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Comparing Decorative Concrete Sealer Stripper Application Methods

Nox-Crete was asked to consult on a difficult decorative concrete sealer stripper project. A 3500 square feet stamped pool deck had been sealed and resealed over time with up to five coats of an acrylic sealer with 25% solids. No stripping had been done between layers.

This thick film buildup had created an impermeable barrier that trapped water vapor coming up from the subgrade. Pressure from the water vapor caused the sealer to delaminate from the concrete, which turned some areas white in color. In addition, the thick film had suffered UV damage, and appeared dark green.

Test Methods to Strip 5 Coats of Decorative Concrete Acrylic Sealer

A test was conducted to determine the best method to remove the old coats of sealer. The test was scheduled for a clear day with a temperature of 84-degrees Fahrenheit. There was a slight 7 mph wind and 52% humidity.

Three methods were tested to remove the thick film of decorative concrete acrylic sealer:

  1. Aro-Peel stripper system with an engineered cellulose blanket was applied to a small area next to the house. Aro-Peel decorative concrete sealer stripper blanket system is sold in Canada, and a similar product—Deco-Peel—is sold in the United States.
  2. Deco-Strip sealer stripper was rolled on a large section, and then pressure washed according to use instructions.
  3. Deco-Strip sealer stripper was applied with a sprayer to another large section. The section was then scrubbed with an electric floor scrubber to loosen acrylic layers and then pressure washed according to use instructions.

Aro-Peel Decorative Concrete Sealer StripperAro-Peel Decorative Concrete Sealer Stripper Test

Aro-Peel’s controlled blanket application strips decorative surfaces of aged, chalky or faded sealers without pressure washer, accidental splatter, or the creation of hazardous waste. This is best for areas against a house where splatter can cause problems. The test area was next to the house, and was applied in direct sun in an area with little to no wind.

The surface was swept clean of debris, and the crew cut and shaped the blanket to fit the test area. The Aro-Peel was rolled onto the blanketed surface until the fabric was fully saturated and had turned translucent. Special care was taken to saturate all valleys, joints and ridges on the surface until the surface texture was visible through the fabric.

Aro-Peel Stripped 5 Layers of Decorative Sealer StripperAfter 3.5 hours, the blanket was peeled up to check for evidence of acrylic and to ensure that the surface wasn’t slimy. This is an indicator that the acrylic is still softening and has not absorbed into the blanket. Once the blanket had dried, it was peeled back and placed into garbage bags for proper disposal.

Aro-Peel successfully removed all five layers of acrylic sealer in this test. However, it must be cautioned that a second application with fresh blanket may be required to remove this many layers of sealer.

Pressure Washed Deco-Strip Test

Deco-Strip Results On 5 Layers of Decorative Concrete Sealer

A large section of the pool deck was swept clean of debris, then Deco-Strip was roll-applied and allowed ample dwell time to penetrate all the way through the acrylic sealer. Multiple light coats kept the Deco-Strip wet until the acrylic had been softened. Dwell times generally range from 30 to 90 minutes depending upon thickness of sealer to be removed and application rate of Deco-Strip. When the sealer was soft all the way through, it was time to remove with a pressure washer.

With five layers of sealer, this method was difficult. In this test, the traditional way to use Deco-Strip required a lot of water, gas for the blowers and also took a long time. If the patio had two to three light coats and was smaller—this would be an acceptable method. The test did resolve the problem, but it was decided to use another method to reduce the man hours required.

Electric Scrubber Modified Deco-Strip Test

Using a scrubbing machine to speed decorative concrete sealerA modified application test used a sprayer to apply the Deco-Strip to a large area. The Deco-Strip was allowed to sit for 3 to 5 minutes. The crew then moved the floor scrubber onto the wet product and started scrubbing in a circular direction using scrubbing pads.

The scrubbing pads were replaced every 3 to 4 minutes. To remove 5 layers of hardened acrylic, 3 pads should be used in a cycle pattern: using one, cleaning one and holding one on standby.

Once the scrubber operator and machine had moved to a new area, the previous area was lightly pressure washed to direct the stringy/sticky bubble gum-consistency old acrylic residue into a “rope” line. Larger pieces were scooped up with a shovel.

This modified method shortened the required time by 80%. The stamped concrete was successfully restored back to original unsealed condition. Natraseal LVOC acrylic sealer was used to finish the project. UV inhibitors will prevent yellowing over time, and the homeowner can expect a sealer lifetime of up to five years.

Properly Removing Bondbreaker from Concrete Can Help Cut Potential of Tilt-Up Floor Sweating

by Craig Coppersmith, P.E., VP Technical Sales & Marketing

Nox-Crete strives to create the highest quality chemicals for the concrete industry, and to consult with architects, engineers, contractors and distributors regarding the use of our products and their impact on the maintenance of concrete. Our goal is to ensure that those products enhance both the performance and appearance of concrete floors.

Recently, there has been much discussion in the concrete construction industry regarding the phenomenon of sweating floor slabs (commonly referred to as Sweating Slab Syndrome) in warehouses and distribution centers. There are multiple factors that have been suggested to contribute to Sweating Slab Syndrome, including trace amounts of reactive bondbreaker that may remain on floors in casting areas.

Understanding and sharing in the concerns about Sweating Slab Syndrome, the Nox-Crete team set out to verify that our Silcoseal Cure and Bondbreaker could be effectively removed from a tilt-up floor following our standard recommendations for removal, which is cited in our product data sheets. This would validate our recommended processes for removal of Silcoseal Cure and Bondbreaker and eliminate it as a possible contributor to the Sweating Slab Syndrome, by virtue of a proven method for its removal.

To demonstrate that Silcoseal Cure and Bondbreaker testing, sweating slab, bondbreakercould be effectively removed, Nox-Crete contracted with Nelson Testing Laboratories (NTL)—an independent, certified testing agency—to perform a mock tilt-up using Silcoseal Cure and Bondbreaker and Nox-Crete’s citrus-based stripper, Bio-Clean Concentrate CPC, for the removal.

Analysis Process
NTL mixed and poured concrete into a 9-foot x 4-foot x 2-inch thick mold. The concrete surface was finished with a steel trowel and coated with two coats of Silcoseal Cure and Bondbreaker, applied at 400 sf/gallon, 24 hours apart. After another 24 hours, a concrete wall panel was cast on top of the original concrete specimen. After another 48 hours, the wall panel was separated from the original concrete specimen.

The exposed face of the concrete casting surface was then sectioned into three equal parts: uncleaned; cleaned with Bio-Clean diluted 1:3 with water; and cleaned with Bio-Clean diluted 1:5 with water.

The uncleaned sample was left untouched. The area cleaned with Bio-Clean diluted 1:3 was stripped with a 1:3 ratio of Bio-Clean Concentrate CPC to water solution, using a nylon scrub brush simulating a downward force of 100 pounds. The area cleaned with Bio-Clean diluted 1:5 was stripped with a 1:5 ratio of Bio-Clean Concentrate CPC to water solution, using a nylon scrub brush simulating a downward force of 100 pounds.

Four 50-gram samples were then extracted from the concrete casting surface—plain concrete; concrete exposed to Silcoseal Cure and Bondbreaker but not stripped with the Bio-Clean solution; concrete exposed to Silcoseal Cure and Bondbreaker and stripped with the 1:3 Bio-Clean solution; and concrete exposed to Silcoseal Cure and Bondbreaker and stripped with the 1:5 Bio-Clean solution.

Methods of Analysis
The four pulverized concrete samples were chemically extracted with η-hexane. To remove all organic substances, 50 grams per each of the four samples were extracted.

The liquid extract from each of the four concrete samples and the liquid samples of the Silcoseal Cure and Bondbreaker and Bio-Clean Concentrate CPC were dried on a universal diamond Attenuated Total Reflectance Accessory (ATR) for Infrared Spectroscopy, then analyzed using a Perkin Elmer Spectrum Model One Fourier Transform Infrared (FTIR) Spectrometer, with a configuration of resolution of 4 cm-1 and eight accumulations (number of scans) per sample.

Samples Received for Analysis
Six samples were analyzed:
A)   Bio-Clean Concentrate CPC (liquid sample)
B)   Silcoseal Cure and Bondbreaker (liquid sample)
C)   Plain concrete not exposed to Silcoseal (50 g. sample – pulverized concrete)
D)   Concrete exposed to Silcoseal, not cleaned (50 g. sample – pulverized concrete)
E)   Concrete exposed to Silcoseal, stripped with 1:3 ratio of Bio-Clean Concentrate CPC to water (50 g. sample – pulverized concrete)
F)   Concrete exposed to Silcoseal, stripped with 1:5 ratio of Bio-Clean Concentrate CPC to water (50 g. sample – pulverized concrete)

Extraction and Infrared Spectroscopy Analysis Results
Evidence of the presence of Silcoseal Cure and Bondbreaker was not found in three of the pulverized concrete samples (Samples C, E & F). However, Sample D, the pulverized concrete that was exposed to Silcoseal but not cleaned, contained a detectable amount of organic extract, indicating the presence of Silcoseal─as expected.

Both of the stripping solution ratios (1:3 and 1:5) of Bio-Clean Concentrate CPC to water effectively removed the Silcoseal Cure and Bondbreaker.

The infrared spectra of both of the extracts from Samples E & F show a sharp absorption band around 1100 cm-1 (frequency), which is due to the presence of the Bio-Clean. Organic substances from the Silcoseal Cure and Bondbreaker are not evident in the spectra of Samples C, E & F, but are evident in Sample D.

Summary: Nox-Crete’s Interpretation of the Analysis Results
Proper surface preparation will remove all trace amounts of Silcoseal Cure and Bondbreaker and its heavy metallic soaps from concrete tilt-up floors. If no Silcoseal Cure and Bondbreaker residue remains on the tilt-up floor, it cannot contribute to Sweating Slab Syndrome.

NOTE: NOTE: These independent tests were only conducted on Nox-Crete-branded products. It is unknown whether other brands of reactive bondbreakers can be successfully removed.These independent tests were only conducted on Nox-Crete-branded products. It is unknown whether other brands of reactive bondbreakers can be successfully removed.

The most effective way to remove Silcoseal Cure and Bondbreaker residue is with Nox-Crete’s Bio-Clean Concentrate CPC. Nox-Crete recommends taking these steps to remove bondbreaker residue from concrete floors:

  • Dilute Bio-Clean Concentrate CPC 1:1 with water for stripping heavy coatings. For removal of lighter coatings,dilute with a ratio of 1:3.
  • Uniformly apply by sprayer or through an automatic floor machine at an application rate of 200-300 sf/gal (5-7.5 sm/L).
  • Allow product to dwell on the floor surface for 20-30 minutes while aggressively scrubbing the surface with an automatic floor machine equipped with nylon scrub brushes.
  • Squeegee the surface clean and rinse thoroughly with water.

Follow these links to learn more about Nox-Crete's line of Silcoseal Cure and Bondbreakers and Bio-Clean Concentrate CPC, or call our customer service team at 402-341-2080.

Liquid Hardeners Realize Maximum Performance When Applied After 28 Days

Patience is a Virtue - Testing Confirms Liquid Hardeners Realize Maximum Performance When Applied After 28 Days

A growing trend within the concrete flooring industry is to apply liquid hardeners on freshly-troweled concrete in what is referred to as a “pre-seal” or a “cure-coat.” Conversely, Nox-Crete has historically advised applicators to wait and apply liquid floor hardeners a minimum of 28 days after concrete placement to allow for maximum performance. The 28 day recommendation was based on intuition and a strong understanding of the chemistry behind liquid floor hardeners and the means by which they densify concrete surfaces. The lack of conclusive data led Nox-Crete to not only ask but to answer the question, does the timing of the application (Day One vs. Day 28) impact the liquid floor hardener’s ability to improve abrasion resistance? Continue reading