The Federal Highway Administration (FHWA) released an updated publication, Petrographic Methods of Examining Hardened Concrete: A Petrographic Manual
The Federal Highway Administration (FHWA) released an updated publication, Petrographic Methods of Examining Hardened Concrete: A Petrographic Manual (Pub. No. FHWA-HRT-04-150), which offers guidance on using hydraulic cement concrete (HCC) petrography. In assessing deterioration, distress, and failure, petrographic analysis uses microscopic techniques to examine concrete condition and quality. Accordingly, the manual includes procedures, instructions and photographs to assist transportation practitioners who lack formal petrographic training.
Leading the effort to update the original publication Û developed in 1992 by Virginia Transportation Research Council (VTRC) petrographer Hollis N. Walker Û was D. Stephen Lane, VTRC senior research scientist. Recent technical advances and field work are reflected in additional chapters addressing (1) use of the scanning electron microscope to examine concrete and concrete-making materials; (2) identification and classification of rocks and minerals in aggregates; and, (3) alkali-aggregate reactions, including an outline of the process used to investigate concrete deterioration with illustration of features indicative of alkali-silica or alkali-carbonate reactions. The updated manual’s new chapter on alkali-aggregate reactions especially will serve as a tool for FHWA’s alkali-silica reactivity (ASR) program, which aims to prevent and mitigate ASR in concrete pavements and structures.
The Petrographic Manual will help achieve one of the objectives in the inventory of structures affected by ASR by confirming that the deterioration mechanism is actually ASR and not some other type. It will help also in recognizing situations where other deterioration mechanisms may be occurring in conjunction with ASR, says Richard Meininger of FHWA’s Office of Infrastructure Research and Development. In some cases, the question may be asked: ÎWhich deterioration occurred first, and was it a causal factor in subsequent deterioration?Ì
The manual’s targeted audience includes petrographers, geologists, engineers, chemists, consultants, and university researchers engaged in forensic work and troubleshooting related to concrete deterioration, plus rock and mineral identification. Currently, many practitioners performing concrete petrography are formally trained geologists whose HCC evaluations are often more qualitative than quantitative. Thus, training new practitioners who lack field experience in examining HCC can be difficult. The updated manual has been compiled to close that gap.
Petrographic Methods of Examining Hardened Concrete: A Petrographic Manual (Pub. No. FHWA-HRT-04-150) is available online at www.fhwa.dot.gov/pavement/peep/pubs/04150. More information can be obtained by contacting FHWA’s Richard Meininger, 202/493-3191; e-mail: [email protected].