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What Is Limestone Slurry? | Stone Slurry Grout Concrete Leveling

August 11th, 2023 | 4 min. read

By Sarah Etler

Get to know the “limestone slurry” – one of the leveling compounds A-1 uses to lift and level sunken concrete slabs.

Concrete leveling can be a complex world to navigate, with various methods, terms, and materials to understand. It's no wonder it can feel overwhelming at times. But in this article, we're here to shed some light on one of the main types of concrete leveling: stone slurry grout leveling.

Stone slurry grout leveling is a tried-and-true method that utilizes all-natural materials to lift sunken concrete slabs back to their proper positions. 

Our goal here at A-1 Concrete Leveling is to empower you with the knowledge and facts you need to make informed decisions about your concrete repair and maintenance needs.

That's why we've crafted this article, specifically focusing on an important component of the stone slurry grout leveling process: the limestone slurry.

What is the “limestone slurry”?

The limestone slurry used in stone slurry grout leveling is a mixture of pulverized limestone blended in-house at each of our franchises. The limestone slurry is optimized specifically for the A-1 Concrete Leveling process. 

Limestone Slurry Means More Control

On the job site, the dry pulverized limestone is mixed with the right amount of water depending on the specific needs of each repair. Adding more water allows the thinned-out slurry to spread and fill all the gaps and voids under the slab, whereas the thickened slurry works harder to lift the sunken slabs.

Being able to control the viscosity and ratio between spread and lift gives us the most control over the repair. It also takes stress off of the slab, minimizing the potential for cracking.

Depending on the needs of the repair, we can also add Portland cement to increase overall strength and accelerate the hardening process.


How is the limestone slurry used in concrete leveling?

All forms of professional concrete leveling involve drilling holes in settled concrete slabs, injecting a leveling compound through the holes and under the slab, then using the pressure from the compound underneath to lift the slab back up to an even position.

In the stone slurry grout concrete leveling process, the limestone slurry is what’s pumped through the drill holes. Once the slurry fills all the voids below the slabs and lifts them back up, the material eventually hardens and is used as a new base for the concrete slab to rest on evenly.

Related Resource: How Does Concrete Leveling Work?

What does the limestone slurry look like?

The limestone slurry is pumped under the concrete wet, but then dries and hardens under the slab to support the newly leveled concrete.

Limestone slurry grout being injected under a settled concrete porch step during a concrete leveling repair

Wet During Repair

The fine, powdery pulverized limestone is mixed with water to form a paste that looks similar to wet concrete. It has the consistency of a thick milkshake, and depending on the local quarry where it’s sourced, the color could range from gray or white to somewhat pink or yellow.

When pumped below the surface of the concrete, it should be contained by the landscaping around the slab and shouldn’t leak out of the edges. 

If you can see edges of the concrete slab that aren’t covered by landscaping, you’ll need to add sod, landscaping, or additional soil to cover the limestone slurry under the slab and maintain the repair.

Dried After Repair

Over time, the stone slurry hardens under the slab. The color of the dried material is typically white or gray, but you really shouldn’t be able to see it as it should be contained under the slab with adequate landscaping.

The texture of dried limestone slurry is quite unique. It dries to a hard, clay-like consistency, but it doesn't shrink down or lose volume over time. It can also take on moisture from the surrounding soils without compromising the integrity of the repair.

It can break apart if crumbled in your hand or dug at with something sharp, but it will stay together completely when weight is put on top of it or something hits it hard and fast.

The fact that the material has so much compressive strength (meaning it holds up against downward pressure) makes it perfect for holding up heavy concrete slabs and supporting vehicle traffic.

Is the limestone slurry messy?

While it may look a little messy during the stone slurry grout leveling process, any excess material can be easily washed away when the repair is complete. The limestone slurry is water soluble and made out of 100% natural materials, making it easy to clean up and safe for plants and animals.

Related Resource: Will Concrete Leveling Harm My Landscaping or Lawn?

Concrete leveling technician washing off limestone slurry grout a sidewalk after a concrete leveling repair

How long does it take the limestone slurry compound to dry?

The outside edges of the limestone slurry material under the concrete slab may never dry completely depending on how much moisture it’s exposed to and the chemistry of the local limestone used.

However, exposure to water, which prevents the exterior layer from completely hardening on the outside edges, doesn’t mean the inside area isn’t hardened or the slab on top isn’t supported. Even when completely wet, the limestone slurry is weight-bearing immediately after being injected under the concrete slab.

Keeping landscaping and soil levels up around the edges of the slab can help the exterior layer to dry out, but it’s not a problem if it never does. Your concrete will be level and supported no matter how wet or dry the material underneath is.

How This Affects You

Regardless of how wet the limestone slurry is, it is immediately weight-bearing when pumped under the concrete slab. We advise staying off of the repaired area for 24 hours in order to allow the patched drill holes and caulking to dry and cure undisturbed.

Most people are concerned about the material used for concrete leveling itself, but the most important factor is the ground that’s underneath. If the variables that affect settling are still present, then it will settle no matter what materials you use to lift.

As long as you take preventative measures to avoid resettling, like redirecting downspouts and drainage, keeping up with soil levels around the repair, and making sure there are no pests making a home under the slab, the wetness or dryness of the material does not matter.

Next Steps

At the end of the day, the limestone slurry used in stone slurry grout concrete leveling is a durable and highly effective way to lift and preserve your settled concrete.

If the limestone slurry doesn’t help solve the problem at hand in a long-lasting way, there are likely other environmental factors (erosion, pests, natural settling) at play that need to be addressed first.

Here at A-1 Concrete Leveling,  the process and material we’ve been using for over 30 years have helped countless homeowners and businesses reclaim their concrete, and we are proud to offer a warranty to provide extra peace of mind.

If you’re interested in seeing what concrete leveling can do for you, click the link below for a free onsite concrete consultation and cost estimate with an A-1 Concrete Leveling expert!

Before you go, be sure to check out these related topics from our online resource library, Concrete Academy:

Sarah Etler

Sarah Etler joined A-1 Concrete Leveling after receiving her Bachelor of Arts degree in English from Northern Kentucky University. As A-1's Content Marketing Manager, she works closely with industry experts to produce content that will best answer questions related to concrete repair and maintenance practices. Sarah loves living a life full of discovery and is excited every day to see what new things she can learn and share with those around her.