Browse Forums Paving & Concreting 1 Aug 30, 2010 7:45 pm Hi all
We've been in our house for just over 12 months and over the past few months I've noticed a white dusty substance along an almost straight line about 3 or 4 cm inside the garage door. The line runs the width of the garage door along the garage floor. I've washed it away as well as swept it but it keeps coming back. Only recently, I've had a closer look and noticed that the actual concrete surface seems to have been eaten away along the white line. In some sections, I can see the aggregate. I called the builder last week and he arranged for the concrete supplier to give me a call. The concrete supplier came out today and I spoke to him on the phone. He said he took some pictures and will show it to the tech people at his company for comment. He will also check the documentation to see what make up the concrete was when it was delivered. I asked about how to rectify what is causing it or to fix it and he said he will see what it is first and then we'll see how to address it. As far as I could make out, he did not seem to know what had caused it. He only said that it appeared to be "dusting". Has anyone else come accross this before or offer any advice? Here are some pics.
Re: Concrete slab "Dusting" and erosion? 2Aug 30, 2010 8:32 pm This is a complete stab in the dark but could it perhaps be acid? If your bricks were cleaned with an hydrochloric acid wash, the solution could have accumulated here just under the garage door, and never got hosed away or neutralized. I would have thought you would have seen evidence earlier. Hopefully someone else may have an idea. Re: Concrete slab "Dusting" and erosion? 3Aug 30, 2010 8:51 pm looks like efflorecense, easy to treat goto a paving supplier and buy anti-eff, follow instructions to a t. in terms of eating concrete away havnt seen eflo eat normal concrete before. what for tech to have a look may not be eflo but it looks like it Da Vinci Outdoor Living Architectural landscaping http://www.davincioutdoor.com Re: Concrete slab "Dusting" and erosion? 4Aug 30, 2010 9:38 pm I don't think it's acid as the bricks were cleaned way before the garage door got installed. Besides, this is the only spot on the whole slab and it's really only become apparent in the last few months, about 20 months since slab was poured and 16 months after bricks were cleaned. The concrete guy said they'd get back to me by the end of the week so we'll see. I'm really concerned that it's going to be a structural problem as well as the fact that it looks pretty crap. Any other thoughts are much appreciated. Re: Concrete slab "Dusting" and erosion? 6Aug 30, 2010 10:13 pm Efflo" Yes Also free lime. If you damp it, the powdery 'stuff' will disappear ...also if you rub it it will breakdown. It is possible the finishing process water was used to 'close the surface'.. as would be the case. Nothing to worry about. Where you are coming from is where you are going to... Re: Concrete slab "Dusting" and erosion? 8Aug 31, 2010 8:14 am Thanks Onc, but what about the surface damage? Can it be repaired? It looks pretty ******* as the rest of the garage floor is nice and smooth. Also, will it stop happening over time or is it something we're going to have to live with? Thanks again Em Re: Concrete slab "Dusting" and erosion? 9Aug 31, 2010 10:25 pm So does the white stuff disappear when you wipe it with a damp cloth? Where you are coming from is where you are going to... Re: Concrete slab "Dusting" and erosion? 10Sep 01, 2010 9:21 am Hi Onc, yes the powder does dissappear when wiped with a damp cloth, but I'm still concerned about the concrete being eaten away. Have you come accross this before? Re: Concrete slab "Dusting" and erosion? 11Sep 01, 2010 5:55 pm A better idea might be to find the source of the water that the concrete is sitting in. The edge of the slab dries out more quickly(more air movement at the door, possibly more sun light) and is where the 'cotton wool' is forming( a symptom of drying concrete/brick/rammed earth etc) It may just be a matter of time before the concrete stabilizes and any other earth works ie paths and driveways if not already complete may change things. I don't think it is an issue for now, next season if you have a similar result then I would investigate down pipes, drainage, falls etc because somewhere nearby there will be pooling water. Where you are coming from is where you are going to... Re: Concrete slab "Dusting" and erosion? 12Sep 01, 2010 8:25 pm As all of our pathways and driveway has been in for more than 12 months already, the only thing I can think of is the join between the slab and the driveway. Could water running down the front of the garage door and seeping into that join cause this? It's a pretty tight join though as you can see in the photos. Onc, can you provide any advice on the concrete being eaten away? This is what I'm more concerned about. Thanks Em Re: Concrete slab "Dusting" and erosion? 13Sep 02, 2010 12:56 pm Just heard from concrete supplier. They say that concrete was to spec and the efflor is caused by water. Referred back to builder. I then spoke to builder who says that it's being caused by water seeping in under garage door during rain and drying along that line. I'm not really buying this as everyone has a garage door and why is mine the only one that's causing efflo? It's got to be something from underneath. Anyways, I've been told that it's my issue and they're not going to cover the fix. Any further suggestions regarding the concrete being eaten away would be great. thanks Re: Concrete slab "Dusting" and erosion? 14Sep 05, 2010 3:46 pm Hi, You have hit the nail on the head, it is water migrating/wicking through your slab drawing salt up with it, and depositing it on top, it is either from the joint or from underneath if the membrane has been damaged, or is simply not there. My advice is to contact a reputable salt damp expert in your area and get it sorted out sooner than later, this isn't called concrete cancer for no reason. They will probably drill into the slab and force sillicone based waterproofer into the area to stop the migration of the water. Hope this helps. Re: Concrete slab "Dusting" and erosion? 15Jul 05, 2012 9:23 pm Hi I am having the same problem. I have only been in my house three yrs after building. Only appears during the cold and wet weather..winter. Had builder out also and they said its nothing to worry about..Yeah right I thought. Im going to get them to come back out and have another look. I had my garage floor painted when it was built and now since the paint has lifted and the substances is now visible. God hope its not concrete cancer... Re: Concrete slab "Dusting" and erosion? 16Jul 06, 2012 1:59 am Nope just moisture coming through your slab hydrostatically , powder is effloresence just salts in the concrete . NOT much you can do since you have already painted your floors > Drilling a hole in the slab isnt going to do jack , if you have a failure/tear/hole in your DPC anywhere the water is going migrate through the concrete anywhere it choose but mostly in a crack . Sounds like you will need to treat the slab with a internal moisture barrier if you are wanting a topical paint . I would also check around the side of the garage and see if there are any cracks in your block work . I doubt very much it will be concrete cancer but if you see rust stains or colour then your in trouble . The concreter will take and reuse. In my case I bought structural LVLs and scraped them back and used them as joists. 1 5150 yep, clearly mark where the infloor heating pipes are before drilling or nailing 1 6056 Building Standards; Getting It Right! is this for a residential dwelling or a shed? If its for a dwelling, its out of tolerance and a "mistakes happen" isnt a good enough excuse to just move on. 1 2406 |