Portland Cement Association's proposal to permit the use of as much as 5 percent ground limestone in ASTM C 150 portland cements passed a full Committee C01 ballot late last year with more than 95 percent affirmative response. During its semi-annual meeting, the Committee reviewed and resolved negatives that had not been withdrawn prior to the meeting.

The approval sets the table for the ground limestone provision to be formally incorporated in the C 150 standard during Committee C01's next meeting in April. The use of ground limestone in finished cement is a key component of PCA members' commitment to reduce greenhouse gas emission intensity levels 10 percent by the year 2020, and brings U.S. standards into harmony with those of Europe and Canada. This most recent proposal followed nearly 15 years of Committee C01 ballot measures and lobbying by PCA to allow the C 150 change.