MODULE 3-3 Patching With Bituminous Mixtures

Learning Objectives  Describe the conditions that require patching  Distinguish between hot-, cold-, and proprietary mix patching material  Describe patching materials properties  Describe procedures for throw and roll, semi-permanent, and automated patching

Introduction  Patching the existing pavement with bituminous materials  Extends the service life of the existing HMA  Used in the preparation of existing pavement prior to construction of an HMA overlay

Moderate Severity High Severity Patching Applications

Definitions – Bituminous Patching Materials  Cold-mix  Often used as temporary patches  Placed in stockpile and used over a period of time (emulsion binders)  Special open-graded mixes  Proprietary-mix  Cold mix with emulsified binder  Proprietary admixtures

Definitions – Bituminous Patching Materials  Hot-mix asphalt (HMA)  Placed immediately while hot  Standard dense graded HMA

Why Do We Patch?  Repair localized distress  Improve motorist safety  Reduce pavement roughness  Reduce the rate of deterioration  Repair pavement prior to overlay

Desirable Mix Properties Bituminous Patching  Stability  Adhesiveness  Resistance to stripping  Durability  Workability (cold-mix)  Storability (cold-mix)

Limitations and Effectiveness  Patching may not be appropriate for all applications  Temporary patches are temporary  Structural design may not be adequate  Principal problem may not be corrected

Limitations and Effectiveness  Bituminous patching is not recommended for permanent repair of rigid pavements  Hot-mix, full-depth patches provide maximum effectiveness  Not cost-effective when pavement is extensively deteriorated

Pavement Survey and Marking

Performance  Winter maintenance  “Throw and Roll” the most cost effective  Spray injection device also very efficient  Summer maintenance  Semi-permanent patch  Pennsylvania found to be 3X more cost effective on LCCA basis

Poor Conditions

Throw and Roll  Fill the hole with patching material  Compact the patch using truck tires  Verify that the compacted patch has some crown (between 3 and 6 mm).  Move on to the next pothole.  Open the repaired section to traffic as soon as maintenance workers and equipment are cleared from the area.

Semi-Permanent Patch  Mark patch boundaries  Cut boundaries  Clean and repair foundation  Apply tack coat  Fill the hole with patching material  Compact the patch  Cleanup

Automated Patching Equipment  Spray injection procedures  Blow debris from hole  Spray hole with binder for tack coat  Blow aggregate and binder into hole  Top off with a layer of uncoated aggregate to prevent tracking  May be rolled to improve smoothness

Automated Patching Equipment

What’s Wrong Here?

Review  What are the properties to look for in a patching material?  What are the major differences between hot-, cold-, and proprietary mix patching material?  Why do we patch?  What are appropriate applications of “throw and roll,” “semi-permanent,” and “automated” patching?

Key References  Wilson, T. P Long-Term Monitoring of Pavement Maintenance Materials Test Sites. FHWA-RD Federal Highway Administration, Washington, DC.  Wilson, T. P. and A. R. Romine Materials and Procedures for the Repair of Potholes in Asphalt-Surfaced Pavements-- Manual of Practice. FHWA-RD Federal Highway Administration, Washington, DC.