Concrete efflorescence is a white powder that is is found on the concrete surface. It is caused by the water from underneath the concrete migrating up the slab, once it reaches the top, the water will evaporate and leave salt particles on the surface. The white efflorescence powder will be soft at first but eventually will turn hard.
Efflorescence On Concrete
If the efflorescence is left on the concrete for long periods of time it will eventually start to eat into the concrete leaving the concrete with a lot of divots and pits as you can see in the photo below. The concrete will then have to be repaired.
Concrete With Moisture Problems
There are two types of sealers we have used that have stopped efflorescence. One type is an epoxy vapor solve product that will basically seal off the concrete completely not allowing the water to escape. This product is best used if you are going to be putting another type of flooring on-top of the concrete that is not breathable such as laminate flooring, VCT, or wood. The epoxy coating can also be used if you want to clean up the look of the concrete if it is going to be left alone. Applying concrete coatings is best left to the professionals because of the proper surface profile needed for the coating to bond properly.
Concrete Epoxy Coating
The other type of sealer we have used is a cost affective DIY alternative to the epoxy vapor solve product. It is a penetrating sealer that will not change the look of the concrete and will still allow the water to pass through the slab. It is not used if you are trying to completely eliminate the moisture coming through the slab. This type of sealer will only stop the efflorescence from forming. It can be used on concrete and bricks. The concrete will need to be cleaned and all of the efflorescence removed from the surface before applying the sealer.
The pictures above are of a garage floor that had serious moisture problems. Water was seeping through the concrete pooling in the middle of the garage. Efflorescence was starting to form causing the concrete to pit. We were called to restore the concrete; we prepped the surface and then applied a tinted vapor solve epoxy system followed by a top coat of polyurethane.
Restoring concrete to its original look can be effectively and efficiently achieved by pressure washing the surface. Over time concrete will absorb oils, mildew will start to grow on the surface, and black grime will get imbedded into the pores. Pressure washing will remove these contaminants by using significant pressure to blast away the dirt and mildew.
When you are using a pressure washer to restore concrete, you must make sure the concrete will not get damaged when pressure washing. Concrete that is flaking or is weak will be etched by the pressure, this will create an unpleasant look. When the concrete is not in good condition to use a high PSI pressure washer, you must use detergents to restore the concrete.
Concrete spalling is often caused by improperly placing the rebar or wire mesh when pouring the concrete. If the rebar is to close to the top of the concrete slab, as water soaks into the concrete it will start to corrode the rebar. This will cause the rebar to expand, weakening the concrete above the piece of rebar.
If you look left of the blue line, you will notice there is a crack starting to form, this crack is right above a piece of rebar corroding. When we tap the concrete with a hammer we hear a hollow sound. To repair this we have to break out all the loose concrete, cut 90 degree edges, pressure wash & clean the rebar, and apply a non-shrink repair mortar.
Spalling Concrete Cause By Corroding Rebar
Right after we start to chip out the bad concrete a piece of rebar started to stick out. This was the main cause of the damaged concrete. It is very important to place rebar and wire mesh at the proper place when pouring concrete.
Spalled Concrete Area Chiseled Out
Concrete Resurfaced & Stained
After the concrete was chiseled out we applied Miracote RM 2 and then finished of the spalled concrete repair by resurfacing the area with Miracote MPC, and then applied a grey stain to match the bricks.
Stained concrete outside helps make the concrete more pleasing. It is one of the easiest DIY projects as the prep work and equipment needed to stain concrete is minimal. There are a few guidelines when prepping the concrete before staining:
Pressure washing will remove most stains from the concrete. Be careful not to hold the nozzle to close to the concrete or you will etch an unwanted pattern that will show up when finished staining and sealing the surface.
Oil stains can be faded with degreasers found at the hardware store. Be sure to thoroughly rinse the surface afterwards, because the degreasers will be very sudsy. The oil might not come out on the first try, a couple of tries might be needed. Some time you will be left with a shadow of where the oil stain was.
Hard water stains can be removed with CLR or similar products, but do not use if you are planning on staining the concrete with an acid stain. This will deplete some of the lime the acid stain works with to produce the color in the concrete. If you need to use CLR you will have to use a water or solvent based dye to stain the concrete.
For exterior surfaces that are very dirty and after trying the above steps still won’t come clean, the last resort would be to grind the concrete. You will need to rent a grinder from a rental place. This will take the top surface of the concrete off, so you will see some aggregate in the concrete.
Concrete restoring is a cost affective way to fix concrete without tearing out and re-pouring. Concrete can be restored anywhere there are problems; whether it is a concrete driveway, sidewalk, tilt-up walls, stucco walls, concrete walls, parking garages, curbs, and parking lots.
If you have any problems with your concrete such as: cracks in the concrete, concrete spalling, concrete discoloration, and concrete joints that are un-even; give us a call at (210) 422-6116 for a free consultation.
Cleaning concrete before acid staining is the most important step. You want to make sure there is nothing on the concrete that will prevent the acid stain from soaking in the concrete.
There are a few tools that you can use to help clean the concrete:
Detergent (nothing that contains acid)
The first thing we do when we clean concrete, is run the floor machine with detergent (typically dawn soap) over the whole surface to remove dry wall mud and any loose paint. This will help you see what is left on the concrete that needs to be removed.
If there is glue that is still on the floor, you might need to use a solvent such as xylene (make sure pilot flames are blown out) to remove it. If there is paint still on the floor, scrape as much of it of as you can, then go over the surface with xylene to remove any stubborn areas. If the whole surface of the concrete floor is painted, you will need to use a chemical stripper or grind the concrete. If you grind the concrete you will have to grind the whole area to make sure the surface texture is all the same. If the paint and glue remain on the concrete floor when acid staining, you will notice them.
After you have removed all the contaminants from the floor, use a mop with clean water to thoroughly clean the floor. Let the concrete completely dry out and then you are ready to acid stain the concrete.