Advanced Materials & Processes

JUN 2015

Covers developments in engineering materials selection, processing, fabrication, testing/characterization, materials engineering trends, and emerging technologies, industrial and consumer applications, as well as business and management trends

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A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U N E 2 0 1 5 2 3 STEEL REINFORCEMENT BAR: A TENSILE TESTING GUIDE Steel rebar is commonly used around the world to reinforce concrete. Understanding the basics of rebar tensile testing is critical to ensuring product quality. Jef Shafer, Instron, Grove City, Pa. S teel reinforcing bar, or rebar, is em- bedded in concrete to improve the overall strength of the surrounding concrete. Material product standards help guarantee that rebar produced through- out the world exhibits the same physical, chemical, and mechanical properties re- gardless of the source. Proper mechanical testing is necessary to determine if the re- bar meets its published specifications, en- suring product quality. Mechanical test- ing requirements for rebar can vary, but typically fall into these main categories: • Tensile • Bend • Compression • Fatigue Other related product testing, such as slip testing of mechanical splices (cou- plers), may also be required. This article primarily focuses on the common—yet sometimes challenging—tensile test. TENSILE TESTING AND STANDARDS At the global level, technical com- mittees governed by the International Organization for Standardization (ISO) develop product and testing standards for reinforcement bar products. In ad- dition to specifying properties such as minimum upper yield strength (Reh), Rm/Reh ratio, and elongation values for ribbed steel bar products, ISO prod- uct standards, such as ISO 6935-2, also specify how to measure tensile proper- ties. Unique testing requirements are included directly in the standard and additional reference is made to ISO 15630-1, which focuses specifically on test methods for similar products. ISO 15630-1 provides further references to the more general metals tensile testing standard, ISO 6892-1, where applicable. On a regional level, many countries also have local standards organizations that may have existed even before the global ISO committees were formed. They often maintain their own product and testing standards or can elect to adopt global ISO standards where ap- propriate. For example, in the U.S., ASTM has established product and testing standards for rebar. Product standards such as ASTM A615, A706, A955, and A996, provide minimum product specifi- cations and also include unique testing details for determining tensile proper- ties. Reference may also be made to ad- ditional testing requirements found in ASTM A370. This steel testing standard covers mechanical testing of steel prod- ucts. It then includes further reference to the primary metals tensile testing standard, ASTM E8. Regardless of the governing body, the information provided in most global and local standards is quite de- tailed and intended to help users un- derstand the following basic testing requirements: • Required equipment • Associated terminology and symbols • Specimen preparation TABLE 1—COMMON REBAR PRODUCT AND TESTING STANDARDS ISO ASTM Rebar product standard 6935-2 A615 Rebar testing standard 15630-1 A370 Metals tensile test standard 6892-1 E8 Uncoiled rebar with slight bends over length.

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