International Concrete Abstracts Portal

For the Ready Mix Concrete mix design, the initial workability depends on the chemical composition of the Polycarboxylate Ether (PCE). Up to now the use of best PCE can achieve 2 hours of slump retention. However, a tendency to segregate is observed when over-dosage is made, due to water reduction capability of PCEs. An approach is to use also a combination of a water-reducing agent and a retarding agent which has the main disadvantage to delay the setting time and consequently the early strength of the concrete. This paper demonstrates the possibility to boost the performance of currently used PCEs. The new slump retention additive that we developed allows a significant increase of the slump retention while maintaining the initial fluidity without impacting the water reduction ability. The homogeneity of the concrete is also controlled by using this additive. On top of that, the combination between this new product and a standard water-reducting PCE is made at commonly used dosage.

Polycondensates and polycarboxylates are known to be effective superplasticizers. Here, the synthesis of a novel, brown coal based superplasticizer by grafting acrylic acid (AA) and 2-acrylamido-2-tert.butyl sulfonic acid (ATBS) onto the alkali soluble components of brown coal (lignite) as backbone using free radical copolymerization technique is described. Furthermore, an ATBS-acrylic acid copolymer was synthesized to investigate the influence of the graft chains on the performance of the lignite copolymer. Successful grafting was confirmed by size exclusion chromatography (SEC) and comparison of the adsorbed layer thicknesses of the brown coal substrate and the grafted product. The dispersing performance of the graft copolymer was probed via mini slump tests and compared with that of BNS. Additionally, slump flow retention and sulfate tolerance were determined. It was found that the graft copolymer possesses higher dispersion effectiveness than BNS and exhibits high sulfate tolerance.

Editors: V. Mohan Malhotra, Pawan R. Gupta, Terence C. Holland

In May 1978, the Canada Center 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 symposium 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 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 admixtures since the last conference in 1998. Proceedings of the conference were published as ACI SP-148.

In October 1997, the Committee for the Organization of CANMET/ACI International Conferences (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. Proceedings of the conference were published as ACI SP-173.

In October 2000, the Committee of 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 eight conference 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 the world over 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. The proceedings were published by ACI as SP-302. Also, additional papers were presented at the conference that were published in the Supplementary Papers Volume.

Thanks are extended to members of the Technical Paper Review Panel that met in the Bahamas from October 3 to 11, 2014. Without their dedicated effort and hard work, it would not have been possible to publish the proceedings. Cooperation of the authors in accepting the reviewers’ suggestions and in revising the manuscripts accordingly is appreciated greatly. The help and assistance of Dr. Pawan R. Gupta and Prabha Gupta are acknowledged gratefully in the administrative work associated with the conference and processing of the manuscripts for both the conference proceedings (ACI SP-302) and the Supplementary Papers Volume.

Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-302

The impact of clinker grinding aids (GAs) based on amine, glycol, or phenol on static yield stress (t0) of cement pastes is not well understood. Results obtained from this project have shown that GA molecules remain active after the grinding process and provide variations in cement properties, whether in the fresh or hardened states. Flowability improved and t0 decreased when the cement is ground using increased GA concentrations. This was attributed to the adsorption of these molecules onto the cement grains and saturation of surface charges, thus creating repulsive forces between neighboring particles. The decrease in t0 was particularly pronounced when phenol-based GA was used, given the presence of polycarboxylate polymers that help dispersing cement particles upon mixing with water.

The microstructure of MPEG-type polycarboxylate (PCE) copolymers, i.e. the distribution of side chains along the main chain was investigated via 13C NMR spectroscopy and the effect on the interaction with cement was determined. For this purpose, two series of polycarboxylate samples (one series synthesized by radical copolymerization, the other one via grafting/esterification) at molar ratios of –COO– to side chain of 2 to 10 were compared. The 13C NMR spectra suggest that the copolymerized PCEs possess a gradient-like distribution of side chains along the main chain while the grafted PCEs exhibit a statistical (random) repartition. Owed to those microstructural differences the grafted PCE copolymers show a tendency to adsorb in lower amount on cement. The reason is that in the copolymerized PCEs, large blocks of –COO– groups are present which exhibit high affinity to the surface of cement and therefore promote adsorption.