Texas A&M Transportation Institute

FHWA/TX-15/0-6686-2

Tech Report

Texas

Texas A&M Transportation Institute

Limestone Rock Asphalt (LRA) mixtures have been produced and placed for several decades using

specification requirements currently listed under DMS 9210. Several districts have had placement issues

and premature failures at the beginning of 2010. These issues and failures have been attributed to material

properties. Requirements for DMS 9210 have not changed for several years and need to be evaluated to

possibly produce a higher quality material to reduce the occurrence of premature failures and to minimize

placement issues. The objectives of the study are to (1) evaluate specification requirements of Item 330 and

DMS 9210, (2) conduct field evaluations and lab testing to determine workability and acceptability as

stockpile material for use as needed in pavement maintenance, and (3) consider improvements to the

specification requirements to ensure an acceptable and workable stockpile material for up to 6 months.

The Hveem stability was determined to be a good indicator of rutting resistance of LRA but it does not

indicate when a mix is too dry and susceptible to raveling. The Cantabro test was able to identify dry

mixtures with insufficient flux oil as well as poor quality flux oil.

A Cantabro loss of 15 percent maximum is being proposed as a new specification test and limit

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Project 0-6686

US Transportation Collection