United States Department of Transportation
i
Establishment of Best Practices for Construction and Design of Cement-Treated Materials
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2020-10-01
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[PDF-13.55 MB]
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Edition:Sept. 1, 2017 – Aug. 31, 2020
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Abstract:Cementitious stabilization of granular soils has been proven to be an economically viable option for sustainable construction and rehabilitation of pavement structures. The absence of a harmonized and rapid turnaround laboratory mixture design procedure, coupled with construction and inspection guidelines that need improvement have resulted in an ongoing challenge for TxDOT, contractors, and users of the transportation facilities. In addition, due to the lack of field data and practical laboratory tests in the past, the fatigue performance models in the Texas Mechanistic Empirical Flexible Pavement Design System (TxME) have never been verified nor calibrated. Therefore, the main objective of this study was twofold: provide an update to the current mixture design specification based on comprehensive laboratory testing and develop and calibrate a new generation of fatigue performance model that accounts for strength as well as shrinkage cracking potential of cement treated materials. To accomplish these objectives, current practices for mixture design and construction of cement treated base, subbase and subgrade soils were documented. This information then served as the basis for the selection of the type and sources of base aggregates and subgrade soils for inclusion in the experiment matrix of the project. Eight different aggregate base materials including multiple sources of limestone, siliceous gravel, reclaimed concrete aggregate, full depth reclamation materials, and reclaimed asphalt pavement, as well as seven different subgrade soils with unique characteristics were incorporated in this research effort. All permutations of the experimental design were prepared with different levels of stabilizer content to cover a wide spectrum of treatments from light stabilization to heavily stabilized systems. This research also provided two alternative moisture susceptibility procedures to quantify the loss of orthogonal strength properties of cement treated virgin and reclaimed materials due to moisture intrusion. More than 3,000 specimens, were prepared, and subjected to various mechanical and physio-chemical laboratory tests to characterize the strength, resilient properties, and permanent deformation potential, clay activity, moisture adsorption potential, as well as other properties of cement treated systems. Microstructural analysis of the cement treated specimen using X-ray computed tomography was instrumental to provide the basis for using the gyratory compactor in lieu of the traditional impact hammer for laboratory specimen preparation. The trend analysis of the laboratory results, statistical reliability and repeatability analysis, practicality of test methods, and operator friendliness were the contributing factors to draft the update to the cement treatment specification. In addition to the laboratory efforts, a new generation of fatigue performance models were developed and calibrated in this study. The model incorporated indirect diametrical tensile (IDT) strength and shrinkage strain to account for the cracking potential in the cement treated layer due to overly rigid matrices. A comprehensive database of pavement profiles and material properties were developed using field-based nondestructive testing such as Falling weight deflectometer, ground penetrating radar, and deployment of Portable WIN (P-WIM) for traffic characterization in this study. The database was instrumental for the calibration of a newly developed fatigue performance model for flexible pavement structures with cement treated layers.
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