Source: National Ready Mixed Concrete Association, Silver Spring, Md.
ASTM Subcommittee C09.40 on Ready Mixed Concrete has approved a revision to C94 Standard Specification for Ready Mixed permitting limited addition of water to a concrete load en route to a job site. It recognizes equipment that gauges the slump of material within a mixer drum, and adds water needed to meet a pour’s workability target.
Also on the heels of ASTM C09 Committee on Concrete and Concrete Aggregates meetings earlier this month, a new C94 section defines requirements for verifying batch plant scale accuracy—a revision consistent with the process described in the NRMCA plant certification program. A proposed revision to eliminate the 300 drum revolution limit on truck mixed concrete was successful in passing the subcommittee resolution process, but held back from the main C09 committee. Previous ballot comments have been accommodated and the revision will be proposed for a new letter ballot.
Items in line for future C94 revisions, NRMCA reports, include air content table changes; batching concrete section revisions; clarifying requirements for ordering lightweight mixes; addressing reuse of fresh returned concrete (more likely as a separate standard); and, revisions to methods used for chemical analysis of non-potable mixing water.