Super Strength Fastcrete


Cemix Super Strength Fastcrete For any posthole concrete project requiring fast setting high strength with structural requirements up to 30MPa. The average Kiwi Fence stands between 1.2m - 1.8m high supported by 100 x 100 H4 posts. Cemix recommends 2 x 20kg bags per post.

Typical Application & Uses:

  • Larger signs and washing lines
  • Foundations and footings
  • Retaining walls
  • Sun Sail Posts
  • Heavy duty fence posts
  • Structural applications


  • No mixing required
  • Fast setting
  • High strength
  • Easy and convenient to use

20kg & 25kg


Dig a hole and place your post in it. Keep the post off the ground to prevent rot and also apply Cemix® Bituproof Plus on the part of the post that will be sub ground. Completely wet the hole and compensate for any ground drainage that might soak up the water required for Cemix® Super Strength Fastcrete. In sandy soils, line the hole with plastic. Pour 2.5 - 3.5 litres of water per bag of Cemix® Super Strength Fastcrete. Position the post in the centre of the hole. Evenly and slowly pour the dry contents of the Cemix® Super Strength Fastcrete around the post. Ensure the concrete gets wet progressively as you pour. Do not empty the bag quickly as this will lead to dry patches and you will have to rod to allow for water penetration. If any dry product is visible on the surface, sprinkle water over to dampen.

Due to the fast setting time of Cemix® Super Strength Fastcrete, do not mix in a concrete mixer or wheelbarrow.

After a minimum of 15 minutes the hole can be topped up with earth and after one hour the post can withstand wire straining or similar pressure. It is recommended that a third of the post should be below the ground. The diameter of the hole in the ground needs to be a minimum of twice the diameter of the post. For structural applications such as footings, ensure the product is left to cure for 7 days.


Cemix® Super Strength Fastcrete consists of a properly proportioned mixture of stone, gravel, sand, Portland cement and other admixtures approved for use in concrete that will harden in 15 minutes to achieve 30Mpa target strength in 28 days.

Technical Data:

Appearance – Cementitious grey powder

Strength (MPa) – 20MPa @ 7 days, 30MPa @ 28 days.

Application Temp – 5 oC – 30oC

Yield / Coverage - .0096m3 per 20kg bag

Packaging – 20 & 25kg bags.

The data shown above reflects typical results based on laboratory testing under controlled conditions. Reasonable variations may occur on site.


Cemix® Super Strength Fastcrete in a cool dry area and use within 6 months.


Clean all tools with water & brush immediately after use.


Variations beyond recommended water demand will compromise strength.