Protecting concrete against slime

[MisterBoy]

The warm, wet weather seems to have really made this a worse problem in 2020 - normally I pressure wash our yard after the winter but already it is covered in some sort of algae. It looks merely a bit dirty but the moment it's damp, it is incredibly slippery, to the point of being pretty dangerous.

Pressure-washing is not a quick job so is there anything I should be doing to make it last longer? Stuff to add in while washing, or treat with afterwards?
With this week being so ridiculously wet I thought I might get on with it.

 

[JohnD]

"Wet and Forget" is a chemical soap.

 

[MisterBoy]

Cheers @JohnD I'll take a look. Would it be worth pressure washing to get a clean surface now it's built up, then start treating periodically? Or just apply this and see what happens afterwards - if all the slime disperses once it's dead?

 

[JohnD]

if you want, but I believe their minimum order is 5 litres, which dilutes, so you may as well buy it and water it on to kill the stuff before washing it. When dry and clean, water on some more to impregnate the surface.

 

[MisterBoy]

Makes sense. I'll have to check if I can use my washer to spray it - it has a car-cleaning gadget so maybe. Otherwise I'll have to use the backpack sprayer I guess

Thanks.

 

[JohnD]

Or a watering-can.

 

[dontbelieveawordofit]

hypochlorite cleaner .

 

[StephenOak]

"Wet and Forget" is a chemical soap.

Hmm, sort of, but only sort of.

In Wet & Forget (& Patio Magic which is another similar product) the active ingredient is benzalkonium chloride (confusingly also called alkyl dimethyl benzyl ammonium chloride).

This has many uses including some soaps, hand sanitisers, etc, but also as a preservative and in catalysing some chemical processes. The relevant use here is as a biocide.

In W&F/PM it is at, IIRC, 7% and you dilute it down to 1-2% for use.

I need to remove moss from my (N facing) front yard every year so I bought 5L of 50% benzalkonium chloride 5+ years ago.