Preface In May 1978@ the Canada Centre for Mineral and Energy Technology (CANMET)@ in association with the American Concrete Institute (ACI) sponsored a three-day conference in Ottawa@ ON@ Canada on the use of superplasticizers in concrete. Selected papers from the conference were published as ACI SP-62. In 1981@ CANMET again in association with the ACI@ sponsored a second three-day International conference in Ottawa on the use of the superplasticizers in concrete. Proceedings of the conference were published as ACI SP-68. The purpose of the third international conference in Ottawa in 1989 was to review the progress made since the meetings in 1978 and 1981@ and to bring together representatives of the chemical admixtures@ cement@ and concrete industries to exchange information and delineate new areas of needed research. The scope of this conference was expanded to include chemical admixtures other than superplasticizers. Proceedings of the conference were published as ACI SP-119. In October 1994@ CANMET in association with the ACI and several other organizations sponsored the fourth conference in Montreal@ QC. Canada. The objective of this conference was to bring attention to new developments in chemical admixture since the last conference in 1989. Proceedings of the conference were published as ACI SP-148. In October 1997@ the Committee for the Organization of CANMET/ACI International Conference@ (ACI Council)@ in association with the ACI and several cement and concrete organizations in Italy@ sponsored the fifth conference in Rome@ Italy. The conference was aimed at transferring technology in the fast -moving field of chemical admixtures. The proceedings of the conference were published as ACI SP-173. In October 2000. Committee for the Organization of CANMET/ACI International Conferences@ (ACI Council)@ in association with several organizations in Canada and France@ sponsored the sixth conference in Nice@ France. More than 50 papers from more than 20 countries were received and reviewed by the ACI review panel@ and 37 were accepted for publication in the proceedings of the conference. The proceedings were published as ACI SP-195 In October 2003@ The Committee for the Organization of CANMET/ACI International Conferences (ACI Council) in association with several organizations in Canada and Germany@ sponsored the seventh conference in Berlin@ Germany. The conference attracted more than 275 delegates and proceedings of the conference consisting of 39 papers@ were published as ACI SP-217. In October 2006@ the Committee for the Organization of CANMET/ACI International Conferences@ (ACI) Council)@ sponsored the eighth conferences in Sorrento@ Italy. More than 60 papers from more than 25 countries were received@ and peer reviewed by the CANMET/ACI review panel in Budapest@ and 36 were accepted for publication as ACI SP-239. In October 2009@ the Committee for the Organization of International Conferences (COIC) (formerly CANMET/ACI International Conferences) sponsored the ninth ACI International Conference in Seville@ Spain. More than 50 papers from more than 20 countries were received and peer reviewed@ and 35 were accepted for publication in the proceedings of the conference. The proceedings were published as ACI SP-262. In October 28 to 31 2012@ COIC sponsored the Tenth International Conference on Superplasticizers and Other Chemical Admixtures in Concrete in Prague@ Czech Republic. More than 70 papers from all over the world were peer reviewed@ and 33 were accepted for publication in the proceedings of the conference. The proceedings were published as ACI SP-288. In July 10-13@ 2015@ the COIC in association with ACI sponsored the Eleventh International Conference on Superplasticizers and Other Chemical Admixtures in concrete in Ottawa@ Canada. More than 60 papers from the world over were peer reviewed@ and 28 were accepted for publication in the proceedings of the conference. Also@ additional papers were presented at the conference that were published in the Supplementary Papers Volume. In October 28-31@ 2018@ the Chinese Ceramic Society and the China Academy of Building Research (CABR)@ Beijing China@ in association with ACI@ sponsored the Twelfth International Conference on Superplasticizers and other Chemical Admixtures in Concrete in Beijing China. More than 80 papers from all over the world were received and peer reviewed. A total of 36 refereed papers were accepted for publication in the proceedings of the conference. The proceedings were published by the ACI as SP 329. Also@ 54 additional papers were presented at the conference@ and were published in the Supplementary Papers Volume.