Indian sandstone cement stains - Cleaning with sandpaper?

[worldofpaving]

I worked out the price per litre from the 5 gallon pail price, they show a small spray bottle on the site but don't actually list the price for it.

My understanding is that it is an alternative to the use of acid, e.g. hydrochloric, etc., the presence of some lemon juice in the formulation does not classify the finished product as "acid".

There would be no problems shipping this product internationally from a regs standpoint, whether they want to or not, is, of course, another question.

The product that MSH saw at SED sounds interesting.

Anyway, hope the OP sorts his paving out ok, I see no reason to wait 6 weeks to powerwash, in hot weather like we have been having, it should be fine after 2 weeks.

Best,
WOP

Best,
WOP

[msh paving]

[quote="R&A Pressure Washing"]I would wait for at least 6 weeks before pressure washing.

in this heat the cement will not reach full strength in 2 weeks,as R+A says leave for 6 weeks,he is a expert in the pressure washing field no doubt he has good reason to make this point,when doing concrete test cubes you wait 28 days to reach strength so why will pointing 30mm deep be full strength in 14 days
the chances of masking the pointing from a pressure washer are pretty slim MSH



Edited By msh paving on 1246830475

[James27]

Thanks for all your help guys. I'll give it a few weeks then as i dont want to wash out the joints, i dont think my back could take another pointing session so soon! Will just have to wait and maybe some of it will weather away by the time it comes round to pressure washing. Its annoying though when you finish the jobs and theres unsightly stains on! Oh well cant be helped i suppose! Will let you know when i hear (if i hear!) back about the cement dissolver!

[RAPressureWashing]

The reason I said 6 weeks is as following,
The pressure and water flow of the machines we use, is much higher then what most home owners would ever use, but saying that the problem with lower psi & water flow rates is people think that by getting closer to the surface they are cleaning quicker etc.
The average machine bought at any of the DIY sheds is ok for general cleaning, but on something like this there is always the temptation to get closer to the surface with your lance and this is where damage can occur. Most Karchers, Alto etc have at best a varilance which is either to wide or to narrow a spray patten or people use a "Dirt Blaster" and again get to close and stay in one place on a surface and either etch or start blowing out their pointing. So if agreed that after 6 weeks the pointing should be "Rock Solid" then what is the problem waiting till 6 weeks as passed.

Re the Citric, not sure if this will move the concrete staining, I use KG's of the stuff each year as a wood brightner and it does remove rust stains in some cases. The prices of Citric acid in powder form have rocketed this year, £68 per 25 KG bag. I have used Citric on sandstone before and had no problems, but as I said we use it as a wood brightner and it can stain some paving surfaces if left on the surface to long.

You could try Tensid, they do a product called Safety Klean which is OK on sandstone, if you give them a call and speak to Richard Turk he should send you a sample, here is their web site. www.tensid.com
Feel free to mention my name to him.

[GB_Groundworks]

i've not read all the post but have cleaned some mortar blobs off indain sandstone with a wire brush wheel and an electric drill. should be said these were out of the way (on top of a wall) and i was being picky haha but got it off with a light brush and a bit of water. wouldn't want to use it on a main patio slab for fear of altering texture/light reflection.

[James27]

You could try Tensid, they do a product called Safety Klean which is OK on sandstone, if you give them a call and speak to Richard Turk he should send you a sample, here is their web site. www.tensid.com
Feel free to mention my name to him.

just read some info on the website, sounds like a good product. I'll give him a call tomorrow.

[Tony McC]

David Burton at SteinTec UK is bringing in some German cleaning products and he has summat that removes cement film from vulnerable stone. Not sure how well it would work on heavier staining but David is a very amenable fellow and would give you good advice if you give him a call.

[James27]

Sounds good Tony, could be just what i need!

[worldofpaving]

MSH,

Just to clarify the question of strength development of OP cements.

In the old days, the 2/3 rule used to apply - 3 day strengths were 2/3 of 7 day strengths and 7 day strengths were 2/3 of 28 day.
These days, especially in hot weather, you would say it's around 9/10ths, particularly if pure cement is involved - almost all ready mix concrete mixes going out these days have a percentage of cement replacement and this can retard strength development a little.

This is mainly due to advancements in manufacturing technology, cements are much finer than they used to be and so hydrate better, also much more gypsum is used than used to be the case.

So, the answer to the question is that for a strong mix mortar, 3 to 1 or 4 to 1, in 14 days in hot weather it will have achieved a strength of about 40 nmm2 and should be fine for pressure washing.

I am in no way questioning Rand A's expertise in presure washing, the question is about cement and concrete technology where I have some expertise.

[Davesmate]

Hi there you might do well to talk to Dave or Gary at www.nccstreetscape.co.uk and avoid all of these cement staining and shrinkage / cracking problems by using their GftK mortars - Also they are used to getting new customers who have similar experience and problems to yours - So they also have a huge range of different stain removing solutions for everything from cement to oil to chewing gum - even for delicate sandstone or other stone surfaces -tel 01257 266696