Wander into any hardware store and you’ll see a whole shelf of products that claim to be the best concrete cleaner going. Most of them are okay for knocking off dirt on the family driveway, but there are a lot fewer that can actually handle a real construction site. And somehow, almost none of these marketing claims even get to the point, it’s not just about whether a product can get rid of concrete grime, but what happens to the dirty water it produces, and whether that water is going to be a problem when it goes into the storm drain on a site that’s got to sort of follow the rules.
Why Concrete Grime Is So Hard To Clean?
Concrete forms itself through some pretty chemical reactions, not just a bit of drying out. During the curing process, a bit of calcium silicate hydrate starts to form as the main bit that holds it all together. Once it’s all set and hard, this stuff is very stable, it doesn’t dissolve in water and won’t respond to the usual cleaning agents like it would if you were cleaning a messy bit of grease off a car. That’s a problem.
Also, concrete is really alkaline, the pH is somewhere between 11 and 12. That means that if you try and clean it with a product that just washes it off, the grime doesn’t just get stuck on (like if you try to clean a greasy pan with warm soapy water); it actually starts to react with the water and causes environmental problems if the dirty water flows off the site into the storm drains.
How much grime can actually penetrate into the surface depends on how porous the concrete is: if the concrete is old and weathered, or if it’s made of a type of stone that has lots of little holes in it, getting the grime off is going to be way harder than if it’s just a smooth, sealed surface.
There is a bit of a difference between trying to clean up grime on freshly poured concrete and grime that has had time to set hard. Grime that is still wet is a bit more workable, still a bit more chemically active. If it’s had time to dry out, you need to use a different product, and most domestic cleaning products just don’t have the grunt to get it done.
Acid Based Vs Non Acid, What Type Of Cleaner Are You After
The sort of products that professionals use to clean concrete divide into two groups: acid based and non-acid. Acid based ones usually contain something like hydrochloric acid or phosphoric acid, which chemically react with the grime and break the bonds that hold it to the surface. This can be a pretty effective way to get rid of it, but you have to be pretty careful: the acid needs to be handled properly, you need to wear safety gear, you can’t let it come into contact with anything else that it could damage… and then you have to make sure the water you wash with is neutralised before you can just hose it down the drain. Sounds simple, but it needs to be done right.
Non-acid products vary a lot in how well they actually work, but the concept is a bit more vague than acid based products. Some of them use special chemicals that grab onto the calcium in the grime and lift it off; others use chemicals that break down the grime in a different way. But unfortunately, these cleaners are often marketed in a pretty vague way, it’s all about being eco-friendly rather than actually explaining what they do. So when you’re choosing between non-acid cleaners, you have to try to figure out what sort of chemistry is going on underneath the marketing fluff, rather than just trusting the “greenwashing”.
The Compliance Factor That Makes All The Difference
NSW EPA has pointed out the requirements concerning site waste of the construction sector, noting that this industry creates significant amounts of materials, which represent a danger to the environment if mismanaged. EPA Victoria has developed a general environmental duty which binds all people whose activity creates a risk to the pollution of waterways. This environmental duty applies to contractors who create wastewater from cleaning concrete.
The selected cleaning product determines what kind of wastewater is created, and how it should be managed:
- The acidic washdown water from hydrochloric acid-based cleaning cannot be disposed into stormwater or soil without pH adjustment; the created liquid is considered the regulated waste in many council areas.
- There are some cleaning products which contain chemicals accelerating the process of solids settling; it simplifies the management of the wastewater on-site as the amount of the liquid which needs to be treated before disposal is reduced.
- For regulated commercial sites, the documentation of the disposal of the chemical cleaning wastewater is increasingly required in the form of environmental management plan.
The product which allows to remove the residues effectively but creates the wastewater which cannot be legally disposed without treatment is not a good concrete cleaner despite its performance on the stains.
Product Selection Based On Surface And Job Type
The cleaning of the residential driveway and diamond grinding operation on a commercial site represent the tasks which are performed on different surfaces with different residues and require different approach to the product selection.
The polished and exposed aggregate concrete surfaces react adversely to acid chemistry; unprotected contact leads to permanent alteration of the surface finish. The equipment washdown on the yard requires the cleaning of the accumulated residues on the mixed substrate conditions. The cleaning of pavers requires the product which will be able to clean both types of residues: the organic growth and efflorescence of concrete.
The suitable product for the particular task depends on the combination of the surface type, residue type, disposal restrictions, and competence of the operator. Selection based on price alone and the assumption about the equal performance of the products labelled as concrete cleaners will result in non-compliance on sites where the documentation of the approach to the waste management is necessary.