The use of quicklime is one of the most common types of soil stabilization techniques used on construction sites. The properties of this chemical compound make it highly effective at changing the physical characteristics of soils, especially those with high moisture or heavy clay content. As widespread as its use is, however, many contractors may not understand what quicklime is, where it comes from, how it works, and what makes it so effective at transforming site conditions. Knowing the answers to these questions can be crucial in helping crews apply the right solution for their project’s specific needs.
Understanding What Quicklime Is
The scientific name of quicklime is calcium oxide, and it is the result of a chemical reaction in limestone that occurs at high temperatures. In its solid form, quicklime can be found as a greyish-white powder or in small pebble-sized clumps. Safety data sheets identify quicklime under CAS number 1305-78-8, and it also may be referred to as burnt lime, unslaked lime, or high-calcium quicklime.
How Quicklime is Produced
The production of quicklime begins with high-quality limestone, also known as calcium carbonate. This naturally occurring mineral is heated in a kiln to temperatures approaching 2,000 degrees Fahrenheit. This is done to burn away any carbon dioxide within the limestone, which leaves behind a reactive solid that is sold as quicklime.
Chemical Properties of Quicklime
Quicklime is valued in numerous industrial applications because of how it reacts to contact with water. When coming into contact with water, the quicklime hydrates and combines with the water to form calcium hydroxide. This is because quicklime’s crystalline structure is highly attractive to water molecules. It also undergoes an exothermic reaction, which means it releases heat as it rearranges its chemical bonds with water to form calcium hydroxide.
Hazards Associated with Quicklime
Both quicklime and the resulting calcium hydroxide from hydration are highly alkaline, which makes it hazardous to the skin and eyes. Contact with quicklime and its byproduct can cause severe irritation, chemical burns, and respiratory damage if the dust is inhaled. Because quicklime also contains crystalline silica, there also is a risk of carcinogenic effects without proper eye protection and breathing apparatus. Workers should always wear gloves, goggles, and respirators when working with or near quicklime for full protection.
How Quicklime is Used for Soil Modification and Stabilization
Many construction projects have to contend with site conditions that are less than ideal. Some of the most common issues crews face include excessively wet soils or soils that have higher clay content. These conditions can have a negative effect on the ground’s ability to support the weight of whatever will be built on top of it, leading to foundations settling over time and roadways buckling and sinking.
Using quicklime can help mitigate these issues. Using carefully calibrated spreaders to prevent uneven application, crews add a thin layer of quicklime to the surface of the soil, then mix it in immediately using reclaimers. After it’s applied, the quicklime reacts with the moisture in the soil, quickly reducing it and helping the soil to dry much faster. This means crews can compact the soil in a shorter timeframe than without quicklime.
Even after reacting with the water, quicklime continues to influence changes within the soil that make it more suitable for construction activities. It works to raise the pH level of the soils so much that certain components of it become soluble. This leads to the creation of more cementitious bonds between particles that become permanent, making the earth more capable of bearing heavy loads.
Comparing Quicklime to Other Chemical Stabilization Methods
In addition to quicklime, construction crews also have the option of using fly ash, lime kiln dust, or cement as additives to improve the mechanical properties of soil. Choosing the right approach is crucial for achieving the best results, which is why crews need to know what the issue with the soil is before starting any stabilization work.
In general, adding quicklime produces the best results when used on excessively wet soils or those with high clay content. Unlike cement, fly ash, or lime kiln dust, quicklime must be applied very carefully to ensure the proper ratio with the soil. It also may require the addition of more water to make sure it is fully hydrated. Although other additives don’t pose as much of a health risk as quicklime, it can take as much as twice the amount of these to achieve the same results.
Trust Rock Solid for Our Quicklime Expertise
As a leader in soil stabilization and modification, Rock Solid is a trusted partner who works with numerous construction companies across the country. Our knowledge when it comes to using quicklime is based in our long history of using this particular technique over many successful projects. Choosing to work with us means project leaders can gain the most stable, dependable subgrade to support their construction now and well into the future.
If you’d like to learn more about everything Rock Solid Stabilization & Reclamation, Inc., can do to benefit your next project, reach out and speak to a member of our knowledgeable team today to request a quote.