Uses of Hydrated Lime
Although hydrated lime has additional uses in industries such as agriculture and post-industrial processes, Mintek primarily uses it as an anti-strip agent in asphalt applications and to dry, modify and stabilize soils.
Hydrated lime is most commonly delivered via pneumatic trailer but is also available in super sacks.
What is high calcium hydrated lime?
High calcium hydrated lime is formed when quicklime is carefully mixed with water to form hydrated lime (Ca(OH)2), also known as hydrate, slaked lime or calcium hydroxide. The hydration process forms a very fine, white powder that is useful in a number of applications. In asphalt, hydrated lime is used as an anti-strip agent as it helps to stiffen binders.
What is the difference between lime and hydrated lime?
Hydrated lime is similar to quicklime in many aspects. For example, both can be effective at soil modification and stabilization. Additionally, both hydrated lime and quicklime can improve the engineering properties of soil. Such as, decreasing the plasticity index and increasing the strength and bearing capacity. Like quicklime, hydrated lime can be used for drying applications, but it has a reduced drying capacity as it has already chemically combined with water during the hydration process. Simply, hydrated lime is just not as efficient as quicklime as an increased dosage rate would be required to see the same benefits.
Another difference between the two is that there is a large variance in density. Hydrated lime is a very fine material. Quicklime, on the other hand, requires less storage because it has a higher bulk density. This means that the same amount of quicklime, by weight, will take up less volume resulting in reduced transportation costs and smaller storage facilities. The density of the material will also affect dosage rates when calculating by volume. Lab testing can eliminate guess work to determine dosage rates. The fine particle size associated with the lower unit weight of hydrated lime can also lead to dusting concerns.
Finally, two factors that are very important are cost and availability. As previously mentioned, hydrated lime is produced by further processing quicklime. This processing results in additional costs. Availability of hydrated lime is regional and can fluctuate depending on the demand of the product.
Is hydrated lime dangerous?
As with any chemical, high calcium hydrated lime should be handled with respect. Personal protective equipment is necessary to protect dust particles from entering the eyes, respiratory system and to keep the material off bare skin. In particular, gasketed safety glasses or goggles should be worn in dusty and/or windy conditions.
What is hydrated lime made of?
Hydrated lime is derived from quicklime, so to understand where hydrated lime comes from you must first understand where quicklime comes from. Quicklime is produced by subjecting limestone, or calcium carbonate (CaCO3), to high temperatures for a long period through a process known as calcining. During calcination, CO2 is driven off leaving only the oxide portion, calcium oxide, or quicklime. Quicklime can be further processed into hydrated lime by adding the right proportion of water and thoroughly agitating the mixture. This hydration process produces a low-density, dry, bulk powder that is high in purity.
What is hydrated lime used for?
High calcium hydrated lime is very useful in the construction market as an anti-strip agent in asphalt and to positively affect the engineering properties of soils through modification and stabilization. It is also used in a number of industrial applications, including water treatment and chemical manufacturing.
Anti-Strip for Asphalt
Hydrated lime, when used as an anti-strip for asphalt, stiffens the binders in asphalt therefore improving resistance to rutting and moisture damage. Additionally, hydrated lime provides greater tensile strength compared to untreated and liquid treated asphalts.
Improve compaction and stability of subgrade soils in construction applications through modification of the soil to extend pavement life. Modification also will reduce the potential to lost compaction because of shrink-swell.
Hydrated lime can be used to strengthen the subbase soils on a construction job site for better long-term strength & compaction. The strength associated with stabilization provides freeze-thaw resistance and has the potential to reduce the overall pavement thickness.
Material handling of Hydrated Lime
As with any chemical, handling of hydrated lime needs to be treated with respect. If handled properly, it is a very safe product. There are several precautions working with hydrated lime.
Calcium hydroxide (Ca(OH)2:
Available calcium oxide (CaO):
pH at 25°C:
~35 PCF #/ft3
Slightly soluble in water. Soluble in acids, glycerin and sugar solutions