Pavements were designed and constructed at two sites in southern Wisconsin employing a layer stabilized in situ with fly ash. One pavement is for a residential subdivision. The other is a test section located in a secondary highway that was recently reconstructed. A control test section employing a conventional cut-and-fill approach was also constructed in the secondary highway. Fly ash was used to increase the strength and stiffness of the fine-grained subgrade at both sites, which was soft prior to stabilization. Pavements at both sites were designed using the 1993 AASHTO method for flexible pavements so that their structural number would be equivalent to that of the conventional pavement originally called for in the design. Measurements of California bearing ratio (CBR) and resilient modulus (Mr) were used with the correlation charts for granular subbase materials in the AASHTO manual to define layer coefficients for the stabilized layers. Tests were also conducted on specimens collected during construction to verify that the in situ mixture had similar properties as anticipated during design. The pavement at one of the sites is being monitored seasonally using a falling weight deflectometer and pavement distress surveys. The monitoring program has indicated that the pavements constructed with fly ash stabilized layers provide comparable stiffness to the conventional pavements employing a cut-and-fill approach. No signs of distress have been observed in the pavements constructed with a stabilized layer.
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