The use of hydrated lime has shown a wide range of benefits in asphalt mixtures. To maximize these benefits, it is important that hydrated lime addition be consistent and well dispersed in the asphalt. Since hydrated lime is a fine powder, careful consideration to the design of storage and processing equipment is needed to optimize lime-modified asphalt performance in the field. Techniques used to mix hydrated lime into the asphalt cement can vary due to regional preferences and the types of equipment used. Hydrated lime can be added to aggregate on a belt or in a pug mill. This coated aggregate is either sent directly to the asphalt blending equipment or marinated in piles prior to use. Hydrated lime can also be added with the asphalt cement when it is mixed with aggregate. There are benefits and potential drawbacks with each method of mixing that must be considered. Selection of process equipment for asphalt plants should take into consideration the characteristics of hydrated lime. There are many options and the right process selection can be dependent on where the plant is located. Properly designed hydrated lime storage and handling systems result in smoother plant operation with consistent product quality.
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