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The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

Showing 1-5 of 37 Abstracts search results

Document: 

SP329

Date: 

October 2, 2018

Author(s):

Jiaping Liu, Ziming Wang, Terence C. Holland, Jing Huang, Johann Plank

Publication:

Symposium Papers

Volume:

329

Abstract:

On 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. The organizers of the conference were the Chinese Ceramic Society, Beijing and the Committee for the Organization of International Conferences (formerly CANMET/ACI Conferences).

DOI:

10.14359/51712247

Document: 

SP-329-28

Date: 

September 26, 2018

Author(s):

Nanxiao Gao, Qianping Ran, and Min Qiao

Publication:

Symposium Papers

Volume:

329

Abstract:

The shrinkage of concrete can adversely affect not only its fitness for use, but also the durability of concrete structural elements. Compared with traditional PCEs, shrinkage-reducing polycarboxylate superplasticizer (SR-PCE) can decrease the concrete shrinkage. Therefore, it’s a new way to increase the durability of concrete in recent years. In this paper, three novel SR-PCEs were designed and synthesized by the free radical copolymerization of acrylic acid and the macromonomers with hydrophobic poly(ethylene oxide and/orpropylene oxide)-based side chains.The effect of the side chain hydrophobicity on drying shrinkage and dispersion performance for concrete was investigated, and the relationship between side chainhydrophobicity, drying shrinkage and pore solution properties (surface tension and alkali ions concentration)was also studied. Based on these investigations, a new kind of SR-PCE was developed (SR-PCE3). Upon the addition of 0.4% SR-PCE3, the water-reducing rate was about 21.4% and the drying shrinkage of concrete was decreased by 24.0% at 60 days. Introducing hydrophobic group as the side chain into the polymer may be an effective way to change the properties of pore solution significantly with low concentration of SR-PCE and thus solve the contradiction between adsorption dispersing and shrinkage reducing.

DOI:

10.14359/51711226

Document: 

SP-329-25

Date: 

September 26, 2018

Author(s):

Yanwei Wang, Xin Shu, Yong Yang, Qianping Ran, and Jiaping Liu

Publication:

Symposium Papers

Volume:

329

Abstract:

Conformational properties of comb-shaped copolymer polyelectrolytes such as polycarboxylate ether-based superplasticizers (PCEs) in aqueous solutions and at liquid/solid interfaces are fundamental to their performances as polymeric dispersants. Pioneering studies of Flatt and coworkers have demonstrated the great relevance of polymer theory to the PCE community. The present work revisits this topic with an emphasis on the semi-flexible characteristics of the anionic backbone decorated with flexible side chains. A simple physical picture, where the backbone adopts a "train-like" conformation on the surface, effectively as a two-dimensional worm-like chain, with the side chains mimicking surface-tethered chains, is presented for PCEs in the strongly adsorbed state.

DOI:

10.14359/51711223

Document: 

SP-329-26

Date: 

September 26, 2018

Author(s):

Hongxia Zhao, Yanwei Wang, Yong Yang, Xin Shu, Jiaping Liu, and Qianping Ran

Publication:

Symposium Papers

Volume:

329

Abstract:

Computational simulations have become a powerful tool to investigate the conformational properties of polycarboxylate superplasticizers in solution and at liquid-solid interfaces. Those properties are difficult to measure experimentally. Our group has recently carried out some studies on conformation using the all-atom model to explore the effects of counter-ion species and concentration, solution pH, content of methyl groups, and hydrophobic modifications on polymer properties. Such studies were driven by the experimental work carried out in our group during the course of product development, and have in return provided useful information for an improved understanding of experimental phenomena. In this work, we discuss the conformation properties of superplasticizers performed by all-atom molecular dynamics simulations and the correlation of the microscopic conformation with the experimental phenomena.

DOI:

10.14359/51711224

Document: 

SP-329-27

Date: 

September 26, 2018

Author(s):

Xin Shu, Yanwei Wang, Yong Yang, Xiumei Wang, Qian Zhang, Hongxia Zhao, Qianping Ran, and Jiaping Liu

Publication:

Symposium Papers

Volume:

329

Abstract:

Rheological properties of cement pastes with polycarboxylate superplasticizers (PCE) containing different hydrophobic groups (styrene, n-butyl acrylate units) at different water to cement ratios (w/c) were investigated. Further investigation on the solution behavior (hydrodynamic radius, solution viscosity) and adsorption behavior revealed the fundamental difference of these PCE samples. At high w/c, the rheological properties of cement pastes primarily depended on the ALT and the differences at constant flow diameter were small. At low w/c, the yield stress primarily depended on the ALT, while the apparent viscosity difference relied on the balance of ALT and solution viscosity. The styrene unit enhanced the backbone stiffness and therefore the adsorption affinity, intrinsic viscosity, yet smaller ALT, therefore reduced the apparent viscosity at a proper dosage. The n-butyl acrylate unit always increased the apparent viscosity of cement pastes.

DOI:

10.14359/51711225

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