Let's Get Technical – June 2025

KY Microsurfacing Issues

In 2024, the following was included in House Bill 265 for Kentucky:

(26) Microsurfacing: It is the intent of the General Assembly that the Transportation Cabinet shall no longer use microsfurfacing by the year 2030.
 
Of course, this upset the microsurfacing supporters in the maintenance department along with the microsurfacing contractors. 

For some background, the state began the use of microsurfacing in 2008, but in my opinion, projects really got going with over the next 7 years. In 2020, the state moved to only using double micro courses.  Double micros are let head-to-head with thinlays. The state spends anywhere from $20-$30 million per year on these jobs.  It depends on the year if the bulk of the money goes to microsurfacing or thinlays.  

Every year or every couple of years, the maintenance department justifies the use of microsurfacing as a tool in the toolbox. They believe this data driven approach to the increased longevity of the road shows that they have been making the correct decision on treatments.  Now, that’s not to say that there haven't been a few issues along the way. There have been failures, but those that I am aware of have been due to base failures or other issues where the microsurfacing never should have been used.

In my discussions with the state, there doesn't seem to be an abundance of concern over this bill. They have slowed down micro lettings for 2025, but plan to pick up with some in the fall.   Additionally, microsurfacing is being looked at for improving some of the current friction issues in the state. The microsurfacing industry has been very active with Kentucky legislation explaining the benefits of their product.  It seems as if the two are doing what they can with the time left to change the legislature’s mind.

The only two things that really come up from the HMA industry are the cost and quality of the microsurfacing projects. In 2025, microsurfacing is expensive as it has ever been in the state and the HMA contractors believe that the thinlay will outlast the microsurfacing. The state has plans to help go after the cost by letting more projects together.  

My biggest concern through all of this is potential spread.  Even discussing this may cause movements in other states or further movements in KY.  

Microsurfacing in Ohio (On-Going Trial and Success)

The article “Micro Surfacing in Ohio” from AsphaltPro Magazine highlights a pavement preservation project led by the Ohio Department of Transportation (ODOT) at Maumee Bay State Park. Facing harsh freeze-thaw cycles and high moisture levels due to its proximity to Lake Erie, the park required a durable, low-maintenance solution. ODOT selected micro surfacing as a cost-effective treatment to protect the pavement from moisture and oxidation while improving surface friction for safety. The project involved sealing cracks, applying a tack coat, and using a spreader box to evenly apply the micro surfacing mixture.

The existing pavement, a 15-year-old hot mix asphalt surface, was still in good condition, making it an ideal candidate for micro surfacing. This aligns with best practices that recommend applying surface treatments before significant structural deterioration occurs. The treatment not only extended the pavement’s life but also minimized disruption to park visitors, which is crucial for a high-traffic recreational area.The article notes that micro surfacing, when applied correctly, can reduce greenhouse gas emissions by over 44% compared to traditional hot mix asphalt resurfacing.

Overall, the project demonstrates how micro surfacing can be a sustainable and efficient pavement preservation strategy, especially when applied at the right time. It also underscores the importance of product evaluation and performance monitoring in optimizing treatment outcomes for public infrastructure.

https://theasphaltpro.com/articles/micro-surfacing-in-ohio/

Charleston County Advances Pavement Preservation with Innovative Strategies

Charleston County, South Carolina continues to lead by example in the field of Pavement Preservation, embracing a range of forward-thinking, data-driven approaches to extend the life of its roadways and enhance surface performance. Among its current initiatives are the application of advanced surface treatments designed to improve durability and long-term value.

The county is currently conducting its fourth round of pavement condition assessments using a specialized data collection vehicle—building on previous evaluations, the most recent of which occurred in 2021. This ongoing data collection effort plays a critical role in measuring the effectiveness of various treatments over time, including those that undergo performance testing several years after application.

In addition to surface treatments, Charleston County is preparing to launch a new Hot In-Place Recycling (HIR) contract, expected to be bid by the end of the year and implemented in the upcoming construction season. The county is also exploring additional rehabilitation techniques such as Cold In-Place Recycling (CIR) and Cold Central Plant Recycling (CCPR), further diversifying its toolbox of sustainable pavement strategies.
Other innovative treatments being evaluated include double fiber-reinforced micro surfacing, scrub seals followed by cape seals, and various other combinations. These efforts reflect Charleston County’s commitment to exploring new technologies and refining its preservation practices.

A special acknowledgment goes to Mackenzie Kelley, Engineering Manager for Charleston County, whose leadership and dedication have been instrumental in driving these initiatives forward.
Through its commitment to innovation and continuous improvement, Charleston County is setting a strong example for agencies across the region—demonstrating how thoughtful planning, evaluation, and collaboration can lead to more resilient and cost-effective pavement solutions.

Microsurfacing: A 30-Year Review 

Overview:
Microsurfacing is a cold-applied, quick-set pavement preservation technique that has gained widespread acceptance over the last 30 years. Used to address surface wear, fill ruts, and extend pavement life, it offers a cost-effective and sustainable maintenance strategy. This review paper synthesizes three decades of field application, research, and evolving practices.

Core Benefits:
- Performance Enhancement: Microsurfacing restores surface texture, improves skid resistance, and corrects minor surface defects. Rut-filling capabilities improve ride quality significantly [7].
- Cost Efficiency: As a preventive maintenance tool, microsurfacing delays costly rehabilitation or reconstruction. Lifecycle analysis shows significant return on investment [9].
- Minimal Traffic Disruption: Fast cure times allow traffic to return within hours, reducing user delay costs.
- Environmental Sustainability: Cold-mix application reduces energy consumption and emissions compared to hot mix asphalt [6].

Challenges Identified:
- Environmental Sensitivity: Application success is highly dependent on temperature, humidity, and timing. Poor conditions can delay curing and affect adhesion [18].
- Inconsistent Field Results: Early wear, delamination, or poor aesthetics can result from inconsistent materials, inadequate contractor quality control, or improper mix designs [19].
- Data Gaps: A shortage of long-term, multi-climate performance data limits lifecycle modeling and predictive maintenance planning [14].

Innovation & Research Trends:
Ongoing efforts focus on:
- Enhanced mix designs for performance reliability [7].
- Standardization of test methods (e.g., Wet Track Abrasion Test).
- Integration of recycled materials for sustainability.
- Development of performance-based specifications to reduce variability [19].

Conclusion:
Microsurfacing remains a key tool in pavement preservation, balancing performance, cost, and environmental stewardship. While its advantages are well-documented, continued progress hinges on improved data collection, standardization, and adaptive innovations.

Key References:
- [6] Kandhal & Mallick (1997): Emissions study favoring cold-applied methods.
- [7] Shuler et al. (2011): Mix design and performance improvements.
- [9] Galehouse et al. (2003): Cost-effectiveness in preventive maintenance.
- [14] Button & Lytton (2007): Need for long-term performance data.
- [18] Andriescu et al. (2006): Environmental timing effects on performance.
- [19] Morian et al. (2012): Performance-based application guidelines and field challenges.