Ananda Herath

Evaluation of Permeability of Superpav® Asphalt Mixtures

The presence of water in a pavement system is detrimental to its life. Permeable asphalt concrete pavement structures are vulnerable to stripping, which causes premature damage under heavy traffic. To assess the permeability of asphalt mixtures, a research study was conducted at the Louisiana Transportation Research Center (LTRC). Laboratory permeability tests were performed on field cores taken from 17 Superpave® projects in Louisiana. An LTRC-modified version of Karol-Warners falling-head permeameter was used to conduct the permeability test. A sensitivity analysis was performed to relate the permeability test results to mixture volumetric properties such as air void content, compaction effort, mixture gradation, and lift thickness. A statistical regression model was developed to predict the permeability of Superpave mixtures from the mixture volumetric properties. The model successfully predicted the coefficient of permeability of asphalt mixtures from a separate data set that was not included in the model development.

THE USE OF DYNAMIC CONE PENETROMETER TO PREDICT RESILIENT MODULUS OF SUBGRADE SOILS

The resilient modulus is used in the characterization of base and subgrade soils and in the design of pavement structures. The resilient modulus of subgrade soils can be estimated by using expensive and time-consuming laboratory test results or from overestimated backcalculated values from nondestructive test results. These limitations imply that the need of a simple and inexpensive insitu geotechnical test method to estimate the resilient modulus of subgrade soils. The dynamic cone penetration test is considered as a simple, rapid, and economical insitu test in geotechnical applications. However, the application of the dynamic cone penetration test in evaluating the resilient modulus of pavement subgrade soils is not well known. The objective of this paper is to develop correlations to predict the resilient m odulus of subgrade cohesive soils from the dynamic cone penetration test parameters, soil type, moisture content, and dry unit weight. Twelve laboratory -compacted large soil samples of two cohesive soil types and six test locations in two existing pavement s were used to perform the dynamic cone penetration tests. Laboratory resilient modulus and soil property tests were also performed. The preliminary estimation models were developed for the prediction of the resilient modulus of subgrade soils from the dynamic cone penetration test parameters, moisture content, dry unit weight, and other soil properties. The models predicted separate data sets that were not used in their development, indicating the success of the application of the dynamic cone penetration test in evaluating the resilient modulus of pavement subgrade soils.

Laboratory Evaluation of Untreated and Treated Pavement Base Materials: Repeated Load Permanent Deformation Test

Pavement performance is related to resilient modulus and permanent deformation properties of pavement materials, as well as other factors such as environmental and traffic conditions. Current resilient modulus test procedures and correlations do not fully describe permanent deformation properties. This limitation signifies the need for a permanent deformation test procedure for proper material characterization. The objective of this study was to evaluate resilient and permanent deformation properties of seven base materials with a proposed permanent deformation test that can provide both resilient modulus and permanent deformation properties. The base materials used were obtained from test sections recently constructed at the Louisiana Pavement Research Facility. These included crushed limestone, blended calcium sulfate, blended calcium sulfate treated with slag, blended calcium sulfate treated with fly ash, recycled asphalt pavement, foamed asphalt-treated 100% recycled asphalt pavement, and foamed aspha...

Evaluation of resilient modulus of subgrade soil by cone penetration test

Pavement design based on the resilient modulus of subgrade soil has been adopted by many transportation agencies following the recommendations of the AASHTO guide for design of pavement structures. Laboratory and field nondestructive tests are generally used to evaluate the resilient modulus of subgrade soil. These methods have shortcomings and limitations and are considered laborious, time-consuming, and expensive. The difficulties associated with the existing methods signify the need for a popular in situ technology for evaluating the resilient modulus of subgrade soil. Among other methods, the cone penetration test (CPT) is fast, simple, and economical and provides repeatable and reliable results. The results of a pilot investigation to assess the possibility of predicting the resilient modulus of subgrade soil from the CPT soundings are presented here. Field and laboratory testing programs were carried out on two types of cohesive soils at the Louisiana Transportation Research Center/Pavement Research Facility. Field tests consisted of CPT soundings using the 15-cm2 friction cone penetrometer and the 2-cm2 miniature friction cone penetrometer. Laboratory tests included the resilient modulus and physical properties of the investigated soils. The results of the miniature CPT were evaluated and compared with the soundings of the 15-cm2 cone at the same site. Both laboratory and field tests were analyzed. Based on statistical analyses, a model was proposed to estimate the resilient modulus from the CPT data and basic soil properties. Predicted values of the resilient modulus are consistent with laboratory measurements.

Characterization of Resilient Modulus of Coarse-Grained Materials Using the Intrusion Technology

This paper investigates the applicability of the cone penetration test in determining the resilient modulus of coarse-grained materials. Field and laboratory investigations were conducted at the sites of two pavement projects in Louisiana. Field tests consisted of continuous intrusion miniature cone penetration tests and soil sampling. Laboratory tests included the repeated load triaxial test and other tests for materials characterization. The test results were used to develop a correlation for predicting the resilient modulus of coarse-grained materials using the cone penetration test parameters and basic soil properties. Another laboratory investigation was conducted in order to investigate the effect of moisture content and unit weight on the cone penetration test parameters and resilient modulus. Test results were used to validate the model developed for predicting the resilient modulus. The resilient modulus values predicted were consistent with those obtained using the repeated load triaxial test.