The Brew Cabin

Posted: **Fri Jul 24, 2020 10:04 am**

Iâ€™m building a slab-on-edge retainer using 600mm square slabs, 9 1/2 slabs long.

I have questions about bedding and haunching.

Firstly, can or should the bedding concrete be different From the haunching concrete with regards to strength and consistency? I ask partly because I might prefer a dryish mix for ease of working when bedding the slabs?

Also, can the job be done in stages, e.g. all the bedding one day followed by haunching the next, or some other combination? I.e., will the structural integrity of the wall be significantly compromised if the concrete is not â€œpouredâ€� in one day?

Posted: **Sat Jul 25, 2020 12:24 pm**

The concrete can all be the same strength, but I wouldnt suggest trying to bed and then haunch later, it needs to all be bonded together for maximum strength
You could bed them on a dryish mix, but then wet it up for the launching, as long as the time between the two is a minimum

Posted: **Mon Jul 27, 2020 5:47 pm**

Although construction drawings (including my own - https://www.pavingexpert.com/featur06 ) usually show the concrete for bedding and haunching as one element, in practice, the upright flags are usually placed onto a bed of fresh concrete, spragged in some way to support them, and then haunched at some later point, maybe the same day (if possible) but it could be a day or more later. This results in a day joint, but, as far as the concrete is concerned, it can all be the same mix, usually a ST1/C7.5.

I had some great flag-on-edge under construction photies and they (along with 53,975 others) were lost when an external HDD crashed when I had no back-up! And, of course, I;ve never had the opportunity to photo-shoot a similar installation since!

Posted: **Tue Jul 28, 2020 7:01 am**

Excellent, thanks Tony.
Would a bond bridge help to strengthen the day-joint? I was intending to use some on the slabs anyway.

Posted: **Tue Aug 25, 2020 6:35 pm**

Apologies for being late to this - had all sorts of health issues with angina during the heatwave and now an arthritic knee that is driving me mad with pain.

It would, slightly, but not wiorth the effort, if truth be told!

The Brew Cabin

Slab on edge retainer