting to demould.

Use a combination of methods like conducting a tap test, checking surface moisture levels, and adhering to recommended curing times to determine when a GFRC piece is ready to be demoulded. Proper monitoring and evaluation of the curing process help ensure the GFRC piece is fully cured and ready for removal from the mould without any damage.

These steps, tips, and guidelines, you will be master in GFRC mixing and achieve high-quality, durable concrete products. Do not forget to prioritize safety when working with any product that produces dust, and always work in a well-ventilated area with appropriate PPE. With practice and experimentation, you will soon become an expert at mixing GFRC and creating stunning, strong concrete creations.

Related Articles