On Tuesday, August 26, 2025, the MMCD Civil Committee recently held a session focused on finalizing the Recycled Aggregate Products (RAP) document. The objective was to consolidate technical updates, resolve outstanding issues, and refine specification language in preparation for the next phase of review. Below is a summary of key findings and decisions.
Key Outcomes and Specification Updates
1. Technical Clarifications and Corrections
- Plasticity Index: Led by Artem Zaporozhets, the group confirmed the plasticity index will remain at 6, as current data did not justify a reduction. This index reflects soil flexibility, a key factor in performance under load.
- Sieve Specifications: Minor typographical errors were corrected to ensure alignment with standard grading practices.
2. Updates to Contractor Requirements
- The requirement for soil examination has been removed to streamline procedures, while drain rock approval processes will remain in place.
- The term “Recycled Aggregate” has been updated to “Recycled Aggregate Material (RAM)” to reinforce clarity and ensure consistent understanding across jurisdictions.
- The Committee emphasized the importance of excluding low-strength or contaminated materials from RAM. Read Fenton underscored that poor-quality inputs undermine performance, and the updated language reflects a commitment to quality assurance.
3. CBR Testing and Performance Insights
- Reza Imaninasab presented findings from recent California Bearing Ratio (CBR) tests, a standard method for evaluating the load-bearing capacity of base and sub-base materials.
- Results showed that crushed stone dramatically increases CBR values, with some samples exceeding 60%.
- Two samples showed lower performance due to poor particle size distribution (gradation), highlighting the importance of proper mix control.
- A key concern raised was the absence of minimum CBR values in current specifications, which could lead to variability in project performance.
4. Defining Next Steps
- The Committee recognized the challenges of establishing uniform specifications for recycled materials, especially given varying municipal classifications.
- There was broad agreement on the need to:
- Introduce minimum CBR thresholds for base and sub-base layers.
- Refine language to reflect both environmental compliance and performance consistency.
- Balance cost-effectiveness with long-term durability in the use of recycled materials.
Why It Matters
These updates aim to improve clarity, material quality, and performance outcomes for MMCD users involved in design, tendering, inspection, and construction. As the industry increases its use of recycled materials, clear, enforceable standards are critical to ensuring reliable results across all project types.
Next Steps for Members
MMCD members can expect a revised draft of the RAP specification to be circulated in the coming weeks. Feedback will be welcomed during the upcoming review period
