Lightweight Aggregate (LWA) for Use in Flexible Pavements

Chip Seal

This surface treatment is referred to by several names depending on the local area. The most common name is chip seal, however, other names like seal coat, surface treatment, oil and chip, and armor coat are also used.

Chip seals are made by spraying a layer of asphalt emulsion or hot liquid asphalt, covering it with aggregate and then rolling it. Only pneumatic rubber tire rollers are used with LWA.

Any chip seal application has some nonembedded loose stones that can be picked up by a tire and sent "flying". Damage to windshields, headlights and paint caused by "flying stones" is practically eliminated with LWA thus avoiding costly insurance claims and motorists complaints. The lightness of the LWA plus the higher wind resistance of the rough surface texture lowers the speed at impact. The resulting striking force is too small to do damage. The rough surface texture also bonds to the asphalt better so there are fewer "flying particles" in the first place.

Chip seal paving is a low cost durable surface treatment since it uses less materials and is not premixed at the asphalt plant or job site. This type of surface treatment is normally used on lowvolume rural roads or city streets. However, because of its high skid resistance, superior bonding capability and lack of vehicle damage, LWA chip seals have been used on high-speed/high volume city streets and highways such as the Autobahn in Germany and Interstate highways in the United States.

Lightweight chip seals offer the engineer an economical long lasting road surface that is safer to drive on and free of motorists complaints.

Plant Mix Seal Overlay

This application uses uniformly-sized aggregate, pre-blended in a drum mix plant using excess oil. The mixture is sent to the job site hot and is put down with a standard lay down machine. The finished road surface has an open-graded texture that is very durable with excellent drainage and skid resistance (see "X").

Hot Mix Surface Coarse

Hot mix, the premier asphalt surface alternative, is much denser and a tighter graded mixture that is usually a blend of LWA and normal weight aggregates. This material is shipped hot and laid down using conventional methods. LWA hot mixes have performed successfully on freeways with high truck traffic.

Micro-Surfacing

Micro-surfacings are useful in stopping the deterioration of an oxidized asphalt surface and the various types of problems that occur with weathering. Fine graded LWA works well in slurry seals and micro-surfacing, and improves skid resistance.

Cold Mix Pothole Patch

LWA is versatile in cold mix form because it has a tenacious bond with asphalt. Since it has a lower heat capacity than normal weight stone, LWA can be used in deep pothole patching applications.

"X" LWA plant mix seals are often used to overlay existing payment after extensive repairs have been made.

Plant mix seals are very effective on highvolume/high speed roadways and because of the open texture, they offer a quieter ride and much less water spray from moving vehicles especially trucks. This type of surface design is quieter because percussion cups are eliminated by the open surface.

Refractory Concretes

Norlite Aggregate is manufactured from Normanskill shale in the vicinity of Cohoes, New York. The lightweight aggregate is made by passing shale through a rotary kiln at a temperature of about 2000·F. At this temperature gases are formed inside the shale particles which cause expansion of the particles. The lightweight aggregate formed in this manner is then sorted into various gradations.

Norlite, in combination with high alumina cements, such as Lumnite or Ciment Fondu, will produce concretes which will withstand temperatures up to approximately 2000 · F.

There are many advantages of using Norlite as a refractory material, including: immediate availability-high thermal insulation-high structural strength-light weight-low expansion and contractionfuel savings, reduced maintenance and installation costs-ease and speed of new erection or repairs-abrasion resistance-minimum spalling, even under severe abuse.

Mix Proportions: Using mix proportions of 1:4 up to 1:6 will obviously vary the strength and weight. For instance a 1:6 mix has significantly lower strength but it also has somewhat lower unit weight. This reduced unit weight provides improved insulating properties. While the insulating properties of Norlite/Lumnite concrete are not as good as could be achieved by using some of the very light lightweight aggregates such as perlite or vermiculite, they combine good strength as well as corrosion and abrasion resistance with their insulating value and are used for lining stacks, ducts and breechings, as well as in and around process vessels in petroleum and petrochemical industries.

Shotcrete

Shotcrete is pneumatically applied portland cement mortar made with an intimate mixture of Norlite and either portland cement or Lumnite cement. The material is shot into place by means of compressed air. For fireproofing structural steel members, proportions shall be in the 1:4 range for cement/aggregate.

All mixes containing Norlite/Lumnite hydrate to produce an alumina gel in the concrete or mortar that make it resistant to the corrosive effects of many industrial wastes and certain mild acids. It is also highly resistant to sulfate attack. The Norlite aggregate as well as the cement must be resistant to corrosion.

Because of the rapid strength development of Norlite/Lumnite it is often used to produce concrete or grout for maintenance applications such as setting machinery, repairing industrial floors, etc., where downtime must be minimized. With a properly proportioned mix and good concrete construction practices, Norlite/Lumnite concrete can achieve a strength level in 24 hours which normally can only be obtained with a similarly proportioned Type 1 portland cement concrete in 28 days.

Norlite/Lumnite is also used to produce concrete for structural applications such as the construction of fire training towers, waste heat flues, chimneys, floors, ash bins, etc.

Since the hydration of Norlite/Lumnite mixes is an exothermic reaction, a rapid evolution of heat takes place during the first 24 hours. It is vital that this heat be dissipated and evaporation be prevented until the concrete is 24 hours old.

For additional information, contact the sales office at

Copyright 1998, Norlite Corporation, all rights reserved.