Date of Award

Spring 2008

Document Type

Thesis

Department

Mathematics, Engineering & Computer Science

First Advisor

John Scharf

Second Advisor

Cheryl Conover

Third Advisor

Terry Mullen

Abstract

In the past 20 years, highway agencies began rehabilitating pavements using newer technologies such as pavement pulverization. On some roadways pulverization can be more cost effective and more environmentally friendly than pavement reconstruction. Pavement pulverization consists of pulverizing and blending the full thickness of the plant mix surfacing and a predetermined portion of the crushed base course to provide a homogeneous base material. The pulverized base course is then overlaid with new plant mix surfacing (PMS) resulting in a new roadway [11]. Sometimes pulverization is used to build an In-Place Cement Treated Base in which the base acts like a weak concrete layer The Montana Department of Transportation has used pulverization on 62 projects starting in 1988. The purpose of this study is to analyze the actual performance of pulverized projects on Montana’s roadways. The evaluation will be used to determine how well pulverized pavements are performing and to compare the performance of these pavements to MDT’s conventional flexible pavements. A comprehensive investigation of pulverization projects was conducted. Twenty-one roads were studied. The roads were constructed from 1989 to 2001 at various locations throughout Montana. MDT’s Pavement Management database was used to determine the conditions of the pulverized pavements. Miscellaneous cracking index (MCI), rutting index, ride index, alligator cracking index (ACI), and overall performance index (OPI) were collected and plotted against the pavement age. The pavement age, traffic level, subgrade type, project location, annual precipitation, plant mix surfacing, and the Recycled Asphalt Pavement (RAP) to crushed based course (CBC) ratio were analyzed to identify factors which contribute to the performance of pulverized roads. Multiple linear regression analyses were conducted to describe the relationship between these factors and the pavement. The pulverized pavements were also compared to the performance of adjacent non-pulverized pavement and the performance of Montana’s overall road system. It was found that among the characteristics in this study, the RAP/CAC ratio, age, annual precipitation, and project location were the most important factors affecting the performance of pulverized roadways. The projects that did not perform as well are located in the Missoula District. Also the projects that received more than 19 inches of precipitation a year did not perform as well. The RAP/CAC ratio that results in poorer performance is a ratio greater than 75%. It can be concluded that pulverized roads in Montana are performing satisfactorily and equivalent to non-pulverized pavements. It is recommended that these projects be evaluated again in years to come. Based on cost and performance it is also recommended that the MDT continues to build pulverized pavements.

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