Road Base Stabilization Quality Assurance

With base stabilization, like most paving projects, the primary goal is to produce a strong, durable base course that is ready to receive a wearing surface. Inspectors can help achieve this goal by ensuring that the process is in accordance with the contract documents as follows: 

Mix Design: Verify representative samples were obtained throughout the project and that a mix design(s) was performed by a qualified lab resulting in a mixture that meets or exceeds the contract documents.

Surface Preparation: Walk or drive the entire pavement section to recieve the stabilized base for the day to ensure the surface has been properly prepared and that all pre-construction repairs have been performed. 

Acceptable Weather: Measure the air temperature and check conditions for anticipated heavy rainfall and freezing weather to determine if construction can start/continue.

Traffic Control: Verify that the proper traffic control is in place to keep the traveling public safe during construction.

Quality Equipment:

• Verify that the stabilizing agent system of the central plant mixer is equipped with a meter capable of recording the rate of flow and total amount of each liquid added to the stabilized base material
• Check the stabilized mixture for uniformity and homogeneity as it is discharged from the central plant mixer
• Verify that the haul trucks are of the required type, size, number and that tarps are working properly
• Verify that the on-board stabilizing agent/additive system of the reclaimer is equipped with a meter capable of recording the rate of flow and total amount of each liquid being added to the stabilized material.
• Verify that nozzles and spray bars of the reclaimer or central plant mixer are working properly and are not plugged.
• Verify that the bulk spreader is properly calibrated and is capable of accurately dispensing the required quantity of dry stabilizing agent/additive.
• Verify that motor graders used have cross slope indicators and are in accordance with the contract documents.
• Verify that the reclaimer is properly mixing the material.
• For foamed asphalt, verify that the proper half-life and expansion ratio is being maintained.
• Verify that the compaction equipment is of the required type, number and size and that scrapers and spray bars are properly working.

 Quality Workmanship:

• Verify that the stabilizing agent is being properly mixed.
• Verify that the mixing of water and stabilizing agent is adequate to ensure a homogenous, consistent blend throughout the treatment section.
• Monitor the amount of water introduced to maintain the specified range of optimum moisture content.
• Verify that the stabilized mixture is placed to the proper depth, grade and cross-slope. 
• Check that longitudinal and transverse joints are properly constructed.
• For cementitious stabilizing agents, verify that maximum mixing and compaction time frames are maintained.
• Verify that a control strip was established to determine the compaction procedures.
• Verify that the rolling procedure established in the control strip is followed and that the compacted density is within the specified range. 
• Verify that the completed section is trimmed to the proper grade and cross-slope.

Application Rates: Periodic checks should be made to verify that the amount of material being added to the stabilized base mixture is within allowable tolerances.

 Curing:

• Verify that the stabilized mixture can support the anticipated loads and will not impair material curing before opening the stabilized base section to light traffic.
• Verify that the completed stabilized base mixture is properly cured.