Lime Stabilization Technique For Soil Improvement

When simply adjusting the location of a soil or adding different soils together isn’t a good enough option, soil can then be altered chemically to make them inherently stronger in terms of durability. The use of chemicals to stabilize soils are known to be widely used in the construction of many types of projects, including roads, airports, embankments, and canal linings. By mixing chemicals with clayey soils, they are able to improve a soil’s workability, strength, stiffness, swelling characteristics, and bearing capacity. The engineering properties of a chemically stabilized soil either show their improved changes immediately or they gradually change through chemical reactions between the soil and the stabilizing agent added to its composition. By using these stabilizers, the pores inside the soil that would otherwise have been filled with water instead get filled with new materials that fill these gaps. This closing of pores helps all of the chemical properties group together as the substance changes over time and create a more solidified soil.

One of the more traditional as well as popular chemical options to add to soil is lime, which then creates a process called lime stabilization. Lime stabilization offers a more economical means of improving clay-like soils by adding lime to the groundwork without needing to pay for aggregates. This addition helps increase the stability of a soil by reducing their swelling potential, meaning it will not expand exponentially over time and end up damaged due to moisture. It also enhances a number of other engineering properties such as strength, resilience, optimum water content, and shrinkage limit. Changing these weaknesses allow the soil to resist being permanently deformed due to fatigue or fractures, which helps increase the soil’s maximum dry density. However, when applying lime to clay-like soils, it is important to note what kind of clay is being manipulated. The two types of clay usually encountered on building projects are montmorillonite clays and kaolinite clays.

Kaolinitic soils are commonly found in areas that have high recorded levels of precipitation. From a chemist point-of-view, kaolinite particles are comprised of a sequence of hexagonally-formed layers bound together by hydrogen bonds. These hydrogen bonds make it so that water and cations are not present among the structural layers of kaolinite, meaning that kaolinitic soils tends to exhibit lower plasticity and lower tendencies for swelling than most other clay-like minerals. Since lime has the ability to make soils less prone to swelling, the addition of it will help decrease plasticity levels in these particular soils even greater as it bonds with the kaolinite particles to make the overall soil more workable. Montmorillonite, on the other hand, is a mineral that is even more prone to swelling than most clay-like minerals due to its molecular structure being rather spread out in composition. In other words, unlike the previous type of soil where water and cations are repelled from the outer structures, the water molecules and exchangeable cations in montmorillonite are readily absorbed among its interlayer areas. Between this and the high amounts of silica also contained within its genetic makeup, the end result of adding water to this soil is swelling factors that correlate to highly plastic clays. Because of this, montmorillonite is sometimes used in petroleum engineering as a component of drilling into mud, which makes mud slurry and helps keep the drill bit cool as it removes drilled solids from the hollowed-out ground.

So which soil benefits more from having lime added to it? Geographically speaking, kaolinite soils benefit from hot, humid regions that allow the ground to leach off of surrounding organic nutrients due to weathering. These humid regions also produce high amounts of rainfall that the soils can easily drain due to its repelling nature, making them rather difficult to work with in terms of stability. Montmorillonite soils, by comparison, prefer cooler climates accompanied by somewhat damp lands that make it difficult to drain and clump amidst their surroundings. This clumping nature is not perfectly stable in comparison to sturdy materials like rocks, but it is a strong enough quality which many engineers find to be favorable. Therefore, even though both soils can benefit from being made into stronger soils, the addition of lime benefits kaolinitic soils more than montmorillonitric soils. As added proof, when both soils were tested in a laboratory, results show that the reactions between lime with kaolinitic clay soils form much stronger bonds than those formed by the reaction of lime with montmorillonitric soils.