This post is part of the Alchemy-Spetec Contractor Lens series, featuring views, news & case studies written by our customers. This article, written by Lewis Evans of Stable Soils, provides an overview of polyurethane concrete repair material. If you're an Alchemy-Spetec customer and you'd like to discuss writing content for our blog, please send an email to marketing@alchemy-spetec.com today!

In Orlando FL there was a new commercial development that included a pharmacy to be constructed. Prior to the commencement of construction, a geophysical survey was undertaken to determine if site conditions were suitable for building. The survey included soil borings and DCP (dynamic cone penetrometer) readings to determine soil compaction.

The results of the survey indicated a layer of Florida muck between 10’ and 5’ below grade: this is very typical in Florida. The engineers recommended excavation down to 10’ to remove the muck from the entire building pad area as well as the entire parking lot area. After the de-mucking process, fill was to be brought in and compacted prior to pouring the building pad and preparing the parking lot for asphalt paving.

When the site work contractor informed the general contractor that the site was prepared, the GC called in the engineer to do some testing and sign off on the site work. Testing revealed that in a majority of the parking lot area, only the upper area of the soil had been excavated and replaced but the muck still was in place between 5' and 10’ deep. Some corners had been cut and the project came to a halt.

At this point, the curbs were in, the crush and run had been put down, and all utilities were already in the ground including water, gas, sewer, electrical, and fiber optic. The engineer presented them with two options:

1. Remove all the utilities, dig up the entire parking area site, and do it as they had recommended in the beginning.
2. Use 2-component polyurethane injection in a grid pattern and at different depths, to densify the soils and muck.

To remove everything and start over was going to take in excess of 2 months to complete. Facing liquidated damages from the property owners for the delays, this was going to be extremely expensive and would most likely end up in litigation. The soil stabilization with the polyurethane foam was selected as the method for the following reasons:

1. Installation in less than one week
2. No excavation required
3. Clean installation and environmentally safe product
4. Proven system used by departments of transportation - DOT
5. Factory trained, engineer approved contractor

Powerful Polymers

The polyurethane material used in this project was Alchemy-Spetec's AP Lift 475. Alchemy-Spetec rigid polyurethane foams start out at 7000 PSF bearing capacity. This rating is based on the unconfined strength of the foam. In the soil or beneath concrete the polymer will increase in strength up to 15X. For comparison, the compaction requirements for pouring slabs or building roads are about 2000 to 2500 PSF. 

Painless Procedures

AP Lift 475 was installed in a grid pattern and at different depths. The polyurethane expanded as it was installed (up to 24X by volume), and solidified the muck and unstable soil. The parking area soils were densified to the requirements of the engineer.

Rapid Results

The job was completed in just 5 days. No curbs, road base, or utilities had to be removed or relocated saving enormous amounts of additional cost and delays.

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