Stains on patio

[munchie]

Hi All,

Having just laid a patio with concrete slabs, i have noticed that some are stained with sand (sharp sand that i used to bed them with) I have tried scrubbing them down with soapy water, i even tried bleach but the stains still remain.
I'm disappointed to say the least, it has taken me ages to lay these (on my own ).

Any help please???

[RAPressureWashing]

Can you post or email me a photo?

[munchie]

OK, it seems once the slabs dried the stains almost disappeared, but now am left with mortar stains where i used a dry mix to do the joints, i soon as i swept it in i could see the moisture rising between the slabs and now am left with horrible marks.
Advice please anyone, i'm so disappointed after all my hard work at laying it

[lutonlagerlout]

i soon as i swept it in

where did you get this masterplan munchi?
i dont think anywhere on this site does it advocate "brushing in a dry mortar"
sounds like cement staining,hydrochloric acid will remove but may etch the slabs
LLL

[munchie]

Pardon me for being stupid but ......

The 4:1 mortar mixture is mixed dry - no water is added at all, and it is essential that the sands and cement are thoroughly mixed together in the dry state before scattering onto the dry paving surface, and then using a soft brush to sweep the mix into the joints. Once an area has been covered, every joint is forcibly struck with the edge of a trowel to pack down the dry mix into the joints, and the process is repeated as required. Sweeping at an angle of 45° to the direction of the paving joints prevents the mix from being swept out of the joint. All surplus mix should be swept off and disposed, it can be re-used to seal other areas, if required, as, unlike the wet grout above, the cement content has not been wetted and is therefore still relatively fresh.

[lutonlagerlout]

oops apologies,
i would never advocate a dry mix personally
tends to fail real fast
LLL

[seanandruby]

maybe there was too much water laying in the joints so that you brushed the wet stuff around the edges but didnt finish with a soft broom and left some fine mix to stain.

[munchie]

Hi sean,

Yes i think ur right, i think i was a little too impatient when i did my grouting and there was too much moisture still in the gaps..
And at the moment here its pouring with rain so not much i can do today out there.

[Tony McC]

There's something missing from that quote...

Left to its own devices, dry brushing-in rarely creates a well-filled, structurally competent joint. The resultant mortar is often a crumbly, friable gap filler that has a very limited lifespan and usually offers an excellent home to all sorts of weeds. This is of little consequence to the less reputable installer, as they will be long gone and the money spent by the time problems start to become apparent.

...taken from the page that explains why dry grouting is not recommended.

[lutonlagerlout]

aha ! every time i see lads sweeping in dry sand and cement , i can hear spurs clinking and horse neighing in the background :;):
LLL

[GB_Groundworks]

i did some work at my sisters house few years ago and the old boy next door kept coming and watching me telling me about he'd been a flagger all his life etc......

then started telling me i was putting the indian stone upside down. he wanted the the widest part of the joint to the top and then when i was sat for a day pointing them up he was telling me i should just use a dry mix and sweep it in.

i humored him but ignored him a lot of people believe that if they have been doing something for a few years then that is the way it has to be done.

[Tony McC]

Back seat builders - when pricing-up, I automatically add 25% to the cost of a job because of all the bollocks and bullshit you'll have to put up with while doing a proper job for them.