How to Stabilize & Reclaim Roads
Before beginning a road base stabilization or full-depth reclamation project, it is important to evaluate the existing material and roadway configuration. Both processes are actually stabilization processes, and road base preparation considerations are similar.
If the road has deteriorated, it is important to understand why so specific remedial action can be taken to improve drainage, the depth of the road base, the quality and grading of underlying and adjacent soils, and other elements that can impact road load-bearing capacity and durability.
Consideration should also be given to the axle loads and traffic volume the road is likely to carry because this will influence the makeup of the new road base and the degree of compaction required, as well as the compaction process used. The quality of the existing aggregate should be evaluated to ensure that it contains the proper mixture of fine and coarse material. This analysis will determine if new aggregate is required to achieve the best stabilization results.
The Road Base Stabilization Process
In road base stabilization, the existing aggregate surface and underlying base are pulverized and mixed together to form a new base. Calcium chloride is added during the process to enhance stabilization. Successful stabilization depends on the quality of the gravel. Gravel should consist of a mixture of coarse materials and fines including clay or other materials that provide plasticity for natural binding characteristics.
Calcium chloride can be mixed with the road base material on the road work site or in a plant facility off site. For road mixing, trucks, a grader, a spreader, a water wagon, and a roller – or a travelling rotary mixer – are used to incorporate the calcium chloride into the gravel. Plant mixing, which is performed off-site in a more controlled environment, helps assure a more uniform mix, minimizing segregation of materials and providing greater control of moisture and gradation. Optimum calcium chloride application rates may vary depending on product and local road base, weather or other conditions. Ask the Experts.
Road Mixing – Coarse material is placed on the road and then fine material is added as a binder. After dry-mixing the two, the material is distributed in layers to prevent segregation. LIQUIDOW™ Technical Grade Calcium Chloride Solution is applied to the material using a pressurized system. Alternatively, a solid OxyChem calcium chloride product may be applied directly to the gravel mixture on the road followed by an application of water.
The aggregate and calcium chloride are mixed thoroughly by blade or travelling rotary mixer. Water is added as needed to assure optimum moisture levels. If the material is wet from rain, blading is required to aerate the mixture. Close attention to moisture levels is essential when compacting or rolling. Base material that is too dry may result in low density and poor stability, while base material that is too wet may build up under a roller. Next the material is bladed to the proper crown. For roads that will be paved, the crown should be shaped to a 2% slope, or ¼ inch per foot of horizontal fall from the center to the edge of the road. For a gravel road, the crown is shaped to a 4-6% slope, or ½ - ¾ inch per foot from the center to the edge of the road. The shaped base is rolled and compacted with a rubber tire or steel roller.
Plant Mixed – Plant-mixed base material is placed uniformly using a mechanical spreader. No more than six inches of loose aggregate should be placed in each layer. The base material should be compacted and shaped the same as for road-mixed material.
The Full-Depth Reclamation Process
There are two processes for full-depth reclamation, both of which result in a densely compacted road base with consistent and uniform strength.
Traditional full-depth reclamation with calcium chloride consists of six primary steps. First a reclaimer is used to pulverize the surface and road base to a specified depth. Next, LIQUIDOW™ calcium chloride solution is applied to the pulverized material using a truck with a spray bar. Then a second pass of the reclaimer thoroughly mixes the calcium chloride with road materials. The road is graded and shaped, followed by rolling and compaction with a vibratory roller. A surface application of calcium chloride is applied as a top dressing or fog seal on the final compacted surface.
An improved method of full-depth reclamation developed in the early 2000’s by Recon Construction Services of York, Pennsylvania, combines the first three steps of the traditional process using a specially modified reclaimer. This alternative method allows the reclamation process to be completed with less time and effort than with the traditional procedure. With the alternative process, the liquid calcium chloride is applied directly to the road material as it is reclaimed. Because the material is uniformly mixed during pulverization, the need for a second pass by the reclaimer is eliminated. Application rate is precisely controlled relative to ground speed and reclaiming depth to assure consistent stabilizing agent coverage. Application of a fog seal after shaping and compaction is optional depending on job specifications.
With both processes, it is important to reshape the road base, creating a parabolic crown to aid in proper drainage. Also important are proper shoulders and ditching to further aid in drainage. For full-depth reclamation, the total recommended application rate for LIQUIDOW 38% Solution is approximately one gallon per square yard.
Road Base Stabilization with Calcium Chloride