Effect of prolonged heating on the Asphalt-Aggregate Bond Strength of HMA containing Liquid Anti-strip Additives

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Title: Effect of prolonged heating on the Asphalt-Aggregate Bond Strength of HMA containing Liquid Anti-strip Additives
Author: Mandapaka, Venkata Lakshman Murthy
Advisors: Akhtarhusein A. Tayebali, Committee Chair
Detlef Knappe, Committee Co-Chair
N. Paul Khosla, Committee Member
Abstract: ABSTRACT Venkata Lakshman Mandapaka. Effect of prolonged heating on the Asphalt-Aggregate Bond Strength of HMA containing Liquid Anti-strip Additives (Under the direction of Dr. A.A. Tayebali and Dr. Detlef Knappe) In this study, an attempt was made to determine the effect of prolonged heating on the bond strength between aggregate and asphalt that contained anti-strip additive (LOF 6500 of various percentages). A series of tests, namely Tensile Strength Ratio test (TSR), Contact Angle test, Pneumatic Adhesion test and Atomic Force Microscopy (AFM) test were performed, and the results obtained from each of these tests were compared to come to a reliable conclusion regarding effectiveness of the various tests for assessing the effect of prolonged heating on the adhesive bond strength. Results obtained from the Tensile Strength Ratio test showed that, as the prolonged heating duration increased the adhesive strength between the asphalt and aggregate was reduced. These results suggest that the non-volatilized portion of the anti-strip additive that remained in the asphalt after prolonged heating increased the moisture sensitivity of the asphalt-aggregate mixture, increased to the point where the mixtures failed the limiting TSR value of 85% as followed by NCDOT specification. Following the Tensile Strength Ratio test, Contact Angle test and Pull-Off test were performed in anticipation of expecting similar results that were obtained for the Tensile Strength Ratio test. However, due to complex interactions of such parameters as mixing of the anti-strip additive in asphalt cement, cleaning up of the glass/quartz slides, various temperature conditions, etc., the results obtained were inconclusive. Atomic Force Microscopy test was also not observed to be a good test for determination of the adhesive strength between the asphalt-aggregate. Hence, based on the results obtained we recommend that the Contact Angle test, Pull-Off test and Atomic Force Microscopy test are not effective tests for determining adhesive strength of asphalt-aggregate with anti-strip additive. Hence, based on the research, TSR test seems to be the reliable test to determine the effect of prolonged heating on adhesive bond strength of asphalt-aggregate with anti-strip additive.
Date: 2008-10-16
Degree: MS
Discipline: Civil Engineering
URI: http://www.lib.ncsu.edu/resolver/1840.16/2214


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