Definition – the pressure exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity. Hydrostatic pressure increases in proportion to depth measured from the surface because of the increasing weight of fluid exerting downward force from above. Hydro=water; Static=not moving

Where does it come from?

Hydrostatic pressure can be caused from: rain running off a roof and draining toward a house, a high water table and/or a faulty gutter system; sometimes it can also happen because of wind-whipped rain.

Hydrostatic pressure describes when water is actually being pushed through the concrete slab. It is actually a very rare problem, but the term has been used inadvertently to describe all water problems. Only the section of concrete that is below-grade can experience hydrostatic pressure.

Many concrete floors with hydrostatic pressure issues are not good candidates for secondary floor coverings. Carpet will remain damp and become musty or the glue that holds vinyl and other flooring options will let loose. What is the solution for such a problem?

Polished Concrete is the solution. When a floor is mechanically polished, there are no additional topical sealers or coverings that are inhibiting the moisture to come out of the slab thus allowing the floor to continue to breathe. Even though a densifier/hardener is applied to the slab, this sealer soaks into the concrete and the reaction takes place at a molecular level so this process doesn’t have any effect on the concrete slabs’ ability to mitigate moisture. In most cases, polished concrete is the only solution for a high rate of moisture through the slab, but it isn’t a bad thing. Take a look at the picture below that had hydrostatic pressure going on in the slab that we polished. They still look great and you’d never know that there was a major problem with this floor at one time.



Concrete patio before Siloxane sealer

Let’s make sure we’re all on the same page here. Concrete is a very durable, strong and long-lasting material which is why it’s used in foundations of buildings, as roads and driveways, and as floors, patios, etc.  However, after years of exposure to the elements and disuse, concrete will break apart and crumble, leaving evidence of its form, but no longer standing or whole. Don’t want the Grand Canyon running through your driveway or patio? How do you prevent it from getting chipped, broken, pitted or cracked? It’s not rocket science! In fact, breathe easy, it’s really quite simple! Seal it.

Concrete patio after Siloxane sealer

Proper care and maintenance of concrete involves sealing it. Concrete surfaces are susceptible to water because it is a porous surface which allows water to move in and out of it. This movement of water coupled with fluctuating hot and cold weather can weaken the integrity of the concrete. Other things can mar the appearance and composition of your concrete such as: oil spills or other engine liquids used in vehicles that may drip or leak onto a concrete driveway, spills of paint, stain or other products used in the upkeep of the exterior of your home or business, dirt accumulation and regular traffic on your concrete. Sealing concrete protects it and extends its life. I think of it as similar to taking care of your vehicle’s appearance – washing it, to clean off the dirt and road salts and other corrosive elements it is exposed to from driving it around, and then applying a wax to protect and preserve the color from fading and to repel the dirt and grime from the road for awhile. Who wants to drive around in a rust bucket? To keep your concrete intact and looking good you need to treat it the same way by sealing it.

Pool deck before sealer and dye

Sealers are either topical or penetrating sealers. As you might guess, a topical sealer sits on top of your concrete, usually by forming a thin film that acts as a barrier between the outside elements and the actual concrete; a penetrating sealer actually permeates into the concrete and is virtually invisible when dry. Topical sealers can be either solvent-based or water-based and are used to protect and enhance the appearance of stained, stamped or other decorative concrete, more often used indoors; while penetrating sealers are typically used on exterior or non-decorative concrete, especially since they don’t create a film on top of the concrete that may add to the slipperiness of the concrete. Types of topical sealers include acrylic, polyurethane and epoxy.

• An acrylic sealer can be used when economy and easy application are necessary, either on an interior or exterior surface. It is a UV resistant, non-yellowing, protection against water and chloride intrusions that also allows for moisture in the slab to escape. Acrylic sealers, when applied, generally dry to the touch within an hour. Because acrylic is a thinner sealer, it wears faster than other sealers and will require reapplication sooner.

• A polyurethane sealer has a protective film that is about twice as thick as an acrylic sealer and offers excellent resistance to abrasion and chemicals. Polyurethane comes in a range of sheens from high gloss to matte, is transparent, non-yellowing and highly durable. They are, however, moisture intolerant until properly cured. This means that upon application, if it comes in contact with moisture or water, it will create a chemical reaction that results in foaming and bubbling of the sealer. Polyurethane also does not allow moisture vapor in the concrete to evaporate out, which could cause problems in an outdoor concrete surface, i.e. a driveway or patio.

• Epoxy sealers are protective films that are hard, long-wearing, and abrasive-resistant. They are very good at repelling water and are much harder than acrylics. Most epoxies are glossy and can be clear or pigmented. Water-based epoxies bond well to concrete and provide a clear finish, but are nonporous and do not allow trapped moisture to escape. Epoxies are generally suitable for interior use because they are susceptible to yellowing with UV exposure.

A penetrating sealer is invisible protection that penetrates into the concrete to form a chemical barrier that shields against moisture penetration and de-icing chemicals. They are breathable, meaning they allow moisture vapor to escape, and are commonly used outdoors because of the excellent protection they provide against harsh exposure conditions, e.g. corrosion and freeze-thaw damage. Some common penetrating sealers are: silanes, siloxanes and silicates. These are good for use on driveways, patios, sidewalks, pool decks and other exterior concrete surfaces.

Pool deck after sealer and dye

With simply a little care and maintenance by sealing and protecting your concrete, you will be able to enjoy it for years to come!

It has been known to happen after removing VCT from a concrete slab and then grinding and polishing the floor for a new finish, sometimes the lines from where the tile was placed reappear in the concrete. This effect is referred to as “ghosting” in polishing terms. These marks can occur from within or beneath the concrete slab, or from treatments that have been used on top of the VCT. A concrete slab will always try to maintain moisture equilibrium, or in other words it will always try to balance the amount of moisture throughout the slab at all times. Because of this state of equilibrium, if there is more moisture either above or below the concrete slab, it will disperse or diffuse through the slab to reach the drier area. This diffusion leaves behind whatever minerals are in the water or moisture and can appear as a stain on the concrete after you remove the VCT. Ghosting can also be caused by a reaction between the adhesive used to apply the VCT and the concrete.

So what does all this mean for you? First of all, it is essential to remember that every concrete slab is as individual as a fingerprint. Every concrete slab has different characteristics that may affect how it performs as a finished floor. Every finished concrete floor is going to have a slightly different look to it than the next. When it comes to VCT and the ghosting effect, the result may just depend on how the ghosting elements were caused. If the marks were caused from surface issues, they may be able to be ground out to minimize or eliminate the tile shadows. However, if the marks were caused from moisture traveling up through the slab from below, no matter how much you grind the floor the marks will not be removed because they are through the entire thickness of the slab.
Here is an example of what ghosting could look like from a job CTI did in a church in Willmar, MN. You can see the marks where the tile had been, it appears like a grid on the floor. If this look is not what you want, there are a few options to try.

• You may be able to make the lines less visible by adding a dye or stain to the concrete floor. This will not make them go away, but will just disguise them slightly.
• If you absolutely don’t want to see the ghosting pattern, then you will need to look at a flooring option that will cover them up, such as a decorative overlay or coating applied to the floor.

Now that school is back in session, it kind of signifies the end of summer. Even though the days are warm, the nights start cooling off. The vegetation begins its slow decent into winter mode and before we know it, the snow will be flying. During the winter months we will have to deal with the daily battle of just walking. Ice and snow builds up on concrete and just about that time, you wish you could just hover over it to get to your car or your destination.

Allow me to introduce a product called Safelane Anti-Icing System. Although this won’t pick you up and carry you to your destination, your areas in front of your buildings and sidewalks will remain free of ice and snow buildup. Safelane is an overlay system that has a very special aggregate broadcasted into it that will trap the de-icing chemicals and slowly release it with time. For the month of September, CTI is running a special on this anti-icing system. During this month, any project booked will get a discount of 30% off of the retail price. We can only run this for the month of September because by the time October rolls around, it will be to cold to install it. Give us a call to further discuss your project with us.

1. Pressure wash – If you pressure wash the surface, it will wash all remaining residue and dirt allowing for a clean surface to apply your sealer of choice.

2. Sealer – Many home stores such as home depot, lowes, menards, etc sell concrete sealers. There are 2 types of sealer you can apply after pressure washing the concrete. A penetrating sealer or a topical sealer. Both sealers will work in your situation but its important to know what you are putting down because that will make a difference on how often you need to re-apply it. A penetrating sealer will penetrate into the concrete and should be re-applied every 3-5 years. A topical sealer is a film forming sealer on the surface and should be re-applied every 1-2 years. For flat gray concrete, I would recommend a penetrating sealer and for stamped concrete, I would recommend a topical sealer. If you are unsure or would like further information, don’t hesitate to contact me here at Concrete Treatments.

As you get out and look around, pay attention to your concrete sidewalks, garage floors and driveways. Have the salts and ice melts started to deteriorate your slabs? Do you have those nasty hard water stains from last years sprinklers? Take the time and think about the investment on what it will cost to replace your concrete.

Cleaning and sealing exterior concrete is a great way to protect this investment. Whether its brand new concrete or 50 years old, there is a sealer that is designed for your situation. As you already know, we take our experience and industry knowledge to provide you with the longest lasting solution for your situation. Lets not wait until fall to think about our concrete again because before you know it, we’ll set another record; earliest measurable snow ever recorded in Minnesota.