How do I clean a pea gravel driveway?

by **semperfiguy** » September 19, 2011, 10:52 am

During this rainy season my brand new pea gravel driveway has started to look like all the other blackened/mildew looking concrete walls and structures in any typical village. Back in the States there are certain chemicals that one can buy that will make it look like new with little or no effort, but I have no idea how to buy those here. I have tried a mixture of clorox (chlorine bleach) and washing detergent, but it didn't phase it. I don't dare ask any of the sales clerks in the local hardware stores because they will tell me anything to get a sale, and from my experience they are totally unreliable. I would like to hear from someone who has first hand knowledge of a local chemical or process that actually works. Your comments/advice are very much appreciated in advance. Cheers!

by **trubrit** » September 19, 2011, 11:07 am

Not sure what you mean by pea gravel but I have just cleaned my concrete driveway by squeezing a couple of Duck toilet cleaning fluids over the wet surface and then using a pressure washer to shift it .Not hard work and under 100bht cost excluding electricity .

by **Shado** » September 19, 2011, 11:17 am

I use only the pressure sprayer to clean the "pebbled" driveway, sidewalks (foot paths) fence and just about any other concrete type surface. It works well with just the water pressure and no chemicals or detergents. 100 bar (1,450 psi) works just fine for me. My unit is a just a small one (Bosch Aquatak 100) but well worth the 3,000 baht investment.

After I cleaned the pebble drive way really well I applied a clear sealant over the surface. Can't say that it prevents the black mildew but it makes for quicker and easier cleaning.

by **semperfiguy** » September 19, 2011, 11:24 am

Shado wrote:I use only the pressure sprayer to clean the "pebbled" driveway, sidewalks (foot paths) fence and just about any other concrete type surface. It works well with just the water pressure and no chemicals or detergents. 100 bar (1,450 psi) works just fine for me. My unit is a just a small one (Bosch Aquatak 100) but well worth the 3,000 baht investment.

After I cleaned the pebble drive way really well I applied a clear sealant over the surface. Can't say that it prevents the black mildew but it makes for quicker and easier cleaning.

Shado, where did you buy the pressure washer?

by **Shado** » September 19, 2011, 12:32 pm

We got ours at HomePro, some time back. They were on sale at the time. Could be that they have specials on pressure washers on a regualar basis.

As you enter the store (left side, facing the building) immediately to your left is a big display of pressure washers. They will try to sell you a 120 or 130 bar machine but my experience is that 100 bars work just fine for our domestic applications.

by **douglas** » September 19, 2011, 2:02 pm

Hi,
Same as Shado. Pressure washer has a seperate lance with a bottle attached , and you fill it with cleaner. Works well on driveway etc. Bought in Homepro.
I've seen people use these to clean cars. I would not do this. If you have a chip in the paint it could lift the paint. Also be careful around the radiator, do not use directly on radiator.
Just been looking at our roof. The north side has a lot of black on the slates. I last cleaned it three years ago. Will have to do it when the rain stops.
Cheers Doug.

by **parrot** » September 19, 2011, 3:26 pm

I bought a pressure washer at Homepro as well.....4 years ago. Had it for a month or two and had a motor problem. They changed the motor and it's worked well since. Paid 4990 baht.

by **FrazeeDK** » September 19, 2011, 7:19 pm

what type of sealant did you use on your "hin tok" pea gravel walks, where did you buy it, and how much did it cost??

tks,....

Dave

by **Shado** » September 19, 2011, 8:07 pm

I'm sorry FrazeeDk but the wife got the sealant through someone who knew a hin tok driveway installer. I quizzed her on the name of the product and where it came from without any informative results. I'm trying to remember the name on the container but drawing a blank. I'll keep trying to find out but can't guarantee I'll be able to come up with anything. My neighbor sealed his driveway as well and I'll ask him if he remembers.

by **fdimike** » September 19, 2011, 9:55 pm

Be careful using sealants on finished concrete "sandwash" surfaces because the original installer may have used a sealer on it alraedy which may not be compatible with the new sealer. I have a "sandwashed" terrace/patio around the first floor of my house which I wanted to apply some sealer to. I purchased a waterbased sealant by Superchamp which stained the concrete very badly. I had the company come out to take a look at it and they wound up replacing the sand wash around the entire house at no cost to me. I then had them seal it with their product without a problem. I would recommend you wait for the dry season to arrive and pressure wash the surface to remove the mildew, let it dry thoroughly (no problem in the dry season) and then test the sealer on a small out of the way area to see if you develop and stains. The stains I had were white in color and stood out like a "sore thumb" on both light & dark surfaces. A number of companies (Bosny, Superchamp, Lanko etc) make water based concrete sealants which will help reduce the mildew problem because they will seal the concrete pores and prevent the mildew from getting deeply into the concrete. Global House & Home Pro have a very good selection.

BTW the chemical additive used to pressure clean concrete surfaces in the US is Trisodiiumphosphate (TSP)

by **arjay** » September 21, 2011, 10:22 am

To clean up sand wash/pebble dash paths I've used "nam grot" - which I believe translates as acid water (which contains about 35% HCL - Hydrchloric acid) - best diluted with water, and a stiff brush and hose off. If used too strong it can cause discolouration blotches.

To seal a recently laid area of coloured stones set in concrete, I first painted on a couple of coats of ordinary silicone based water proofing liquid, and then finished off with a coat of Acrylic Lacquer, namely - Lobster A100 - "Pure Clear Acrylic Finish Solvent Base". That worked well and looks good.

by **Khun Paul** » September 21, 2011, 3:00 pm

one could say take each individual stone and wash it and then relay it, or you could use many of the acidic detergents used by many, the downside is that some of the liquid may seep into the garden doing untold damage to flora and fauna.

me I wanted but decided against it hence I have no problems.

by **Mosquito** » September 21, 2011, 3:53 pm

Like the look of the gravel drive ways (only have concrete), so how much would it cost to pave a 25x12 meter area???

My concrete drive way has this dark green slime all over the place, have tried a few bottles of clorox/bleach with little or no effect.........will that Duck stuff work????

by **Drtierra** » September 21, 2011, 10:25 pm

I assume the gravel is imbedded in concete so the gravel is somewhat exposed.
Muratic acid is commonly used to clean this type of surface. TSP is just too weak. Muratic acid is used to clean swimming pools for example so a pool supply store may be able to help you. The acid can kill plants so care must be used when it is used.
Concrete contains rock, sand, cement & water. All rock & sand products contain salts. Those appear in the surfaces of concrete products as white or light colored discolorations. This will continue until all the salts are leached out of the concrete which can take a long time.
Sealing the surfaces with a product like Thompsons water seal will help but you must clean everything very well first. All such products are about the same & should be compatable. The application of this or any type of sealant can cause the surfaces to become slippery at least for awhile. There would need to be several applications done to have any chance of success. Even then it will be very difficult to stop the blackening of these surfaces over time. The key would be to provide excellent sub surface drainage along with the proper slope angles on the exposed areas. This is often not done due to cost.

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