Introduction

The Georgia Department of Transportation (GDOT) mandates the use of volumetric concrete mixers for Latex Modified Concrete (LMC) bridge overlays to ensure strict quality control, durability, and optimal performance of bridge decks. This requirement is outlined in the GDOT 2021 Standard Specifications.

As a leading ready-mix volumetric company based in Douglasville, GA, serving the Metro Atlanta area, we understand the importance of adhering to GDOT requirements and delivering high-quality LMC for bridge overlays. In this blog, we’ll explore why GDOT requires volumetric trucks, the advantages of volumetric mixing, and why traditional drum mixers are not permitted for LMC applications.

What is Latex Modified Concrete (LMC)?

Latex Modified Concrete (LMC) is a high-performance overlay material used to extend the lifespan of bridges. It consists of:

• Portland cement
• Fine and coarse aggregates
• Water
• Latex polymer admixture

The latex additive enhances flexibility, bond strength, and water resistance, making it ideal for bridge deck overlays where resistance to cracking, de-icing salts, and freeze-thaw cycles is crucial.

GDOT’s Requirement for Volumetric Mixers

According to the GDOT 2021 Standard Specifications, Section 500—Concrete Structures, volumetric proportioning requires that the operator be certified by the Office of Materials and Research.

This specification underscores GDOT’s commitment to ensuring that LMC is mixed and placed under strict quality control standards, enhancing durability, bond strength, and long-term performance on bridge decks.

Why GDOT Requires Volumetric Mixers for LMC Overlays

GDOT mandates volumetric concrete mixers for LMC bridge overlays due to the precise mixing capabilities required to maintain quality, consistency, and workability. Here’s why:

1. On-Demand Fresh Mixing

• Volumetric trucks mix concrete on-site, ensuring that LMC remains fresh throughout placement.
• Traditional drum mixers batch concrete at the plant, meaning the mix can degrade during transport.

2. Precise Control Over Water and Latex Content

• LMC requires strict water-to-cement ratio control, which volumetric mixers can adjust in real-time.
• Drum trucks cannot modify mix proportions on-site, leading to inconsistent quality.

3. Reduced Waste & Improved Efficiency

• With volumetric mixers, only the needed amount is mixed, eliminating excess waste.
• Drum mixers must batch in bulk, increasing waste if delays occur.

4. Continuous Pouring Without Set Time Issues

• LMC has a short working window, requiring continuous placement for proper bond strength.
• Drum mixers risk premature setting, causing issues with overlay bonding and performance.

5. Compliance with GDOT and ASTM Standards

• GDOT follows ASTM C685 for volumetric batching, recognized for high-quality, controlled mix production.
• LMC overlays require uniform dispersion of latex admixture, best achieved with volumetric mixers.

Why Traditional Drum Mixers Are NOT Allowed for LMC

GDOT does not permit traditional ready-mix drum trucks for LMC overlays because:

• Inconsistent mixing – The latex can separate during transport.
• Short working time – Concrete can begin to set before placement.
• No real-time adjustments – Water, cement, or admixtures cannot be modified on-site.

These limitations reduce LMC’s durability and bonding ability, making it unsuitable for critical bridge repairs.

Final Thoughts: The GDOT Standard for LMC Bridge Overlays

By requiring volumetric mixers for LMC overlays, GDOT ensures:

✔ Consistent, high-quality concrete ✔ Stronger bond and better durability

✔ Reduced material waste and cost efficiency ✔ Compliance with ACI, ASTM, and GDOT standards

As a trusted volumetric concrete provider in Metro Atlanta based in Douglasville Georgia, we ensure that our LMC meets GDOT specifications and delivers long-lasting infrastructure repairs. If you’re a contractor working on GDOT bridge projects, ensure your LMC mix is delivered via volumetric truck—it’s the only way to meet state-mandated quality requirements and guarantee superior performance.