How To Mix HardMaster W615

Marketing Team

A how to guide on mixing HardMaster W615 Flowable concrete. Including mix instructions and water ratio amounts. 

1. Prepare The Area

The area should be prepared to the correct specification for the application. All application substrates must be sound, clean and free from dust, dirt, debris, oil, grease and other contaminants. Proper surface preparation is vital to ensure the successful application and durable performance of the concrete. All substrates should be pre-wetted with water prior to the application of the mortar, however any standing water should be removed.

Required Materials

2. Mixing Instructions And Water Ratios

Please note: water is added first then the concrete mix is added to the water. 

Mix each 25kg unit with 2.3 – 2.8 litres of clean water (which complies with BS EN 1008 – water for concrete). Pre-measure the required volume of water into a clean mixing vessel and steadily add half the powder to the water. Then add another quarter of powder and mix again, before adding the final quarter and mix well, adding the rest of the water if required. The product should be mixed for 2-3 minutes until a smooth, and mortar like consistency is achieved.

Due to the rapid setting nature of HardMaster W615 Flowable Concrete, only ever mix a quantity of material that can be used and placed within 5 minutes of the end of mixing. 

DO NOT re-mix or add extra water to extend the working time of the material.

NOTEWater consumption can be impacted by calcium content i.e. in different soft water and hard water areas.

3. Technical Performance Data

Concrete continues to harden over time, the HardMaster range is developed to set quickly (within 90 minutes it can be opened to traffic), yet have an extended workability time up to 10 minutes and then set extremely quickly and continue to do harden over time. 

Water Addition 2.3 – 2.8 litres / 25kg
Yield 12.0 litres / 25kg
Workability 5 – 10 minutes
Set Time < 20 minutes
Shrinkage Less than 0.001%
Density 2250 – 2300kg/m³
Compressive Strength
After 1 Hour 8.0 N/mm²
After 90 Minutes 20 N/mm²
After 2 Hours 22 N/mm²
After 1 Day 31 N/mm²
After 7 Days 42 N/mm²
After 28 Days 50 N/mm²


Workability Time Explained:

4. Mix The Concrete Mix For 2-3 Minutes Using A Powered Mixer And Paddle. 

Using a powered mixer and mixing paddle for 2-3 minutes. Secure the bucket  when using the powered mixer so the bucket doesn’t tip over. The mix will be heavy and we would recommend using a powered mixer like a Collomix in this video we use a cordless version. For best results HardMaster W615 should be mixed using a steel Meon OX Pro Mixing Paddle coupled with a twin handled mixing unit.

5. Pour HardMaster W615

Pour HardMaster W615 into the desired area, distribute evenly and then using a concrete float smooth the concrete mixture. 

HardMaster W615 Flowable Concrete should be applied at a thickness of 30mm – 250mm in a single pass. If thicker sections are required, this can be achieved using the layer-on-layer method.

HardMaster W615 Flowable Concrete should be placed on the pre-wetted application area without delay after mixing. When backfilling around carriageway ironwork or completing patch repairs guide the material into the desired location using a trowel. Due to the flowing nature of the product, good compaction should be easily achieved. HardMaster W615 Flowable Concrete should be used to encase the flange of any ironwork and then be brought to a height 40mm below the required surface of the carriageway of footpath. HardMaster W615 Flowable Concrete can be finished by floating using a trowel or similar. Once the product has reached initial set, the reinstatement process can then be continued.

For optimum results, use Meon BituSeal, bitumen edge sealer to seal any vertical edges, then apply and compact Meon PatchMaster to the finished level of the ironwork. Meon ThermaBand can then be applied to the surface joints to prevent future cracking. (See corresponding TDS Sheets for more information).

Recommended ambient application temperature is 5°C to 25°C.

6.  Clean Off The Tools

Clean off the tools, paddles and floats using water. Discarding any waste water according to your waste disposal guidelines. 

Recommended Mixer

We recommended the Collomix Cordless Mixer, being cordless makes it possible to work in remote areas, and it is incredibly powerful. Make sure you have secured the bucket before you use this. The Collomix makes light work of concrete, resin bound mixing and plaster. 



DO NOT re-mix or add extra water to extend the working time of the material. As it will compromise the integrity of the concrete.