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Concrete Surface Preparation – Mechanical prep vs Acid washing

A Closer Look at Portland-Limestone Cement
and the Questions It Raises

In the race toward reducing carbon emissions and building a more sustainable future, the construction industry has placed significant emphasis on material innovation. One of the most talked-about shifts in recent years is the rise of 1L concrete, also known as Type 1L Portland-limestone cement (PLC). While its environmental intentions are clear, the execution and field performance of this material have sparked deep concerns among contractors, finishers, and construction professionals across the country.

What Is 1L Concrete?

1L concrete is a blended cement product made by intergrinding Portland cement clinker with up to 15% finely ground limestone. It falls under ASTM C595 and was promoted as a more sustainable option than traditional Type I or Type II cement, with a claimed reduction in embodied carbon of about 10%.
This transition is part of a broader movement toward lowering the construction industry’s carbon footprint. However, for many professionals working in the field every day, the reality of 1L’s performance has not aligned with its promise.

Why the Push—And Why the Pushback?

Advocates of 1L cement cite decades of successful use in Europe and a growing need for climate-conscious practices. Major producers in the U.S. began shifting almost entirely to Type 1L in 2022 and 2023, often with little consultation or consideration for the practical realities faced by contractors and specialty finishers.
This sudden change, often framed as a “drop-in replacement,” has led to a number of serious challenges:
Surface Defects & Finish Failures
Many contractors have reported inconsistent finish quality, scaling, dusting, and difficulty achieving color uniformity in decorative and exposed applications. In some cases, these issues have led to litigation over failed installations.

Lack of Field Testing & Support

Although some densifiers and admixtures are being promoted as compatible with 1L, most have not undergone sufficient independent testing to ensure reliable long-term performance. Contractors are left to troubleshoot on their own, often at their own expense.

Distrust from the Field

For many in the construction world, especially those working on architectural concrete, decorative finishes, or high-performance surfaces, the lack of transparency and technical support has created a deep sense of frustration and mistrust.

What Industry Experts Are Saying

While many material producers remain committed to 1L cement, an increasing number of contractors, specifiers, and consultants are raising red flags. Some are now avoiding 1L altogether in high-exposure projects or are specifying additional treatments, sealers, or surface hardeners to compensate for performance issues.
Yet even these remedies come with asterisks: most haven’t been thoroughly tested alongside 1L, and results vary based on climate, substrate, and finishing practices. While some contractors are beginning to find combinations that work, there is no universally endorsed solution at this time.

Proceeding with Caution

There’s no question that sustainability is an urgent priority—but true sustainability must also account for durability, performance, and constructability. When cement fails in the field, the environmental impact of replacement materials and labor far outweighs any initial carbon savings.
As the industry continues to explore lower-carbon alternatives, many experts are calling for a more thoughtful, transparent, and inclusive approach—one that includes rigorous testing, real-world data, and support for the contractors on the front lines of implementation.

The Bottom Line

1L concrete may represent a step toward sustainability, but for now, it’s a step that should be taken with full awareness of its limitations. The current landscape demands caution, continued evaluation, and an honest dialogue between producers and practitioners.
Until field data improves and manufacturers take stronger accountability for performance, the use of 1L cement should be considered on a case-by-case basis, especially in projects where finish quality, color uniformity, or long-term durability are critical.

When it comes time to prepare a floor for a coating or resurfacing system a decision must be made as to whether to mechanically prep (grind or shot blast) or chemically prep using an acid wash.  Either way, the end result is to provide a clean, sound surface with a rough texture referred to as a concrete surface profile or CSP.

You may be tired of hearing it, but take care and wear your safety gear…eye protection, respirators, and if you are using acid to chemically prep, gloves. If acid comes in contact with your skin, immediately rinse with fresh water. Refer to the product Safety Data Sheet before using any harmful chemical.

Mechanical surface preparation of a concrete slab:

The two most common methods to mechanical prep a concrete surface are grinding and shot blasting.

Grinding requires the use of floor grinders or polishing machines that spin abrasive pads on the surface of the concrete that will remove coatings, old sealers, adhesives, as well as create a scratch pattern and rough texture to which new material can be applied.  These machines can be used wet or dry and require vacuuming of either the wet slurry or dry concrete dust created during these processes. The tooling you use on your machines will make a significant difference in the time it takes to complete your floor prep, as well as the final quality of the prepped surface. We carry a diverse selection of high-quality tooling available to get you started.

 

 

Shot blasting is a method of surface preparation that uses small beads propelled out of a machine at a high speed. The beads are shot out of the machine, striking the floor and are sucked back into the shot blaster to be reused. This “blasting” creates a sandpaper-like finish that is ideal for a strong adhesion between the existing concrete and new material. Generally, after shot blasting is done the surface is clean and ready for new material with minimal cleanup, thus making shot blasting a very cost-effective floor prep option.

 

 

Chemical Prep:

Chemical floor prep utilizes an acid to etch and burn the surface of the concrete, opening the pores of the concretes cream and creating a rough surface that is ideal for new material adhesion.  This method involves diluting the acid with water and scrubbing the solution into the slab.  The acid will “sizzle” as it reacts with the cement causing it to weaken and eventually dissolve. If muriatic acid is used it will need to be neutralized with baking soda or ammonia and rinsed thoroughly with water (commonly pressure washed). You will also need to protect all plants, grasses, and animals throughout this process. If you’re hesitant to use such a harsh chemical but do not want to sacrifice etching strength try SureCrete’s Super Concrete Renovator or SCR. SCR is an eco-friendly detergent, degreaser, and hydrochloric acid that contains no toxic heavy metals, or ozone-depleting solvents. This acid also does not need to be neutralized, can be rinsed down any drain, and can be used to earn LEED points. Click the link for more information: https://www.surecretedesign.com/product/concrete-cleaner/

 

 

Mechanical floor prep is most commonly favored over chemical for a couple of reasons.  Mechanical floor prep leaves a better surface profile which will increase adhesion between the existing slab and new material. Mechanical prep removes coatings, glues, thin set, etc. without introducing strippers or emulsifiers that may interfere with the bond between the slab and the new material.  Mechanical prep can be done dry which is better when applying coatings that are sensitive to moisture, such as epoxy.

Mechanical prep is not always possible.  There may be a texture that needs to be preserved.  In cases such as this, a chemical stripper to remove old coatings plus a chemical etch is required.  The EPA recently banned all chemicals that contain methylene chloride to be removed from manufacturing and shelves. Currently, most strippers contain this chemical.  We have a new replacement product, FAST STRIP, that is a strong emulsifier, pH neutral, stays wet, contains no solvents, and can be cleaned up with water.  FAST STRIP will remove VCT glue, carpet glue, polyurethane, polyaspartic, water-based epoxy, acrylic, and when diluted FAST STRIP can be used to remove graffiti without damaging the substrate. Emulsified materials can be scrapped up and thrown away with no special treatment. Rinse the surface thoroughly and with clean water. Click on the link for more information: https://selectsurfacesoln.com/cleaning-repair-supplies-in-orlando/

Resurfacing or coating an existing slab can be costly.  Deciding how to prep the concrete properly is the first step to having a successful outcome.  The Select Surface Team is ready and able to help you make that decision. Call us at 407-730-3103!

 

 

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