How do you repair alkali silica reaction in concrete? I wish there was a simply solution to achieving that. I had a homeowner call and tell me she was having small modules of gel leaching out of the concrete, and over time the gel would harden. She had an engineer come out and take samples of the concrete, they determined that she had alkali silica reaction or (ASR).
So I went over to the house to take a look at the problem and was amazed by what I saw. Take a look for yourself:
Alkali Silica Reaction
I’m sure you can figure out why this might be a problem. For starters she has a decorative overlay in the house that is peeling off because of this reaction. She also has sticky gel all over her floor which makes it difficult to keep clean. She asked if there was any way to prevent the gel from re-appear.
I asked a couple of different suppliers and manufactures about what can be done to stop this. For the most part they all told me the concrete has to be jack hammered out and re-poured, which is not feasible because the house is already built and she is living in it. One person told me I can use a product called Aqua Block and that might help.
I told the homeowner I would not mind messing around with it seeing if anything will help the situation. I suggested to grind the concrete down where the ASR was happening, which happens to be where all of the structural beams are. After grinding the concrete I left one area untreated and another area I treated with Aqua Block to see if that will help at all. After a couple of months I will go back and check to see if their is any improvements. If anyone has any suggestions or questions on this issue please email me at firstname.lastname@example.org.
Spalling concrete can be a major issue in parking garages. Unlike concrete buildings that receive a curtain wall protecting the inside concrete floors from the weather, parking garages are open to the elements of the weather. Since the concrete parking decks are opened to the weather is it especially important to place the rebar in the correct locations and have enough concrete covering them.
A protective treatment that can be done to the parking deck after the concrete has been poured is to apply a waterproofing membrane to the concrete. This membrane will prevent water that is sitting on the concrete parking deck to leech into the concrete causing the rebar to corrode causing a spalled area. This membrane can be applied right after the concrete has cured or years after. This investment will protect the parking garage from future spalling problems that could potentially harm a pedestrian.
For more information please visit are website: http://mvlconcrete.com/concrete%20restoration%20-%20san%20antonio.htm
Concrete spalling is very common in parking garages. The spalling occurs when the rebar in the concrete starts to corrode due to water seeping into the concrete. As the rebar corrodes it expands causing a piece of the concrete to break off.
Overhead spalling concrete can be dangerous to occupants in the parking garage. Pieces of concrete could fall and hit someone causing a lawsuit. It is relatively easy to repair the spalling concrete in the parking garage if done sooner than later. When rebar corrodes it could spread causing bigger areas to spall off.
The pictures below is an example of an overhead piece of concrete spalling in a parking garage. We offer parking garage restoration services in San Antonio, TX.
The bottom concrete slab of this parking garage had many cracks that were between 1/4″ to 1/2″ wide. The cracks were left alone for many years allowing water to drain into them. Overtime the concrete slab started to sink because the water started to erode the sub-base.
To help prevent further erosion, we cleaned out the cracks with a saw blade and then filled them with a flexible sealant.
Stay tuned for more pictures in a couple of weeks of other parking garage repairs. We will next be repairing spalling concrete on the slab-on-grade.
A common area for spalling concrete is underneath exterior formed concrete stairs. The spalling is caused by water seeping into the concrete corroding the rebar. As the rust forms on the rebar it expands causing the concrete to break off.
To prevent this from happening, you should have the top surface of the concrete stairs waterproofed. Waterproofing concrete involves prepping the concrete and then troweling on a special waterproofing cement. This will help prevent water from soaking into the concrete corroding the rebar.
This week we prepared a mud-base for wood flooring. A mud-base is a cement-sand mixture that is fairly soft and brittle. The mud-base was placed because the home builder did not build the front entrance of the house higher than the outside patio, so to bring the floor up in the house they placed a mud-base and then tile.
During the tile removal the mud-base got chipped up in some areas as well. There were a lot of gouges in the mud-base that had to be filled and also leveled. The homeowner had two options he could either remove the 2 1/2″ of mud-base and place concrete or repair the mud-base for the wood floors.
They decided to repair the mud-base. To do this we had to coat the entire surface with an epoxy to make sure the mud-base would not break apart, the epoxy also helps the special repair mortars bond properly. After applying the repair mortar to fill all of the gouges we applied a self-leveling underlayment to finish off the repair.
Today we repaired a concrete column that was in pretty bad shape. The column was hit by a delivery truck backing into the loading dock. The edges of the concrete column were spalling off. We removed all of the loose concrete, applied a bonding agent, and then a repair mortar to finish the concrete repair.
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.
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.
The first thing you should do when you are about to repair concrete is to try and find out what is causing the damage. This will be either obvious or it will be hard to find out what is causing the damage. If you do not fully understand what is causing the damage, the concrete repair might fail.
Often times the concrete is damaged when it is being placed. Their might be to much water mixed in the concrete, or the concrete finishers added water to the surface when troweling. Excessive amounts of water in the concrete will cause the concrete to be weak, prone to erosion, cracking, porous, and not as abrasion resistant. You will often notice if you rub your hand on the surface of the concrete you till see a lot of dust on your hand.
Concrete that is spalling is often caused by the rebar not being embedded far enough in the concrete. If the rebar is to close to the surface, it is more prone to rusting causing the rebar to expand breaking the top piece of the concrete off. Spalled concrete is also caused by un-entrained air concrete that under goes freeze-thaw cycles; basically water will soak into the concrete and when it freezes it will expand causing the concrete to start breaking apart.
Another common cause that damages concrete is from tree roots. Concrete will start to crack and uplift when it is poured close to growing trees. The roots of the tree will start to uplift a section of the concrete and cause a tripping hazard that will need to be repaired.
These are the top reasons to why concrete gets damaged in residential areas. Once you have figured out what is causing the damage to the concrete, you can then start planning on repairing the concrete. How to repair concrete under these circumstances will be in another blog post.