What is Soil Stabilization?
Soil stabilization is the general name for a wide array of treatments that increase the stability of the soil or change its physical properties to increase its load-bearing capacity - that is, to make it stronger and better able to hold weight. This is especially important when building roads, parking lots, and all sorts of buildings.
If the soil where you want to build does not meet the engineering properties required, you may not be able to obtain building permits and your building may be compromised in the future. For example, the plasticity index of the soil is vital when building roads: a high plasticity index indicates a clayey soil (that’s a fancy term for a soil that is rich in clay). Clay is very sensitive to moisture, and clay-rich soils become plastic and soft when water seeps into them. If no soil stabilization method is used before building on fine-grain soils, your newly-built construction, parking lot or road will develop waves and dents, and require repairing or rebuilding much sooner than if the soil had been stabilized before construction started.
Before attempting any kind of building, from a tiny house to a shopping mall, make sure to evaluate the soil thoroughly and carry out the necessary soil stabilization so your building pad is in top shape for laying down reliable foundations.
Types of Soil Stabilization Methods
There are many ways to stabilize soil: by mixing in other materials and then compressing the soil back down, by using chemical agents, by using biological agents, by using heat or electricity.
Let’s talk about some of the most usual soil stabilization methods, including electrical, mechanical and chemical stabilization.
Bitumen Soil Stabilization
Bitumen refers to materials such as tar and asphalt, which are “gooey” and waterproof by nature. Mixing bitumen into the soil will make it more cohesive - meaning soil will stick together instead of moving around like dust. Additionally, bitumen soil stabilization reduces water absorption, meaning it can make the soil water-resistant or waterproof, depending on the ratios used.
The most common steps for bitumen stabilization are:
- Work the soil to pulverize it
- Soak it to facilitate proper mixing
- Add the bitumen and mix it in
- Let it aerate to ensure loss of volatiles - the fewer volatiles, the stronger the soil
- Compact and level
- Aerate and cure once more
Cement Soil Stabilization
Mixing portland cement into a poor soil is a popular soil stabilization method. The cement mix reacts, solidifies, and turns into a weak form of concrete usually called soil cement. If your weak soil qualifies for cement stabilization, the process is relatively straightforward:
- Level the area you want to mix with cement.
- Work the soil to pulverize it, and soak it if necessary, then level it again
- Spread the cement and mix it in
- Add water and mix it in
- Compact well, level once more, and cure like you would cure any concrete
If certain materials, known as pozzolans, are added to the portland cement (or already present in the soil) there will be a pozzolanic reaction, which is a long term process that binds and cements the particles into a stable unit. Fly ash is an example of a pozzolan, as well as other ash and waste products that are rich in silica.
Cement kiln dust is a byproduct of Portland cement, and can usually be acquired for free at cement plants. If cost is a major factor in your construction, you might want to consider it, since it is a cheaper option that significantly improves strength and decreases swelling of the soil. Keep in mind that it may require longer curing times, and factor that in your building schedule.
Lime Soil Stabilization
Lime and cement are commonly mixed into the ground for soil stabilization, but they serve different purposes. While cement adds strength and structure, lime also helps reduce wetness in soggy and clayey soils.
There are two main types of lime: high magnesium and high calcium, and they are both equally good for soil stabilizing. Lime stabilization is usually performed with hydrated lime, officially known as calcium chloride. The process is similar to that of stabilizing with cement, with a few differences:
- Level the area you want to stabilize with lime
- Work the soil to pulverize it
- Spread the lime and add water during the preliminary mix
- Level roughly and compact lightly
- Let it sit for a preliminary cure
- Mix and pulverize again
- Compact well, level once more, and cure
Chemical Soil Stabilization
We have gone over two specific types of chemical soil stabilization: lime and concrete. In general, chemical stabilization is a process in which the soil is worked and pulverized, mixed with a chemical additive, and compacted back down. Common stabilizers include calcium chloride and sodium chloride (salt), as well as fly ash.
Calcium chloride is used when you want to improve the water retention properties of dry, arid soil. Some of the effects of adding calcium chloride to poor soil are:
- Increasing surface tension, thus making it more stable
- Decreasing the rate of evaporation, which keeps water in the soil
- Lowering the freezing point, to prevent frost damage
- Facilitating compaction
Frequent application may be required, as the additive is gradually lost by leaching action.
Sodium chloride has been used to stabilize the soil under highways and roads since the early 1900s. It is well tried and trusted for stabilizing building pads under roads and parking lots, but it is not recommended for strengthening the soil under larger, heavier constructions.
Electro-osmosis is a type of soil improvement used to remove excess water from water-logged, clayey soils. To make a long story short, electro-osmosis uses special equipment to apply electricity to wet soils and drain excess water out of the soil, therefore improving its load-bearing capacities and stability. While effective, this is an expensive method due to the highly specialized equipment and high electricity consumption, so it is only recommended in extreme cases where other methods are not applicable.
Why Soil Stabilization?
Strengthen Your Soil
Unstable soil is the source of many problems: it can turn into clouds of dust at the slightest gust of wind, or it can become a swamp after a little rain. Poor soil is easy to fix, and something you should look into even if you are just using it as a garden path or parking spot. Don’t let weak, unstable soil cause you unnecessary trouble when soil stabilization solutions are so readily available.
Improve Load Bearing Capacity & Support Structure
If you are building, the first thing you need is strong soil. Whether youŕe building a sidewalk or a skyscraper, you can’t have your soil give way under your construction, or expanding and shrinking with the seasons until you get cracks and damage.
If the soil has a high plasticity index, you will need to get it within acceptable parameters before you get building permissions.
Very dry soil made of small particles will tend to fly away easily, creating dust clouds. These clouds of dust are not just a nuisance, they can also contaminate the surrounding air and water, and may pose health risks and damage machinery and electronics. There may even be legal ordinances regulating and fining dust pollution, just as any other kind of pollution.
Control the “dustiness” of your soil with chemical additives for a long-term solution to dust pollution.
Erosion is not just an agricultural issue that affects plants and ecosystems - erosion can damage your construction, essentially washing the foundations right from under it until it collapses. Depending on the conditions of the terrain you’re building on, it may not be enough to have strong, stable soil - you may also need to take actions to protect it against erosion to ensure it will be there in the future. This is one reason why bitumen stabilization is so popular for road construction: bituminous materials waterproof the soil, and make erosion unlikely, to guarantee the road will not sink suddenly for lack of ground beneath it.
Protect the Environment
The old-school alternative to soil stabilization was to dig out the bad soil and replace it with aggregate. This is a very expensive method and an environmentally unsound one since it creates tons of CO2 through all the digging and mining and transportation, and then leaves the problem of disposing of the weak soil that was dug out.
Soil stabilization works with the soil that is there, and by adding relatively small quantities of certain additives it makes the soil stronger and more resistant. No mining, hardly any transportation, and no tonnes of soil to dispose of afterward - soil stabilization is definitely the more eco-friendly alternative.
The Right Soil
Minick Materials started transporting sand over 60 years ago, and we have gradually expanded into every aspect of the materials business. Soils and aggregates are no exception: we source and sell various types of soil, sand, fine and coarse aggregates, and our expert customer service staff is always happy to hear about your projects and help you get the soil you need for the job. From home improvement to commercial-scale building endeavors, we are prepared to assist you and make sure all your soil needs are satisfied.