permeation grout NASA

Permeation Grout vs. Sodium Silicate, Which is the Better Choice for Soil Stabilization?

In Commercial Blog Posts, Permeation Grout by John Topa

When it comes to soil stabilization projects, many contractors are faced with a choice when it comes to the different materials and processes to utilize. Permeation Grout vs. Sodium Silicate is a common choice that contractors are faced with when planning soil stabilization projects.

NASA Kennedy Space Center Faced the Same Decision That Many Contractors Face

At a recent project for the NASA Kennedy Space Center in Cape Canaveral, Helicon was one of the various contractors bidding for the soil stabilization project for the rocket launch assembly area.

Some contractors submitted bids to stabilize the soil with a sodium silicate solution, while others, like Helicon, submitted a bid for the project utilizing permeation grout as a soil stabilization solution. Helicon’s bid was accepted because our trained business development representative laid out the pros and cons of permeation grout vs. sodium silicate for the NASA project. In this post, we will cover all the bases on how these two solutions work and what solution is best for your next commercial project.

Types of Chemical Grouting for Soil Stabilization

Soil stabilization grouting involves either injecting grout materials into the ground to fill gaps in soils, rock, or sand or injecting a grout that turns granular areas into a solid mass.

There are different types of grout injections that are used to solidify foundations, create barriers to water flows, offer support for excavation projects, and stabilize or strengthen existing soils. For this comparison, we focus on the two main types of chemical grout: sodium silicate and permeation grout.

Chemical grouts come in many forms. Two of the most popular types of chemical grout are sodium silicate grout and a polyurethane-based permeation grout. Each type has its uses, characteristics, and advantages.

Common Uses of Chemical Grout

At its core, chemical grout is a way to fill space in the medium being grouted. Grouting is usually done to improve the soil structure or to reduce the hydraulic conductivity of the soil or rock.

Chemical grouting can be done before or after excavation to provide support, increase stand-uptime, and reduce settling. Chemical grouting also helps improve bearing capacity.

Selecting the Right Chemical Grout Process

The permeation grout process uses a polyurethane-based method that has considerable advantages over sodium silicate grout. For many projects, permeation grouting has considerable benefits.

Ease of Application

Permeation grout is much less invasive than sodium silicate grout. Permeation grouting is done by drilling holes that are just 5/8” and inserting a half-inch rod into the soil. The rod is used to pump the grout into the area. When the process is complete, the holes are easily filled. Low viscosity means that permeation grouting penetrates deeply into the soil and encapsulates and strengthens the loose soil it contacts.

In contrast, sodium silicate grouting means using 2.5-3” steel pipes to inject the grouting material. These pipes can easily drill into existing rebar or other structures. Also, there are challenges to the aesthetic and cosmetic look of the property. With permeation grouting, there is a far smaller chance of hitting existing infrastructure.

Impact of Water Table
permeation grout sodium silicate

Water table management is a critical consideration for construction in Florida. With permeation grouting, there is no risk from the fluctuating water tables that are very common in Florida soils. However, sodium silicate grouts can shrink over time and lose strength when exposed to fluctuating water tables. Wet and dry cycles underground will cause the permeated sand to degrade and shrink over time.

No Water Necessary

Polyurethane permeation grout is hydrophobic. There is no need to mix with water, as with cement-based products.  The permeation grout is injected as a resin. It is a resource-friendly solution that means fewer resources are needed at the construction site.

The polyurethane grout that Helicon utilizes is phthalate-free. At Helicon, we only use permeation grouting materials that are certified for compliance with NSF 61-5, meaning they are approved for contact with drinking water.

Compression Strength Reliability

You want a chemical grout solution that has the highest possible compression strength for ideal soil stabilization. With permeation grout techniques and polyurethane bases, you can achieve a compression strength of 1500-2,085 psi in confined sandy soils. That is 2-3 times the compression strength of sodium silicate grout. Depending on the mix design, silicate concentrate, and the type of organic or inorganic hardener used, the sodium silicate compression strength can be as low as 25-30 psi in the sand.

Time to Cure  

Time is money in construction projects. The cure time for permeation grout is 3-4 hours. For sodium silicate grout, the cure rate is measured in days not hours. Sodium silicate can take between 7 and 28 days to reach full strength.

No catalyst is required when using our permeation grout techniques. However, an optional catalyst is available, which can reduce curing times even further to as little as 25 minutes.

How It is Injected

Planning is critical to effective results using permeation grout. Areas and depths should be pre-determined to create an injection matrix. Once completed, calculations can be performed to determine the volume of permeation liquid necessary to be injected at each point in the matrix to ensure thorough soil cohesion.

When using permeation grout as a soil stabilization method, our professionals ensure that all safety precautions are followed and wear personal protective equipment. Permeation grouting is usually done in defined zones using sleeve ports that are installed in the soil or within the rock. This approach allows the grout to be injected at specified locations for precise placement.

If the optional catalyst is required, it is added and stirred using a low-speed drill or mixing paddle. A diaphragm pump or airless sprayer is used to apply the grout. Once inserted, the liquid permeates the soil or sand, causing the particles to bond together.

The Choice is Clear

The benefits of utilizing permeation grout as a soil stabilization method vastly outweigh the benefits of utilizing sodium silicate grout. From the ease of application to strength to time to cure, permeation grout wins every time. NASA came to this same conclusion; that permeation grout is the superior choice for soil stabilization when it comes down to all the benefits it holds over sodium silicate.

It doesn’t take a rocket scientist to see that if permeation grout is the best soil stabilization solution for NASA, then it should be good enough for any project. Permeation grout is an important component of many Florida soil stabilization construction projects. To learn more about Helicon’s expert permeation grout methods, contact us today.