Although hydrated lime (HL) has been known for a long time, in the 1970s in the United States, when moisture and frost damage became one of the most urgent asphalt pavement failure modes of that time, it gained great interest as an asphalt additive.
Due to its widespread use over the last 40 years, HL or hydrated lime is known to be more than a moisture damage additive: it is an "active filler" that also reduces the chemical aging of bitumen and makes mastic more durable than a mineral filler. Normal hardens at normal temperature. These properties affect durability, and HL is now seen as an additive that increases the durability of asphalt mixtures. Also, these factors affect the sale of bitumen and the daily price of exported bitumen.
This article is a review of the basics of HL effect on asphalt mixtures. The reasons for its effectiveness lie in strong interactions between aggregate and bitumen and a combination of four mechanisms, two on aggregate and two on bitumen. HL modifies the surface properties of the aggregate and makes it possible to create a more favorable surface and roughness combination for bitumen adhesion. Then, HL can treat the existing clay particles stuck to the aggregate surface and prevent their destructive effect on the mix.
Also, HL chemically reacts with bitumen acids, which in turn slows down the aging kinetics and neutralizes the effect of "bad" adhesion promoters that were initially present in the bitumen, increasing the moisture resistance of the mixture. Gives. Finally, the high porosity of HL explains its stiffening effect above room temperature.
Recent studies confirm that lime also has other important benefits:
It hardens the binder and HMA against deterioration.
Increases toughness and resistance to fracture growth at low temperatures.
Lime changes the oxidation chemistry in the adhesive to reduce age hardening. And
Lime changes moisture to improve stability and durability.
Lime is also useful for upgrading marginal aggregates. In addition to the chemical effects that lime provides to reduce stripping potential and the aging effect of oxidative hardening, the "filler effect" of lime improves corrosion resistance at high temperatures and increases fracture toughness at low temperatures.
Hydrated lime multi-purpose asphalt modifier
As many state highway officials have found, modifications made to HMA with hydrated lime add years to the life of the pavement. These changes can reduce hardening, deterioration, cracking and aging. Hydrated lime significantly improves each of these properties when used alone and also works well in combination with polymeric additives, helping to create pavement systems that will last for years to the highest expectations. it works.
A superior anti-stripping agent
Hardening occurs when the bond between the asphalt cement and the aggregate breaks down due to the presence of moisture and the adhesive separates from the aggregate. Certain types of aggregates are particularly susceptible to cutting. Weather features such as heat, heavy rains, freeze/thaw cycles and traffic play a major role in deprivation. Hydrated lime is the most effective anti-stripping agent available and is widely specified by governments with serious stripping problems.
When lime is added to the hot mix, it reacts with the aggregates and strengthens the bond between the bitumen and the stone. At the same time as the aggregate is refined, the lime also reacts with the asphalt itself. Lime reacts with highly polar molecules that would otherwise react in the compound to form water-soluble soaps that cause dissociation. When these molecules react with lime, they form insoluble salts that no longer absorb water. In addition, the dispersion of fine particles of hydrated lime throughout the mixture makes it stiffer and stiffer, reducing the possibility of mechanical breakage of the bond between the asphalt cement and the aggregate, even in the absence of water.
Improves hardness and reduces decay
Skidding is the permanent deformation of asphalt that occurs when the tension is excessive. The ability of hydrated lime to create a stiffer and more resistant to deterioration asphalt mixture is a reflection of its superior performance as an active mineral filler. Unlike many mineral fillers, lime is chemically active rather than inert. It reacts with the bitumen and removes undesirable components at the same time as its fine particles are dispersed throughout the mixture, making the coating more resistant to deterioration and cracking.
Hardening caused by the addition of hydrated lime can increase the performance grade (PG) of asphalt cement. Depending on the amount of lime used (generally 10-20% by weight of asphalt), the PG grade may increase by a full grade. In other words, PG 64-22 can be increased to PG 70-22. The addition of lime does not make this composition more brittle at low temperatures. At low temperatures, hydrated lime becomes less chemically active and behaves like other inert fillers.
Reduces oxidation and aging
Oxidation and aging occur over time, causing a brittle pavement. Polar molecules react with the environment, dissociate and contribute to pavement deterioration. Addition of hydrated lime to asphalt cements reduces oxidation and aging of asphalt. This is the result of chemical reactions that occur between the calcium hydroxide and the highly polar molecules in the bitumen. Hydrated lime combines with polar molecules when added to asphalt, and therefore, polar molecules do not react with the environment. As a result, asphalt cement is flexible and protected from brittle cracking for years without the use of lime.
Reduces cracking
Cracks can be caused by reasons other than aging, such as fatigue and low temperatures. Hydrated lime also reduces asphalt cracking from these reasons. Although stiffer asphalt generally causes more cracking, the addition of lime improves fatigue properties and reduces cracking. Cracking often occurs due to the formation of small cracks. These micro-cracks are intercepted and deflected by hydrated lime particles. Lime reduces cracking more than passive fillers due to the reaction between lime and polar molecules in asphalt cement, which increases the effective volume of lime particles by enclosing them in large organic chains. As a result, lime particles are better able to intercept and deflect micro-cracks, preventing them from growing together into large cracks that can cause pavement failure.
ATDM CO is a reputable manufacturer and exporter of Bitumen 60/70 and Bitumen 80/100. We specialize in offering high-quality bitumen products in various packaging options, including drums, bags, and bulk quantities. Our product line consists of three distinct quality grades: premium, second, and third types. Each grade is produced with meticulous attention to detail, utilizing advanced facilities and processes.
Our diverse range of options is designed to cater to the specific needs and volume requirements of our customers. Whether you require a smaller quantity for a specific project or a larger bulk order, we have the flexibility to accommodate your demands.
At ATDM CO, we prioritize product quality, reliability, and customer satisfaction. Our bitumen 60/70 is manufactured to meet international standards, ensuring optimal performance and durability in various applications. Currently, we have supplies in three countries of the United Arab Emirates (Dubai), Panama and Singapore are available. We take pride in delivering exceptional products that meet the diverse needs of our valued customers, both domestically and internationally.