Leaching from granular waste materials used in highway infrastructures during infiltration coupled with freezing and thawing

Collaborators

Kate Langley, Graduate Student of Civil and Environmental Engineering
Florence Sanchez, Assistant Professor of Civil and Environmental Engineering
Malcom E. Baird, Research Professor of Civil and Environmental Engineering
Rossane Delapp, Research Engineer of Civil and Environmental Engineering

Funding

Recycled Materials Resource center (RMRC)

Abstract

The overall objective of the proposed research project is to investigate the effect of freezing and thawing processes on constituent leaching from granular waste materials used in highway construction applications. The durability of aggregate materials or their resistance to the forces of weathering is one of the most important considerations in the selection of a material for highway construction. One of the primary exposures of concern is alternate freezing and thawing.


Current test methods for evaluating the soundness of aggregates due to freezing and thawing (AASHTO T 103 and brine freeze-thaw ITM 209) are only based upon meeting physical test criteria and do not integrate environmental material performance. However, during the design life of the construction application, materials are exposed to freezing and thawing coupled with intermittent infiltration/wetting as a consequence of precipitation events. In such a scenario, leaching of material constituents is a primary pathway for environmental impact. The effect of freezing and thawing processes may be significant enough to impact the environmental acceptability of a proposed application. The specific objectives of the proposed research are therefore to:

• Determine the effect of material moisture content at the time of freezing on constituent release during percolation flow controlled scenarios and on material integrity (i.e., change in particle size distribution);


• Examine the effect of the number of freeze/thaw cycles on constituent release during percolation flow controlled scenarios and on material integrity;


• Examine the interaction between material integrity and environmental performance;


• Determine the critical parameters that control mass transfer of constituents to the environment during wetting coupled with freezing and thawing; and,


• Develop guidelines for test methods and accelerated aging procedures that can be used by end-users to assess the potential impact of freezing and thawing processes on constituent leaching during percolation flow controlled scenarios.