Expansive clay soil causes an extensive amount of damage to roads, walkways, foundations and other structural elements. According to the American Society of Civil Engineers, in a typical year, expansive soil causes greater financial losses to property owners in the U.S. than earthquakes, floods, hurricanes and tornadoes combined.
These statistics are surprising to many people, and that’s probably because the damaging effect of expansive soil typically happens in a gradual manner. Tests have demonstrated that clay can expand in volume by as much as 10% when it absorbs water. In doing so, it can exert as much as 5,500 pounds per square inch of pressure. This pressure can be applied as an uplifting force, as a sideways force, or from multiple directions.
Expansive clay soil has another characteristic that also causes structural damage: It contracts when it dries out. So after pushing up against a sidewalk, slab or wall during wet periods, it shrinks away as the soil dries out, creating voids that can also cause concrete elements to crack and sink. The deep cracks that occur during prolonged dry periods allow for greater water penetration when the weather changes, increasing expansion pressure.
Chemical Stabilization Methods for Expansive Soil
One way to protect foundations, sidewalks and other structures from expansive soils is to improve drainage in the area around them. Basic protective measures like channeling roof runoff away from a building and surrounding a foundation with highly permeable soil have proven to be effective.
However, sometimes it’s not possible to control the amount of moisture that gets into the soil. Roadways, parking lots and airport runways are simply too large to protect with water-management measures. This is where chemical treatment proves to be especially valuable.
As the name implies, chemical soil stabilization works by chemically altering the clay particles in the soil. Because of the mineral composition of clay and silt, these soil elements have a negative surface charge. Consequently, they tend to attract a positive charge, which can be found in water molecules. When clay-rich soil gets wet during rainy weather, water doesn’t pass through the ground like it does in soil that has a high sand and gravel content. Instead, clay particles attract and hold water molecules. The added volume of the retained water causes the soil to expand.
Chemical Ground Stabilization Process
In the chemical soil stabilization process, an ion exchange solution is applied to the soil to reduce the negative charge of clay particles. Once this happens, clay particles will actually repel water, allowing it to drain away.
There are two principle ways to apply the ion exchange solution. It can be sprayed over loose soil and mixed into the soil before the soil is compacted. This technique is often used prior to constructing a road, sidewalk or other slab-type element. A second application method is to drive perforated rods into the soil and inject the stabilizer under pressure. This technique us useful when soil stabilization needs to be done around existing structures, and when clay-rich soil extends to greater depth.
Home/Tract builders, airport taxiways/runways, HOAs, COAs and all new construction have benefited from the ESSL process. When you have an expansive clay soil problem, the AGSS Chemical soil stabilization method is your proven answer.