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Martin Bonner Martin Bonner is offline
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Default Mortar setting time

On Oct 29, 10:54 pm, "Andrew Mawson"
wrote:
"Tim Lamb" wrote in message

...



In message
,
Osprey writes
On 29 Oct, 11:19, Tim Lamb wrote:
I am lifting the roof on an old pig farrowing barn to accommodate

a
furniture restorer.


The roof is heavy but can be moved in one piece. So far I have

raised
one side on Acrows and intend to lay two courses of brick to gain

the
height needed.


What is a reasonable time to wait before heavily loading fresh
brickwork? I am particularly nervous of any side thrust

encountered as I
start to jack up the other side.


regards
--
Tim Lamb


I would leave it 48Hrs ... 24 Hrs is no problem if a simple daed

load,
but as you point out there is side thrust, and bricks not

particularly
strong in that direction.


use a good 3:1 mix and suitable bricks, deep frog frettons as a
minimum, laid frog up, and fully filled ... or engineering if you

have
them.


OK. The brickwork will be Flettons for the first course and
semi-engineering for the top. Basically because that is what I have
lying about the farm:-) I can easily wait 3 days as I also have to

fit a
wider door and re-plumb the electrical conduit.


regards
--
Tim Lamb


Tim,

Very temperature dependant: I've just laid 8 cu m of RC40 concrete and
it took two days in the current cold snap to 'not' take a finger
impression. Earlier in the year I laid a batch of the very same stuff
on a blazing hot day and we couldn't finish tamping before it set
solid (perhaps 1.5 hours from delivery)

Cement re-hydradtion (ie setting) is a chemical reaction and thus very
dependent on the temp. When it starts to go off though it is
exothermic - ie gives off heat.


The heat given off can be an issue with bulk concrete (they
incorporated cooling pipes in the Hoover Dam), but it's extremely
likely to be detectable for mortar joints between bricks - there just
isn't enough of it!

(But the point about temperature dependance is /very/ relevant.)