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International Concrete Abstracts Portal

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-329-34

Date: 

September 26, 2018

Author(s):

Wolfram Schmidt, Sarah Leinitz, Berta Mota, and Claudia Crasselt

Publication:

Symposium Papers

Volume:

329

Abstract:

The paper presents rheometric results and hydration curves for cementitious systems based on cement mixed with different aqueous phases at solid volume fraction of ϕ = 0.45. The varied aqueous phases were deionized water, limewater, the filter residue of a cement paste mixed at w/c = 2.0, and the filtrate of cement paste at solid volume fraction of 0.45. Each cementitious system provided different amounts and sizes of particles formed in the aqueous phase. The pastes were observed with and without polycarboxylate ether based superplasticizer. It was observed that the presence of particles causes higher PCE saturation dosages to achieve a minimum value, but the minimum value is only affected in the case of large particles. In all cases with and without PCE, the presence of small particles causes increased plastic viscosity. In addition, with decreased number and size of hydrates in the aqueous phase the hydration was retarded, which was specifically pronounced in the presence of PCE.

DOI:

10.14359/51711232


Document: 

SP-329-11

Date: 

September 26, 2018

Author(s):

Giorgio Ferrari, Mariele Gamba, Francesco Surico, Gilberto Artioli, Maria Chiara Dalconi, and Luca Valentini

Publication:

Symposium Papers

Volume:

329

Abstract:

Expandable clays are highly detrimental to PCEs because of the possibility to intercalate PCEs molecules into the clay interlayer. In this work, the interaction of PCEs with such type of clay was studied by XRPD and adsorption measurements and the effect of clay on the fluidity of cement pastes was measured by mini-slump test. Smectite clay has been mixed in synthetic cement pore solution with different PCEs based on methacrylic acid/MPEG methacrylate copolymers. Results confirmed that the presence of expandable clays reduces the cement paste fluidity because of the possibility to intercalate PCE molecules and the formation of hydrogel between PCE and clay. It was found that the sensitivity to expandable clay depends on the PCE molecular weight and the shift in the position of the 001 diffraction peak of the clay, which is a direct measurement of the tendency of different PCEs molecules to intercalate into swelling clays.

DOI:

10.14359/51711209


Document: 

SP-329-20

Date: 

September 26, 2018

Author(s):

P. Gronchi, S. Bianchi, L. Brambilla, and M. Goisis

Publication:

Symposium Papers

Volume:

329

Abstract:

Graphene, graphite nanoplatelets and graphene oxide are emerging nanomaterials for future technologies. Despite the conservative nature of the building industry, nanomaterials are already making their way into some construction applications and nanotechnologies have the potential to open a new season in this field. Recent studies reported mechanical improvements in cement-graphene oxide composites. The interaction between the carbon nanoadditives and C-S-H is not clear yet. In this paper, we investigate whether and how graphite nanoplatelets and graphene oxide affect morphology and kinetics of C-S-H formation, studying the simple reaction between calcium oxide and silica. Influence on hydration by two different types of silica having different specific surfaces was considered. Instrumental analyses of the products were performed through Infrared and Raman spectroscopy, TG and SEM analysis up to four weeks. Results indicate that GO interacts with C-S-H phase and hinders its formation while GNPs remain only dispersed in the matrix.

DOI:

10.14359/51711218


Document: 

SP-329-19

Date: 

September 26, 2018

Author(s):

Angela Rozzoni and Michael Dolci

Publication:

Symposium Papers

Volume:

329

Abstract:

Admixtures for concrete offer a wide range of water reducers that are mostly based on polycarboxylate polymers (PCE) bearing polyethylene oxide nonionic side chains. It is possible to increase PCE effectiveness mixing them with a special workability retention agent (WRA). We focused on ester-based PCE, synthesized from methoxypolyethylene glycol (Mpeg) and acrylic or methacrylic acid, and allylic-type PCE, synthesized from TPeg (polyethyleneglycol isopentenyl ether) or Ipeg (polyethylenglycol methallyl ether) and acrylic or methacrylic acid. By modifyng the composition of the backbone, the kind of repeating units and the molecular weight of polyethylene oxide side chains of PCE it is possible to optimize the properties of the mixture of PCE and WRA. The structures of the most interesting polymers we prepared are described in terms of their conformations (worms or stars). WRA is a particular acrylic polymer that can hydrolyze in alkaline environment; to work properly it must have a certain molecular weight and a low polydispersibility index. If it is used alone it is an ineffective water reducer. To investigate the reason behind this behavior slump test and rheological measured were carried out on mortar.

DOI:

10.14359/51711217


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