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Effect of sodium hexametaphosphate and trisodium phosphate on dispersion of polycarboxylate superplasticizer

Tan, H; Zou, F; Ma, B; Bai, Y; (2016) Effect of sodium hexametaphosphate and trisodium phosphate on dispersion of polycarboxylate superplasticizer. In: Proceedings of the 36th Cement and Concrete Science Conference. : Cardif. Green open access

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Abstract

The high fluidity cement-based material has been widely used in indoor floor, grout, pumping concrete and self-compacting concrete. Efficiently dispersing the cement grains is essential for the practical application of this kind of material. Generally, the retarder can enhance the initial dispersion of PCE system because of the reduced consumption of superplasticizer and free water as well as the delayed formation of the hydration products at the very beginning of hydration. Both sodium hexametaphosphate (SHMP) and trisodium phosphate (TSP) are commonly used retarders. However, SHMP can enhance the initial dispersion of PCE while TSP cannot; this phenomenon cannot be simply explained from the retarding effect. It is proposed in this paper that the different behavior of SHMP and TSP could be related to the water/solid interface performance. The adsorption behavior was analyzed with TOC, ICP and XPS. The adsorption model was then proposed to explain the mechanism. The results show that TSP can reduce the initial dispersing ability of PCE while SHMP can enhance it. Both TSP and SHMP can reduce the adsorption capacity of PCE, but increase the thickness of adsorption layer. This phenomenon indicates that phosphates, which can be quickly precipitated and partly cover the PCE layer, may increase the ineffective adsorption to reduce the initial dispersing ability of the PCE system; on the contrary, for those phosphates, which can be combined with Ca2+ and preferentially adsorb onto the surface of cement grains, can avoid the ineffective adsorption to enhance the initial dispersing ability of the PCE system. The results suggest that the dispersing ability of PCE-retarder system is not completely dependent on the total adsorption amount of PCE or the thickness of adsorption layer, but mainly depends on the effective adsorption amount.

Type: Proceedings paper
Title: Effect of sodium hexametaphosphate and trisodium phosphate on dispersion of polycarboxylate superplasticizer
Event: 36th Cement and Concrete Science Conference
Location: Cardiff, UK
Dates: 05 September 2016 - 06 September 2016
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng
URI: https://discovery.ucl.ac.uk/id/eprint/1523332
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