Tag Archives: concrete spalling

Siloxa-Tek 8505 Concrete Sealant

Siloxa-Tek 8505 Concrete Sealant

Recently I received a question from a reader who was having condensation issues in his post frame (pole) building. Amongst my suggestions was using a concrete floor sealant, if there was not a well-sealed vapor barrier underneath the slab. Following this conversation, my reader did his research and determined a silane concrete sealant such as Siloxa-Tek 8505 would be a first choice.

This will not be an endorsement of Siloxa-Tek 8505, as I have not personally used it, however so far online reviews are positive. If deciding to utilize this product, do your own due diligence to determine the best product for your needs.

Siloxa-Tek 8505 is an industrial-grade, water-based, silane/siloxane sealer. Engineered to reduce water and moisture intrusion, Siloxa-Tek 8505 also protects concrete from deicing salts and chloride-ion ingress, as well as resisting staining from oil and fluids. This penetrating sealer dries clear and may be an ideal choice to seal concrete, brick, or masonry driveways, garages and patios.

Two coats of sealant are recommended. It comes in ready to use 125 square foot coverage gallons as well as a concentrate. When a gallon of concentrate and four gallons of water are mixed it covers five times an area, at roughly three to four times of an investment.

Benefits of Siloxa-Tek 8505 include: resisting staining from oils and grease. It reduces deicing salt damage, spalling and cracking, freeze-thaw cycle damage, mold and mildew growth and moisture intrusion and water ingress. It prevents efflorescence. No appearance change to concrete as it dries clear. Excellent for water beading, Seloxa-Tek 8505 applies easily.

Concrete slabs must wait 28 days after pouring, prior to being sealed. Manufacturer recommends applying over Lithitek 4500 primer. It can be sprayed, rolled or brushed on in temperatures between 40 and 95 degrees F. It only requires five minutes between coats. Dry to touch within six hours and fully cured in 24.

If you think you ever might want to paint a sealed concrete surface, use Siloxa-Tek 8500 instead.

Concrete after a Fire

We recently received a request from a client who had a building burn to the ground. The client proposed to reuse their existing concrete – which to me has always resonated as a bad choice.

But is it actually a bad choice?

Concrete can be some amazing stuff. In June of 1987, I was privileged enough to attend the 88th annual Rotary International convention in Glasgow, Scotland. In conjunction with this event, I was a member of a group which also toured England and Scotland by bus for over three weeks. One of the stops on our tour was the Roman Baths, located in (of course) Bath! In the first century A.D. the Roman occupiers constructed first a temple and then continued to build a bathing complex at this site. Among their improvements were concrete roads – which I actually walked upon, still intact after nearly 2000 years!

Concrete is obviously one durable building material, but how does it hold up under fire?

concreteWell, the heat from fire can result in the breakdown of the chemical composition of concrete. Other effects include spalling of the concrete, which is seen as large pits. While the concrete may have protected substrates below, further investigation is probably required. Water used on the fire can also adversely affect underlying soils. It is always best to have an engineer who is familiar with concrete test for strength as sometimes it may look like the concrete is ok, but then later it begins to crumble.

To protect themselves, many Building Departments may impose requirements such as, “An affidavit from a registered design professional certifying that the effects of the fire have not significantly lowered the structural bearing capacity or water vapor retardation of the slab, including a minimum of two concrete core strength tests.”

In cases which do not require a Building permit, or structural inspections are not part of the process, it is best to perform due diligence before relying upon the strength of burned concrete.

A concrete rebound hammer can be used to field test the structural integrity remaining in the concrete. These hammers employ a rubber impact system which measures the amount of elastic rebound when a rubber insert impacts the surface of the concrete. More about concrete rebound hammers can be read at: https://www.proceq.com/products/concrete-testing/concrete-test-hammer.html?L=0&pqr=3

Soot needs to be blasted from the concrete surface with either a dry ice mixture (Best as it is least damaging) or sand. A surface-strengthening bond product can be applied after all soot is removed. Because extreme heat makes the concrete porous, the surface-bonding agent will help to protect it from moisture and eventual crumbling. If the concrete surface has suffered only slight damage from spalling, but the structural integrity is still intact, small spalled areas may be removed and patched with concrete mortar.

In my mind, I really cannot recommend reusing burned concrete without a thorough engineer’s investigation. Providing the engineer has approved its use, several avenues can be taken.

My preference would be to cut out areas of the concrete where columns would be located, excavate to place them in the ground and fill in between the new columns and the existing slab with readi-mix. As an alternative, engineered brackets can be mounted to a slab to support the columns, provided the concrete below has adequate thickness to support the weight of the structure. https://www.hansenpolebuildings.com/blog/2012/09/concrete-brackets-2/

Concrete Spalling

My home outside of Spokane, Washington is located in an area which is subjected to a variety of weathering patterns which can prove to be stressful to concrete flatwork. Being on a lake, subjects concrete to high humidity, due to the amount of moisture in the area. Added to this, my home is in an area which has its own micro-climate. It is not unusual to see several feet of snow, when not a 30 minute drive away there will be no snow at all. Most winters will see temperatures drop below zero for several weeks, and 15 to 20 below is not an unusual event.

When my pole building garage floor was poured, it was a large enough area to require more than a single truckload of ready mixed concrete. On the day it was poured, temperatures hovered just above freezing. The first load was fairly wet, the second load, a “clean up” was a leftover from another pour in the area, and must have had an accelerator, such as calcium chloride added to it, as even though it was delivered several hours after the first load, it cured far quicker than the first pour.

All of these factors contributed to a finished pour which has not held up well at all – it has dramatically spalled.

Concrete Spalling Spalling concrete is concrete which has broken up, flaked, or become pitted. This is usually the result of a combination of poor installation and environmental factors which stress the concrete, causing it to become damaged. On a low level, it can be purely cosmetic in nature, but it can also result in structural damage, such as damage to reinforcing bars positioned inside the concrete. For this reason, it is important to address spalling when it first starts to appear.

The signs of spalling are easy to spot. The surface will become rough and flaky, and may pit. In some cases, chunks of concrete break loose from the installation. The concrete can also start to crack, especially if large chunks break off. It can be repaired by totally removing the damaged section of concrete and filling it in with new concrete.

The best time to address spalling is when concrete is first poured, by taking steps to prevent it from occurring in the first place. The concrete should be mixed with the right amount of water, and ideally the mix kept as dry as possible because high water content can weaken the material. It also needs time to cure properly and should be handled carefully during curing. Sealing the concrete can also protect it from the elements.

If signs of deterioration are spotted in a concrete installation, it is best to act quickly to address them. The longer concrete is allowed to crack, pit, chip and flake, the higher the risk of serious damage.

In the case of my own floor, spalling is so bad, the solution is going to be to chip out all of the concrete, and repour the floor.