Civil Engineering ETDs

Publication Date

2-14-2014

Abstract

In the past, numerous studies have been conducted on the topics of moisture damage and permeability, but very few studies have correlated permeability with moisture damage in Asphalt Concrete (AC). This study evaluates whether such a relation exists or not. In addition, correlations of permeability with AC mix volumetrics and pores are evaluated. Also, correlation of laboratory permeability with field permeability is examined. In this study, a field survey is conducted to identify a set of eight pavements (bad) that are known to suffer from moisture damage and a set of eight pavements (good) that do not exhibit moisture damage. Field permeability testing is conducted on those 16 pavements. Results show that good performing pavements have very low (field) permeability compared to the bad performing pavements, which was expected. Field coring is conducted and cores are collected from all 16 pavement sections. Next, laboratory permeability testing is conducted on the field cores using a falling head permeameter. Based on laboratory permeability values, the good pavement sections exhibit smaller permeability than the bad performing sections. To this end, moisture damage potential of field cores is determined in the laboratory using Moisture Induced Sensitivity Test (MIST) device and the AASHTO T 283 method. In MIST method, a sample is wet conditioned using repeated increase and decrease of pore pressure inside the saturated pores of AC sample. In the AASHTO T 283 method, a sample is wet conditioned using vacuum saturation and then subjected to one cycle of freeze-thaw. A set of three wet and three dry conditioned samples are tested for indirect tensile strength and Tensile Strength Ratio (TSR) of wet to dry sample sets is determined. It is shown that both MIST and the AASHTO T 283 yield TSR values of less than 1.0, which means moisture damage occurred by both conditioning methods. Based on the AASHTO T 283 data, when moisture damage is correlated with laboratory permeability, the AASHTO T 283 shows a good correlation but MIST shows a poor correlation. Correlations of field permeability with the AASHTO T 283 and MIST are found to be poor. Mix volumetrics (e.g., gradation, porosity, binder content) tests are performed on field cores. Gradation data is plotted on a 0.45 power curve. Based on the power curve plot, it is shown that a mix gradation that passes near to the maximum density line have low permeabilities and moisture damage potentials. It is known that an AC sample contains 3 types of pore: permeable, dead-end, and isolated pores. In this study, permeable pore is determined using a tracer test method, a concept borrowed from soil permeability testing. Dead-end and isolated pores are also determined using a CoreLok device. It is shown that permeable pores have a better correlation with permeability than the effective pore, which is defined as the sum of permeable and dead-end pores. In this study, an attempt is made to correlate laboratory permeability with field permeability. Laboratory permeability does not have any correlation with the field permeability. This may be due to the fact that field permeability is affected by several factors such as 3D flow in the field, Open Graded Friction Coarse (OGFC), tack coats. To this end, an analytical model is developed to predict field permeability from laboratory permeability. Model permeability is found to be higher than the laboratory permeability. Because the model considers lateral and vertical direction flows whereas laboratory permeability test considers only vertical flow. It is shown that the model permeability is less than the field permeability for pavements with OGFC and more than the field permeability for pavements without OGFC. Therefore, a shift factor is developed to match the model permeability with the field permeability.

Keywords

Permeability, Damage, TSR, Porosity, Tracer

Sponsors

New Mexico Department of Transportation

Document Type

Thesis

Language

English

Degree Name

Civil Engineering

Level of Degree

Masters

Department Name

Civil Engineering

First Committee Member (Chair)

Ng, Percy

Second Committee Member

Stone, Mark

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