Expansion and microstructural development in over-sulfated systems

Authors: H.A. Elaqra, K. Scrivener
Paper category: conference
Book title: Concrete Durability and Service Life Planning – ConcreteLife’09
Editor(s): K. Kovler
Print ISBN: 978-2-35158-074-5
e-ISBN: 978-2-35158-085-1
Publisher: RILEM Publications SARL
Publication year: 2009
Pages: 556 – 561
Total Pages: 6
Language: English

Abstract: It is well known that excessive additions of sulfate to Portland cement lead to expansion and similar unstable expansions can be observed in ternary blends of Portland cement, calcium aluminate cement and calcium sulfate. So far the associated expansion mechanisms are not well understood, with two main proposed theories: swelling and crystal growth pressure associated with ettringite formation.
The aim of the present study was to investigate of the relation between microstructure and expansion in the binary systems (Portland cement-calcium sulfate).
Ordinary Portland cement (OPC) was mixed with increasing amounts of gypsum (1, 3, 5, 7 and 9%) and cast into specimens of 10x10x40 mm3 which were de-moulded after 6h, 8h, 10h, 24h, 48h and 72h and stored in water or under 100% relative humidity.
The length variation were monitored as a function of time and related to the phase assemblages measured by XRD and SEM.
These investigations indicate that the direct implication of ettringite on expansion is far from clear.

Online publication: 2012-05-16
Publication Type: full_text
Public price (Euros): 0.00