ASTM C78 and Making 4-Inch Beams a Reality
EBA Engineering, Inc. (EBA) owns and operates a nationally accredited materials testing laboratory in Laurel, Maryland. Recently, our main laboratory in Baltimore had the opportunity to participate in an American Society for Testing and Materials (ASTM) Inter-Laboratory Study (ILS) Program. The goal of the ILS Program is to enhance the quality of standard test methods by providing quality data required to develop precision statements.
Precision statements are incredibly important to materials testing professionals because we use them to evaluate multi-laboratory test results. For example, EBA’s engineering materials testing department is involved in projects where multiple laboratories provide testing services for quality assurance. If the labs have conflicting test results on similar materials, using precision statements is one way to resolve the conflicts.
EBA participated in ILS Study #1625, with a goal of refining the existing precision statement on ASTM C78, Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading). Refining this precision statement was necessary because, in 2015, ASTM C78 adopted the use of smaller, 4x4x14-inch beams for flexural strength testing. Until 2015, the standard size for beams was a bulky 6x6x21 inches. The current precision statement in ASTM C78 was developed based on the standard 6-inch beams.
In addition to the size limitation, the precision statement was also based on testing one concrete mix and using one type of testing equipment. Upon approval, the new precision statement will be based on different sized beams, multiple concrete mix designs, and different types of testing equipment, which will be much more representative.
EBA was eager to participate in this study because we know how important precision statements are to the materials testing industry. When we provide quality assurance on some of our airport projects, we let the contractors and their quality control managers know what type of equipment we use. Using the same type of equipment allows us to compare the results using the current ASTM C78 precision statement. Making a fair comparison between test results is important because these results are usually used as a basis for payment to the contractor. But a new precision statement generated using multiple types of equipment will eliminate the need to have similar testing equipment.
EBA’s laboratories also test approximately 300 to 400 standard-sized concrete beam samples from various airport and roadway projects in the Mid-Atlantic region every year. Most of these tests are conducted between June and September at the height of the paving season on most airport projects. The standard 6-inch beam weighs approximately 65 pounds depending on the concrete mix, whereas a 4-inch beam on average weighs a mere 21 pounds.
As you can imagine, many lab testing technicians would appreciate the widespread use of 4-inch beams. They are much easier to handle. They also pose a much lower risk of back injury, since they weigh much less than standard beams. Curing 200 standard sized beams in the lab occupies a lot of valuable space at a period when we are extremely busy. Field testing technicians would also appreciate making these specimens, since smaller beams require much less rodding. I am sure most field and lab technicians are looking forward to the day when stakeholders will allow the use of 4-inch beams on their projects.
ASTM standards are important because they supplement building codes, highway design standards, and many other areas of engineering and construction. These standards provide accepted, peer-reviewed, and industry-wide guidelines on material specifications and testing. As active and voting members of various ASTM committees, we appreciated this opportunity to go beyond reviewing technical papers and casting ballots to creating some of the data used in standards development.
Jason Kolenda is the Laboratory Manager for EBA Engineering, Inc. For all your materials testing needs, please contact him at 410.504.6125 or firstname.lastname@example.org.