HOLCIM

About the sulfate resistance of slag composites

In Europe it is generally accepted that more than 65 % of granulated blast-furnace slag (GBFS) in composite cements make them high sulfate resistant. Proven by numerous studies, this rule has been implemented into national standards, such as the German DIN 1045-2. Due to the mechanism of sulfate attack, the composition of both, Portland clinker and GBFS influence the sulfate resistance of their composites, apart from an adequate cement and concrete design. In this study, mortars containing GBFS of different composition and high C3 A Portland cement were lab-tested for sulfate resistance. The results illustrate the influence of the alumina content of the GBFS, coupled with its reactivity, on expansion under sulfate attack. A GBFS Sulfate Expansion Index (GSEI) is proposed for rough indication, if a GBFS of given quality would need special attention when used in high sulfate resistant cements. Furthermore it was shown, that Ca-sulfate additions are very effective to increase the sulfate resistance of medium to high alumina GBFS-Portland composites.

1 Background

When sulfates in dissolved form, such as sodium, potassium, magnesium or calcium sulfates from soil or groundwater, enter hardened concrete, they react with the hydrated cement paste. Attacking ­alkali sulfates react with portlandite to calcium sulfate and sodium hydroxide. In the presence of calcium aluminate, the calcium sulfate reacts to ettringite. This reaction is coupled with a volume increase and pressure buildup, which can result in concrete cracking. According to Kunther (2012), sulfate expansion occurs when first, the pore solution is supersaturated with respect to...

Related articles:

Issue 7-8/2015 WO?2015/085139?A1

Gypsum composite modifiers

(22) 05.12.2014 (43) 11.06.2015 (57) Anhydrite calcium sulfate whiskers are prepared by combining alpha calcium sulfate hemihydrate and water to form a slurry, autoclaving the slurry to form alpha...

more
Issue 06/2010

Use of steel slags in the cement industry

Reply to Yüksel, I., Özkan, Ö.: Physical and mechanical properties of composite cements. ZKG INTERNATIONAL 12/2009, pp. 54.

The article by Yüksel and Özkan postulates rates of replacement of clinker with granulated blast furnace slag (GBFS) and steel slag (specifically: LD slag) of 60 to 80??%. The authors’...

more
Issue 4/2017 WO 2017/017376 A1

Long-workability calcium aluminate cement with hardening ­promoted by a temperature increase, and related use

(22) 27.07.2016 (43) 02.02.2017 (57) The invention relates to a calcium aluminate cement containing a calcium aluminate with a first crystallized mineralogical phase of calcium dialuminate CA2,...

more
Issue 12/2017 UA115381 (C2)

Calcium sulfoaluminate composite binders

(22) 02.09.2014 (43) 25.10.2017 (57) The present invention relates to composite binders containing calcium sulfoaluminate cement and supplementary cementitious material, wherein a weight ratio of...

more
Issue 1-2/2019 US 2018/0312445 A1

Use of quarry fines and/or limestone powder to reduce clinker content of cementitious compositions

(22) 05.07.2018 (43) 01.11.2018 (57) Quarry fines and/or limestone powder are used to reduce clinker content in concrete, mortar and other cementitious compositions, typically in combination with one...

more