Treating aggregate with lime for use in asphalt concrete is done in different ways. California Department of Transportation (CALTRANS) has very specific requirements.
Wilderness Technology, Inc. manufactures controls for these different lime treatment systems. Correct proportioning of the lime and water to the aggregate is important to not let the moisture get any higher than necessary, cutting into your production of asphalt.
Continuous Lime slurry marination systems for use in California must meet CALTRANS requirements. System usually has a lime silo with a weighting device, CALTRANS does not allow Loss-in-weight devices. We use a scale belt. We are presently working on a scale auger to weigh the lime to CALTRANS specifications. The lime is added to a mixer with the water which must be metered also, generally this is a three to one mixture of water to lime, forming the slurry. The aggregate is weighed on a belt scale with controlled feed and runs into a pugmill for mixing with the slurry. The slurry is metered into the pugmill with the aggregate and mixed. The treated aggregate is stacked in a pile and must marinate a specified time. There are data log requirements for the metering values of slurry and aggregate. All of this is accomplished by the control system automatically.
Dry lime marination is similar without the slurry. The mixer is not used or the slurry metering device. The water is still metered in but not at a 3 to 1 ratio, the water amount is related to the surface saturated number for the aggregate. Water is added to the pugmill with the lime and aggregate and mixed. Mixed, stacked and left in a pile to marinate for a specified time.
Dry lime in-line adds the specified percentage of lime to the aggregate as its goes to the dryer (drum). The pugmill is added in line with your cold feed system. Lime and aggregate goes into a pugmill and has a specified amount of water added. After mixing the aggregate goes to the drum for drying. Correctly controlling the proportions of lime and water is important to not impact your production throughput.
We can make you a complete system or integrate parts that you may already have into the necessary system. Our controller has been retrofitted to existing lime plants also. If you have a system with a weight loss measuring device that needs to be legal for CALTRANS, we can provide one.
This is a typical control panel for a Lime Treatment System