Date of Award

Spring 1994

Project Type

Dissertation

Program or Major

Engineering

Degree Name

Doctor of Philosophy

First Advisor

David Gress

Abstract

A research project was conducted to investigate the potentials of using municipal solid waste combustion bottom ash as a paving material. The effort focused on (i) characterization of the time-dependent properties of the bottom ash, (ii) bottom ash utilization as an unbound material in road subbase and base application, and (iii) bottom ash utilization as an aggregate substitution in hot mixture asphalt. A series of standard or non-standard procedures were employed to evaluate bottom ash behavior.

Results indicate that variability of the physical properties of the bottom ash produced during the two years study period is relatively small in view of the fact that the bottom ash is a uncontrolled waste material. In comparison to conventional aggregates bottom ash shows more variation. The bottom ash is a heterogeneous, well graded, highly absorptive, porous and lightweight aggregate material. The abrasion resistance and durability of the bottom ash as measured by the Los Angeles abrasion and sodium sulfate soundness tests pass ASTM requirements. The California Bearing Ratio tests show that the bottom ash has an excellent bearing capacity and would make an excellent subbase and base material in road application.

Gyratory Testing Machine (GTM) and Marshall mix design methods were employed to study the properties of hot mix asphalt. Results show that the bottom ash can be used as an aggregate substitute in hot mix asphalt. Results also indicate that GTM and Marshall methods do not make much difference in developing the optimum mix design for the conventional aggregate mix. However, they make a significant difference for the bottom ash mix. The GTM method results in much lower optimum asphalt content than the Marshall method for the bottom ash mix. GTM, unlike Marshall, is a unique tool in predicting the mix performance. It is anticipated that the bottom ash mix developed with the GTM method will perform much better than a mix developed with the Marshall method.

A bottom ash test road at 50% substitution designed with the GTM method was successfully installed in Laconia, NH in May of 1993. The long term performance of the test road is being evaluated with various destructive and nondestructive testing techniques.

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