The American Concrete Institute (ACI, formerly National Association of Cement Users or NACU) is a non-profit technical society and standards developing organization.

An editorial by Charles C. Brown in the September 1904 issue of Municipal Engineering discussed the idea of forming an organization to bring order and standard practices to the industry.

[4] In 1905 the National Association of Cement Users was formally organized and adopted a constitution and bylaws.

The first committees were appointed at the 1905 convention in Indianapolis and offered preliminary reports on a number of subject areas.

Clerical and editorial help was brought on to more effectively organize conventions and publish proceedings of the institute.