Is my mortar too weak?

[DonnySP]

Hi guys,

I've just installed a stone resin shower tray, as per instructions, on a bed of 5:1 mortar. I'm sure the volumes were correct: I used 10 flower-pots full of sand and two of cement. I also put a bit of PVA in as a plasticiser (again, as per instructions).

Now, after about 32 hours, I'm a bit scared that the bl***y stuff is too weak!

When I put the tray down there was a little mortar that oozed out of the gap. I scraped this off and left it on a scrap of wood to see what it was like when it had dried. Initially it was a browny colour, and now it has gone grey so I thought it must be set. Unfortunately, with a bit of effort, I was able to crush it between finger and thumb!

So, what do we reckon? Do you think it will be OK since the load is spread across the whole area? What might be a suitable test to see if will be OK in the long run?

I was thinking that if I stand on the tray and jump about a little bit, and I see no crumbling at the edges, then it might be OK.

Any advice would be greatly appreciated. As you can probably tell I'm panicing a little: I need to get on ASAP because this is the only shower in the flat (and there's no bath).

Cheers, Donny

[Andrew Mawson]

Donny,

The bit on your piece of wood will have dried out before the cement has chemically reacted fully, so will be weak from lack of water at the critical stage. Hopefully your bulk under the shower tray will have stayed wetter longer so should be fine. It doesn't need to be mega hard - even a nice bed of neat compacted sand would do if it would stay in place (which it wouldn't)

Andrew

[Harry Bloomfield]

I would suggest that 32 hours is far to early to be able to judge its final strength, wait a week or so. It does really need to be that strong any way, it will be under compressive load all the time.

[DonnySP]

Thanks for your replies guys. I feel a lot better about it now :)

I did jump about on it a bit and there was no crumbling, just about half a mm of vertical movement at the corner; which doesn't seem bad across a 900mm tray.

Cheers, Donny

[Fatima T. Milner]

To destroy the Target Newsgroup, they will not relate here. On one particular night they posted to a killfile! For someone subscribed to quite vicious personal attacks throughout usenet, even I found this disturbing.

Examples are illegal.

[The Most Rev. Peter Parsnip]

The Lord alerted my mind to the presence of this EVIL article by Harry Bloomfield, and I thusly replied:

After 32 hours, dig a large hole and place Harold inside it.

Fill the hole with concrete. Leave for several millennia.

HTH.