Strength Criteria for Cement-Treated Large-Size Macadam Base to Control Fatigue Failure.

Area of Science:

• Civil Engineering
• Materials Science
• Geotechnical Engineering

Background:

• Super-large-particle-size cement-stabilized macadam (CTB-50) utilizes low cement dosage and a dense structure for reduced base course cracking and costs.
• Existing research lacks strength design criteria and specifications for CTB-50, hindering its practical application.
• Understanding CTB-50 mechanical properties and stress under vehicle loading is crucial for pavement design.

Purpose of the Study:

• To investigate the mechanical properties of CTB-50 under construction vehicle loading.
• To propose strength criteria for CTB-50 to prevent ultimate failure during construction and fatigue failure during service.
• To establish fatigue damage control criteria for CTB-50.

Main Methods:

• Utilized the vertical vibration compaction method (VCM) for specimen preparation.
• Applied Miner's fatigue cumulative theory to analyze repeated loading effects.
• Compared VCM-prepared specimen strengths with static-pressing methods and field core samples.

Main Results:

• VCM-prepared CTB-50 specimens showed approximately 90% of field core sample 7-day compressive strength, significantly higher than static-pressing methods (<70%).
• Mechanical strengths of VCM-prepared specimens highly correlated with on-site core samples.
• Proposed specific 7-day splitting and compressive strength thresholds for base and sub-base courses.

Conclusions:

• The VCM is a suitable method for preparing CTB-50 specimens that accurately reflect field performance.
• Established strength criteria effectively control both ultimate and fatigue failures in CTB-50 pavements.
• Recommended 7-day strengths: base course >0.77 MPa (splitting) & 7.6 MPa (compressive); sub-base course >0.71 MPa (splitting) & 7.0 MPa (compressive).