Aggregate and Petrographic Laboratory

Purpose: The Aggregate and Petrographic Laboratory (APL) at the Turner-Fairbank Highway Research Center (TFHRC) provides facilities for the evaluation, preparation, and testing of aggregate sources, products, and samples for use in concrete, asphalt mixtures, and granular base course applications. Staffed by an experienced geologist and petrographer, the APL is able to assist in forensic evaluations of construction materials for others within Federal Highway Administration (FHWA) and with State departments of transportation (DOTs).

Laboratory Description: Facilities are available for characterizing highway materials using mechanical and durability tests, identification and quality testing of mineral aggregates, and troubleshooting of inferior quality materials or distress in concrete using forensic petrography. The Petrography Laboratory includes state-of-the-art transmitted and reflected light compound and reflected light microscopes and image-capturing tools, along with air-void parameter assessment using American Society for Testing and Materials (ASTM) C 457 for hardened air-entrained concrete. When necessary, the APL collaborates with the Chemistry Laboratory, which is equipped with wet, analytical, and spectroscopic chemical methods. Included in the Chemistry Laboratory are an Analytical/Spectroscopy Laboratory, a Materials Characterization Laboratory, and modern x-ray diffraction (XRD) and scanning electron microscopy (SEM) tools, along with laboratories for conducting bench scale research.

Laboratory Capabilities: The APL Laboratory is capable of aggregate preparation and sizing, mechanical and durability testing, and characterization  and classification  of aggregate types for use in concrete, asphalt, and granular base courses and drainage layers. The APL has tools to help troubleshoot performance problems and investigate  degradation and distress mechanisms  in concrete and other materials used in the transportation infrastructure,  working in conjunction with the Chemistry, Concrete, and Asphalt laboratories at TFHRC.

Laboratory Equipment:  includes: state-of-the-art transmitted and reflected light compound optical microscope and stereomicroscope; Rapid-Air 457 Air-Void Analyzer; state-of-the-art thin section making equipment; mineral aggregate crusher, grinder and pulverizer; sieving and washing equipment; and full sets of certified standard and intermediate-size sieves for coarse and fine aggregates and for the sizing of minus No. 200 microfine materials using sieves, hydrometer, and laser analysis. Various methods of shape, angularity, and texture analysis are available, including the AIMS II device as well as American Association of State Highway and Transportation Officials (AASHTO) Superpave methods. Durability and compaction equipment include the Micro-Deval device for fine and coarse aggregate degradation in wet exposures and standard and modified proctor testing and permeability equipment. Cutting, lapping, and polishing equipment for preparation of thin sections and lapped and polished sections for analysis of aggregates and materials containing aggregates are available in the materials preparation labs.

Laboratory Services: Testing, characterizing, and preparing aggregate materials for evaluation in concrete, asphalt, and granular base course mixtures as well as troubleshooting and forensic investigation of performance in pavement and structures applications. Assistance can be provided to FHWA divisions, Federal Lands engineers, and to State DOTs in evaluating special materials or materials performance.