By Mark S. Kuhar
A proposed new ASTM International standard will cover the process, verification and record keeping procedures for recycling returned fresh concrete. The proposed standard, ASTM WK39876, Specification for Returned Fresh Concrete for Use in a New Batch of Ready-Mixed Concrete, is being developed by Subcommittee C09.40 on Ready-Mixed Concrete, part of ASTM International Committee C09 on Concrete and Concrete Aggregates.
A significant amount of concrete is returned to manufacturing plants, which can result in wasted material, the need for disposal and unnecessary environmental impact. These issues can, however, be minimized since some of the returned concrete is suitable for reuse and can be incorporated into new batches. A proposed ASTM International standard will ensure that returned fresh concrete mixed with new concrete has known and verifiable characteristics.
“Concrete is the most widely used building material in the world,” said Eric Koehler, vice president, Verifi LLC, and chairman of the task group developing ASTM WK39876. “The proposed standard will help ready mixed concrete manufacturers reduce waste material and disposal requirements. Purchasers and specifiers of concrete can obtain concrete with greater recycled content while ensuring the concrete is of high quality.”
Koehler notes that technology available to facilitate the reuse of returned fresh concrete includes hydration stabilizing admixtures that can be used to extend the setting time of concrete and ensure that concrete can be used in a new batch. In addition, truck-mounted equipment can be used to measure, manage and record concrete slump, water content, temperature and load size throughout the delivery cycle to reduce the need for manual testing.
Subcommittee C09.40 welcomes all interested parties, particularly those with experience in using returned fresh concrete, to contribute to the ongoing development of ASTM WK39876.
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