Removing Stains from Fertilizer on Patio Slabs

Hi,
Unfortunately I got some fertilizer on the patio paving slabs and it has left these orange iron rust marks everywhere.
As I ended up walking in the fertilizer and in turn onto the patio, it is in a good few spots :(

Google tells me to try some lemon juice and scrub hard, which I did on a couple of spots to test. It definitely seems to reduce the stain but not fully remove it. Maybe I need to give it a second dose of lemon juice or scrub harder. I was using a kitchen pot brush that you would use for cleaning dishes to scrub.

Has anybody any first hand experience of a remedy that did work? I dont mind putting in a lot of physical effort if it will work

Pics below showing the stains.

Thanks

 

I'm not fully sure, when I google it, I see a few different things. It is a custom build slab made for the builder who built the estate.

The name is Kilsaran Newgrange Autumn Oyster. I managed to get sticker off the slabs the builder used,see pic.

The below link seems to say it is:

• Natural Aggregrate Paving
• Lightly textured surface finish using premium granite aggregrates.

Newgrange Autumn Oyster - Hardscape | Commercial Stone & Paving

 

Hi,

The manufacturer has quite a few information sheets on that product, but not seen anything relating to cleaning, though you could ask them what they recommend .




Lots of products out there for cleaning concrete slabs plus many diy solutions such as white vinegar/ cider vinergar and lemon juice etc.
However think it really depends on what parts of the fertilizer caused the stain as to what treatment will best remove it.
Wonder if the orange stain was from a lawn weed and feed / moss killer that contained Iron ?

Have you tried a Pressure Washer ?

The only catch in such cleaning methods is that your 'cleaned' area may stand out from the rest of the flags !

 

Thank you for your reply.
Is it definitely concrete the slab or a concrete/granite mix? To me it is not fully clear.

Below is a link to the lawn sand that was used, and due to walking in it and in turn walking on the patio it has I think left a lot of the marks.

Westland Lawn Sand | Lawn Care | Westland Garden Health

I have not tried with the pressure washer yet but already from using the lemon juice and scrubbing, it 1) hasnt fully removed the stain & 2) it has left the "cleaned" area a lighter shade which nearly looks like I have taken a top layer off the granite.

As the marks are throughout the patio, I need to be careful what I do next.

Do I get a yard brush and spray lemon juice on every slab and brush hard with the brush and try do it en masse.

I came across this product,but it will probably do similar and make the cleaned part stand out more.

Stontex Rust Off 1L

 

Your Granite is just the aggregate/gravel part of the concrete mix and its likely its the more porus sand and cement part of the slab that have stained rather than the hard granite.

As you will have seen on that Stontex sites video, its still needs a good bit of work to remove any stains and you need to check how garden/plant/grass friendly it is when washed away or you might worsen the effect !

Have no experience of using such products, perhaps someone else who has used them might reply.

You could try a small test patch using some neat household toilet bleach and a scrubbing brush, though you need to be very careful for yourself and the surrounding soil /plants when using.

The other option is to just leave it overwinter and see if the rains and frosts help weather it away ?

 

Likely that your lawn treatment contained ferrous sulphate which is highly water soluble. It will dissipate once we get prolonged rain.

 

Thank you.
What is the thinking behind the toilet bleach idea? Have you seen it work before?

I'm beginning to think maybe leaving it over the Winter is the best option and see what it looks like come next March/April.

See pic showing impact of applying lemon juice and scrubbing on patio slab. Pretty obvious.

 

Thank you, it seems the lawn sand did contain ferrous sulphate, so if as you said it is highly water soluble then maybe the rain will help which ties in with another suggestion from another user to just leave it for a few months.

However, in my quest to understand what had happened I have now found out more info and it seems there may be an additional issue at play.

Originally, I removed a relatively newly planted tree from the garden and to backfill the hole I used a mix of lawn sand and topsoil. I trampled all over the hole to flatten it, I then proceeded to walk onto the patio and presumably the lawn sand was on the bottom of my boots and hence left foot like marks throughout the patio which when washed down after made the orange stains appear in the days after. It is pretty obvious what these stains were.

I have now found out in the last hour from the other half, that while we were away last week, a family member of hers came in and cut the grass which is fine and we asked to do, but they also decided to add a lawn feed I had purchased but not gotten around to using but was left with the gardening stuff in the house while we awaited delivery of a shed.
This was a pellet based garden feed and from speaking with him just now he spread it throughout the lawn, which is maybe why I am also seeing random speckle spot bits of rust that look different to the larger footprint marks also on the patio.

This has gone from bad to worse.

 

This is a link to the Hardscape cleaning and maintenance info (pdf) https://hardscape.co.uk/wp-content/uploads/2023/02/Concrete-Maintenance-V4.pdf
While ferrous sulfate is water soluble, it quickly oxidises to ferric sulfate and ferric oxide which is brown and insoluble.
I'm not sure I would use toilet bleach, best bet is lemon juice or citric acid (as used in wine making) and a brush, pressure washing is not recommended for these slabs.
The cleaner patch will probably even out over winter.

 

Did say to just try a "small test patch" with bleach to see if it by chance removes the stains as NG20 had tried lemon juice with little effect.

That set our alarm bells ringing, assume you mean it was Westland lawn sand bag you used ?
If so putting such a large amount of fertiliser and moss killer in a small hole will probably adversely affect anything you plant in that now full hole for many months, possibly any nearby plants as well.

You might have been better using an Autumn Feed and Moss killer this time of year as the one you used is high in Nitrogen, more intended for Spring when the grass is starting to grow and needs that boost.

 

As you can see from my username I am very novicey and am learning from my mistakes. :D

To backfill the hole, I mainly used the soil I removed in the first place to get at the trees root. As I put some of the soil from the garden in with the tree, there was a balance of the hole to be backfilled.
I used a combination of westland lawn sand and westland top soil, probably a 40:60 mix, in favour of the top soil to backfill the hole.

I read elsewhere on the internet about using lawn sand and topsoil to backfill a hole, what I didnt know, was that there was fertilizer in the lawn sand, I just presumed it was sand used specifially for lawns. Only when I noticed the footmarks and orange/brown patches on the patio, did I look at what was in the lawn sand and put 2&2 together.

The hole is probably 90% covered by a new garden shed, which was the reason for removing the tree in the first place and has caused all these problems.

I presume the grass the other side of the hole should not be too adversly impacted by what I put in the hole?

Thanks

 

Unless the staining is really bad I'd just leave it and see if it weathers out over the winter.
Pretty sure over the years you will get other types of staining, it all evens out in the end.

 

Thank you.

The thing is, if I try to reduce the orange patches throughout the patio, I am going to have a substantial amount of "cleaner patches", due to the amount of orange patches.

Do I take the risk of giving the majority of the slabs a clean with a yard brush and lemon juice and have a load of clean patches and hope they even out.

To save on squeezing a load of lemons would the below lemon juice which seems to have some sort of lemon oil added, do the trick?

I can also see about the white vinegar option, could only see white wine vinegar in the shops earlier.

https://www.tesco.ie/groceries/en-IE/products/250428970

 

Thanks, it is maybe more that I am only in the house 3 months and the patio was as clean as a whistle before I messed up, so hard to look at it now.
The spread of orange marks is pretty wide tbh, it doesnt help that the slab is a light colour.

Another vote saying to see how it fairs out over the Winter.

 

Lemon juice is basically citric acid I think.
Its probably just some kind of acid cleaner you need if the lemon juice is working.