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How To Mix Back Fill Trowelable Concrete

How To's - Surface Repairs

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A how to guide on mixing HardMaster W610 back fill trowelable 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.

NOTE: Water 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. The below figures are derived from laboratory testing at 20°C and at a WSR of 0.11

DESIGN MANUAL FOR ROADS & BRIDGES – Vol 7 Sec 2

The department of Transport HD 27/04 Clause 3.11
Mortars for bedding ironwork may be trafficked when the strength is expected to be 20N/mm 2. For rapid construction, this should be achieved within 2 hours.

QUALITY CONTROL: tested and packaged to quality control procedure in accordance with BS EN ISO 9001.

Water Addition	2.3 – 2.8 litres / 25kg
Yield	12.2 litres / 25kg
Workability	5 – 10 minutes
Set Time	< 20 minutes
Shrinkage	Less than 0.001%
Density	2250 – 2300kg/m³
Compressive Strength
After 1 Hour	15 N/mm²
After 90 Minutes	20 N/mm²
After 2 Hours	23 N/mm²
After 1 Day	31 N/mm²
After 7 Days	42 N/mm²
After 28 Days	50 N/mm²

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 rubber OX Pro Rubber Blade Mixing Paddle coupled with a twin handled mixing unit.

5. Application of Trowelable HardMaster W610

Trowel HardMaster W610 into the desired area, distribute evenly and then using a concrete float to smooth and compact the concrete mixture.

HardMaster W610 Trowelable 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 W610 should be placed on the pre-wetted application area without delay after mixing. When backfilling around carriageway ironwork or completing patch repairs ensure the material is tamped down and well compacted as soon as possible after placing. HardMaster W610 can be placed 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 W610 should be placed on the pre-wetted application area without delay after mixing. When backfilling around carriageway ironwork or completing patch repairs ensure the material is tamped down and well compacted as soon as possible after placing. HardMaster W610 should be used to encase the flange of any ironwork and then be brought to a height 40-50mm below the required surface of the carriageway or footpath. HardMaster W610 can be finished by floating using a trowel or similar.

Once the HardMaster W610 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.