How to utilise our defect-free HardMaster CD534

How to utilise our defect-free HardMaster CD534

In this series of ToolBox Tips, we will be looking at a product from our Magma range of reinstatement & surfacing materials, the HardMaster polymer modified mortars W620 & W621.

These 2 mortars are used in conjunction to provide the high compressive and flexural strengths required for ironworks in highways. They conform to CD534, which is the recently released document that has replaced HA104:09. They are mixed with a pre-measured polymer resin component rather than water.

The HardMaster W620 trowelable bedding mortar is used as a damming material to stop the flowable mortar running underneath the frame & down the chamber. HardMaster W621 is a flowable bedding mortar and is used to hold the frame without any air voids, which would lead to water ingress & failure.

It is also essential to have the right tools for this type of application: a gorilla bucket, water carrier, measuring jug, paddle mixer (with power source), steel float and bucket trowel.


When starting the application, it's important to make sure the substrates is sound, clean, and free from dirt, oil and other contaminants. Proper surface preparation is vital to ensure the successful application and durable performance. All substrates should be pre-wetted with water prior to the application of the concrete and, any standing water should be removed.



For best results, HardMaster W620 should be mixed using a heavy duty mixing whisk with a 10mm Ox pro rubber blade mixing paddle. Pour the activator into a suitable mixing container, reserving approxmertly 200ml, then slowly add the contents of the 18kg bag whilst mixing thoroughly. Add the sachet of red dye at this point if required. The product should be mixed for 2-3 minutes until a smooth, homogenous concrete consistency is achieved. This may require adding the reserved activator.



The first process is to set the manhole cover on the chamber and adjust the height so it is flush with the surface level.

Whilst the W620 trowelable bedding mortar can be used to bed the manhole cover fully, in this application method, we use it to create a bung around the inside of the cover.

Using a trowel or heel of a gloved hand place the W620 mortar in the gap on the inside face of the frame and chamber top. Taking care not to leave any voids and to produce a 'dam' with a pointed, smooth finish. Allow this to stiffen and once this bedding material has reached its initial set, the backfill material HardMaster W621 flowable can be used.

It is essential to pick the highest corner and pour the product in from that corner only, letting the mortar flow all the way around and underneath the flange.  As you can see, this pushes all the air around in one direction guaranteeing zero air voids underneath the flange and no chance for failure.

Once this material has reached its initial set, the reinstatement can be backfilled. HardMaster W615 flowable backfill concrete, and completed with PermaFyx L271 (This product has been replaced with PermaFyx L273) with either 6mm or 10mm aggregate. This cold applied system can also be used to backfill and create the finished surface, which is far quicker, allowing the whole process to be completed in under 90 mins. 



Tools and equipment should be cleaned using water as soon as possible after application.

Quick Summary:

  • Complies with Department of Transport HD 27/04 Design Manual for Roads and Bridges CD534 and NRA MCDRW Vol 1 Clause 501.17.
  • Controlled quick setting
  • Fibre-reinforced
  • Shrinkage compensated
  • High final strength
  • Exceptional performance in wet conditions
  • Guaranteed cure
  • Controlled quick setting
  • High final strength
  • Easy to use
  • Self-levelling

Take a look at the Training Academy video for yourself:


 ToolBox Tips HardMaster W620 & W621

If you want to know more about our HardMaster W620 & W621 you can find additional technical data, within our technical datasheet for the W620 & W621 here. If you are interested in using these products please don't hesitate to contact us by calling 023 9220 606 or emailing us at