Highly Modified Hot Mix Asphalt on Bridge Decks Promises Longevity

Item #: 20230046

CONTACTS

Implementing Organization: Central Materials
Implementation Lead: Howard Anderson
Development Team:
- Howard Anderson (Central Materials) - Champion/Lead
- Lonnie Marchant (Region 2 Materials) - Member
- Cody Parker (Structures Preservation Engineer) - Structures Contact Design/Member

Article Written By: Eric Buell
Innovation Council Liaison: Eric Buell
Innovation Team Coordinator: Quinten Klingonsmith

STATUS

Implementation Date: June 1, 2023
Adoption Status: Implemented (further adoption advisable)
Adoptability Note: The more structures that HMHMA is tried on, the sooner UDOT will know the extent of its effectiveness in preserving bridge decks. This might be a good material for our new Trails Division to try out.

APPLIES TO

Topic: Maintenance Practices
Organization(s): Asset Management, Central Construction, Central Maintenance/Facilities Management, Central Materials, Central Preconstruction, Region 1, Region 2, Region 3, Region 4, Structures
Job Role(s): Construction Engineer, Materials Engineer, Program Manager, Program Specialist, Transportation Technician
Tags: active transportation, air transportation, highway transportation, capital productivity, infrastructure preservation, labor productivity, materials, economic benefits, value of time, products, materials, pavement, overlay, HMHMA, bridge deck, civil engineering, chemistry, materials science, construction, maintenance, structures, quality of life

PROBLEM

When an asphalt overlay is placed on a concrete bridge deck, the material used traditionally follows conventional HMA or SMA mix designs. But those materials are more suitable for roadway surfaces and are not ideal for bridge deck overlays because they allow water and chlorides to reach the top surface of the concrete bridge deck, which accelerates deterioration of the concrete and increases the probability of corrosion of the internal reinforcing steel. This can lead to potholes on the surface of the deck, as well as water leaking through the bridge onto structural components below. Waterproofing membranes can mitigate this effect, but are not always successful long-term solutions.

Although other materials are preferable for bridge decks, such as thin bonded polymer overlays and polyester concrete, existing roadway conditions and past work history often dictate the use of asphalt.

CHANGE

UDOT’s Central Materials group helped to develop a new special provision to allow the use of a Highly Modified Hot-Mix Asphalt (HMHMA) in roadway projects. This material (PG 76-34) uses an asphalt binder containing far more polymer than traditional binders. The result is an asphalt with fewer voids that is easier to compact and less water permeable.

Based on the success of this material in roadway projects (see innovation 20220065), it was recommended for use on bridge decks as an asphalt overlay wearing surface. It was also projected that this material would be easier to install and have better compaction.

RESULT

This new HMHMA material was used on two structures in Spring 2023 for a preservation project. It was also change-ordered into another bridge overlay project in the Ogden area.

Although bridge overlay applications of this product are new, it is hoped that by using this material in certain circumstances, the service life of both the concrete bridge deck and the asphalt overlay wearing surface will be extended beyond what is typically seen using traditional asphalt materials. This would help enhance safety, preserve Utah's bridges and reduce the number of projects needed to address asphalt deficiencies on bridge decks.

IMPACT

BETTER MOBILITY

Fewer potholes and bridge repairs mean less construction restrictions, closures, and delays

GOOD HEALTH

CONNECTED COMMUNITIES

STRONG ECONOMY

This mix promises great efficiencies, but until UDOT has more data, the extent of bridge deck-related savings is hard to measure
Potential cost savings in project and closure costs with reduced project frequency

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