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A new admixture for concrete with clay contaminated sand

Author(s): O. Mazanec, F. Morati, A. Große-Sommer
Paper category: Proceedings
Book title: Proceedings of the International Conference on Sustainable Materials, Systems and Structures (SMSS2019) New Generation of Construction Materials
Editor(s): Marijana Serdar, Nina Štirmer, John Provis
ISBN: 978-2-35158-217-6,
Vol 1. ISBN: 978-2-35158-223-7
e-ISBN: 978-2-35158-218-3
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 350-350
Total Pages: 1
Language : English

Abstract: Our daily lives are built on sand. A report by the United Nations Environment Programme (UNEP) found that no solid raw material is used more than sand and gravel. But these fine grains are in short supply. This is primarily due to the construction boom. In 2014, the UNEP estimated that between 26 and 30 billion metric tons of sand are poured into concrete mixers every year worldwide. Since then, these numbers will have only increased. The demand for this raw material in expanding metropolises, such as Singapore, Shanghai, Paris, or Dubai, is always growing. Mega construction projects in these cities are already devouring vast quantities of sand, as we see with the major public transfer projects in Paris.
This shortage has made sand a scientific priority. We are now looking for ways to make better use of the resources. One of these methods has been in use since 2016: a process developed by BASF to convert sand that was previously unsuitable for high-quality concrete into a valuable raw material. This involves using clayey sand or sand with a high proportion of ultra-fine
additives, such as mica. Clay and mica absorb large amounts of water due to their large surface area and their special, partially expandable structure – they also absorb the commonly used polycarboxylate superplasticizer (PCE) needed for concrete mixing by superficial adsorption via electrostatic interactions between the anionic groups and positively charged sites by adsorbed Ca2+ cations or the intercalation of ether units of the PCE grafts in the interlayer space of the alumosilicate layers. This has unwanted consequences: concrete cannot be processed.
A clay blocking superplasticizer has been synthesized to increase the performance in in concrete with challenging sands. It ensures that water and PCE superplasticizer are not absorbed by the sand, and instead the concrete is generously liquefied. The use of the clay blocking superplasticizer as counter measure will be discussed, including underlying mechanistical principles and sustainable aspects. Sands that were previously unsuitable can now be used and existing deposits can be exploited more intensively.

Online publication : 2019
Publication type : full_text
Public price (Euros) : 0.00

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